Postlarval Stages Research Articles

The complete larval development of Pagurus lanuginosus De Haan, 1849(Decapoda, Anomura, Paguridae) reared in the laboratory, with emphasis on the post-larval stage.

The complete larval development of Pagurus lanuginosus is described and illustrated including the first description of the post-larval stage. Specimens were reared in the laboratory at 15°C and 33.5-35.02 PSU. Newly hatched larvae passed through a short prezoeal stage (10 minutes to 2 hours), four zoeal stages (6, 6, 6, 8 days), and one megalopal stage (10 days). We compared the morphological features of each larval stage with those of the preceding two descriptions on the same species, and found many differences in morphology and the duration between zoeal stages. We concluded that significant diagnostic characters separating this species from other congeners in Japanese waters include the presence of two pairs of yellowish chromatophores on the carapace in the zoeal stages, a translucent body flecked with red chromatophores, and two pairs of red chromatophores on the carapace in the megalopal stage.

Climate variability and spatiotemporal dynamics of five Southern Ocean krill species

Understanding the ecological response of marine organisms to future climate change will benefit from quantifying spatiotemporal aspects of their distribution and abundance as well as the influence of ocean–atmospheric climate modes on their population cycles. Our study provides a synthesis of 18years of data (1992–2009) for 5 krill (euphausiid) species monitored near the North Antarctic Peninsula (NAP) during austral summer. Distribution and abundance data are presented for postlarval stages of Euphausia crystallorophias, E. frigida, E. superba, E. triacantha and Thysanoessa macrura and larval E. superba and T. macrura. Intraseasonal, interannual and longer-term distribution and abundance patterns are quantified relative to climate modes driving ecosystem variability off the Antarctic Peninsula: El Niño-Southern Oscillation (ENSO), Southern Annual Mode (SAM) and associated zonal and meridional winds. Interannual abundance variations of all 5 species are significantly correlated with seasonally averaged ENSO indices and, with the exception of E. triacantha, elevated population sizes are associated with the higher productivity La Niña phase. Time-lagged responses of each species to ENSO indices approximate their generation times and suggest evolution of their life histories and reproductive efforts in accordance with the ENSO cycle. Postlarval E. crystallorophias and E. frigida and larval T. macrura demonstrate significant abundance increases after 1998 associated with a shift from an El Niño dominated period to predominantly La Niña and “Nino-neutral” conditions. Seasonal changes in species distributions and co-occurrence indicate portions of the southernmost E. frigida, E. triacantha and T. macrura populations move poleward with E. superba during late-summer, suggesting that environmental conditions associated with sea ice development (e.g., food, retention) may be more favorable than within the Antarctic Circumpolar Current during low productivity seasons. Spatial distributions of larval and postlarval T. macrura suggest 2 separate spawning populations within oceanic and coastal waters. Lastly, mean euphausiid species concentrations and abundance relationships encountered during 1992–2009 are remarkably similar to those reported for the Antarctic Peninsula during the 1928–1935 Discovery Investigations. Circumpolar observations of E. superba “superswarms” associated with a major climatically related ecosystem change in the late 1970s may have represented an episodic period of anomalous peak abundance. Subsequent abundance estimates compared to these anomalies would indicate a significant decrease, but should not be taken to reflect the impact of climate warming.

Myoinhibitory peptide regulates feeding in the marine annelid Platynereis.

