Advanced Larval Stages Research Articles

Effects of dissolved carbon dioxide on growth and vertebral column of hybrid marine grouper (Epinephelus fuscoguttatus × E. lanceolatus) early advanced larvae

This study investigated the effects of different dissolved carbon dioxide (CO2) concentrations (400, 700, and 1000 ppm) on the growth and vertebral column formation of hybrid tiger grouper × giant grouper (TG × GG) in their advanced larval stage under controlled laboratory conditions for 12 weeks. Growth parameters, including specific growth rate (SGR), survival rate, food consumption (FC), and food conversion rate (FCR), were calculated at the end of the experiment. Vertebral column formation was analysed using X-radiography and osteology methods. The results showed that all growth parameters were significantly affected by CO2 concentration, with the best performances observed under 400 ppm CO2. The highest statistically significant (p < 0.05) SGR, survival rate, and FC were observed under 400 ppm CO2, whereas the lowest was observed under 1000 ppm CO2. The lowest FCR (0.40, p < 0.05) was observed in 400 ppm CO2 and the highest was observed at 1000 ppm CO2 (0.59, p < 0.05). Furthermore, larvae without vertebral column malformations were observed in 400 ppm CO2, while larvae with small angles of kyphosis were observed in 700 ppm CO2, and larvae with kyphosis, lordosis, and vertebral compression were observed in 1000 ppm CO2. Only six spine measurements out of 31 obtained under different CO2 concentrations were significantly different (p < 0.05). Overall, the results suggest that CO2 concentration plays a crucial role in the growth and vertebral column formation of TG × GG in their advanced larval stage. The optimal CO2 concentration for the aquaculture of TG × GG in their advanced larval stage was found to be 400 ppm or lower. This study highlights the importance of maintaining optimal CO2 concentrations to enhance the growth and health of fish in aquaculture systems.

Determination of Almond Saw Fly (Cimbex quadrimaculata Müller, 1766, hymenoptera: cimbicidae)’s larval development time in controlled conditions

The study was conducted to compare the larval development stages, cocoon knitting and cocoon completion of Cimbex quadrimaculata (Müller, 1766) (Hymenoptera: Cimbicidae) in climate cabinets where 65% humidity, 25C ± 2 °C and 30C ± 2 °C temperature and 16:8 illumination conditions are provided. A statistically significant difference was found between 25 ºC and 30 ºC in terms of larval development times. It has been determined that as the temperature increases, the duration of the advanced larval stages shortens, and at 30 ºC, it has been observed that the larval development stages, cocoon knitting and full cocoon time are statistically shorter. These data have the characteristics of being the basis study for determining the biology of the pest under controlled conditions. The data of the study is important in terms of the bioecology and control of the pest.

Light Trapping Reveals Multiple Bigheaded Carp Spawns Upstream of Lock and Dam 19 in the Upper Mississippi River

AbstractThe Silver Carp Hypophthalmichthys molitrix and Bighead Carp H. nobilis are two species of invasive bigheaded carp currently invading North American rivers and watersheds. Bigheaded carp were accidentally introduced into the lower Mississippi River basin in the early 1970s and have since invaded many water bodies in the Midwestern United States. Evidence of bigheaded carp reproduction and recruitment in the upper Mississippi River upstream of Lock and Dam 19 (LD19) at Keokuk, Iowa, thought to be a critical constriction point to their upstream establishment, has been limited to a few isolated detections of eggs, larvae, and juvenile life stages since 2012. Therefore, a more comprehensive assessment of bigheaded carp reproduction in this critical management zone was needed. We used quadrafoil light traps (n = 1,387) deployed during May–September 2016–2018 in Pools 17–19 of the Mississippi River to monitor for advanced larval bigheaded carp in low‐velocity habitats. Throughout the sampling period, we captured 1,747 larval and 35 postlarval bigheaded carp (N = 1,782). Bigheaded carp were collected on 15 sampling events that spanned from May 31, 2016, to September 13, 2018, with associated hatch dates estimated to represent 10 unique reproductive events from May 2016 to September 2018. The individual captures and backdated hatch estimates revealed a protracted spawning period of up to seven events in 2016, one event in 2017, and two events in 2018. Bigheaded carp were only captured in Pool 19, possibly due to the drifting requirements for egg maturation and the low‐velocity downstream reach of Pool 19. This research provides confirmation that bigheaded carp spawned upstream of LD19 are capable of transitioning past the yolk sac stage upstream of this bottleneck to more advanced larval stages. Knowledge of reproduction and larval retention and the field‐based evidence of protracted spawning fill critical research gaps needed for the management of bigheaded carp.

