Performance of the SSI development function compared with 33 other functions applied to 79 arthropod species' datasets.

The development rates of arthropods are temperature-dependent. Studies aiming to predict the dynamics of arachnid, crustacean, and insect populations in nature often require the derivation of development functions representing this phenomenon. A previous study (Quinn, B.K., 2017, J. Therm. Biol. 63, 65-77) identified 33 development functions commonly used in past studies on temperature-dependent development of arthropods, and illustrated that: (1) most of 99 past studies only applied one or few (2-5) development functions to their data without considering others; and (2) most of a subset of 79 studies' data were not fit with the actual best function for them, resulting in sometimes substantial differences in model performance and predictive ability. However, that study did not test the class of development functions based on theoretical enzyme thermodynamics, including the Sharpe-Schoolfield-Ikemoto (SSI) function. Herein, the meta-analyses done in that previous study were redone, after fitting all 79 reanalyzed datasets with the SSI function. Estimates of the intrinsic optimum temperature (TΦ) for development of each tested species were also derived using the SSI function and compared among taxa. Including the SSI function in analyses did not change the conclusions of the previous study concerning development function usage, choice, and consequences. Notably, the SSI function performed as well as or relatively better than other functions of comparable or lower complexity in terms of R2, AICC-based rankings, ΔAICC values, and prediction errors, which may recommend its more widespread use in future studies. Overall differences in TΦ were found among arthropod subphyla, as well as between most species pairs. Most TΦ estimates produced herein were novel, and could be used to make inferences about or comparisons among arthropod taxa in future studies.

Temporal variation of antibiotic resistance genes carried by culturable bacteria in the shrimp hepatopancreas and shrimp culture pond water.

The increasing prevalence of antibiotic resistance genes (ARGs) is a challenge to the health of humans, animals and the environments. Human activities and aquatic environments can increase ARGs. Few studies have focused on the temporal variation of aquatic bacteria with multiple ARGs in aquatic environments affected by human production activity. We studied culturable bacteria (CB) carrying ARGs, including sul1, sul2, floR, strA and gyrA in the shrimp hepatopancreas (HP) and in pond water during shrimp culture. The relative abundance of ARGs carried by CB in HP was higher than that in water (P < 0.05). However, CB carrying ARGs generally varied in random pattern. The correlation of sul2 abundance was significantly positive in HP, while that of strA abundance was significantly negative in water (P < 0.05) during shrimp culture. Among all of the CB, 33.59% carried multiple ARGs. Temporal distance-decay analysis indicated that CB carrying ARGs in water were more resistant to the effects of human activity. CB carrying ARGs varied temporally in HP and pond water during shrimp culture. These results demonstrate that multiple ARGs are carried by CB, and these varied with the phase of aquatic culture.

A review on the application of Bacillus as probiotics in aquaculture.

Probiotics use in aquaculture has gained attention as microbial candidates to maintain the health and the well-being of many aquaculture animals. Among the many microbial candidates, probiotic Bacillus has sporulation capacity that makes them survive harsh environmental conditions, are non-pathogenic and non-toxic when fed to fish, and can produce antimicrobial substances making them more suitable candidates compared to other probiotics. In this review, we discussed the necessity of using the probiotic Bacillus in sustainable aquaculture as a good alternative to improve feed utilization, stress response, immune response and disease resistance, maintenance of tissue integrity, and as well improvement of water quality for sustainable aquaculture. Therefore the findings of current researches about the effects of Bacillus application to improve the culture of aquatic animals for future research and development of Bacillus application in aquaculture have been summarised.

Molecular cloning and characterization of genes encoding chitinase and N-acetyl-ß-glucosaminidase in Dolerocypris sinensis.