BackgroundDuring larval settlement and metamorphosis, marine invertebrates undergo changes in habitat, morphology, behavior and physiology. This change between life-cycle stages is often associated with a change in diet or a transition between a non-feeding and a feeding form. How larvae regulate changes in feeding during this life-cycle transition is not well understood. Neuropeptides are known to regulate several aspects of feeding, such as food search, ingestion and digestion. The marine annelid Platynereis dumerilii has a complex life cycle with a pelagic non-feeding larval stage and a benthic feeding postlarval stage, linked by the process of settlement. The conserved neuropeptide myoinhibitory peptide (MIP) is a key regulator of larval settlement behavior in Platynereis. Whether MIP also regulates the initiation of feeding, another aspect of the pelagic-to-benthic transition in Platynereis, is currently unknown.ResultsHere, we explore the contribution of MIP to the regulation of feeding behavior in settled Platynereis postlarvae. We find that in addition to expression in the brain, MIP is expressed in the gut of developing larvae in sensory neurons that densely innervate the hindgut, the foregut, and the midgut. Activating MIP signaling by synthetic neuropeptide addition causes increased gut peristalsis and more frequent pharynx extensions leading to increased food intake. Conversely, morpholino-mediated knockdown of MIP expression inhibits feeding. In the long-term, treatment of Platynereis postlarvae with synthetic MIP increases growth rate and results in earlier cephalic metamorphosis.ConclusionsOur results show that MIP activates ingestion and gut peristalsis in Platynereis postlarvae. MIP is expressed in enteroendocrine cells of the digestive system suggesting that following larval settlement, feeding may be initiated by a direct sensory-neurosecretory mechanism. This is similar to the mechanism by which MIP induces larval settlement. The pleiotropic roles of MIP may thus have evolved by redeploying the same signaling mechanism in different aspects of a life-cycle transition.Electronic supplementary materialThe online version of this article (doi:10.1186/s12983-014-0093-6) contains supplementary material, which is available to authorized users.

Prevalence and quantification of pathogenic Vibrio parahaemolyticus during shrimp culture in Thailand.

Vibrio parahaemolyticus is a major cause of seafood-borne gastroenteritis. The human pathogenic strains possess tdh or trh or both genes. In Thai shrimp farming, the level of pathogenic V. parahaemolyticus contamination has not been completely characterized, although it has been identified as a risk for people who consume undercooked shrimp. In this study, the prevalence and concentration of V. parahaemolyticus (total Vp) and pathogenic V. parahaemolyticus (tdh+ Vp and trh+ Vp) were investigated during shrimp culture cycles using the most probable number (MPN) method and were confirmed by PCR and the loop-mediated isothermal amplification (LAMP) techniques. The prevalence and concentration of total Vp were high in broodstock and egg samples at the start of the hatchery cycle, but the organism decreased in the subsequent larval and postlarval stages. In contrast, total Vp was low at the beginning of the pond cycle and dramatically increased during the later stages of culture. Broodstock and fresh feed were important sources of V. parahaemolyticus. Numbers of tdh+ Vp and trh+ Vp detected by the LAMP technique were much greater than those detected by the PCR technique, especially in the late stages of the pond cycle. A direct correlation between total Vp and pathogenic Vp was demonstrated only during the harvest stage. This study will be useful as a guideline to establish levels of V. parahaemolyticus presence which can be considered as safe during shrimp culture. In addition, it could be used to identify the source of V. parahaemolyticus, which has recently been reported to be one of the etiologic agents of acute hepatopancreatic necrosis disease.

Crecimiento y supervivencia de larvas D, pedivéligeras y postlarvas de Gari solida (Mollusca: Psammobiidae), provenientes de reproductores acondicionados

Adults of Gari solida were maintained at a room temperature of around 14°C for approximately 90 days, fed with a microalgae mix 300,000 cell ml-1, after which spawning was induced in 20 specimens. The oocytes obtained were fertilized at a 10:1 sperm/oocyte ratio and the embryos were incubated in a specially designed system (`hatching system') for a period of 96 h, until D-shape larvae without gelatinous coating were obtained. Larval culture was undertaken in cylindrical 200 L tanks at 13 ± 1.3°C, with seawater filtered to 1 µm and UV irradiation, at an initial density of 9.7 larvae ml-1, with water renewal every 2-3 days; D-shape larvae were fed with Isochrysis aff. galbana and throughout the umbonate, pediveliger and postlarval stages, with a mix of Isochrysis aff. galbana and Chaetoceros calcitrans (7:3), where concentration was proportioned in accordance with culture density. The umbonate larval stage was detected at day 11 of culture and the pediveliger stage, at day 22, starting from the free-swimming D-shape larvae. Metamorphosis was induced with an epinephrine bath at 0.005 N concentration and postlarvae obtained at day 26 of culture were subsequently cultured up to day 35. Average sizes reached were 122 ± 13 µm, 158 ± 12 µm, 185 ± 5 µm and 216 ± 24 µm for the `D', umbonate, pediveliger and postlarval stages, respectively. Survival up to postlarvae stage was 0.005%. Development of G. solida larvae and postlarvae culture is in its initial phases and improvements in all stages are necessary, from breeder conditioning onwards.

