Treatment of fish parasites: 5. The effects of sym. triazinone (Toltrazuril) on fish parasitic ciliophora (Ichthyophthirius multifiliis FOUQUET, 1876, Apiosoma amoebea GRENFELL, 1884, Trichodina sp. EHRENBERG, 1831)

For chemotherapy of fish parasitized by different Ciliophora (Protozoa) toltrazuril was tested in vivo and in vitro against skin and gill parasitizing species (e.g. Ichthyophthirius multifiliis, Apiosoma amoebea and Trichodina sp.). For in vitro treatment naturally infected fish were incubated at 20 °C for 0.3,1,2,4.5 h in water containing 0,1,5,10,20 or 50 μg toltrazuril/ml. Lethal damages already occurred in about one third of the trophozoites of I. multifiliis after incubation in 5 μg/ml for 4.5 h, and in more than two thirds of the trophozoites after incubation in 10 μ/ml for 2 h. A few trophozoites, however, were still able to leave their hosts, to encyst and to produce theronts. However, when treatment was done by intermittent therapy (1×10 μg/ml for 2 h, first day; 1 × 20 μg/ml for 1 h, second day; 1 × 20 μg/ml for 1 h, third day) all the trophozoites were lethally damaged. The damages consisted in the destruction of the outer cell membranes, of the cilia, and of the mitochondria, as well as in the complete abolishment of the ribosomes and in the enlargement of the nuclear space. After in vitro treatment (10 μg/ml, 2 h) all the trophozoites were lethally damaged. In contrast to the trophozoites, the free-swimming theronts of I. multifiliis were not affected by the drug. In vivo treatment starting with 20 μg/ml for 1 h led to severe damages in A. amoebea, which were intensified after treatment with 50 μg/ml for 0.3 h. The specimens were heavily contracted, and the oral cilia were redrawn. Furthermore, the pellicular pores seen in the surface of controls were not detectable. Despite the affections caused by the treatment the parasites did not drop off their hosts. In vivo treatment against Trichodina sp. led to a reduced motility in these parasites starting with 10 μg/ml for 2 h. Incubation with 20 μg/ml for 1 h caused a complete stop of motion in most of the specimens. The highest dose (50 μg/ml; 0.3 h) only caused a dropping off in about one third of the specimens from their hosts. Treated specimens of Trichodina sp. had a more flattened appearance compared to untreated controls, and the epistomial disc was drastically enlarged. From these experiments it is suggested that treatment against the trophozoites of I. multifiliis should be done by intermittent therapy according to the following scheme: 1st day: 10 μg/ml, 2 h, 2nd day: 20 μg/ml, 1 h; 3rd day: 20 μg/ml, 1 h. In the cases of Apiosoma spp. and Trichodina spp. infected fish incubating with 50 μg/ml for only 20 minutes is recommended.

Comparative population dynamics of a generalist (Ixodes ricinus) and specialist tick (I. hexagonus) species from European hedgehogs

Although the population dynamics of the tick Ixodes ricinus are relatively well studied, those of other Western European tick species are largely unknown. Moreover, there is very little information related to the interactions between I. ricinus and other ticks. Such knowledge, however, is of special interest in respect to the epidemiology of tick-borne pathogens such as Borrelia spp. We compared the dynamics of the generalist I. ricinus with the nest-dwelling hedgehog specialist, I. hexagonus. Both species were collected from hedgehogs from a naturally infested experimental population between 2006 and 2008. Ticks were collected once a month from March to October from each hedgehog counted and the life history stage and species determined. All hedgehogs harboured both tick species. Nymphs, females and males of I. ricinus showed clear bimodal seasonal distributions with peaks in spring and autumn, while larvae peaked only in summer. The density of I. hexagonus life stages was low during the whole investigation period and seasonal fluctuations of population density were much weaker compared to I. ricinus. Nymphs and larvae showed comparatively little change in population size and no consistent period of peak density. Females showed a single peak in summer and males were found only occasionally on hedgehogs. We suggest density-dependent mechanisms regulating the population density of the specialist I. hexagonus but not of the generalist I. ricinus.

Acanthocephalus reunionensisn. sp. (Acanthocephala: Echinorhynchidae), a parasite ofAnguillaspecies (Anguillidae) from Reunion Island

In a survey of 118 eels Anguilla bicolor, A. marmorata and A. mossambica, (Anguillidae) indigenous to Reunion Island in the Mascarene island group, western Indian Ocean, a new species of acanthocephalan, Acanthocepholus reunionensis n. sp., was found. With a proboscis hook formula of 19 rows of 4-5 hooks, and elongated cement glands arranged in three pairs, this species differs from all other species in the genus. This is the first record of the genus Acanthocephalus occurring in eels from the African Region.

Hosts and parasites as aliens

Over the past decades, various free-living animals (hosts) and their parasites have invaded recipient areas in which they had not previously occurred, thus gaining the status of aliens or exotics. In general this happened to a low extent for hundreds of years. With variable frequency, invasions have been followed by the dispersal and establishment of non-indigenous species, whether host or parasite. In the literature thus far, colonizations by both hosts and parasites have not been treated and reviewed together, although both are usually interwoven in various ways. As to those factors permitting invasive success and colonization strength, various hypotheses have been put forward depending on the scientific background of respective authors and on the conspicuousness of certain invasions. Researchers who have tried to analyse characteristic developmental patterns, the speed of dispersal or the degree of genetic divergence in populations of alien species have come to different conclusions. Among parasitologists, the applied aspects of parasite invasions, such as the negative effects on economically important hosts, have long been at the centre of interest. In this contribution, invasions by hosts as well as parasites are considered comparatively, revealing many similarities and a few differences. Two helminths, the liver fluke,Fasciola hepatica,of cattle and sheep and the swimbladder nematode,Anguillicola crassus,of eels are shown to be useful as model parasites for the study of animal invasions and environmental global change. Introductions ofF. hepaticahave been associated with imports of cattle or other grazing animals. In various target areas, susceptible lymnaeid snails serving as intermediate hosts were either naturally present and/or were introduced from the donor continent of the parasite (Europe) and/or from other regions which were not within the original range of the parasite, partly reflecting progressive stages of a global biota change. In several introduced areas,F. hepaticaco-occurs with native or exotic populations of the congenericF. gigantica, with thus far unknown implications. Over the fluke's extended range, in addition to domestic stock animals, wild native or naturalized mammals can also serve as final hosts. Indigenous and displaced populations ofF. hepatica, however, have not yet been studied comparatively from an evolutionary perspective.A. crassus, from the Far East, has invaded three continents, without the previous naturalization of its natural hostAnguilla japonica, by switching to the respective indigenous eel species. Local entomostrac crustaceans serve as susceptible intermediate hosts. The novel final hosts turned out to be naive in respect to the introduced nematode with far reaching consequences for the parasite's morphology (size), abundance and pathogenicity. Comparative infection experiments with Japanese and European eels yielded many differences in the hosts' immune defence, mirroring coevolution versus an abrupt host switch associated with the introduction of the helminth. In other associations of native hosts and invasive parasites, the elevated pathogenicity of the parasite seems to result from other deficiencies such as a lack of anti-parasitic behaviour of the naïve host compared to the donor host which displays distinct behavioural patterns, keeping the abundance of the parasite low. From the small amount of available literature, it can be concluded that the adaptation of certain populations of the novel host to the alien parasite takes several decades to a century or more. Summarizing all we know about hosts and parasites as aliens, tentative patterns and principles can be figured out, but individual case studies teach us that generalizations should be avoided.

