Mycale (Mycale) sundaminorensis Van & Aryasari & De 2021, n.sp.

Mycale (Mycale) sundaminorensis n.sp.

Figs 89 a–d, 90a–h, 91a–b

Mycale murrayi; Burton 1959: 228 (not: Ridley & Dendy 1886: 338).

Mycale massa var. oceanica; Burton 1959: 229 (not: Topsent 1924).

Material examined. Holotype ZMA Por. 01603, Indonesia, Nusa Tenggara, off E coast of Sumbawa, 8.5°S 119.125°E, depth 73 m, dredge, coll. Siboga Expedition stat. 310, field nr. SECXIII–II, 12 February 1900.

Examined for comparison: BMNH 1936.3.4.541, Mycale massa var. oceanica sensu Burton, 1959, from the South Arabian coast, 21.8333°N 59.8667°E, depth 1046 m; BMNH 1887.5.2.155, holotype of Esperella murrayi Ridley & Dendy, 1886, from Port Jackson; BMNH 1936.3.4.542, holotype of Mycale topsenti Burton, 1959, from South Arabian coast, 21.8333°N 59.8667°E, depth 1046 m; BMNH 1923.10.1.102, spicule slide of holotype of Mycale (Mycale) novaezealandiae Dendy, 1924, from Three Kings Island, New Zealand.

Description (Fig. 89a). Globular sponge of 3 cm diameter, with a disk-like area of attachment. Color in alcohol dirty white, tending to light beige. Surface optically smooth but microscopically uneven, rough. No visible oscules or openings. Consistency firm.

Skeleton (Figs 89 b–d). Plumose thick spicule tracts of 150–200 µm diameter (approximately 15 spicules in cross section) traverse the choanosome and fanning out at the surface carry the ectosomal skeleton (Fig. 89b). They are spaced parallelly at distances of 200–500 µm and have only few interconnecting tracts. The inner parts of the choanosome contain also a mass of megascleres strewn without direction. The region between this unorganized interior skeleton and the surface is occupied by large lacunae crossed over only by skeletal tracts, sparingly ‘echinated’ by groups of anisochelae. Ectosomal region (Fig. 89c) a dense mass of tangentially arranged megascleres pierced by brushed endings of the choanosomal spicule tracts. These brushes are responsible for the rough surface. Anisochelae do not form clear rosettes, but form small groups (pseudorosettes, cf. Fig. 89d) of 4–5 spicules attached here and there to the spicule tracts.

Spicules (Figs 90 a–h). Mycalostyles in two distinct size categories, three categories of anisochelae, two categories of sigmas, and trichodragmas.

Mycalostyles I (Figs 90a,a 1), found especially frequent in the choanosomal tracts and the surfaces brushes, long and thin, thickest about halfway the length of the spicule, slightly curved, occasionally slightly sinuous, heads elongate, with barely any constriction subterminally (at low magnification appearing oxea-like), 901–998.3– 1092 x 12 – 15.4 – 19 µm.

Mycalostyles II (Fig. 90b), found especially in the ectosomal crust but occurring also in the choanosomal spicule mass, generally similar to mycalostyles I, but more curved and looking more robust because of having the same thickness while being shorter, 591– 621.6 –678 x 12– 13.3 – 16 µm.

Anisochelae I (Fig. 90c), with upper and lower alae broadly developed, with free part of the shaft about 40–45% of spicule length, 71– 87.5 – 98 µm.

Anisochelae II (Fig. 90d), elongated oval in shape, with both upper and lower alae well-developed, compared to anisochelae I they are more narrow-shaped, 28– 36.1 – 42 µm.

Anisochelae III (Fig. 90e), similar in shape to anisochelae II, but only almost half the length, and provided with a small spur, 19– 22.2 – 27 µm.

Sigmas I (Fig. 90f), thin (about 1 µm in thickness), normal shaped, symmetrical, 42– 45.9 – 50 µm.

Sigmas II (Fig. 90g), comparatively thick (1.5–2 µm in thickness), symmetrical, with ends incurved and bluntending, occasionally slightly swollen, 19– 25.6 – 32 µm.

Trichodragmas (Figs 90h), variable in length, but no distinct categories, comparatively thick and tending to be fusiform, 35– 78.0 –91 x 10– 13.2 – 18 µm.

Etymology. The name is a composite word meaning ‘from Lesser Sunda’ referring to the province in which the type locality is found.

Distribution and ecology. Dredged between Sumbawa and Pulau Banta at 73 m depth.

