Showing papers on "Larva published in 1989"

Mycetocyte symbiosis in insects.

Abstract: 1. Non-pathogenic microorganisms, known as mycetocyte symbionts, are located in specialized 'mycetocyte' cells of many insects that feed on nutritionally unbalanced or poor diets. The insects include cockroaches, Cimicidae and Lygaeidae (Heteroptera), the Homoptera, Anoplura, the Diptera Pupiparia, some formicine ants and many beetles. 2. Most mycetocyte symbionts are prokaryotes and a great diversity of forms has been described. None has been cultured in vitro and their taxonomic position is obscure. Yeasts have been reported in Cerambycidae and Anobiidae (Coleoptera) and a few planthoppers. They are culturable and those in anobiids have been assigned to the genus Torulopsis. 3. The mycetocyte cells may be associated with the gut, lie free in the abdominal haemocoel or be embedded in the fat body of the insect. The mycetocytes are large polyploid cells which rarely divide and the symbionts are restricted to their cytoplasm. 4. The mycetocyte symbionts are transmitted maternally from one insect generation to the next. In many beetles (Anobiidae, Cerambycidae, Chrysomelidae and cleonine Curculionidae), the microoganisms are smeared onto the eggs and consumed by the hatching larvae. In other insects, they are transferred from mycetocytes to oocytes in the ovary, a process known as transovarial transmission. The details of transmission in the different insect groups vary with the age of the mother (adult, larva or embryo) at which symbiont transfer to the ovary is initiated; whether isolated symbionts or intact mycetocytes are transferred; and the site of entry of symbionts to the egg (anterior, posterior or apolar). 5. Within an individual insect, the biomass of symbionts varies in a regular fashion with age, weight and sex of the insect. Suppression of symbiont growth rate and lysis of 'excess' microorganisms may contribute to the regulation of symbionts (including freshly-isolated preparations of unculturable forms) are used to investigate interactions between the partners. However, some methods to obtain aposymbiotic insects (e.g. antibiotics and lysozyme) deleteriously affect certain insects and aposymbionts may differ from the symbiont-containing stocks from which they were derived. 7. The mycetocyte symbionts have been proposed to synthesize various nutrients required by the insect. The symbionts of beetles and haematophagous insects may provide B vitamins and those in cockroaches and the Homoptera essential amino acids. The role of symbionts in the sterol nutrition of insects is equivocal. 8. Mycetocyte symbionts may have evolved from gut symbionts or guest microorganisms. The association is monophyletic in cockroaches but polyphyletic in many groups, including the sucking lice, beetles and scale insects.(ABSTRACT TRUNCATED AT 400 WORDS)

Density-Dependent Growth and Survival of Larval Ambystoma: Evidence from Whole-Pond Manipulations

Abstract: To determine whether growth and survival of marbled salamander larvae were density dependent under natural conditions, I established hatchlings at either natural density or one—fourth natural density in paired halves of 11 natural ponds. I sampled ponds at 7, 11, and 15 wk and at the initiation of metamorphosis, comparing percentage of larvae injured, larval size, and larval survivorship. I also compared density, size, and biomass of zooplankton, the dietary staple of larvae. Reducing density increased mean larval body size on all sample dates except week 7, and mean size at the initiation of metamorphosis was negatively correlated with average larval density during the larval period. Mean size at the initiation of metamorphosis was correlated positively with average zooplankton biomass during the larval period, which suggests that food was limiting in many ponds. Surprizingly, however, reducing larval density did not increase zooplankton biomass, number, or density relative to controls. Density reductions significantly increased larval survival on all sample dates. Many populations exhibited Type II survival, but survival tended towards Type I at sites where ponds contracted severely near the end of the larval period. Mortality associated with pond contraction was due to changes in biotic or physical factors associated with pond contraction, and not to desiccation per se. Most larvae suffered tail damage caused by attacks from conspecifics and/or invertebrates. high larval mortality in contracted ponds was associated with increased larval density and injury frequency. The proportion of animals showing tail damage was significantly less in reduced—density treatments compared to natural—density treatments. Tail—damaged animals were smaller than undamaged animals, perhaps because loss of tail tissue compromised growth. Because larvae did not reduce zooplankton biomass, it is unlikely that exploitative competition for zooplankton was the primary cause of density—dependent growth and survival. My data suggest that intraspecific aggression may be more important than exploitative competition in explaining density dependence in Ambystoma larvae.

