Mycale (Aegogropila) gravelyi Burton 1937, comb.nov.
Creators: name: Van, Rob W. M.
name: Aryasari, Ratih
name: De, Nicole J.
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Animalia
Porifera
Demospongiae
Poecilosclerida
Mycalidae
Mycale
Mycale gravelyi

description: Mycale (Aegogropila) gravelyi Burton, 1937 comb.nov.
Figs 2 a–e, 3a–f
Mycale gravelyi Burton, 1937: 24, pl. II fig. 16; Vacelet & Vasseur 1965: 102, pl. VII, fig. 25; Vacelet & Vasseur 1971: 86.
? Mycale rotalis; Burton 1926: 80 (listed for Suez Canal, Red Sea, without description) (not: Bowerbank, 1874)
? Mycale pachysigmata Pulitzer-Finali, 1996: 117, fig. 16.
Mycale (Mycale) gravelyi; Minh-Quang Thai: 114 (listed only).
Material examined. ZMA Por. 07864a, Indonesia, Maluku, Ambon,Ambon Bay, Hative Besar, 3.6833°S 128.1333°E, depth 1–4 m, coll. R. W.M. van Soest, snorkeling, Indonesian-Dutch Snellius II Expedition stat. 002, field number 002 / II/18, 6 September 1984 (color grey; grainy interior); ZMA Por. 07884, Indonesia, Maluku, Ambon, Ambon Bay, near Tawiri, 3.7°S 128.1167°E, depth 1–4 m, coll. J. Brouns, snorkeling, Indonesian-Dutch Snellius II Expedition stat. 010, field number 010 / II/08, 6 September 1984 (color grey; grainy interior); ZMA Por. 08199a, Indonesia, Maluku, Ambon, Ambon Bay, near Eri, 3.75°S 128.1333°E, depth 3–7 m, coll. R. W.M. van Soest, SCUBA, Indonesian-Dutch Snellius II Expedition stat. 007, field number 007 / III/33, 3 September 1984 (color grey; on coral clump; grainy); RMNH Por. 11765, Taiwan, Lanyu Island, Iraraley Bay, 22.0813°N 121.5226°E, depth 3 m, coll. N.J. de Voogd, SCUBA, field number KUE141A (encrusting on an Agelas sp.; slide only).
Description. The three specimens from Ambon Bay are thinly encrusting on dead corals and among the base of living corals, forming patches up to several cms long and wide (cf. Fig 2a, arrows), thickness between 0.5 and 1.5 mm. The specimen from KUE grew on the surface of a sponge (Agelas sp.) collected from a cave. Consistency firm. Surface smooth with faint canal patterns visible in preserved condition. Color in life reported as greyish or light reddish, in alcohol it becomes light beige. The tissue between the skeletal tracts of our specimens is grainy in outlook and consists of unidentified polyangular particles of about 2–5 µm in diameter.
Skeleton. The tangential ectosomal skeleton (Figs 3f,f 1) is formed by robust intercrossing spicule tracts of 30–120 µm in diameter, in cross section consisting of 3–10 aligned spicules. The ectosomal tracts form triangular meshes, with mesh sizes between the tracts variable, approximately 250–450 µm wide. Rosettes of anisochelae 105–125 µm in diameter are common between the tracts. The choanosomal skeleton consists of thick plumose tracts fanning out peripherally, carrying the ectosomal skeleton. Tracts are 100–200 µm in thickness, formed by up to 15 spicules in cross section, and they are positioned at approximately 500–600 µm distance from each other. ZMA Por. 07684 has overall a slightly less robust skeleton compared to ZMA Por. 08199a.
Spicules (Figs 2 b–e, 3a–e). Mycalostyles, three categories of anisochelae, and one of sigmas.
Mycalostyles (Figs 2b,b 1, 3a,a 1), fusiform, with elongate head and clearly constricted neck, gradually but somewhat abruptly pointed, 524– 548.4 –616 x 11– 16.6 – 22 µm.
Anisochelae I (Figs 2c, 3b), robust, with alae all well-developed and the shaft free for about 1/3 of the spicule length, with slightly outwardly curved median alae, 38– 47.6 – 57 µm.
Anisochelae II (Fig. 2d,d 1, 3c), narrow-shaped, with upper alae longer than half the length of the spicule, often 2/ 3 in length, with lower alae relatively small and the free part of the shaft short, 21– 23.2 – 25 µm (in both specimens approximately the same size).
Anisochelae III (Figs 2e,e 1, 3d), narrow and thin, with small lateral alae, looking undeveloped, but they are similar in both specimens, 12– 14.4 – 20 µm.
