Mycale (Aegogropila) orientalis

Mycale (Aegogropila) orientalis (Topsent, 1897)

Figs 4 a–i, 5a–h, 6a–i, 7, Tables 1, 2

Esperella sordida var. orientalis Topsent, 1897: 459.

Mycale aegagropila; sensu Wilson, 1925: 426; Rao 1941: 445 (not: Johnston 1842)

Carmia orientalis; Lévi 1956: 17; Desqueyroux 1981: 739, figs 35–39.

Carmia contarenii; sensu De Laubenfels 1951 a: 261, fig. 8; Bergquist 1977: 65 (not: Lieberk̹hn 1859).

? Mycale sulevoidea; sensu Lévi 1961a: 16, fig. 20; Vacelet & Vasseur 1971: 86; Pulitzer-Finali 1993: 290 (not: Sollas 1902).

? Mycale sp. 1 sensu Vacelet & Vasseur 1971: 88, fig. 38.

Material examined. Holotype MHNG C12 /4, slide of Esperella sordida var. orientalis, Ambon, Ambon Bay, between corals, depth 0-10 m (cf. Topsent, 1897, p. 425).

ZMA Por. 01604, Indonesia, depth 36 m, coll. Siboga Expedition, field nr. SE1295, details not certain, possibly from stat. 303, year 1899; ZMA Por. 01612, Indonesia, Nusa Tenggara, Timor, Samau Island, Haingsisi, 10.2050°S 123.4591°E, depth 23 m, coralline algae, coll. Siboga Expedition, stat. 060, fieldnr. SE 12 III, 27 April 1899; ZMA Por. 02889, Indonesia, Nusa Tenggara, Postillion Islands, anchorage off Pulau Sarassa, 7.1833°S 118.2°E, depth 38 m, coll. Siboga Expedition, stat. 043, fieldnr. SE 1291 V, 4-5 April 1899; ZMA Por. 02890, Indonesia, Nusa Tenggara, Flores, W coast, Bay of Badjo, 10.2050°S 123.4591°E, depth 40 m, dredge, coll. Siboga Expedition, stat. 050, fieldnr. SE 1313IIB, 16-18 April 1899; ZMA Por. 02900, Indonesia, Nusa Tenggara, Postillion Islands, anchorage off Pulau Sarassa, 7.1833°S 118.2°E, depth 36 m, coll. Siboga Expedition, stat. 043, fieldnr. SE 1291 II, 5 April 1899; ZMA Por. 07978b, Indonesia, Nusa Tenggara, NE coast of Sumba, E of Melolo, 9.9169°S 120.75°E, depth 1–4 m, gently sloping reef flat, coll. R. W.M. van Soest, snorkeling, Indonesia-Dutch Snellius II Expedition stat. 052, field nr. 052 / II/22, 13 September 1984 (color red). ZMA Por. 10360, Seychelles, Mahé, NE coast, Cap Maçons and Anse de Forbans, 4.7667°S 55.5167°E, depth 0-6 m, coll. R. W.M. van Soest, snorkeling, Netherlands Indian Ocean Expedition stat. 612, 14 December 1992; ZMA Por. 11929, Seychelles, Amirantes, Poivre Atoll, N rim, reef slope, 5.75°S 53.3°E, depth 10–15 m, coll. R. W.M. van Soest, SCUBA, Netherlands Indian Ocean Expedition stat. 767, fieldnr. IOP-E 767/02, 29 December 1992 (color orange-red); ZMA Por. 15818, Seychelles, Mahé, NE of Aride Island, 4.1667°S 55.7333°E, depth 55 m, coll. R. W.M. van Soest, Agassiz trawl, Netherlands Indian Ocean Expedition stat. 714, fieldnr. IOP-E 714/06, 19 December 1992 (color orange); ZMA Por. 17025, Oman, Kuria Maria Islands, Al Hallaniya main island, tidal region, on dead shell between stones, coll. R. G. Moolenbeek & H. Dekker, fieldnr. 91/61, 12 November 1991; ZMA Por. 17254, Oman, no further locality data, on dead shell, coll. R.G. Moolenbeek, fieldnr. MOO 02/04, December 2002; ZMA Por. 22274, Seychelles, Mahé, NE of Aride Island, 4.1667°S 55.7333°E, depth 55 m, coll. R. W.M. van Soest, Agassiz trawl, Netherlands Indian Ocean Expedition stat. 714, fieldnr. IOP-E 714/06, 19 December 1992 (color orange).

