Mycale (Arenochalina) regularis Wilson, 1925

Van, Rob W. M., Aryasari, Ratih & De, Nicole J., 2021, Mycale species of the tropical Indo-West Pacific (Porifera, Demospongiae, Poecilosclerida), Zootaxa 4912 (1), pp. 1-212 : 42-47

Mycale (Arenochalina) regularis Wilson, 1925

Figs 24 a–e, 25a–e, 26a–c, 27a–f, 28

Mycale euplectellioides var. regularis Wilson, 1925: 427 .

Mycale euplectellioides ; Salmoun et al. 2007: 153 (not: Row, 1911).

Material examined. USNM 21273 ( Fig. 22a ), holotype of Esperella euplectelliodes var. regularis , Philippine Islands, Sulu Archipelago, Jolo Island, Belan Point , 6.7222°N 120.989°E, depth 39.6 m, Albatross Expedition stat. 5136, 14 February 1908 .

ZMA Por. 02906, Indonesia, Papua, Aru Islands, Pearl Banks , anchorage off Pulau Jedan , 5.4134°S 134.6677°E, depth 13 m , trawl/dredge/divers, Siboga Expedition stat. 273, field nr. SE 1604I, 23 December 1899; ZMA Por. 08883, Indonesia, Sulawesi, SE, Take Bone Rate NE, S of Tarupa Kecil, 6.5°S 121.1333°E, depth 10–15 m , SCUBA, coll. R. W.M. van Soest, Indonesian-Dutch Snellius II Expedition stat. 139, field nr 139 / IV/02 , 25 September 1984 (blue) ; ZMA Por. 14515, Indonesia, North Sulawesi, Bunaken , S of Tilisei Island, 1.7931°N 125.0568°E, depth 15 m , SCUBA, coll. B.W. Hoeksema, SYMBIOSPONGE Project, field nr. 98/NS/MAY06/BH/068, 6 May 1998 (iridescent blue) ; RMNH Por. 2147, Indonesia, Bali, Tulamben Beach, Liberty Wreck , 8.2739°S 115.5911°E, depth 18 m , SCUBA, coll. N.J. de Voogd, Bali-Lombok Strait Expedition 2001, field nr. BAL.21/100401/112, 11 April 2001 (blue) ; RMNH Por. 2155, Indonesia, Sulawesi, S, Tanjung Bira , 5.6623°S 120.4734°E, depth 25 m , coll. N.J. de Voogd, station BIR03, field nr. UP / BR/040302 /222, 4 March 2002 ; RMNH Por. 2160, Indonesia, Sulawesi, S, Tanjung Bira , 5.6623°S 120.4734°E, depth 42 m , coll. N.J. de Voogd, station BIR02, field nr. UP / BR/090202 /286, 9 February 2002 (blue) ; RMNH Por. 3928, Indonesia, West Papua, Raja Ampat Islands, SE Gam, Mike’s Point , 5.1687°S 130.6733°E, 20–25 m , SCUBA, coll. W. Renema, 20 November 2007; Specimen not retrieved, not registered: Papua New Guinea, coll. M.C. Díaz, field nr. 92579 (whitish) .

Description ( Figs 24 a–b, 25a–b, 26a, 27a,e–f). Hollow, cylindrical tube or group of tubes connected at the base ( Figs 24a , 25a , 27 e–f). Shape tending to become expanded or even flaring in the larger specimens ( Fig. 24a ), but smaller specimens may be finger-shaped ( Fig. 27a ) or massive, not forming clear tubes and then resembling M. (Ar.) imperfecta (cf. above). Size variable, up to 20 cm or more in height, mouth diameter up to 10 cm in the larger specimens, narrower in smaller specimens. Mouth of the tubes provided with thin organic rim ( Fig. 24a ), which disappears in preservation. Surface provided with grouping of blunt spines, or bluntly conulose, due to protruding fibres, becoming progressively macerated in preservation. Color iridescent pale blueish ( Figs 24a , 25a ) or (greyish) white ( Figs 27 e–f), becoming light beige or dirty white in preservation ( Figs 24b , 25b , 26a , 27a ). Consistency cartilaginous. Copious mucus production when lifted out of the water.

Skeleton ( Figs 26b,b 1–c ). Framework of spongin-enforced spicule tracts, with main tracts 300–700 µm in diameter interconnected—frequently at right angles—by secondary tracts of 150–250 µm diameter. Both fibre types are filled with dense masses of thin mycalostyles, usually closely aligned, but especially at the connecting region they may be strewn in all directions. Near the surface, thinner tracts may branch off and fan out into the organic ectosome. Loose mycalostyles may be strewn tangentially in the mucous tissue inbetween the protruding endings of the main fibres. Specimens not immediately put into alcohol may loose much of their organic tissues and also loose the bulk of the microscleres. This may cause difficulties in identifying the spicule complement because the presence, absence or rarity of microscleres may then vary in individual sponge specimens. In well-preserved specimens, the microscleres are usually present in abundance, and anisochelae are typically gathered in rosettes of 60–70 µm diameter ( Fig. 26c ).

Spicules ( Figs 24 c–e, 25c–e, 27b–d). Mycalostyles, a single size of anisochelae, a single size of sigmas; microscleres are usually common.

