Naupliar Stages Research Articles

Differential gene expression profile of male and female copepods in response to cadmium exposure

In this study, the whole transcriptome and sex-specific differential gene expression of the copepod Pseudodiaptomus annandalei exposed to cadmium (Cd) were investigated. P. annandalei were exposed to 40 μg/L Cd from the naupliar stage to male and female adults. High-throughput transcriptome sequencing (RNA-seq) was performed with copepod samples using an Illumina Hiseq™ 2000 platform. TransDecoder analysis found 32,625 putative open reading frame contigs. At p-values of <0.001, a total of 4756 differentially expressed genes (DEGs) (2216 up-regulated and 2540 down-regulated genes) were found in male copepods. Whereas a total of 2879 DEGs (2007 up-regulated and 872 down-regulated genes) were found in female copepods. A few selected cellular stress response genes, involved in xenobiotic metabolism, energy metabolism, growth, and development as a result of Cd exposure in the copepods were discussed. The study showed that most of these processes were changed in a sex-specific manner, accounting for the different sensitivities of male and female copepods. Results suggest and reinforce that sex is an important factor to be considered in ecotoxicogenomics.

Genome-wide identification and expression profile of the sox gene family in different tissues and during embryogenesis in the Pacific white shrimp (Litopenaeus vannamei).

Sox transcription factors play essential roles in a variety of critical physiological processes. Still, members of the sox gene family have not yet been genome-wide identified in shrimps. In this study, a total of five members of the sox gene family were identified from the genome of Pacific white shrimp Litopenaeus vannamei and classified into three subgroups based on the conserved HMG-box domain. Among them, three belong to the SoxB subgroup (one in B1 and two in B2), one in the SoxC subgroup, and one in the SoxE subgroup. The five sox genes had different sex-biased expression in some tissues. Sox21, soxB1, and sox14 had a higher expression in ovary than in testis. In comparison, sox4 had a male-biased specific expression in the gonad, hepatopancreas, gill, and eyestalk. There was no difference in soxE gene expression between testis and ovary. During embryonic development, the expression level of three sox genes (soxB1, sox21, and soxE) was higher in gastrulation stage compared to previous stages, declined in limb bud stage and then increased in intramembrane nauplius stage; the expression of sox4 was detected in blastula stage and continued to increase in the following two stages and then surged in intramembrane nauplius stage; the highest expression of sox14 was in the fertilized egg stage, and the expression level decreased with the development of the embryo. These results suggest that the shrimp sox gene family may be involved in gametogenesis, tridermogenesis, and neurogenesis.

Small copepods of the deep South Adriatic Pit: diversity, seasonal and multi-annual dynamics, and implications from the regional hydrography.

In order to expand the fragmentary knowledge on the interactions between the environment and copepod distribution in the deep offshore Adriatic Sea, microcopepod assemblages were investigated during 31 cruises in the 1200-m deep central part of the South Adriatic Pit (SAP), from May 1998 to December 2009. Samples were collected in 8 depth layers, using a 53-μm mesh Nansen net equipped with a closing system. The taxonomic composition and vertical and temporal distributions of copepod abundances were analyzed, considering naupliar stages for all species combined, total calanoid copepodites, copepodite stages and adults separately for oithonids and oncaeids, and all post-naupliar stages combined of harpacticoids and mormonilloids. Corycaeid copepods are not considered in the present study. Data are presented for 41 non-calanoid copepod species, as well as for 7 undetermined morphospecies. Within the family Oncaeidae, four species new to the Adriatic Sea fauna are registered. Nauplii were generally the numerically dominant group, especially in the upper epipelagic layers, where they outnumbered all total post-naupliar stages by a factor of an average 3.5. Oncaeids were notably abundant, accounting in total post-naupliar copepods for an average proportion of 33% in the upper 50m and 74% between 300- and 400-m depth. In the epipelagic zone, copepod abundances were enhanced by the cyclonic circulation which enriches the central part of the SAP with new primary production. A strong advection of Levantine Intermediate Water (LIW) influenced the post-naupliar abundances also in mesopelagic and deeper layers, by promoting the sinking of heavy water mass from the connected middle Adriatic sub-basin which enhances the trophic conditions and transports new organisms into the deeper layers of the SAP. Therefore, the variability in copepod abundances was influenced not only by the seasonal temperature fluctuations but also by the productivity conditions in the SAP which are connected to the movements of regional water masses and the resulting effects on the internal Adriatic circulation.