Influence of Delayed Metamorphosis on the Growth and Metabolism of Young Crepidula fornicata (Gastropoda) Juveniles

Abstract: Larvae of most marine invertebrates delay metamorphosis ifthey fail to contact an appropriate en vironmental stimulus. We conducted seven experiments with the slipper shell snail, Crepidulafornicata, to deter mine if delaying metamorphosis decreases juvenile fit ness. Larvae were reared in the laboratory at 25°C on the unicellular alga Isochrysis sp. (clone T-ISO, 18 X iO@ cells m1'), and were induced to metamorphose after long, medium, or short periods ofdelayed metamorpho sis. Long delay larvae were reared until they metamor phosed spontaneously in acid-cleaned glassware. Me dium and short delay larvae were induced to metamor phose with adult-conditioned seawater or 20 mM elevations ofKCl. Juveniles were subsequently reared for about one to two weeks at 25°C in the laboratory on a diet ofT-ISO. Delaying metamorphosis generally did not lower juvenile weight-specific feeding rates, increase ju venile weight-specific respiration rates, or lower juvenile shell or tissue growth rates, any of which effects would suggest that delaying metamorphosis reduces juvenile fitness. Moreover, there was no indication that delaying metamorphosis reduced juvenile tolerance of tempera ture-salinity stress. Delaying metamorphosis of C.forni cata does not appear detrimental, at least for the first few weeks ofjuvenile life.

Heterochronic genes control the stage-specific initiation and expression of the dauer larva developmental program in Caenorhabditis elegans.

Abstract: We report that a stage-specific developmental program, dauer larva formation, is temporally regulated by four heterochronic genes, lin-4, lin-14,1in-28, and 1in-29. The effects of mutations in these four genes on dauer larva formation have revealed that they regulate two different processes of dauer larva formation: (1) a decision specifying the larval stage at which dauer larva development initiates, and (2) the specialized differentiation of hypodermal cells during dauer larva morphogenesis. Epistasis analysis has suggested a model in which lin-4 negatively regulates lin-14, and the resulting temporal decrease in lin-14 activity specifies the stage of dauer larva initiation. Our results further suggest that dauer larva morphogenesis by hypodermal cells requires that 1in-28 acts to inhibit 1in-29 during early larval stages.

Life history consequences of feeding versus non-feeding in a facultatively non-feeding toad larva.

Abstract: Bufo periglenes, a toad endemic to montane Costa Rica, produces an unusually small clutch of large, yolk-rich eggs. The toads breed in small ephemeral pools that are unpredictable in duration and may be low in food availability. Two congeners, Bufo coniferus and Bufo marinus, occur nearby, breed in more permanent bodies of water that offer more food, and exhibit the typical toad pattern of large clutches of small eggs. Tadpoles of all three species feed on detritus and suspended organic material. By raising tadpoles of the three species individually with and without food I investigated the relationship between egg size (yolk provision) and tadpole survival. All of the unfed B. coniferus and B. marinus tadpoles grew little and died soon after developing to the hindlimb bud stage. On the other hand, all of the unfed B. periglenes tadpoles metamorphosed successfully, demonstrating that the tadpoles are facultatively non-feeding; developmental time from hatching to metamorphosis was significantly shorter for unfed tadpoles than for fed tadpoles, but fed individuals were significantly larger at transformation. Faster developmental rate and larger body size at transformation are both advantageous for frogs and toads, but cannot be attained simultaneously. Large egg size may afford flexibility in unpredictable environments. In pools where food is available, tadpoles presumably eat, take longer to metamorphose, but are larger at transformation than tadpoles developing in nutrient-poor sites. Small body size at transformation (a consequence of not eating) has potential costs, but the large quantity of yolk provided by a large egg enhances the probability of metamorphosis in food-limited environments.

