Schizotricha vervoorti Peña Cantero, 1998

Peña Cantero, A. L. & Vervoort, W., 2005, Species of Schizotricha Allman, 1883 (Cnidaria: Hydrozoa: Halopterididae) from US Antarctic expeditions with the description of two new species, Journal of Natural History 39 (11), pp. 795-818 : 814-816

Schizotricha vervoorti Peña Cantero, 1998

Schizotricha vervoorti: Peña Cantero and Vervoort 1999, p 377 –379 (synonymy).

Material examined. 15/1345, one distal stem fragment ca 40 mm long, with gonothecae ( USNM 1025621); 691/27, a few stems up to 240 mm high, with male and female gonothecae ( USNM 1025622; RMNH-Coel. 30963; MNCN 2.03/338); 691/28, at least two stems up to 220 mm high, with gonothecae ( USNM 1025623; RMNH-Coel. 30964; MNCN 2.03/339); 691/30, one stem ca 55 mm high ( USNM 1025624); 721/704, one stem ca 250 mm high ( USNM 1025625).

Diagnosis. Colonies with branched stems. Main cauline tube with single hydrothecate internodes with three infrathecal nematothecae; cauline apophyses with two nematothecae. Hydrocladia up to fourth order. Hydrocladia regularly divided into hydrothecate internodes. Unforked hydrocladial internodes with two infrathecal nematothecae at same level (occasionally only one in the most distal internodes). Hydrotheca deep. Forked hydrocladial internodes with two to four infrathecal nematothecae; hydrocladial apophyses with two or three nematothecae.

Ecology and distribution. Schizotricha vervoorti is a eurybathic species. It has previously been found at depths from 50 to 149 m (Peña Cantero 1998). The material discussed here comes from depths between 91 and 1152 m, considerably extending its bathymetric range. It is used as a substratum by colonies of other hydroids ( Lafoea sp., Oswaldella vervoorti Peña Cantero and García Carrascosa 1998 , Symplectoscyphus sp.). Colonies with gonothecae have been found in January (Peña Cantero 1998) and in February and November (present material).

Schizotricha vervoorti is known mainly from West Antarctica, having been reported off Peter I Island in the Bellingshausen Sea ( Blanco and Bellusci de Miralles 1972), off Low Island ( Blanco 1984) and King George Island (Peña Cantero 1998), both in the South Shetland Islands area, and off Coronation Island, South Orkney Islands (Peña Cantero 1998). We found it both in the South Shetland Islands area (off Low Island, King George Island and Deception Island) and at 54 u 509–54 u 519S, 129 u 489–129 u 469W (South Pacific Ocean), far from the previously known area of distribution.

Bathymetrical and biogeographical remarks

The genus Schizotricha consists of 17 known species, four of which are found far from Antarctic or sub-Antarctic waters. These species are S. dichotoma and S. profunda , which seem to be restricted to deep waters of the tropical West Atlantic, S. frutescens , found in the north-east Atlantic and living in shelf and deep waters, and S. variabilis , a boreal Atlantic species also dwelling on deep bottoms.

The remaining 13 species are found either in Antarctic and sub-Antartic waters or exclusively in Antarctic waters ( Figure 3 ). Only two of those species, S. multifurcata and S. unifurcata , are found in sub-Antarctic waters. Of those two the first should be considered a sub-Antarctic species found in the Antarctic region only at its limits (at the South Sandwich Islands and off Bouvet Island), but never in high Antarctica. Conversely, S. unifurcata is widely distributed in Antarctic waters and reaches sub-Antarctic waters only in the Kerguélen area, thus having an Antarctic-Kerguélen distribution.

The remaining 11 species are endemic to the Antarctic region. Of those, four ( S. anderssoni , S. glacialis , S. nana , and S. turqueti ) are circum-Antarctic species, i.e. they are found in both East and West Antarctica. Of the remaining seven species, S. trinematotheca sp. nov. is from present evidence endemic to East Antarctica, whereas the remainder are endemic to West Antarctica ( S. crassa , S. falcata , S. heteromera sp. nov., S. jaederholmi , S. southgeorgiae , and S. vervoorti ). Two species ( S. jaederholmi and S. southgeorgiae ) are endemic to South Georgia, the marine fauna of which has many peculiarities, being considered as a district of the Antarctic region by several authors. It seems to be closer to the Patagonian area in its shallow-water fauna, but closer to the Antarctic region as far as the deep-water fauna is considered.

Table II shows the bathymetrical distribution of the known species of Schizotricha . Most of the species have a wide bathymetric range. However, of the 13 known species inhabiting Antarctic waters, only S. turqueti must be considered a eurybathic species, extending from the shallowest levels of the continental shelf to bathyal depths. Most species are shelf species, i.e. species inhabiting bottoms of the continental shelf which in the Antarctic has the shelf-break two to four times deeper than in other oceanic regions. These shelf species are S. crassa , S. falcata , S. heteromera sp. nov., S. jaederholmi , and S. trinematotheca sp. nov. They are absent from the shallowest levels of the continental shelf, impacted by different manifestations of ice. Another group of species is that constituted by species extending beyond the limit of the continental shelf-break, reaching bathyal depths ( S. anderssoni , S. multifurcata , S. nana , S. unifurcata , and S. vervoorti ). Finally, S. southgeorgiae can be considered, at least for the present, as a deep-water species.

Figures

Figure 3. Geographical distribution of the known Antarctic and sub-Antarctic species of Schizotricha Allman 1883. (a) S. anderssoni; (b) S. crassa; (c) S. falcata; (d) S. glacialis; (e) S. heteromera sp. nov.; (f) S. jaederholmi; (g) S. multifurcata; (h) S. nana; (i) S. southgeorgiae; (j) S. trinematotheca sp. nov.; (k) S. turqueti; (l) S. unifurcata; (m) S. vervoorti.