Postlarval Stages Research Articles

Observations on the life history and ecology of Clubiona pacifica Banks in Washington State (Araneae: Clubionidae)

Clubiona pacifica Banks, 1896 is a common secondary occupant of lepidopteran leafrolls on alders (Alnus spp.). We collected rolled alder leaves at riparian sites in Washington State to determine seasonal phenology of C. pacifica and to examine egg laying and predatory activity. All stages of the spider occurred in rolled leaves, and spiders were found in rolled leaves throughout the season. Rolled alder leaves were used by C. pacifica as protected sites in which to molt and spend inactive periods and possibly to seek prey. Field observations and greenhouse experiments indicated that C. pacifica is capable of preying upon leafroller larvae. Occasionally, lepidopteran leafrolls were used by C. pacifica as ready-made chambers in which to oviposit, but more commonly the female spider herself folded an alder leaf to form a protective retreat for oviposition. These egg sac retreats and the associated egg sac are described and illustrated. After eclosion C. pacifica passes through a prelarval stage, a larval stage, and six nymphal stages before reaching adulthood. The principal period of reproduction and egg deposition is June and July, and most post-larval stages of C. pacifica appear to overwinter. We postulate that some individuals require two years to complete their life cycle although others may do so in a shorter time. Three ichneumonid wasps parasitized C. pacifica: Gelis sp. attacked the eggs; Schizopyga frigida and Zaglyptus varipes parasitized immature and adult spiders.

Changes in Symbiotic Microbiota and Immune Responses in Early Development Stages of Rapana venosa (Valenciennes, 1846) Provide Insights Into Immune System Development in Gastropods.

The symbiotic microbiota can stimulate modulation of immune system, which also can promote immune system mature in critical developmental periods. In this study, we have investigated the symbiotic microbiota in Rapana venosa at five early development stages using Illumina high-throughput sequencing, and detected immune responses in larvae. Analysis of the symbiotic microbiota sequences identified that the most abundant phylum was Proteobacteria. Beta diversity analysis indicated that the structure of the symbiotic microbiota dramatically shifted in early development stages. The abundance of immune-related KEGG Orthologs (KOs) also increased in competent larval (J4, 30-day post-hatching) and postlarval after 3 days of metamorphosis (Y5, 33-day post-hatching) stages. Acid phosphatase activity decreased significantly in the Y5 stage, and alkaline phosphatase activity also at a lower level in Y5 stage, whereas lysozyme activities exhibited no remarkable change. Also, the activities of catalase and superoxide dismutase activities decreased dramatically during early development stages of R. venosa. Dramatic changes in the symbiotic microbiota and the immune response mainly occurred in the initially hatched veliger (C1), competent larval (J4) and postlarval (Y5) stages, during which the hosts might experience substantial environmental changes or changes in physiological structure and function. These findings expand our understanding of the stage-specific symbiotic microbiota in R. venosa and the close association between immune system and symbiotic microbiota in mollusks, however, the specific relationship may need more researches are needed to investigated in the future.

Insight into the Regulatory Relationships between the Insulin-Like Androgenic Gland Hormone Gene and the Insulin-Like Androgenic Gland Hormone-binding Protein Gene in Giant Freshwater Prawns (Macrobrachium rosenbergii).