Occurrence of Anguillicola crassus (Nematoda: Dracunculoidea) in Japanese eels Anguilla japonica from a river and an aquaculture unit in SW Taiwan

The infection by swimbladder nematodes of the genus Anguillicola (Dracunculoidea: Anguillicolidae) was examined in 2 populations of the Japanese eel Anguilla japonica in SW Taiwan. Wild eels from the Kao-Ping river were compared with cultured eels from an adjacent aquaculture unit. Only the cosmopolitan species Anguillicola crassus was present. Among wild eels, prevalence of infection varied between 21 and 62%, and mean intensity between 1.7 and 2.7 for adult worms. Similar intensity values (1.3 to 2.8) were recorded for the larvae. In cultured eels, prevalence as well as mean intensities were higher. In the cultured hosts, mean larval intensities exceeded those of adult worms 2-fold, and maximum larval intensities were 4- to 5-fold higher than in eels from the river. In cultured eels, dead larvae were also more abundant than in wild eels. We conclude that infrapopulations of A. crassus in Japanese eels are regulated by the defense system of this host, intraspecific density-dependent regulation being less likely as the major regulatory mechanism. No influence of the parasite on eel condition was found in either wild or cultured eels, indicating a low or moderate pathogenic effect of A. crassus on this host. This study shows that A. crassus is moderately common in cultured and wild Japanese eels in Taiwan, where the parasite is endemic.

Procamallanus (Spirocamallanus) anguillae sp. n. (Camallanidae) and some other nematodes from the Indonesian shortfin eel Anguilla bicolor in Thailand

A new species of parasitic nematode, Procamallanus (Spirocamallanus) anguillae sp. n. (family Camallanidae), is described based on specimens recovered from the intestine of the Indonesian eel Anguilla bicolor McClelland (type host) from southern Thailand (type locality Phuket Island). It is characterized mainly by the presence of 10-13 spiral ridges in the buccal capsule, length of spicules (366-372 microm and 198-216 microm), presence of a gubernaculum, arrangement of caudal papillae, and by the broad female tail with a digit-like projection bearing two cuticular spikes. In addition, two species of larval nematodes, Physalopteridae gen. sp. and Anisakis cf. simplex (Rudolphi 1809), were recorded from A. bicolor. All species are briefly described and illustrated.

Anguillicola papernai (Nematoda: Anguillicolidae) and other helminths parasitizing the African longfin eel Anguilla mossambica

The swim bladder nematode Anguillicola papernai Moravec & Taraschewski, 1988 has been investigated as regards its occurrence in longfin eels Anguilla mossambica (Peters) in rivers in South Africa. A. papernai revealed a prevalence of around 50% and a mean intensity of about 6 adult worms at 1 sampling site but were less abundant in 3 others. Field observations suggest a more narrow habitat preference than that of Anguillicola crassus and a seasonal pattern of abundance. African longfin eels harboured a poor helminth community. In addition to A. papernai, 2 gastro-intestinal nematodes occurred, the stomach worm Heliconema longissimum Ortlepp, 1923 as the dominant species, and the intestinal Paraquimperia africana Moravec, Boomker & Taraschewski, 2000. Experiments were undertaken using European eels Anguilla anguilla (Linnaeus) and copepods as laboratory hosts. The morphology of larvae and adult parasites obtained from these experimental hosts is described. The ultrastructure of adult worms recovered from wild longfin eels was studied. The 'papilla-like excrescences of fibrous structure' on the adult worms' cuticle, as mentioned in the original description, are in fact the attachment points of thick cords of fibers interconnecting the epicuticle with the hypodermis. Such a structure has not yet been described from any other species of Anguillicola Yamaguti, 1935. At present in South Africa, Mozambique and Madagascar attempts are on the way to establish an eel management like in Asia and Europe including eel farming. In this context, care should be taken to prevent the introduction of non-endemic eel parasites into Africa and Madagascar. On the other hand, the future commercial management of African eel species should not lead to the spread of A. papernai or other parasites of African eel species to Europe or elsewhere. In this study A. papernai has been experimentally demonstrated to be capable of reproducing in the European eel and of using European copepods as intermediate hosts.

Influence of Anguillicola crassus (Nematoda) and Ichthyophthirius multifiliis (Ciliophora) on swimming activity of European eel Anguilla anguilla

We investigated the swimming activity of 70 European eels Anguilla anguilla in relation to natural infection with 2 parasite species: the eel-specific swimbladder nematode Anguillicola crassus and the non-specific skin and gill protozoan Ichthyophthirius multifiliis. We measured how long individual eels exposed to a water current in a swimming channel with a steady-stream profile could withstand the water current. The parasites affected the swimming behaviour of eels in different ways. The maximum period of time the fish were able to swim against the current was not correlated with infection by A. crassus. In contrast, infection with I. multifiliis reduced the swimming time. The protozoan has a higher pathogenicity than the swimbladder nematode, at least in closed systems, where I. multifiliis is able to spread within a few days. Reduction in swimming capacity after infection with the ciliate averaged 47 % compared to capacity prior to infection. Thus, our results do not support the previously suggested strong negative relation between swimming activity of eels and intensity of A. crassus infection, at least in the short-term. However, there are indications in the literature that the pathological effects of A. crassus on the eel swimmbladder may involve a higher energy demand, possibly manifested in a prolonged spawning migration. As a result, eels heavily infected with this parasite may arrive too late at the spawning site to participate in mating. This could ensure a selection of 'good genes'.

The intestinal parasite Pomphorhynchus laevis (Acanthocephala) from barbel as a bioindicator for metal pollution in the Danube River near Budapest, Hungary

Concentrations of As, Al, Ag, Ba, Bi, Cd, Co, Cr, Cu, Fe, Ga, Mg, Mn, Ni, Pb, Sb, Sn, Sr, Tl, V and Zn were analyzed by inductively coupled mass spectrometry (ICP-MS) in the intestinal helminth Pomphorhynchus laevis and its host Barbus barbus. The fish were caught in the Danube river downstream of the city of Budapest (Hungary). Ten out of twenty one elements analyzed were found at higher concentrations in the acanthocephalan than in different tissues (muscle, intestine, liver and kidney) of barbel. Considering the fish tissues, most of the elements were present at highest concentrations in liver, followed by kidney, intestine and muscle. Spearman correlation analyses indicate that there is competition for metals between the parasites and the host. The negative relationships between parasite number and metal levels in organs of the barbel support this hypothesis. The bioconcentration factors for Ag, As, Ba, Bi, Cu, Ga, Mn, Pb, Sr, Tl, and Zn showed that the parasites concentrated metals to a higher degree than the fish tissues. They accumulated the metals As, Cd, Cu, Fe, Ni, Pb, Sr and Zn even better than established bioindicators such as the mussel Dreissena polymorpha as revealed by data from the literature. The results presented here emphasize that acanthocephalans of fish are very useful as sentinels for metal pollution in aquatic ecosystems. Ratio of metal concentrations in the parasites and the host tissues provide additional information. Not including acanthocephalans in accumulation bioindication studies with fishes (as still customarily done) may lead to false results.

