A new species of Arene ( Vetigastropoda , Areneidae ) from Canopus Bank , off NE Brazil

Arene lychee sp. nov. is described from Canopus Bank, a seamount located ~190 km off Fortaleza, Ceará, NE Brazil (02°14’25”S, 38°22’50”W), based on shell morphology. The species is characterized by a large, trochiform shell; color ranging from intense reddish to white (darker on spiral cords, lighter at base) with a yellow apex; sculpture of 3-8 wide spiral cords with large scale-like spines; cords separated by deep interspaces with similar width, and interspaces sculptured by closely-packed, thin axial growth lines. Key-Words. Angarioidea; Biodiversity; Gastropoda.


INTRODUCTION
The family Areneidae has been recently erected to remedy nomenclatural issues and to reflect recent molecular phylogenetic hypotheses of relationships within the Vetigastropoda (Williams et al., 2008;McLean, 2012).As it is currently understood, the family exclusively accommodates species previously belonging to Liotiidae Gray, 1850.The Areneidae are characterized by colorful shells (as opposed to the whitish Liotiidae) with dominant spiral sculpture, a tangential aperture with denticles and a lip preceded by a short phase of whorl expansion (McLean, 2012).The group currently includes the African genus Cinysca Kilburn, 1970 and the Atlantic-Pacific Arene Adams & Adams, 1854, which is represented in Brazil by at least nine species (Rios, 2009).
Canopus Bank is a seamount located ~190 km off Ceará state, NE Brazil (02°14'25"S, 38°22'50"W, ca.50-600 m depth), which harbors an impressive diversity of invertebrate species.The local substrate is mostly biogenic, presenting relatively large, calcareous particles consisting of mixed animal remains such as fragmentary hard corals, crustaceans, echinoderms, and mollusk shells.Studies on sediment samples from Canopus collected in 2005 have revealed a remarkable number of new taxa.This includes 17 new gastropod species belonging to 12 different families, most of which were described based on empty shells (e.g., Abbate & Cavallari, 2013;Simone & Cunha, 2014;Fernandes et al., 2015).In the present study, we formally describe a new species of Arene from Canopus stemming from a broader review of the local vetigastropod fauna (Cavallari & Simone, unpublished data).

SYSTEMATICS
Distribution: Known only from type locality.

Etymology:
The specific name, a noun in apposition, is derived from the English common name of the Asian soapberry tree Litchi chinensis (Sapindaceae).The fruits of L. chinensis bear a strong resemblance to the shell of the described species, having similar coloration, globose outline, and an overall rough, "spiky" aspect.

DISCUSSION
Compared to Western Atlantic congeners, Arene lychee sp.nov. is most similar to Arene briareus (Dall, 1881) from the Caribbean, in both color range and size, and seems to be related to it.Though the syntype specimen of Arene briareus var.perforata (Dall, 1889) (= Arene briareus) depicted herein (Fig. 2A-D) apparently has its color altered or damaged in some way, as it seems to be only faintly reddish, it certainly has a slightly yellowish apex, thus presenting a color pattern that is quite similar to A. lychee sp.nov.Even so, the new species differs by having one less spiral cord per whorl, bearing much larger, coarser, and more pronounced nodules/spines, and a proportionally taller, trochoid shell with a straighter profile.Moreover, it can be distinguished from nearly every other congener in Brazilian waters by its size alone, being at least 25% larger than the remaining species.The sole exception is Arene flexispina Leal & Coelho, 1985, recently illustrated by Pimenta et al. (2014).It can be distinguished from the latter by having a predominantly red shell with a yellow apex, as opposed to an overall reddish-brown shell with lighter colored spiral cords and spines; more numerous nodules/spines; by being proportionally shorter and wider, and by having a less convex and more coarsely sculptured base.
The present discovery is based on relatively scarce samples but is nevertheless a testimony to the significance of studying seamount environments.Seamounts are known to harbor a diverse and often endemic biota (Stocks, 2004), which often suffers the effects of intense fishing pressure (Morato et al., 2004(Morato et al., , 2006)).In our understanding, Canopus is no exception to this fact, which is made even worse when a large number of new species that have been revealed from that location is considered.Since the fauna of Canopus might be at risk due to intense human activities in that area (Melo-Filho & Melo, 2006), it is vital that the local biodiversity is thoroughly investigated so that proper legal protection can be provided.