Horizontal transfer and finalization of a reliable detection method for the olive fruit fly endosymbiont, Candidatus Erwinia dacicola

BACKGROUND

The olive fly, Bactrocera oleae, is the most important insect pest in olive production, causing economic damage to olive crops worldwide. In addition to extensive research on B. oleae control methods, scientists have devoted much effort in the last century to understanding olive fly endosymbiosis with a bacterium eventually identified as Candidatus Erwinia dacicola. This bacterium plays a relevant role in olive fly fitness. It is vertically transmitted, and it benefits both larvae and adults in wild populations; however, the endosymbiont is not present in lab colonies, probably due to the antibiotics and preservatives required for the preparation of artificial diets. Endosymbiont transfer from wild B. oleae populations to laboratory-reared ones allows olive fly mass-rearing, thus producing more competitive flies for future Sterile Insect Technique (SIT) applications.

RESULTS

We tested the hypothesis that Ca. E. dacicola might be transmitted from wild, naturally symbiotic adults to laboratory-reared flies. Several trials have been performed with different contamination sources of Ca. E. dacicola, such as ripe olives and gelled water contaminated by wild flies, wax domes containing eggs laid by wild females, cages dirtied by faeces dropped by wild flies and matings between lab and wild adults. PCR-DGGE, performed with the primer set 63F-GC/518R, demonstrated that the transfer of the endosymbiont from wild flies to lab-reared ones occurred only in the case of cohabitation.

CONCLUSIONS

Cohabitation of symbiotic wild flies and non-symbiotic lab flies allows the transfer of Ca. E. dacicola through adults. Moreover, PCR-DGGE performed with the primer set 63F-GC/518R was shown to be a consistent method for screening Ca. E. dacicola, also showing the potential to distinguish between the two haplotypes (htA and htB). This study represents the first successful attempt at horizontal transfer of Ca. E. dacicola and the first step in acquiring a better understanding of the endosymbiont physiology and its relationship with the olive fly. Our research also represents a starting point for the development of a laboratory symbiotic olive fly colony, improving perspectives for future applications of the Sterile Insect Technique.

Effects of a Covert Infection with Phthorimaea operculella granulovirus in Insect Populations of Phthorimaea operculella

Virus infections of insects can easily stay undetected, neither showing typical signs of a disease, nor being lethal. Such a stable and most of the time covert infection with Phthorimaea operculella granulovirus (PhopGV) was detected in a Phthorimaea operculella laboratory colony, which originated from Italy (Phop-IT). This covert virus (named PhopGV-R) was isolated, purified and characterized at the genetic level by full genome sequencing. Furthermore, the insect colony Phop-IT was used to study the crowding effect, double infection with other PhopGV isolates (CR3 and GR1), and co-infection exclusion. An infection with a second homologous virus (PhopGV-CR3) activated the covert virus, while a co-infection with another virus isolate (PhopGV-GR1) led to its suppression. This study shows that stable virus infections can be common for insect populations and have an impact on population dynamics because they can suppress or enable co-infection with another virus isolate of the same species.

In vitro feeding of Hyalomma lusitanicum ticks on artificial membranes

In vitro feeding of ticks (Acari: Ixodidae) is an important means to study the biology of ticks and their vectorial capacity. Here, we have adapted the tick Hyalomma lusitanicum Koch to previously published silicone-based membranes for in vitro feeding. For comparison purposes data on pre-oviposition, oviposition and hatching from females engorged on animals were used. A total of 68 engorged females out of 169 were obtained; feeding duration and feeding behaviour were similar to that of ticks on live host animals, although the final weight achieved for membrane-fed ticks was lower than that of their animal-fed counterparts. Comparison of the time taken for egg production and hatching showed that pre-oviposition was faster for membrane-fed ticks (16 days) than for animal-fed ticks (36 days), whereas the duration of oviposition-hatching was the same for the two feeding methods (34 days). We also observed that seasonality has an influence on tick feeding success: the conditions in Spring/Summer accelerated the tick life cycle. It is concluded that relatively large numbers of homogeneous laboratory-raised Hyalomma ticks can be produced without feeding them on experimental animals.

Developmental Expression of Ecdysone-Related Genes Associated With Metamorphic Changes During Midgut Remodeling of Silkworm Bombyx mori (Lepidoptera:Bombycidae)

Steroid hormone 20-hydroxyecdysone is known as the systemic regulators of insect cells; however, how to impact the fate and function of mature and stem cells is unclear. For the first time, we report ecdysone regulatory cascades in both mature midgut cell and stem cell fractions related to developmental events by using histological, immunohistochemical, biochemical and gene expression analysis methods. Ecdysone receptor-B1 (EcR-B1) and ultraspiracle 1 (USP-1) mRNAs were detected mainly in mature cells during programmed cell death (PCD). Lowered E75A and probably BR-C Z4 in mature cells appear to provide a signal to the initiation of PCD. E74B, E75B and BR-C Z2 seem to be early response genes which are involved in preparatory phase of cell death. It is likely that βFTZ-F1, E74A and BR-C Z1 are probably associated with execution of death. EcR-A and USP2 mRNAs were found in stem cells during remodeling processes but EcR-B1, USP1 and E74B genes imply an important role during initial phase of metamorphic events in stem cells. BHR3 mRNAs were determined abundantly in stem cells suggesting its primary role in differentiation. All of these results showed the determination the cell fate in Bombyx mori (Linnaeus) midgut depends on type of ecdysone receptor isoforms and ecdysone-related transcription factors.

A comparison of adult body size between captive and wild vervet monkeys (Chlorocebus aethiops sabaeus) on the island of St. Kitts

Weight and 34 morphological measurements were obtained from 103 vervet monkeys living either in the wild or in captive colonies derived from the wild populations on the island of St. Kitts in the Eastern Caribbean. All measures were taken during the same week, eliminating bias that might result from changing seasonal environmental conditions. Vervets on St. Kitts are all descended from a small number of individuals brought to the island approximately 400 years ago from West Africa, thus eliminating bias that might result from subspecific size differences. We conducted a principal components analysis (PCA) and compared individual traits between captive and wild adult animals. Morphological measures such as body, arm, and leg length did not differ significantly between animals living in the wild and animals in captivity. Weight and measures indicating condition-including body mass index (BMI), chest, thigh, and upper arm girth were all higher for animals living in captivity. More consistent available food is probably the cause of differences in measures reflecting condition.