Giant freshwater prawns (Macrobrachium rosenbergii) are commonly found throughout the world. The size of the male giant freshwater prawn is much larger than that of the female. Therefore, understanding the molecular mechanism that underlies the sexual differentiation of M. rosenbergii is of both commercial and scientific importance. Insulin-like androgenic gland hormone (IAG) plays a key role in the differentiation of sex in M. rosenbergii. Although IAG has been investigated, the regulatory relationship between IAG and its binding protein partner, the insulin-like androgenic gland hormone-binding protein (IAGBP), has not been studied in M. rosenbergii. Here, we cloned and characterized the IAGBP from M. rosenbergii (Mr-IAGBP) for the very first time. Transcriptomic analysis showed that Mr-IAGBP mRNA was detected in a wide array of tissues with the highest expression found in the androgenic gland. The importance of IAG in male development was further demonstrated by an increase in IAG transcripts during the development of the androgenic gland and Mr-IAG was only highly transcribed in the androgenic gland of M. rosenbergii. Interestingly, we found that the Mr-IAG gene expression started during the 20th-day larva after hatching stage (LH20), followed (20th-day post-larval stage, PL20) by a gradual elevation of Mr-IAGBP levels. The levels of both genes peaked at the adult stage. The relationship between Mr-IAGBP and Mr-IAG was further analyzed using RNA interference. The injection of Mr-IAGBP double-stranded RNA (dsRNA) significantly reduced the transcription of Mr-IAG, while the amount of Mr-IAGBP mRNA and the translation of IAGBP protein was significantly reduced by the injection of Mr-IAG dsRNA. These results revealed that IAGBP is involved in IAG signaling. Furthermore, our data supports the hypothesis that (IAG and IAGBP)-IAG receptor signaling schemes exist in M. rosenbergii. Our results will provide important information for the further study of determining the sex of M. rosenbergii.

Nitric Oxide Negatively Regulates Larval Metamorphosis in Hard-Shelled Mussel (Mytilus coruscus)

Marine invertebrates undergo distinct life cycles and development processes, and some undergo a metamorphic transition from pelagic larvae to benthic juvenile. Previous studies have shown that the second messenger nitric oxide (NO) plays important roles in regulating larval metamorphosis in marine invertebrates. However, this regulatory function is not conserved. Herein, we investigated the regulatory role of NO in larval metamorphosis in Hard-shelled mussel (Mytilus coruscus). Pharmacological experiments revealed that after exposure to nitric oxide synthase (NOS) inhibitors, the larval metamorphosis rate was increased significantly. By contrast, exposure to NO donors significantly reduced the larval metamorphosis rate. To further investigate the function of NO in metamorphosis, we cloned the NOS cDNA sequence from M. coruscus (McNOS), analyzed amino acid sequences of McNOS from different species, and measured McNOS mRNA temporal expression alongside the molecular chaperone heat shock protein 90 (HSP90) in different larval stages. The results showed that NOS proteins share a highly conserved domain sequence in different species, even in invertebrates and vertebrates, but their classification among invertebrates and vertebrates is not the same. Except for the umbo veliger stage, McNOS mRNA was expressed at low levels in pediveliger larval and post-larvae stage, indicating a potential inhibitory function for NO in larval metamorphosis. Meanwhile, HSP90 mRNA expression was correspondingly high in the umbo veliger stage and lower in the pediveliger larval and post-larvae stage, indicating potential functional synergism. Interestingly, McNOS enzyme activity in different larval stages was inconsistent with its mRNA expression. Metamorphosis assays of pharmacological treatments combined with McNOS and HSP90 gene expression and NOS enzyme activity analyses indicated that NO acts as a suppressor to regulate metamorphosis in M. coruscus, regardless of whether nitric oxide is endogenous or exogenous.

Identification and expression characterization of a novel carboxypeptidase A-like gene (RvCPA) during early developmental stages in the gastropod Rapana venosa (Muricidae)

