Abstract
Morphological (shell) and molecular examination of a large suite of specimens of pleurotomariids from around New Caledonia and the Coral Sea reveals the existence of four species in the complex of Perotrochus caledonicus: Perotrochus deforgesi Métivier, 1990 and P. pseudogranulosus sp. nov. live allopatrically on the plateaus and guyots of the Coral Sea; Perotrochus caledonicus Bouchet & Métivier, 1982 and Perotrochus wareni sp. nov. live sympatrically - but essentially not syntopically - on the slopes of New Caledonia, Norfolk Ridge and the Loyalty Ridge. All species live in the 300–500 m interval, and together form a significant component of the mollusc fauna living on hard bottoms in the SW Pacific, with individual dredge hauls containing up to 25 specimens of Perotrochus.
Highlights
Perotrochus caledonicus Bouchet & Métivier, 1982 and P. tangaroanus Bouchet & Métivier, 1982 were the first pleurotomariids described from the South Pacific, from New Caledonia and from the Lau Ridge between New Zealand and Fiji (Bouchet & Métivier 1982), respectively
With the exception of some juveniles, we could separate all the specimens of the Perotrochus caledonicus complex into four different morphotypes (Table 2): one group presents shell characters consistent with the name-bearing holotype of P. caledonicus as described by Bouchet & Métivier (1982); the second group corresponds to the “rugose” or “pustulose” form, and is described below as P. wareni sp. nov.; a third group, with a geographically limited distribution within the Coral Sea, shows a microgranular
One of the distinctive shell characters separating Perotrochus wareni sp. nov. from P. caledonicus is the well-marked beading on the teleoconch spiral cords, visible on the earlier whorls, giving it at first glance its typical pustulose or granular appearance
Summary
Perotrochus caledonicus Bouchet & Métivier, 1982 and P. tangaroanus Bouchet & Métivier, 1982 were the first pleurotomariids described from the South Pacific, from New Caledonia and from the Lau Ridge between New Zealand and Fiji (Bouchet & Métivier 1982), respectively. Additional species have been documented from New Caledonia Many populations at first sight referable to Perotrochus caledonicus were sampled around New Caledonia and in the Coral Sea. The type material of P. caledonicus from off southern New Caledonia consists of specimens with a macroscopically non-pustulose shell, with rather smooth to weakly beaded spiral cords. It appeared that a more granulose or pustulose morph occurred around New Caledonia. As such material appeared very similar in terms of size, color and general profile, it was considered to represent just a form of P. caledonicus. New material from New Caledonia and the Coral Sea has allowed revisiting this issue, using an integrative taxonomic approach combining DNA sequencing and shell characters of both juveniles and adults. Perotrochus deforgesi was found to be molecularly closely related to this complex - which was not suspected from shell characters alone - and in this paper we will designate these small Perotrochus from the SW Pacific together as the “Perotrochus caledonicus complex”
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