Chitinases and N-acetyl-ß-glucosaminidase (NAG) are important in molting and growth of crustaceans. In ostracods, the genes encoding these enzymes have not been characterized. The aim of the present study was to clone the genes encoding chitinase (DsChi) and NAG (DsNAG) from the ostracod, Dolerocypris sinensis, elucidate the phylogenetic relationships between the cloned genes and known chitinolytic enzymes, and determine the expression patterns of these genes at different stages of growth in the presence of an environmental pollutant. The genes were amplified from the genomic DNA of the organism using polymerase chain reaction (PCR). The products from PCR were cloned and characterized with bioinformatics tools, and their expression patterns at different growth stages were determined using real-time quantitative PCR (qRT-PCR). Nine and five introns were identified in DsChi and DsNAG genes, respectively. When compared with protein sequences available in GenBank, chitinase from D. sinensis was most closely related to that of Macrobrachium nipponense (61 % homology). The NAG of D. sinensis was most closely related to that of Limulus polyphemus (55.6 % homology). Based on phylogenetic analysis of known chitinases from crustaceans and insects, the D. sinensis chitinase tightly clustered in the same branch with chitinases from species within the Malacostraca class. In contrast, NAG of D. sinensis was clustered with NAG from F. candida.The level of expression of DsChi mRNA was significantly higher than that of DsNAG throughout the period of growth (p < 0.05). Treatment of D. sinensis cells with fenoxycarb significantly downregulated the expressions of DsChi and DsNAG throughout the period of growth (p < 0.05). These results show that the protein products of DsChi and DsNAG possess remarkable biochemical properties characteristic of a chitinase and NAG, respectively.

Quantitative genetic changes in reproductive performance of giant freshwater prawn after 10 years of selection for increased growth rate.

Effect of long-term selection for improved growth on reproductive performance of giant freshwater prawn (GFP) Macrobrachium rosenbergii has not been reported in the literature. The present study aimed to measure correlated responses in reproductive traits and to estimate genetic parameters for these characters in a GFP population selected for high growth over ten generations from 2007 to 2016. A total of 959 breeding females (offspring of 515 sires and 810 dams) had measurements for seven reproductive traits (weight before spawn WBS; weight after spawn WAS; Fecundity FEC or number of larvae per female at hatching; first age to reach post-larvae PLAGE; zoea (e) weight ZOEAWT; larval survival during hatchery phase SURV1 and survival from PL to tagging SURV2. The restricted maximum likelihood (REML) and mixed model analysis were used to estimate genetic parameters and evaluate selection responses for the seven traits studied. Our REML analysis showed that heritability for these traits ranged from 0.04 to 0.42 (SE: 0.19-0.28). Female body weight either before or after spawning had strong positive phenotypic correlations with fecundity (0.52-0.98). By contrast, the phenotypic correlations of WBS/WAS with larval and fry survivals were not significant (-0.08-0.05). Genetic correlations among fecundity-related traits studied were not different from zero due to their high standard errors. Correlated responses in reproductive traits were measured by comparing least squares means of the selection line and control group. Females of the selected line for high growth had significantly greater weight before or after spawning than that of the control group. There were, however, no statistical differences between the two lines in the other traits. It is concluded that selection for high growth did not have detrimental impact on reproductive performance of breeding females in the present population of GFP.

Response of host-bacterial colonization in shrimp to developmental stage, environment and disease.

The host-associated microbiota is increasingly recognized to facilitate host fitness, but the understanding of the underlying ecological processes that govern the host-bacterial colonization over development and, particularly, under disease remains scarce. Here, we tracked the gut microbiota of shrimp over developmental stages and in response to disease. The stage-specific gut microbiotas contributed parallel changes to the predicted functions, while shrimp disease decoupled this intimate association. After ruling out the age-discriminatory taxa, we identified key features indicative of shrimp health status. Structural equation modelling revealed that variations in rearing water led to significant changes in bacterioplankton communities, which subsequently affected the shrimp gut microbiota. However, shrimp gut microbiotas are not directly mirrored by the changes in rearing bacterioplankton communities. A neutral model analysis showed that the stochastic processes that govern gut microbiota tended to become more important as healthy shrimp aged, with 37.5% stochasticity in larvae linearly increasing to 60.4% in adults. However, this defined trend was skewed when disease occurred. This departure was attributed to the uncontrolled growth of two candidate pathogens (over-represented taxa). The co-occurrence patterns provided novel clues on how the gut commensals interact with candidate pathogens in sustaining shrimp health. Collectively, these findings offer updated insight into the ecological processes that govern the host-bacterial colonization in shrimp and provide a pathological understanding of polymicrobial infections.

