Characterization of the gene repertoire and environmentally driven expression patterns in Tanner crab (Chionoecetes bairdi)

Tanner crab (Chionoecetes bairdi) are an economically important species that is threatened by ocean warming and Bitter Crab Disease, which is caused by an endoparasitic dinoflagellate, Hematodinium. Little is known about disease transmission or its link to host mortality, or how ocean warming will affect pathogenicity or host susceptibility. To provide a transcriptomic resource for the Tanner crab we generated a suite of RNA-seq libraries encompassing pooled hemolymph samples from crab displaying differing infection status and maintained at different temperatures (ambient (7.5˚C), elevated (10˚C), or decreased (4˚C)). After assembling a transcriptome and performing a multifactor differential gene expression analysis, we found genes influenced by temperature in relation to infection, and detected some of those genes over time at the individual level using RNAseq data from one crab. Biological processes associated with those genes include lipid storage, transcription, response to oxidative stress, cell adhesion, and morphogenesis. Alteration in lipid storage and transcription provide insight into how temperature impacts energy allocation in Hematodinium infected crabs. Alteration in expression patterns in genes associated with morphogenesis could suggest hemocytes were changing morphology and/or type in response to temperature. This project provides insight into how Hematodinium infection could influence crab physiology as oceans warm.

Potential impact of harvesting on Tanner crab (Chionoecetes bairdi) on state of its commercial stock off the coast of Kamchatka

Potential impact of landing on the stock and biological state of Tanner crab is analyzed for two fishery districts at Kamchatka in 2013-2020. In the Kamchatka-Kuril fishery subzone, the number of commercial males without limbs and with old shell increased in catches that may be associated with active operations of alive-crab vessels in 2015-2017. In the Petropavlovsk-Commander fishery subzone, cases of injured Tanner crabs catch became frequent after resumption of the crab harvesting in 2017, as well as the cases of commercial crabs with old shell, that also could be explained by operations of alive-crab vessels. The operations of such vessels are distinguished by strict sorting of caught crabs with removing the individuals of lower quality. As the result, the crabs without limbs and commercial males at late stages before molting were accumulated in the areas of sorting. The problem can be solved by measures for total registration (weighting) of catch before the start of sorting, concerning to all crabs with commercial size landed aboard. To avoid degradation of the Tanner crab population, development of catch processing aboard fishing vessels is recommended, with transportation of frozen products instead of live crabs.

Characterization of the Gene Repertoire and Environmentally Driven Expression Patterns in Tanner Crab ( Chionoecetes Bairdi )

Tanner crab ( Chionoecetes bairdi ) are an economically important species that is threatened by ocean warming and Bitter Crab Disease, which is caused by an endoparasitic dinoflagellate, Hematodinium . Little is known about disease transmission or its link to host mortality, or how ocean warming will affect pathogenicity or host susceptibility. To betterunderstand how temperature and infection influence host physiology, we performed a temporal transcriptomic analysis on crab infected with Hematodinium and uninfected crab exposed to either ambient (7.5˚C), elevated (10˚C), or decreased (4˚C) temperature treatments. After assembling a transcriptome and performing a multifactor differential gene expression analysis, we found genes influenced by temperature in relation to infection, and detected some of those genes over time at the individual level using RNAseq data from one crab. Biological processes associated with those genes include lipid storage, transcription, response to oxidative stress, cell adhesion, and morphogenesis. Alteration in lipid storage and transcription provide insight into how temperature impacts energy allocation in Hematodinium infected crabs. Alteration in expression patterns in genes associated with morphogenesis could suggest hemocytes were changing morphology and/or type in response to temperature. This project provides insight into how Hematodinium infection could influence crab physiology as oceans warm.

Ocean acidification alters properties of the exoskeleton in adult Tanner crabs, Chionoecetes bairdi

ABSTRACTOcean acidification can affect the ability of calcifying organisms to build and maintain mineralized tissue. In decapod crustaceans, the exoskeleton is a multilayered structure composed of chitin, protein and mineral, predominately magnesian calcite or amorphous calcium carbonate (ACC). We investigated the effects of acidification on the exoskeleton of mature (post-terminal-molt) female southern Tanner crabs, Chionoecetes bairdi. Crabs were exposed to one of three pH levels – 8.1, 7.8 or 7.5 – for 2 years. Reduced pH led to a suite of body region-specific effects on the exoskeleton. Microhardness of the claw was 38% lower in crabs at pH 7.5 compared with those at pH 8.1, but carapace microhardness was unaffected by pH. In contrast, reduced pH altered elemental content in the carapace (reduced calcium, increased magnesium), but not the claw. Diminished structural integrity and thinning of the exoskeleton were observed at reduced pH in both body regions; internal erosion of the carapace was present in most crabs at pH 7.5, and the claws of these crabs showed substantial external erosion, with tooth-like denticles nearly or completely worn away. Using infrared spectroscopy, we observed a shift in the phase of calcium carbonate present in the carapace of pH 7.5 crabs: a mix of ACC and calcite was found in the carapace of crabs at pH 8.1, whereas the bulk of calcium carbonate had transformed to calcite in pH 7.5 crabs. With limited capacity for repair, the exoskeleton of long-lived crabs that undergo a terminal molt, such as C. bairdi, may be especially susceptible to ocean acidification.

On reproductive biology of tanner crab Chionoecetes bairdi Rathbun, 1924 (Crustacea, Decapoda) females at southeastern Kamchatka

Fecundity and some other reproductive characteristics of tanner crab Chionoecetes bairdi females are studied for the first time in the area at southeastern Kamchatka on the materials collected in spring and summer aboard research vessels (in 2016 and 2019) and fishing boats (in 2020). The females with new eggs prevailed in the catches. The size of functional sexual maturity was determined as 79 mm. The implemented fertility was estimated as 93.4 ± 28.1.103 eggs in 2016 and 115.7 ± 24.5.103 eggs in 2019, on average. Reproductive effort and K/r-coefficient were evaluated; their relatively high values confirmed r-strategy of tanner crab reproduction.

CURRENT STATE OF STOCK FOR TANNER CRAB CHIONOECETES BAIRDI RATHBUN, 1924 (CRUSTACEA, DECAPODA) AT THE SOUTH-EASTERN COAST OF KAMCHATKA

Tanner crab Chionoecetes bairdi is the highly valuable object of commercial fishery dwelling in the seas surrounding Kamchatka Peninsula. Its landings started at the southeastern coast of Kamchatka in early 1980s and continued till 2009, when the fishery was stopped by reasons independent on the stock state. It was launched again in 2017. Now the species is landed mostly in the Petropavlovskaya fishery subzone (62 % of the total allowable catch of tanner crab in Russia in 2019), whereas its stocks at southwestern Kamchatka and in the northwestern Bering Sea are rather low. Modern condition of the tanner crab population and its distribution at southeastern Kamchatka are considered on the data of the trap surveys conducted in spring and summer of 2012 and 2018. Between these years, commercial males of these species spread wider at southeastern Kamchatka and formed commercial aggregations in the northern Avachinsky Bay and in the southern and central parts of the Kronotsky Bay, but were rare southward from Cape Povorotny. They became larger: while size of the males varied in the range 50–170 mm in both years, the males with the carapace width < 120 mm prevailed in 2012, but the large-sized males with commercial size were more numerous in 2018. Percentage of the females in the catches was low both in 2012 and 2018 that is typical for the trap catches. The crabs at the 3rd stage of molting dominated both in May and August of 2012 and 2018. Injury level of the commercial males was rather high and increased from 2012 to 2018 in 8 %. Good current condition of the tanner crab population at southeastern Kamchatka is concluded.