Description (Figs 4a, 5a, 6a). The type is described as a network of creeping flattened lobes, which also applies to four Siboga specimens (ZMA 01604, 1612, 2889, and 2900). These show some tendency to be elongated branchlike, but other specimens are irregularly massive or thinly encrusting. All shallow-water specimens are encrusting without a definite form. Sizes vary, with largest encrusting specimen measuring 5 x 6 cm (ZMA 11929). A specimen from deeper water (ZMA 22274) consists of thin orange branches up to 2–3 cm long each. All specimens are soft. Colors where known are orange-red, orange or red, which keeps in alcohol in the more recently collected specimens but fades to light beige in older specimens. Surface smooth or more irregular, variable.

Skeleton (Figs 4b, 6b). The ectosomal skeleton is a tangential reticulation of moderately thick spicule tracts, not clearly bound by spongin, so it tends to become confused in several specimens. In the type the skeletal tracts average 25 µm in diameter, with 5–6 spicules in cross section, other specimens may have slightly thicker tracts, up to 35 µm. Meshes enclosed in the type are 200–400 µm in size, and this may be slightly larger or smaller in the remaining specimens, ranging from 150–450 µm. Most specimens have rosettes of anisochelae I, positioned on the tracts or on the crossings. The type has relatively few rosettes, but several specimens have them abundantly, while ZMA 02889 appears to lack them. Size of rosettes 100–110 µm diameter. The choanosomal skeleton consists of the usual plumose spicule tracts fanning out to carry the ectosomal reticulation. Tracts are relatively thin just below the surface, 30–60 µm in diameter (5–13 spicules in cross section), and become gradually more robust interiorly, with 70–120 µm as maximum diameter. They are rather closely positioned, approximately 300–600 µm apart.

Spicules (Figs 4 c–i, 5b–h, 6c–i). Mycalostyles, anisochelae in three categories, sigmas in two categories, and toxas.

Mycalostyles (Figs 4c,c 1, 5b,b 1, 6c,c 1), rather robust, with faintly developed constriction of neck and elongate head, 231– 295.6 –381 x 4– 7.8 – 12 µm (type: 288-324 x 5–6 µm).

Anisochela I (Figs 4d, 5c, 6d), rather robust, alae mostly well-developed, and the shaft straight and free for about 1/3 of the spicule length, with outwardly curved upper median alae, variable in size among specimens, 32– 42. 1 – 57 µm (type 41–45 µm).

Anisochelae II (Figs 4e, 5d,d 1, 6e), narrow-shaped, with upper alae longer than half the length of the spicule, often about 2/ 3 in length of the spicule. Upper frontal alae in Indian Ocean specimens rather ‘bulbous’, curved inwards at the lower ala rim. Lower alae well developed, sometimes with undulate rim or provided with a median protrusion. Free part of the shaft short. Size variable, 18– 23.8 – 30 µm (type: 22–27 µm).

Anisochelae III (Figs 4f, 5e, 6f), variable shape, often narrow-shaped similar to anisochela II, but with longer free part of the shaft; normally with median upper ala slightly more expanded outward; lower median ala with median protrusion, 9– 14.1 – 19 µm.

Sigmas I (Figs 4g,g 1, 5f, 6g), robust, strongly curved near the apices, inequiended, quite variable in size, 51– 90.5 – 121 µm, thickness 2–9 µm.

Sigmas II (Figs 4h, 5g, 6h), thin, more openly curved than sigma I, variable in size, 9– 23.7 – 38 µm.