Rapana venosa is an economically important aquaculture species in China. Carboxypeptidases (CPs) A and B (CPA and CPB, respectively) hydrolyze peptides and proteins and play critical roles in the development of the digestive system in animals. In this study, a full-length CPA-like cDNA sequence from R. venosa (RvCPA) was isolated using RACE, and RvCPA mRNA expression levels were analyzed in different tissues and developmental stages by quantitative real-time PCR. Additionally, the expression patterns of RvCPA under different diets were investigated in competent larvae of R. venosa. The full-length cDNA of the RvCPA gene was 1,810 bp and consisted of a 1,296-bp open reading frame (ORF) encoding 431 aa. Phylogenetic analysis revealed high homology of RvCPA with CPs from Biomphalaria glabrata, Pomacea canaliculata, and Ampullaria crossean. Our results showed that RvCPA had higher expression in the salivary gland than in other tissues and that the expression of RvCPA was dramatically increased in the juvenile (postlarval) stage compared with other stages, indicating that functional changes occur in the larval digestive system during the food habit transition. Furthermore, we found that an animal diet could significantly increase the expression of RvCPA, which may suggest that animal diets can promote the development of the digestive system. This information on a novel CP in R. venosa that participates in digestion and is related to the food habit transition may broaden our understanding of digestive system development during metamorphosis in carnivorous gastropods.

Fatty acid composition of the postlarval daubed shanny (Leptoclinus maculatus) during the polar night

Recent discoveries of high levels of biological activity in the Arctic marine ecosystems during the polar night raise questions regarding the ecophysiology of the pelagic postlarval daubed shanny Leptoclinus maculatus. Of special interest is the composition of the lipid sac—a unique feature not found in other Arctic fishes. Analysis of the fatty acid content of major classes of lipids as membrane—total phospholipids (PL) and storage—triacylglycerols (TAG) in the different postlarvae stages during the polar night is presented in this work for the first time. A high level of monounsaturated fatty acids (MUFAs) (71–74% of the total fatty acids (FA) of TAG) was found in the TAG of the L3-L4* postlarvae stages, among which 20:1(n-9) (28%) and 22:1(n-11) (27–29%) FAs are trophic biomarkers of the zooplankton Calanus spp. Among the polyunsaturated FA (PUFA), the FAs of (n-3) class were dominated (22:6(n-3)—in the PL, and 18:4(n-3)—in the TAG). A decrease in the content of the saturated FA (SFA) and an increase in the MUFA in the structural PL during the transition from the postlarval to the demersal stage were observed. Our analyses of the FA composition of the lipid sac suggest that the fish continues to actively hunt for its preferred prey item Calanus spp. during the polar night.

Probiotics, lactic acid bacteria and bacilli: interesting supplementation for aquaculture

Probiotics administration in aquafeed is known to increase feed consumption and absorption due to their capacity to release a wide range of digestive enzymes and nutrients which can participate in digestion process and feed utilization, along with the absorption of diet components led to an increase in host's health and well-being. Furthermore, probiotics improve gut maturation, prevention of intestinal disorders, predigestion of antinutrient factors found in the feed ingredients, gut microbiota, disease resistance against pathogens and metabolism. The beneficial immune effects of probiotics are well established in finfish. However, in comparison, similar studies are less abundant in the shellfish. In this review, the discussions will mainly focus on studies reported the last 2years. In recent studies, native probiotic bacteria were isolated and fed back to their hosts. Although beneficial effects were demonstrated, some studies showed adverse effects when treated with a high concentration. This adverse effect may be due to the imbalance of the gut microbiota caused by the replenished commensal probiotics. Probiotics revealed greatest effect on the shrimp digestive system particularly in the larval and early post-larval stages, and stimulate the production of endogenous enzymes in shrimp and contribute with improved the enzyme activities in the gut, as well as disease resistance.

Unravelling the paleoecology of flat clams: New insights from an Upper Triassic halobiid bivalve

