Zyzzyzus spongicolus

Campos, Carlos J. A., Marques, Antonio C. & Migotto, Alvaro E., 2007, A taxonomic revision of the genus Zyzzyzus Stechow, 1921 (Cnidaria: Hydrozoa: Tubulariidae), Zootaxa 1627, pp. 1-22 : 7-10

Zyzzyzus spongicolus (von Lendenfeld, 1884)

Table 3

Tubularia spongicola von Lendenfeld, 1884: 597, pl. 26, fig. 50.

Zyzzyzus spongicolus ;— Watson, 1978: 303, fig. 1, C–M; 1982: 85, pl. 7.4, fig. 4.6 a.— Petersen, 1990: 178.—Marques & Migotto, 2001: 469.

Zyzzyzus spongicola ;— Rudman, 1981: 421, pl. 1, fig. 1.— Edmunds, 1987: 189 [incorrect subsequent spelling].

Material examined. Preserved: Australia: Victoria, Port Phillip Bay, Popes Eye Reef (ca. 38°S, 144°50’E), 10 m, 29 Jan 1999, about 40 polyps with gonophores, embedded in sponges, in two samples, coll. and det. J.E. Watson, MZUSP 1978 and MZUSP 1977; Port Phillip Bay, Point Wilson (ca. 38°S, 144°50’E), 0 6 Apr 1999, about 125 polyps with gonophores, embedded in sponge, coll. and det. J.E. Watson, MZUSP 1976.

Description. Hydroids 1.4–4.0 mm in height; hydrocaulus stiff, embedded on horny and soft sponges by expanded hydrorhiza. Hydrorhiza with several bulbous or finger-shaped processes, varied in morphology and length. Hydranth vasiform, hydranth body 0.7–1.0 mm high, 0.2–1.0 mm in maximum diameter. Oral tentacles filiform, 9–12 in number, in one whorl, adnate to hypostome around mouth; tentacles circular in cross section throughout. Aboral tentacles filiform, 11–17 in number, evenly spaced in one whorl at base of hydranth body; tentacles ovate in cross section at bases, circular in cross section at distal free part, 0.7–1.8 mm long, 0.03–0.11 mm in maximum diameter. Fertile hydranths with 4–7 blastostyles, in one whorl above aboral tentacles. Hydranths monoecious, each blastostyle with 2–6 cryptomedusoid gonophores in different developmental stages; male and female gonophores on same blastostyles. Developing male gonophores oval, almost spherical in later developmental stages, with visible spadix, 0.27–0.51 mm long, 0.03–0.11 mm in maximum diameter. Female gonophores with raised collar around orifice at distal region in later developmental stages, enlarged, with up to 3 actinulae. Hydrocaulus flexible, sometimes twisted or bent in several directions, covered by thin perisarc, slightly thickened at basal part of hydrocaulus. Perisarc secreted at region above circular groove, between hydrocaulus and hydranth base. Hydrocaulus sometimes with small tubular hydrorhizal processes at most proximal region and marked by sets of transverse grooves at distal region. Coenosarc of hydrocaulus with endodermal canals, anastomosed along hydrocaulus length at region above thickened perisarc.

Cnidome. Large stenoteles 8.5–11.8 x 7.3–10.8 Μm (10.4 ± 0.97 x 9.5 ± 1.06, n = 14); small stenoteles 5.3–5.5 x 4.3–4.6 Μm (5.4 ± 0.15 x 4.5 ± 0.25, n = 2); basitrichous isorhizae 6.1–7.6 x 2.2–3.7 Μm (6.6 ± 0.49 x 2.7 ± 0.49, n = 7); heterotrichous microbasic euryteles 6.5–8.6 x 3.3–4.3 Μm (7.3 ± 0.73 x 3.7 ± 0,31, n = 15); desmonemes 3.2–4.6 x 2.6–3.0 Μm (3.6 ± 0.39 x 2.8 ± 0.12, n = 9) (hydranth).

Additional data. Watson (1978) described 12 endodermal canals communicating with the gastral cavity of the hydranth. Main body of actinulae 0.25–0.3 mm in diameter, supporting 10–12 aboral tentacles ( Watson 1978).

Colour. Hydranth and tentacles translucent white, main body of the hydranth red, actinulae white, spadix of well developed gonophores orange ( Watson 1978).

Type. Tubularia spongicola von Lendenfeld (1884), AM G10809 and AM G10789 [cf. von Lendenfeld (1884)].

Additional material. Australia: Victoria, Port Phillip Bay, Popes Eye Reef (ca. 38°S, 144°50’E), about 30-40 polyps embedded in sponge, in two samples; about 125 polyps embedded in sponge; New South Wales, Port Jackson, AM G10809, AM G10798.