Palophaginae, a new subfamily for leaf-beetles, feeding as adult and larva on araucarian pollen in Australia (Coleoptera: Megalopodidae).

Abstract: A new genus Palophagus and a new subfamily Palophaginae are proposed for a megalopodid chrysomeloid beetle reared from male strobili (cones) of Araucaria bidwillii from south Queensland, Australia. The beetle feeds as adult and larva on pollen. The larva pupates in the soil where it goes through an additional but inactive instar. The beetle shares with Megalopodinae a mesonotal stridulatory organ and the same characteristic male and female genitalia but differs in various other structures. The relationship of the subfamily is discussed. A key to families of Chrysomeloidea based on the male and female genitalia is offered as well as keys to the genera and species of Palophaginae. Palophagus bunyae and P. australiensis are described as new, and Cucujopsis setijer Crowson is transferred from Orsodacninae to Palophaginae and redescribed. Habitus drawings of two adults are provided. The immature stages of Palophagus species are described and illustrated.

Sibling cannibalism in noncannibal morph Ambystoma tigrinum larvae and its correlation with high growth rates and early metamorphosis

Abstract: We describe here, for the first time, the existence of an Ambystoma tigrinum tigrinum larval morph characterized by fast growth rates and early metamorphosis and triggered by cannibalism. This new ...

Interaction between the effects of pH and density on growth and development in Rana temporaria L. tadpoles

Abstract: The common frog (Rana temporaria L.) occurs in areas where waters are naturally acid and where breeding sites are susceptible to acidification from anthropogenic sources. Acid conditions have been shown to cause embryo mortality. They can also delay metamorphosis and reduce size at metamorphosis among individual tadpoles. Time of metamorphosis and size at metamorphosis may also be influenced by crowding effects. It is conceivable that reductions in tadpole density arising from embryo mortality will offset depressant effects of acid conditions on individual tadpoles. Furthermore, interactions among tadpoles may be modified by individuals' responses to acid conditions. To investigate such possible effects, common frog tadpoles were raised to metamorphosis in the laboratory at three densities (4, 8 and 16 tadpoles litre-1) and two levels of pH (nominally pH 4 and pH 7) on a limiting ration. Overall, the effects of density on size at metamorphosis and time of metamorphosis far outweighed those of low pH. The depressant effect of low pH on mean development rate and mean size at metamorphosis decreased with increasing tadpole density. Low pH accentuated hierarchical effects within density replicates, and dominant tadpoles suffered little or no net retardation of growth or development due to low pH. Tadpoles which grew and developed rapidly at low pH suffered debilitating limb deformities. The implications of these interactive effects of density and pH are discussed in the context of freshwater acidification and its possible effects on frog populations. The response of individuals in a group is likely to be more important than the mean response of the group. Key-words: Amphibian, frog, Rana temporaria, tadpole, pH, density, interaction, growth, metamorphosis, acidification, deformity

Susceptibility and Immune Response of Western Corn Rootworm Larvae (Coleoptera: Chrysomelidae) to the Entomogenous Nematode, Steinernema feltiae (Rhahditida: Steinernematidae)

Abstract: Susceptibility of third-instar western corn rootworms, Diabrotica virgifera virgifera LeConte, to the Agriotos, All, Breton, and Mexican strains of the entomogenous nematode Steinemema feltiae was compared based on concentration-mortality regressions. Larvae were most susceptible to the Mexican strain, less susceptible to the Agriotos and Breton strains, and least susceptible to the All strain. The Mexican strain was 22 times more virulent than the Allstrain. Rootworm larvae encapsulated invading nematodes of all strains, but the frequency of encapsulation was lower for the Mexican and Agriotos strains. Apparently, the defensive response of encapsulation had only a minor effect on larval susceptibility. Frequency of encapsulation and larval susceptibility were not consistently related.

