Lirapex felix, Chen & Han & Copley & Zhou, 2021

Chen, Chong, Han, Yuru, Copley, Jonathan T. & Zhou, Yadong, 2021, A new peltospirid snail (Gastropoda: Neomphalida) adds to the unique biodiversity of Longqi vent field, Southwest Indian Ridge, Journal of Natural History 55 (13 - 14), pp. 851-866 : 861

Peltospiridae in the Indian Ocean

The discovery of Lirapex felix sp. nov. increases the peltospirid diversity in Longqi hydrothermal field and the Indian Ocean to five species, of which three ( L. felix sp. nov., L. politus and Dracogyra subfusca ) are restricted to Longqi and one is found also in the nearby Duanqiao field less than 80 km away ( Gigantopelta aegis ; Zhou et al. 2018). Only in Longqi do the five peltospirids co-occur, and within the same assemblage type (the large aggregations of the giant peltospirids Chrysomallon squamiferum and Gigantopelta aegis ; Figure 1 (b)).

Although we did not attempt to examine the stomach contents of L. felix sp. nov. due to the scarcity of material, the lack of an enlarged oesophageal gland (seen by transparency) combined with the sizeable intestine and stomach suggests deposit feeding or grazing, like most peltospirids including other Lirapex species ( Fretter 1989; Warén and Bouchet 1989, 2001; Chen et al. 2017a). This is also in agreement with the intestine being packed with dark material in L. felix sp. nov., seen by transparency.

The fact that only two specimens of Lirapex felix sp. nov. were found during relatively focused collecting efforts at the ‘Tiamat’ chimney (DFF11) in the Longqi hydrothermal vent field ( Copley et al. 2016; Zhou et al. 2018) suggests that it may be a rare species – although sampling across the whole vent field remains patchy. Nevertheless, the relative abundance of Lirapex politus and Dracogyra subfusca has varied greatly between research cruises ( Chen et al. 2017a), indicative of either waxing and waning of abundance between years or sampling bias associated with fine-scale habitat preferences. It is also possible that L. felix sp. nov. is not truly rare but instead prefers a different microhabitat than L. politus , where sampling has not been done; perhaps it prefers more sedimented areas, like L. humatus ( Warén and Bouchet, 1989) . Future sampling efforts at Longqi and other Indian Ocean vents should pay careful attention to such microhabitats, in order to fully sample the biodiversity present.

Figures

Figure 1. (a) Map of southwestern Indian Ocean showing the Longqi hydrothermal vent field on the Southwest Indian Ridge; (b) ‘Tiamat’ chimney (DFF11) showing the typical peltospirid-snail-dominated aggregations alongside colonies of Bathymodiolus mussels and Neolepas stalked barnacles.