Carry-over effects modulated by salinity during the early ontogeny of the euryhaline crab Hemigrapsus crenulatus from the Southeastern Pacific coast: Development time and carbon and energy content of offspring.

Hemigrapsus crenulatus is a key species of coastal and estuarine ecosystems in the Southeastern Pacific and New Zealand. Since the gravid females-and their embryos-develop under conditions of variable salinity, we propose that low external salinity will be met with an increase in energy expenditures in order to maintain osmoregulation; subsequently, the use of energy reserves for reproduction will be affected. In this study, we investigate in H. crenulatus whether 1) the biomass and energy content of embryos is influenced by salinity experienced during oogenesis and embryogenesis and 2) how variation in the biomass and energy content of embryos affects larval energetic condition at hatching. Here at low salinity (5PSU), egg-bearing females experienced massive and frequent egg losses, and therefore the development of their eggs during embryogenesis was not completed. In turn, at intermediate and high salinity (15 and 30PSU) embryogenesis was completed, egg development was successful, and larvae were obtained. Consistently, larvae hatched from eggs produced and incubated at high salinity (30PSU) were larger, had higher dry weight, and had increased carbon content and energy than larvae hatched from eggs produced at intermediate salinity (15PSU). From these results, it is seen that the size and biomass of early life stages of H. crenulatus can be affected by environmental salinity experienced during oogenesis and embryogenesis, and this variation can then directly affect the energetic condition of offspring at birth. Therefore, this study reveals a "cascade effect" modulated by salinity during the early ontogeny.

Unexpected UBX expression in the maxilliped of the mystacocarid crustacean Derocheilocharis remanei-evidence for a different way of making a maxilliped?

In terms of morphology, crustacean maxillipeds are hybrid appendages. They arise in anterior thoracic segments and display characteristics of both locomotory (thoracic) and feeding (gnathal) appendages. Maxillipeds are functionally integrated with the anterior gnathal appendages. Hox gene expression patterns and immunolabeling with the FP6.87 antibody, which detects conserved epitopes of UBX and ABD-A proteins, reveal that maxillipeds are consistently associated with a shift in the expression of the homeotic gene Ubx. Ubx transcription products or proteins only appear in thoracic segments with a typical locomotory thoracopod and are consistently absent in the maxilliped. This pattern is found in various crustaceans: the copepod Mesocyclops, the mysid Mysidium, the decapods Homarus and Periclimenes, the isopod Porcellio, and the amphipod Parhyale. In Parhyale, which possesses maxillipeds on the first thoracic segment, gene manipulation experiments have shown that a leg-like thoracic appendage can be recovered by mis-expressing Ubx in that segment and walking legs can be transformed into maxillipeds by Ubx-knockdown. This survey focuses on the expression of UBX/ABD-A proteins, studied using the FP6.87 antibody, in the larval stages of the mystacocarid crustacean Derocheilocaris remanei. Mystacocarids inhabit the intertidal meiofauna zone of sandy beaches and possess one pair of maxillipeds on the first thoracic segment. Strong UBX/ABD-A expression in the developing maxilliped makes Derocheilocaris unique among crustaceans. Our data might also show that the transformation from locomotory thoracopod to maxilliped cannot be accounted for by the mere presence or absence of UBX, because in mystacocarids, UBX is present in both kinds of limbs. The role of the other Hox gene known to be involved in this transformation, Sex combs reduced (Scr), is unclear. The results presented here may document a new example of a shift in Hox gene function in arthropods. The difference in UBX/ABD-A expression between D. remanei and the copepod maxillipeds is of particular interest because correspondences between the feeding apparatus-including the maxilliped-in mystacocarids and copepods have been suggested as being of phylogenetic significance.

