Tubularia longstaffi Hickson & Gravely, 1907

ÁLVARO L. PEÑA CANTERO, 2017, Benthic hydroids (Cnidaria, Hydrozoa) from the Ross Sea (Antarctica) collected by the New Zealand Antarctic expedition BioRoss 2004 with RV Tangaroa, Zootaxa 4293 (1), pp. 1-65 : 19-21

Tubularia longstaffi Hickson & Gravely, 1907

( Figs 6–8 ; Table 4)

Tubularia longstaffi Hickson & Gravely, 1907: 14 –15, pl. 2 fig. 11.

Material examined. Stn 71, 25 stems up to 55 mm high (NIWA 117482); Stn 72, six stems up to 60 mm high, without polyps (NIWA 117483); Stn 104, single stem 78 mm high, with gonophores (MNCN 2.03/531); Stn 105, 20 stems up to 110 mm high, most without polyps (MNCN 2.03/532); Stn 150, one stem 140 mm high (NIWA 117484); Stn 178, 19 stems up to 60 mm high, some without polyps, with gonophores (NIWA 117485); Stn 198, one stem 21 mm long, without polyp (NIWA 117486).

Other material examined. Tubularia longstaffi Hickson & Gravely, 1907 (type material, Natural History Museum, London, Coel no. 1907.8.20.9): McMurdo Bay, Ross Sea, No. 6 hole, April 8th, 1903, 227 m.

Description. Stem up to 140 mm high. Perisarc tube reaching base of polyp, yellow, transversally ringed ( Fig. 6 A), relatively firm, becoming weak and translucent distally ( Fig. 6 B). Tube diameter increasing distally, from ca. 250 µm basally to 1 mm distally. Coenosarc attached to inner side of tube, with about 14 similar longitudinal lines. Polyps 2–5 mm high and 2–5 mm in maximum diameter, with aboral crown of 11 to 20 filiform tentacles (about 5 mm in length) ( Fig. 6 C), and oral crown of 30–32 filiform tentacles (ca. 1.5 mm in length) ( Fig. 6 D).

Fertile polyps with ca. ten unbranched blastostyles (ca. 1150 µm in length), each with ca. 17 gonophores (largest ca. 400 x 250 µm) ( Fig. 6 B–D).

Cnidome ( Fig. 7 ) consisting of stenoteles in two size classes, two types of haplonemes and desmonemes.

Measurements (in µm). Stn 178: Cnidome: stenoteles I [range 9.0–11.0 x 7.0–8.0, mean 10.0±0.7 x 7.7±0.4 (n=10); ratio, range 1.2–1.5, mean 1.3±0.1 (n=10)]; stenoteles II [range 11.5 x 11]; rounded haplonemes [range 13.0–15.0 x 9.0–11.0]; tear-shaped haplonemes [range 14.0–16.0 x 4.5–5.5, mean 14.4±0.6 x 5.1±0.3 (n=9); ratio, range 2.6–3.2, mean 2.9±0.2 (n=9)]; desmonemes [range 6.0 x 4.0]. Stn 150: Cnidome: stenoteles I, abundant [range 10.0–11.5 x 7.0–8.5, mean 10.4±0.5 x 7.6±0.5 (n=7); ratio, range 1.3–1.4, mean 1.4±0.1 (n=7)]; stenoteles II, scarce [range 13.5–14.0 x 12.0–13.0]; rounded haplonemes [range 14.0–16.0 x 9.5–11.0, mean 15.1±0.8 x 10.3±0.6 (n=6); ratio, range 1.4–1.6, mean 1.5±0.1 (n=6)]; tear-shaped haplonemes [range 13.5–17.0 x 4.5–6.0, mean 15.5±1.0 x 5.2±0.5 (n=7); ratio, range 2.3–3.4, mean 3.0±0.3 (n=7)].

Description (Type of Tubularia longstaffi ). Stem broken into three parts: basal part corresponding to hydrorhizal stolon; 44 mm long middle part corresponding to basal part of stem ( Fig. 8 A); distal part with hydranth ( Fig. 8 C). Diameter of stem distinctly increasing distally, from ca. 0.5 mm basally to ca. 1.5 mm distally. Stem perisarc yellowish, transversally striated ( Fig. 8 B). Stem with ca. 14 longitudinal coenosarc strands. Polyp ( Fig. 8 C) with oral crown of over 50 filiform tentacles, aboral whorl with 25 filiform tentacles, ca. 13 mm long, merged basally.

Blastostyles unbranched, with up to 23 well developed gonophores ( Fig. 8 D–F), except by incipient grouped gonophores at base of blastostyles.

Cnidome consisting of stenoteles, apparently in two size classes, two types of haplonemes and desmonemes.