Flat clams are ubiquitous in marine Triassic and Jurassic deep-water environments, where they are often recovered as mono- or pauci-specific assemblages. Their abundance in deep-water facies deposited under oxygen-depleted conditions suggests a potentially unique, but nevertheless debated, paleoecology. The distribution of Halobia cordillerana in an Upper Triassic hemipelagic succession outcropping at Tsiko Lake, Vancouver Island, Canada, serves as a revealing case study. There, deep-water deposits were investigated using a multi-disciplinary approach including facies description (mineralogical, fossil and organic content), taphonomy, morphometry, microscopy (cathodoluminescence, scanning-electron microscope) and independent paleo-redox proxy constraints (framboidal pyrite distributions, Fe speciation). Overall, halobiids' taphonomy at Tsiko Lake is indicative of in situ accumulations with little or no reworking. Among the hemipelagic deposits, three major litho-biofacies (BFC 1, 2, 3) were identified; paleo-redox proxies indicate that these litho-biofacies were deposited under different oxygen conditions ranging from extreme dysoxic (BFC 1) to dominantly euxinic (BFC 3). The distribution of H. cordillerana is shown to be directly influenced by bottom water oxygenation with this organism peaking both in abundance and dimensions under extreme dysoxic to anoxic conditions (i.e. BFC 1 & 2). Conversely, under prevailing euxinic conditions (i.e. BFC 3), the population of H. cordillerana is dominated by forms at larval or post-larval stage which were presumably killed by water-column euxinia. Thus, although the species is here shown to have lived most likely as an epibenthic recliner, an early (larval) planktonic/nektonic stage is needed to explain its mode of occurrence during dominantly euxinic conditions (i.e. BFC 3), and its wide distribution and rapid expansion. Finally, this study highlights the colonizing capacity of halobiids in case of restored oxygen conditions, stressing the potential significance of flat clams for paleoenvironmental reconstruction.

Effects of live microalgae and algae powder on microbial community, survival, metamorphosis and digestive enzyme activity of Penaeus monodon larvae at different growth stages

Most hatcheries use live microalgae and algae powder for artificial rearing; however, the effects of these different diets on the rearing process and bacterial communities is not clear. In order to investigate the effects of live algae and algal powder on the larval culture of Penaeus monodon. Two kinds of live algae (Chaetoceros muelleri, Thalassiosira weissflogii) and Spirulina powder were used to feed larvae in this study, and the effects on the environmental parameters of water, the digestive enzymes activity of larvae and the bacterial community from the zoea stage to the post larval (PL) stage were explored. The results revealed that feeding larvae with C. muelleri significantly improved the enzymatic activity of amylase and the survival rate of the larvae, and significantly reduce the concentrations of NH4-N, NO2-N and the quantity of Vibrio in the water (P < 0.05). Feeding with T. weissflogii significantly improved the enzymatic activity of lipase and pepsin, and the percentage of metamorphosis (P < 0.05). It suggested that adding live microalgae was beneficial in increasing the diversity of the bacterial community in larvae. Cyanobacteria and Patescibacteria were dominant bacteria in the algal solutions of C. muelleri and T. weissflogii. The entire rearing environment was dominated by two phyla: Bacteroidetes and Proteobacteria. Virgulinella fragilis, the bacteria present in the liquid of C. muelleri and T. weissflogii, accounts for a high proportion of bacteria in the rearing water at the zoea stage. The bacterial community in the zoea stage showed significant negative correlations with NH4-N and NO2-N (P < .05), whereas the bacterial community in the PL stage showed significant positive correlations with NH4-N and NO2-N (P < .05). Saprospiraceae and Microbacteriaceae in the water were significantly positively correlated with NH4-N and NO2-N (P < .05). Feeding larvae with C. muelleri and T. weissflogii and Spirulina powder could increased the abundance of Microbacteriaceae, Devosiaceae and Saprospiraceae at the family level, and increased the abundance of Pseudoalteromonas, Roseovarius and Nautella at genus level. In conclusion, feeding larvae with live microalgae could improve the percentage of metamorphosis and survival rates of larvae by improving the external water environment, enhancing digestion, and regulating bacterial community.