Captive Care, Raising, and Breeding of the Veiled Chameleon (Chamaeleo calyptratus)

Squamate reptiles comprise approximately one-third of all living amniotes. In most of these species, it is difficult to study gastrulation and neurulation because the embryos are at a late stage of development at the time of oviposition. This is not the case, however, in veiled chameleons (Chamaeleo calyptratus), which are increasingly being used as a model organism to study these and other developmental and evolutionary phenomena. Originating from the Arabian Peninsula, veiled chameleons are arboreal specialists that possess extensive morphological specializations for climbing. They naturally inhabit semitropical habitats, but they also have an almost 30-yr history of being bred in captivity. Veiled chameleons breed readily and do not require a period of cooling to induce the reproductive cycle, and females can produce ∼45-90 eggs multiple times per year. Thus, compared with other reptiles, relatively few animals are needed to maintain a productive breeding colony. Herein, we present the conditions, equipment, and techniques required for proper husbandry and breeding of veiled chameleons within a laboratory environment.

Influence of resource levels, organic compounds and laboratory colonization on interspecific competition between the Asian tiger mosquito Aedes albopictus (Stegomyia albopicta) and the southern house mosquito Culex quinquefasciatus

The mosquitoes Aedes albopictus (Stegomyia albopicta) (Skuse) and Culex quinquefasciatus (Say) (Diptera: Culicidae) are common inhabitants of tyres and other artificial containers, which constitute important peridomestic mosquito breeding habitats. We tested the hypotheses that interspecific resource competition between the larvae of these species is asymmetrical, that the concentration of chemicals associated with decomposing detritus affects the competitive outcomes of these species, and that wild and colonized strains of Cx. quinquefasciatus are affected differently by competition with Ae. albopictus. We conducted two laboratory competition experiments wherein we measured survivorship and estimated population growth (λ') in both species under multiple mixed-species densities. Under varying resource levels, competition was asymmetrical: Ae. albopictus caused competitive reductions or exclusions of Cx. quinquefasciatus under conditions of limited resources. In a second experiment, which used both wild and colonized strains of Cx. quinquefasciatus, organic chemical compounds associated with decomposing detritus did not affect the competitive outcome. The colonized strain of Cx. quinquefasciatus had greater survivorship and adult mass, and faster development times than the wild strain, but both strains were similarly affected by competition with Ae. albopictus. Competition between these species may have important consequences for vector population dynamics, especially in areas in which tyres and artificial containers constitute the majority of mosquito breeding habitats.

Introducing improvements in the mass rearing of the housefly: biological, morphometric and genetic characterization of laboratory strains

Understanding the biology of the housefly (Musca domestica L.) is crucial for the development of mass-rearing protocols in order to use this insect as a degradation agent for livestock waste. In this study, the biological and genetic differences between different laboratory strains of M. domestica were analysed. Additionally, hybrids were obtained by mixing the strains and their biological parameters were also measured. The three strains of M. domestica presented differences in their biological and morphological parameters, the main differences were: size, egg production and developmental time. The strain A (specimens from Central Europe) had the best qualities to be used in mass-rearing conditions: it produced the largest quantities of eggs (5.77±0.38 eggs per female per day), the individuals were larger (12.62±0.22 mg) and its developmental time was shorter (15.22±0.21 days). However, the strain C (specimens from SW Europe) produced the fewest eggs (3.15±0.42 eggs per female per day) and needed 18.16±0.49 days to develop from larva to adult, whilst the females from strain B (from South America) produced 4.25±0.47 eggs per day and needed 17.11±0.36 days to complete its development. Genetic analysis of the original laboratory strains showed four different mtDNA cytochrome c oxidase subunit I haplotypes. Statistical parsimony network analysis showed that the SW Europe and South-American strains shared haplotypes, whereas the Central Europe strain did not. Upon hybridizing the strains, variations in egg production and in developmental time were observed in between hybrids and pure strains, and when mixing Central European and South-American strains only males were obtained.

Phenotypic variation of the housefly, Musca domestica: amounts and patterns of wing shape asymmetry in wild populations and laboratory colonies

Musca domestica L. (Diptera: Muscidae) is a vector of a range variety of pathogens infecting humans and animals. During a year, housefly experiences serial population bottlenecks resulted in reduction of genetic diversity. Population structure has also been subjected to different selection regimes created by insect control programs and pest management. Both environmental and genetic disturbances can affect developmental stability, which is often reflected in morphological traits as asymmetry. Since developmental stability is of great adaptive importance, the aim of this study was to examine fluctuating asymmetry (FA), as a measure of developmental instability, in both wild populations and laboratory colonies of M. domestica. The amount and pattern of wing shape FA was compared among samples within each of two groups (laboratory and wild) and between groups. Firstly, the amount of FA does not differ significantly among samples within the group and neither does it differ between groups. Regarding the mean shape of FA, contrary to non-significant difference within the wild population group and among some colonies, the significant difference between groups was found. These results suggest that the laboratory colonies and wild samples differ in buffering mechanisms to perturbations during development. Hence, inbreeding and stochastic processes, mechanisms dominating in the laboratory-bred samples contributed to significant changes in FA of wing shape. Secondly, general patterns of left-right displacements of landmarks across both studied sample groups are consistent. Observed consistent direction of FA implies high degrees of wing integration. Thus, our findings shed light on developmental buffering processes important for population persistence in the environmental change and genetic stress influence on M. domestica.

Adolescent sleep patterns in humans and laboratory animals

This article is part of a Special Issue "Puberty and Adolescence". One of the defining characteristics of adolescence in humans is a large shift in the timing and structure of sleep. Some of these changes are easily observable at the behavioral level, such as a shift in sleep patterns from a relatively morning to a relatively evening chronotype. However, there are equally large changes in the underlying architecture of sleep, including a >60% decrease in slow brain wave activity, which may reflect cortical pruning. In this review we examine the developmental forces driving adolescent sleep patterns using a cross-species comparison. We find that behavioral and physiological sleep parameters change during adolescence in non-human mammalian species, ranging from primates to rodents, in a manner that is often hormone-dependent. However, the overt appearance of these changes is species-specific, with polyphasic sleepers, such as rodents, showing a phase-advance in sleep timing and consolidation of daily sleep/wake rhythms. Using the classic two-process model of sleep regulation, we demonstrate via a series of simulations that many of the species-specific characteristics of adolescent sleep patterns can be explained by a universal decrease in the build-up and dissipation of sleep pressure. Moreover, and counterintuitively, we find that these changes do not necessitate a large decrease in overall sleep need, fitting the adolescent sleep literature. We compare these results to our previous review detailing evidence for adolescent changes in the regulation of sleep by the circadian timekeeping system (Hagenauer and Lee, 2012), and suggest that both processes may be responsible for adolescent sleep patterns.

