Immunolocalization of Na+,K+-ATPase in the branchial cavity during the early development of the crayfish Astacus leptodactylus (Crustacea, Decapoda)

Comparative transcriptome analysis of the gills of Cardisoma armatum provides novel insights into the terrestrial adaptive related mechanism of air exposure stress

Cardisoma armatum is a typical member of the Gecarcinidae which show significant behavioral, morphological, physiological, and/or biochemical adaptations permitting extended activities on the land. The special gills (branchiostegal lung) of C. armatum play an important role in maintaining osmotic pressure balance and obtaining oxygen to adapt to the terrestrial environment. However, adaptive molecular mechanisms responding to air exposure in C. armatum are still poorly understood. In this study, transcriptomic analysis and histological analysis were conducted on the gills to test adaptive capabilities over 8 h between the aerial exposure (AE) and the water immersion (WI) group. Differentially expressed genes (DEGs) related to terrestrial adaptation were categorized into four broad categories: ion transport, acid-base balance, energy metabolism and immune response. This is the first research to reveal the molecular mechanism of terrestrial adaptation in C. armatum, and will provide new insight into the molecular genetic basis of terrestrial adaptation in crabs.

Salinity Variation in a Mangrove Ecosystem: A Physiological Investigation to Assess Potential Consequences of Salinity Disturbances on Mangrove Crabs

Dimitri Theuerkauff, Georgina A. Rivera-Ingraham, Jonathan A.C. Roques, Laurence Azzopardi, Marine Bertini, Mathilde Lejeune, Emilie Farcy, Jehan-Hervé Lignot, and Elliott Sucré (2018) Salinity is one of the main environmental factors determining coastal species distribution. However, in the specific case of mangrove crabs, salinity selection cannot be understood through ecological approaches alone. Yet understanding this issue is crucial in the context of mangrove conservation, since this ecosystem is often used as biofilter of (low- salinity) wastewater. Crabs are keystone species in this mangrove ecosystem and are differentially affected by salinity. We hypothesize that crab salinity selection may be partly explained by specific salinity-induced physiological constraints associated with osmoregulation, energy and redox homeostasis. To test this, the response to salinity variation was analysed in two landward mangrove crabs: the fiddler crab Tubuca urvillei, which inhabits low-salinity areas of the mangrove, and the red mangrove crab Neosarmatium meinerti, which lives in areas with higher salinity. Results confirm that both species are strong hypo-/hyper-osmoregulators that deal easily with large salinity variations. Such shifts in salinity do not induce changes in energy expenditure (measured as oxygen consumption) or in the production of reactive oxygen species. However, T. urvillei is physiologically suited to habitats with brackish water, since it presents i) high hemolymph osmolalities over a wider range of salinities and lower osmoregulatory capacity in seawater, ii) high Na+/K+-ATPase (NKA) activity in the posterior osmoregulatory gills and iii) a thicker osmoregulatory epithelium along the posterior gill lamellae. Therefore, while environmental salinity alone cannot directly explain fiddler and red mangrove crab distributions, our data suggest that salinity selection is indeed influenced by specific physiological adjustments.

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.

Transcriptomic analysis of adaptive mechanisms in response to sudden salinity drop in the mud crab, Scylla paramamosain

Background

Scylla paramamosain (Crustacea: Decapoda: Portunidae: Syclla De Hann) is a commercially important mud crab distributed along the coast of southern China and other Indo-Pacific countries (Lin Z, Hao M, Zhu D, et al, Comp Biochem Physiol B Biochem Mol Biol 208-209:29–37, 2017; Walton ME, Vay LL, Lebata JH, et al, Estuar Coast Shelf Sci 66(3–4):493–500, 2006; Wang Z, Sun B, Zhu F, Fish Shellfish Immunol 67:612–9, 2017). While S. paramamosain is a euryhaline species, a sudden drop in salinity induces a negative impact on growth, molting, and reproduction, and may even cause death. The mechanism of osmotic regulation of marine crustaceans has been recently under investigation. However, the mechanism of adapting to a sudden drop in salinity has not been reported.

Methods

In this study, transcriptomics analysis was conducted on the gills of S. paramamosain to test its adaptive capabilities over 120 h with a sudden drop in salinity from 23 ‰ to 3 ‰.