Sigmas I (Figs 2f, 3e), robust, with unequally curved apices, occasionally S-shaped, similar in both specimens, 69– 80.9 – 93 µm, thickness 3.5– 4.4 – 5.5 µm.
Distribution and ecology. Indonesia, Ambon Bay, depth 1–7 m, on corals, Taiwan, Lanyu, in cave, encrusting an Agelas specimen; Krusadai Island, Gulf of Manaar, India (no further data); Tuléar, Madagascar, whitish, among corals and in shallow reef caves, depth 1– 2 m.
Remarks. This species, named after the naturalist F.H. Gravely, is only rarely reported and remains insufficiently known. The identification of our specimens must be considered tentative, because Burton’s description of the type (BMNH 1931.11.28.178) is ambiguous, as there is no information on the dermal skeleton and spicule data contrast between description and illustration. Vacelet & Vasseur (1965, 1971) cited occurrence of this species in Madagascar, and described the ectosomal skeleton as possessing a ‘réseau régulier de fibres de styles’, which we interpret as conforming to that of the subgenus Aegogropila. Thus our identification with Burton’s species rests on Vacelet & Vasseur’s subsequent description. Still, the spicule size information of the type conforms closely with that from our specimens: styles 510 x 14 µm, anisochelae I (in rosettes) 35–45 µm, anisochelae II/III 14–24 µm (not separated by Burton), sigmas 70 µm. In Burton’s drawing of the spicules, there is a difference with the description, as he pictures two sizes of sigmas (not mentioned in the description) and his two anisochelae drawings are not clearly different in shape and size from each other and we classify them both as anisochelae I. We assume that the drawing of the small sigma must be attributed to the smallest anisochela category (III) as this appears with the barely developed alae almost like a sigma at the magnification used by Burton (500 x). Tissue of the type was noted to be charged with refringent granules, which were also present in our specimens (and assumed to be evidence of mucus production). Vacelet & Vasseur (l.c.) report similar spicule sizes as our specimens: styles 400–500 µm, anisochelae I (rosettes) 45 µm, anisochelae II 18–24 µm, anisochelae III 10–12 µm, sigmas I 75–85 µm, but they make no mention of grainy tissue.
Burton (1926: 80) listed Mycale rotalis (Bowerbank, 1874) as occurring in the Suez Canal, but he failed to provide a description. Unless this Atlantic-Mediterranean species has performed a reversed Lessepsian migration, this record possibly concerns a member of the present species. However, re-examination of the specimen is necessary.
A species close to, and possibly a junior synonym, is Mycale (Aegogropila) pachysigmata Pulitzer-Finali, 1996 from Papua New Guinea. The overall data of the shape and the sizes of the spicules match the present material, but there are two distinct differences, the sigmas may be as thick as up to 14 µm, and the ectosomal spicule tracts are up to 1 mm in diameter, both sizes clearly in excess of those of the above discussed likely members of M. (Ae.) gravelyi.
Mycale (Aegogropila) meridionalis sensu Samaai & Gibbons 2005 (not: Lévi 1963) from the Atlantic coast of South Africa appears similar to the present species, but the sigmas of the South African specimen are clearly smaller, only 23–28 µm and the anisochelae I have a curved shape, unlike those of M. (Ae.) gravelyi.
With its narrow-shaped anisochela II, Mycale (Aegogropila) gravelyi is obviously close to M. (Ae.) orientalis (Topsent, 1897) and M. (Ae.) sulevoidea (Sollas, 1902), but differs from these species in having larger styles, lacking sigmas II and toxas. We searched exhaustively for these microscleres and are certain they were absent in our four specimens.
It is possible that Esperella porosa Ridley & Dendy, 1886: 338; Ridley & Dendy 1887: 68, pl.XV figs 6,9,17, pl. XVI fig. 5 from Southeast Australia, now reassigned as Mycale (Aegogropila) porosa (cf. World Porifera Database, Van Soest et al. 2020) is a senior synonym of the present species. The general description fits, but Ridley & Dendy’s mycalostyles are only 380 x 16 µm, only a single anisochela is reported and sigmas are much larger, 160 x 8.5 µm, than those of the present specimens. The species was only reported outside our regional limits and is here further ignored, but comparison of the two types is recommended.
description: Published as part of Van, Rob W. M., Aryasari, Ratih & De, Nicole J., 2021, Mycale species of the tropical Indo-West Pacific (Porifera, Demospongiae, Poecilosclerida), pp. 1-212 in Zootaxa 4912 (1) on pages 10-13, DOI: 10.11646/zootaxa.4912.1.1, http://zenodo.org/record/4450930