Reproduction of Omalonyx matheroni (Gastropoda: Succineidae) under laboratory conditions

The life histories of succineids have received relatively little attention. To evaluate life history characteristics of Omalonyx matheroni, we studied a Brazilian population (Reserva Particular do Patrimônio Natural Feliciano Miguel Abdala, in Caratinga, Minas Gerais, Brazil) under laboratory conditions. The aims of the present study were (1) to describe in detail an appropriate rearing method; (2) to investigate the effects of different temperature and photoperiod conditions; and (3) to assess the effects of self and cross-fertilization on the reproductive biology of these mollusks. We studied the oviposition site, the time to sexual maturity and the influences of photoperiod and temperature on reproductive parameters of O. matheroni reared under laboratory conditions. We tested three combinations of temperature and photoperiod, designated A, B and C (A: 25degreeC, 24 hours of light; B: environmental conditions of temperature and photoperiod, characterized as follows: average maximum temperature=27.1 degreeC, average minimum temperature=18.3 degreeC, average day length=12.06 hours; and C: 25 degreeC, zero hours of light) and two rearing densities (I: isolated and G: grouped) on reproductive parameters (number of eggs per egg mass, number of unviable eggs per mass, egg mass incubation period, and duration of the hatching period). A total of 186 individuals and 565 egg masses were studied. Data were analyzed by Student's t-test, two-way ANOVA and Chi-Square test. Eight generations were produced (March/2004-March/2006), from 35 field specimens, 91% of 3 197 eggs hatched. The time to sexual maturity was approximately three months for individuals reared in groups or in isolation (Student's t-test: t=1.41, df=31, p=0.16); however, they differed significantly in weight (Student's t-test: t=3.6, df=31, p<0.001). Regarding the influences of temperature and photoperiod on reproductive parameters, under natural environmental conditions, individuals produced a greater number of eggs per mass (ANOVA: F2573,=84.15, p<0.001), with a longer incubation period (ANOVA: F2559=170.05, p<0.001). The extreme photoperiod conditions of 24 hours of light or zero hours of light likely imposed stress and could be related to the significant reductions in the number of eggs per mass, and egg incubation period as well as the increased synchrony in egg hatching. No correlations were observed between the number of unviable eggs per mass and the temperature, photoperiod (ANOVA: F2573=0.87, p=0.92) or rearing density (ANOVA: F1 .573=0.21, p=0.64). Individuals reared in isolation under natural conditions produced more eggs per mass and did not presented any disadvantage with respect to the variables analyzed as compared to the animals reared in groups. These results indicate that O. matheroni can successfully reproduce by selfing.

Growing male rats in individually ventilated and open-top cages

During the past few decades, the development and use of individually ventilated cages (IVC), which are now commercially available for housing laboratory mice and rats, have increased. Because limited information is available regarding the influence of caging systems on the growth of rats, the present study assessed body weight and food and water consumption in growing male rats that were housed in IVC and open-top cages (OTC). We allocated 21-d-old male Wistar outbred rats (HsdOla:WI; n = 24) into 2 groups, which then were housed in pairs in IVC (n = 12) and OTC (n = 12). After an 8-d acclimatization period, body weight and food and water consumption were assessed every 3 d until the rats were 94 d old. There were no significant differences between the body weights of rats housed in IVC compared with OTC over the 65-d observation period. Food and water consumption were greater in rats housed in OTC compared with IVC, becoming significantly different when the rats were 50 and 53 d old, respectively. In conclusion, IVC and OTC housing conditions influenced food and water intakes but not body weight in growing male rats. Further research is needed to clarify the exact basis for these changes in food and water consumption.

A comparative study of different diets to optimize cultivation of Hyalella azteca in the laboratory

The aim of this study was to assess the influence of four diets on the laboratory cultivation of H. azteca, seeking to improve production of young specimens through reduced mortality and better growth and number of offspring per couple. The best diet was composed of a mixture of diluted commercial fish food, diluted yeast and primrose oil, associated with fish food flakes containing spirulina. With this diet the maximum mortality was 25 percent (at the end of 28 days), the average number of offspring/couple was 11.4 ± 2.8 (at the end of twelve days) and the peak weight and length of the males (at the end of 40 days) were 0.930 μg and 5.26 ± 1.1mm, respectively.

The value of juvenile animal studies: a pediatric clinical perspective

With the emphasis of US American and European legislators on consideration of children in the drug development process regulatory authorities ask increasingly for additional non-clinical data to elucidate the safety of a given drug in development in future pediatric use. Juvenile animal studies are increasingly requested. These requests should never be tick box requests. Companies, academic toxicologists, clinicians, and regulatory authorities need a dialogue to differentiate between the perceived need to do "something" and the request for studies that have clinically meaningful results.

Juvenile animal studies in the development of pediatric medicines: experience from European medicines and pediatric investigation plans

INTRODUCTION

The need for early consideration of pediatric investigation plans (PIP) to support an indication in pediatric population has led to an increased focus on the relevance of nonclinical studies in juvenile animals (JAS). The usefulness of JAS is not yet established and a criterion for request is still a learning process.

OBJECTIVE

This article compares data from JAS in all medicines approved by European centralized procedure before Pediatric Regulation (1995-2005) and data from JAS in the nonclinical information on all approved PIP (2007-2009).

RESULTS

Of the 226 substances licensed by centralized procedure in 10 years, 31.9% were considered for children and 31 JAS were described in 9.7%. Since 2007, of the 205 PIP decisions, 50 PIP (24.3%) have 87 JAS planned or requested. The mean number of JAS in each medicine or PIP, increased from 1.4 to 1.7 between the two periods and the juvenile rat remained as the prevalent species.

CONCLUSIONS

Results demonstrate that JAS planned/performed in EU environment has significantly increased.