Growth and biochemical composition of hatchery reared Scyllaridae lobster (Thenus australiensis) larval stages, nisto and juvenile first stage

Understanding the nutrition of lobster larvae through the examination of growth and biochemical composition across different life stages is a critical component of aquafeed development of new aquaculture species. Therefore, in the present study, we benchmarked growth and changes in biochemical composition of Thenus australiensis from first larval stage (S1) to the juvenile first stage (J1). The larval cycle was completed in a maximum duration of 31 d and comprised four successive larval stages followed by a post-larvae stage (nisto) and a subsequent moult to J1. Growth during all larval stages, metamorphosis to nisto, and moult to J1 were tracked through the measurement of size (total length, TL and cephalic/carapace width, CW), individual wet (WW) and dry (DW) weights. Bulk samples of all developmental stages were collected and analysed for ash, crude protein, total lipid, nitrogen free extract (NFE) and gross energy of dry matter (DM). Lipid class, fatty acid and mineral composition of S1, S4 and J1 of DM were also measured to provide more detailed analysis of composition. As expected, TL, CW, WW and DW increased with each subsequent stage except for lower TL and CW of the nisto stage when compared to S4 larvae. The DW increases throughout larval development until nisto and was defined by higher ash, crude protein, total lipid and NFE absolute amounts. However, from nisto to J1, total lipid decreased by half. The total lipid of DM increased as larval stages progressed to the nisto phase, declining rapidly when monitored at J1. The accumulation of lipid during the larval phase highlights the importance of building lipid stores to maintain metabolism during the non-feeding nisto stage and moult to J1. Polar lipid was the dominant lipid group in comparison to neutral lipids stores. The energy content of larvae, nisto and J1 reflected the accumulation of lipid over the larval stages and its depletion during the non-feeding nisto stage. The environmental influence on elemental uptake was evident at the moult to J1 with a >4-fold increase in ash content in individual J1 compared to nisto. This was supported by an increase of major mineral constituents of the exoskeleton, particularly, calcium. The present study is the first describing in detail the growth and biochemical composition of all the larval stages until J1 for T. australiensis. The new knowledge on nutrition will support progress in aquafeed development for this new aquaculture species.

Bacterial analysis in the early developmental stages of the black tiger shrimp (Penaeus monodon)

Microbial colonization is an essential process in the early life of animal hosts—a crucial phase that could help influence and determine their health status at the later stages. The establishment of bacterial community in a host has been comprehensively studied in many animal models; however, knowledge on bacterial community associated with the early life stages of Penaeus monodon (the black tiger shrimp) is still limited. Here, we examined the bacterial community structures in four life stages (nauplius, zoea, mysis and postlarva) of two black tiger shrimp families using 16S rRNA amplicon sequencing by a next-generation sequencing. Although the bacterial profiles exhibited different patterns in each developmental stage, Bacteroidetes, Proteobacteria, Actinobacteria and Planctomycetes were identified as common bacterial phyla associated with shrimp. Interestingly, the bacterial diversity became relatively stable once shrimp developed to postlarvae (5-day-old and 15-day-old postlarval stages), suggesting an establishment of the bacterial community in matured shrimp. To our knowledge, this is the first report on bacteria establishment and assembly in early developmental stages of P. monodon. Our findings showed that the bacterial compositions could be shaped by different host developmental stages where the interplay of various host-associated factors, such as physiology, immune status and required diets, could have a strong influence.

Effects of triploidy induction on productive traits of the Caribbean pectinid, Argopecten nucleus (Mollusca: Bivalvia)

Argopecten nucleus is a small size pectinid, whose farming and hatchery technology have been developed at experimental and pilot scales. In order to assess the effectiveness of biotechnological tools for the improvement of productive traits, the effects of triploidy induction on its growth and survival rates at different developmental stages were analyzed. Thus, zygotes that underwent cold-shock treatment (12 °C for 15 min) and untreated zygotes were cultured in the laboratory during their embryonic, larval and post-larval stages, while juvenile and adults were farmed in sea-based suspended systems. Ploidy condition was verified by cytofluorometry. Growth was similar in induced to triploid and untreated larvae and post-larvae. Similarly, no differences were found for shell growth and wet weight in confirmed triploid juveniles and adults, in comparison to diploid individuals. In addition, although no effects of the triploidy induction treatment was observed on the survival of larvae and post-larvae, triploid juveniles and adults exhibited a lower survival than diploids. Thus, the triploid condition did not to confer advantages in terms of growth; instead it caused a decrease on the survival of juveniles and adults, negatively impacting the biomass yield of this pectinid species.