Results

At the level of transcription, 135 DEGs (108 up-regulated and 27 down-regulated) annotated by NCBI non-redundant (nr) protein database were screened. GO analysis showed that the catalytic activity category showed the most participating genes in the 24 s-tier GO terms, indicating that intracellular metabolic activities in S. paramamosain were enhanced. Of the 164 mapped KEGG pathways, seven of the top 20 pathways were closely related to regulation of the Na⁺ / K⁺ -ATPase. Seven additional amino acid metabolism-related pathways were also found, along with other important signaling pathways.

Conclusion

Ion transport and amino acid metabolism were key factors in regulating the salinity adaptation of S. paramamosain in addition to several important signaling pathways.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-4803-x) contains supplementary material, which is available to authorized users.

The Legs Have It: In Situ Expression of Ion Transporters V-Type H(+)-ATPase and Na(+)/K(+)-ATPase in the Osmoregulatory Leg Organs of the Invading Copepod Eurytemora affinis

The copepod Eurytemora affinis has an unusually broad salinity range, as some populations have recently invaded freshwater habitats independently from their ancestral saline habitats. Prior studies have shown evolutionary shifts in ion transporter activity during freshwater invasions and localization of ion transporters in newly discovered "Crusalis organs" in the swimming legs. The goals of this study were to localize and quantify expression of ion transport enzymes V-type H(+)-ATPase (VHA) and Na(+)/K(+)-ATPase (NKA) in the swimming legs of E. affinis and determine the degree of involvement of each leg in ionic regulation. We confirmed the presence of two distinct types of ionocytes in the Crusalis organs. Both cell types expressed VHA and NKA, and in the freshwater population the location of VHA and NKA in ionocytes was, respectively, apical and basal. Quantification of in situ expression of NKA and VHA established the predominance of swimming leg pairs 3 and 4 in ion transport in both saline and freshwater populations. Increases in VHA expression in swimming legs 3 and 4 of the freshwater population (in fresh water) relative to the saline population (at 15 PSU) arose from an increase in the abundance of VHA per cell rather than an increase in the number of ionocytes. This result suggests a simple mechanism for increasing ion uptake in fresh water. In contrast, the decline in NKA expression in the freshwater population arose from a decrease in ionocyte area in legs 4, likely resulting from decreases in number or size of ionocytes containing NKA. Such results provide insights into mechanisms of ionic regulation for this species, with added insights into evolutionary mechanisms underlying physiological adaptation during habitat invasions.

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

The role of the main ion transporting enzyme Na+/K+-ATPase in osmoregulation processes was investigated in Litopenaeus stylirostris. The development and localization of the osmoregulation sites were studied during ontogenesis by immunodetection of Na(+)K(+)-ATPase using monoclonal antibodies and transmission electron microscopy (TEM). Osmoregulation sites were identified as the pleurae and branchiostegites in the zoeae and mysis stages. In the subsequent post-metamorphic stages the osmoregulatory function was mainly located in the epipodites and branchiostegites and osmotic regulation was later detected in the gills. The presence of ionocytes and microvilli in these tissues confirmed their role in ionic processes. The complete open reading frame of the mRNA coding for the α-subunit of Na+K+-ATPase was characterized in L. stylirostris. The resulting 3092-bp cDNA (LsNKA) encodes a putative 1011-amino-acid protein with a predicted molecular mass of 112.3kDa. The inferred amino acid sequence revealed that the putative protein possesses the main structural characteristics of the Na+K+-ATPase α-subunits. Quantitative RT-PCR analyses indicated that LsNKA transcripts did not significantly vary between the different developmental stages. The number of transcripts was about 2.5-fold higher in the epipodites and gills than in any other tissues tested in juveniles. A reverse genetic approach was finally implemented to study the role of LsNKA in vivo. Knockdown of LsNKA expression by gene-specific dsRNA injection led to an increase of shrimp mortality following an abrupt salinity change compared to control animals. These data strongly suggest that LsNKA plays an important role in osmoregulation when the shrimp are challenged by changing salinities.