Optimization of breeding output for larval stage of Anopheles gambiae (Diptera: Culicidae): prospects for the creation and maintenance of laboratory colony from wild isolates

Domesticating anopheline species from wild isolates provides an important laboratory tool but requires detailed knowledge of their natural biology and ecology, especially the natural breeding habitats of immature stages. The aim of this study was to determine the optimal values of some parameters of Anopheles gambiae larval development, so as to design a standard rearing protocol of highland isolates, which would ensure: the biggest fourth instars, the highest pupae productivity, the shortest duration of the larval stage and the best synchronization of pupation. The density of larvae, the size of breeding water and the quantity of food supplied were tested for their effect on larval growth. Moreover, three cheap foodstuffs were selected and tested for their capability to improve the breeding yield versus TetraMin® as the standard control. The larval density was a very sensitive parameter. Its optimal value, which was found to be ≈1 cm-2 surface area, yielded a daily pupation peak of 38.7% on day 8 post-oviposition, and a global pupae productivity of 78.7% over a duration range of three days. Anopheles gambiae's larval growth, survival and developmental synchronization were density-dependent, and this species responded to overcrowding by producing smaller fourth instars and fewer pupae, over elongated immature lifetime and duration range of pupae occurrence, as a consequence of intraspecific competition. While shallow breeding waters (<3 cm) produced a higher number of pupae than deeper ones, no effect of the breeding habitat's absolute surface area on larval development was observed. Increasing the daily food supply improved the pupae productivity but also boosted the water pollution level (which was assessed by the biological oxygen demand (BOD) and the chemical oxygen demand (COD)) up to a limit depending on the food quality, above which a rapid increase in larval mortality was recorded. The food quality that could substitute the manufactured baby fish food was obtained with weighed mixture of 1 wheat+1 shrimp+2 fish. On establishing an anopheline mosquito colony in the laboratory, special care should be taken to design and maintain the appropriate optimal values of larval density, water depth, daily diet quantity and nutritional quality.

Juvenile animal testing in drug development--is it useful?

In pharmaceutical drug development, there has been increased interest in the need to perform juvenile animal studies to support the safety of use of new medicines in the pediatric population. Although such studies are not new, the increased interest has been "formalized" in recent regulatory guidelines. As a result, companies are now performing many more studies in juvenile animals, even when there is a lack of robust knowledge of cross-species functional and kinetic differences among juveniles that means extrapolation of any toxicology study finding to an immature human may not be easy or even relevant, especially if performed in the wrong species at the wrong time. It will be shown by presentation of some basic considerations needed in order to perform such testing, that juvenile animal studies are indeed feasible. However, it will also be highlighted that (based on available knowledge) there are currently not enough clear-cut examples to answer the question of whether juvenile animal toxicology studies to support pediatric development (by affecting the performance or design of a pediatric clinical trial or identifying a potential different-from-adult safety risk in clinical use) are truly useful or necessary.

Method of feed presentation affects the growth of Mongolian gerbils (Meriones unguiculatus)

The Animal Welfare Regulations, which define legal requirements for the care and use of gerbils in research and testing, and the Guide for the Care and Use of Laboratory Animals describe feeding practices for several species of rodents but not Mongolian gerbils (Meriones unguiculatus). To investigate whether the method of feed presentation affected reproduction and growth of gerbils, we compared the reproductive performance and rate of growth of gerbils fed on the cage floor, by hopper (J-feeder), or by wire-bar cage lid. Reproductive parameters of 10 breeding pairs for each method of feeding were followed for 63 d and did not differ between methods. To investigate the effect of feeding method on weight gain in juvenile gerbils, groups of 80 male and 80 female weanling gerbils per feeding method were fed for 5 consecutive weeks after weaning and weighed weekly. Gerbils fed on the cage floor and by means of J-feeders were significantly heavier than were those fed by using a wire-bar top. Our findings indicate that feeding gerbils by using J-feeders or on the cage floor are both acceptable practices.

The short-tailed fruit bat Carollia perspicillata: a model for studies in reproduction and development

Carollia perspicillata has proven to be a valuable laboratory model for studies in reproduction and development. We present here an overview of the care and handling of Carollia in captivity and discuss some pertinent studies in reproductive biology. Finally, we describe various features of the genome and some of the genetic manipulations that are now possible.

Artificial diets for larvae of Anarsia lineatella Zeller (Lepidoptera: Gelechiidae)

Maintenance of an insect colony under laboratory conditions is prerequisite for its further study. However, numerous artificial diet formulas, such as dietary replacements or supplements, influence species growth and survivorship and display difficulties in utilization in laboratory settings. In this work, successful rearing in the laboratory is reported for the peach twig borer A. lineatella on artificial diet. The diet contains dry pindo beans (380 g), brewer's yeast (64 g) agar 31 g, 1360 ml distilled water and preservatives. It is a modification of an artificial rearing medium proposed for the development of the Tortricid Cydia pomonella. Larval survivorship, when developed on the above diet, is significantly higher (-90%) when compared to peach fruits (-60%) and to other diets that were initially tested (5-35%). Diet had no effect on larval developmental time when compared to fruits (27.1 +/- 0.4 and 27.2 +/- 0.5 days, respectively, at 25 degrees C and 65 +/- 5% RH). Light presence of 16:8h L:D did not appear to be a critical factor for a successful rearing of A. lineatella larvae in the laboratory. Type of diet had a significant effect on male (d.f. = 4,103, F = 18.562, P < 0.05) and female (d.f. = 4,91, F = 14.990, P < 0.05) pupal weights. Pupal weights, when they developed as larvae on the proposed 'pindo-bean' diet, ranged from 7.7 +/- 0.3-8.2 +/- 0.2 mg. First-instar larvae exhibited lower survivorship during development, regardless of rearing medium. Sex ratio, for individual larval rearing, was in all cases close to 1:1 regardless of tested rearing medium. More than five generations of A. lineatella were reared under constant conditions without observable adverse effects on development.