Lead concentrations in Hymenolepis diminuta adults and Taenia taeniaeformis larvae compared to their rat hosts (Rattus norvegicus) sampled from the city of Cairo, Egypt

Concentrations of lead, determined by electrothermal atomic absorption spectrometry, were compared between the cestodes Hymenolepis diminuta and Taenia taeniaeformis and its host rat (Rattus norvegicus). Rats were sampled at 2 sites, which differed in respect to lead pollution as quantified from road dust, adjacent to the city of Cairo, Egypt. Comparing lead levels among host tissues and the parasites the significantly highest accumulation was found in H. diminuta, followed by rat kidney and larvae of T. taeniaeformis. Calculation of bioconcentration factors showed that H. diminuta contained 36-, 29-, 6- and 6-fold higher lead levels than intestinal wall, liver, kidney and larvae of T. taeniaeformis, at the more polluted site. At the less contaminated site lead bioconcentration factors for H. diminuta were found to be 87, 87 and 11 referred to intestine, liver and kidney of the host. Due to a high variability of the lead concentrations in H. diminuta it was not possible to indicate differences in metal pollution between both sampling sites. This variability may be influenced by different age structures of cestode infrapopulations. It is likely that younger worms contain lower metal levels than older worms due to a shorter exposure period. Thus, it is necessary to standardize the sampling of worms which should be used for indication purposes. Due to a lack of adequate sentinel species in terrestrial habitats more studies are required to validate and standardize the use of helminths as accumulation bioindicators in order to obtain mean values with low standard deviations. The host-parasite system rat-H. diminuta appears to be a useful and promising bioindication system at least for lead in urban ecosystems as rats as well as the tapeworm are globally distributed and easily accessible.

Accumulation and distribution of platinum and rhodium in the European eel Anguilla anguilla following aqueous exposure to metal salts

The platinum group metals (PGM) Pt and Rh are emitted into the environment mainly by catalytic exhaust gas converters of cars and by effluents of hospitals, which use Pt based anti-cancer drugs. However, there is still a lack of information on the availability of these precious metals to the biosphere. As PGM accumulate in sediments of aquatic ecosystems we focused our study on the uptake of the noble metals by European eels, Anguilla anguilla. Therefore, eels were exposed in tap water and humic water containing Pt(4+) and Rh(3+) at a concentration of 170 and 260 microg/l, respectively. After an exposure period of 6 weeks the mean Pt levels in bile, liver, kidney and intestine of the exposed eels ranged between 68 ng/g and 840 ng/g and the mean Rh levels between 35 ng/g and 155 ng/g whereas the PGM levels of the unexposed controls were below the detection limit of 50 ng/g for Pt and 5 ng/g for Rh. Rh was also taken up by gill and spleen. No PGM uptake was found for muscle and blood. The pattern of metal distribution within the eel differed between Pt and Rh and was dependent on the water type. Due to their accumulation capacity for PGM eels are suitable as accumulation indicators to detect PGM pollution in aquatic ecosystems.

The acanthocephalan Paratenuisentis ambiguus as a sensitive indicator of the precious metals Pt and Rh from automobile catalytic converters

Recent studies revealed that intestinal acanthocephalans of fish can accumulate heavy metals to concentrations orders of magnitude higher than those in the host tissues or the aquatic environment. This significant heavy metal accumulation by acanthocephalans, even surpassing that of established free living accumulation bioindicators, encouraged us to study the bioavailability of the platinum-group-metals (PGM) Pt and Rh for parasites. These precious metals are used in catalytic converters of cars for exhaust gas purification in Europe since the early 1980s. In addition to the beneficial effect in reducing the emission of CHx, CO and NOx of cars there is an increasing emission of these metals. However, it still remains unclear if these elements become accumulated in the biosphere and whether they affect the health of organisms. The present study reveals that in European eels (Anguilla anguilla) naturally infected with the eoacanthocephalan parasite Paratenuisentis ambiguus and experimentally exposed to ground catalytic converter material, the parasites take up and accumulate the catalytic active metals Pt and Rh whereas in the examined host tissues we found no metal uptake. Compared with the PGM concentrations in the water the worms contained 1600 times higher Rh and 50 times higher Pt concentrations. Thus, the parasites can be used as sentinel organisms reflecting even very low levels of precious metals.

Interaction between cadmium exposure and infection with the intestinal parasite Moniliformis moniliformis (Acanthocephala) on the stress hormone levels in rats

The impact of an infection with the acanthocephalan Moniliformis moniliformis and a simultaneous Cd-exposure on the stress hormone levels of rats was studied. Immediately after the application of cadmium to some rats, cortisol levels in all groups of rats, as quantified by radioimmunoassay (RIA), significantly increased. However, infections with M. moniliformis as well as the uptake of Cd reduced significantly the cortisol release compared to untreated controls. While catecholamine concentrations, as determined by high-performance liquid chromatography (HPLC), showed no clear tendency during the experimental period, the ratio of C(adrenaline)/C(noradrenaline) in the controls showed the significantly lowest value of all four groups after killing the animals. Thus, the acanthocephalan infection as well as the Cd-exposure and the combination of both treatments affect hormone homeostasis in the rats which probably lead to negative effects on the health of the rat. Therefore parasite infections must be carefully considered in environmental impact studies, as an important factor affecting the host's health.

Evaluation of an ELISA and immunoblotting for studying the humoral immune response in Anguillicola crassus infected European eel Anguilla anguilla

The applicability of an enzyme-linked immunosorbent assay (ELISA) for the detection of anguillicolosis in feral eels was examined using a crude antigen preparation from the body wall of adult Anguillicola crassus. The screening consisted of samples from 100 feral European eels Anguilla anguilla. As a reference the actual status of infection was determined by dissection of the eels' swim-bladders. The ELISA results were compared with a background value calculated from the results obtained from 43 non-infected farm eels. The screened samples had a high prevalence of A. crassus (83 %); however, the specificity and the negative predictive value of the ELISA were low compared to the high positive predictive value. Nonetheless, the reproducibility (precision) of the test was satisfactory, and for the non-infected reference group specificity was 97.7 %. Although the ELISA, as used in the present study, is not applicable for diagnostic purposes, it represents a useful tool for the investigation of the specific humoral immune response of eels against A. crassus under controlled experimental conditions. Immunoblots using crude antigen preparations from different parts of adult A. crassus as well as a crude somatic third-stage (L3) antigen preparation illustrated that only antigens associated with the body wall of adult A. crassus are potentially suitable for diagnostic purposes. Despite the fact that antibodies against Raphidascaris acus cross-reacted with 3 body wall antigens of A. crassus, the most encouraging results were obtained with the antigen preparation from the outer cuticle of adult A. crassus which yielded a conspicuous, broad band at about 100 kDa.