Morphological characterization and biocontrol effects of Vibrio vulnificus phages against Vibriosis in the shrimp aquaculture environment.

The re-emerging field of phage therapy is the potential biocontrol agents for the transfer of virulence factor and to kill their bacterial hosts. In this study, the lytic Vibrio vulnificus phages were studied to provide a better understanding of phage-host interactions and development of phage therapy. Four new V. vulnificus phages were detected from shrimp aquaculture system, named VV1, VV2, VV3 and VV4. All lytic V. vulnificus phages are the Tectiviruses of the family Tectiviridae with typical double layered elongated icosahedral head and tailless morphology. Lytic V. vulnificus phages which infect other Vibrio isolates were further characterized by long term storage, enzymes treatment, organic solvents treatment, detergents treatment, pH stability, temperature stability, agar bioassay method and one-step growth experiment. The effects of chloroform, acetone, ethyl alcohol, methyl alcohol, ribonuclease (RNase), trypsin, protease, Triton-X100 treatments were not affected the growth of VV1, VV2, VV3 and VV4 phages. These phages (VV1-VV4) were inactivated completely with temperature (over 60 °C), pH (<3 or >12), lysozyme and sodium dodecyl sulfate (SDS) treatment. One-step growth experiments indicated that the latent period was at 3 h and burst size was at 37 °C. Agar bioassay method indicated that the percentage of inhibition was 75% (VV1) and 70% (VV2, VV3 & VV4), respectively. SDS-PAGE analysis of all V. vulnificus phages had similar protein patterns with molecular weight masses of 260, 249, 204, 148, 63, 59, 22 and 15 kDa. Hence, it could be concluded that V. vulnificus phage had a broad lytic spectrum and potential biocontrol of luminous Vibriosis in the shrimp aquaculture system.

Life stage and species identity affect whether habitat subsidies enhance or simply redistribute consumer biomass.

Quantifying the response of mobile consumers to changes in habitat availability is essential for determining the degree to which population-level productivity is habitat limited rather than regulated by other, potentially density-independent factors. Over landscape scales, this can be explored by monitoring changes in density and foraging as habitat availability varies. As habitat availability increases, densities may: (1) decrease (unit-area production decreases; weak habitat limitation); (2) remain stable (unit-area production remains stable; habitat limitation) or (3) increase (unit-area production increases; strong habitat limitation). We tested the response of mobile estuarine consumers over 5 months to changes in habitat availability in situ by comparing densities and feeding rates on artificial reefs that were or were not adjacent to neighbouring artificial reefs or nearby natural reefs. Using either constructed or natural reefs to manipulate habitat availability, we documented threefold density decreases among juvenile stone crabs as habitat increased (i.e. weak habitat imitation). However, for adult stone crabs, density remained stable across treatments, demonstrating that habitat limitation presents a bottleneck in this species' later life history. Oyster toadfish densities also did not change with increasing habitat availability (i.e. habitat limitation), but densities of other cryptic fishes decreased as habitat availability increased (i.e. weak limitation). Feeding and abundance data suggested that some mobile fishes experience habitat limitation, or, potentially in one case, strong limitation across our habitat manipulations. These findings of significant, community-level habitat limitation provide insight into how global declines in structurally complex estuarine habitats may have reduced the fishery production of coastal ecosystems.

The Underlying Ecological Processes of Gut Microbiota Among Cohabitating Retarded, Overgrown and Normal Shrimp.

