Mycale (Arenochalina) imperfecta Baer 1906

Mycale (Arenochalina) imperfecta Baer, 1906

Figs 20 a–g, 21a–d, 22a–d, 23

Mycale imperfecta Baer, 1906: 20, pl. II fig. 5, pl. V figs 3–8; Vacelet & Vasseur 1971: 86, fig. 35; Pulitzer-Finali 1993: 291; Barnes & Bell 2002 a: table 1 (listed only).

Mycale fistulata Hentschel, 1911: 292, fig. 4.

Mycale fistulata var. macrochela Hentschel, 1911: 294.

? Mycale monanchorata Burton & Rao, 1932: 329, text-fig. 6; Rao 1941: 446.

Mycale trincomaliensis Rao, 1941: 447, pl. XII fig. 19, text-figs 23–25.

Mycale spongiosa; Thomas 1973: 36, pl. II fig. 8, pl. V fig. 9, pl. VII fig. 8 (not: Dendy 1896 = M. (Ar.) mirabilis).

Mycale tylostrongyla Pulitzer-Finali, 1982a: 102, figs 13–14.

? Mycale sp. Thomas 1973: 37, pl. II fig. 9, pl. V fig. 6.

Mycale setosa; Van Soest 1984: 30; Erpenbeck et al. 2016: supplementary data COI tree (not: Gelliodes setosa Keller, 1889).

Mycale tricomaliensis (sic); Pattanayak 2009: 26.

Material examined. ZMB 4398 (Figs 26a), syntype (2 specimens, 2 slides) of Mycale fistulata Hentschel, 1911, Australia, West Australia, Sharksbay, ca. 6 miles S of Denham, coll. R. Hartmeyer & W. Michaelsen 1905; ZMB 4399 (Fig. 26b), holotype of Mycale fistulata var. macrochela, Australia, Sharksbay, South Passage, coll. Hartmeyer & Michaelsen.

ZMA Por. 01611, Indonesia, N Maluku, Halmahera, anchorage N of Salomakiee (Damar) Island, 0.942°S 128.3241°E, depth 45 m, bottom coralline algae, dredge, coll. Siboga Expedition stat. 144, field nr. SE1199, 7 August 1899; ZMA Por. 11438, Seychelles, Mahé, Praslin Island, NW coast, Chevalier Bay, 4.2833°S 55.7°E, depth 2–10 m, SCUBA, coll. R. W.M. van Soest, Netherlands Indian Ocean Expedition stat. 703, field nr. IOP-E 703/11, 17 December 1992 (dirty grey); ZMA Por. 12656, Seychelles, Mahé, NE of Aride Island, 4.2°S 55.6833°E, depth 40 m, rectangular dredge, coll. R. W.M. van Soest, Netherlands Indian Ocean Expedition stat. 715, field nr. IOP-E 715/02, 19 December 1992 (purple); ZMA Por. 12657, Seychelles, Mahé, E of Bird Island, 3.75°S 55.2333°E, depth 45 m, trawl, coll. R. W.M. van Soest, Netherlands Indian Ocean Expedition stat. 720, field nr. IOP-E 720/20, 20 December 1992; ZMA Por. 12703, Seychelles, Amirantes, St. Joseph Atoll, NW rim, reef slope, 5.4167°S 53.3167°E, depth 5–22 m, SCUBA, coll. R. W.M. van Soest, Netherlands Indian Ocean Expedition stat. 753, field nr. IOP-E 753/22, 26 December 1992 (purple); ZMA Por. 13409, Seychelles, Mahé, SE coast near Pointe Cocos, coral rubble, 4.75°S 53.55°E, depth 40 m, rectangular dredge, coll. R. W.M. van Soest, Netherlands Indian Ocean Expedition stat. 738, field nr. IOP-E 738/17, 24 December 1992 (rose-purple); ZMA Por. 13728, Seychelles, Mahé, W of Bird Island, 3.6833°S 55.2°E, depth 1 m, snorkeling, coll. W. Kooistra, Netherlands Indian Ocean Expedition stat. 722, field nr. IOP-E 722/1A, 19 December 1992; ZMA Por. 17888, Oman, Dhofar province, Mirbat Peninsula, 16.95°N 54.82°E, depth 5–15 m, SCUBA, coll. R.G. Moolenbeek, R. Gómez & O. Eerland, December 2002.

Description (Figs 20 a–d, Figs 21a, Figs 22a,a 1). Cushion-shaped, erect-lobate, or thick encrustations. Size of specimens up to 10 x 8 x 4 cm. Color in life purple or greyish purple. Surface flaky and/or irregularly smooth to spiny (preserved condition), due to choanosomal fibres protruding through the surface membrane. In preserved samples oscules small and spread over the surface. Consistency compressible, rather soft.

Skeleton (Figs 20 e–g). As usual for the subgenus, the skeleton consists of a reticulation of spongin-encased spicule tracts. In this species, the spongin is often almost entirely obscured by the solid mass of the mycalostyles. Meshes are square, 1–2 mm wide, with primary tracts 200–300 µm in diameter and secondary tracts of 10–100 µm anastomosing at right angles. Microscleres common, anisochelae arranged in rosettes (Fig. 20g) of up to 65 µm in diameter.

Spicules (Figs 21 b–d, 22b–d). Mycalostyles, one size of anisochelae, one size of sigmas.

Mycalostyles (Figs 21b,b 1, 22b,b 1), variable in thickness, straight, with oval heads, 241– 275.2 –309 x 2– 5.4 – 10 µm.

