SCI. MAR., 61 (Supl. 2): 5-14 SCIENTIA MARINA 1997 ECOLOGY OF MARINE MOLLUSCS. J.D. ROS and A. GUERRA (eds.) Biology and description of Antisabia juliae sp. nov., new Hipponicid gastropod commensal on Turbo spp. in Laing Island (Papua New Guinea)* MATHIEU POULICEK1, JEAN-CLAUDE BUSSERS1 and PIERRE VANDEWALLE2 1Animal Ecology Laboratory and 2Functional Morphology Laboratory, Zoological Institute, Liège University. 22, Quai Van Beneden, B-4020 Liège. Belgium. SUMMARY: The gastropod family Hipponicidae comprises widely distributed but poorly known sedentary species. On the beach-rock of the coral reefs of Laing Island (Papua New Guinea) live rich populations of several gastropod Turbo species of which many specimens have attached to their shell a hipponicid gastropod attributed to a new species, Antisabia juliae. This new species, described in this paper, appears to have adapted its mode of life on live turbinids in several ways result- ing in morphological changes (thin basal plate loosely adherent to the supporting shell, functional eyes, very long snout, functional radula, small osphradium) and ethological changes (foraging behaviour: it appears to feed on the epiphytic com- munity growing on the host, in the vicinity of the “host” shell). Except for these characteristics, the mode of life appears quite similar to that of other hipponicid species with few big females surrounded by several much smaller males. Development occurs within the egg mass inside the female shell and a few young snails escape at the crawling stage. Key words: Mollusca, Gastropoda, ecology, Hipponicidae, Papua New Guinea, Indopacific. RESUMEN: BIOLOGÍA Y DESCRIPCIÓN DE ANTISABIA JULIAE SP. NOV., UN NUEVO GASTERÓPODO HIPONÍCIDO COMENSAL DE TURBO SPP. EN LA ISLA LAING (PAPÚA NUEVA GUINEA). La familia Hiponícidos comprende especies sedentarias ampliamente distri- buidas pero poco conocidas. En las costas rocosas de los arrecifes coralinos de la isla Laing (Papúa Nueva Guinea) viven abundantes poblaciones de varias especies de Turbo, muchos de cuyos ejemplares portan un gasterópodo hiponícido atri- buido a una nueva especie, Antisabia juliae, que se describe en este artículo. Esta especie parece haberse adaptado de varias maneras a vivir sobre los turbínidos vivos, lo que ha conducido a cambios morfológicos (placa basal delgada y ligeramen- te adherente a la concha de sostén, ojos funcionales, hocico muy largo, rádula funcional, osfradio pequeño) y etológicos (comportamiento alimentario: parece que se alimenta de la comunidad epifítica que crece sobre el patrón, en la inmediatez de la concha del “patrón”). Excepto por estas características, el modo de vida parece muy semejante al de otras especies de hiponícidos, con unas pocas hembras grandes rodeadas de varios machos mucho menores. El desarrollo tiene lugar en el interior de la masa de huevos, dentro de la concha de la hembra, y unos pocos caracoles juveniles escapan en el estadio de reptación. Palabras clave: Moluscos, Gasterópodos, ecología, Hiponícidos, Papua-Nueva Guinea, Indopacífico. *Received October 1995. Accepted September 1996. NEW HIPPONICID SPECIES IN PAPUA NEW GUINEA 5 INTRODUCTION tilled water at 4°C for 1 hour, washed in distilled water, dehydrated through graded ethanol series and Hipponicidae are a group of widely distributed dried by sublimation at 10°C under low pressure but poorly known sedentary gastropods. Except for after inclusion in Peldri® fluorocarbon resin. The a few older papers (i.e., Quoy and Gaimard, 1835) material was glued onto Al stubs with Tempfix® there is only a small number of articles dealing with conductive resin, Au-Pd sputtered (15 nm) (cold the detailed morphology and life habits of represen- diode Balzers sputtering device) and examined with tatives of this family (for a review, see Knudsen, a Jeol JSM-840/A scanning microscope. 1991, 1993). Due to the lack of knowledge about their anatomy, a considerable uncertainty prevails regarding the delimitation of the Indopacific genera DESCRIPTION and species (Knudsen, 1993), particularly in Papua New Guinea. Antisabia juliae sp. nov. Laing Island (4° 10’ 30” S, 144° 52’ 47” E) lies Class Gastropoda in the western part of the Bismarck Sea, in the mid- Superfamily Hipponicacea Troschel, 1861 dle of Hansa Bay (Madang Province, northern coast Family Hipponicidae Troschel, 1861 of Papua New Guinea). This small island is almost completely surrounded by live coral formations and Material examined: Over 300 specimens were has an eroded coral plateau (beach rock), 75 meters observed of which most were returned live to the wide, on three sides: east, north and south. On this beach. Approximately 50 specimens were preserved plateau live rich populations of Turbo setosus for dissection and SEM examination. Gmelin, 1791, T. crassus Wood, 1829, T. brunneus (Röding, 1798) and T. sparverius Gmelin, 1791, of Holotype: A female specimen, collected