Larvae of the sea hare Aplysia californica settle and metamorphose on an assortment of macroalgal species

Abstract: Larvae of the sea hare Aplysia californica (Molluscs: Opisthobranchia) spend several weeks feeding in the plankton pnor to settlement and metamorphosis Previous work indicated that metamorphosis was tnggered by only one (or a t most a few) algal species. However, in the present laboratory study, a mean of 30 % or more of the larvae of this sea hare metamorphosed in response to 10 of 18 species of intertidal macroalgae (9 red. 7 brown, 2 green). Metamorphosis was greatest in response to the red algae Rhodymenja californica, Corallina officinalis, Plocamjurn cartilagineurn and Laurencia pacifjca. Juveniles of A. californica that had metamorphosed on the last 2 species grazed on them and began to grow, whereas juveniles on the other species tended to crawl off the alga and around the assay dish. Of the 8 algae least preferred, only 1 was red, the remainder brown or green. For larvae of A. californica, metamorphosis on a relatively wide spectrum of algal species may be more efficacious than metamorphosis on any one alga, because juvenile sea hares can readily crawl to nearby algal species that they prefer to eat after they have metamorphosed on an alga that is not t h e ~ r preferred food. Most marine invertebrates pass through a planktonic larval stage prior to settlement and metamorphosis, and the recruitment of their larvae is important in structuring benthic marine communities (Keough & Downes 1982, Keough 1983, Gaines & Roughgarden 1985). Larval settlement is largely regarded as a response to complex, and often highly specific, environmental stimuli (Burke 1983, Crisp 1984), especially chemical cues (reviewed in Hadfield 1986, Pawlik & Faulkner 1986). However, few naturally-occurring chemical inducers of larval settlement and metamorphosis have been isolated and identified (Kato et al. 1975, Cuomo 1985, Pawlik 1986). ' Present address: Friday Harbor Laboratories, University of Washington, 620 University Road, Friday Harbor, Washington 98250, USA O Inter-Research/Printed in F R. Germany Marine molluscs of the genus Aplysia are among the most intensively studied animals on earth and have been the subject of research on development, growth and energetics, circadian rhythms, and the neural basis for learning, memory and behavior (reviewed in Kandel 1979, Carefoot 1987). Research interest in one of the best studied sea hares, A. califol-nica, from the coast of California, prompted the laboratory cultivation of the planktotrophic larvae of these animals through metamorphosis (Kriegstein et al. 1974). In the field, young recruits of these herbivorous snails were most frequently found eating red algae, primarily of the genus Laurenc ia (Kupfermann & Carew 1974). Moreover, several putatively defensive halogenated natural products isolated from adult A. californica were found to be derivatives of metabolites of L. paci f jca (Stallard & Faulkner 1974), suggesting some dependence of the molluscs on this alga. Larval settlement of Aplysia californica was reported to be highly substrate-specific, and chemical inducers were believed to be responsible for substrate choice (reviewed in Carefoot 1987). Kriegstein et al. (1974) found that laboratory-reared larvae would settle and metamorphose on Laurenc ia paci f ica , but not on species of Plocarnium, Polysiphonia, Daysia , C h o n d r u s or Ulva. Subsequently, Capo et al. (1979) reported that 2 red algae from the New England coast, N e o a g a r dhei l la baileyl and Graci lar ia sp. , would also induce settlement and metamorphosis of A . californica. The study described herein was initiated in a n effort to isolate and identify compounds from L. paci f ica that induced metamorphosis of A. californica. It was discovered, however, that metamorphosis of A. californica was much less specific than had been previously reported. 196 Mar. Ecol. Prog. Se Materials and methods. All larvae used in experiments were the progeny of 2 specimens of Aplysia californica that had been cultured as larvae in the lab, had metamorphosed upon exposure to branchlets of Laurencia pacifica, and had been reared from juveniles to reproductive adults on a diet of Plocamium cartilagineum and L. pacifica. Small pieces of egg mass were placed in aerated beakers containing l pm-filtered, natural seawater (hereafter referred to as 'seawater') until hatching occurred. Larvae were then transferred to 2 1 Fernbach flasks filled to the neck with seawater containing 40mg 1-' each of the antibiotics streptomycin sulfate and sodium penicillinG (Sigma Chemical Co., St. Louis, Missouri) and 104 cells ml-' of the green flagellate Pavlova lutheri. Larval entrapment a t the air/water interface was prevented by spreading flakes of cetyl alcohol (l-hexadecanol, Sigma) on the water surface. Flasks were kept a t 20°C in a chamber 35 cm beneath 2 continuously-illuminated 60 W fluorescent lights. Every 4 d , culture vessels were cleaned.