Remarks. The diagnostic characters of Z. spongicolus are male and female gonophores growing on the same blastostyle (although this character is not known for Z. floridanus because of the scarcity of fertile material), and the raised collar around the orifice in female gonophores. In fact, the species is quite similar to Z. warreni . The tenuous diagnosis of the species was noted by Calder (1988: 50), who stated: “ Z. warreni differs from Z. spongicolus in having male and female gonophores on separate blastostyles instead of on the same ones […]. From the existing descriptions, the two seem otherwise remarkably similar and may prove conspecific.”

Reports of monoecy in Zyzzyzus are somewhat confused in the literature. Calder (1988) defined the genus as monoecious, and Marques & Migotto (2001) extended this interpretation to Z. spongicolus , Z. calderi , and Z. warreni in their study based both on Petersen’s (1990) data and on the description of Z. warreni by Migotto & Silveira (1987). Our observations from extensive collections demonstrate that species of Zyzzyzus are monoecious, with gonophores of different sexes either developing on the same or on different blastostyles (uncertain for Z. floridanus ; see above). From our observations, Zyzzyzus spongicolus is the only species of the genus in which male and female gonophores are both present on the same blastostyle.

Von Lendenfeld (1884) described Tubularia spongicola from hydroids collected in Port Jackson, New South Wales, Australia (material AM G10809 and AM G10789). Watson (1978) re-examined von Lendenfeld’s material, remarking on some imprecise observations regarding the morphology of oral tentacles and branching of blastostyle, and complemented von Lendenfeld’s description concerning the number of aboral tentacles and structure of gonophores and hydrorhizal processes. Our study of Australian material agrees with the general descriptions of von Lendenfeld (1884) and Watson (1978) regarding morphometric features, morphology of the hydranth, region of perisarc secretion and hydrocaulus, and morphology of blastostyles and gonophores. However, we observed some slight differences in composition and dimensions of nematocysts. Watson (1978) described large stenoteles 7.5–9.0 x 9.5 Μm; small stenoteles, 5.5 x 3.0 Μm; basitrichous isorhizae, 8.0 x 3.5 Μm and heterotrichous anisorhizae, 3.0 x 5.0 Μm and the number of oral and aboral tentacles. She also reported 12–16 aboral tentacles, and 10–12 oral tentacles. However, she studied live material, which may account for part of the difference.

Zyzzyzus spongicolus presents great variability in the morphology of hydrorhizal processes, apparently as a phenotypic response to the skeletal structure of the sponge. Similar observations have been made for Z. warreni .

x ± SD (in Μm) Range (in Μm) n

Hydrorhiza

Number of processes - - - Length - - - Diameter - - - Hydrocaulus

Length 1777 ± 599 722–2918 9 Proximal diameter 347 ± 155 210–755 25 Median diameter 315 ± 86 191–464 22 Distal diameter 281 ± 76 118–395 22 Hydranth

Total length 869 ± 202 679–1075 4 Length from aboral tentacle bases to hypostomial tip 523 ± 145 350–653 4 Diameter at base 534 ± 187 262–1047 17 Oral tentacles

Number 11 ± 1 9–12 19 Length - - - Diameter - - - Aboral tentacles

Number 13 ± 2 11–17 19 Length 1162 ± 427 696–1770 8 Diameter 70 ± 20 32–110 35 Gonosome

Total number - - - Male gonophore

Number 4 ± 2 2–6 5 Length 381 ± 99 275–514 5 Diameter 285 ± 78 212–413 5 Female gonophore

Number - - - Length - - - Diameter - - - Blastostyles

Number 6 ± 1 4–7 5 Length - - - Diameter - - - Distribution. Eastern Indian Ocean: shallow-waters off Port Phillip Bay (ca. 38°S, 144°50’E), Victoria, Australia. Southwest Pacific: Port Jackson (ca. 33°50’S, 151°15’E), New South Wales, Australia ( Watson 1978); Montague island (36°16’S, 150°12’E), south of Narooma, New South Wales, Australia; Green Point (33°55’S, 151°10’E), Sydney Harbour, New South Wales, Australia ( Rudman 1981).

Ecology. Substratum. Species with “fuzzy growth” on orange-coloured sponges in sheltered ocean bays ( Watson 1982: 85).

Seasonality. From April to December ( Watson 1978, 1982).

Associations. Z. spongicolus is a preferred food item of the nudibranch Cuthona kuiteri , whose cerata developed processes acting as a kind of mimetic “special resemblance” with Z. spongicolus tentacles ( Edmunds 1987: 191).