Molecular characterization of myostatin and its inhibitory function on myogenesis and muscle growth in Chinese Shrimp, Fenneropenaeus chinensis.

Myostatin (Mstn) inhibits muscle growth in vertebrates with endoskeleton, but it is still inconclusive that Mstn is a positive or negative regulator in crustacean with exoskeleton, and little information was available for its function on myogenesis. In this study, we identified and characterized the Mstn from Fenneropenaeus chinensis (FcMstn), and investigated its function on myogenesis and muscle growth. Two different cDNA sequences (2628bp and 2604bp) encoding for slightly different sizes of proteins were obtained for FcMstn, containing 86bp of 5' untranslated regions (UTR) and 1258bp of 3' UTR. The open reading frame of the long sequence and the short sequence contain 1284bp and 1260bp cDNA, encoding 427 and 419 amino acid sequence, respectively. Sequence analysis revealed that the overall protein sequence and specific functional sites of FcMstn were highly conserved with those in other crustacean species. In the early development stage, the muscle firstly appeared in nauplius stage and developed gradually until post larval, but the expression of FcMstn at mRNA and protein levels decreased from nauplius stage to post larval stage, indicating that Mstn involved in myogenesis as a negative regulator in shrimp. In the adult shrimp, the expression of FcMstn at mRNA and protein levels in muscle were significantly lower in the larger group than in the smaller group, and the diameter and number of muscle fiber of the muscle were significantly different between the two groups. Moreover, the shrimp with reduced level of FcMstn by RNAi displayed a dramatic faster growth rate compared with the control group. The present study demonstrates that FcMstn involved in myogenesis and muscle growth probably also as a negative regulator in shrimp like in vertebrates.

Hatching and survival of the salmon 'gill maggot' Salmincola californiensis (Copepoda: Lernaeopodidae) reveals thermal dependence and undocumented naupliar stage.

Salmincola californiensis is a Lernaeopodid copepod parasitizing Pacific salmon and trout of the genus Oncorhynchus. Salmincola californiensis is of increasing concern in both native and introduced ranges because of its potential fish health impacts and high infection prevalence and intensity in some systems. Discrepancies in the documented life history phenology of S. californiensis with the sister species Salmincola edwardsii, as well as our laboratory observations, led us to question the existing literature. We documented a naupliar stage, thought lost for S. californiensis. In addition, we found a high degree of thermal sensitivity in egg development, with eggs developing faster under warmer conditions. Survival of copepodids was also highly dependent on temperature, with warmer conditions reducing lifespan. The longest lived copepodid survived 18 days at 4°C in stark contrast to the generally accepted <48 h survival for that life stage. We also note a consistent relationship between egg sac size and the number of eggs contained. However, egg sac sizes were highly variable. Our findings demonstrate that revisiting old assumptions for S. californiensis and related taxa will be a necessary step to improving our knowledge of the parasite life history and development that will be critical to disease management.

Fine-scale succession patterns and assembly mechanisms of bacterial community of Litopenaeus vannamei larvae across the developmental cycle

BackgroundMicrobiome assembly in early life may have a long-term impact on host health. Larval nursery is a crucial period that determines the success in culture of Litopenaeus vannamei, the most productive shrimp species in world aquaculture industry. However, the succession patterns and assembly mechanisms of larval shrimp bacterial community still lack characterization at a fine temporal scale. Here, using a high-frequency sampling strategy and 16S rRNA gene amplicon sequencing, we investigated dynamics of larval shrimp bacterial community and its relationship with bacterioplankton in the rearing water across the whole developmental cycle in a realistic aquaculture practice.ResultsAlpha-diversity of larval shrimp bacteria showed a U-shaped pattern across the developmental cycle with the stages zoea and mysis as the valley. Correspondingly, the compositions of dominant bacterial taxa at the stages nauplius and early postlarvae were more complex than other stages. Remarkably, Rhodobacteraceae maintained the overwhelming dominance after the mouth opening of larvae (zoea I~early postlarvae). The taxonomic and phylogenetic compositions of larval bacterial community both showed stage-dependent patterns with higher rate of taxonomic turnover, suggesting that taxonomic turnover was mainly driven by temporal switching among closely related taxa (such as Rhodobacteraceae taxa). The assembly of larval bacteria was overall governed by neutral processes (dispersal among individuals and ecological drift) at all the stages, but bacterioplankton also had certain contribution during three sub-stages of zoea, when larval and water bacterial communities were most associated. Furthermore, the positive host selection for Rhodobacteraceae taxa from the rearing water during the zoea stage and its persistent dominance and large predicted contribution to metabolic potentials of organic matters at post-mouth opening stages suggest a crucial role of this family in larval microbiome and thus a potential source of probiotic candidates for shrimp larval nursery.ConclusionsOur results reveal pronounced succession patterns and dynamic assembly processes of larval shrimp bacterial communities during the developmental cycle, highlighting the importance of the mouth opening stage from the perspective of microbial ecology. We also suggest the possibility and potential timing in microbial management of the rearing water for achieving the beneficial larval microbiota in the nursery practice.EV4FFVE7Wr7jezsPpZE3f6Video

