Ontogeny of osmoregulation in the Pacific blue shrimp, Litopenaeus stylirostris (Decapoda, Penaeidae): Deciphering the role of the Na(+)/K(+)-ATPase

Function of taurine and its synthesis-related genes in hypertonic regulation of Sinonovacula constricta

Salinity changes affect the osmotic gradient across the gill epithelium of marine species. Taurine is an important osmoregulator with a crucial role in osmoregulation in marine bivalves. This study determined the osmolality, taurine content, key enzymes involved in taurine synthesis (cysteine dioxygenase (CDO), cysteine sulfinic acid decarboxylase (CSAD), and taurine transporter (TauT)) and related gene expression in razor clam Sinonovacula constricta in response to high salt stress [high salt seawater (S30) versus high salt seawater with taurine supplementation (S30T) versus natural salinity control]. The data were recorded at 0, 6, 12, 24, 48, 72 h. Serum osmolality significantly increased under high salt conditions compared with the control group (P < 0.05). When serum osmolality had stabilized (after 48 h), there was no significant difference in serum osmolality between the S30T and control groups (P > 0.05), but serum osmolality was significantly lower in the S30 versus control group (P < 0.05). Taurine content significantly increased under high salt stress and remained high (P < 0.05). CSAD and CDO content was higher in S30 than in S30T, whereas TauT was significantly lower in S30 than in the control group eventually (P < 0.05). Expression of CDO and CSAD in the S30 and S30T groups was significantly higher than in control animals (P < 0.05), with that in S30 being higher than in S30T. By contrast, TauT expression peaked 6 h after stress in S30 and S30T, but was lower in S30 than in the control group (P < 0.05). These results demonstrate that S. constricta is an osmoconformer, with exogenous taurine relieving the stress of osmoregulation caused by insufficient endogenous taurine in cells. These findings further enhance our understanding of the regulatory mechanisms underlying the response of S. constricta to high salinity stress.

Waterless live transport degrades the flesh quality of Litopenaeus vannamei by disturbing neuroendocrine response: based on physiology and metabolomics

BACKGROUND

Shrimp is one of the most popular marine foods consumed throughout the world and its freshness is a crucial indicator for consumers. However, the flesh quality degradation of shrimp during waterless live transport has been observed and the underlying mechanism remains unknown.

RESULTS

The present study aimed to clarify the biochemistry mechanisms of flesh degradation with integration of quality evaluation, metabolic profiling and histopathological analysis. The flesh quality indicators such as water holding capacity, protein and lipid contents, amino acid composition and myofiber components degraded with the prolongation of combined stress. In addition, the metabolites including gamma-aminobutyric acid, Val-Ala, Trh and derivatives of carnitine, phosphocholine and prostaglandin all reduced significantly under combined stress (P < 0.05). Furthermore, Kyoto Encyclopedia of Genes and Genomes (https://www.genome.jp/kegg) analysis revealed the enrichment of neuroactive ligand-receptor interaction and estrogen signaling pathways, indicating the involvement of neuroendocrine in stress response. Moreover, architecture impairment in hepatopancreas tissue verified the accumulation of metabolic disturbance.

CONCLUSION

Taken together, the findings of the present study indicate that neuroendocrine system mediates the flesh degradation of L. vannamei during waterless transport by disturbing the biochemical metabolic pathways and inducing architecture impairment of myofibril components. © 2022 Society of Chemical Industry.

Ontogenetical development of branchial chambers of Litopenaeus vannamei (Boone, 1931) and their involvement in osmoregulation: ionocytes and Na+/K+-ATPase

Branchial chambers constitute the main osmoregulatory site in almost all decapod crustaceans. However, few studies have been devoted to elucidate the cellular function of specific cells in every osmoregulatory structure of the branchial chambers. In decapod crustaceans, it is well-known that the osmoregulatory function is localized in specific structures that progressively specialize from early developmental stages while specific molecular mechanisms occur. In this study, we found that although the structures developed progressively during the larval and postlarval stages, before reaching juvenile or adult morphology, the osmoregulatory capabilities of Litopenaeus vannamei were gradually established only during the development of branchiostegites and epipodites, but not gills. The cellular structures of the branchial chambers observed during the larval phase do not present the typical ultrastructure of ionocytes, neither Na⁺/K⁺-ATPase expression, likely indicating that pleura, branchiostegites, or bud gills do not participate in osmoregulation. During early postlarval stages, the lack of Na⁺/K⁺-ATPase immunoreactivity of the ionocytes from the branchiostegites and epipodites suggests that they are immature ionocytes (ionocytes type I). It could be inferred from IIF and TEM results that epipodites and branchiostegites are involved in iono-osmoregulation from PL15, while gills and pleura do not participate in this function.

