Mycale (Mycale) topsenti Burton 1959

Mycale (Mycale) topsenti Burton, 1959

Fig. 91c

Mycale (Mycale) topsenti Burton, 1959: 229, text-fig. 15.

Material examined. BMNH 1936.3.4.542, holotype, Oman, South Arabian coast, 21.8333°N 59.8667°E, depth 1046 m, coll. John Murray Exped. stat. 54, 3 November 1933.

Summary description. Small repent-ramose mass (Fig. 91c), surface bumpy, with several small oscules. Color yellow-brown (alcohol). Consistency softly compressible. Ectosomal skeleton a tangential layer of megascleres, carried by ascending choanosomal megasclere tracts forming brushes near the surface. Spicules: mycalostyles 900 x 18 µm, anisochelae I 88 µm, anisochelae II 40 µm, anisochelae III 20 µm, sigma I 60–80 µm, trichodragmas 60 µm.

Distribution. Oman, deep water.

Comment. We re-examined Burton’s holotype and found his description accurate. Compared to the closely related Mycale (Mycale) sundaminorensis sp.nov. (reported by Burton as Mycale (Mycale) massa var. oceanica from the same station), the shape of the specimen (cf. Fig. 91c) is more spreaded, less compact, the mycalostyles occur in a single category and with more distinct heads, and there is only a single category of sigmas, clearly larger than those of M. (M.) sundaminorensis sp.nov. (see also above).

Key to the Indo-West Pacific species of Mycale (Mycale)

Remark. The present key is state of the art, but suffers from several species not well known. Not all species treated below are certain members of Mycale (Mycale), and possibly some species may turn out to be synonyms.

1 Megascleres are variously shaped styles, subtylostyles and strongyles..................... Mycale (Mycale?) multisclera

- Megascleres exclusively stylote.......................................................................... 2

2 Megascleres in two distinct size categories................................ Mycale (Mycale) sundaminorensis sp.nov.

- No megasclere categories............................................................................... 3

3 Largest anisochelae> 100 µm........................................................................... 4

- Largest anisochelae ± 100 µm........................................................................... 6

4 Largest anisochelae> 200 µm..................................................... Mycale (Mycale) anisochela

- Largest anisochelae <200 µm........................................................................... 5

5 Live color white.......................................................... Mycale (Mycale) aff. grandis ‘white’

- Live color shades of red and orange................................................ Mycale (Mycale) grandis ‘red’

6 Toxas present...................................................... Mycale (Mycale) ernsthentscheli comb.nov.

- No toxas............................................................................................ 7

7 Sigmas absent........................................................................................ 8

- Sigmas present...................................................................................... 10

8 Trichodragmas present................................................................................. 9

- No trichodragmas................................................................ Mycale (Mycale) incurvata

9 Anisochelae III present, three categories of trichodragmas.......................... Mycale (Mycale) asigmata sp.nov.

- Anisochelae III absent, a single category of trichodragmas.............................. Mycale (Mycale) myriasclera

10 Raphides> 140 m present, but no trichodragmas......................................... Mycale (Mycale) digitata

- Trichodragmas present, but no single raphides of> 140 µm................................................... 11

11 Longest mycalostyles <350 µm................................................... Mycale (Mycale) meridionalis

- Longest mycalostyles> 400 µm......................................................................... 12

12 No anisochelae III, no sigmas II..................................................... Mycale (Mycale) gelatinosa

- Both anisochelae III and sigmas II present................................................................. 13

13 Distinct circular rosettes present........................................................................ 14

- Rosettes absent; groupings of anisochelae may be present but these are not circular............................... 15

14 Anisochelae I strongly curved, with short alae............................................ Mycale (Mycale) dendyi

- Anisochelae I ‘normal’ shaped............................................... Mycale (Mycale) grandoides sp.nov.

15 Mycalostyles up to at least 900 µm.................................................... Mycale (Mycale) topsenti

- Mycalostyles less than 700 µm.................................................... Mycale (Mycale) crassissima

Global diversity and distribution of the subgenus Mycale (Mycale)

We queried the World Porifera Database (Van Soest et al. 2020) and added the above results from our Indo-West Pacific Mycale (Mycale) study to arrive at the current tentative estimate of known accepted species, which numbers 63. 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. 92. The subgenus is widespread, with polar-, temperate- and warm water species. The highest species densities occur in Indonesia, the Western Indian Ocean and some Antarctic regions. This is likely a combined effect of collecting efforts and the non-monophyletic nature of the subgenus. Also, many cold water species are not well known. More revisions of species groups are necessary to arrive at meaningful distribution patterns.