“Tedania charcoti, Topsent.
T. charcoti, Topsent, 1908, p. 3o, pl. i, fig. 3, pl. iii, fig. 3, pl. v, fig. 6; 1913, p. 630, pl. v, figs. 3-7; nec Topsent, 1917.
Occurrence. St. 39: South Georgia, 179-235 m.; St. 140: South Georgia, 122-136 m.; St. 145: South Georgia, 26-35 m.; St. 146: South Georgia, 728 m.; St. 148: South Georgia, 132-148 m.; St. 152: South Georgia, 245 m.; St. 158: South Georgia, 401-411 m.; St. 16o: Shag Rocks, 177 m.; St. WS 27: South Georgia, 106-109 m.; St. WS 42: South Georgia, 198 m.
The nineteen specimens range from a few centimetres in longest diameter to nearly 20 cm. From the structure of the skeleton it is possible to divide this group into two smaller groups; the first, of five specimens, is characterized by a dense skeleton and thick spicules (styli 0.36-0.49 by 0.02-0.031 mm.), with the dermal skeleton composed of a very dense palisade of stout tornota (measuring 0.32-0.39 by 0.014-0.021 mm.). The second group, of eleven specimens, is characterized by a loose skeleton composed of few spicules, mainly slender (styli 0.35-0.52 by 0.011-0.021 mm.), with a diffuse dermal skeleton of slender tornota (measuring 0.24-0.34 by 0.007-0.009 mm.). There are in addition three specimens with skeletons somewhat intermediate in character between those of these two groups. In external form the specimens of each group show the same variations; from massive with digitate or flabellate processes, to massive, with the surface raised into low rounded prominences, and, in rare cases, sub-clathrate. Further, all the five specimens of the first group are from St. WS.27 (South Georgia, 106.9 m. depth) and four of the second group are from the same locality. The remaining specimens of group 2 are also from South Georgia, from depths varying between 132 and 411 m. The similarity in external form between the members of the two groups, the presence of intermediates as regards skeleton structure, and the similarity between the two groups in spiculation, except for size of spicules and numbers present, suggest that there is no taxonomic significance in this sub-division. Similarly, since all the specimens from the first, and a third of the specimens from the second group are from the same station, an ecological significance is hardly a possibility. It is, however, remarkable that seven specimens of group 2, out of a total of eleven, contain embryos while none of the specimens of group I has any. Possibly the looseness of the skeleton may have something to do with the development of the embryos, and we may therefore accept all nineteen as conspecific .
Several of the specimens of this group are almost identical with the co-type of Tedania charcoti, Topsent (1908, pl. iii, fig. 3). One or two of them approximate fairly closely to the holotype (id., loc. cit., pl. i, fig. 3), and there are several which differ slightly from both. There can, however, be little doubt that all belong to T. charcoti. Here, however, another point arises: Topsent (1908) records only two sorts of onychaeta in his specimens, but in the present specimens exceptions are found to this. In the types of this species, these spicules measure 0.09-0.12 and 0.25-0.265 mm. long. In eleven of the present specimens three sizes of onychaeta were found, the smallest measuring from 0.05 to 0.105 mm., with an average of 0.08 mm., the largest, 0.24-0.32 mm., with an average of 0.29 mm. Intermediate sizes were found, admittedly rare, varying from 0.105 to 0.24 mm., with an average of 0.163 mm. In six specimens, no intermediates were found, but in two specimens four separate categories appeared to be present. Moreover, in some specimens the onychaeta were rare, in others commonly present, and in rare cases so abundant that they formed the bulk of the skeleton. It does not seem possible therefore to use the onychaeta for the determination of species.
DISTRIBUTION. Graham Land; Burdwood Bank.”
(Burton, 1932: 307-308)