Accumulation and distribution of lead in the archiacanthocephalan Moniliformis moniliformis from experimentally infected rats

It recently became clear that adult eo- and palaeacanthocephalans parasitizing fish can bioconcentrate several heavy metals to significantly higher concentrations than the tissues of their definitive hosts. Following this discovery the lead accumulation of the archiacanthocephalan Moniliformis moniliformis was investigated using experimentally infected male Wistar rats of the CD-M-strain. The worms were allowed to grow up for 4 weeks post-infection followed by a 3 weeks oral lead exposure of the rats. After the exposure period the rats were killed and the metal levels were determined in muscle, liver, intestine and kidney of the rats as well as in different organs of female and male acanthocephalans. Lead concentrations were found to be highest in female M. moniliformis followed by the kidneys of the rats. Male worms contained approximately the same lead concentration as the hosts' kidneys. Lead analysis of the worms' organs revealed the highest lead concentration in the eggs of female acanthocephalans, followed by the cement gland of male Worms. Whilst the lead burden of the presoma was higher than that detected in the kidneys of the rats, the lead content of the metasoma was even lower than in the kidneys. A lead uptake of M. moniliformis from the intestinal lumen of the host became apparent as the faeces of infected rats contained significantly less lead compared to the uninfected conspecifics. Thus, this study reveals that lead accumulation also occurs in archiacanthocephalans parasitizing mammals. But the degree of metal bioconcentration is considerably lower compared to eo- and palaeacanthocephalans in fish. Anyway, due to a lack of adequate sentinel species in terrestrial biotopes the host-parasite system rat M. moniliformis appears to be a useful and promising bioindication system especially in urban ecosystems in temperate regions.

Element concentrations in the archiacanthocephalan Macracanthorhynchus hirudinaceus compared with those in the porcine definitive host from a slaughterhouse in La Paz, Bolivia

Concentrations of lead and cadmium, determined by electrothermal atomic absorption spectrometry, and concentrations of the elements barium, cadmium, copper, iron, magnesium, manganese, nickel, lead, selenium and strontium, determined by inductively coupled plasma mass spectrometry, in the acanthocephalan Macracanthorhynchus hirudinaceus and its porcine final host, sampled at a slaughterhouse in La Paz, Bolivia, were compared. Inductively coupled plasma mass spectrometry analysis revealed that most of the elements were found at higher concentrations in the acanthocephalan than in different tissues of its host. The bioconcentration of elements in M. hirudinaceus compared with the host intestine, listed in order of decreasing values, was as follows: Cd > Pb > Ni > Sr = Cu > Mg > Se > Fe = Mn = Ba. Analysis by electrothermal atomic absorption spectrometry showed that M. hirudinaceus contained 85, 85, 56 and 24 times higher lead levels compared with hosts muscle, liver, kidney and intestine, respectively. The mean cadmium concentration of the parasite was 32 times higher than that of the liver and five times higher compared with porcine kidney. The metal distribution within the body of M. hirudinaceus was as follows: cement gland > testes > lemnisci > eggs = tegument for lead and lemnisci > testes > cement gland > tegument > eggs for cadmium. Therefore, the hypothesis that parasites excrete toxic metals with the shells of their eggs seems not to be valid for M. hirudinaceus. It is concluded, that not only eoacanthocephalans and palaeacanthocephalans parasitising fish, but also archiacanthocephalans from mammalian hosts, are able to bioaccumulate metals.

Leiperia cincinnalis Sambon, 1922 (Pentastomida) from Nile crocodiles Crocodylus niloticus in the Kruger National Park, South Africa, with a description of the male

A single male and several adult females of the pentastomid Leiperia cincinnalis were recovered from the trachea of five of six Nile crocodiles examined in 1995 and 1998. Infective larvae, pre-adult males and females, as well as mature males, occurred in clusters in the pulmonary artery but infective larvae and pre-adult females were also occasionally taken from the lungs. Irrespective of the developmental stage, the intensity of infection was 3, 6, 48, 72 and 79. Sixty-four percent of eggs recovered from the posterior part of the uterus of a patent L. cincinnalis female contained fully-developed primary larvae and these were used to infect 24 Mozambique bream Oreochromis mossambicus. Within a week of infection all the fish died and hatched primary larvae were recovered from the stomach and anterior part of the intestine. Eggs that had not hatched were found to be unsegmented. The total primary larval count in seven fish was 18, 12, 1, 25, 16, >40 and >50. Descriptions with detailed measurements are given of the females, the males, the eggs, the primary larvae and the infective larvae of L. cincinnalis.

Humoral immune response of European eel Anguilla anguilla experimentally infected with Anguillicola crassus

A humoral immune response of the European eel Anguilla anguilla elicited by an experimental infection was demonstrated for the first time against the swimbladder nematode Anguillicola crassus. Eels were experimentally infected once or repeatedly and the antibody response was observed over a period of 325 d. Specific antibodies against A. crassus in the peripheral blood of the eels were measured using an ELISA and the immunoblot technique. Anti-A. crassus antibodies were first observed 8 wk post infection, and appeared to be independent of both the number of infective third stage larvae (L3) administered and the frequency of administration. However, individual eels showed great differences in the course of the antibody response. The late appearance of antibodies in the peripheral blood supports the hypothesis that not the invading L3 but rather the adult parasites elicit the production of specific antibodies. A stage-specific antibody response against the L3 was not observed. Main antigens are located in the body wall, especially in the gelatinous outer cuticle, of adult A. crassus.

Cadmium accumulation in Moniliformis moniliformis (Acanthocephala) from experimentally infected rats

The accumulation of cadmium in Moniliformis moniliformis parasitizing experimentally infected rats that had been orally exposed to cadmium was investigated in this study. Cadmium accumulation in the helminth and in different tissues of the host was determined using electrothermal atomic absorption spectrometry (AAS) after a 3-week period of exposure. The mean cadmium concentration measured in M. moniliformis was 5.8 microg g(-1) wet weight, which was 20, 23, and 119 times higher than that determined in the kidney, liver, and intestine of the host, respectively. Although female worms accumulated higher amounts of cadmium than did males, no tendency emerged between the cadmium concentration and the weight of individual acanthocephalans. This study reveals that cadmium accumulation also occurs in archiacanthocephalans, but to a lesser degree than in palaeacanthocephalans parasitizing fish. Due to its cadmium-accumulation capacity, M. moniliformis might be used as a highly sensitive free-living bioindicator in terrestrial and urban ecosystems.

Host-parasite interactions in Acanthocephala: a morphological approach

In this review recent morphological and histochemical descriptions have been compiled of (mainly outer) features of all developmental stages of the Acanthocephala as well as what is known about the host's defence measures directed against these worms. From acanthors, for instance, it is documented how they escape melanization inside the haemocoel of a suitable intermediate host after they have been activated and released from their eggshell enclosure in the gut of the arthropod. Acanthors possess a complex set of eggshell-envelopes and interstices that fulfil different tasks. While the sequence of events inside the intermediate host's haemocoel is rather well known, what happens in paratenic hosts has been little studied. In final hosts the host-parasite interactions depend on the systematic affiliation of the parasite as well as the host and on the depth of penetration of each acanthocephalan species in the intestinal wall of the host. The mode of attachment also influences the microhabitat preference inside the gut. Mammals often reveal symptoms of high morbidity when infected with acanthocephalans, while fish seem to tolerate high intensities of worms deeply penetrating into their intestinal wall without showing pronounced symptoms of disease. The review also treats the subjects of host specificity, nutrient uptake and metabolism of the worms as well as their absorbance of metals and other elements. The high absorbance capacity for heavy metals suggests the usefulness of acanthocephalans as bioindicators.