Morphological Development of Larvae and Juveniles of Acanthopagrus schlegeli

ABSTRACTNewly hatched black porgy larvae (Acanthopagrus schlegeli) swam to the surface, with the mouth and anus still closed and were 1.90–2.11 mm (mean, 2.0 mm) in total length (TL). The larvae were 2.71–2.94 mm TL (mean, 2.82 mm) on day 2 after hatching. At this time, about two-thirds of the yolk was absorbed, the bladder and intestines had formed, and the mouth and anus were open. Total length was 4.32–4.66 mm (mean, 4.45 mm) at the post-larval stage on days 5–6 after hatching, and the yolk and oil globule were almost absorbed. The end of the notochord began to flex, and 6–8 caudal fin rays were visible. The larvae were 15.37–16.1 mm TL (mean, 15.83 mm) at the juvenile stage on days 30–32 after hatching, and the number of rays in all fins was completely revealed.

Morphological Development of Larvae and Juveniles of Acanthopagrus schlegeli.

Newly hatched black porgy larvae (Acanthopagrus schlegeli) swam to the surface, with the mouth and anus still closed and were 1.90-2.11 mm (mean, 2.0 mm) in total length (TL). The larvae were 2.71-2.94 mm TL (mean, 2.82 mm) on day 2 after hatching. At this time, about two-thirds of the yolk was absorbed, the bladder and intestines had formed, and the mouth and anus were open. Total length was 4.32-4.66 mm (mean, 4.45 mm) at the post-larval stage on days 5-6 after hatching, and the yolk and oil globule were almost absorbed. The end of the notochord began to flex, and 6-8 caudal fin rays were visible. The larvae were 15.37-16.1 mm TL (mean, 15.83 mm) at the juvenile stage on days 30-32 after hatching, and the number of rays in all fins was completely revealed.

Pilot California Spiny Lobster Postlarvae Sampling Program: Collector Selection

Lobster (infraorder Astacidea) is perhaps the most intensively studied shellfish around the world due to its economic importance (Phillips 2006). Fishery management tools almost universally include catch reporting, but fishery-dependent data such as this often fails to adequately inform managers about the true state of the population (Erisman et al. 2011). Increasingly, fishery-independent surveys are being relied upon to provide the robust information fishery managers require, such as the California Cooperative Oceanic Fisheries Investigation (CalCOFI). The CalCOFI program attempts to understand and predict variations in the Pacific Sardine (Sardinops sagax) fishery, among others, in California through quarterly sampling of fish larvae and other biological and hydrographic data. This focus on larval stages stems from Hjort’s seminal work in 1914, which hypothesized the recruitment and transition of larval forms into postlarval and juvenile life stages is a critical period in population dynamics (Houde 2008). In modern times, fishery management agencies expend significant effort towards cataloging and understanding recruitment levels and patterns which provide the foundation for most fishery management tools (e.g. stock assessments). Recruitment monitoring is at the core of many of global lobster fishery management programs (Cruz et al. 1995; Acosta et al. 1997; Cruz and Adriano 2001; Phillips et al. 2005; Phillips and Melville-Smith 2005; Phillips et al. 2006; Arteaga-Rios et al. 2007; Phillips et al. 2010). Recruitment monitoring of numerous lobster taxa globally have been well correlated with future catch-rate predictions, typically with a 4 to 5 year time lag (e.g. Gardner et al. 2002; Caputi and Brown 2011; Linnane et al. 2014). Long-term recruitment monitoring programs, such as that in Australia (Linnane et al. 2010), are vital in assessing future stock levels and setting the total allowable commercial catches. Like many lobster species, the California Spiny Lobster (Panulirus interruptus) is an economically important fishery species, supporting one of California’s most valuable fisheries with annual ex-vessel values exceeding $9 million (Porzio et al. 2012). However, unlike many of the world’s lobster fisheries, no California Spiny Lobster recruitment monitoring program exists. Recent attempts to address this data gap have been made using plankton collection (Koslow et al. 2012) and power plant entrapment records (Miller 2014). Plankton collections were unable to reliably predict recent landings while entrapment records were more successful, but both articles noted the likely effect of unknown recreational harvest levels impacting the analyses and final conclusions. While informative, neither existing program fulfills the need for targeted information on California Spiny Lobster recruitment in southern California. Furthermore, as southern California power plants shift away from once-throughcooling, lobster entrapment data may soon be unavailable, in which case no regular abundance estimates of California Spiny Lobster postlarvae will be available. Noting the clear need for lobster recruitment monitoring in California, a pilot program was initiated in Orange County, California with the hopes of establishing a model that Bull. Southern California Acad. Sci. 113(3), 2014, pp. 180–186 E Southern California Academy of Sciences, 2014