Survivorship characteristics of the mosquito Aedes caspius adults from southern France under laboratory conditions

The survivorship characteristics of two populations of Aedes caspius (Pallas) (Diptera: Culicidae) were compared in the laboratory. One population was sourced from Mourgues, where larvicides have been used continuously for approximately 40 years, and the other from Pont de Gau, where there has been no consistent mosquito control. The aims of the study were to ascertain the basic life history profiles of adults and to determine whether continuous larviciding affects inherent adult survivorship. Life tables were constructed to calculate the following life expectancy parameters: mean lifetime (tau(ad)); maximum lifetime (tau(max)), and daily survival rate (p(ad)). All three parameters were higher for females than for males (paired t-test, P < or = 0.001); male mean lifetime, maximum lifetime and daily survival rate were 4.95 +/- 0.94 days, 20.50 +/- 6.66 days and 0.79 +/- 0.05, respectively; female values were 14.74 +/- 3.68 days, 49.69 +/- 16.55 days and 0.93 +/- 0.02, respectively. No differences were found between the two populations, and no correlations were found between initial adult densities and their respective survival rates. The survivorship curves for Ae. caspius were type IV for males (mortality rates higher for young adults) and type III for females (mortality rates constant).

Description of the immature stages and redescription of the female of Ixodes schulzei Aragão & Fonseca, 1951 (Acari: Ixodidae), an endemic tick species of Brazil

Ixodes schulzei Aragão & Fonseca, 1951 is a tick endemic to Brazil, where nine species of Ixodes Latreille, 1796 are currently known to occur. Larvae, nymphs and females of I. schulzei were obtained from a laboratory colony originating from an engorged female collected on a free-living water rat Nectomys squamipes from the Santa Branca municipality, São Paulo State. Only female ticks were obtained from engorged nymphs. Unfed immature and female adult specimens were measured and the descriptions were based on optical and scanning electron microscopy, as were drawings of some features of the larva. Both immature stages present the very long palpi and basis capituli, and the female has large, contiguous porose areas. However, the basis capituli is triangular, with a slight central elevation in the larva and nymph, whereas in the female this area is depressed. The I. schulzei types deposited at the FIOCRUZ (Instituto Oswaldo Cruz) were also examined, as was other material from collections, such as the IBSP (Coleção Acarológica do Instituto Butantan), CNC-FMVZ/USP (Coleção Nacional de Carrapatos da Faculdade de Medicina Veterinária e Zootecnia da USP) and USNTC (United States National Tick Collection). In addition, the relationship between I. schulzei and other immature neotropical species of Ixodes is discussed.

Field and laboratory comparison of hatch rates in Aedes albopictus (Skuse)

Laboratory experiments attempting to elicit a response based on a natural condition rely on the assumption that the laboratory treatment accurately mimics field conditions. With Aedes albopictus (Skuse), laboratory experiments analyzing hatch rates assume that the laboratory stimuli resemble those received by the eggs in field conditions. With the use of a colonized strain of Ae. albopictus, an analysis of the hatch rates comparing both field and laboratory settings was conducted. Additionally, hatch rates were compared for mosquitoes exposed to regular, periodic hatch stimulation (as usually seen in laboratory experiments) and random hatch stimulation (as seen in the field). In both experiments, laboratory treatments were not found to differ significantly from the field treatments, indicating that experimental results achieved in the lab are relevant to field situations.

Effect of two types of environmental enrichment for singly housed mice on food intake and weight gain

For animals that cannot be housed socially for scientific reasons, such as rodents on food intake-energy expenditure studies, the provision of environmental enrichment may alleviate stress. However, the influence of environmental enrichment on food intake and energy expenditure is unresolved. The authors tested the effects of two environmental enrichment options on food intake and weight gain in singly housed mice. Their results may be helpful in developing rodent enrichment programs.

Laboratory culture and maintenance of the horseshoe crab (Limulus polyphemus)

Often referred to as a living fossil, the American horseshoe crab, Limulus polyphemus, is one of the most-studied invertebrate animals in the world. It has served as a model in Nobel Prize-winning eye research, and researchers use a component of its blood to detect bacterial contamination in medical devices and drugs. The authors review the conditions necessary for housing these animals in the laboratory.

New records and laboratory-rearing data for Ixodes schulzei (Acari: Ixodidae) in Brazil

Ixodes schulzei Aragão and Fonseca was described from Brazil in 1951 based on female ticks collected on wild rats from the states of Rio de Janeiro and Santa Catarina. Since that time, there have been no additional reports of I. schulzei in the literature. We report two new records of I. schulzei: a female collected on the water rat Nectomys squamipes (Brants) from Minas Gerais State, and another female from this same host species from São Paulo State. This last specimen was engorged and oviposited fertile eggs in the laboratory. Larvae hatched from these eggs were used for subsequent infestations under laboratory conditions, as were nymphs obtained from the engorged larvae. Naive laboratory rats (Rattus norvegicus Berkenhout) and wild mice (Calomys callosus Rengger) were used to feed ticks. C. callosus was a more suitable host than R. norvegicus, as significantly more ticks (P < 0.05) were recovered and successfully molted after feeding on the former host species. A significantly (P < 0.05) greater proportion of larvae detached from C. callosus during daylight (71.3%) when compared with those that detached from R. norvegicus in the same period (54.8%). A total of nine engorged nymphs (one from R. norvegicus, and eight from C. callosus) were recovered in the infestations. All of them successfully molted to adults, which were all females. The male of I. schulzei remains unknown.

Review of growth plate closure compared with age at sexual maturity and lifespan in laboratory animals

Although it is assumed that most mammals experience growth plate closure and cessation of bone growth soon after sexual maturity, bone growth in rats continues throughout their lifespan. The rat was compared to other laboratory animals to assess differences in the duration of bone growth and its relationship to age at sexual maturity and lifespan. We reviewed the literature from 1966 to March 1999 by searching MEDLINE and other databases. Growth closure times and age at sexual maturity were retrieved for the mouse, rabbit, dog, cat, sheep, cow, horse, nonhuman primates, and human. For all species, we calculated the ratios of: 1) age at growth plate closure to lifespan, 2) age at growth plate closure to age at sexual maturity, and 3) age at sexual maturity to average lifespan. The ratio of age at physis closure to the average lifespan was large for the rat (22 to 35) and showed some overlap with that of humans (17 to 25); this ratio was comparatively small in all other nonhuman species (range, 4 to 17). This finding indicates that bone growth continues in the rat for a greater proportion of their lifespan than does that in other species. The ratio of age at physis closure to age at sexual maturity was larger for the rat (5 to 6) than that for other species, indicating that bone growth continues much longer after sexual maturity in rats than in other animals. The ratio of age at sexual maturity to average lifespan was largest for humans and nonhuman primates (13 to 14), indicating the increased time to reach puberty versus that in other species. These differences are important for studies in which animal models are used in research involving bone growth.