Продукционные характеристики копепод Arctodiaptomus salinus и Calanipeda aquaedulcis при питании смесью микроводорослей Dinophyceae и Prymnesiophyceae

Убиквитные виды копепод Arctodiaptomus salinus (Daday, 1885) и Calanipeda aquaedulcis (Krichagin, 1873) — важные компоненты пищевых цепей многочисленных пресных и солёных водоёмов. Данные копеподы пригодны для кормления личинок как морских, так и пресноводных видов рыб, однако влияние питания на продукционные характеристики этих видов копепод изучено недостаточно. Ранее нами было определено, что монокультуры микроводорослей Dinophyceae и Prymnesiophyceae являются оптимальными кормовыми объектами для продуцирования яиц самками A. salinus и C. aquaedulcis, выживаемости и скорости развития этих копепод на всём протяжении их онтогенеза. Цель данной работы заключалась в определении продукционных характеристик копепод A. salinus и C. aquaedulcis в оптимальных температурных условиях в зависимости от варианта питания смесью микроводорослей Dinophyceae и Prymnesiophyceae. Наиболее высокие значения выживаемости A. salinus от науплиальной до взрослой стадии развития (93–95 %) отмечены при питании копепод монокультурой микроводоросли Isochrysis galbana (Parke, 1949) и смесью I. galbana + Prorocentrum cordatum (Ostenfeld) J. D. Dodge, 1975; наименьшая продолжительность развития (19 суток) — при кормлении смесью из трёх микроводорослей I. galbana + P. cordatum + Prorocentrum micans (Ehrenberg, 1834). Наименьшая средняя продолжительность развития C. aquaedulcis от науплиальной до взрослой стадии развития (13 сут.) зафиксирована при питании смесью микроводорослей I. galbana + P. cordatum. Наименьшая продолжительность науплиального периода развития копепод обоих видов отмечена тогда, когда в состав их диеты входила I. galbana в качестве моно- или одного из компонентов смеси. Такая же закономерность сохраняется для копеподитного периода, только уже с P. cordatum. Максимальная абсолютная плодовитость C. aquaedulcis достигала 24 яиц на самку (I. galbana), A. salinus — 16 яиц на самку (P. cordatum). Выклев C. aquaedulcis при питании как монокультурами микроводорослей P. cordatum и I. galbana, так и их смесью достигал 100 %. Для A. salinus только питание самок смесью микроводорослей I. galbana + P. micans обуславливает максимальный процент выклева.

From swimming towards sessility in two metamorphoses – the drastic changes in structure and function of the nervous system of the bay barnacle Amphibalanus improvisus (Crustacea, Thecostraca, Cirripedia) during development

Knowledge about the development of the nervous system in cirripeds is limited, particularly with regard to the changes that take place during the two metamorphoses their larvae undergo. This study delivers the first detailed description of the development of the nervous system in a cirriped species, Amphibalanus improvisus by using immunohistochemical labeling against acetylated alpha-tubulin, and confocal laser scanning microscopy. The development of the nervous system in the naupliar stages corresponds largely to that in other crustaceans. As development progresses, the protocerebral sensory organs differentiate and the intersegmental nerves forming the complex peripheral nervous system appear, innervating the sensory structures of the cephalic shield. During metamorphosis into a cypris the lateral sides of the cephalic shield fold down into a bilateral carapace, which leads to a reorganization of the peripheral nervous system. The syncerebrum of the cypris exhibits the highest degree of complexity of all developmental stages, innervating the frontal filaments, nauplius eye, compound eyes and the antennules. During settlement, when the second metamorphosis occur, the closely associated frontal filaments and compound eyes are shed together with the cuticle of the carapace and the antennules. In adults, the syncerebral structures are reduced while the ventral nerve cord and the peripheral nervous system increase in complexity. The peripheral nervous system plays an important role in processing sensory input and also in settlement. In summary, through the larval development we observed a structural and thus also functional increase of complexity in favor of the peripheral nervous system and the ventral nerve cord.