Remarks. The new species is characterized by the two distinct size classes of mycalostyles and the peculiarly shaped sigma II. Burton (1959) reported a specimen named Mycale massa var. oceanica Topsent, 1924 from the South Arabian coast (21.8333°N 59.8667°E) at considerable depth (1046 m). The specimen (BMNH 1936.3.4.541) was re-examined (Fig. 91a) and it likely belongs to the present new species (Burton also labeled the present ZMA holotype with the same name in his unpublished manuscript on the Siboga sponges). The South Arabian specimen has mycalostyles of 1000 x 20 µm, three sizes of anisochelae, 90–100 µm, 40–44 µm and 20 µm, two sizes of sigmas 52–72 µm and 10–12 µm, and trichodragmas of 30–100 µm (measurements taken from Burton’s paper), thus almost identical to the present holotype. Topsent’s (1924) original description of M. (M.) massa var. oceanica concerns deep water material from the Azores and Cape Verde Islands. In a previous paper (Van Soest et al. 2014, pp. 62–65) we described similar specimens from the Cape Verde Islands, Mauritania and Morocco and concluded the var. oceanica fell within the variation of Mycale (Mycale) massa (Schmidt, 1862) s.l. There is a general similarity in spiculation with our new species, but the division in two discrete size categories of mycalostyles is not found in the Mediterranean-Atlantic specimens, and the shape of the sigma II is also different (asymmetrical, thin).

Burton (1959) reported Mycale (Mycale) murrayi (Ridley & Dendy, 1886) from the Gulf of Aden (11.895°N 51.22°E) at 73–220 m depth. We re-examined the specimen (BMNH 1936.3.4.589) (cf. Fig. 91b) and found it to be similar to our new species in most aspects, except the slightly larger size of sigma II). Provisionally, we reassign this record to our new species. Southeast Australian Mycale (Mycale) murrayi Ridley & Dendy, 1886 (type specimen BMNH 1887.5.2.155 from Port Jackson re-examined) appears indeed close to our new species in spiculation, although styles are smaller (528– 621.6 –714 x 13– 16.9 – 22 µm), occur in a single size category, and have a proper mycalostyle form with clearly developed head, but there are only few subtle differences in the remaining spicules: slimly built anisochelae I (76–83.3– 91 µm) occurring in rosettes, anisochelae II (30– 43.7 – 61 µm), spurless anisochelae III (18–22.2– 24 µm), sigmas I (37– 44.5 – 51 µm), sigmas II (22– 26.4 – 31 µm) and trichodragmas (63–75.6–93 x 4–11.2– 15 µm). A strong further difference with our (and also Burton’s specimen named M. massa var. oceanica), however, is the elaborate upright habitus of M. (M.) murrayi with characteristic groove pattern, reminding rather strongly of North Atlantic Mycale (Mycale) lingua (Bowerbank, 1866), unlike the present and Burton’s specimen.

On paper the new species is also similar to Mycale (Mycale) topsenti Burton, 1959 described from the same locality as the above mentioned South Arabian M. (M.) massa var. oceanica. We re-examined Burton’s holotype, BMNH 1936.3.4.542) and found his description accurate. The shape of the specimen (Fig. 91c) is more widespread, less compact, the mycalostyles (900 x 18 µm) with more distinct heads (not oxea-like at low magnification), and there is only a single category of sigmas, clearly larger (60–80 µm) than those of our material (see also below).

With New Zealand Mycale (Mycale) novaezealandiae Dendy, 1924 (type slide BMNH 1923.10.1.102, re-examined by us) the new species shares the presence of two sizes of mycalostyles (I 972– 1116 x 23–30 µm, and II 498–678 x 10–23 µm, and overall spicule complement: anisochelae I 81–92 µm, anisochelae II 36–43 µm, anisochelae III 24–30 µm, sigmas I 33–72 µm, sigmas II 14–19 µm, and trichodragmas 51–96 x 7–9 µm. The habitus of the type of M. (M.) novaezealandiae is club-shaped, so not unlike our present species, but the surface is corrugated-grooved, clearly different from M. (M.) sundaminorensis sp.nov. There are also compelling differences in the smaller mycalostyles, which are oxeote in M. (M.) novaezealandiae, in the shape of the anisochelae I (curved in M. (M.) novaezealandiae), and in the presence of peculiarly swollen sigmas II in M. (M.) sundaminorensis sp.nov.

The present new species shows considerable similarity to the above described Mycale (Mycale) grandoides sp.nov., as the locality (Nusa Tenggara at greater depth), the shape (compact cylindrical) and the overall spicule complement are virtually the same. There are two distinct differences: M. (M.) grandoides sp.nov. has only a single category of mycalostyles with length only about half of the longer category of M. (M.) sundaminorensis sp.nov., and M. (M.) grandoides sp.nov. has characteristic peculiarly compact anisochelae II, not found in the present species. We are confident the two belong to closely related but different species.

Additional species of Mycale (Mycale) from the region