Tulpa revelata, Cantero, 2025

Tulpa revelata sp. nov.

( Figs 7–8 View FIGURE 7 View FIGURE 8 )

Tulpa tulipifera View in CoL — Vervoort, 1972: 90, fig. 25e; El Beshbeeshy, 2011: 85–88, fig. 25; Soto Àngel & Peña Cantero, 2015: 1000, fig. 9i–j.

Tulpa diverticulata View in CoL — Millard, 1977: 20, fig. 5G–H.

Material examined. ATLANTIS 2008 Stn LO 01 , several interwoven colonies with stolonal hydrothecae and stems up to 50 mm high, also growing on and surrounding stems of Symplectoscyphus sp. , with male and female gonothecae (Holotype, MNCN 2.03/692 , colony fragment 40 mm long, with three complete hydrothecae and five female gonothecae; Paratype, MNCN 2.03/693 , colony fragment 14 mm long, with two hydrothecae and one male gonotheca); ANTARKTIS XIX/5 Stn 153 , four stem fragments up to 40 mm long, with one complete hydrotheca and the basal part of another, with male and female gonothecae ( DZUV) .

Description. Colonies consisting of stolonal hydrothecae and erect, monosiphonic, occasionally branched stems up to 50 mm high. Stems with up to 12 hydrothecae on very short pedicels, alternately arranged in two planes forming an acute angle. Strong tendency to unilateral arrangement. No distal hydrotheca observed. Branching irregular. Branches with hydrothecae arranged as in stems.

Hydrothecae tubular, almost cylindrical, with slightly bulbous basal part ( Fig. 7a–b View FIGURE 7 ): diameter markedly increasing at annular thickening, then slightly decreasing distally, and finally widening slightly at most distal part, reaching maximum diameter at aperture. Rim of hydrothecal aperture uneven (with 12 to 16 well-marked blunt cusps) ( Figs 7a–c View FIGURE 7 , 8a–b View FIGURE 8 ), slightly everted ( Fig. 8f–g View FIGURE 8 ), and markedly sinuous ( Fig. 8e–g View FIGURE 8 ). Sinuosity creating alternate sequence of crests and troughs outside and inside hydrotheca ( Fig. 8e–g View FIGURE 8 ); inside crests more acute ( Fig. 8f View FIGURE 8 ). Sinuosity fading downwards. Rim external troughs corresponding to cusps; outside crests to embayments ( Fig. 8e–g View FIGURE 8 ). Cusps directed upwards, embayments outwards ( Figs 7c View FIGURE 7 , 8a–d View FIGURE 8 ), resulting in a series of longitudinal, little-marked ridges running downwards and delimiting barely concave external facets. Rim of cusps and embayments markedly bent outwards for a short extent ( Fig. 8f–g View FIGURE 8 ). Hydrothecal perisarc smooth.

Gonothecae arising from hydrorhizal stolons, or from stems between hydrothecae, on very short pedicels. Putative female gonothecae ( Fig. 7d View FIGURE 7 ) oval-shaped, distally projecting into a long neck bearing a circular distal aperture. Putative male gonothecae ( Fig. 7e View FIGURE 7 ) oval-shaped, distally projecting into a very short neck with distal circular aperture. Gonothecal perisarc smooth or partially striated.

Remarks. Stems might have up to 21 hydrothecae when adding those on their branches.

The sinuosity is well defined at the hydrothecal rim, but rapidly fades towards the base. As a result, the facets become almost indistinguishable in the basal part of the hydrotheca, although a polygonal structure remains noticeable ( Fig. 8e View FIGURE 8 ).

In this species, the presence of cusps is a real feature and not an optical illusion as in T. diverticulata . The cusps are also visible from above, with the cusps and embayments clearly situated at different levels ( Fig. 8f View FIGURE 8 ). The rim of the embayments, corresponding to the external crests, is clearly lower than the rim of the cusps, corresponding to the external troughs ( Figs 7c View FIGURE 7 , 8c–g View FIGURE 8 ).

The sex assignation of the gonothecae is based on the fact that, in the case of Tulpa peculiaris sp. nov., the undoubtedly female gonothecae have significantly longer necks.

The revision of the material from ANTARKTIS XIX/5, previously studied by Soto Àngel & Peña Cantero (2015, as T. tulipifera ), who illustrated a hydrotheca and a female gonotheca, has shown that it is conspecific with the holotype of Tulpa revelata sp. nov. They share both the shape and size of the hydrothecae and gonothecae (see Fig. 9I–J View FIGURE 9 in Soto Àngel & Peña Cantero 2015), as well as the size of the nematocysts. The study of their material also revealed the presence of previously overlooked male gonothecae, which are similar to those present in the holotype.

As mentioned above, the specimens assigned to T. tulipifera by Vervoort (1972) and El Beshbeeshy (2011) do not belong to Allman’s species. Instead, I believe they are conspecific with Tulpa revelata sp. nov. The shape of the hydrotheca is remarkably similar, barely widening at the aperture and with well-marked cusps. According to Vervoort (1972) the incisions between the cusps are curved outwards, while the rounded cusps are bent inwards, which is also present in Tulpa revelata sp. nov. In addition, the gonothecae illustrated by El Beshbeeshy are similar in both shape and size to those of Tulpa revelata sp. nov.

As noted previously, Millard’s (1977) material of T. diverticulata does not belong to Totton’s species (see discussion of that species). In my opinion, it is conspecific with Tulpa revelata sp. nov., as they agree perfectly in both the shape and size of the hydrothecae and gonothecae.

Jäderholm’s (1905) material of T. tulipifera from Burdwood Bank, re-examined and described by Nutting (1915), probably does not belong to Allman’s species. Instead, it may be conspecific with Tulpa revelata sp. nov.

Finally, as noted above, part of the material assigned to T. diverticulata by Ralph (1959), particularly that from Bligh Sound, appears to belong to a different species. It has more robust hydrothecae without a distinctly everted rim, similar to those of Tulpa revelata sp. nov. However, the gonothecae are clearly different.

Ecology and distribution. Tulpa revelata sp. nov. seems to be distributed from the deep waters of the continental shelf to the upper slope. It has been recorded from 80 to 1200 m ( El Beshbeeshy 2011). The holotype was collected at a depth of 126– 129 m. Colonies with gonothecae have been collected in March (present material) and April ( Millard 1977; Soto Àngel & Peña Cantero 2015).

Tulpa revelata sp. nov. seems to be a sub-Antarctic species. Millard’s (1977) material comes from the Kerguelen and Crozet islands, but most records are from the Patagonian region ( Vervoort 1972; El Beshbeeshy 2011; Soto Àngel & Peña Cantero 2015; present material).

Etymology. The specific name revelata derives from the Latin adjective revelatus, meaning revealed, unveiled and conveys the idea that the true nature of the species has been uncovered.