Interactive effects of increased temperature and gadolinium pollution in Paracentrotus lividus sea urchin embryos: a climate change perspective

Gradual ocean warming and marine heatwaves represent major threats for marine organisms already facing other anthropogenic-derived hazards, such as chemical contamination in coastal areas. In this study, the combined effects of thermal stress and exposure to gadolinium (Gd), a metal used as a contrasting agent in medical imaging which enters the aquatic environment, were investigated in the embryos and larvae of the sea urchin Paracentrotus lividus. Embryos were exposed to six treatments of three temperatures (18 °C, 21 °C, 24 °C) and two Gd concentrations (control: 0 μM; treated: 20 μM). With respect to developmental progression, increased temperature accelerated development and achievement of the larval stage, while Gd-exposed embryos at the control temperature (18 °C) showed a general delay in development at 24 h post-fertilization (hpf), and a stunting effect and impaired skeleton growth at 48 hpf. Elevated temperatures at near-future projections (+3 °C, 21 °C) reduced the negative effects of Gd on development with a lower percentage of abnormality and improved skeleton growth. Combined extreme warming at present-day marine heatwave conditions (+6 °C, 24 °C) and Gd treatment resulted in a lower proportion of embryos reaching the advanced larval stages compared to the 21 °C + Gd. At the molecular level, western blot analysis showed that Gd was the main driver for the induction of heat shock protein (HSP60, HSP70) expression. At 48 hpf, temperature increase was the main driver for activation of additional cellular stress response strategies such as autophagy and apoptosis. Combined treatments showed the induction of HSP60 at 24 hpf and autophagic and apoptotic processes at 48 hpf. Treatments having low levels of HSPs expression showed high levels of apoptosis, and vice versa, clearly demonstrating the antagonistic effects of HSPs expression and apoptosis. Detection of fragmented DNA in apoptotic nuclei showed selective apoptosis, likely in extremely damaged cells. Our results indicate that the negative effects of Gd-exposure on P. lividus larval development and biomineralization will be mitigated by a near-future ocean warming, up to a thermotolerance threshold when negative synergistic effects were evident. Our data highlight the use of biomarkers as sensitive tools to detect environmental impacts as well as the need for a better understanding of the interactions between the multiple stressors faced by marine species in coastal environments.

A novel cell-free method to culture Schistosoma mansoni from cercariae to juvenile worm stages for in vitro drug testing.

BackgroundThe arsenal in anthelminthic treatment against schistosomiasis is limited and relies almost exclusively on a single drug, praziquantel (PZQ). Thus, resistance to PZQ could constitute a major threat. Even though PZQ is potent in killing adult worms, its activity against earlier stages is limited. Current in vitro drug screening strategies depend on newly transformed schistosomula (NTS) for initial hit identification, thereby limiting sensitivity to new compounds predominantly active in later developmental stages. Therefore, the aim of this study was to establish a highly standardized, straightforward and reliable culture method to generate and maintain advanced larval stages in vitro. We present here how this method can be a valuable tool to test drug efficacy at each intermediate larval stage, reducing the reliance on animal use (3Rs).Methodology/Principal findingsCercariae were mechanically transformed into skin-stage (SkS) schistosomula and successfully cultured for up to four weeks with no loss in viability in a commercially available medium. Under these serum- and cell-free conditions, development halted at the lung-stage (LuS). However, the addition of human serum (HSe) propelled further development into liver stage (LiS) worms within eight weeks. Skin and lung stages, as well as LiS, were submitted to 96-well drug screening assays using known anti-schistosomal compounds such as PZQ, oxamniquine (OXM), mefloquine (MFQ) and artemether (ART). Our findings showed stage-dependent differences in larval susceptibility to these compounds.ConclusionWith this robust and highly standardized in vitro assay, important developmental stages of S. mansoni up to LiS worms can be generated and maintained over prolonged periods of time. The phenotype of LiS worms, when exposed to reference drugs, was comparable to most previously published works for ex vivo harvested adult worms. Therefore, this in vitro assay can help reduce reliance on animal experiments in search for new anti-schistosomal drugs.