Mycalostyles ( Figs 24c,c 1 , 25c,c 1 , 27b,b 1 ), thin, with elongate heads, shaft equidiametrical, often with blunt ending, 213– 283.9 –318 x 2– 4.3 – 6.5 µm; type specimen: 279– 305.3 –315 x 5– 5.8 – 6.5 µm.

Anisochelae ( Figs 24d , 25d , 26e , 27c ), narrow, but with both upper and lower alae well-developed, free shaft about one third of the length of the spicule, 23– 30.1 – 41 µm; type specimen: 28– 32.1 – 36 µm.

Sigmas ( Figs 24e , 25e , 27d ), thin, widely curved to almost circular, with ends tending to turn inward, 51– 70.2 – 94 µm; type specimen: 74– 83.8 – 94 µm.

Distribution and ecology ( Fig. 28 ). Philippines, Indonesia, Papua New Guinea, on deeper parts of the reefs and rocks, from 10 m down to 42 m depth.

Remarks. Together with M. (Ar.) euplectellioides , the present species is distinct from the other Mycale (Arenochalina) species in the region by forming a large cylindrical shape. Differences with M. (Ar.) euplectellioides are mainly the surface color, of whitish to pale blue color, against the red color of that species. It is close in additional characters to Mycale (Aenochalina) imperfecta Baer, 1906 (cf. above), sharing rosettes of anisochelae and semicircular sigmas with incurved endings. As a further distinction apart from shape, the skeletal fibres are usually more robust, up to 700 µm in diameter. In the Caribbean, Mycale (Arenochalina) laxissima ( Duchassaing & Michelotti, 1864) occurs in a large range of shapes (tubular, massive or encrusting), so it may be argued that the differences in shape between M. (Ar.) regularis (and indeed also M. (Ar.) euplectellioides ) and M. (Ar.) imperfecta is infraspecific variability within a single variable species. For the time being, we emphasize here the differences (see also below), and keep the two as separate species.

The syntype of Mycale (Arenochalina) regularis Wilson, 1925 (as a variety of M. euplectellioides ), USNM 21273 (cf. Fig. 26a ), was re-examined and we conclude that the alleged differences with M. (Ar.) euplectellioides noted by Wilson are maybe not all of taxonomic significance. Wilson cites fibre diameter differences between main fibres (up to 850 µm in diameter) and connecting fibres, and subdermally thinner fibres, and a more regular reticulation, but these features are quite variable in our specimens. In situ photos of the two (e.g. M. (Ar.) euplectellioides (RMNH Por. 9628) and M. (Ar.) regularis (ZMA Por. 14515) show that the two differ clearly in color and more subtly in surface features, the former being more sharply conulose, the latter more bluntly conulose. In preservation, these differences largely disappear. A further indication that the two are closely related but different species is the distribution known so far, with M. (Ar.) euplectellioides confined to the Arabic peninsula and M. (Ar.) regularis to the Indo-Malayan archipelagoes ( Fig. 28 ).

Figures

FIGURE 1. A. Numbers of available specimens for the present study from the collections of the Naturalis Biodiversity Center distributed over Indo-West Pacific Marine Ecoregions (MEOWS, cf. Spalding et al. 2007). B. Ditto for type specimens and additional specimens from other institutions consulted for this study.

FIGURE 22. Mycale (Arenochalina) imperfecta Baer, 1906, ZMA Por. 01611 from Indonesia, a, preserved habitus (scale bar = 1 cm), a1, detailed view of surface crust, b–d, SEM images of the spicules, b, mycalostyle, b1, details of mycalostyle, c, anisochelae, d, sigmas.

FIGURE 24. Mycale (Arenochalina) regularis Wilson, 1925, ZMA Por. 14515, a, habitus in situ in Indonesia (photo B.W. Hoeksema), b, preserved fragment (scale bar 1 cm), c–e, SEM images of spicules, c, mycalostyle, c1 details of mycalostyle, d, anisochela, e, sigma.

FIGURE 25. Mycale (Arenochalina) regularis Wilson, 1925, ZMA Por. 08883 from Indonesia, a, habitus on deck, b, preserved habitus (scale bar = 1 cm), c–e, SEM images of spicules, c, mycalostyle, c1, details of mycalostyle, d, anisochela, e, sigma.

FIGURE 26. Mycale (Arenochalina) regularis Wilson, 1925, a, syntype of Mycale euplectellioides var. regularis Wilson, 1925, USNM 21273 (photo L.E. Becking), b,b1, light microscopic views of choanosomal skeleton showing thick spicule-filled fibre tracts, c, ZMA Por. 14515 from Indonesia, light microscopic view of rosette of anisochelae.

FIGURE 27. Mycale (Arenochalina) regularis Wilson, 1925, a–d, ZMA Por. 02906 from Indonesia, a, preserved fragment (scale bar = 1 cm), b–d, SEM images of the spicules, b, mycalostyle, b1, details of mycalostyle, c, anisochela, d, sigma, e, habitus in situ of RMNH Por. 3928 from Rajah Ampat, (West) Papua (photo W. Renema), f, habitus in situ of unregistered specimen from Papua New Guinea (photo M.C. Díaz).

FIGURE 28. Mycale (Arenochalina) euplectellioides Row, 1911 and M. (Ar.) regularis Wilson, 1925, approximate distribution of specimens studied (squares) and literature records (dots); blue = M. (Ar.) euplectellioides, red = M. (Ar.) regularis. Squares and dots may represent several close collecting localities.