Inventory of ectoparasites in pacific white shrimp (Litopenaeus vannamei) that cultivated with high density

Ectoparasites can attack on pacific white shrimp (Litopenaeus vannamei) which are kept in high density concrete ponds. The purpose of this study was to determine the type, prevalence, infestation and intensity degree of ectoparasites pacific white shrimp Postlarva (PL11 – PL15) stage and Postlarva (PL20 - PL30) stage in Bangil ponds that are cultivated with high density. The method used in this research is a survey method with random sampling. Data were analyzed using T test. The results of this study indicate that there are three genus of ectoparasites both in the pacific white shrimp PL11 - PL15 stage and PL20 - PL30 stage, namely Zoothamnium sp., Vorticella sp. and Epistylis sp. The prevalence of ectoparasites in pacific white shrimp is in the PL20 - PL30 stage at 100% while the prevalence of ectoparasites in the PL11 - PL15 stage is 75%. The level of ectoparasite intensity that attacks the pacific white shrimp (PL11 - PL15) includes a moderate category of 21.8 individuals/head, while the level of intensity of ectoparasites that attacks the pacific white shrimp (PL20 - PL30) includes a very severe category that is 814.05 individuals/head.

Bacterial Community Dynamics During Nursery Rearing of Pacific White Shrimp (Litopenaeus vannamei) Revealed via High-Throughput Sequencing.

A 20-day trial was conducted to reveal bacterial community dynamics in a commercial nursery of larval Litopenaeus vannamei larvae. The bacterial communities in the ambient water were profiled by high-throughput sequencing of the V4-V5 hypervariable region of the 16S rRNA gene. The results indicated that the dominant bacterial phyla between the metamorphosis stage and postlarval stage were Bacteroidetes, Proteobacteria, Cyanobacteria, and Firmicutes, representing more than 80.09% of the bacterial operational taxonomic units. The relative abundance among bacterial phyla notably differed between the two stages. The relative abundance of Cyanobacteria was higher in the metamorphosis stage, while that of Bacteroidetes was higher and more stable in the postlarval stage. At the class level, the relative abundance of Sphingobacteriia and Alphaproteobacteria increased markedly in the postlarval stage, while that of Flavobacteriia decreased. Redundancy analysis showed that bacterial composition in the metamorphosis stage was positively correlated with salinity, alkalinity, and pH, while in the postlarval stage, it was positively correlated with ammonium nitrogen and nitrite nitrogen. Thus, microbial community diversity in the nursery phase varies per rearing stage.

Ontogenetic Development Related to Parental Care of a Neotropical Fish, Pterygoplichthys ambrosettii (Siluriformes: Loricariidae).

This study describes the main ontogenetic changes in the armored catfish Pterygoplichthys ambrosettii from newly hatched larva to adult. The relationship between the degree of development of newly hatched larvae and post-larvae and parental care is discussed. Ontogenetic series containing newly hatched larvae, post-larvae, and juveniles of P. ambrosettii were obtained from the Fish Culture Station of Universidade Estadual Paulista. Adult specimens were collected from the Preto River in the upper Paraná River basin. Morphological, osteological, morphometric, and meristic data and color pattern were analyzed. The species exhibited indirect development, with a distinct post-larval stage after the larval stage. Newly hatched larvae had a well-developed yolk sac and lacked pigmentation. The following characters underwent less change during development and can therefore be useful in taxonomical analyses: odontodes located posteriorly to the preopercle, number of plates on the lateral line, lower lip with three series of papillae, spots on the upper ray of the caudal fin, caudal fin similar to that of the adult, body ventrally covered with dermal plates and odontodes, small irregular spots on head, and typical ventral color pattern of the adult. The morphometric data revealed that most variation in body proportions occurred during less advanced developmental stages. Parental care influenced the ontogenetic development of newly hatched larvae.