Per offspring investment implications for crustacean larval development: evolutionary insights into endotrophy and abbreviated development

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 493:207-217 (2013) - DOI: https://doi.org/10.3354/meps10496 Per offspring investment implications for crustacean larval development: evolutionary insights into endotrophy and abbreviated development Andrew Oliphant*, Sven Thatje Ocean and Earth Science, University of Southampton, Southampton SO14 3ZH, UK *Email: andrew.oliphant@noc.soton.ac.uk ABSTRACT: At the inter-specific level, per offspring investment (POI) is associated with larval development mode and follows a macro-ecological trend within the marine environment; higher POI and its associated greater degree of endotrophy and abbreviated development is found in cooler, high latitude regions. Here, the implications of between-brood-variation in hatchling energy content (measured as carbon mass) on larval starvation resistance and developmental plasticity within the caridean shrimp Palaemonetes varians were assessed. Results demonstrate that greater POI provides increased endotrophy and the potential for abbreviated development. In the absence of food, P. varians larvae from broods of higher hatchling energy content developed to more advanced larval stages and survived for longer before succumbing to starvation. In the presence of food, P. varians larvae from broods of higher hatchling energy content developed through fewer larval instars, showed higher growth rates, and had shorter development times. Also, for larvae developing through the same number of larval instars, larvae from broods of higher hatchling energy content developed to greater juvenile dry weight. These data support the hypothesis that macro-ecological trends in development mode are driven by inter-specific variations in POI. At the intra-specific level, phenotypic plasticity allows for environmentally mediated variations in POI. Under differential selection pressures, this flexibility may, thus, eventually permit the evolution of the diverse and complex life cycles observed in the marine environment. KEY WORDS: Carry-over effects · Evolution of lecithotrophy · Larval ecology · Palaemonidae · Palaemonetes varians · POI Full text in pdf format PreviousNextCite this article as: Oliphant A, Thatje S (2013) Per offspring investment implications for crustacean larval development: evolutionary insights into endotrophy and abbreviated development. Mar Ecol Prog Ser 493:207-217. https://doi.org/10.3354/meps10496 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 493. Online publication date: November 20, 2013 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2013 Inter-Research.

Distribution and abundance of Heterocarpus reedi Bahamonde, 1955, Cervimunida johni Porter, 1903, and Pleuroncodes monodon (H. Milne Edwards, 1837), larvae off Coquimbo and Caldera, Chile

To better understand the population dynamics of fishery resource species, 160 zooplankton samples were obtained with a Bongo net at 40 oceanographic stations around Caldera and Coquimbo in October and December, 2005, and analyzed. All crustacean decapod larvae were sorted, and Heterocarpus reedi, Cervimunida johni, and Pleuroncodes monodon larvae were identified. For all three species, the highest abundances of early zoea were found in October in Coquimbo, whereas advanced larval stages were predominant in December. In Caldera, advanced larval stages of H. reedi and P. monodon, and early zoeas of C. johni were dominant during both sampling months. The frequency of occurrence of H. reedi larvae was similar during both sampling months in Coquimbo and greater in October in Caldera. The frequency of occurrence of the larvae of P. monodon and C. johni was greater in both areas in October. All the megalops captured in both zones and sampling months corresponded to a single morphotype, with morphological characteristics similar to the smallest P. monodon juvenile specimens. Based on the larval distribution and abundance of these three species, it is postulated that spawning occurs earlier in the Caldera area than around Coquimbo, mainly in areas near the coast, given the differences in abundance of the developmental stages.