Measurements (in µm). Cnidome: stenoteles I [range 10.0–10.5 x 7.0–8.0, mean 10.1±0.2 x 7.5±0.2 (n=10); ratio, range 1.3–1.4, mean 1.3±0.0 (n=10)]; stenoteles II [range 11.0–14.0 x 10.0–12.5, mean 12.7±1.2 x 11.5±1.1 (n=3); ratio, range 1.0–1.2, mean 1.1±0.1 (n=3)]; rounded haplonemes [range 15.0–16.0 x 10.5–12.0, mean 15.6±0.5 x 11.3±0.5 (n=10); ratio, range 1.3–1.5, mean 1.4±0.1 (n=10)]; tear-shaped haplonemes [range 14.5–16.0 x 5.0–6.5, mean 15.4±0.5 x 5.7±0.5 (n=10); ratio, range 2.5–3.0, mean 2.7±0.2 (n=10)]; desmonemes [range 6.5 x 4.5].

Remarks. After examining the type material of Tubularia longstaffi , I have no doubt that the BioRoss 2004 material belongs to that species, by their similar stem structure and cnidome. Diameter of the stem distinctly increases distally and the perisarc is yellowish and transversally striated. In relation to the cnidome, both have stenoteles, in two size classes, two types of haplonemes and desmonemes, all of similar size (cf. Table 4). The only difference is the slightly smaller number of oral tentacles in the present material (type material of T. longstaffi with over 50 tentacles).

Tubularia Tubularia ralphii Tubularia Tubularia Tubularia hodgsoni (Hickson & longstaffi longstaffi longstaffi (Type) Gravely’ material) (Type) Stn 150 Stn 178

Smaller Range 8.5–10.0 x 10.0 x 10.0–10.5 x 10.0–11.5 x 7.0– 9.0–11.0 x

stenoteles 7.0–7.5 7.5–8.0 7.0–8.0 8.5 7.0–8.0

Mean 9.3±0.5 x 10.0±0.0 x 10.1±0.2 x 10.4±0.5 x 10.0±0.7 x 7.2±0.2 (n=10) 7.8±0.2 (n=5) 7.5±0.2 (n=10) 7.6±0.5 (n=7) 7.7±0.4 (n=10)

Rounded Range 14.0–15.5 x 14.5–15.5 x 15.0–16.0 x 14.0–16.0 x 9.5– 13.0–15.0 x

haplonemes 10.0–13.0 10.5–11.5 10.5–12.0 11.0 9.0–11.0 Mean 14.8±0.5 x 15.0±0.3 x 15.6±0.5 x 15.1±0.8 x - 11.5±0.9 (n=10) 11.5±0.9 (n=7) 11.3±0.5 (n=10) 10.3±0.6 (n=6)

Tear-shaped Range 13.5–15.0 x 13.0–14.0 x 14.5–16.0 x 13.5–17.0 x 4.5– 14.0–16.0 x

haplonemes 4.5–6.0 5.0–5.5 5.0–6.5 6.0 4.5–5.5

Mean 14.3±0.6 x 13.7±0.4 x 15.4±0.5 x 15.5±1.0 14.4±0.6 x 5.2±0.5 (n=10) 5.1±0.2 (n=5) 5.7±0.5 (n=10) x 5.2±0.5 (n=7) 5.1±0.3 (n=9)

Larger Range - - 11.0–14.0 x 13.5–14.0 x 12.0– 11.5 x 11

stenoteles 10.0–12.5 13.0

Mean - - 12.7±1.2 x - - 11.5±1.1 (n=3)

Desmonemes 6.0–6.5 x 6.0 x 4.5 6.5 x 4.5 - 6.0 x 4.0 4.0–4.5

I have also studied the type material of Tubularia hodgsoni and the material assigned to Tubularia ralphii by Hickson & Gravely (1907). Both agree with T. longstaffi , and the material studied here, in the structure of the stem, having yellowish and transversally striated tubes, whose diameter also increases distally in T. hodgsoni . They also agree with T. longstaffi in the size of the nematocysts they share (cf. Table 4). Nevertheless, they appear to lack the larger stenoteles and, consequently, I prefer to keep them apart. I have found no differences between T. hodgsoni and the material described as T. ralphii by Hickson & Gravely (1907) and, therefore, this should be considered as T. hodgsoni .

Ecology and distribution. Tubularia longstaffi was only known from McMurdo Bay, in the Ross Sea ( Hickson & Gravely, 1907), where it was collected at a depth of 227 m, with gonophores in April. Present material, which constitutes the second record of the species, was collected at depths between 222 and 630 m, off Cape Adare, Adare Peninsula, Moubray Bay and Cape Hallet. Gonophores in February.

Figures

FIGURE 6. Tubularia longstaffi Hickson & Gravely, 1907: A, fragment of hydrocaulus; B, distal part of hydrocaulus and polyp; C, polyp and gonophores (lateral view); D, polyp and gonophores (upper view). (All images from Stn 105). Scale bar: B: 5 mm; A, C, D: 1 mm.

FIGURE 7. Cnidome of Tubularia longstaffi Hickson & Gravely, 1907: A, larger stenoteles (arrow); B, smaller stenotele (arrow); C, haploneme (arrow); D, haploneme (arrow). (All images from Stn 150). Scale bar: 10 µm.

FIGURE 8. Tubularia longstaffi Hickson & Gravely, 1907 (type material): A, general aspect of hydrocaulus; B, part of hydrocaulus with striation; C, distal part of hydrocaulus and polyp; D – E, blastostyles and gonophores; F, detail of gonophores. Scale bar: A, C – D: 5 mm; B, E – F: 1 mm.