Functional analysis of a SoxE gene in the oriental freshwater prawn, Macrobrachium nipponense by molecular cloning, expression pattern analysis, and in situ hybridization (de Haan, 1849).

In this study, a full-length cDNA sequence of SoxE (subgroup E within the Sox family of transcription factors) was cloned from Macrobrachium nipponense and named MnSoxE1. The full-length cDNA of MnSoxE1 is 1748bp, consisting of a 110bp 5' UTR, a 105bp 3' UTR, and a 1533bp ORF that encodes 510 amino acids. Conserved domains showed that MnSoxE1 has a high similarity to the SoxE gene of Penaeus vannamei. Phylogenetic tree analysis classified that MnSoxE1 with the SoxE gene of other arthropods into one clade. These results suggested that MnSoxE1 belongs to the SoxE subgroup. During embryonic development, MnSoxE1 was mainly expressed in the gastrula stage, implicating its involvement in tissue cell differentiation and formation. In the post-larval stages, the expression of MnSoxE1 continued to increase on days 1-10. The expression level in males was significantly higher than that in females. Males are clearly distinguishable from females on post-larval day 25, showing that MnSoxE1 may play a role in promoting early development and germ cell and gonadal differentiation, especially for males. qPCR analysis showed that MnSoxE1 may also be involved in oogonium proliferation during ovary development. Further in situ hybridization analysis revealed that MnSoxE1 was mainly located in oocytes and spermatocytes, especially in sertoli cells, and implies that it may be involved in the development of oocytes and spermatocytes, as well as the maintenance of testes in mature prawns. These results indicate that MnSoxE1 is involved in gonadal differentiation and development in M. nipponense, especially testis development.

Immune and bacterial toxin genes expression in different giant tiger prawn, penaeus monodon post-larvae stages following AHPND-causing strain of vibrio parahaemolyticus challenge

Acute Hepatopancreatic Necrosis Disease (AHPND), a disease caused by Vibrio parahaemolyticus (VpAHPND), kills Penaeid shrimps worldwide, resulting in severe economic losses during aquaculture. To further understand how Penaeus monodon post-larvae (PL) respond towards infection of this pathogenic bacterium, the expression of several important immune and bacterial toxin genes in three stages of P. monodon PL (PL15, PL30 and PL45) upon VpAHPND challenge, were determined. A 20-hrs challenge test with 2.7 × 107 cfu ml−1 of VpAHPND resulted 81, 65 and 1.7% mortality respectively for PL30, PL15 and PL45, indicating that PL30 was most vulnerable to VpAHPND. The immune response of shrimp PL at this stage was robust, with Toll-like receptor (TLR), prophenoloxidase (proPO), lysozyme (lyso) and penaeidin (PEN) augmented approximately 10.7, 4.7, 6.5 and 3.2-fold, respectively. The expression initiated at one hour post-infection (h.p.i), peaked at 16 h.p.i and 20 h.p.i, and decreased at 18 h.p.i, indicating the crucial involvement of these immune related genes in the defence and recovery of the first-line defence mechanisms during VpAHPND infection. This work also revealed that toxR gene represents a good indicator gene for Vibrio detection whereas PIR A, for VpAHPND pathogenicity determination of P. monodon. Overall, these findings provided novel insights into the immune response and VpAHPND susceptibility of different P. monodon PL stages during infection, with outcomes potentially useful in enhancing the application of health therapy and biosecured aquaculture practices to minimize the damaging risk of AHPND towards sustainable production of P. monodon.