Ultrastructural changes in the advanced third larval stage of Gnathostoma binucleatum Almeyda-Artigas, 1991 (Nematoda: Spirurida) following albendazole and albendazole sulfoxide in vitro exposure

We report here the ultrastructural changes in the third advanced larval stage (AL3) of Gnathostoma binucleatum Almeyda-Artigas, 1991, induced by in vitro treatment with albendazole and the metabolite albendazole sulfoxide. During the whole period of the experiment, the controls remained active and vital throughout the 108-h exposure period. The primary site of action of both drugs appears to be the mitochondria and myofibrils of the polymyarian musculature. Degenerative changes in the secretory portion of the esophagus and somatic musculature were clearly observed. These degenerative changes, leading to complete muscular and glandular necrosis, were interpreted as the consequence of drug-induced blockade of metabolic energy production. Cuticular disruption had also been observed in the experimental groups. We observed a dramatic reduction in the number of mitochondria and muscle fibers, as well as the formation of large autophagic vesicles as result of an irreversible degenerative phenomenon. The passive cutaneous elimination of larvae in human infections is probably a consequence of parasite immobility, due to the effects of this antihelminthic drug.

Effect of thermal stress on survival and delay of metamorphosis in larvae of the purple sea urchin Strongylocentrotus purpuratus

The effect of thermal stress (heat shock) on survival was evaluated for advanced larval stages and the possible effect on delay of metamorphosis in competent larvae was also evaluated in the purple sea urchin Strongylocentrotus purpuratus under laboratory conditions. Eight-arm precompetent and competent larvae were kept at 15, 19, 23, 28, and 31 ºC during 24 h to estimate their thermal tolerance and measure their survival in each treatment. Delay of metamorphosis was evaluated in competent larvae exposed to heat shock treatments of 15, 20, 24, 28, and 32 ºC for 30 min. After this, larvae were induced to metamorphose in the presence of biofilms and KCl. Our results indicated that the thermal tolerance limit for precompetent and competent larvae was 27 ºC; temperatures equal or above this value are lethal for both stages of development, where we observed 100% mortality in a period of 24 h for the treatment at 27 ºC and of 2 h at 31 ºC. Competent larvae subjected to a heat shock treatment of 28 ºC for 30 min delayed the onset of metamorphosis (&lt;40%) and showed high percentage of larvae with incomplete metamorphosis (55%). These results indicate the sensitivity of late larval stages to temperatures above 27 ºC for short periods of time, and that this sensitivity may compromise the onset of metamorphosis. This could have some effect on the settlement and recruitment patterns of the purple sea urchin, particularly in intertidal sites exposed to high temperatures during the summer.

On the simple and economical rearing method (kasso-iku) of silkworms in advanced larval stages

On the simple and economical rearing method (kasso-iku) of silkworms in advanced larval stages

Experimental vertical transmission of Macrobrachium rosenbergii nodavirus (MrNV) and extra small virus (XSV) from brooders to progeny in Macrobrachium rosenbergii and Artemia

White tail disease (WTD) is a serious problem in hatcheries and nursery ponds of Macrobrachium rosenbergii in India. Experiments were carried out to determine the possibility of vertical transmission of M. rosenbergii nodavirus (MrNV) and extra small virus (XSV) in M. rosenbergii and Artemia. Prawn broodstock inoculated with MrNV and XSV by oral or immersion challenge survived without any clinical signs of WTD. The brooders spawned 5-7 days after inoculation and the eggs hatched. The survival rate of larvae gradually decreased, and 100% mortality was observed at the post-larvae (PL) stage. Whitish muscle, the typical sign of WTD, was seen in advanced larval developmental stages. The ovarian tissue and fertilized eggs were found to be positive for MrNV/XSV by reverse transcriptase-polymerase chain reaction (RT-PCR) whereas the larval stages showed positive by RT nested PCR (nRT-PCR). In Artemia, reproductive cysts and nauplii derived from challenged brooders were normal and survival rates were within the expected range for normal rearing conditions. The reproductive cysts were found to be positive for MrNV/XSV by RT-PCR whereas the nauplii showed MrNV/XSV-positive by nRT-PCR. The PL of M. rosenbergii fed nauplii derived from challenged Artemia brooders died at 9 days post-inoculum with clinical signs of WTD.