Anisochelae (Figs 21c, 22c), variable in length and in abundance among specimens but less so within a given specimen, with prominent upper lateral alae and narrow median alae, fully developed lower alae, 18– 25.5 – 42 µm.

Sigmas (Figs 21d, 22d), variable in size, but within an individual there is less variation; no sigma size categories are evident; most are almost half-circular in outline, with slightly incurved apices; occasionally they are more elongate in shape, 42– 74.6 – 104 µm.

Distribution and ecology (Fig. 23). Indonesia, Seychelles, Oman, Zanzibar, Madagascar, West Australia, India, in shallow reefs down to 45 m.

Remarks. Type specimens of Mycale fistulata Hentschel, 1911 and its variety macrochela were re-examined and re-assigned to Baer’s species, which has priority. Microscleres among the various specimens here assigned to M. (Ar.) imperfecta show the same large range of sizes (anisochelae 18–42 µm, sigmas 45–104 µm) as in M. (Ar.) regularis, a size range that in other subgenera of Mycale would cover two or more categories. However, the size range within specimens of this species is narrow, with little variation in size, whereas among specimens it is wide, but no regional patterns are apparent.

The characters distinguishing the present species from other Mycale (Arenochalina) members of the region are lobate shape, purple live color, thin primary and secondary spicule tracks completely filled with often relatively robust mycalostyles. Baer mentions mycalostyles of only 186–246 x 3–4 µm whereas in our specimens these are longer and barely overlap Baer’s specimens, but in view of the large variation of spicule lengths and thickness, this is thought to fall within the variation. Vacelet & Vasseur’s (1971) description of a Madagascar specimen reports longer but equally thin mycalostyles. Baer’s, Vacelet & Vasseur’s and Pulitzer-Finali’s specimens had on average smaller anisochelae, and they do not mention presence of rosettes, but otherwise the descriptions match ours. In our specimens the spicule data show a large range. Hentschel’s (1911) material of Mycale fistulata is similar in shape to Baer’s type, but shares the longer mycalostyles with Vacelet & Vasseur’s (1971) material and the present specimens from the Seychelles. Hentschel’s var. macrochela is here regarded as belonging to this species, but in some individuals the sigmas are larger than average. Future studies might show there is taxonomic diversity in this presumed variable species.

Mycale trincomaliensis Rao, 1941 from India conforms in all aspects to the present species. We believe Thomas’ (1973) description of Mycale spongiosa from the Seychelles likely concerns the present species, as the shape (encrusting a ‘twig’), the skeleton (‘scalariform’ with main fibres of 180 µm diameter cored by 30–50 megascleres), and the spicules (anisochelae in rosettes, fairly large sigmas) match Baer’s and our description. Esperella spongiosa Dendy, 1896 is convincingly synonymized with M. (Ar.) mirabilis by Wiedenmayer (1989). That author also synonymized the present species with M. (Ar.) mirabilis (cf. above), but we disagree because of the consistent differences of our specimens with Von Lendenfeld’s species. That species has erect-pedunculate shape, cream or yellow color, has foreign material enclosed in its primary fibres and its microscleres are virtually absent. In the absence of more definite information we believe that Mycale sp. sensu Thomas (1973) from the Seychelles could also belong to the present species.

Vacelet & Vasseur (1971) suggested the present species is close to Esperella tenuispiculata Dendy, 1905. However, Dendy’s species (cf. also below) has much smaller sigmas (36 µm) and the skeleton and tissue is filled with sand grains and foreign material. It may be closer to M. (Ar.) mirabilis. Below, we recognize specimens in our collection as close to if not conspecific with M (Ar.) tenuispiculata.

Mycale tylostrongyla Pulitzer-Finali, 1982a was also suggested as a synonym of M. (Ar.) mirabilis by Wiedenmayer (1989), but in view of the apparently abundant presence of microscleres, both anisochelae and sigmas, it is perhaps closer to the present species. In contrast, the fibres are described to be filled mostly with sand grains, rendering it not certainly a member of M. (Ar.) imperfecta.

Rosettes of anisochelae are shared with M. (Ar.) regularis Wilson, 1925 (cf. below), and in many other aspects, e.g. the semicircular, slightly incurved shape of the sigmas, this species is closest to the present. However, the habitus of M. (Ar.) regularis is persistently tubular, fibres are thicker and contain more spongin. If Wiedenmayer’s hypothesis of polymorphism in Indo-West Pacific Arenochalina specimens would prove to be for real, then chances are that what we described above under M. (Ar.) euplectellioides and below under M.(Ar.) regularis belong to the same species as the present. In that case, the name M. (Ar.) imperfecta would have priority. We prefer to emphasize the difference in overall shape as a specific feature.

We suggest that Indian Mycale monanchorata Burton & Rao, 1932 could be a junior synonym, even though no sigmas have been reported from it. Several specimens assigned here to M. (Ar.) imperfecta had their sigmas only rarely present (e.g. ZMA. Por. 13728 and 17888), and paucity of microscleres is characteristic of the subgenus Arenochalina in general. Re-examination of the type material is necessary to confirm the synonymy.

In the course of the study of this species we discovered that Mycale fistulata var. macrochela Hentschel, 1911 (here re-assigned to M. (Ar.) imperfecta Baer, 1906) is a senior primary homonym of Mycale macrochela Burton, 1932 from the South Orkney Islands, Antarctica (Burton 1932: 289, pl. 51 fig. 6). Despite the synonymic status of the former, the junior primary homonym must be replaced (ICZN Art. 57.2), and we propose Mycale (Mycale) mauricei sp.nov., named after Maurice Burton (there is already a combination Mycale (Grapelia) burtoni Hajdu, 1995, cf. below).