Modelling the spread and connectivity of waterborne marine pathogens: the case of PaV1 in the Caribbean

AbstractThe PaV1 virus infects spiny lobsters (Panulirus argus) throughout most of the Caribbean, where its prevalence in adult lobsters can reach 17% and where it poses a significant risk of mortality for juveniles. Recent studies indicate that vertical transmission of the virus is unlikely and PaV1 has not been identified in the phyllosoma larval stages. Yet, the pathogen appears subclinically in post-larvae collected near the coast, suggesting that lobster post-larvae may harbour the virus and perhaps have aided in the dispersal of the pathogen. Laboratory and field experiments also confirm the waterborne transmission of the virus to post-larval and early benthic juvenile stages, but its viability in the water column may be limited to a few days. Here, we coupled Lagrangian modelling with a flexible matrix model of waterborne and post-larval-based pathogen dispersal in the Caribbean to investigate how a large area with complex hydrology influences the theoretical spread of disease. Our results indicate that if the virus is waterborne and only viable for a few days, then it is unlikely to impact both the Eastern and Northwestern Caribbean, which are separated by dispersal barriers. However, if PaV1 can be transported between locations by infected post-larvae, then the entire Caribbean becomes linked by pathogen dispersal with higher viral prevalence in the North. We identify possible regions from which pathogens are most likely to spread, and highlight Caribbean locations that function as dispersal “gateways” that could facilitate the rapid spread of pathogens into otherwise isolated areas.

Selected nutrient profiles in first larvae and postlarvae of American lobster (Homarus americanus)

Initiatives to enhance natural stock of lobster imply the production of high-quality postlarvae. The aim of this study was to evaluate the physiological condition of postlarvae produced under hatchery conditions by comparing the nutrient profiles of larvae stage I and postlarvae stage IV of American lobster (Homarus americanus) fed frozen adult Artemia with a mixture of dry commercial products. Body sterols, acetone mobile polar lipids and phospholipids levels were lower in stage IV than in stage I, while cholesterol was nearly 400 % higher in the former. The C20 mono-unsaturated acids and C22 n-3 decreased between stage I and IV in both neutral and polar lipids, while linoleic (18:2n-6 cis) and linolenic (18:3n-3) acids increased concomitantly. The levels of docosahexaenoic acid (DHA) in the polar fraction were twice lower in postlarvae compared to stage I larvae and almost completely depleted in the neutral fraction while eicosapentaenoic acid levels were reduced by nearly 30 % in the polar lipids and by over 70 % in the neutral lipids. Results suggested possible dietary phospholipids and DHA deficiencies that lead to the low levels observed in the postlarvae stage IV.

PERKEMBANGAN POST-LARVA IKAN NILEM Osteochilus hasselti C.V. DENGAN POLA PEMBERIAN PAKAN BERBEDA