Preliminary investigation on the effects of biological and synthetic insecticides on large white butterfly (Pieris brassicae L.) larvae

Control of cabbage pests is oriented towards the use of efficient but high-risk insecticides, some of them being endocrine disruptors. Biopesticides are more environment-friendly, operator-and consumers-safe, but they have low initial toxicity, low efficacy to advanced larval stages, and they require certain knowledge of pest and host biology. In our laboratory experiments we have investigated the effects of formulated synthetic pyrethroid cypermethrin (0.3 l/ha) and biological products - formulations based on Bacillus thuringiensis subsp. kurstaki (2 and 3/ha) and Spinosad (0.1 l/ha) - on large white butterfly (Pieris brassicae L.) larvae-instars 2, 3, 4 and 5. The effect of insecticides was inversely proportional to larval instars. Btk effect could be improved if tank-mixed with cypermethrin. The mixing of ready-made products allows a reduction 3 and 6 times compared with the recommended dose, still obtaining satisfactory results. Rate of leaf damage was reduced when tank mixtures were used. Use of two products in mixture would be of significance especially for control of advanced late instars late in season, when Btk action alone is insufficient. Spinosad was effective in inducing mortality and reducing leaf damage by all larval instars, therefore we assume that the dose could be reduced. Feeding rate and mortality are equally important parameters when assessing biopesticide efficacy. This strategy should also reduce the possibility of inducing resistance in pest population. It also tends to reduce the residues in commodities and is good solution in production of hygienic and health safe food.

Synoptic distribution of crab larvae near the mouth of Delaware Bay: Influence of nearshore hydrographic regimes

In this paper we describe results of a study designed to test the hypothesis that coastal regions with weak subtidal flow (i.e., coastal null zones) may serve as retention areas for estuarine larval forms. Our investigation assessed the distribution of 3 taxa of crab larvae ( Callinectes sapidus, Uca spp., and Hexapanopeus angustifrons) within a 200-km 2 region encompassing the mouth of Delaware Bay (ca. 39° N, 75° W). Previous studies had shown that larvae of C. sapidus and Uca spp. are exported to the coastal ocean, while larvae of H. angustifrons are retained within the estuary. In the present investigation, we conducted simultaneous plankton tows at 3 stations during peak spawning season. Samples were collected from a depth of 1 m every 30 min throughout a complete tidal cycle. One station was located 15 km within the bay and was subjected to strong flow at tidal frequency. A second station was located within a southward-flowing coastal current near the southern terminus of the bay at Cape Henlopen. A final station was located in a coastal area of weak subtidal flow near Cape May at the northern terminus of the bay. Results provide a unique synoptic view of larval distributions in 3 distinct hydrographic regimes in the mouth of a major estuary. The coastal-current station was characterized by low concentrations of newly hatched C. sapidus and Uca zoeae, while the null-zone station had high densities of both early and advanced larval stages of these two taxa. In contrast, the station located within the bay had few C. sapidus or Uca zoeae and was dominated by both early and advanced stages of the mud crab H. angustifrons. These data provide clear evidence for the retention of exported larval forms in a coastal null zone associated with the circulation of a large estuary and thus are consistent with our hypothesis.

Effects of Bt‐toxin Cry1Ac on Propylaea japonica Thunberg (Col., Coccinellidae) by feeding on Bt‐treated Bt‐resistant Helicoverpa armigera (Hübner) (Lep., Noctuidae) larvae

Abstract: Propylaea japonica is an important predatory insect of common cotton pests. To assess the ecological effects of transgenic Bt cotton, expressing Cry1Ac toxin, on this predator, we examined the life history parameters of P. japonica for two generations by feeding them with Bt‐resistant Helicoverpa armigera. After ingesting Bt‐treated Bt‐resistant H. armigera larvae in the third and fourth instar, the body mass and body length of adult P. japonica decreased, a combined effect of poor prey quality and Cry1Ac Bt‐toxin may account for these effects. However, larval survivorship and development in these two instars, pupal mortality, fecundity and adult longevity of P. japonica were not affected in both the generations. These results suggest that ingesting Bt‐toxin Cry1Ac‐treated pests in advanced larval stage might have no significant effect on the fitness of predator P. japonica.