Larval diet and the vector competence of Culex annulirostris (Diptera: Culicidae) for Murray Valley encephalitis virus.

Abstract: Culex annulirostris Skuse larvae were reared on two different amounts of powdered dog chow and yeast, low intake (2.8 micrograms/larva) and high intake (8.4 micrograms/larva), to produce adults with mean wing lengths of 3.25 and 3.7 mm, respectively. The resulting adults were fed different dosages of Murray Valley encephalitis virus and after 10 d extrinsic incubation at 28 degrees C, the infection rate, transmission rate, salivary gland, and body titers were determined. There were no significant differences in any of these parameters.

Predator‐mediated coexistence in laboratory communities of mycophagous Drosophila (Diptera: Drosophilidae)

Abstract: . 1. This laboratory experiment examined the effects of interspecific competition and predation by Ontholestes cingulatus Gravenhorst (Coleoptera: Staphylinidae) on three species of mycophagous Drosophila (Diptera: Drosophilidae): D.tripunctata Loew, D.falleni Wheeler and D.putrida Sturtevant. 2. Single-species and three-species assemblages were exposed to single commercial mushrooms on wet pine shavings in 200 ml culture bottles. A predacious rove beetle (Ontholestes cingulatus) was present in half of the three-species replicates. The stocked adult flies and beetles were removed after 4 days, and the number, biomass and mean mass of emerging progeny was recorded. 3. For all three species the abundance and biomass of the progeny emerging in the ‘no predator’ communities' was significantly less than for the progeny emerging in single-species replicates, suggesting an interspecific competitive effect. D.tripunctata was the competitive dominant; it emerged in abundance from all seven three-species ‘no predator’ communities while D.putrida and D.falleni were often excluded. 4. The decrease in production was attributed to strong interspecific competition among larva and not interference among ovipositing adults. 5. Predation on ovipositing adults significantly reduced the number and biomass of D.tripunctata progeny emerging, and indirectly facilitated the number and biomass of emerging D.falleni and D.putrida.Predation on adults reduced larval recruitment, relaxed larval competition, and released the inferior competitors.

Cryobiology of Musca domestica: Supercooling Capacity and Low-Temperature Tolerance

Abstract: The supercooling capacity and cold tolerance of Musca domestica L. embryos, larvae, prepupae, pupae, and adults were examined. Two-h-old embryos had the greatest supercooling capacity (−34°C) followed by 2-d-old pupae (−24°C), adults (−16°C), 1-d-old larvae (−15°C), and prepupae (−14°C). Significant differences ( P ≥ 0.001) between temperatures of crystallization means were observed among and within several stages. Age within a developmental stage was critical to survival at the treatment temperatures tested. The 50% mortality levels of the five developmental stages exposed to 10, 5, 0, and −5°C were determined and compared with the supercooling capacity. At temperatures above O°C, pupae were the most cold tolerant, followed by adults, larvae and prepupae, and embryos. However, at −5°C, 10- and 12-h-old embryos were able to tolerate the longest exposure, followed by pupae, larvae, prepupae, and adults. With this insect, the temperature of crystallization is not a reliable indicator of the lowest lethal temperature.