Patterns of Bacterial Community Composition and Diversity Following the Embryonic Development Stages of Macrobrachium rosenbergii

During the evolution of aquatic animals, co-evolution between host and microbes has been overlooked. Previous studies have shown that microbes were present in the fertilized egg of fish, but compared with fish, little information is available for crustaceans. High-throughput Illumina Miseq DNA sequencing of the V3-V4 domain of the 16S rRNA gene was used to assess the microbial community composition during different stages of embryonic development in Macrobrachium rosenbergii: fertilized egg stage (OM1), cleavage stage (OM2), blastula stage (OM3), gastrula stage (OM4), egg nauplius stage (OM5), egg metanauplius stage (OM6), protozoea stage (OM7) and zoea stage (OM8). Water samples (WMZ) were also assessed. The results showed that Proteobacteria (82.92%), Bacteroidetes (9.27%), and Actinobacteria (4.49%) were the predominant phylum in the M. rosenbergii embryo. At the genus level, the microbial composition was constantly changing during embryonic development. We concluded that OM3 and OM4 might be the critical stage for transformation of the microbial composition in the M. rosenbergii embryo. The main factor responsible for microbial colonization in the embryo was primarily selective pressure exerted by the shrimp, while the microbial community in the water environment had a lower impact. This study describes bacterial communities in different stages of embryonic development in M. rosenbergii, and the effects of the surrounding environment on microbial colonization. These findings provide valuable information for further studies examining the formation of early intestinal flora in crustaceans.

Rotational Maneuvers of Copepod Nauplii at Low Reynolds Number

Copepods are agile microcrustaceans that are capable of maneuvering freely in water. However, the physical mechanisms driving their rotational motion are not entirely clear in small larvae (nauplii). Here we report high-speed video observations of copepod nauplii performing acrobatic feats with three pairs of appendages. Our results show rotations about three principal axes of the body: yaw, roll, and pitch. The yaw rotation turns the body to one side and results in a circular swimming path. The roll rotation consists of the body spiraling around a nearly linear path, similar to an aileron roll of an airplane. We interpret the yaw and roll rotations to be facilitated by appendage pronation or supination. The pitch rotation consists of flipping on the spot in a maneuver that resembles a backflip somersault. The pitch rotation involved tail bending and was not observed in the earliest stages of nauplii. The maneuvering strategies adopted by plankton may inspire the design of microscopic robots, equipped with suitable controls for reorienting autonomously in three dimensions.

EXPERIMENTAL RESEARCH FOR TECHNOLOGICAL PREPARATION OF ARTEMIA (ARTEMIA) ARTIFICIAL CULTIVATION IN SALT LAKES

An integral part of the technological preparation of artificial cultivation of brine shrimp in saline water is a set of preliminary experimental work to assess the quality of cysts. It has been shown that during the winter period, activation of Artemia cysts occurs from the initial hatching values of 5-10 % to 72-99 %. The most optimal salinity range for hatching nauplii is a salinity of 20-30 g/l. With an increase in salinity above these indicators, hatching decreases. The size of hatching of Artemia depends on the salinity of a natural reservoir. In reservoirs with salinity of 50-80 g / l, higher hatching rates were obtained than with salinity of 150-160 g/l. Higher hatching rates are observed when using natural lake water for incubation. During incubation of cysts in a standard solution and fixed salinity and temperature conditions, the development rate of various stages of nauplii from the beginning of the opening of cysts (breaking stage) and pre-nauplius to active nauplii is shown. After 1.5–2 h after the mass appearance of pre-nauplii, they completely change into the nauplius stage.