Failure of adaptation in feed utilization can result in larval mortality. Post-larval stage is a critical period of fish development in which transition from internal feeding to external feeding occurs. This study aimed to determine the growth and survival of hard-lipped barb ( Osteochilus hasselti C.V.) post-larvae fed with different feeding patterns. The experiment was conducted on an experimental basis with a completely randomized design (CRD). The treatments consisted of (P1) 100% Spirulina sp., (P2) 75% Spirulina sp. + 25% pellet powder, (P3) 50% Spirulina sp. + 50% powder pellet, (P4) 25% +75% sp Spirulina pellet powder, and (P5) 100% powder pellets. Day 1 post-hatching larvae were reared in aquaria with density of 17 fish / L for 8 weeks. The larvae were fed as much as 5% of the total weight of biomass. Post-larval development was evaluated by observing the development of the larvae morphology, the body length (every week), the biomass weight (every 2 weeks), and calculating their survival rate at week 8. Morphological data were analyzed descriptively. Data on body length, biomass weight and survival were analyzed using two-way ANOVA followed by LSD test. The results showed that the feeding pattern significantly affected the development of post-larvae (p<0.05). The most advance post-larval development was obtained from the post-larvae fed with 100% pellet powder. In this group, morphological characters of post-larvae in the first week were the mouth start opening, the skin was pigmented, and gall bladder in bi-lobes shaped, caudal fin and dorsal fins were differentiated. Completion of fins development was achieved by the third week when the post-larvae have adult morphological character. The highest body length and biomass weight of the post-larvae was obtained in the group fed with100% of pellets and the highest survival rate was found in the group fed with combination of 50% Spirulina sp. + 50% pellet powder (P3).

Sensitivity of Danio rerio (Teleostei, Cyprinidae) during two stages of development based on acute toxicity tests.

The sensitivity of Danio rerio to three chemicals was compared at two growth stages [larval (10 ± 2 after hatching) and post-larval (60 ± 4 days after hatching)] based on acute toxicity tests. Thirty-nine 48 h acute toxicity tests were performed with the substances CuSO4, NaCl and KCl. The 48 h LC50 values at the two growth stages were compared by independent samples t-tests. The results showed a clear decrease in sensitivity when post-larval organisms were used. Since acute toxicity test methods for D. rerio that recommend using post-larval stage fish do not represent the most sensitive stage of the test organism, our study suggests a revision of the methods to use larval fish.

Size-dependent predation of fish larvae by jellyfish: an experimental evaluation exemplified with the flounder Paralichthys olivaceus larvae and the moon jellyfish Aurelia aurita medusae

This study evaluates the size-dependent predation of fish larvae by jellyfish, exemplified with flounder Paralichthys olivaceus and moon jellyfish Aurelia aurita under laboratory conditions. The effects of some environmental factors on the size-dependent predation were also investigated. The results indicate that the predation rate increased with larval development, until the larvae had developed the ability to actively avoid predation at approximately 11-day post-hatching and decreased thereafter. This suggests a size-dependent predation on the fish larvae. Water temperature and predator size significantly affected the predation rate of the medusae on the fish larvae, but the temperature and size effects were markedly reduced as the larvae reached post-larval stage. These findings suggest that water temperature and jellyfish size interacted with the ontogenetic development of the fish larvae to affect the predation rates. The presence of alternative prey Artemia salina, could alleviate the predation rate on the fish larvae, whereas light conditions showed no effects on the predation rate. Due to their overlaps in spatial and temporal distributions along the north Chinese coast, jellyfish are likely to prey upon flounder larvae and thus affect the recruitment of the wild fish populations.

The genome and occlusion bodies of marine Penaeus monodon nudivirus (PmNV, also known as MBV and PemoNPV) suggest that it should be assigned to a new nudivirus genus that is distinct from the terrestrial nudiviruses.

BackgroundPenaeus monodon nudivirus (PmNV) is the causative agent of spherical baculovirosis in shrimp (Penaeus monodon). This disease causes significant mortalities at the larval stage and early postlarval (PL) stage and may suppress growth and reduce survival and production in aquaculture. The nomenclature and classification status of PmNV has been changed several times due to morphological observation and phylogenetic analysis of its partial genome sequence. In this study, we therefore completed the genome sequence and constructed phylogenetic trees to clarify PmNV’s taxonomic position. To better understand the characteristics of the occlusion bodies formed by this marine occluded virus, we also compared the chemical properties of the polyhedrin produced by PmNV and the baculovirus AcMNPV (Autographa californica nucleopolyhedrovirus).ResultsWe used next generation sequencing and traditional PCR methods to obtain the complete PmNV genome sequence of 119,638 bp encoding 115 putative ORFs. Phylogenetic tree analysis showed that several PmNV genes and sequences clustered with the non-occluded nudiviruses and not with the baculoviruses. We also investigated the characteristics of PmNV polyhedrin, which is a functionally important protein and the major component of the viral OBs (occlusion bodies). We found that both recombinant PmNV polyhedrin and wild-type PmNV OBs were sensitive to acid conditions, but unlike the baculoviral OBs, they were not susceptible to alkali treatment.ConclusionsFrom the viral genome features and phylogenetic analysis we conclude that PmNV is not a baculovirus, and that it should be assigned to the proposed Nudiviridae family with the other nudiviruses, but into a distinct new genus (Gammanudivirus).Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-628) contains supplementary material, which is available to authorized users.