Comprehensive expression analysis of the beta integrin from Penaeus monodon indicating its participation in innate immunity and ammonia nitrogen stress response

The aim of the present study was to investigate the function of the beta integrin (PmItgb) in Penaeus monodon. The 3011 bp cDNA sequence of PmItgb was cloned from P. monodon using rapid amplification of cDNA ends (RACE) PCR. Phylogenetic tree analyses indicated that the amino acid sequence of PmItgb should be merged into Fenneropenaeus chinensis (93%). Quantitative real-time PCR (q RT-PCR) revealed that PmItgb mRNA was highly expressed in the hemocytes. In addition, with regard to developmental stages, PmItgb showed significantly higher expression in oosperm, nauplius IV, zoea I and III, and post larval stages than that in other development stages. PmItgb expression in the shrimp epidermis was higher in the postmolt (B) stage, and lower in other molting stages. We also found that Vibrio harveyi and V. anguillarum challenge enhanced PmItgb expression in the hepatopancreas and gills. When PmItgb was inhibited, innate immunity-related genes such as ALF, crustin 1, crustin 7, penaeidin 3, and penaeidin 5 were significantly down-regulated. Furthermore, we demonstrated that PmItgb knock-down by specific dsRNA reduced bacterial clearance. In high ammonia nitrogen concentrations, PmItgb was significantly up-regulated in the hepatopancreas and gills. After PmItgb was silenced, the rate of mortality owing to high ammonia nitrogen concentrations decreased; the expression of related anti-apoptotic genes was up-regulated, and that of the apoptotic genes was slightly down-regulated. These results suggested that PmItgb may be involved in shrimp innate immunity and mediate apoptosis of hepatopancreatic cells induced by high ammonia nitrogen environments.

Unprecedented Enantiospecific Live-cell Nuclear DNA Targeting and Photosensitizing of the Chiral DNA Light-Switch Ru(II) Cationic Complex via Simple Ion-Pairing with Chlorophenolic Counter-anions

Argopecten nucleus is a small size pectinid, whose farming and hatchery technology have been developed at experimental and pilot scales. In order to assess the effectiveness of biotechnological tools for the improvement of productive traits, the effects of triploidy induction on its growth and survival rates at different developmental stages were analyzed. Thus, zygotes that underwent cold-shock treatment (12 °C for 15 min) and untreated zygotes were cultured in the laboratory during their embryonic, larval and post-larval stages, while juvenile and adults were farmed in sea-based suspended systems. Ploidy condition was verified by cytofluorometry. Growth was similar in induced to triploid and untreated larvae and post-larvae. Similarly, no differences were found for shell growth and wet weight in confirmed triploid juveniles and adults, in comparison to diploid individuals. In addition, although no effects of the triploidy induction treatment was observed on the survival of larvae and post-larvae, triploid juveniles and adults exhibited a lower survival than diploids. Thus, the triploid condition did not to confer advantages in terms of growth; instead it caused a decrease on the survival of juveniles and adults, negatively impacting the biomass yield of this pectinid species.

Preliminary note on the morphological characters of penja (amphidromous goby postlarvae) in West Sulawesi and Gorontalo Bay

Penja is the local name for the postlarvae of fish belonging to the Gobioidei, whose appearance at certain times is an amphidromous migration process from the sea to rivers. This group of fish is generally referred to as amphidromous gobies. This study aimed to reveal some facts related to the species diversity of penja based on morphological characteristics. The study was conducted from October 2017 to March 2019 in West Sulawesi and Gorontalo Bay, Indonesia. Amphidromous goby samples at the penja (postlarval) stage were obtained from fishermen’s catches and from traditional markets in each location. The samples obtained were measured and described based on morphological differences. The total length of the sampled penja ranged from 18 mm to 58 mm. All penja were identified as belonging to one of two families, the Gobiidae and Eleotridae. Although the species obtained from the waters of West Sulawesi and Gorontalo Bay were similar, there were variations in species composition (relative abundance) based on observed morphology of penja postlarvae from these two locations.