Tonic fibres in axial muscle of cyprinid fish larvae: their definition, possible origins and functional importance.

Teleost fish are known to develop small populations of muscle fibres that are assumed to be tonic in nature although their contractile properties and many other characteristics remain unknown. Here we attempt to resolve some of the ambiguity and confusions surrounding the definition and functional role of tonic fibres in teleosts and provide new information on their ontogeny. We investigate the differentiation of tonic muscle fibres in three species of cyprinid fish using electron microscopy, histochemistry, immunohistochemistry and in situ hybridization. The fine structure of the fibres defined as tonic in the larvae used in this study complies with patterns known from studies in teleost adults. This allows formal definition of tonic fibres in cyprinid larvae. The tonic fibres may be recognized by a variety of features: (1) by their characteristic position along the medial confines of the red muscle insertion at the horizontal septum, (2) their fine structure, including solid clusters of irregularly cleaved myofibrils, thick and wavy Z-lines, and T-tubules at the A-band/I-band transitions, (3) their histochemical features, specifically weak but obvious staining for mATPase after alkaline preincubation, and lack of SDH activity in the more advanced larval stages, (4) their unique immunological properties, being the only fibre type in the myotome that reacts with a serum against chicken tonic myosin (anti- T2). Expression of tonic characters usually begins within a few fibres in the dorsal domain of the superficial red muscle insertion at the horizontal septum and hence involves a high degree of dorso-ventral polarity. The present evidence indicates that tonic fibres arise from separate myogenic stem cells rather than by transdifferentiation from existing red fibres. First appearance of tonic fibres during ontogeny correlates closely with the onset of free swimming and exogeneous feeding. We use this fact to argue that tonic fibres are probably a prerequisite for efficient locomotory control during prey capture, shoaling and predator avoidance.

Ergastoplasmic paracrystalline inclusion bodies in the adipose gonadal envelope and fat body of the glow worm, Lampyris noctiluca (Insecta, Coleoptera)

The gonads of glow worm larvae are enveloped by adipose tissue which represents a specialized fat body. The adipose gonadal envelope, and also to a lesser extent the fat body cells, contain tubular paracrystalline inclusion bodies (PIBs). Cells of other tissues are devoid of such inclusions. The PIBs form in the cisternae of rough ER. In young larvae PIB formation is sparse, but at advanced larval stages PIBs often occur as bundles in stacks of ergastoplasm. Typically, a PIB within a cisterna consists of four to seven parallel tubules. The outer diameter of a tubule is ca 28.8 nm and the width of the tubule lumen ca 12.2 nm. The “wall” of a tubule contains globular protein subunits of ca 8.3 nm diameter; the subunits are arranged helically. Since the adipose gonadal envelope progresses through a cytological differentiation process during differentiation and maturation of the gonads, the increased number of PIBs may indicate enhanced metabolic activity of the tissue related to nutrition of the growing gonads.

LARVAL DEVELOPMENT OF AUSTROPANDALUS GRAYI (CUNNINGHAM, 1871) (DECAPODA, CARIDEA, PANDALIDAE) FROM THE SOUTHWESTERN ATLANTIC OCEAN

Austropandalus grayi and Pandalopsis ampla are the only members of the Pandalidae recorded from coastal waters of Argentina. The identie cation of planktonic larvae of A. grayi from the southwestern Atlantic and the Magellan Region was cone rmed by comparing stage I zoeae with larvae hatched in the laboratory. Zoeal stages I-V and an advanced larval stage were distinguished, and their morphology and distribution are described. The phylogenetic relations of pandalid larvae and the position of A. grayi in the family are discussed.

Changing surface antigen and carbohydrate patterns during the development of Oesophagostomum dentatum.

