Cordagalma tottoni Margulis, 1993

P. R. Pugh, 2016, A synopsis of the Family Cordagalmatidae fam. nov. (Cnidaria, Siphonophora, Physonectae), Zootaxa 4095 (1), pp. 1-64 : 16-17

Cordagalma tottoni Margulis, 1993 .

Diagnosis. Small, typically heart-shaped nectophores. Pedicular canal, on reaching nectosac, gives rise to only upper and lower radial canals. Lateral canals arise from the upper canal.

Remarks. The original description of Cordagalma tottoni was based on fragments of a single specimen collected, using a Juday net in the 100–0m depth zone, by the Research Vessel Vozrozhedenia on 18th December 1986 at 35°S 139°W, in the middle of the South Pacific Ocean. The material was said to consist of a stem, with pneumatophore and various buds, three nectophores, two gastrozooids, and several siphosomal fragments. The type specimen has been re-examined by the present author.

A problem with Margulis' (1993) description of the nectophores is that she had orientated them upside-down, such that she considered the conical lower part of the nectophore to be anterior. This apart, the only real distinguishing feature of the nectophores, the largest of which measured 3.5 mm in height and 2.5 mm in width, was that the pedicular canal, on reaching the nectosac, gave rise to only the upper and lower radial canals ( Figure 12 ). The lateral radial canals then arose from the upper (ventral according to Margulis) canal. This, with some difficulty, was confirmed by the present author and, thus, is in contrast to the arrangement in all other Cordagalma species herein described where all the radial canals arise together from the pedicular canal.

It is far from certain that the siphosomal zooids described by Margulis (1993) actually belong to the same specimen as the detached nectophores. Some of the palpons were said to have palpacles ( Figure 12 ) while others did not. This suggests their presence and subsequent loss, which would be in marked contrast to the arrangement in other Cordagalma species, but is in accord with that found for Cardianecta parchelion gen. nov., sp. nov. described below. However, the re-examination showed that the palpons, which were attached at their bases, appeared not to possess palpacles. The loose gastrozooids had the proximal part of the tentacles attached, which bore, presumably, young tentilla with long pedicles and oval cnidobands, with a beak-shaped tip. There was said to be a single row of larger nematocysts on either side of the cnidoband, enclosing numerous smaller ones. No further details could be added. These are quite unlike the tentilla of C. ordinatum that Margulis (1993, Figure 2 E) figured but, again, those of Cardianecta parchelion gen. nov., sp. nov. are very different. The bracts of C. tottoni also were markedly different in having a transverse ridge demarcating a triangular distal facet on the upper side, and with a bracteal canal that was said to end below the middle of a strip of nematocysts running proximally from the distal tip of the bract. Finally, Margulis described the gonophores as being immature but, on re-examination, the sex of some could be determined and they all appeared to be female. It is, however, doubtful that this observation has any significance.

Thus, until a complete specimen of Cordagalma tottoni is collected it is impossible to know if the siphosomal zooids described by Margulis (1993) actually belong with the nectophores. Nonetheless, the fact, since confirmed by the present author, that the lateral radial canals on the nectosac arise from the upper canal is a distinguishing feature setting this species apart from all other Cordagalma species.

Distribution. Known only from a single specimen collected in superficial waters in the central South Pacific Ocean (c, 35°S 139°W).

Etymology. Named for Arthur Knyvett Totton whose Synopsis of the Siphonophora , published in 1965, remains the most important work on siphonophores published to date.

Figures

FIGURE 2. Anthemodes ordinata Haeckel, 1888. Reproduced from Haeckel (1888, Pl. XV).

FIGURE 12. Cordagalma tottoni Margulis 1993. A. & B. Axial and lateral view, respectively, of a nectophore, scale bar 1 mm; C. a tentillum (proximal at top), scale bar 0.1 mm; D. bract & E. palpon (proximal at bottom), scale bars 1 mm. Redrawn from Margulis (1993).