Paraquimperia Africana n. sp (Nematoda : Quimperiidae), a new intestinal parasite of the eel Anguilla mossambica Peters, in South Africa

A new seuratoid nematode of the family Quimperiidae, Paraquimperia africana n. sp., is described from the small intestine of the longfin eel, Anguilla mossambica Peters, from the Eastern Cape Province, South Africa. The new species is characterized mainly by the presence of a ventral sucker in mature males, short spicules (147-171 microm), the number and arrangement of caudal papillae, the postesophageal position of the excretory pore, and by the slender female tail. In this new species, a variability in the number (3-5 pairs) of subventral preanal papillae was observed. Paraquimperia africana is the first representative of the genus in Africa. In view of recent reports, Paraquimperia aditum (Mueller, 1934) is considered a junior synonym of Paraquimperia tenerrima (Linstow, 1878). Paraquimperia xenentodonia Gupta and Bakshi, 1984 is considered a species inquirenda.

Histopathological changes in the swimbladder wall of the European eel Anguilla anguilla due to infections with Anguillicola crassus

The histopathological changes in swimbladders of European eels naturally and experimentally infected with Anguillicola crassus were studied using transmission and scanning electron microscopy. During the course of probably several infections swimbladders undergo characteristic changes. In addition to the thickening of the entire swimbladder wall, and to the folded internal surface of this organ, inflammation, migration of white blood cells, fibrosis and changes in the epithelial cells are frequently seen. Epithelial cells tend to proliferate heavily and form hyperplastic tissues; these processes are accompanied by changes in the internal structure of the cells. The normally cubic cells become spherical or columnar and form folds facing the lumen of the swimbladder. As a consequence, most of these cells lose contact with the blood vessels and show no strict polarity. In heavily affected swimbladders the basal labyrinth of the epithelial cells is reduced, i.e. becomes shorter and less densely packed. The lamina propria shows severe fibrosis with infiltration of white blood cells. Larvae of A. crassus, inhabiting the wall of the swimbladder, were found to be surrounded by cell debris, but this local necrosis does not affect the entire swimbladder in its overall structure. These histological findings can partly explain changes in the gas composition in eels infected with A. crassus.

Development of Anguillicola crassus (Dracunculoidea, Anguillicolidae) in experimentally infected Balearic congers Ariosoma balearicum (Anguilloidea, Congridae)

The development of Anguillicola crassus in experimentally infected Ariosoma balearicum (Anguilloidea, Congridae) kept in seawater was studied in the laboratory. In parallel trials the effect of water salinity on the development of larval A. crassus in European eels Anguilla anguilla was also investigated using eels kept in seawater of a salinity of 34 per thousand. Both eel species were orally inoculated with L3 larvae of A. crassus and then maintained for up to 3 mo at 18 degrees C in seawater. 110 d post infection, no adult but larval (L3 and L4) stages of A. crassus were detected in the swimbladder wall of Balearic congers, although this period of time was sufficient for the parasites to develop to the adult stage in European eel kept in seawater. The results presented suggest that the definitive host specificity of A. crassus comprises species of the family Anguillidae (i.e. the genus Anguilla), but not members of the Congridae. Theoretically however, A. balearicum might serve as a metaparatenic host. Factors determining the definitive host range of A. crassus remain to be elucidated. Water salinity does not seem to act as a factor affecting definitive host specificity once the parasite has become ingested by the eel.

Experimental studies on lead accumulation in the eel-specific endoparasites Anguillicola crassus (Nematoda) and Paratenuisentis ambiguus (Acanthocephala) as compared with their host, Anguilla anguilla

The effect of salinity and the mode of application (oral versus aqueous) on the lead accumulation in different tissues of the fish host eel (Anguilla anguilla) and its parasites Anguillicola crassus (Nematoda) and Paratenuisentis ambiguus (Acanthocephala) was investigated. Waterborne as well as dietary lead exposure caused an increase in the metal levels of different eel tissues and the parasites. The mode of lead application had a significant influence on the distribution of lead in the fish tissues. No significant difference on the lead concentration due to water salinity was found for the fish tissues. Among the analyzed tissues and helminths, the intestinal acanthocephalan P. ambiguus contained the significantly highest amounts of lead, which were affected by neither the mode of application nor the water salinity. In contrast, the lead level of the nematode A. crassus dwelling in the swim bladder of eels was even below the levels detected for host liver, intestine, and bile. Thus, depending on the mode of lead application, the resulting metal concentrations were approximately 20 to 2,000 times higher in P. ambiguus than in A. crassus. These differences may be due to the different microhabitats and nutrient uptake mechanisms of both parasite species. This study presents important new facts for the use of intestinal fish parasites as biological indicators for water quality, not only in freshwater, but also in marine and estuarine ecosystems. The combination of the results obtained from the host and the parasites could reveal a more detailed tool to ascertain the source of an environmental contamination than a study based on a single species.http://link.springer-ny. com/link/service/journals/00244/bibs/37n2p190.html

Parasites as accumulation indicators of heavy metal pollution

Parasites are attracting increasing interest from parasite ecologists as potential indicators of environmental quality because of the variety of ways in which they respond to anthropogenic pollution. However, until recently, little was known about the accumulation of toxins within parasites. Certain parasites, particularly intestinal acanthocephalans and cestodes of fish, can accumulate heavy metals at concentrations that are orders of magnitude higher than those in the host tissues or the environment. In this review, Bernd Sures, Roy Siddall and Horst Taraschewski discuss the recently described phenomenon of conspicuous metal accumulation by parasites and how this might be applied to environmental monitoring. They also suggest how environmental science and parasitology might profit from each other in the near future.

Detection of Cryptosporidium parvum in human feces by PCR

C. parvum has a high pathologic potential also for man, especially for immununosuppressed patients. The microscopic detection of cysts in feces is neither easy nor always reliable. During the recent years, considerable progress has been achieved in establishing PCR-based approaches for i) sensitive detection of C. parvum in a variety of specimen types [3, 9-16, 18, 21, 24, 25, 27, 29-32, 34], ii) identification of individual genotypes of C. parvum [2, 4-7, 17, 19, 20, 22, 23, 26, 28, 33] and iii) viability testing of C. parvum organisms [8, 9, 13, 29, 30]. The protocols published so far include nested PCR [3, 8, 18, 34], RT-PCR [13, 29], and use of the UNG carryover prevention system [10]. The aim of this work was to establish a PCR system for the detection of C. parvum oocysts in stool samples, applying the same specimen preparation procedure as applied for immunofluorescence. In addition, we combined the UNG carryover prevention system with the use of long, PCR-generated digoxigenin-labelled probes, thus achieving a sensitivity comparable to nested PCR und circumventing the contamination risks associated with nested PCR protocols. We developed a simplified sucrose-cushion-based protocol for preparation of clinical specimens (adopted from [1]), satisfying both the needs of immunofluorescence and PCR. When tested with stool samples spiked with C. parvum oocysts, the analytical sensitivity of PCR was 3,500 oocysts/ml stool (immunofluorescence: 3,000 oocysts/ml stool), demonstrating that both methods were equivalent with respect to analytical sensitivity. However, when PCR and immnunofluorescence were applied to clinical samples (n=5) with known positivity for C. parvum, only the specimen with the shortest duration of storage (5 weeks) could be correctly identified by PCR (clinical sensitivity: 20%). Our results demonstrate, that the PCR approach presented in this work is not suited for highly sensitive detection of C. parvum in faeces. This was mainly due to the fact that sucrose-gradient purified material was used, which relies on the presence of morphologically intact oocysts in the specimens. Desintegration of oocysts by excystation and/or storage may lower the parasite yield of the protocol drastically. As a consequence, a protocol extracting the entire DNA from faeces should be used for PCR for detection of C. parvum [34].