Colonization patterns of decapods into artificial collectors: seasonality between habitat patches

Understanding colonization of new habitats by recruits is essential to comprehend local abundance patterns of adult populations. Colonization of benthic habitats by new colonizers is achieved through the influx of larvae from the water column and movements from adjacent habitats. Colonization, i.e., the composition and abundance of new colonizers, into a focal habitat may be affected by surrounding habitats. In this study, we investigated seasonal variation through an annual cycle in postlarval settlement patterns of decapod crustaceans colonizing artificial collectors on different habitats, in particular: Cymodocea nodosa seagrass meadows, sandy patches, ‘urchin-grazed’ barrens and macroalgal-dominated beds, which are arranged in patches within seascapes in the eastern Atlantic. Our results showed that: 1) decapods, at least some species, settle preferentially on artificial collectors deployed on vegetated substrates when compared to those deployed on unvegetated substrates; 2) despite most decapods have a planktonic larval phase with wide oceanic dispersal, the presence of crustaceans in particular habitats suggests a great specificity at their early post-larval stages; and 3) although subtropical waters of Gran Canaria have a weak seasonal variation, early postlarval stages of decapod crustaceans showed two distinct settlement periods, i.e., a ‘cold’ and a ‘warm’ season.

Survival and growth of juveniles of the coconut crab Birgus latro under laboratory conditions: implications for mass production of juveniles

Populations of the coconut crab, Birgus latro (Linnaeus, 1767), have been depleted by primarily overharvest. The aim of this study was to develop artificial propagation technologies for the restocking and conservation of this species: it is a terrestrial hermit crab with aquatic larvae. Megalopae (post-larvae stage) were group cultured for six months with access to both “land” and “sea” areas (trial 1). In addition, shell-carrying juveniles aged one month were group cultured on land until the age of 13 or 24 months (trial 2). Furthermore, juveniles that had abandoned their gastropod shells were cultured individually and their moult and growth was monitored. The survival rates of animals ranged from 26-55% in trial 1, and they grew to a mean thoracic length (TL) of approx. 1 mm. In trial 2, the juveniles grew to a mean TL of approx. 4 mm at age 24 months. The juveniles changed their gastropod shells for larger ones according to their growth based on their body width. The juveniles found soon after abandoning their gastropod shells varied in size (2.5-8.6 mm TL), age (15-26 months old), and the degree of the formation of pleonal tergal plates. The juveniles without shells moulted 5-6 times during the culture period of 9-20 months. Two survivors grew to 6.8 mm TL and 11.9 mm TL at an age of 24 and 37 months, respectively. The body colour pattern of the juveniles was retained through successive moults. Our results demonstrated the feasibility of artificial production of the coconut crab juveniles and the utility of using natural marks to monitor their growth and migration after being released in the wild.

Distribution of Pasiphaea japonica larvae in submarine canyons and adjacent continental slope areas in Toyama Bay, Sea of Japan

The horizontal and vertical distribution of Pasiphaea japonica larvae, which included larval stages and postlarval or later stages, were investigated in Toyama Bay located in central Japan. The horizontal distributions in the inner part of the bay were investigated by oblique hauls from 10m above the sea-bottom to the surface using a Remodeled NORPAC net (LNP net) in May, August, November 2005, January, March, April, July, September, December 2006, March–September, November–December 2007, and January–March 2008. The vertical distributions were investigated by concurrent horizontal hauls at the depths of 0, 50, 100, 150, 200, and 250m using a Motoda net (MTD net) in January, March, April, July, September, and December 2006. Mean density of larvae was higher in submarine canyons which dissect the continental shelf and run to the mouth of river, than adjacent continental slope areas. Larvae densely aggregated in the canyon head. Vertical distribution of the larval stages concentrated in the depth range of 100–150m in both daytime and nighttime, and larvae in the postlarval or later stages showed diel vertical distribution over a wider depth range than larval stages. Our results indicate the possibility of a larval aggregation in energy-rich habitats, and indicated two important roles of submarine canyons, which were larval retention and high food supply.

