Tulpa peculiaris Cantero, 2025, sp. nov.
Creators: name: Cantero, Álvaro Luis Peña
Publisher: name: Zenodo
Year: 2025
Subjects: Biodiversity
Taxonomy
Animalia
Cnidaria
Hydrozoa
Leptothecata
Campanulariidae
Tulpa
Tulpa peculiaris

description: Tulpa peculiaris sp. nov.
(Figs 5–6)
Material examined. ACE 14, several colonies with stolonal hydrothecae and male and female gonothecae, on bryozoans, Grammaria sp. and Symplectoscyphus sp. (Holotype, MNCN 2.03/690, colony 40 mm long, with several hydrothecae and female gonothecae, partially growing on bryozoan; Paratype, MNCN 2.03/691, colony with several hydrothecae and male gonothecae, growing on Symplectoscyphus sp.).
Description. Stolonal colony. Stolons on substrate giving rise to long pedicels with single distal hydrotheca. Pedicel perisarc smooth, typically without regenerations.
Hydrotheca tubiform (Fig. 5a–b), almost cylindrical, its diameter distinctly increasing at basal part, then either more or less constant with slight increase at aperture, or smoothly increasing to aperture (Fig. 5a–b); in either case maximum diameter at aperture. Rim of hydrothecal aperture strongly sinuous (Fig. 6b, e) and uneven, with 12 to 16 blunt cusps (Figs 5a–c, 6a–b). Sinuosity creating an alternate sequence of crests and troughs outside and inside hydrotheca (Fig. 6b–g). This resulting in a series of little-marked, barely concave facets on external hydrothecal wall, corresponding to external troughs, strongly fading basally, and laterally delimited by very faint longitudinal ridges coinciding with external crests. Opposite pattern on inner wall. At rim, outside troughs corresponding to cusps and external crests to embayments (Fig. 6b). Distal part of external crests strongly bent outwards (Fig. 6b– g); distinctly lower than non-everted distal part of external troughs (Fig. 6b–g), and thus giving rise to cusps. Hydrothecal perisarc smooth. Rim with up to five renovations (cusps fading on renovations).
Gonothecae arising from stolons, oval-shaped, with a narrow basal part, and distally projecting into a long neck with a circular distal aperture. Female gonothecae (Fig. 5d) distinctly larger than male ones (Fig. 5e), and with much longer neck. Female gonothecae containing many ova (Fig. 5d). Gonothecal perisarc partially finely striated transversally. In male gonothecae, striation typically occurring on their distal half, whereas in female gonothecae, it may extend from one-third (basically over the neck) to two-thirds of their distal length.
Larger nematocysts banana-like (Fig. 6h).
Remarks. The size of the hydrotheca in Tulpa pecularis sp. nov. varies significantly (Fig. 5a–b). Some hydrothecae growing on Symplectoscyphus sp. reach the smallest size.
The rim of the hydrothecal aperture is not completely everted, only the most distal part of the external crests is sharply everted outwards (Fig. 6e, g). At the rim, the external troughs create the cusps, which are straight or even slightly inwardly directed, while the crests form the embayments, which are everted and strongly outwardly directed. In addition, the rim may have a short, thin perisarc projection, also curved outwards in the external crests, but kept upright in the external troughs (Fig. 6f), making the cusps and embayments even more prominent in the side view.
The perisarc of the hydrothecal wall is typically smooth, although barely noticeable striations can occasionally be observed in stained hydrothecae (Fig. 6a).
In Tulpa pecularis sp. nov., the most distal part of the hydrotheca is strongly sinuous (Fig. 6b, e), but the sinuosity decreases rapidly downwards, resulting in a roughly cylindrical hydrotheca, in contrast to T. diverticulata or T. tulipifera, in which the hydrotheca has a distinct polygonal structure. It should be noted, however, that a very faint polygonal structure can be seen in some stained hydrothecae of the material studied herein.
Tulpa peculiaris sp. nov. is easily recognised by the shape of its larger nematocysts, hydrothecae and gonothecae. It is clearly distinguished from the other species of the genus by the absence of a bulbous basal part in the hydrotheca. The diameter increases strongly at the annular perisarc thickening and then smoothly to the aperture, where it reaches its maximum diameter (Fig. 5a–b).
The colony of this species is exclusively stolonal, a feature that at present distinguishes it from T. diverticulata and T. tulipifera, but which it shares with T. costata. However, Tulpa peculiaris sp. nov. differs from Gravier-Bonnet’s species in many characters. The hydrotheca of T. costata has a bulbous basal part and a narrower part below the aperture. They also differ in the size of the hydrothecae (up to 2390 µm in T. costata, but up to 3400 µm in Tulpa peculiaris sp. nov.), and nematocysts (67 × 20 µm in T. costata, 17.5–20.5 × 4.0–4.5 µm in Tulpa peculiaris sp. nov.). According to Gravier-Bonnet, in T. costata, the hydrothecal perisarc is entirely or partially finely striate transversally, whereas in Tulpa peculiaris sp. nov. it is typically smooth. The two species also differ in the gonothecae. Although Gravier-Bonnet was not able to determine the sex, the size and shape of the gonothecae she described coincide with those of the male gonothecae of Tulpa peculiaris sp. nov. However, she characterised the gonothecae of T. costata as having eight distinct longitudinal ridges, which are not present in either the male or female gonothecae of Tulpa pecularis sp. nov.
The gonotheca illustrated by Ralph (1957) from material collected in Bligh Sound, which she identified as T. diverticulata but which clearly does not belong to that species, is similar in shape and size to the female gonotheca of Tulpa peculiaris sp. nov. However, according to Ralph (1957: 844), the neck is provided with ‘about 25 fairly prominent but fine closely spaced annulations’ and the margin of the aperture is everted. In Tulpa peculiaris sp. nov. the rim is not everted and there is only a very fine striation. The shape of the hydrotheca is also different, as in Tulpa peculiaris sp. nov. the diameter increases smoothly distally, whereas in Ralph’s material there is a bulbous basal part, where the diameter is maximum.
The material assigned to T. diverticulata by Vervoort & Watson (2003), which in my opinion clearly belongs to another species, shares the relatively small size of the hydrotheca with Tulpa pecularis sp. nov. However, its shape is clearly different, ‘with a slightly swollen basal part, narrowing somewhat apically and widening again towards hydrothecal rim’ (Vervoort & Watson 2003: 446). The gonotheca they illustrated resembles the male gonothecae of Tulpa pecularis sp. nov. but lacks striations in the perisarc.
Ecology and distribution. Tulpa peculiaris sp. nov. was collected at a depth of 270 m in the Marion/Prince Edward area, epibiotic on bryozoans, Grammaria sp. and Symplectoscyphus sp. Gonothecae were found in December.
Etymology. The specific name “peculiaris ” refers to the peculiar shape of the larger nematocysts when compared to the nematocysts present in the other species studied.
description: Published as part of Cantero, Álvaro Luis Peña, 2025, On the species of Tulpa Stechow, 1921 (Cnidaria, Hydrozoa) with the description of two new species from sub-Antarctic waters, pp. 51-78 in Zootaxa 5633 (1) on pages 63-66, DOI: 10.11646/zootaxa.5633.1.3, http://zenodo.org/record/15372803