in May which many specimens wear a hipponicid gastropod 1995 cemented to a shell of Turbo setosus Gmelin, attributed to the genus Antisabia that we consider as 1791 on the beach rock at Laing Island (Papua New a new species. This hipponicid was almost found Guinea); 4 mm length and 3 mm width; glutarade- only on the shells of these four species. hyde/OsO4 fixed and ethanol preserved. Deposited in the collections of the Royal Institute of Natural Sciences of Belgium in Brussels (IRSNB) under n° MATERIAL AND METHODS I.G. 28.371A During three missions on Laing Island in Holotype diagnosis: The shell is solid, patelliform in October-November 1990, 1992 and May-June 1995, general shape, with a pyriform aperture. In lateral we were able to collect samples for SEM observa- view, the anterior edge is convex and the apex is tions and to describe the gross morphology, the spa- located quite closer to the posterior margin. tial and specific distribution of this new Antisabia Sculpture is constituted of 6 thick axial undulations species (approx. 300 specimens were observed, becoming deeper close to the aperture, crossing most of which were returned live to the collecting irregular growth marks. The shell is whitish pink site according to the wishes of the Papua New under a thin amber periostracum, partly covered by Guinea authorities). calcareous algae and other epiphytes. The interior is The material was sampled at low tide on the glossy white. The protoconch (not well conserved) beach rock. Supporting shells of Turbo spp. were is rissoid in shape (Fig. 3B), with 2.5 whorls, sized and identified on site and the number, position smooth (except superficial granulations due to the on the host and sizes of the hipponicid shells record- shell fabric) and disposed at right angle of the teleo- ed with a caliper square to the nearest 0.1 mm. conch. Its sizes are as follow: 400 µm in length, 270 Results were computed and interpreted through µm in diameter, nucleus 120 µm in diameter. The Systat® statistical software package. basal plate is partly conserved: it is a thin white cal- Some samples were either ethanol preserved for careous layer on the ventral side of the metapodium, dissection and radula extraction or glutaraldehyde smaller in diameter than the aperture of the shell. fixed for scanning electron microscopy (SEM). When observed alive, the head showed a rela- Later, the samples for SEM were washed in 0.2 µm tively big muscular and very extensible snout (sev- filtered seawater and postfixed in 0.5 % OsO4 in dis- eral mm out of the shell; Figs. 1D, 4), the distal ends 6 M. POULICEK et al. FIG. 1 – Antisabia juliae sp. nov.; A, shell, dorsal view of a female specimen (paratype; scale bar, 250 µm); B, shell, internal view of a female specimen (paratype; scale bar, 250 µm); C, fingerprint on the surface of a Turbo shell (scale bar, 250 µm); D, anterior cephalic region (scale bar, 100 µm) c, ctenidium (gill); f, anterior part of the propodium; l, lateral lobe of the snout; o, osphradium; p, mantle edge; t, tentacles. NEW HIPPONICID SPECIES IN PAPUA NEW GUINEA 7 FIG. 2 – Antisabia juliae sp. nov. A, General view of the radula of a male specimen (scale bar, 50 µm). B, Detail of the anterior part (6 first rows) of the radula of a female specimen (scale bar, 10 µm). C, General view of a young snail recently hatched from the egg capsule. (scale bar, 10 µm). 8 M. POULICEK et al. of which bear a pair of blunt lateral mobile lobes (l, Other morphological features and variations Figs. 1D, 4). Tentacles are conical, long and thin within the population when extended, of the same length or slightly longer than the snout (t, Figs. 1D, 4), with small brown The teleoconch is variable in shape and thick- ventrolateral eyes at the base. The general colour is ness: generally solid, patelliform to conical, it is whitish with regular dark brown to black marks on more or less elevated according to the size and the the distal part of the tentacles (one third of their localization of the specimen on the “carrier” mol- length) and on the edges and lateral parts of the lusk shell (Figs. 1A, B): specimens located on the snout except the distal lobes (Fig. 4). external part of the peristomium are generally larger than specimens on the columellar region of the host Allotype: A male specimen, collected in May 1995 shell (shallower ovoid patelliform shells). The same cemented to the same shell of Turbo setosus Gmelin, observations were made on males and females. The 1791 as the holotype, same locality; 2 mm length biggest female specimens observed reach 14 mm in and 1.5 mm width; ethanol preserved (IRSNB col- diameter, the biggest males less than 4 mm. lections N° I.G. 28.371B). Sculpture is present in more than 85% of specimens: it is constituted of 2 to 12 axial undulations becom- Allotype diagnosis: The shell (teleoconch) is very ing deeper closest to the aperture.