Fine-Structural Changes in a Lepidopteran Nervous System During Metamorphosis

The fine structure of the metamorphosing abdominal nerve cord of Manduca sexta has been studied. In fifth instar larvae, the connectives are ensheathed by a complex, thickened neural lamella. The underlying perineurium at this stage consists of 2 layers. The outer layer consists of interdigitating type I cells which are attached to the overlying neural lamella by hemidesmosomes, and to each other by occasional gap and tight junctions which persist throughout development. They are attached by desmosomes to a thin underlying type II cell layer, which is joined by gap and tight junctions and which has desmosomal attachments with the underlying glial membranes. The larval axons are surrounded by multiple glial wrappings containing bundles of microtubules. During the first week after larval-pupal ecdysis, the neural lamella degenerates and is phagocytosed by invading haemocytes. The underlying perineurial I cells gradually become hypertrophied and vacuolated. At the same time the type II layer, which does not increase in size, appears to be composed of either one or two cells which form a continuous ‘bracelet’ around each connective. The cellular bracelet is joined at one or two places by extensive gap, tight and septate junctions, and gap junctions are also seen along its perineurial I and glial borders. The underlying axons are embedded in vast amounts of glial cytoplasm containing relatively few microtubules. During the second week after larval-pupal ecdysis, the neural lamella is reformed and the perineurium flattens again. Type I and II cell junctions remain as described in earlier stages. Before adult emergence, the axons are again wrapped by glial cells rich in microtubules.

Studies on the life history of Echinostoma ivaniosi n. sp

The life cycle ofEchinostoma ivaniosin.sp., found in the rectum of domestic fowl (Gallus gallus domesticus) has been worked out in detail. The eggs hatch in 7–8 days in tap water at room temperature (24-28°C). Body of the miracidium covered with 18 epidermal plates arranged in four tiers of 6, 6, 4, 2 from the anterior to the posterior end. Miracidia develop into sporocysts in the snails,Lymnaea luteola f typica.There are two redial generations and the first cercariae are liberated 25–30 days post-infection with miracidia, or a little later. 37 collar spines of the cercaria are arranged in the pattern-5(3+2)+6+15(8+7)+6+5(3+2). Caudal finfold present, cuticle spinose, paraoesophageal gland cells present, penetration glands two pairs and excretory system with 18 pairs of flame cells in triplets. Metacercaria develops into adult in domestic fowl and the eggs are recovered from the faeces of the host, 12–14 days post-infection. The adult is compared with other 37-spined echinostomes whose life cycles are known or which show characteristic differences from the present species and the creation of a new species is justified.

Growth and respiration throughout the life-cycle of Nematospiroides dubius Baylis, 1926 (Nematoda: Heligmosomidae). The free-living stages

The growth of the three free-living stages of N. dubius was measured in terms of dry and fresh weight. Changes in body water content during moulting were demonstrated by variations in dry weight when expressed as a percentage of fresh weight. The respiration rate of the larvae increased until they became infective, after which time it decreased until five days later no oxygen consumption could be recorded. The inability of all larval stages to withstand anaerobic conditions indicated that their metabolism was essentially aerobic. The relationship between body size and metabolic rate was established for each stage and its significance in relation to the life-cycle discussed.

Biometrical effects of the inversion polymorphism of Kiefferulus intertinctus (Skuse)

The Lonsdale, Barwon, and Corio inversions of K. intertinctus produce biometrical effects in larvae. The Lo, Ba, and Co sequences all increase the length of the ventral tubules in both male and female larvae. This effect may help in understanding the basis of the non-random association between the Lonsdale and Barwon inversions. La and Ba, whose occurrence together is advantageous, are more common in warmer regions where the oxygen content of the water is low. Larger ventral tubules provide an increased area for respiratory exchange.

Morphological descriptions of the egg and larval stages of Trichuris suis Schrank, 1788

The egg and larval stages of Trichuris suis can be briefly characterized as follows: The egg: barrel shaped, possesses a thick shell consisting of three thick outer layers and an inner thin vitelline membrane, is operculate at each end and is unsegmented and unfertilized when freshly deposited. L. 1 within the egg: presence of an oral spear, a poorly denned oesophagus and an intestinal tract consisting of undifferentiated granulated material. L. 1 within the host: initial differentiation of an oesophagus, cell body, intestine and rectum. L. 2: further differentiation of the body organs and the appearance of the rudiments of the reproductive system. L. 3: initial development of reproductive system and development of a cloaca in the male thus distinguishing the sexes. L. 4: differentiation of reproductive system into vagina, uterus, oviduct and ovary in the female, and testis, vas deferens, ejaculatory duct, spicule and spicular muscle, sheath and tube in the male. L. 5 or adult stage: completed development of the sexual organs including formation of the vulval orifice and eggs in the female and seminal vesicle in the male.

Observations on migratory behaviour and development of Baylisascaris tasmaniensis

The development of larvae of Baylisascaris tasmaniensis to the adult stage is described, using laboratory mice and the Tasmanian devil as experimental hosts. The first moult occurred in the egg, the second moult occurred in mouse tissues at 1–2 weeks after ingestion of embryonated eggs. Larvae migrated to liver, lungs, brain, eyes and kidneys, but most larvae were found in the mesenteric tissues and wall of the intestine. Larvae grew to a length of 0·5–1·0 mm in mice, although some attained a length of 2 mm or more in infections over a year in duration.

