Mycale (Grapelia) vaceleti Hajdu, 1995

Mycale (Grapelia) parasitica; Vacelet et al. 1976: 51, pl. 3 fig. c, text-fig. 31 (not: Carter 1885 = M. (G.) australis)

Mycale (Grapelia) vaceleti Hajdu, 1995: 91, figs 6.55–64.

Material examined. Schizotype fragment, ZMA Por. 10912 (taken from holotype MNHN D. VVL 149), Madagascar, Tuléar, Antseteky, Grand Récif, station 16c, depth 8–9 m, coll. P. Vasseur , 1969.

Summary description (after Hajdu 1995). Massively encrusting in coral cavities, with conulose surface. Oscules 2–3 mm in diameter. Color white in life and in alcohol. Size up to 4 x 2 x 1 cm. Consistency softly compressible, easily damaged. Choanosome cavernous, fibrous. Skeletal tracts up to 200 µm in diameter diminishing to 30–90 towards the periphery. Tangential ectosomal skeleton consist of thin spicule tracts and numerous rosettes of both anisochelae I and II. Spicules mycalostyles comparatively slim, 250–355 x 6–9 µm, anisochelae I with strongly curved shaft and unguiferous upper alae, pointed lower alae, 40–62 µm (arranged in rosettes of 135 µm diameter), anisochelae II similar in shape to anisochela I but much smaller, with three-pronged fused upper alae with serrated rim, with serrated lower alae, 15–19 µm (arranged in rosettes of 45 µm diameter), anisochelae III with spurred palmate shape, 11–15 µm, and rare sigmas 37–40 µm, found in the holotype, but not in the paratypes.

Distribution. Madagascar, 8–9 m depth.

Remarks. The present species from Madagascar is similar to M. (G.) carteri, but sizes of spicules differ substantially.

N.B. We have not been able to find the fragment cited above in the collections of the Naturalis Biodiversity Center in 2019, so data provided above are based on Hajdu 1995.

Key to the Mycale (Grapelia) species of the region

Remark. Hajdu’s (1995) (p. 95) key to the Mycale (Grapelia) species is here emended to leave out the Caribbean species, M. (G.) unguifera Hajdu et al., 1995 . We do include Mycale (Grapelia) australis despite the fact that its distribution falls outside our regional focus.

1 Anisochelae I palmate............................................................. Mycale (Grapelia) burtoni

- Anisochelae I unguiferate............................................................................... 2

2 Sigmas absent........................................................................................ 3

- Sigmas present....................................................................................... 5

3 Microsclere complement includes trichodragmas.................................... Mycale (Grapelia) trichophora

- No trichodragmas..................................................................................... 4

4 Habitus ramose; anisochelae II tend to be smaller than anisochelae III...................... Mycale (Grapelia) ancorina

- Habitus thickly massive; anisochelae III tend to be smaller than anisochelae II................ Mycale (Grapelia) australis

5 Anisochelae II compact, globular, free part of shaft barely present, small (± 10 µm)......... Mycale (Grapelia) menylloides

- Anisochelae II Ξ 10 µm, differently shaped................................................................. 6

6 Anisochelae bipocilla-like, rounded open with little difference in shape between upper and lower alae................................................................................................ Mycale (Grapelia) vansoesti

- Anisochelae II with long free part of the shaft, canopy-like upper alae and narrow-high lower alae.................... 7

7 Anisochelae I ± 50 µm, sigmas common............................................... Mycale (Grapelia) carteri

- Anisochelae I up to 78 µm, sigmas rare............................................... Mycale (Grapelia) vaceleti

Global diversity and distribution of the subgenus Mycale (Grapelia)

We queried the World Porifera Database (Van Soest et al. 2020) and added the above results from our Indo-West Pacific Mycale (Grapelia) study to arrive at the current tentative estimate of known accepted species, which numbers 9. Their distribution over the world oceans summarized as the numbers of species found in Marine Ecoregions of the World (cf. Spalding et al. 2007) is presented in Fig. 60. The subgenus is circumglobal in tropical warm-temperate waters, but is so far lacking from the tropical East Pacifc and East Atlantic (contrasting with Van Soest & Hajdu’s (2002) statement that the subgenus has ‘representatives in all tropical and warm-temperate regions of the world oceans’). Details are scarce as most species have been found only once.

Subgenus Mycale (Kerasemna) Pulitzer-Finali, 1982

Kerasemna Pulitzer-Finali, 1982a: 104; Richmond et al. 2011: 122, fig. on p. 123.

Mycale (Arenochalina); (in part) Van Soest & Hajdu 2002: 678, figs 5H–I.

Mycale (Mycale); sensu Calcinai et al. 2006: 197, 201 (not: Mycale (Mycale) sensu Van Soest & Hajdu 2002).

Amended definition. Thin-walled tubular or hollow-massively encrusting Mycale . Habitus consisting of a weblike outer surface supported by a reticulation of spicule tracts and skeletal support from branched coralline algae enclosing a hollow interior. The thin tissue between the supporting skeletal tracts and/or algal thallus is charged with single intercrossing megascleres and toxodragmas. Further microscleres, if present, are sigmas, anisochelae and trichodragmas.

Type species. Kerasemna tenuityla Pulitzer-Finali, 1982 (by monotypy) (= Mycale (Kerasemna) tenuityla).

Remarks. It is proposed here to re-erect the genus Kerasemna as a subgenus of the genus Mycale, to which it was previously assigned as a junior synonym of the subgenus Arenochalina (cf. Van Soest & Hajdu 2002).Although there are similarities with Arenochalina (such as spongin-encased spicule tracts, symbiosys with algae, and often scarceness of microscleres), the usually dense mass of toxodragmas, often arranged in loose concentrations (‘nested’ in Thiele’s (1903) description of one of the species, cf. below), and the web-like habitus make it clearly distinct from the known species of Arenochalina . A further difference with most species of Arenochalina is the absence of the production of copious slime when lifted out of the water, so characteristic of Arenochalina species.

We distinguish so far two species, the type species, M. (K.) tenuityla and M. (K.) humilis (Thiele, 1903) discernible by the absence (in M. (K.) tenuityla) or presence (in M. (K.) humilis) of anisochelae. Mycale (Mycale) vansoesti Calcinai et al., 2006 and Mycale (Mycale) corallina Calcinai et al., 2017 are also members of the subgenus, but these are clear junior synonyms of Mycale (K.) humilis, cf. below. Both distinguished Mycale (Kerasemna) species may possibly be members of a single variable species, but the evidence for this is currently lacking.

A possible Atlantic representative of the subgenus is Mycale incrustans Burton, 1932 (as Arenochalina), found attached to a buoy at Ascension Island (Burton 1932, p. 293). The specimen has a Mycale (Carmia) - type skeleton, consisting of wispy bundles of thin mycalostyles running parallel from the substratum to the surface. It lacks anisochelae and sigmas, but has ‘nested’ toxas as the only microscleres. The specimen needs to be re-examined, but on paper sounds rather similar to Mycale (Kerasemna) tenuityla .

Pulitzer-Finali (1982a) assigned several unrelated species to his genus Kerasemna, including Ophlitaspongia arbuscula Row, 1911 and O. horrida Row, 1911, both reassigned to Clathria by Hooper (1996). These are not members of the subgenus Mycale (Kerasemna) .