Effects of multigenerational rearing, ontogeny and predation threat on copepod feeding rhythms

Marine planktonic copepods frequently exhibit diel feeding cycles coupled with vertical migrations. However, copepod feeding rhythms can be influenced by factors others than different food availability between layers. In this study, we determined the changes in the diel feeding behaviour of two marine copepod species (Centropages typicus and Paracartia grani) through multigenerational laboratory rearing, ontogeny, and upon the exposure to predator chemical cues. The wild females of both C. typicus and P. grani showed marked feeding rhythms with higher ingestion rates at night. The diel rhythms of C. typicus were maintained in the first laboratory-reared generation (F1), suggesting maternal effects, but disappeared in the following generations. The P. grani females of a long-term culture (> 10 years) also showed no differences in their day–night feeding activity. Ontogenetic variations were detected in the F1 generation of C. typicus: feeding rhythms were absent in naupliar stages, but adults fed more intensely at night. In the case of the cultured P. grani, in general none of the stages showed feeding rhythms. Laboratory-reared C. typicus (8–11 generations) did not recover back the natural cyclic feeding when exposed to jellyfish and fish exudates, indicating that either predation risk does not significantly affect their diel feeding activity or predator-induced responses in marine copepods might not involve chemical signalling. Our study confirms that feeding-related functional traits of marine copepods can experience quick multigenerational changes in the laboratory; consequently, cultured copepods might not be good models for studies involving their diel feeding behaviour.

Resilience of the Copepod Oithona similis to Climatic Variability: Egg Production, Mortality, and Vertical Habitat Partitioning

There has been an overall decline in copepod populations across the North Atlantic over the past few decades. Reasons for these declines are unclear, and several major species, including the cyclopoid copepod Oithona similis, have maintained stable populations at station L4 in the western English Channel. To identify the factors contributing to this stability, we conducted a one-year intensive study of O. similis at L4 over 2017-2018, a period of high climatic variability. For context, dominant frequency state analysis was applied to the 30-year L4 time series to derive the baseline dynamics of the Oithona spp. population. The Oithona spp. baseline demonstrated stable densities and a bimodal annual cycle. These dynamics, as well as those of reproductive output and phenological timings, were upheld in 2017-2018, indicating resilience to climatic variability. During 2017-2018, all life stages of O. similis were relatively scarce in the top 2 m of the water column, despite the presence of abundant food. Naupliar stages occurred predominantly around 10 m depth, with subsequent life stages progressively deeper. We suggest this vertical structuring may represent different trade-offs between feeding and mortality risk between ontogenetic stages. To determine the traits that contribute to population stability, we compare O. similis with the large, biomass-dominant copepod, Calanus helgolandicus. Despite having contrasting functional traits, both species have exhibited strong population stability over the time series. Our results provide evidence that mortality plays a major role in maintaining population dynamics.

Early life stages of Calanus pacificus are neither exposed nor sensitive to low pH waters

Abstract We characterized the vertical distribution of Calanus pacificus eggs and larvae and the carbonate chemistry that they are exposed to in Puget Sound, WA. We found that, under stratified conditions, more than 90% of eggs and nauplii stages 1–4 were distributed above the pycnocline, in seawater with pH higher than 7.7. In addition, eggs and larvae from 101 females were reared for 5 days under a range of pH conditions (7.2–8.0) to investigate how pH sensitivity varies among individuals. We observed a slight increase in naupliar survival at pH 7.3 in Individual Brood experiments, while in Mixed Brood experiments, exposure to pH 7.3 led to a small decline in hatching success. In a Split Brood experiment, inter-individual variability among different females’ broods masked pH effects. These results indicate that C. pacificus early life stages are generally tolerant to short-term direct effects of ocean acidification.

A new process for nauplius production of the freshwater fairy-shrimp Dendrocephalus brasiliensis (Pesta, 1921) and the effect of enzymatic and chemical treatment on hatching