Relative concentrations of heavy metals in the parasites Ascaris suum (Nematoda) and Fasciola hepatica (Digenea) and their respective porcine and bovine definitive hosts

The concentrations of lead and cadmium determined by electrothermal atomic absorption spectrometry were significantly higher in the liver and kidney, respectively, of pigs than in their intestinal nematode parasites Ascaris suum. There was no clear pattern in the distribution of lead within the ascarids, but cadmium concentrations were highest in the intestine. A parallel investigation of cattle naturally infected with the liver fluke, Fasciola hepatica, revealed interesting differences. Although the cadmium content of F. hepatica was considerably lower than that in the tissues of cattle, the concentration of lead in the digenean was on average 172, 53 and 115 times higher than in the muscle, kidney and liver of the host. Furthermore, there was a significant positive correlation between the weight of individual F. hepatica and their lead burden. The lack of appreciable heavy-metal accumulation in A. suum is consistent with results for the nematode Anguillicola crassus in fish. However, although lead concentrations in the liver fluke F. hepatica were considerably elevated above host tissue levels, the degree of heavy-metal accumulation was relatively low when compared to that of acanthocephalans and cestodes of fish.

Impact of low water temperature on the development of Anguillicola crassus in the final host Anguilla anguilla

The effect of low water temperatures on the development and viability of larval and adult Anguillicola crassus (Nematoda) in the final host Anguilla anguilla was studied. European eels were experimentally infected with A. crassus and then maintained for 4 mo at 4, 9, 10, and 19 degrees C. Larval development showed a temperature-dependent pattern and was significantly retarded at low temperatures. Third-stage larvae survived a 4 mo period at 4 degrees C without being affected, although they were not able to invade the swimbladder wall at this temperature. In contrast, adult worms were severely harmed during a 4 mo period at 4 degrees C, as reflected by increased mortality and decreased growth and reproductivity as compared to the worms maintained for the same period at 18 degrees C. Starvation for the eels at 4 mo at 19 degrees C did not affect the development and growth of the nematode. The experimentally obtained results support the hypothesis that the spread of A. crassus in boreal regions, e.g. Northern Europe, is restricted by the natural ambient temperature regimes.

Distribution and prevalence of Anguillicola crassus (Nematoda) in eels Anguilla anguilla of the rivers Rhine and Naab, Germany

Over a period of 2 yr eels were collected at several sites along the river Rhine as well as from adjacent waters and examined for Anguillicola crassus in the swimbladder. Additionally eels were collected once from a site on the river Naab (Danube system). All eels were searched for both juvenile and adult stages of A. crassus, revealing prevalences of 80% in eels from the river Rhine and 39% in eels from the river Naab. The mean intensities were 5.6 and 7.7, respectively. With respect to the prevalence and mean intensity of infection, no significant differences were observed between the different sampling sites in the Rhine system. Neither the prevalence nor the intensity showed significant seasonal patterns. Further, no correlation between the condition factor of the eels and intensity of infection with A. crassus could be found. Of all eels examined, 28% showed pathological alterations of the swimbladder.

Heavy metal concentrations in adult acanthocephalans and cestodes compared to their fish hosts and to established free-living bioindicators

Intestinal helminths of fish caught from freshwater and brackish water biotopes throughout Europe were analysed by electrothermal atomic absorption spectrometry for their heavy metal (Pb and Cd) levels. The metal concentrations of the parasites were compared to those of different organs (muscle, liver, intestine) of the fish hosts and to those detected in the whole bodies of the respective intermediate hosts. The three acanthocephalan species analysed contained very high amounts of Pb and Cd. The lead level of Pomphorhynchus laevis was up to 2700 times higher and the cadmium concentration was approximately 500 times higher than the muscle of chub, its host. Concurrent analysis of larval acanthocephalans in the crustacean intermediate host indicated that the bioconcentration of heavy metals by these parasites occurs only in the final host. In two species of cestodes accumulation of metals was also recorded although the degree of bioconcentration was somewhat lower. Nevertheless, Monobothrium wageneri contained 75 times more Pb and 43 times more Cd than the muscle of its host, the tench. In contrast, no bioconcentration of heavy metals was detected in the swimbladder nematode Anguillicola crassus. It contained less lead than the muscle of its final host, the eel. In one biotope the concentration of 18 elements was compared between the whole soft tissues of the zebra mussel, Dreissena polymorpha, the parasite Acanthocephalus lucii and its final host, perch. The acanthocephalan accumulated most of the elements to considerably higher concentrations than the zebra mussel, which has been considered an effective bioindicator of heavy metals. The sessile nature of the zebra mussel may allow a better identification of small-scale local differences in environmental heavy metal contamination. However, acanthocephalan parasites will provide an ecologically-important index of average exposure of their mobile fish host to biologically-available metals within its natural range.

Syncytial organization of acanthors of Polymorphus minutus (Palaeacanthocephala), Neoechinorhynchus rutili (Eoacanthocephala), and Moniliformis moniliformis (Archiacanthocephala) (Acanthocephala)

The fine structures of immature and of developed shelled acanthors of three species belonging to the three subgroups of the Acanthocephala were investigated. Acanthors are surrounded by four eggshells (embryonic envelopes) and are composed of three syncytia: a frontal syncytium, a central syncytium, and an epidermal syncytium. Neither a sense organ nor a nervous system has been found. The central syncytium shows a mass of condensed nuclei and 12 decondensed nuclei and gives rise to 10 anterior/posterior subepidermal myofibrillar systems and 2 oblique retractor muscles. Circular muscles are missing. A single decondensed nucleus can be assigned to each of the 12 muscular systems. The epidermal syncytium embeds the other two syncytia and forms the wrinkled epidermis, which shows an extracellular glycocalyx and intrasyncytial condensations. Prominent recurved hooks, which mark the anterior end of each acanthor, and body spines are intraepidermal differentiations. Partly branched tubular infoldings of the epidermal plasma membrane of the acanthor exist and represent precursors of the pore ducts typical of the adult epidermis. Autapomorphies in the ground pattern of the monophylum Acanthocephala are the four eggshells, the early development of three syncytia, the condensed nuclei in the central syncytium, and the differentiation of ten longitudinal muscle bands and two muscle retractors and of intraepidermal hooks and spines. The syncytial organization of the epidermis with intraepidermal skeletal condensations and infoldings of the apical plasma membrane are characteristics inherited from a stem species common to Acanthocephala, Seison, and Rotifera.