Cellular and molecular osmoregulatory responses to cadmium exposure in Gammarus fossarum (Crustacea, Amphipoda)

Osmoregulation represents a reliable indicator of the physiological state of crustaceans. It is mainly effected in gills via Na(+)/K(+)-ATPase (NKA) providing the major driving force for ion transport. In the present study conducted in the freshwater amphipod Gammarus fossarum, the impact of an exposure to 15 μg Cd L(-1) for 3 and 7d was investigated on the haemolymph osmolality (HO), gill structure, NKA localization in gills and its relative expression. In Cd-exposed G. fossarum, mean HO significantly decreased compared to controls. In animals exposed for 3 and 7d, high inter-individual variations in HO values were noted, resulting in their separation into unimpacted, slightly impacted and impacted animals. In unimpacted individuals, gills retained their organization, showing a thicker gill epithelium than in controls; NKA fluorescence was continuously observed along the gill epithelium and was distributed on a broader area than in controls. In slightly impacted individuals, a thinner epithelium, a slight collapse of the gill and a lower NKA fluorescence were observed compared to unimpacted specimens. In impacted individuals, dramatic alterations of the gill structure, including hyperplasia and alteration of the pillars, resulting in the collapse of the gill and the disappearance of the haemolymphatic canals were observed, as well as very limited NKA fluorescence. Therefore, the degree of gill alteration and the intensity of NKA fluorescence observed in the different groups were correlated with their respective HO levels. The relative amount of the NKA α-subunit mRNA significantly increased in specimens exposed to Cd for 3d compared to controls, and then returned to control level after 7d. The relationships between the changes in HO values, NKA immunostaining and mRNA relative expression are discussed. These results confirm that HO represents a valuable biomarker to evaluate crustacean health, and they underline the interest to assess individual responses to contaminants.

Expression of Na(+)/K(+)-ATPase alpha-subunit mRNA during embryonic development of the crayfish Astacus leptodactylus

Astacus leptodactylus is a decapod crustacean fully adapted to freshwater where it spends its entire life cycle after hatching under huge osmoconcentration differences between the hemolymph and surrounding freshwater. We investigated the expression of mRNA encoding one ion transport-related protein, Na(+)/K(+)-ATPase alpha-subunit, and one putative housekeeping gene, beta-actin, during crayfish ontogenesis using quantitative real-time PCR. A 216-amino acid part of the open reading frame region of the cDNA coding for the Na(+)/K(+)-ATPase alpha-subunit was sequenced from total embryo, juvenile and adult gill tissues. The predicted amino acid sequence showed a high percentage similarity to those of other invertebrates (up to 95%) and vertebrates (up to 69%). beta-actin expression exhibited modest changes through embryonic development and early post-embryonic stage. The Na(+)/K(+)-ATPase alpha-subunit gene was expressed in all studied stages from metanauplius to juvenile. Two peaks of expression were observed: one in young embryos at 25% of embryonic development (EI=100 mum), and one in embryos just before hatching (at EI=420 mum), continuing in the freshly hatched juveniles. The Na(+)/K(+)-ATPase expression profile during embryonic development is time-correlated with the occurrence of other features, including ontogenesis of excretory antennal glands and differentiation of gill ionocytes linked to hyperosmoregulation processes and therefore involved in freshwater adaptation.

Ultrastructural Studies and Na+,K+-ATPase Immunolocalization in the Antennal Urinary Glands of the LobsterHomarus gammarus(Crustacea, Decapoda)

Unlike in crustacean freshwater species, the structure and ultrastructure of the excretory antennal gland is poorly documented in marine species. The general organization and ultrastructure of the cells and the localization of Na+,K+-ATPase were examined in the antennal gland of the adult lobster Homarus gammarus. Each gland is composed of a centrally located coelomosac surrounded ventrally by a labyrinth divided into two parts (I and II) and dorsally by a voluminous bladder. There is no differentiated nephridal tubule between them. The labyrinth and bladder cells have in common a number of ultrastructural cytological features, including basal membrane infoldings associated with mitochondria, apical microvilli, and cytoplasmic extrusions, and a cytoplasm packed with numerous vacuoles, vesicles, lysosome-like bodies, and swollen mitochondria. Each type of cell also presents distinctive characters. Na+,K+-ATPase was detected through immunofluorescence in the basal part of the cells of the labyrinth and in the bladder cells with an increasing immunostaining from labyrinth I to the bladder. No immunoreactivity was detected in the coelomosac. The cells of the labyrinth and of the bladder present morphological and enzymatic features of ionocytes. The antennal glands of the lobster thus possess active ion exchanges capabilities.