Effect of water hyacinth leaf extract on mortality, growth and metamorphosis of certain pests of stored products

Abstract: Petroleum ether extract of Eichhornia crassipes (Mart) Solm. was evaluated for its biological activity against Tribolium castaneum (Herbst), Sitophilus oryzae (L.), Callosobruchus maculatiti (F.) and Corcyra cephalonica (Stainton). The crude extract included in the diet of insects retarded development and caused mortality in the fourth instar larvae of T. castaneum and C. cephalonica . Cuticle melanization in patches were observable in C. cephalonica larvae. High mortality of adult C. maculatus occurred in insects confined to the treated diet as well as in insects exposed to treated surfaces. The extract did not show any toxicity to adult S. oryzae .

Survival of Trichinella muscle larvae in frozen wolf tissue in Italy.

Abstract: Living larvae were collected in central It- aly from the masseters of a wolf frozen for 6 mo. These parasites were identified as a southern Palearctic species (Trichinella sp. 3) through gene-enzyme analysis. At the second passage in laboratory mice, the muscle lar- vae were unable to survive at - 10 C for 5 days. Bio- logical and epidemiological implications are discussed. The resistance to freezing of Trichinella mus- ABSTRACT: Living larvae were collected in central It- aly from the masseters of a wolf frozen for 6 mo. These parasites were identified as a southern Palearctic species (Trichinella sp. 3) through gene-enzyme analysis. At the second passage in laboratory mice, the muscle lar- vae were unable to survive at - 10 C for 5 days. Bio- logical and epidemiological implications are discussed. The resistance to freezing of Trichinella mus-

Effect of temperature and host plant on development of three species of leafrollers (Lepidoptera: Tortricidae).

Abstract: Three species of leafrollers were reared to maturity on fresh leaves or diets prepared from freeze-dried leaves of various host plants. Linear relationships were found between development rate and temperature for brownheaded (Ctenopseustis sp.) and greenheaded leafroller (Planotortrix excessana) larvae and pupae reared at 11.5, 18.0 and 22.5°C. Rate of pre-imaginal development was affected by insect sex and species and larval host plant. Greenheaded leafroller developed faster than the brownheaded leafroller. Males of all 3 leafroller species developed faster than females for larvae, while the reverse applied for pupae. Leafrollers developed relatively faster on some host plants and produced relatively larger insects, e.g., lightbrown apple moth (Epiphyas postvittana) on broadleaved dock (Rumex obtusifolius). Insects developed more slowly on diets based on freeze-dried leaves to produce heavier individuals than insects reared on fresh leaves of the same hosts.

Larval habitat duration and size at metamorphosis in frogs

Abstract: The relationship between size at metamorphosis and adult size was studied in 12 closely-related species of frog from Malawi (Central Africa). These species of frogs breed in water of different durations, and occupy different habitats as adults. We could demonstrate no correlation between size at metamorphosis and size of adults when frogs were divided into groups on the basis of occupying similar habitats as adults, but when frogs were divided into groups on the basis of similar duration of larval habitat we demonstrated a strong correlation between size at metamorphosis and adult size. Thus we suggest that duration of the larval habitat is a major determinant of size at metamorphosis, with species which breed in the more temporary habitats metamorphosing at smaller size than species which breed in more permanent habitats, but which are of similar size as adults. Such manipulation of the life cycle appears to be adaptive since it results in individuals becoming independent of water earlier when the likelyhood of early loss of larval habitat is high.

Larval ambystoma: evidence from whole-pond manipulations'

