Pedicularia

Cairns, Stephen D. & Zibrowius, Helmut, 2013, Stylasteridae (Cnidaria, Hydrozoa, Filifera) from South Africa, Zootaxa 3691 (1), pp. 1-57 : 50-51

Pedicularia as a symbiont of South African stylasterids

The cypraeoid gastropod genus Pedicularia Swainson occurs worldwide from shallow to deep water. The highest latitude occurrences presently known are at about 48°N in the northeast Atlantic (Celtic Sea) and at about 37°S in both the southwest Pacific (Three Kings Islands, New Zealand) and the southwest Indian Ocean (Sapmer Seamount southeast of Madagascar). No Pedicularia seem to exist at higher northern and southern latitudes whereas stylasterids do occur up to Iceland, Norway, Alaska, and Antarctica. All Pedicularia are obligate symbionts on stylasterids (symbiont in its most neutral and etymologic sense of “living together”). The less than centimetric shells may be homochromous with the stylasterid host. Pedicularia feeds on its host coral, but how precisely is still unknown. Biology data are scarce. Liltved (1985a, 1985b, 1989) published interesting observations (juveniles still moving freely on the host before becoming sedentary) and speculations on feeding (consuming mucoid secretions of the host).

Adult Pedicularia always have their shell edge closely conforming to the configuration of the stylasterid branch at the place where they sit. This is a situation similar to that of a limpet shell adapting to the irregularities of the rock. Under the foot of the snail the branch surface is modified in a somewhat elongate area. It may have the aspect of a slightly prominent flat and smooth “sole”, or even bear distinct crests. In other cases the surface where the foot of the snail adheres is, as a whole, slightly depressed. Whether smooth or with crests, this is presumed to depend on the Pedicularia species involved. More distinct “soles” typically correspond to larger specimens (perhaps a matter of time to produce them). It is not intended here to discuss the precise structure of the modified area and how this modification is produced.

Thanks to the modified branch surface at the site where a Pedicularia had been sitting, information can be obtained on the occurrence of Pedicularia even after the snail and its host coral had become separated (e.g., by handling of the dredge contents), as well as from stylasterid bioclasts collected dead, separated from the sediment.

Given the diversified stylasterid fauna of South Africa and the moderate southern latitude, it is no surprise that Pedicularia occurs there. By latitude the South African occurrences fall a few degrees short with respect to the southernmost localities mentioned above for the southwest Indian Ocean and the southwest Pacific. Most data available are from the malacological literature, a supplement that has been obtained from traces left behind on stylasterid branches when the snail had not been preserved together with its host.

Pedicularia had first been mentioned from South Africa by Sowerby (1903), who mistakenly referred his sample to P. s i c u l a, the Mediterranean-northeast Atlantic species. Barnard (1963) added three more records (as P.

elegantissima ). All are (like Sowerby’s) from J.D.F. Gilchrist’s dredgings on the Pieter Faure. All specimens are preserved in the malacological collection of the South African Museum (A 5040, A 8931, A 8932, A 5070, A 8933; seen by HZ in 1980) and correspond to what currently is understood as P. elegantissima (not P. s i c ul a). Barnard (1963) mentioned that one sample had been taken from “ Stylaster or Allopora ” (i.e., the host species is not precisely known) whereas the others had been picked out of “bottom samples”. These records range along the coast from off Kwazulu-Natal south of Durban to off Western Cape Province approximately south of Mossel Bay, in the areas of Umkomaas (73m), Cape Morgan (86m, 173m), Hood Point (89m), and Cape St. Blaize (212m). The southwesternmost station is close to 35°S.

Liltved (1985a, 1985b, 1989) reported new records of P. elegantissima from the East London and the Nqabara Point areas (both Eastern Cape Province), mentioning as hosts Errina capensis , Errina sp., and Stylaster sp. He illustrated a trace (“scar”) of Pedicularia on a pink Stylaster (herein identified as Stylaster lonchitis ). Small pieces of two host species sent by Liltved to HZ in 1986 (now deposited at NMNH) are identified herein as the pink Errinopsis fenestrata (in 1989 mentioned as Errina sp.; off Nqabara Point, northern Eastern Cape Province, 32°27.2’S, 28°55.9’E, 250 m, 12.7.1984), and the pink Stylaster lonchitis (off Gonubie, Eastern Cape Province, 33°01.8’S, 28°04.4’E, 85 m, 17.7.1984).

Additional Pedicularia occurrences have been inferred during this study from what seem to be traces on Errina capensis from the Cape Morgan area, Eastern Cape Province (PF 13394, 123m; SAM H 1233) and on Conopora sola from Western Cape Province (UCTES AFR 950, 20.3.1949, 34°44’S, 21°18’E, 201m).

Considering experience from other stylasterid faunas (e.g., northeast Atlantic, New Caledonia) it is probable that Pedicularia occurs on even more species of South African Stylasteridae than those presently recognized as host corals.