Toxicity of Bacillus thuringiensis and B. sphaericus to laboratory populations of Drosophila melanogaster (Diptera: Drosophilidae)

A total of 65 samples, consisting of 8 sample types, collected from the Jordan Valley, were examined for the presence of Bacillus thuringiensis and B. sphaericus and for their toxicity against the larvae of the fruit fly Drosophila melanogaster. The frequency of samples containing toxic aerobic spore-forming bacilli was 12%; of which 21.7% belonged to B. thuringiensis and 17.4% to B. sphaericus. The B. thuringiensis populations consisted of 5 serogroups: thuringiensis (H1), entomocidus (H6), pakistani (H13), autoagglunated, in addition to a new serotype. The B. sphaericus population consisted of 3 serogroups, and belonged to serovars H5, H9, and H13. All B. thuringiensis and B. sphaericus local isolates, in addition to the reference strains B. thuringiensis kuristaki, and B. thuringiensis israelensis, showed high toxicity towards 3(rd) instar larvae of D. melanogaster. The toxic concentrations ranged between 2.0 x 10(6) and 4.4 x 10(7) viable spores ml(-1).

Effects of environmental antiandrogens on reproductive development in experimental animals

Chemicals that act as androgen receptor (AR) agonists and antagonists or inhibit fetal steroidogenesis can induce reproductive malformations in humans and laboratory animals. Several environmental chemicals disrupt development in rats and/or rabbits at fetal concentrations at, or near, exposure levels seen in some segments of the human population. In rats, fetal tissues concentrations of 10-20 p.p.m. of the DDT metabolite, p,p'-DDE, are correlated with reproductive abnormalities in male offspring. These concentrations are similar to those measured in first-trimester human fetal tissues in the late 1960s. The pesticides vinclozolin, procymidone, linuron and DDT are AR antagonists. They reduce male rat anogenital distance, and induce areolas at relatively low dosages. Hypospadias, agenesis of the sex accessory tissues and retained nipples are seen in the middle dosages, while undescended testes and epididymal agenesis are seen in the highest doses. Phthalate esters (PE) inhibit testosterone synthesis during fetal life, but do not appear to be AR antagonists. Prenatal administration of a single low dose of dioxin (50-1,000 ng TCDD/kg) alters the differentiation of androgen-dependent tissues at p.p.t. concentrations, but the mechanism of action likely involves interaction with a hormone-like nuclear transcription factor, the hormone-like receptor AhR, rather than AR. p,p'-DDT and p,p'-DDE, vinclozolin and di-n-butyl phthalate affect reproductive function in rabbits when administered during prenatal and/or neonatal life. Cryptorchidism and carcinoma in situ-like (CIS) testicular lesions were seen in male rabbits treated during development with p,p'-DDT or p,p'-DDE. Extrapolation of effects from rodents to humans would be enhanced if future studies incorporate determination of tissue concentrations of the active metabolites. Knowledge of the tissue concentrations of the active toxicants also would provide an important link to in-vitro studies, which provide more useful mechanistic information when they are executed at relevant concentrations.

The influence of rearing conditions on the physical growth of captive Japanese macaques (Macaca fuscata)

To clarify the influence of rearing conditions on the growth of various body parts of Japanese macaques (Macaca fuscata), two groups reared under different conditions, i.e., a group born and reared in open enclosures (Enclosure group) and another consisting of macaques born and reared in cages (Caged group), were somatometrically analyzed. Somatometric data on 36 measures of various body parts were collected from 77 males and 92 females. Growth in many body parts was smaller in the Caged group than in the Enclosure group. Body parts that exhibited large incremental increases were more sensitive to differences in rearing space at the infantile growth stage in both sexes. Recovery from delayed growth at the pubertal growth stage was found in many body parts. However, the size of some locomotor elements such as the wrist and hand, and ankle and foot strongly reflected limitations of space and changes due to this were irreversible. Females were more sensitive than males to such differences in rearing conditions. We conclude that open enclosures with ample rearing space are necessary for the innate growth of Japanese macaques to occur.

Development and survival of immature Aedes albopictus and Aedes triseriatus (Diptera: Culicidae) in the laboratory: effects of density, food, and competition on response to temperature

Effects of food, density, and heterospecific interactions on temperature-dependent development of Aedes albopictus (Skuse) and Aedes triseriatus (Say) larvae and pupae were described using a degree-day model. Under all conditions, the predicted number of degree-days (DD(T0)) to complete larval development was less, and the threshold temperature (T0) for initiation of larval development was higher for Ae. albopictus than for Ae. triseriatus. The DD(T0) for both species was food and density dependent. However, the per capita food ration appeared to exert a greater influence on the developmental times of Ae. triseriatus immatures, whereas for Ae. albopictus effects of density were not completely eliminated by an increase in the per capita food ration. The presence of heterospecific larvae did not prolong the DD(T0) of either species. At the low food ration, DD(T0) for both species were significantly greater under conspecific conditions. The DD(T0) for Ae. triseriatus increased directly as the proportion of conspecific larvae increased. However, when a higher per capita food ration was provided, conspecific effects on DD(T0) were mitigated. For Ae. albopictus, estimated DD(T0) values for larvae reared in pure culture were significantly higher than when heterospecific larvae were present, regardless of the per capita amount of food provided. Survivorship of immatures was density and food-dependent for both species. Ae. albopictus exhibited higher immature survivorship under all conditions relative to Ae. triseriatus. For both species, survival probabilities were lowest under conditions of high density and low food. Addition of food improved survival for both species. The presence of heterospecific larvae exerted a differential effect on the survivorship response of Ae. albopictus immatures to temperature. Lowest probability of survival for Ae. albopictus was occurred at low temperature when the proportion of heterospecific larvae in containers was the highest. In contrast, at high temperatures, survivorship of immatures improved, but was lowest for pure species cultures. For Ae. triseriatus, survivorship of immatures was consistently lower for pure species cultures regardless of the temperature. Standing crop production of adults of both species was primarily food rather that density-dependent. Under field conditions, Ae. triseriatus were predicted to initiate development sooner and exhibit faster population growth early in the season than Ae. albopictus. However, because of the shorter DD(T0), Ae. albopictus population growth was predicted to surpass that of Ae. triseriatus populations later in the season. Based on optimal DD(T0) values from laboratory experiments, spring emergence dates of Ae. triseriatus females in western North Carolina for 1989 and 1990 were predicted from accumulated degree-days calculated from local air temperature records. Predicted emergence dates were congruent with results of a previous survey for the same locality, indicating that accumulated degree-days can be used to accurately predict the seasonal occurrence of Ae. triseriatus. The utility of the degree-day approach in predicting the phenology of Ae. albopictus remains to be established.