The freshwater microcrustacean Dendrocephalus brasiliensis, known as branchoneta, has been considered for use as an alternative live feed for commercial aquatic organisms during larval development. However, there are limited studies on techniques to improve nauplii hatching. Thus, the aim of this work was to develop a method for reproduction and cyst recovery, following a new process for nauplius production by the enzymatic action of chitinase and/or chemical treatment. The physical and chemical water parameters and hatching rate were monitored, while morphological changes on nauplii were evaluated after enzyme and chemical treatment by Scanning Electron Microscopy. A hatching protocol was developed for the use of Ca(OH)2, ascorbic acid and enzyme, wherein the most efficient concentration of enzyme for hatching cysts was determined. The concentrations of commercial chitinase tested were 0.008 U·mL−1, 0.08 U·mL−1 and 0.16 U·mL−1 in 20 mg of cysts, which resulted in the ideal concentration of 0.16 U·mL−1 yielding 88% hatching efficiency. Therefore, the concentration of 0.16 U·mL−1 was used for the second experimental test, which consisted of a control and five experimental treatments with three replicates. In T1, the cysts were subjected to chitinase, T2 to calcium hydroxide, T3 to ascorbic acid, T4 to calcium hydroxide and ascorbic acid and T5 to calcium hydroxide, ascorbic acid and chitinase. The use of the enzyme showed an increase in the hatching rate of the branchoneta, and the addition of calcium hydroxide and ascorbic acid further increased the hatching efficiency of the nauplii (96%). At the naupliar stage one, the treatment with the use of chitinase, calcium hydroxide and ascorbic acid did not present morphological alterations in nauplii. In larval stage two, nauplii already initiate alterations in the region of the abdomen with T5, with segments developed for the naupliar stage. Therefore, the use of enzyme associated with chemicals promotes an increase in hatching when compared to the traditional hatching process. Moreover, this treatment also promotes a reduction of hatching time, as >80% of total hatching was observed on the first day. The proposed protocol could be used for the hatching of branchoneta cysts for the use of nauplii offered as food until naupliar stage 2 in fish and shrimp larviculture.

Acute toxicity of glyphosate on various life stages of calanoid copepod, Pseudodiaptomus annandalei

Copepods are one of the most important primary producers and biodiversity indicators. They are also highly susceptible to various toxicants. In this study, glyphosate (Roundup®), a widely used herbicide was used to investigate the toxicity effect on calanoid copepods, Pseudodiaptomus annandalei, focused on their nauplius, copepodid, and adult stages. Different concentrations of glyphosate (i.e. 0 - as control, 0.05, 0.1, 0.4, 1.6, 6.4 and 25.6 mg/L) were used to elucidate the tolerance level of P. annandalei. The survival rate of copepod was recorded at the intervals of 24, 48, 72 and 96 h after glyphosate exposure. The analysis was performed using probit test to determine the sub-lethal concentrations. Our results revealed that LC50 of the nauplius stage was recorded as 3.47, 3.02, 1.86 and 1.10 mg/L at 24, 48, 72 and 96 h, respectively. Higher LC50 values were recorded at 4.36 mg/L for 24 h, 3.09 mg/L for 48 h, 2.00 mg/L for 72 h, and 1.12 mg/L for 96 h at the copepodid stage. Generally, adult copepods showed a higher level of tolerance to glyphosate among all stages, whereby at this stage LC50 values were recorded as 11.70 mg/L for 24 h,10.23 mg/L for 48 h, 7.41 mg/L for 72 h, and 3.61 mg/L for 96 h, respectively. Our results indicated that prolong exposure time of glyphosate could increase the susceptibility of P. annandalei to the herbicide. Nauplii are the most sensitive group among all. This study showed that glyphosate could post significant eco-toxicological impact to the non-targeted organism.

BIODIVERSITY STUDY OF ZOOPLANKTON IN SELECTED BAHR Al-NAJAF DEPRESSION, NAJAF GOVERNORATE, IRAQ

The current study aims to assess zooplankton diversity in Bahr Al-Najaf depression using diversity index, specimens were collected from five sites at Bahr Al-Najaf depression, Iraq during April 2017 to March 2018. Forty-eight taxa of zooplankton were identified including 26 taxa to Copepoda, 17 taxa belonged to Rotifers and 5 taxa to Cladocera: Copepoda was the most dominant group (54.2%); Rotifera comprised (35.4%); Cladocera comprised (10.4%). Relative abundance index of zooplankton showed Copepodite and nauplii of Harpacticoid, Hexarthra mira, Daphnia sp., Harpacticoid sp., and Copepodite and nauplii of Cyclops were more abundant. According to the constancy index, the Copepodite and nauplii of Harpacticoid, nauplii Cyclops, nauplii stage and Hexarthra mira can be considered as the most frequent; Shanon-Weiner diversity index values of zooplankton recorded less value 0.48 in August 2017 at site (5); while the higher value was recorded in April 2017 at site (2) was 2.42; the higher value of species richness index was recorded in April 2017 at site (2) which was (7.2), the higher value of species uniformity index was recorded in February at site (2) and March at site (1) (0.61). The present study concluded that Copepoda was the most abundant of zooplankton with variations in zooplankton species (density and from month to another).