Toxas (Figs 4i, 5h, 6i), usually wing-shaped, deeply curved, but more gradually curved forms also common, very large size range in Indonesian specimens, less so in Indian Ocean specimens, large toxas are also thicker, up to 2 µm, smaller toxas thin, overall they range 31– 111.6 – 384 µm.

Distribution and ecology (Fig. 7). In our material specimens of this species originated from Indonesia (as did Topsent’s type), Oman, and the Seychelles, from shallow reefs down to 55 m. The species has not been reported often, but records may be hiding under different names, e.g. some specimens may have been identified as M. (Ae.) sulevoidea. Wilson’s (1925) and Rao’s (1941) records of the European species Mycale aegagropila (Johnston, 1842) [= M. (Ae.) contarenii (Lieberk̹hn, 1869)] from the Philippines and India possibly concern the present species, although it could be also M. (Ae.) sulevoidea as no images of the spicules were provided. Carmia contarenii by De Laubenfels, 1951 from Hawaii is likely also this species.

Records of M. sulevoidea by Lévi (1961a), Vacelet & Vasseur (1971) and Pulitzer-Finali (1993) from the Western Indian Ocean (Aldabra, Madagascar, Kenya) are likely assignable to M. (Ae.) orientalis based on spicule sizes and drawings of anisochelae II. Vacelet & Vasseur’s (1971) Mycale sp. 1 conforms in most details to the present species, although their small sigmas/toxas (their Fig. 38g) look peculiar. If these records indeed concern the present species, its distribution covers a wide area, from the Western Indian Ocean eastward to Hawaii.

Aproximate localities where M. (Ae.) orientalis specimens have been found or probably have been found are presented in Fig. 7.

Remarks. A slide of Topsent’s holotype was re-examined. Neither Topsent’s (1897) description, nor Desqueyroux’s (1981) redescription mention the presence of narrow-shaped anisochelae II. They are more rare than anisochelae I and III, but nevertheless clearly present in the slide.

The present species has the same spicule complement as M. (Ae.) sulevoidea (cf. below), but differs from that species in the possession of flattened but not duck-beaked anisochela II, which are also smaller in length. It is a subtle difference, but under SEM it is unmistakable. In view of the rather common widespread occurrence of the species in our samples and the scarceness of reports in the literature, it is quite imaginable that older records of M. (Ae.) sulevoidea may have sometimes been mistaken for M. (Ae.) orientalis.

SEM images of 9 specimens were made and these showed some variability in shapes of anisochelae III (more narrow or more squat) and of toxas (deeper or shallower curved). The species is apparently widespread, occurring in Indonesian as well as in Seychelles and Oman waters. The spicule complement of the two ‘populations’ were compared and this resulted in small, subtle differences, although a clear separation is not found. Toxa upper length of Indonesian specimens appears greater and sigma I size of Indonesia specimens on average seems slightly larger. The upper frontal alae of anisochelae II of Western Indian Ocean specimens is often more robust and rather bulbous compared to that in Indonesian specimens. A comparison between spicule size data of West Pacific and Indian Ocean specimens (cf. Table 1) indicates there is very little difference and the species seems homogeneous over the entire region as far as spicule sizes are concerned. These differences do not point to geographic differentiation.

M. (Ae.) tapetum Samaai & Gibbons, 2005 (p. 76) from the West coast of South Africa is rather similar in spicule complement to the present species. No sigmas II were reported, the toxas measure only 46–48 µm, and there were apparently raphides of 23 µm (not shown in the drawing of the spicules of their fig. 53).

De Laubenfels’ (1951) Hawaii record of the European species Carmia contarenii (Lieberk̹hn, 1859) was suggested to be M. (Ae.) orientalis by Lévi (1956). Although no anisochelae II were mentioned, it is here assumed that they were present, but overlooked.

Elsewhere, there is similar spiculation in Mexican Pacific Mycale (Aegogropila) magnitoxa Carballo & Cruz-Barraza, 2010, but anisochela II of that species is less narrow, and mycalostyles are significantly shorter and thinner.