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

Marta Gil,Fran Ramil

doi:10.5852/ejt.2021.758.1425

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.

Highlights

Seamounts are one of the most ubiquitous components and major biomes of the world oceans (Wessel 2007; Rogers 2018)
Despite the fact that seamount biodiversity still remains unknown or poorly understood (Rowden et al 2010; Clark et al 2012), it is well documented that many seamounts are inhabited by vulnerable marine ecosystems (VMEs) that can be impacted by human activities (Bergstad et al 2019b)
Molecular studies carried out by Schuchert (2005) to explore species boundaries within the genus Coryne found that populations identified as Coryne pusilla from the Mediterranean, Japan and Korea are genetically different from the Northeast Atlantic ones

Summary

Introduction

Seamounts are one of the most ubiquitous components and major biomes of the world oceans (Wessel 2007; Rogers 2018). Distinct formation elevated at least 100 m above the seafloor in this concept, a definition widely accepted in recent literature (Hillier & Watts 2007; Consalvey et al 2010; Yesson et al 2011; Rogers 2018) Linked to these different interpretations, the estimated number of seamounts is highly variable, ranging from around 10 200 (Harris et al 2014) to 68 700 (Costello et al 2010) large seamounts, and up to 25 million in the global ocean when elevations of ≤ 100 m are taken into account (Wessel et al 2010). Despite the fact that seamount biodiversity still remains unknown or poorly understood (Rowden et al 2010; Clark et al 2012), it is well documented that many seamounts are inhabited by vulnerable marine ecosystems (VMEs) that can be impacted by human activities (Bergstad et al 2019b)

Methods

Results

Conclusion