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The population structure of the blue crab Callinectes sapidus was examined in the Maryland Coastal Bays (MCB) from 2014 to 2016. Crabs were sampled from April to December of each year. Size-frequency distributions showed a strong seasonal cycle, with small crabs being abundant in April, increasing in size through September, with adult crabs observed in the highest proportions from August through October of each year. A subsample of crabs was assayed for hemolymph ecdysone concentrations to examine molting patterns in field-collected blue crabs. Molting was observed throughout the sampling season, peaking in April for immature crabs, with lows in all size classes occurring in October. The mean size at maturity ([L.sub.50]) for females collected in this study was 116 mm carapace width (CW), which is comparable to that reported for the lower Chesapeake Bay (CB) and suggests crabs in the MCB are not significantly smaller as previously thought; however, large crabs (>127 mm CW) appear to make up a smaller proportion of the total population in the MCB than in CB. Ovigerous females were observed at two distinct locations depending on the season, with 13/15 (86.7%) in southern Chincoteague Bay in April and May and 24/41 (58.5%) nearest to the Ocean City Inlet in July and August, indicating two potentially distinct spawning grounds and periods. This work suggests that blue crab reproductive success and general population trends are similar across both systems, with fishing pressure or disease in the MCB potentially explaining the low abundance of adult male crabs. KEY WORDS: population structure. Callinectes sapidus, crustacean ecology, molting, size-frequency distribution, INTRODUCTION Shellfish populations are a major economic resource in the United States, with shellfish making up approximately 57% of all commercial fishery landings in 2016 (NOAA 2018). Because of their [...]

The blue crab Cullinectes sapidus reovirus 1 (CsRV1), a double-stranded RNA virus, belongs to the Class III virus family Reoviridae and infects marine invertebrates, including the blue crab C. sapidus. Callinectes sapidus reovirus 1 levels correlate with disease progression, and high levels of infection usually result in death. To understand CsRV1 disease progression, the impact of CsRV1 infection on the translation initiation machinery in adult female C. sapidus was determined. Using transcriptome analysis of C. sapidus, sequences representing each of the three classes of metazoan eukaryotic translation initiation factor 4E (eIF4E) family members, eIF4E1, eIF4E2. and eIF4E3, as well as the eIF4E-binding protein (4E-BP), were identified as the first description of a Class III eIF4E in decapod crustaceans. Transcripts encoding the three eIF4E family members and 4E-BP are found in all tissues examined by end-point RT-PCR analysis, except for the hypodermis. In the noninfected animals, EIF4E1 transcript levels are ~ 11.5- to 150-fold higher than those of EIF4E2, EIF4E3, or 4EBP in both hemocytes and eyestalk ganglia. In CsRV 1 infected animals, transcript levels of eIF4E family members and 4EBP initially increase in hemocytes and to a much lesser extent in eyestalk ganglia. In hemocytes, EIF4E2, EIF4E3, and 4EBP transcript levels are highest at low levels of infection. By contrast, EIF4E1 transcript levels peak at moderate levels of infection. In the eyestalk ganglia, an endocrine tissue, CsRV1 infection only slightly impacts EIF4E1 and EIF4E2 levels, although more substantial increases in EIF4E3 and 4EBP are seen. These results provide the first window into how CsRV1 infection and disease progression perturb the host C. sapidus eIF4E family members and 4E-BP in different tissues, suggesting nuanced responses of the host translational machinery during disease progression. KEY WORDS: translation initiation factors, eIF4E family, 4E-BP, hemocytes, Callinectes sapidus, CsRV1, infection, INTRODUCTION Since the first discovery of a virus belonging to the family Reoviridae in a crustacean (Vago 1966), there have been numerous reports of double-stranded RNA reo-like viruses in other [...]

Perkinsus marinus , a protozoan and the causative agent of perkinsosis (dermo disease) is a prevalent parasite found within the eastern oyster ( Crassostrea virginica ). In this study, we explore metabolic processes of P. marinus cells under lipid-depleted medium conditions to elucidate the interchanging flux of lipid and carbohydrate metabolism. Although P. marinus can synthesize their own lipids from available nutrients, they display a slower growth in medium not supplemented with lipids as opposed to medium with lipids. Under these conditions, using transcriptomics, we surprisingly observed evidence of stimulated lipid degradation through increased transcription of two core β-oxidation pathway enzymes. Simultaneously, phospholipid biosynthetic pathways were downregulated. Metabolomic analysis supported the transcriptomic results. Most fatty acids were decreased in lipid-deplete medium as opposed to lipid-replete medium, and available glucose was fermented to lactate. A significant increase in the cholesterol derivative zymosterol further supported a downregulation of membrane synthesis under the experimental conditions. A robust tricarboxylic acid (TCA) cycle was apparent by enhanced citrate synthase transcription, and a simultaneous reduction in branched chain amino acids. It is concluded that although P. marinus has the capacity for synthesizing its own lipids, it can respond to lipid deprivation in medium by oxidizing readily available stores, and likely transitioning into a resting stage.