Vercoia interrupta Kim & Fujita, 2004

Anker, Arthur, 2010, A Second Finding Of Vercoia Interrupta Kim & Fujita, 2004 (Crustacea, Decapoda, Crangonidae), A Remarkable Shrimp Imitating Dead Snail Shells, Raffles Bulletin of Zoology 58 (1), pp. 27-30 : 29

Vercoia interrupta Kim & Fujita, 2004

( Fig. 1 )

Material examined. – 1 ovigerous female (CL 6.5 mm), OUMNH 2009-18 - 0046 , The Philippines, Bohol, Balicasag Island near Panglao , 9°31'05.07"N 123°40'52.25"E, early night dive, depth 3–5 m, coll. G. Poppe, 26 Jan.2009 [photographed] .

Additional specimen observed in situ, not collected. – 1 ovigerous female, The Philippines, Cebu, Ponson Island off Pilar , 10°43'54.75"N 124°31'00.43'E, night dive, rubble, depth 20 m, 12 Oct. 2008 [photographed] .

Description. – Kim & Fujita (2004) provided an excellent description of V. interrupta , with numerous illustrations of the adult morphology, as well as the first to fourth zoea.

Colour pattern. – Carapace and abdomen mostly opaque whitish with some greyish areas; walking legs dark purple; antennular flagella with blackish spot proximally, pale yellow distally ( Fig. 1 ).

Distribution. – Presently known only from the type locality in Okinawa, Ryukyu Islands (Kim & Fujita 2004) and Balicasag (Bohol) and Ponson (Cebu) in the central Philippines (present study). The present record of V. interrupta from the Philippines extends its distribution range southwards by around 1,800 km.

Habitat. – Coral rubble with encrusting algae and sponges ( Fig. 1C ), at depths of 3–8.5 m, possibly down to 20 m (Kim & Fujita 2004; present study).

Biology. – Vercoia interrupta uses a rather remarkable camouflage strategy. As in other species of Vercoia and some other Crangonidae , the body of V. interrupta is compact and heavily sculptured (“bumpy”), being covered with numerous tubercles and several ridges ( Fig. 1A, B ; see also Kim & Fujita 2004), and has a uniform “dirty whitish” colour, the dark purple walking legs being mostly invisible in dorsal view ( Fig. 1B, G ). Kim & Fujita (2004) noted that V. interrupta resembles a “small piece of rubble”, which would make it cryptic on a rubble bottom. However, by stretching the abdomen completely, with its tail fan almost pointing posteriorly ( Fig. 1D–G ), the shrimp also remarkably resembles a dead and encrusted cerithiid snail shell, more specifically that of Cerithium rostratum G. B. Sowerby II, 1855 , which is common in the area (G. Poppe, pers. comm.). Even when moving V. interrupta resembles a cerithiid shell occupied by a hermit crab more than a shrimp, and would probably be ignored by most visually hunting predators. Night activity (all individuals of V. interrupta were found at night) may further increase the survival chances of this peculiar shrimp.

Remarks. – Behavioural observations and photographs of Vercoia spp. are extremely rare. To the author’s best knowledge, the only other published photograph of Vercoia is that of V. gibbosa ( Gowlett-Holmes, 2008) , which also seem to mimic shell fragments. All species of Vercoia may be imitators of dead shells or at least shell fragments, based on their morphological similarity with V. interrupta , although the latter species seems to do so most convincingly.

Figures

Fig. 1. Vercoia interrupta Kim & Fujita, 2004: A–D, ovigerous female from Balicasag Island, Panglao, Bohol, Philippines; E–G, ovigerous female from Ponson Island, Pilar, Cebu, Philippines. A, recently preserved specimen, lateral view; B, same, dorsal view; C, living shrimp in situ, showing microhabitat; D, same, close-up; E, living shrimp (different individual) in situ, lateral view; F, same, dorsolateral view; G, same, anterodorsal view. (C–G, photographs by Guido Poppe).