[The effect of the period of egg quiescence on the life cycle of Aedes aegypti (Linnaeus, 1762) (Diptera, Culicidae) under laboratory conditions]

The influence of the period of egg quiescence on the life cycle of Aedes aegypti (Linnaeus, 1762) (Diptera, Culicidae) was studied under laboratory conditions in order to improve the management of vector control. The eggs are known to be the most resistant stages during development, allowing a long survival of the mosquitoes under unfavorable climatic conditions. The experiments were performed in a biological chamber kept at 28 +/- 1 degrees C temperature, with 80 +/- 5% relative humidity and 12 hours of photophase. Data about the influence of different periods of quiescence on eclosion, larval and pupal development and the developmental cycle are presented. We observed a highly significant effect of the period of quiescence on larval eclosion. The period of quiescence had no influence on the duration of larval or pupal incubation. Eggs originating from the same period of quiescence showed significantly different periods of incubation. The larvae emerged in groups defined by the period of incubation. This group effect was significant during the cycle. In 99.8% of the cycles the variation was determined by incubation.

The rationale for culling of rodent litters

Based on a review of the pertinent literature and our own unpublished data, it is recommended that culling of rodent litters in the early postnatal period should be a standard practice in delivery-type reproduction studies. This, in turn, will reduce the litter size-induced variability in the growth and development of pups during the postnatal period and thus increase the sensitivity of statistical analyses to detect treatment-related effects. This will also ensure that any adverse effects on pup growth (body weight gain) and development (reflex and behavior development) are not masked by a treatment-induced reduction in litter size. The culling should be carried out randomly and no attempt should be made to selectively cull sick or underweight pups. Since male pups weigh significantly more than females and studies have shown differences in maternal behavior toward one sex over the other, whenever possible each culled litter should consist of an equal number of males and females.

Some considerations for the development of diets for mature rodents used in long-term investigations

Nutritional requirements for mature rodents used in long-term investigations are virtually unknown. The limited knowledge of the dietary needs of mature rodents is due in part to overreliance on weanling animals fed an experimental diet for relatively short periods. Generalizations made from observations of weanling rodents are not appropriate for all ages. Dietary recommendations for rodents have been established, for the most part, by using the nutritional benchmark of maximal growth rate in animals fed ad libitum. Although this method provides valuable insight into the understanding of nutritional deficiency, it is less effective in determining nutrient requirements for mature animals used for the long term. The implication that maximal growth resulting from ad libitum feeding may not indicate the best dietary regimen in the long term is consistent with the observation that energy-restricted rodents live significantly longer and have lower incidence of disease that do their ad libitum-fed counterparts. These and other findings discussed in the review suggest that nutrient requirements established for young rodents may need re-evaluation to determine their applicability to the dietary recommendations for older animals used in long-term investigations.

[Conditions for the laboratory survival of Haemagogus janthinomys dyar, 1921 (Diptera:Culicidae)]

A little modification was made on the classical Borel tube, used for rearing isolated females of mosquitoes. The first studies were realized with the main Yellow fever vector, Haemagogus janthinomys, in Brazil. The results are: a better survival, as far as 72 days, a greater number of eggs, up to 80, and a shorter trophogonic cycle of 7-8 days. So, one can imagine more easily further studies about the vertical transmission of the YF virus by this important neo-tropical mosquito.

Territorial aggression, body weight, carbohydrate metabolism and testosterone levels of wild rats maintained in laboratory colonies

Aggressive territorial behavior was studied in 15 colonies of wild rats (Rattus norvegicus), each consisting of 2 males and 1 female. One of the males attacked an intruder rat more frequently and had a higher body weight than the less aggressive one. In another experiment, male and female rats were raised in colonies from weaning to adulthood. Animals were weighed every 7 days until 90 days of age when plasma testosterone was measured in males, and plasma glucose, hepatic and muscle glycogen were measured in both males and females. THe heavier (and thus possibly dominant) males in the colonies of 3 males and 1 female also had a higher body weight than males raised with females, but without any male partner. In this long-term social relationship there were no significant differences in carbohydrate metabolism among the animals. The differential growth rate among males was established around the period of sexual maturity. Moreover, when adult, heavier males had higher plasma testosterone levels compared to the other members of the colony and also to males that had no other competitive male partner. This higher androgenic hormone level may be one of the causal factors involved in the weight increase of the dominant male in the colony.

[Population statistics of Triatoma sordida Stäl 1859 (Hemiptera:Reduviidae) in experimental conditions]

Four cohorts of 100 Triatoma sordida eggs were reared under standard laboratory conditions (28 degrees C, 63% R.H.) and fed weekly on hens during 40 minutes. The numbers of dead insects, moults and eggs laid were recorded weekly. A constant survival value was observed without any important peaks in the four cohorts. Life expectancy was 37.4 weeks for males and 36.8 weeks for females. The average generation time was 61.7 weeks. The average net reproduction rate suggests that this population would increase 143.2 times during each generation. The average intrinsic rate of natural increase was 0.082 per individual per week. The highest reproductive value was observed 3 weeks after entering the adult stage. The age structure, assuming stable age distribution, would be 32% eggs, 26% of first instar nymphs, 19% of second instar nymphs, 13% of third instar nymphs, 6% of fourth instar nymphs, 3% of fifth instar nymphs and 1% of adults. Our results suggest that this species behaves as a k-strategist under experimental conditions.

Development of predictive models of laboratory animal growth using artificial neural networks

Traditional regression analysis of body weight growth curves encounters problems when the data are extremely variable. While transformations are often employed to meet the criteria of the analysis, some transformations are inadequate for normalizing the data. Regression analysis also requires presuppositions regarding the model to be fit and the techniques to be used in the analysis. An alternative approach using artificial neural networks is presented which may be suitable for developing predictive models of growth. Neural networks are simulators of the processes that occur in the biological brain during the learning process. They are trained on the data, developing the necessary algorithms within their internal architecture, and produce a predictive model based on the learned facts. A dataset of Sprague-Dawley rat (Rattus norvegicus) weights is analyzed by both traditional regression analysis and neural network training. Predictions of body weight are made from both models. While both methods produce models that adequately predict the body weights, the neural network model is superior in that it combines accuracy and precision, being less influenced by longitudinal variability in the data. Thus, the neural network provides another tool for researchers to analyze growth curve data.

