Population structure and reproduction of the alvinocaridid shrimp Rimicaris exoculata on the Mid-Atlantic Ridge: Variations between habitats and vent fields

Reproduction in deep‐sea vent shrimps is influenced by diet, with rhythms apparently unlinked to surface production

“…Embryonic stages in broods were identified and classified in three developmental stages (early, mid, and late) as seen through their transparent envelope. Briefly, early stage includes freshly fertilized eggs until the blastula stage, mid‐stage starts with gastrulation and extends to the end of the naupliar development (embryonic structures clearly separated from yolk), and late stage includes post‐naupliar development when abdomen, appendages, and larval structures become fully developed (Hernandez‐Avila et al, 2021 ; Methou et al, 2019 ).…”

“…In addition, although the brooding state of females from the YK01‐15 (2002) expedition could be assessed, poor storage condition of these samples did not allow egg count or measurement analyses. An additional published dataset for Rimicaris exoculata collected at TAG and Snake Pit in January–February 2014 (BICOSE cruise) is also included in our analyses (Hernández‐Ávila et al, 2021 ), the raw data of which are available in the Ifremer/SEANOE (SEA scieNtific Open data Edition) database at: https://doi.org/10.17882/84112 . As the 2014 dataset was produced by a different observer than the present study, a subsample of 60 broods from 2014 were measured again by the observer who produced the 2017 and 2018 datasets, and compared with the 2014 dataset produced by Hernández‐Ávila et al ( 2021 ).…”

“…Attempts to understand the reproduction of Rimicaris shrimps have so far been inconclusive due to contradicting evidences. As with most carideans (Correa & Thiel, 2003 ), Rimicaris shrimps are gonochoric, with the females brooding their eggs under the abdomen until the larva hatches (Hernández‐Ávila et al, 2021 ; Ramirez‐Llodra et al, 2000 ). While aperiodic reproduction was initially suggested from the examination of their reproductive tissues (Copley et al, 2007 ; Ramirez‐Llodra et al, 2000 ), very few ovigerous individuals were collected in over 35 years of seagoing expeditions, despite a relatively focused and repeated sampling effort (Copley et al, 2007 ; Komai & Segonzac, 2008 ; Ramirez‐Llodra et al, 2000 ; Shank et al, 1998 ; Vereshchaka, 1997 ; Williams and Rona, 1986 ).…”

“…While aperiodic reproduction was initially suggested from the examination of their reproductive tissues (Copley et al, 2007 ; Ramirez‐Llodra et al, 2000 ), very few ovigerous individuals were collected in over 35 years of seagoing expeditions, despite a relatively focused and repeated sampling effort (Copley et al, 2007 ; Komai & Segonzac, 2008 ; Ramirez‐Llodra et al, 2000 ; Shank et al, 1998 ; Vereshchaka, 1997 ; Williams and Rona, 1986 ). Brooding females were first found in small numbers in 2007 (Guri et al, 2012 ), and much greater numbers were recovered in 2014 (Hernández‐Ávila et al, 2021 ; Methou et al, 2019 ), around a restricted time period between January and March. These females were living within dense aggregations close to vent orifices (Hernández‐Ávila et al, 2021 ), refuting the previous hypothesis that brooding females would migrate to the vent periphery to protect their eggs from vent fluid, as observed for bythograeid crabs (Perovich et al, 2003 ) and Kiwa squat lobsters (Marsh et al, 2015 ).…”

“…Brooding females were first found in small numbers in 2007 (Guri et al, 2012 ), and much greater numbers were recovered in 2014 (Hernández‐Ávila et al, 2021 ; Methou et al, 2019 ), around a restricted time period between January and March. These females were living within dense aggregations close to vent orifices (Hernández‐Ávila et al, 2021 ), refuting the previous hypothesis that brooding females would migrate to the vent periphery to protect their eggs from vent fluid, as observed for bythograeid crabs (Perovich et al, 2003 ) and Kiwa squat lobsters (Marsh et al, 2015 ). Taken together, these recent findings are suggestive of a seasonal reproductive cycle possibly linked to surface primary production, as shown in vent crabs, bathymodiolin mussels, and some other alvinocaridid shrimps (Copley & Young, 2006 ; Dixon et al, 2006 ; Tyler et al, 2007 ).…”