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1. Blue king crab ( Paralithodes platypus ) and red king crab ( P. camtschaticus ) juvenile settlement to nearshore nursery habitats of Saint Paul Island, Pribilof Islands, Alaska

   https://doi.org/10.1139/cjfas-2024-0227  

   Weems, Jared D; Long, W Christopher; Divine, Lauren M; Eckert, Ginny L (January 2025, Canadian Journal of Fisheries and Aquatic Sciences)

   The Pribilof Islands blue king crab ( Paralithodes platypus) fishery collapsed over two decades ago, is considered overfished, and has not recovered in the absence of fishing. Red king crab ( Paralithodes camtschaticus) abundance estimates have exceeded blue king crab for over three decades. We investigated the roles of larval recruitment and habitat availability as potential mechanisms limiting blue king crab recovery. We conducted young-of-year abundance and habitat assessments near Saint Paul Island from 2017 to 2019 and compared these results to 1983–1984 historical data to assess changes in larval supply and benthic substrates. Historically abundant blue king crab settlers were rarely encountered in our surveys. Red king crab settlers, once rare in historical surveys, are now more common throughout the region in low abundance. Benthic habitats did not change over time, as 90% of resampled sites had similar substrates. We conclude that larval supply and not benthic habitat is limiting juvenile recruitment. Our results could inform future fishery rebuilding efforts for blue king crab, which could include approaches to increase larval supply and juvenile recruitment through aquaculture. 

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2. Caribbean king crab larvae and juveniles show tolerance to ocean acidification and ocean warming

   https://doi.org/10.1007/s00227-022-04053-8  

   Gravinese, Philip M.; Perry, Shelby A.; Spadaro, Angelo Jason; Boyd, Albert E.; Enochs, Ian C. (April 2022, Marine Biology)

   Abstract Coastal habitats are experiencing decreases in seawater pH and increases in temperature due to anthropogenic climate change. The Caribbean king crab,Maguimithrax spinosissimus, plays a vital role on Western Atlantic reefs by grazing macroalgae that competes for space with coral recruits. Therefore, identifying its tolerance to anthropogenic stressors is critically needed if this species is to be considered as a potential restoration management strategy in coral reef environments. We examined the effects of temperature (control: 28 °C and elevated: 31 °C) and pH (control: 8.0 and reduced pH: 7.7) on the king crab’s larval and early juvenile survival, molt-stage duration, and morphology in a fully crossed laboratory experiment. Survival to the megalopal stage was reduced (13.5% lower) in the combined reduced pH and elevated temperature treatment relative to the control. First-stage (J1) juveniles delayed molting by 1.5 days in the reduced pH treatment, while second-stage (J2) crabs molted 3 days earlier when exposed to elevated temperature. Juvenile morphology did not differ among treatments. These results suggests that juvenile king crabs are tolerant to changes associated with climate change. Given the important role of the king crab as a grazer of macroalgae, its tolerance to climate stressors suggests that it could benefit restoration efforts aimed at making coral reefs more resilient to increasingly warm and acidic oceans into the future. 

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3. Effects of molting on the expression of ecdysteroid biosynthesis genes in the Y-organ of the blackback land crab, Gecarcinus lateralis

   https://doi.org/10.1016/j.ygcen.2023.114304  

   Benrabaa, Samiha A.M.; Chang, Sharon A.; Chang, Ernest S.; Mykles, Donald L. (September 2023, General and Comparative Endocrinology)

   A pair of Y-organs (YOs) synthesize ecdysteroids that initiate and coordinate molting processes in decapod crustaceans. The YO converts cholesterol to secreted products through a biosynthetic pathway involving a Rieske oxygenase encoded by Neverland (Nvd) and cytochrome P450 monooxygenases encoded by Halloween genes Spook (Spo; Cyp307a1), Phantom (Phm; Cyp306a1), Disembodied (Dib; Cyp302a1), and Shadow (Sad; Cyp315a1). NAD kinase (NADK) and 5-aminolevulinic acid synthase (ALAS) support ecdysteroid synthesis in insects. A 20-hydroxylase, encoded by Shed in decapods and Shade in insects, converts ecdysone to the active hormone 20-hydroxyecdysone (20E). 20E is inactivated by cytochrome P450 26-hydroxylase (Cyp18a1). Contigs encoding these eight proteins were extracted from a Gecarcinus lateralis YO transcriptome and their expression was quantified by quantitative polymerase chain reaction. mRNA levels of Gl-Spo and Gl-Phm were four orders of magnitude higher in YO than those in nine other tissues, while mRNA levels of Gl-NADK and Gl-ALAS were similar in all ten tissues. In G. lateralis induced to molt by multiple leg autotomy, YO mRNA levels of Gl-Nvd, Gl-Spo, Gl-Phm, Gl-NADK, and Gl-ALAS were highest in intermolt and premolt stages and lower in postmolt. Gl-Dib mRNA level was not affected by molt stage. mRNA level of Gl-Sad, which converts 2-deoxyecdysone to ecdysone, was higher in mid-and late premolt stages, when YO ecdysteroidogenic capacity is greatest. Gl-Cyp18a1 mRNA level was highest in intermolt, decreased in premolt stages, and was lowest in postmolt. In animals induced to molt by eyestalk ablation, YO mRNA levels of all eight genes were not correlated with increased hemolymph 20E titers. These results suggest that YO ecdysteroidogenic genes are differentially regulated at transcriptional and translational levels. 

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4. First record of the Harlequin crab Lissocarcinus orbicularis, an obligate symbiont of sea cucumbers, from the Red Sea

   https://doi.org/10.56222/28166531.2023.15  

   Lasley, Robert; Evans, Nathaniel; Paulay, Gustav; Uyeno, Daisuke; Carvalho, Susana (January 2023, Specimen)
5. Hormonal control of the crustacean molting gland: Insights from transcriptomics and proteomics

   https://doi.org/10.1016/j.ygcen.2020.113493  

   Mykles, Donald L.; Chang, Ernest S. (August 2020, General and Comparative Endocrinology)