Addisonia cf. excentrica ( Tiberi, 1855 )

Gofas, Serge, Luque, Ángel A., Oliver, Joan Daniel, Templado, José & Serrano, Alberto, 2021, The Mollusca of Galicia Bank (NE Atlantic Ocean), European Journal of Taxonomy 785 (1), pp. 1-114 : 29

Addisonia cf. excentrica ( Tiberi, 1855)

Fig. 3I

Gadinia excentrica Tiberi, 1855: 13 , pl. 2 figs 5–6.

Addisonia excentrica – Watson 1886: 32. — Locard 1898: 93.

Material examined

GALICIA BANK • 1 sh; 42°51′ N, 11°53′ W; 1110‒1125 m; 19 Oct. 1987; SEAMOUNT 1 DW108 ; MNHN • 5 spm; 42°58.50′ N, 11°59.24′ W; 1683 m; 7 Aug. 2011; BANGAL 0711 GOC9 ; MNCN .

Remarks

Three living specimens (3.5, 3.4 and 2.0 mm) were found on the inside surface of an empty egg-capsule of the smalleyed rabbitfish, Hydrolagus affinis (de Brito Capello, 1868) (Holochephali, Chimaeridae). Two specimens (3.5 and 2.0 mm) were attached close to small oval thinner areas or holes on the wall of the egg-capsule ( Fig. 3I ) caused by limpet rasping during feeding ( Dantart & Luque 1994). The shell and the external morphology of the living specimens resemble those of A. excentrica from shallower depths, but given their small size, further anatomical and molecular study is needed to identify them with certainty. As far as we know, this is the deepest record (1683 m) for living specimens of any Addisonia species. Living specimens of Addisonia excentrica were found down to 330‒426 m in the Mediterranean ( Dantart & Luque 1994). The NW Atlantic Addisonia paradoxa ( Dall, 1882) , synonymized with A. excentrica by Dantart & Luque (1994), was found alive by Dall (1882) from 110 to 293 m, and McLean (1985) recorded it from 119 to 1170 m, deepest records being probably shells. Addisonia enodis Simone, 1996 , described from Brazil, was recorded alive down to 184 m ( Simone 1996; Lima et al. 2016) and the NE Pacific A. brophyi McLean, 1985 from 155 to 174 m depth. Besides, this is the first record of an Addisonia species living inside a holocephalan egg-capsule. In addition to two empty eggcapsules (only one of them with Addisonia ), three specimens (2 females and one male) of Hydrolagus affinis were caught in the same sample ( Bañón et al. 2016).

Figures

Fig. 3. Polyplacophora and Gastropoda (Patellogastropoda and Vetigastropoda Lepetelloidea). A–B. Connexochiton platynomenus Kaas, 1979, ECOMARG 0709, G5, 863 m, 4.8 mm. C. Placiphorella atlantica (Verrill & S. Smith, 1882), BANGAL 0711, DR2, 1697 m, 10.3 mm (shipboard photograph by Pilar Ríos, IEO). D–E. Propilidium exiguum (Thompson, 1844), BANGAL 0711, V6, 909 m, 3.8 mm. F–G. Iothia fulva (Müller, 1776), SEAMOUNT 1, DW116, 985–1000 m, 6.3 mm.H. Living Lepetella sp. on a tube of the polychaete Hyalinoecia tubicola (Müller, 1776), BANGAL 0711, V2, 1706 m (shipboard photograph). I. Two small (3.5 and 2.0 mm) living specimens of Addisonia cf. excentrica (Tiberi, 1855) on the inside surface of an egg-capsule of Hydrolagus affinis (de Brito Capello, 1868), near two holes in the wall of the egg-capsule, BANGAL 0711, GOC9, 1683 m (shipboard photograph). Scale bars = 1 mm.