Increasing evidence of tight links among the gut microbiota, obesity, and host health has emerged, but knowledge of the ecological processes that shape the variation in microbial assemblages across growth rates remains elusive. Moreover, inadequately control for differences in factors that profoundly affect the gut microbial community, hampers evaluation of the gut microbiota roles in regulating growth rates. To address this gap, we evaluated the composition and ecological processes of the gut bacterial community in cohabitating retarded, overgrown, and normal shrimps from identically managed ponds. Gut bacterial community structures were distinct (P = 0.0006) among the shrimp categories. Using a structural equation modeling (SEM), we found that changes in the gut bacterial community were positively related to digestive activities, which subsequently affected shrimp growth rate. This association was further supported by intensified interspecies interaction and enriched lineages with high nutrient intake efficiencies in overgrown shrimps. However, the less phylogenetic clustering of gut microbiota in overgrown and retarded subjects may offer empty niches for pathogens invasion, as evidenced by higher abundances of predicted functional pathways involved in disease infection. Given no differences in biotic and abiotic factors among the cohabitating shrimps, we speculated that the distinct gut community assembly could be attributed to random colonization in larval shrimp (e.g., priority effects) and that an altered microbiota could be a causative factor in overgrowth or retardation in shrimp. To our knowledge, this is the first study to provide an integrated overview of the direct roles of gut microbiota in shaping shrimp growth rate and the underlying ecological mechanisms.

Emergent Macrophytes Support Zooplankton in a Shallow Tropical Lake: A Basis for Wetland Conservation.

Understanding the biodiversity value of littoral zones of lakes is a priority for aquatic biodiversity conservation. However, less emphasis has been given to the littoral part of tropical African lakes, with many of the previous researches focusing only on the open water side. The aim of the present study was, therefore, to investigate the impact of the littoral zone of a shallow freshwater tropical lake (Ziway, Ethiopia), dominated by two emergent macrophytes, on zooplankton community structure. We hypothesized that the wetland vegetation serves as a preferred microhabitat for zooplankton communities. A lake with substantial coverage of emergent macrophytes was monitored monthly from January to August, 2016. The monitoring included the measurements of physical, chemical, and biological parameters. Sampling sites were selected to represent areas of the macrophyte vegetation (Typha latifolia and Phragmites australis) and the open water part of the lake. Sites with macrophyte vegetation were found to be the home of more dense and diverse zooplankton community. However, during the period of high vegetation loss, the density of crustacean zooplankton showed significant reduction within the patches of macrophytes. From biodiversity conservation perspective, it was concluded that the preservation of such small areas of macrophytes covering the littoral zone of lakes could be as important as protecting the whole lake. However, the rapid degradation of wetland vegetation by human activities is a real threat to the lake ecosystem. In the not-too-far future, it could displace and evict riparian vegetation and the biota it supports.

Harnessing fertilizer potential of human urine in a mesocosm system: a novel test case for linking the loop between sanitation and aquaculture.

Human urine (HU) is a biogenic fertilizer which has raised immense interest owing to its capacity of combining sanitation and nutrient recovery. In search of an alternative organic fertilizer for fish culture, the nutrient potential of HU was evaluated. Fries of Indian carps and larvae of freshwater prawn were reared for 120 days under six conditions: (a) aerated and (b) non-aerated fresh HU (0.01%), (c) cattle manure (CM; 1.8 kg tank-1), mixed treatment with CM and HU under (d) iso-phosphorus and (e) iso-nitrogenous condition and (f) control. Monitoring of water quality and biological parameters revealed that total fish yield was the highest in CM (621.5 g tank-1) followed by mixed treatments under iso-nitrogenous (428 g tank-1) and iso-phosphorus (333 g tank-1) conditions, aerated HU (321 g tank-1) and HU (319 g tank-1). The gross primary productivity (GPP) in HU was satisfactory (601.8 mg C m-2 h-1) and superior to all but CM treatment. The abundance of heterotrophic bacteria (HB) was highest in CM and lowest in HU. Both GPP and HB population were correlated positively with fish yield per tank. Although pH in all treatments remained high (pH 8.4-8.9), no ammonia toxicity was observed. No E. coli infestation in any fish muscle was encountered. The concentrations of cadmium and lead in fish muscle were within respective safe level. The study established that high fertilizer potential of HU could be exploited as an alternative organic fertilizer or as a candidate to be blended with cattle manure.

Competing influences on morphological modularity in biomechanical systems: a case study in mantis shrimp.