Characterization, functional analysis, and expression levels of three carbonic anhydrases in response to pH and saline-alkaline stresses in the ridgetail white prawn Exopalaemon carinicauda

Carbonate alkalinity, salinity, and pH are three important stress factors for aquatic animals in saline-alkaline water. Carbonic anhydrases (CAs) catalyze the reversible reaction of CO2 reported to play an important role in the acid-base regulation in vertebrates. To explore the molecular mechanism of CAs efficacy in shrimp after their transfer into saline-alkaline water, the cDNAs of three CAs (EcCAc, EcCAg, and EcCAb) were cloned from Exopalaemon carinicauda. Sequence analysis showed that EcCAc and EcCAg both possessed a conserved α-CA domain and a proton acceptor site, and EcCAb contained a Pro-CA domain. Tissue expression analysis demonstrated that EcCAc and EcCAg were most abundantly in gills, and EcCAb was highly expressed in muscle. The cumulative mortalities remained below 25% under exposure to pH (pH 6 and pH 9), low salinity (5 ppt), or high carbonate alkalinity (5 and 10 mmol/L) after 72 h of exposure. However, mortalities increased up to 70% under extreme saline-alkaline stress (salinity 5 ppt, carbonate alkalinity 10 mmol/L, and pH 9) after 14 days of exposure. The EcCAc and EcCAg expressions in gills were significantly upregulated during the early period of pH and saline-alkaline stresses, while the EcCAb expressions showed no regular or large changes. The two-way ANOVA found significant interactions between salinity and carbonate alkalinity observed in EcCAc, EcCAg, and EcCAb expressions (p < 0.05). Furthermore, an RNA interference experiment resulted in increased mortality of EcCAc- and EcCAg-silenced prawns under saline-alkaline stress. EcCAc knockdown reduced expressions of Na+/H+ exchanger (EcNHE) and sodium bicarbonate cotransporter (EcNBC), and EcCAg knockdown reduced EcCAc, EcNHE, EcNBC, and V-type H+-ATPase (EcVTP) expressions. These results suggest EcCAc and EcCAg as important modulators in response to pH and saline-alkaline stresses in E. carinicauda.

Protein kinase C mediates juvenile hormone-dependent phosphorylation of Na+/K+-ATPase to induce ovarian follicular patency for yolk protein uptake

In oviparous animals, vitellogenesis is prerequisite to egg production and embryonic growth after oviposition. For successful insect vitellogenesis and oogenesis, vitellogenin (Vg) synthesized in the fat body (homologue to vertebrate liver and adipose tissue) must pass through the intercellular channels, a condition known as patency in the follicular epithelium, to reach the surface of oocytes. This process is controlled by juvenile hormone (JH) in many insect species, but the underlying mechanisms remain elusive. Previous work has suggested the possible involvement of Na⁺/K⁺-ATPase in patency initiation, but again, the regulatory cascade of Na⁺/K⁺-ATPase for patency initiation has been lacking. Using the migratory locust Locusta migratoria as a model system, we report here that RNAi-mediated knockdown of gene coding for Na⁺/K⁺-ATPase, inhibition of its phosphorylation, or suppression of its activity causes loss of patency, resulting in blocked Vg uptake, arrested oocyte maturation, and impaired ovarian growth. JH triggers G protein-coupled receptor (GPCR), receptor tyrosine kinase (RTK), phospholipase C (PLC), inositol trisphosphate receptor (IP3R), and protein kinase C (PKC) to phosphorylate Na⁺/K⁺-ATPase α-subunit at amino acid residue Ser⁸, consequently activating Na⁺/K⁺-ATPase for the induction of patency in vitellogenic follicular epithelium. Our results thus point to a previously unidentified mechanism by which JH induces the phosphorylation and activation of Na⁺/K⁺-ATPase via a signaling cascade of GPCR, RTK, PLC, IP3R, and PKC. The findings advance our understanding of JH regulation in insect vitellogenesis and oogenesis.

Expression of Na+/K+-ATPase Was Affected by Salinity Change in Pacific abalone Haliotis discus hannai