Abstract: To determine whether growth and survival of marbled salamander larvae were density dependent under natural conditions, I established hatchlings at either natural density or one-fourth natural density in paired halves of 11 natural ponds. I sampled ponds at 7, 11, and 15 wk and at the initiation of metamorphosis, comparing percentage of larvae injured, larval size, and larval survivorship. I also compared density, size, and biomass of zooplankton, the dietary staple of larvae. Reducing density increased mean larval body size on all sample dates except week 7, and mean size at the initiation of metamorphosis was negatively correlated with average larval density during the larval period. Mean size at the initiation of metamorphosis was correlated positively with average zooplankton biomass during the larval period, which suggests that food was limiting in many ponds. Surprizingly, however, reducing larval density did not increase zooplankton biomass, number, or density relative to controls. Density reductions significantly increased larval survival on all sample dates. Many populations exhibited Type II suvival, but survival tended towards Type I at sites where ponds contracted severely near the end of the larval period. Mortality associated with pond contraction was due to changes in biotic or physical factors associated with pond contrac- tion, and not to desiccation per se. Most larvae suffered tail damage caused by attacks from conspecifics and/or invertebrates. High larval mortality in contracted ponds was associated with increased larval density and injury frequency. The proportion of animals showing tail damage was significantly less in reduced-density treatments compared to natural-density treatments. Tail-damaged animals were smaller than undamaged animals, perhaps because loss of tail tissue compromised growth. Because larvae did not reduce zooplankton biomass, it is unlikely that exploitative competition for zooplankton was the primary cause of density-dependent growth and survival. My data suggest that intraspecific aggression may be more important than ex- ploitative competition in explaining density dependence in Ambystoma larvae.

Drift postures of nemourid stonefly larvae (Insecta, Plecoptera)

Abstract: Larva drifting behaviour of eight Nemourid stonefly species was studied in the laboratory. These aquatic insects demonstrated three distinct body postures, with a species‐specific preference for different poses. The effect of posture on drift dynamics is discussed.

Identity of the Hydropsychid Larva Known as "Oropsyche?": The Immature Stages of Homoplectra flinti Weaver

Abstract: Collections of pharate pupae, pupae, and pharate adults of the larva tentatively assigned to Oropsyche by G. B. Wiggins (Larvae of the North American caddisfly genera, University of Toronto Press, 1977) have revealed that these larvae are actually those of Homoplectra flinti Weaver. At present the immature stages and habitat of Oropsyche remain unknown. The larval retreat and pupa of H. flinti are described and figured.

Metamorphosis in the frog Arthroleptella lightfooti (Anura, Ranidae) with emphasis on neuro-endocrine mechanisms

Abstract: The Cape chirping frog, Arthroleptella lightfooti, has a type of direct development in which nonfeeding larval stages undergo an early metamorphosis resulting in the rapid attainment of the adult form. Precocious metamorphosis may be the result of the precocious activation of the same neuro-endocrine mechanisms known to regulate metamorphosis in species having free-living larvae. Alternatively there is evidence that during the course of evolution, metamorphosis in species with direct development has become largely independent of thyroid control. In this study we investigate this problem by comparing the timing of development of the median eminence in A. lightfooti relative to the timing of metamorphosis. The resulting data allow a comparison of the role of the median eminence during metamorphosis to be made between A. lightfooti and Xenopus laevis (a frog with free-living larvae). The results suggest that the brain — pituitary — thyroid axis is involved in the control of metamorphosis in A. lightfooti.

Ostertagia Ostertagi: Population Dynamics Under Pasture and Confinement Conditions With Particular Reference to the Inhibition Phenomenon.

Abstract: This experiment was conducted to further define epidemiological events involved in the induction, duration and maturation phases of inhibited development of Ostertagia ostertagi in naturally infected calves and to characterize some aspects of the immune response associated with the inhibition phenomenon. During March, April and May 1988, 3 groups of 18 calves were grazed on the same experimental pasture for 3 weeks. At the end of each grazing period, 2 calves of each group were slaughtered for analysis of worm population; the remaining calves were divided into 2 subgroups of 8 calves. One subgroup was returned to pasture while the other was placed in confinement. At 2-week intervals herbage samples were collected for larval recovery. Large numbers of 0. ostertagi early 4th-stage larvae (EL4) were observed in calves placed on pasture in March and April, while calves introduced in May had smaller numbers of parasites and lower percentages of EL4. Ostertagia ostertagi larval inhibition was attributed to seasonal factors. Similar level of EL4 in grazed and confined calves, suggested that inhibition was not

An imported case of myiasis caused by a larva of cordylobia anthropophaga from africa