Cross-sectional growth standards for captive baboons: I. Organ weight by chronological age

We present the first cross-sectional organ weight reference standards for captive baboons (Papio hamadryas). Organ weight data were obtained from necropsy reports for 634 healthy, pedigreed, captive female and male baboons. From summary statistics we calculated and fit cross-sectional, sex-specific percentile curves for: adrenals, brain, eyes, heart, kidneys, liver plus gall bladder, lungs, pancreas, pituitary gland, spleen, and thyroid gland in two year age class intervals and summary statistics by sex for each organ in one year age classes.

Cross-sectional growth standards for captive baboons: II. Organ weight by body weight

We present the first cross-sectional organ weight by body weight reference standards for captive baboons (Papio hamadryas). Organ weight data were obtained from necropsy reports for 634 healthy, pedigreed, captive female and male baboons. From summary statistics we calculated and fit cross-sectional sex-specific percentile curves for: adrenals, brain, eyes, heart, kidneys, liver plus gall bladder, lungs, pancreas, pituitary gland, spleen, and thyroid gland in three kilogram body weight intervals and cross-sectional summary statistics by sex for each organ in one kilogram body weight intervals.

Laboratory survival, growth, and digestive gland histologic features of squids reared on living and non-living fish diets

The effects of non-living diets on the survival, growth, and digestive gland histologic features of the bigfin reef squid (Sepioteuthis lessoniana Lesson, 1830) cultured in the laboratory were evaluated during one-half of their life cycle (95 days). Two groups of squids (n = 16 per group) were held in closed seawater systems with similar water volume, temperature, salinity, water filtration, and water flow velocities. Food for the control group consisted of live, freely swimming fish (Cyprinodon variagatus); the test group was trained to grab freshly dead fish (days 1 to 45) and then thawed, frozen fish (days 46 to 95). The two groups were evaluated for differences in (1) food intake, (2) survival, (3) growth (wet weight, mantle length, instantaneous growth rate), (4) morphologic (mantle thickness in four locations, digestive gland weight), and (5) digestive gland histologic features (indices for nuclear density and relative vacuolar density). Unexpectedly, no significant differences were found between the two groups. Mean wet weight increased from 32.1 g to 342.9 g for the control group and from 58.6 g to 372.0 g for the group fed dead food. The results demonstrate that laboratory-cultured squids can survive and grow when fed dead fish (fresh or frozen) as well as live fish without adverse effects on growth, survival, or digestive gland histologic features.

A simple technique to feed newborn piglets

We describe a simple and relatively inexpensive technique for feeding conventionally reared newborn pigs. The feeding system consists of a nipple assembly and an enteral feeding bag. Piglets are weaned at 4-10 h of age and are initially bottle-fed a simulated sow's milk formula. After adaptation to the synthetic nipple and artificial milk, the piglets are placed on the semiautomatic feeding system. Piglets fed in this manner gain weight at rates comparable to sow-reared animals or animals fed via completely automated systems.

[Management of individual body weight growth of infant squirrel monkey (Saimiri sciureus) in indoor breeding colony]

We biometrically analyzed the body weight growth data of new-born squirrel monkeys, obtained during the nursing period from 0 to 12 weeks of age. Body weight (y in grams) could be expressed as a function of birth weight (a in grams) and age (x in weeks) by the following equation: y = a + b x, where b indicates growth rate. This equation corresponded significantly with actual growth curves (R2 = 0.96). The frequency distribution of b values was demonstrated to be abnormal distribution. This value was used to judge whether the body weight growth of each monkey was normal or abnormal. The lower control limit (LCL) was calculated by using a linear equation with the b value of 9.07 (M-1.25 x S.D.) and each birth weight. For the monkeys whose body weight was above the LCL during the first three weeks after birth, it was determined whether the frequency of weighings could be reduced from 13 to 7. Using the same animals, no significant difference was detected between the b value estimated from 13 measurements and that estimated from 7 measurements. Thus, from the standpoint of management's policy to save labor, the frequency of weighings could be reduced. A new daily routine has been established in our primate center to save labor by reducing the number of body weighings of the many infant monkeys. In the new program, newborn monkeys whose body weight is above the LCL are weighed only 7 times during the nursing period of 12 weeks, while those whose weight is below the LCL are weighed 8 to 13 times.

Calomys laucha (Rodentia, Cricetidae): growth and breeding in laboratory conditions

The husbandry and breeding of Calomys laucha (Rodentia, Cricetidae) in captivity are described. Growth curves based on body weight and length showed statistical differences between sexes after 45 days, males being heavier than females. The overall reproductive efficiency was 53.4% but birth rate was depressed during winter. Gestation length was 21 +/- 1 days and females exhibited postpartum oestrus with a 3-7 day implantation delay (51%). Litter size was 5.3 +/- 1.1 (n = 34). Pup survival at weaning was 84.9%. Mean life span in laboratory conditions was 13.5 months and a cumulative mortality of 90% was reached at 27-28 months of age.

Growth of the clavicle and development of clavicular secondary cartilage in the embryonic mouse

Whether secondary cartilage develops in the mammalian clavicle has been a matter of controversy. This study documents, in the embryonic mouse: (a) the onset of clavicular osteogenesis at 14 days of gestation (Theiler stage 22); (b) the appearance of secondary cartilage at 16 days of gestation (Theiler stage 24) and its persistence as a prominent cartilage until 18 days of gestation; (c) that the relative growth rate of the clavicle is much higher (0.097 mg/g body weight/day) between 16 and 17 days of gestation than at later ages (mean of 0.005 mg/g/day between 17 days of gestation and 4 days postnatally), and (d) that secondary cartilage failed to form in clavicles from 15-day-old embryos maintained in vitro. We conclude that secondary cartilage is a feature of the developing mouse clavicle, that it arises when the relative growth rate of the clavicle is highest, and that the most likely stimulus for differentiation of this cartilage is mechanical, muscle-based and associated with rapid relative clavicular growth.