Lead and cadmium content of two cestodes, Monobothrium wageneri and Bothriocephalus scorpii, and their fish hosts

The adult cestodes Monobothrium wageneri and Bothriocephalus scorpii from the intestines of their respective final hosts, tench (Tinca tinca) caught in the river Ruhr, Germany, and turbot (Scophthalmus maximus) collected from two sampling sites on the coast of Gdansk, Poland, were analyzed for lead and cadmium by atomic absorption spectrometry. Both cestode species contained significantly higher cadmium contents than did the muscle, liver, and intestine of their fish hosts. Whereas M. wageneri also contained several times more lead than did the organs of tench, B. scorpii showed nearly the same lead burden as did the liver and intestine of turbot. Posterior sections of B. scorpii comprising gravid proglottids contained significantly higher concentrations of lead and cadmium than did the anterior proglottids.

Changes in gas composition in the swimbladder of the European eel (Anguilla anguilla) infected with Anguillicola crassus (Nematoda)

The effect of Anguillicola crassus (Nematoda) on gas composition in the swimbladder of eels (Anguilla anguilla) was studied using mass spectrometry in feral eels from two German rivers and in experimentally infected eels. In both naturally and experimentally infected eels significant correlations were observed between the proportion of oxygen in the swimbladder and level of infection with Anguillicola crassus. In swimbladders of naturally infected feral eels the contribution of oxygen to swimbladder gas was reduced by 36-62.9% and in experimentally infected eels it was reduced by 11.4-57% compared to uninfected controls. The proportion of CO2 appeared to be lower in infected swimbladders compared to uninfected ones. However, this change was not significant. The findings are discussed in relation to an altered structure of the swimbladder wall due to the parasite.

Chain elongation of fatty acids in the fish parasite Paratenuisentis ambiguus (Acanthocephala)

An active enzyme system for fatty acid chain elongation exists in Paratenuisentis ambiguus (Acanthocephala), which elongates [1-14C]palmitic acid consecutively to stearic and arachidic acid. Highest specific activity of radioactive elongation products was detected in phosphatidylethanolamines that seem to play an outstanding role as acceptors of saturated long-chain and very long-chain fatty acids. In contrast, incubation of P. ambiguus with monounsaturated [1-14C]oleic acid under similar conditions led to small proportions of labeled eicosenoic acid only. Analysis of the fatty acid pattern and stereospecific distribution at the glycerol backbone of phospholipids revealed that saturated acyl moieties with 18, 20, and 22 carbon atoms were esterified almost exclusively in the sn-1 position of phosphatidylethanolamines and -cholines, whereas polyunsaturated fatty acids were found predominantly in the sn-2 position of these phospholipids. From these results it may be concluded that the parasite channels saturated long-chain and very long-chain fatty acids predominantly to the sn-1 position of phospholipids in order to compensate for increasing membrane fluidity caused by the incorporation of high proportions of polyunsaturated fatty acids of aquatic feed.

Lipids of fish parasites and their hosts: fatty acid fingerprints of four species of acanthocephalans and of their hosts' intestinal tissues

The fatty acid fingerprints of total lipid extracts from the four fish parasites Acanthocephalus lucii, Neoechinorhynchus rutili, Paratenuisentis ambiguus, and Pomphorhynchus laevis were investigated by capillary gas-liquid chromatography (GLC). The fatty acid patterns of the parasites were compared with those of their respective host tissue, viz., intestinal tract tissue of infected perch, brown trout, eel, and chub. The highly complex gas chromatograms revealed significant differences not only between parasite and host tissue but also between the parasites themselves. For instance, all the parasites contained much more eicosapentaenoic acid (20:5n-3) than did the respective fish intestinal tissue. Differences were also observed between the presoma and metasoma of Pomphorhynchus laevis.

Cadmium concentrations in two adult acanthocephalans, Pomphorhynchus laevis and Acanthocephalus lucii, as compared with their fish hosts and cadmium and lead levels in larvae of A. lucii as compared with their crustacean host

Adults of Pomphorhynchus laevis and Acanthocephalus lucii were analyzed for cadmium by atomic absorption spectrometry. Their cadmium concentrations were compared with those found in different tissues (muscle, liver, and intestine) of their final hosts the chub and perch. Additionally, the cadmium and lead concentrations in larvae of A. lucii and their intermediate host Asellus aquaticus were determined. Regarding the adult acanthocephalans, the parasites showed several times more cadmium than did the tissues of their fish hosts. In contrast to this obvious accumulation capacity of adult A. lucii, the larvae contained less cadmium than did their crustacean host. Thus, the cadmium concentration in the larval stages was nearly 180 times lower than that measured in the adult worms. According to the present results, it appears that the heavy metals cadmium and lead are predominantly accumulated by the adult acanthocephalans inside the fish gut and not by the larvae inside the hemocoel of the crustaceans.

Metabolism of long-chain fatty acids, alcohols and alkylglycerols in the fish parasite Paratenuisentis ambiguus (Acanthocephala)

Specific differences between the acyl composition of lipids of the helminth Paratenuisentis ambiguus and its host eel, as shown previously, prompted us to study the lipid metabolism in this intestinal fish parasite. Adults and larvae of P. ambiguus were fed various lipid precursors, e.g., fatty acids, long-chain alcohols and 1-O-alkylglycerols, which may occur as common nutrients of intestinal parasites. Incorporation of [1-14C]palmitic acid into neutral and polar lipids was found to be similar under aerobic and near-anaerobic conditions. In adult parasites maintained in culture medium supplemented with glucose, [1-14C]palmitic acid was incorporated mainly into triacylglycerols and phosphatidylcholines, whereas [1-14C]oleic acid was incorporated preferentially into triacylglycerols. In fasted adults, as well as in larvae, [1-14C]oleic acid was mainly transferred to phosphatidylcholines. Lipolytic activity was detected in adult parasites that had been incubated with radioactive trioleoylglycerol. [1-14C]Hexadecan-1-ol was oxidized in P. ambiguus at a high rate to labeled palmitic acid, which was incorporated into various lipid classes of P. ambiguus. Small but significant proportions of radioactivity from hexadecan-1-ol were incorporated into ether glycerolipids of the parasite. A more direct precursor in ether glycerolipid metabolism, i.e., rac-1-O-[1'-14C]hexadecylglycerol, was incorporated into alkyl and 1'-alkenyl moieties of choline and etha-nolamine ether-glycerophospholipids of P. ambiguus in high yield. High proportions of labeled diacylglycerols, triacylglycerols and steryl esters were detected in surface lipids as well as lipid extracts of the culture media after incubation of P. ambiguus with [1-14C]palmitic or [1-14C]oleic acids.(ABSTRACT TRUNCATED AT 250 WORDS)

Proteinase activity in the plerocercoid of Proteocephalus ambloplitis (Cestoda)

Host invasion and tissue migration of several helminths have been linked to expression and release of parasite-derived proteinases. The plerocercoid of the cestode Proteocephalus ambloplitis can migrate into the visceral organs or, in the case of bass, from them into the intestinal tract of the same individual fish. It does this within a few hours, aided by secretion of a substance from its apical gland. Proteinase activity in this plerocercoid, obtained from the host liver, was defined by pH optimum, by substrate and inhibitor specificity, and by electrophoretic and chromatographic techniques. Homogenates of plerocercoid contained a metalloproteinase exhibiting a molecular weight of 30,000 determined by gelatin substrate gel electrophoresis. Peak activity of this proteolytic enzyme in gel filtration fractions when azocoll was used as substrate then corresponded to a molecular weight of 31,500. The proteinase showed collagenolytic, haemoglobinolytic and slight elastinolytic activity, and it had a pH optimum at 9.0. Enzyme activity could be inhibited by various chelating agents. The metalloproteinase identified in this study constitutes the only enzyme class present in this larval stage of P. ambloplitis. We suggest that the plerocercoid's metalloproteinase is the substance secreted from the apical organ, necessary for the previously recognized tissue migration phase. This enzyme might also have a nutritional function.