Abstract: A 25 year-old Japanese man (musician) had been in Middle-Africa for the concert-tour from 14 January to 20 February 1989 On 21 February after homecoming to Japan, a lesion with a severe pain was found in the right abdomen He expelled a white larval worm (15 cm in length) from this lesion by pressure of his fingers This larval worm taken out from the lesion was identified as the third-stage larva of Cordylobia anthropophaga (Blanchard, 1893), by their pair of toothed, spade-like oral hooklets and by several pairs of posteriorly directed fleshy processes arising from the twelve abdominal segments, as well as by the character of the posterior spiracles, which lack a distinct chitinous rimThe disease caused by the larva of C anthropophaga is a familiar form of myiasis in Africa This fly lays its eggs on dry sand polluted with the excrement of animals, or clothing The hatched larva invade the skin of human and animals This patient may be contacted with a larva of this fly in Africa

Essential fatty acid status of laboratory-reared mosquitos improved by supplementing crude larval foods with fish oils

Abstract: Laboratory mosquitos are commonly maintained using larval media based on crude food materials such as powdered animal chows, dried yeast, liver powder, etc. Males of Culex tarsalis so reared for use in studies of sterile male control methods proved unsuccessful in competition for mates against wild males in the field, even if tested after one generation of laboratory rearing. Such laboratory-reared adults had much lower levels of an essential fatty acid, eicosapentaenoic acid (EPA) than wild C. tarsalis adults from the sterilc-male-control experimental sites. Hypothesizing that suboptimal essential fatty acid status might reduce adult vigor, we attempted to raise levels of EPA in tissues of laboratory-reared C. tarsalis by supplementing the larval food mixture with fish oils, which are rich sources of EPA and related n3 polyunsaturated fatty acids. Supplementation with codliver oil doubled tissue phospholipid EPA levels compared with unsupplemented controls, and a proprietary fish oil, Walgreen EPA 500, trebled the level, as high as for wild adults. Oil-supplemented diets improved growth, as judged by bigger pupae and increased female adult longevity, and flight mill studies provided some evidence that improved EPA status improved flight. Although the phenotypic contribution to mating inferiority of laboratory-reared mosquitos remains unclear, this work illustrates how an apparently satisfactory stock rearing regimen may he cryptically suboptimal with respect to an essential nutrient. Resume Importance des acides gras fondamentaux dans le regime larvaire classique enrichi en huiles de poisson chez Culex tarsalis eleve au laboratoire Les souches de laboratoire de moustiques sont generalement conservees en utilisant un regime larvaire brut tel que pâtee pour animaux domestiques, levure dessechee, poudre de foie, etc. Les mâles de C. tarsalis eleves de la sorte se sont reveles defavorises dans la competition sexuelle avec des mâles sauvages dans la nature, lors d'experiences sur l'utilisation de mâles steriles dans la lutte contre les moustiques, meme si la competition a eu lieu apres un seul cycle larvaire en elevage au laboratoire. Les adultes provenant de ces elevages avaient une teneur en acide eicosapentaenoique (EPA), – acide gras essentiel-, beaucoup plus faible que les adultes provenant de la nature. En envisageant qu'une teneur suboptimale en acides gras essentiels pouvait diminuer la vigueur des adultes, nous avons tente d'augmenter la teneur en EPA des tissus de C. tarsalis eleves au laboratoire en completant le regime avec des huiles de poisson qui sont riches en EPA et en acides gras polyinsatures n3 apparentes. L'addition d'huile de foie de morue double la teneur des tissus en phospholipides EPA par rapport aux temoins, et la specialite Walgreen EPA 500, triple la teneur en EPA, la mettant au niveau des adultes de la nature. Les regimes completes en huile ont ameliore la croissance (pupes plus grosses et longevite des femelles accrue), et quelques etudes en moulin a vol ont montre que l'amelioration de la teneur en EPA modifiait les caracteristiques du vol. Bien que ce travail n'ait pas permis de clarifier la part phenotypique de l'inferiorite des mâles des moustiques eleves au laboratoire, son interet general a ete de montrer comment un regime apparemment satisfaisant peut etre en realite suboptimal en ce qui concerne un aliment essentiel.