Na⁺/K⁺-ATPase (NKA) belongs to the P-type ATPase family, whose members are located in the cell membrane and are distributed in diverse tissues and cells. The main function of the NKA is to regulate osmotic pressure. To better understand the role of NKA in osmoregulation, we first cloned and characterized the full-length cDNAs of NKA α subunit and β subunit from Pacific abalone Haliotis discus hannai in the current study. The predicted protein sequence of the NKA α subunit, as the catalytic subunit, was well conserved. In contrast, the protein sequence of the β subunit had low similarity with those of other species. Phylogenetic analysis revealed that both the α and β subunits of the NKA protein of Pacific abalone were clustered with those of the Gastropoda. Then, the relationship between salinity changes and the NKA was investigated. Sudden salinity changes (with low-salinity seawater (LSW) or high-salinity seawater (HSW)) led to clear changes in ion concentration (Na⁺ and K⁺) in hemolymph; however, the relative stability of ion concentrations in tissue revealed that Pacific abalone has a strong osmotic pressure regulation ability when faced with these salinity changes. Meanwhile, the expression and activity of the NKA was significantly decreased (in LSW group) or increased (in HSW group) during the ion concentration re-establishing stages, which was consistent with the coordinated regulation of ion concentration in hemolymph. Moreover, a positive correlation between cyclic adenosine monophosphate (cAMP) concentrations and NKA mRNA expression (NKA activity) was observed in mantle and gill. Therefore, the sudden salinity changes may affect NKA transcription activation, translation and enzyme activity via a cAMP-mediated pathway.

An atlas of larval organogenesis in the European shore crab Carcinus maenas L. (Decapoda, Brachyura, Portunidae)

BACKGROUND

The life history stages of brachyuran crustaceans include pelagic larvae of the Zoea type which grow by a series of moults from one instar to the next. Zoeae actively feed and possess a wide range of organ systems necessary for autonomously developing in the plankton. They also display a rich behavioural repertoire that allows for responses to variations in environmental key factors such as light, hydrostatic pressure, tidal currents, and temperature. Brachyuran larvae have served as distinguished models in the field of Ecological Developmental Biology fostering our understanding of diverse ecophysiological aspects such as phenotypic plasticity, carry-over effects on life-history traits, and adaptive mechanisms that enhance tolerance to fluctuations in environmental abiotic factors. In order to link such studies to the level of tissues and organs, this report analyses the internal anatomy of laboratory-reared larvae of the European shore crab Carcinus maenas. This species has a native distribution extending across most European waters and has attracted attention because it has invaded five temperate geographic regions outside of its native range and therefore can serve as a model to analyse thermal tolerance of species affected by rising sea temperatures as an effect of climate change.

RESULTS

Here, we used X-ray micro-computed tomography combined with 3D reconstruction to describe organogenesis in brachyuran larvae. We provide a detailed atlas of the larval internal organization to complement existing descriptions of its external morphology. In a multimethodological approach, we also used cuticular autofluorescence and classical histology to analyse the anatomy of selected organ systems.

CONCLUSIONS

Much of our fascination for the anatomy of brachyuran larvae stems from the opportunity to observe a complex organism on a single microscopic slide and the realization that the entire decapod crustacean bauplan unfolds from organ anlagen compressed into a miniature organism in the sub-millimetre range. The combination of imaging techniques used in the present study provides novel insights into the bewildering diversity of organ systems that brachyuran larvae possess. Our analysis may serve as a basis for future studies bridging the fields of evolutionary developmental biology and ecological developmental biology.

Gene silencing reveals multiple functions of Na+/K+-ATPase in the salmon louse (Lepeophtheirus salmonis)

Na⁺/K⁺-ATPase has a key function in a variety of physiological processes including membrane excitability, osmoregulation, regulation of cell volume, and transport of nutrients. While knowledge about Na⁺/K⁺-ATPase function in osmoregulation in crustaceans is extensive, the role of this enzyme in other physiological and developmental processes is scarce. Here, we report characterization, transcriptional distribution and likely functions of the newly identified L. salmonis Na⁺/K⁺-ATPase (LsalNa⁺/K⁺-ATPase) α subunit in various developmental stages. The complete mRNA sequence was identified, with 3003 bp open reading frame encoding a putative protein of 1001 amino acids. Putative protein sequence of LsalNa⁺/K⁺-ATPase revealed all typical features of Na⁺/K⁺-ATPase and demonstrated high sequence identity to other invertebrate and vertebrate species. Quantitative RT-PCR analysis revealed higher LsalNa⁺/K⁺-ATPase transcript level in free-living stages in comparison to parasitic stages. In situ hybridization analysis of copepodids and adult lice revealed LsalNa⁺/K⁺-ATPase transcript localization in a wide variety of tissues such as nervous system, intestine, reproductive system, and subcuticular and glandular tissue. RNAi mediated knock-down of LsalNa⁺/K⁺-ATPase caused locomotion impairment, and affected reproduction and feeding. Morphological analysis of dsRNA treated animals revealed muscle degeneration in larval stages, severe changes in the oocyte formation and maturation in females and abnormalities in tegmental glands. Thus, the study represents an important foundation for further functional investigation and identification of physiological pathways in which Na⁺/K⁺-ATPase is directly or indirectly involved.