Related species that share similar biomechanical systems and segmentation patterns may exhibit different patterns of morphological covariation. We examined morphological covariation of the potent prey capture appendage of two mantis shrimp (Stomatopoda) species-a spearer (Squilla empusa) and smasher (Gonodactylaceus falcatus). We assessed three frameworks for modularity, two based on the biomechanics of the appendage and one based on its segmentation as a proxy for shared developmental pathways. We collected morphometric data from S. empusa, and compared morphological covariation patterns across the raptorial appendage with patterns from a new analysis of previously published morphometric data from G. falcatus. The relative importance of the different hypothetical influences differed between the two species, and was dependent on whether specimens were analyzed all together or subdivided based on sex or sub-populations, including one particularly distinct population in the Gulf of Mexico. We also found an intriguing handedness pattern in which right-hand appendages had a variable number of spines, whereas the left had a constant number of spines. Overall, our findings highlight the importance of testing multiple, alternative frameworks for morphological covariation and suggest that mantis shrimp experience contrasting influences on covariation depending on their feeding mechanisms.

Biosynthesis of silver nanoparticles using a probiotic Bacillus licheniformis Dahb1 and their antibiofilm activity and toxicity effects in Ceriodaphnia cornuta.

In the present study, we synthesized and characterized a probiotic Bacillus licheniformis cell free extract (BLCFE) coated silver nanoparticles (BLCFE-AgNPs). These BLCFE-AgNPs were characterized by UV-visible spectrophotometer, XRD, EDX, FTIR, TEM and AFM. A strong surface plasmon resonance centered at 422 nm in UV-visible spectrum indicates the formation of AgNPs. The XRD spectrum of silver nanoparticles exhibited 2θ values corresponding to the silver nanocrystal. TEM and AFM showed the AgNPs were spherical in shape within the range of 18.69-63.42 nm and the presence of silver was confirmed by EDX analysis. Light and Confocal Laser Scanning Microscope (CLSM) images showed a weak adherence and disintegrated biofilm formation of Vibrio parahaemolyticus Dav1 treated with BLCFE-AgNPs compared to control. This result suggests that BLCFE-AgNps may be used for the control of biofilm forming bacterial populations in the biomedical field. In addition, acute toxicity results concluded that BLCFE-AgNPs were less toxic to the fresh water crustacean Ceriodaphnia cornuta (50 µg/ml) when compared to AgNO3 (22 µg/ml). This study also reports a short term analysis (24 h) of uptake and depuration of BLCFE-AgNPs in C. cornuta.

Living shorelines can enhance the nursery role of threatened estuarine habitats.

Coastal ecosystems provide numerous services, such as nutrient cycling, climate change amelioration, and habitat provision for commercially valuable organisms. Ecosystem functions and processes are modified by human activities locally and globally, with degradation of coastal ecosystems by development and climate change occurring at unprecedented rates. The demand for coastal defense strategies against storms and sea-level rise has increased with human population growth and development along coastlines world-wide, even while that population growth has reduced natural buffering of shorelines. Shoreline hardening, a common coastal defense strategy that includes the use of seawalls and bulkheads (vertical walls constructed of concrete, wood, vinyl, or steel), is resulting in a "coastal squeeze" on estuarine habitats. In contrast to hardening, living shorelines, which range from vegetation plantings to a combination of hard structures and plantings, can be deployed to restore or enhance multiple ecosystem services normally delivered by naturally vegetated shores. Although hundreds of living shoreline projects have been implemented in the United States alone, few studies have evaluated their effectiveness in sustaining or enhancing ecosystem services relative to naturally vegetated shorelines and hardened shorelines. We quantified the effectiveness of (1) sills with landward marsh (a type of living shoreline that combines marsh plantings with an offshore low-profile breakwater), (2) natural salt marsh shorelines (control marshes), and (3) unvegetated bulkheaded shores in providing habitat for fish and crustaceans (nekton). Sills supported higher abundances and species diversity of fishes than unvegetated habitat adjacent to bulkheads, and even control marshes. Sills also supported higher cover of filter-feeding bivalves (a food resource and refuge habitat for nekton) than bulkheads or control marshes. These ecosystem-service enhancements were detected on shores with sills three or more years after construction, but not before. Sills provide added structure and may provide better refuges from predation and greater opportunity to use available food resources for nekton than unvegetated bulkheaded shores or control marshes. Our study shows that unlike shoreline hardening, living shorelines can enhance some ecosystem services provided by marshes, such as provision of nursery habitat.