The Role of the Epidermal Cells in Moulding the Surface Pattern of the Cuticle in Rhodnius (Hemiptera)

The patterns of folding in the epicuticle of Rhodnius result from mechanical forces directed by the epidermal cells and not from the action of physical forces arising spontaneously in the secreted substance. This conclusion is supported by observations on the cuticular folds over the abdomen of the larva and adult; on the formation of the plaques and the tactile setae arising from them; and on the taenidial folds in the tracheae.

At the time of formation of the outer epicuticle the boundaries of the definitive epidermal cells are clearly defined by adhesion zones. The total surface area of the cuticle is thus the sum of contributions determined by the individual cells.

The area of outer epicuticle deposited is greater than that of the apical plane of the cell. The cell surface is thrown into folds over which the epicuticle is laid down. But before the inner layers are deposited the cuticle is moulded by mechanical forces controlled by the epidermal cells.

Microtubules and fibre bundles appear to play an active part, notably in the outgrowth of setae, and perhaps in the raising of the initial folds in the abdominal surface and in the tracheae. The taenidial folds in the tracheae arise mainly at the sites of the folds in the preceding instar.

Cellular movements or changes in shape lead to aggregation of epidermal cells to form the ‘stellate pattern’ of the larval abdomen and the transverse ‘ripple pattern’ of the adult.

Distension of intercellular and intracellular vacuoles controls the moulding of the definitive stars in the larval cuticle, the transverse ridges in the adult, the smoothing of the cuticle over the plaques, the raising of the plaques in dome-like form above the rest of the cuticle, the expansion of the setae and the shaping of the taenidial folds in the tracheae.

The basement membrane provides a resistant substrate for these mechanical forces.

The effect of various periods of infection with the nematode Haemonchus contortus on the development of the nematode Nematodirus battus

A comparison was made between 14-day-old populations of Nematodirus battus from single infections and from those which developed concurrently with Haemonchus contortus from the day of infection and from days 5 and 10 after infection. The numbers of Nematodirus fell with decreasing length of exposure to Haemonchus and were negatively correlated with the numbers of Haemonchus. The percentage of the populations of Nematodirus in the adult stage and the mean worm lengths fell with increasing length of development with Haemonchus, the lowest values being found in infections which developed concurrently with the abomasal worm for the full 14 days (days 0–14). Mean Nematodirus worm lengths were negatively related to abomasal pH and Na+ levels in populations which were concurrent with Haemonchus for the last 9 days (days 5–14) and for the full 14 days of development studied. Nematodirus egg capacity also fell with exposure to Haemonchus, but was lower in the worm populations exposed for the last 9 days than in those exposed for 14 days. Egg capacity was related to abomasal electrolyte levels in populations which had developed concurrently with Haemonchus for the last 9 days and for the full 14 days. Significant differences between the population parameters of Nematodirus from the proximal and middle third of the small intestine were only found in the single Nematodirus infections and in those which were concurrent with Haemonchus for the last 4 days (days 10–14). The differences in the populations of Nematodirus were related to the probable changes in alimentary conditions affected by the different periods of concurrent infections of Haemonchus. It was suggested that the alimentary changes may have caused the loss of adult Nematodirus and have influenced the growth, development and reproductive capacity of the intestinal worm by acting upon the fourthand fifth-stage larvae.

Migration and growth of Ancylostoma ceylanicum in golden hamsters Mesocricetus auratus

The route of migration and development of Ancylostoma ceylanicum, when given orally, has been described for the first time in hamsters. A predominant feature of the migration is the absence of any lung journey. This is unlike A. caninum, A. duodenale and A, brazilicnse when larvae are similarly given to an abnormal host. The larvae of A. ceylanicum apparently had no submucosal migration

Larvae of the British Metastriata (Ixodoidea: Ixodidae)

Detailed descriptions are given of the larvae of the three species of British metastriatan ticks, with particular reference to the arrangement and dimensions of setae.

Life cycle of a new echinostome from Egypt, Echinostoma liei sp.nov. (Trematoda: Echinostomatidae)

A 37-spined Egyptian echinostome, Echinostoma liei sp.nov., is described in adult and larval stages. The parasite develops readily in the laboratory in chicks and ducklings, hamsters and rats. Its natural final host in or near irrigation ditches of the Nile delta involves the roof rat, Egyptian giant shrew and aquatic bird hosts. Developmental forms are described from infection of the NIH strain of Biomphalaria glabrata in the laboratory. B. alexandrina, is infected in the normal habitat in Egypt and contains both developmental stages in the heart or aorta and the hepatopancreas, and metacercariae encyst in the pericardium and kidney. E. liei sp.nov. is one of six very similar species characterized by 37 collar spines with a pattern of (3 + 2) corner spines in each lappet, six laterals on each side, and 15 dorsals in alternating rows; two pairs of dorsoventral and one small pair of ventro-lateral finfolds on the cercarial tail; and rodlike cystogenous material filling the cercarial encystation glands. In addition to distinctive intermediate-host specificity, differentiating characteristics of E. liei cercariae include presence of six sets of three flame cells each per side (total 36), seven oesophageal cells, eight penetration gland outlets on the dorsal lip of the oral sucker, and an absence of paraoesophageal gland cells as determined by intravital dyes. Significance of these and other cercarial traits is emphasized to aid in defining highly similar, but none the less distinct, sibling species.