Living and fixed specimen of Oesophagostomum dentatum were labelled in situ with serum antibodies or a panel of biotin-labelled lectins. Specific binding of antibodies was observed in all parasitic stages--freshly exsheathed 3rd-stage larvae (L3), 3rd- and 4th-stage (L4) larvae cultured in vitro and L3 and L4 and adults isolated from pig intestines. The shedding of the stained layer by motile larvae was inhibited by levamisole-induced paralysis. Larvae cultured in vitro exposed serum-derived proteins on their surface which could be labelled with secondary antibody directed against the respective serum donor species. While freshly exsheathed larvae were recognized by O. dentatum-positive serum only, older larvae and adults cross-reacted with serum from pigs infected with O. quadrispinulatum, a closely related species. Lectin binding varied considerably between stages. While binding was not observed in pre-parasitic stages, Concanavalin A, Soybean Agglutinin, Wheat Germ Agglutinin, Ricinus communis Agglutinin and Peanut Agglutinin bound to developing larvae in varying degrees. Dolichos biflorus Agglutinin only bound to advanced (luminal) larval stages, while adults generally displayed only weak or partial lectin binding (except with Concanavalin A and Wheat Germ Agglutinin). Ulex europaeus Agglutinin only labelled larvae derived from cultures containing 10% pig serum. Cleavage of the carbohydrate residues by sodium periodate treatment resulted in reduction of antibody binding to cultured larvae, but not to freshly exsheathed L3. Concanavalin A, Soybean Agglutinin, and Peanut Agglutinin binding was also reduced by periodate treatment, while binding of Wheat Germ Agglutinin and Ricinus communis Agglutinin was inhibited only in early L3, but not in older stages. The different lectin labelling patterns are related to the different stages of the nematode--infective, invasive, histotropic, and luminal--and may serve as a mode of adaptation for the parasite against the host's immune attack by surface glycoprotein variation, together with antigen shedding (as demonstrated by labelling of motile larvae) and a possible acquisition of host molecules at the parasite's surface. Furthermore, a possible role of this developmental variation in surface carbohydrates in parasite-parasite interactions is discussed.

Energy metabolism during embryonic development and larval growth of an Antarctic sea urchin.

Developmental energetics of an Antarctic sea urchin, Sterechinus neumayeri, were quantified to describe the physiological bases underlying ontogenetic changes in metabolic rate at extreme cold temperatures (-1.5 degrees C). Rates of development from a four-arm to a six-arm larval stage were not affected by food availability. The respiratory cost of development to the six-arm larval stage (day 60) was 14.0 mJ for fed larvae and 8.2 mJ for unfed larvae. We observed three phases of metabolic regulation during development. During embryogenesis (day 0-22), increasing metabolic rates were proportional to increases in cell numbers. During early larval development (day 22-47), the differences in respiratory rate between fed and unfed larvae were not accounted for by cell number, but by cell-specific metabolic rate (respiratory rate normalized to DNA content). Once an advanced larval stage had been reached (day 47-60), cell-specific respiratory rate and mitochondrial densities (citrate synthase activity normalized to DNA content) were more equivalent between fed and unfed larvae, suggesting that size-specific metabolic rates were determined at a level of physiological regulation that was independent of cell numbers or feeding history.

The tadpole of the endemic Corsican painted frog Discoglossus montalentii (Anura, Discoglossidae)

The tadpole of the endemic Corsican painted frog Discoglossus montalentii Lanza, Nascetti, Capula & Bullini, 1984 is described on the basis of two samples obtained in captivity from in‐traspecific breeding. Tadpoles of this species possess a ventral spiraculum, dorsal eyes and nares, and a relatively long tail which is rounded at the end. The oral disk is completely bordered by a single series of marginal papillae and, in advanced larval stages (i.e., from stage 35), the two anterior and the three posterior ker‐atodont rows usually comprise three or four subrows. In Corsica, where D. montalentii and D. sardus are often found in syntopy, the identification of their tadpoles appears relatively easy only if the developmental stage is taken into account: the tadpole of D. montalentii always possesses a complete series of marginal papillae, a higher total number of keratodont subrows, a larger body size, and a differently shaped tail. These characters permit identification of Corsican Discoglossus tadpoles. The results have important implications for both in ecological and management strategies necessary to the preservation of the endemic Corsican painted frog.