Pan-tropical distribution of the Jurassic ostreid bivalves

Globally, the Jurassic cemented ostreid bivalves from northern Tibet, SW China, have a pan-tropical distribution pattern between palaeolatitudes of 60° South and North. Ostreid bivalves have tiny to large larvae, and nearly all of them have a cemented mode of life during their adult stage. The distribution pattern and the habits of the Jurassic ostreid bivalves revealed that, in the Jurassic time interval, all seas and oceans were interconnected, and ostreid bivalves were very capable of dispersion through their planktonic larval stage or as pseudoplankton during the post-larval stage, and even were able to cross the palaeo-Pacific Ocean from east to west. However, latitudinal temperature variation limited the distribution of these thermophilous bivalves to the lower and middle latitudes.

Developmental rate, size, and sexual dimorphism of Megaselia scalaris (Loew) (Diptera: Phoridae): its possible implications in forensic entomology.

Cosmopolitan scuttle fly, Megaselia scalaris (Loew) (Diptera: Phoridae) is one of the commonest forensic species recorded colonizing human corpse indoors and in concealed environment. The occurrence of this species in such environments provides a higher evidential value to assist estimation of postmortem interval (PMI) compared to other forensically important dipterans. However, developmental and size data of M. scalaris are still lacking and they are derived from a limited range of thermal values. The objective of this study is to develop the growth model of M. scalaris by emphasizing the size range of larvae and puparia at different constant temperatures. This species was reared in six replicates at eight varying constant temperatures ranging from 23 to 36°C and cow's liver was provided as food source. Larvae and puparia were sampled at set time intervals and measured by their length and weight. Because interpretation of forensic entomological evidence is subject to application of different techniques, development of M. scalaris is expressed herein by using developmental table, length/morphological stage diagrams and linear/nonlinear estimation methods. From the findings, it is very important to highlight that sexual dimorphism of M. scalaris during post feeding larva and pupa stage could be observed based on size and developmental periods. Mean length and weight ratios of male to female puparia are approximately 0.8 and 0.3-0.5, respectively, indicating sexual dimorphism of this species. Developmental period in female are 4.0-11.4h (post feeding larval stage), 3.7-24.0h (pupal stage), and 3.0-20.1h (total developmental period) longer in male. Due to this dimorphism, PMI estimation using M. scalaris post feeding larva or puparium specimens must be carried out carefully by to avoid inaccuracy and misinterpretation.

Cloning and expression analysis on a homolog of spermatogonial stem-cell renewal factor in Fenneropenaeus chinensis

The spermatogonial stem-cell renewal factor (SSRF) was named since its function in spermatogonial mitosis was reported in Japanese eel. Our previous study showed that a homolog of SSRF was highly expressed in the ovary of triploid shrimp, but not expressed in the ovary of diploid shrimp. To understand the function of SSRF in shrimp, the full-length cDNA of ssrf gene was cloned from Chinese shrimp Fenneropenaeus chinensis (Fcssrf) and its expression was analyzed. The full length of Fcssrf cDNA was 2588 bp and it contained an open reading frame encoding 450 amino acids. The predicted tertiary structure of FcSSRF was very similar to that of SSRF/eSRS34 from Anguilla japonica and TP/PD-ECGF from Homo sapiens. RT-PCR analysis showed that the Fcssrf was highly expressed in nerve, testis, hepatopancreas, gill, and stomach rather than in ovary. Expression of Fcssrf mRNA was not detected during embryonic stages and larval stages, from the nauplii to the post-larvae stage, in diploid, and triploid shrimp. However, it began to be expressed in juvenile stages (June–September) in diploid and triploid shrimp. Immunohistochemical analyses showed that FcSSRF was identified in both the diploid testis and triploid ovary. We inferred that the Fcssrf might be related to testis development.