Hydroids (Cnidaria, Hydrozoa) from the Vema and Valdivia seamounts (SE Atlantic)

Abstract

In this report, we analyse the benthic hydroids collected on the Vema and Valdivia seamounts during a survey conducted in 2015 in the SEAFO Convention Area, focused on mapping and analysing the occurrence and abundance of benthopelagic fish and vulnerable marine ecosystem (VMEs) indicators on selected Southeast Atlantic seamounts. A total of 27 hydroid species were identified, of which 22 belong to Leptothecata and only five to Anthoathecata. Monostaechoides gen. nov. was erected within the family Halopterididae to accommodate Plumularia providentiae Jarvis, 1922, and a new species, Monotheca bergstadi sp. nov., is also described. Campanularia africana is recorded for the first time from the Atlantic Ocean, and the Northeast Atlantic species Amphinema biscayana, Stegopoma giganteum and Clytia gigantea are also recorded from the South Atlantic. Three species were identified to the genus level only, due to the absence of their gonosomes. None of the reported species are endemic, and the hydroid community is clearly dominated by species with a wide geographical distribution in the three major oceans. Only Monotheca bergstadi sp. nov. presently has its distribution restricted to the Vema Seamount and the South African coast.

Unveiling the Faunal Diversity in the Water Column Adjacent to Two Seamounts in the Deep Arabian Sea Using Environmental DNA Metabarcoding

“…Many organisms with a calcified exoskeleton, except foraminiferans [67] and mussel Amygdalum sp., Ref. [68] avoid oxygenminimum waters, while nematodes [69][70][71][72]; polychaetes [68] and crustaceans, such as ostracods [73,74], copepods [52] and malacostracans [75,76], are adapted to live in the hypoxic conditions.…”

“…A more diverse group of organisms was found in the water column adjacent to the summit and periphery of SMS3, which were characterized by a high abundance of Hydrozoa and Actinopterygii. Hydrozoans are the dominant group of invertebrates found on the flanks of many seamounts [70]. They follow a life cycle that includes a benthic polyp (hydroid) stage and a pelagic medusan (jellyfish-like) stage [69][70][71][72].…”

“…Hydrozoans are the dominant group of invertebrates found on the flanks of many seamounts [70]. They follow a life cycle that includes a benthic polyp (hydroid) stage and a pelagic medusan (jellyfish-like) stage [69][70][71][72]. However, the molecular phylogeny of these organisms remains poorly explored [80], which hinders our ability to make complete taxonomic assignments for these groups in seamounts.…”

FISH, cephalopods and associated habitats of the Discovery rise seamounts, Southeast Atlantic

“…Data on habitats and biodiversity of this area were produced during Russian, Spanish and Namibian fishing surveys of the Valdivia and Ewing seamounts, where both pot fisheries for the deep-sea red crab (Chaceon erytheiae) and bottom trawl fisheries for pelagic armourhead (Pseudopentaceros richardsoni), splendid alfonsinos (Beryx splendens) and orange-roughy have historically taken place (McPherson, 1984(McPherson, , 1987Zibrowius and Gili, 1990;Fedorov, 1991;Vinichenko and Kakora, 2008;Lopéz Abellán and Holtzhausen 2011;Durán Muñoz et al, 2012 and others). These seamounts (along with Wüst, Vema and Schmitt-Ott seamounts) were targets of a research cruise conducted in 2015 on board the RV Dr. Fridtjof Nansen, as part of an international effort to map and provide ecological descriptions of benthic environments of seamounts in the SEAFO Convention Area (Bergstad et al, 2019a and b;Gil and Ramil, 2021). This effort continued in 2019 in a subsequent cruise of the 'new' RV Dr. Fridtjof Nansen, this time focused on mapping and identifying VMEs on the southerly Discovery Rise seamounts (41-45 • S, 3 • W -3 • E), in areas both open and closed to longline fisheries targeting the Patagonian toothfish (Dissostichus eleginoides).…”