Transcriptional response of mysid crustacean, Americamysis bahia, is affected by subchronic exposure to nonylphenol.

Nonylphenol (NP) has been classified as an endocrine-disrupting chemical. In this study, we conducted mysid DNA microarray analysis with which has 2240 oligo DNA probes to observe differential gene expressions in mysid crustacean (Americamysis bahia) exposed to 1, 3, 10 and 30 µg/l of NP for 14 days. As a result, we found 31, 27, 39 and 68 genes were differentially expressed in the respective concentrations. Among these genes, the expressions of five particular genes were regulated in a similar manner at all concentrations of the NP exposure. So, we focused on one gene encoding cuticle protein, and another encoding cuticular protein analogous to peritrophins 1-H precursor. These genes were down-regulated by NP exposure in a dose-dependent manner, and it suggested that they were related in a reduction of the number of molting in mysids. Thus, they might become useful molecular biomarker candidates to evaluate molting inhibition in mysids.

Sex ratio, gonad development and fecundity of Miyakella nepa (Crustacea, Stomatopoda) of Pantai Remis coastal waters of Malaysia.

The sex ratio, gonad development and fecundity of Miyakella nepa (Latreille, 1828), in the coastal waters of Pantai Remis, Perak, were investigated from February 2012 to January 2013. Sex identification was done by identifying stomatopod's genitalia organs, and the ovaries were dissected out and preserved for further analysis. Female stomatopods with mature or near spawning stages were used for fecundity estimation. A total of 951 specimens of M. nepa, with 565 females and 386 males were examined. Results showed a sex ratio of 1:1.46 (male:females). Maximum GSI was estimated to be 5.80, while lowest was 2.95. Sexual maturity for female M. nepa was observed at 100 mm total length. The mean fecundity of M. nepa was 425,657 (? 1,8701) eggs which was observed to increase with increased body length.

The effect of γ-radiation on resting eggs and life cycle of cladoceran Moina macrocopa.

We investigated the effects of γ-irradiation on the survival of resting eggs of the cladoceran Moina macrocopa and on the parameters of the life cycle of neonates hatched from the irradiated eggs. It was shown that γ-irradiation in a wide range of doses (from the background level to 100 Gy) had no effect on survival of eggs and mortality of neonates hatched from the irradiated eggs. However, exceeding the absorbed dose of 40 Gy sharply decreased the reproductive potential of the neonates hatched from irradiated eggs.

Seeing double: visual physiology of double-retina eye ontogeny in stomatopod crustaceans.

Stomatopod eye development is unusual among crustaceans. Just prior to metamorphosis, an adult retina and associated neuro-processing structures emerge adjacent to the existing material in the larval compound eye. Depending on the species, the duration of this double-retina eye can range from a few hours to several days. Although this developmental process occurs in all stomatopod species observed to date, the retinal physiology and extent to which each retina contributes to the animal's visual sensitivity during this transition phase is unknown. We investigated the visual physiology of stomatopod double retinas using microspectrophotometry and electroretinogram recordings from different developmental stages of the Western Atlantic species Squilla empusa. Though microspectrophotometry data were inconclusive, we found robust ERG responses in both larval and adult retinas at all sampled time points indicating that the adult retina responds to light from the very onset of its emergence. We also found evidence of an increase in the response dynamics with ontogeny as well as an increase in sensitivity of retinal tissue during the double-retina phase relative to single retinas. These data provide an initial investigation into the ontogeny of vision during stomatopod double-retina eye development.