BIODIVERSITY STUDY OF ZOOPLANKTON IN SELECTED BAHR Al-NAJAF DEPRESSION, NAJAF GOVERNORATE, IRAQ

The current study aims to assess zooplankton diversity in Bahr Al-Najaf depression using diversity index, specimens were collected from five sites at Bahr Al-Najaf depression, Iraq during April 2017 to March 2018. Forty-eight taxa of zooplankton were identified including 26 taxa to Copepoda, 17 taxa belonged to Rotifers and 5 taxa to Cladocera: Copepoda was the most dominant group (54.2%); Rotifera comprised (35.4%); Cladocera comprised (10.4%). Relative abundance index of zooplankton showed Copepodite and nauplii of Harpacticoid, Hexarthra mira, Daphnia sp., Harpacticoid sp., and Copepodite and nauplii of Cyclops were more abundant. According to the constancy index, the Copepodite and nauplii of Harpacticoid, nauplii Cyclops, nauplii stage and Hexarthra mira can be considered as the most frequent; Shanon-Weiner diversity index values of zooplankton recorded less value 0.48 in August 2017 at site (5); while the higher value was recorded in April 2017 at site (2) was 2.42; the higher value of species richness index was recorded in April 2017 at site (2) which was (7.2), the higher value of species uniformity index was recorded in February at site (2) and March at site (1) (0.61). The present study concluded that Copepoda was the most abundant of zooplankton with variations in zooplankton species (density and from month to another).

Sequence and expression analysis of HSP70 family genes in Artemia franciscana

Thus far, only one gene from the heat shock protein 70 (HSP70) family has been identified in Artemia franciscana. Here, we used the draft Artemia transcriptome database to search for other genes in the HSP70 family. Four novel HSP70 genes were identified and designated heat shock cognate 70 (HSC70), heat shock 70 kDa cognate 5 (HSC70-5), Immunoglobulin heavy-chain binding protein (BIP), and hypoxia up-regulated protein 1 (HYOU1). For each of these genes, we obtained nucleotide and deduced amino acid sequences, and reconstructed a phylogenetic tree. Expression analysis revealed that in the juvenile state, the transcription of HSP70 and HSC70 was significantly (P < 0.05) higher in a population of A. franciscana selectively bred for increased induced thermotolerance (TF12) relative to a control population (CF12). Following non-lethal heat shock treatment at the nauplius stage, transcription of HSP70, HSC70, and HSC70-5 were significantly (P < 0.05) up-regulated in TF12. In contrast, transcription of the other HSP70 family members in A. franciscana (BIP, HYOU1, and HSPA4) showed no significant (P > 0.05) induction. Gene expression analysis demonstrated that not all members of the HSP70 family are involved in the response to heat stress and selection and that especially altered expression of HSC70 plays a role in a population selected for increased thermotolerance.

Molecular cloning, expression pattern analysis, and in situ hybridization of a Transformer-2 gene in the oriental freshwater prawn, Macrobrachium nipponense (de Haan, 1849)

In this study, we isolated a full-length cDNA sequence from Macrobrachium nipponense and investigated its gene function. We named the gene Mntra-2a because of high similarities and close evolutionary divergence with arthropod tra-2. The full-length cDNA of Mntra-2a was 1293bp, consisting of a 212bp 5' UTR, a 268bp 3' UTR, and an ORF of 813bp encoding 270 amino acids. It contained an RNA recognition motif and a linker region. Real-time PCR analysis showed that Mntra-2a was highly expressed in the gonads of both males and females. Further in situ hybridization analysis showed that Mntra-2a was mainly located in oocytes and spermatocytes. During embryogenesis, Mntra-2a expression was higher in the cleavage and nauplius stages. During the ovarian reproductive cycle, Mntra-2a expression reached a peak at OvaryV and decreased to the lowest level at OvaryIV. These results indicated that Mntra-2a probably played important roles in embryonic development and early gonad development in M. nipponense. Our results provide basic information for further functional studies of tra-2 in M. nipponense.