First observations of the bigfin squid Magnapinna sp. in the Colombian Southern Caribbean

Abstract Herein, first observations are reported of Magnapinna squids in the Colombian Southern Caribbean. Two specimens were observed by Remote Operated Vehicles (ROV) during exploratory drilling surveys for hydrocarbons at 1,883 and 2,294 m depth. These are the first observations of specimens of Magnapinna in the Southern Caribbean. Resumen La primera observación del calamar Magnapinna sp. en el caribe sur colombiano. Dos especímenes de calamares de aleta grande fueron observados con submarino de operación remota (ROV) durante un proyecto de perforación exploratoria de hidrocaburos a profundidades de 1,883 y de 2,294 m, respectivamente. Estas son las primeras observaciones de especímenes de Magnapinna en el Caribe Sur.

According to the morphology of the specimens (Fig. 1a, b, c) they were identified as members of the genus Magnapinna Young, 1998 (Magnapinnidae Vecchione &Young, 1998) (Vecchione et al. 2001, Vecchione andYoung 2016). Unfortunately, the species cannot be determined without close examination of some details of the arm and tentacle suckers and these details were not possible to see with the videos provided by the ROV in the two sightings. It was thus not possible to get confirmation of the species. This is a common problem with photographic identification of invertebrates. A review of the videos however, confirmed the family and genus (Michael Vecchione, Smithsonian Institute, Washington DC, personal communication).
The size of the specimens, estimated through comparison with the riser (set of tubes that connect the well with the drilling unit) is of approximately 200 mm mantle length; fin width 200 mm and a total length of ca. 2,300 mm. The individuals exhibited characteristics of fully developed animals: one specimen had its complete arm arrangement with all its filaments, the other specimen lacked the filament on one arm.
The poorly known deep-sea family Magnapinnidae, where only eleven specimens are known and deposited in collections worldwide, is presently understood to comprise five species: Magnapinna pacifica Vecchione & Young, 1998, M. atlantica Vecchione & Young, 2006, M. talismani (Fischer & Joubin, 1907, Mangapinna sp. B and Magnapinna sp. C (Vecchione and Young 1998, Vecchione and Young 2006, Vecchione and Young 2016. Vecchione et al. (2001) described the occurrence of a large, strange squid recorded only by submersible or ROV observations in the Atlantic, Indian and Pacific Oceans. Magnapinnid species are characterised by unique brachial morphology amongst all known cephalopods: the thicker regions of the arms and tentacles are often held at nearly right angles to the body axis and the long, slender portions of the arms and tentacles that trail the squid are nearly parallel to the body axis. Magnapinnids are likely found, at least in temperate to tropical latitudes, throughout the world's oceans at great depths within a few meters from the bottom. The deepest record is 4,735 m depth in the western Atlantic off the coast of Brazil (Vecchione et al. 2001, Vecchione andYoung 2016). Magnapinna has been reported in the Great Caribbean and Gulf of Mexico by ROV sightings at the offshore exploratory well "Perdido" and during deep-sea research, respectively (Guerra et al. 2002). These are the first observations known for the family in the Southern Caribbean.
Until now, 49 species of cephalopods were known for the Colombian Caribbean (Guerrero-Kommritz 2015), most from shallow water (Diaz et al. 2000. The only reports from deeper water are for Semirossia spp. and Austrorossia spp. from 500 and 790 m depth (Guerrero-Kommritz and Rodriguez-Bermudez 2017). This is the first report of a Magnapinnid (and of any deep-sea oegopsid) squid in the Colombian Caribbean.

Acknowledgements
Thanks to I-TECH Services (a division of Subsea 7) and its entire technical staff for conducting the ROV. Their time and patience made it possible to get the videos we were a b c Figure 1.