Lead accumulation in Pomphorhynchus laevis and its host

Adults of Pomphorhynchus laevis were collected from the intestines of 10 chubs (Leuciscus cephalus) from the river Ruhr near Bochum, Germany. The acanthocephalans and various tissues of the fish (muscle, liver, and intestine) were analyzed for lead with electrothermal atomic absorption spectrometry. The mean lead level in the parasite was 54 micrograms/g wet weight, which was 284 times more than in the host intestine, 771 times more than in host liver, and 2,700 times more than in host muscle. Thus, P. laevis may serve as a very sensitive bioindicator for the presence of biologically available lead in aquatic ecosystems.

Sterol and fatty acid composition of neutral lipids of Paratenuisentis ambiguus and its host eel

The sterol composition of free sterol and steryl ester fractions of the fish parasite Paratenuisentis ambiguus was determined. In addition, the fatty acid composition of various neutral lipid classes, i.e., wax esters, steryl esters, triacylglycerols and free fatty acids, as well as the composition of the 1-O-alkyl moieties of total ether glycerolipids of the parasite, were investigated. The results of these studies were compared with those obtained on the intestinal tract tissue of its host, the eel (Anguilla anguilla). Cholesterol is the major sterol in both P. ambiguus and A. anguilla. However, the sterols of P. ambiguus contain high proportions (> 20%) of other sterols, such as campesterol and various dehydrosterols. [e.g., 7-dehydrocholesterol and cholesta-5,22(E)-dienol]. The presence of these minor sterols agrees with the known biotransformations of exogenous sterols in various helminths. Considerable differences are found in the fatty acid composition of neutral lipid fractions, as well as the total lipid extract from the endoparasite as compared to the host tissue. In particular, eicosapentaenoic acid (20:5n-3), other polyunsaturated fatty acids, such as 20:4n-6, 22:5n-3 and 22:6n-3, as well as long-chain saturated fatty acids, such as 20:0, are generally enriched in the neutral lipid fractions of the parasite as compared to those of infected eel intestine.(ABSTRACT TRUNCATED AT 250 WORDS)

Proteolytic enzymes of Pomphorhynchus laevis and in three other acanthocephalan species

Cystacanths and adults of the acanthocephalan Pomphorhynchus laevis were found to release proteolytic enzymes during in vitro culture. Culture media in which cystacanths had been kept contained a trypsinlike collagenolytic proteinase exhibiting a molecular mass of 29 kDa on gelatin substrate gel electrophoresis and a pH optimum at pH 9.0. Samples of adults possessed a trypsinlike collagenolytic proteinase with a molecular mass of 26 kDa and showed a pH optimum at 9.0. Leucine aminopeptidase activity was also present in culture media of adults. An apparent molecular mass of 92 kDa and a pH optimum at pH 8.5 were determined for this proteolytic enzyme. It was concluded that the trypsinlike proteinases of both stages were necessary for the complete and quick perforation of the fishes' intestinal wall, whereas the leucine aminopeptidase seemed to have a nutritional function in the terminal stages of protein hydrolysis at the surface of the worm's body wall. Cystacanths of 3 other species of fish-parasitizing Acanthocephala (Acanthocephalus anguillae, Acanthocephalus lucii, Paratenuisentis ambiguus) did not show any histolytic activity.

Identification and characterization of the proteolytic enzymes in the developmental stages of the eel-pathogenic nematode Anguillicola crassus

The proteolytic activities of homogenates prepared from the second larva (L2) and the third larva (L3) as well as the adult stage of the eel-pathogenic nematode Anguillicola crassus were examined using hemoglobin, azocoll, elastin-orcein, and keratin azure as substrates. Whole bodies of L2 larvae, the anterior third of the bodies of L3 larvae, and the anterior fifth of the bodies of adults were studied. Extracts of L2 contained a trypsin-like proteinase exhibiting a molecular weight of 38,000 Da on gelatin-substrate gel electrophoresis. The proteinase showed a pH optimum at 8 and activity against azocoll and keratin. An apparent molecular weight of 25,000 Da was determined for the trypsin-like proteinase of the L3. This enzyme possessed collagenolytic, keratinolytic and slight elastinolytic activity at an optimal pH of 8. Samples of adults contained an aspartyl proteinase with a molecular weight of 90,000 Da. When hemoglobin was used as the substrate, the enzyme displayed optimal activity at pH 5. It was concluded that the proteinases of the larval stages are penetration enzymes, whereas that of the adult stage is a digestive enzyme.

Comparative investigations of the morphology and chemical composition of the eggshells of Acanthocephala. II. Palaeacanthocephala

Eggshells of the palaeacanthocephalans Acanthocephalus anguillae, Pomphorhynchus laevis and Polymorphus minutus were investigated for their fine structure as well as their chemical composition. The acanthor larvae are surrounded by four eggshells (E1-E4) separated by interstices (G1-G4). Immature eggs do not exhibit the complete set of eggshells. The chemical composition of the outermost, thin eggshell (E1) remains unknown. E2 is supplied by outer filaments of different strength; it contains keratin, which was localized electron microscopically using anti-keratin. In P. laevis and P. minutus, E3 seems to contain glycoproteins, which could not be visualized in this eggshell of A. anguillae. The innermost eggshell (E4) uniformly contains chitin. The electron-lucent interstices of the eggs of P. laevis and P. minutus are rich in polysaccharides and/or proteoglycans, whereas those of A. anguillae contain low amounts of such substances. The differences observed in the abundance of carbohydrates are discussed with respect to the life cycles of the three acanthocephalans.

Comparative investigations of the morphology and chemical composition of the eggshells of Acanthocephala. III. Eoacanthocephala

Eggshells of the eoacanthocephalans Neoechinorhynchus rutili (Neoechinorhynchidae) and Paratenuisentis ambiguus (Tenuisentidae) were investigated for their fine structure and their chemical composition. The acanthor larvae of P. ambiguus are surrounded by four eggshells (E1-E4) separated by electron-lucent interstices (G1-G4). This resembles the stratification of the eggshells of archiacanthocephalans and palaeacanthocephalans. However, an additional outer envelope (E0) exists in N. rutili. In mature eggs of this species, the broad interstice between E0 and E1 is densely packed with polysaccharides, but the other interstices also showed an intense Thiéry label. In both species, E2 along with its outer protuberances contains keratin, as does E2 in archiacanthocephalans and palaecanthocephalans, whereas E4 does not contain chitin, which contrasts with findings in the eggs of the two other classes of acanthocephalans. The results are discussed with respect to the classification of the Acanthocephala and to their transmission to the intermediate hosts.