Descriptions of the species
Suborder Mycalina Hajdu, Van Soest and Hooper, 1994
Family Mycalidae Lundbeck, 1905
Genus Mycale Gray, 1867
Subgenus Aegogropila Gray, 1867
Mycale (Aegogropila) magnitoxa sp. nov.
Material examined. Holotype: MNCN 1.01/631, Isla Lobos (Sinaloa), 23º13’27’’N, 106º28’01’’W, 7 m, 3.x.2003. Paratypes: BMNH 2010.11.01.1. LEB-ICML-UNAM-388, Punta Santiago (Colima), 19°05’41’’N, 104°25’22’’W, 2 m, 16.xi.2001. LEB-ICML-UNAM-632, Conchas Chinas (Jalisco), 20º35’16’’N, 105º14’42’’W, 5 m, 8.x.2002. LEB-ICML-UNAM-730, puente Maviri (Sinaloa), 25°34’55’’N, 109°06’52’’W, 2 m, 14.xi.2002. LEB-ICML-UNAM-824, antiguo corral del risco (Nayarit), 20°46’20’’N, 105°32’49’’W, 2 m, 11.vi.2003. LEB-ICML-UNAM-870, Chacala (Nayarit), 21°09’57’’N, 105°13’38’’W, 4 m, 12.vi.2003. LEB-ICML-UNAM-904, Isla Lobos (Sinaloa), 23º13’27’’N, 106º28’01’’W, 7 m, 3.x.2003. LEB-ICML-UNAM-934, Isla Hermano Sur (Sinaloa), 23º11’16’’N, 106º25’11’’W, 6 m, 22.x.2003. LEB-ICML-UNAM-953, Isla Hermano Norte (Sinaloa), 23º10’59’’N, 106º26’24’’W, 8 m, 24.x.2003. LEB-ICML-UNAM-1067, Isla El Crestón (Sinaloa), 23º11’02’’N, 106º25’37’’W, 9 m, 2.ix.2003. LEB-ICML-UNAM-1199, Submarino (Sinaloa), 23º09’59’’N, 106º25’05’’W, 18 m, 5.iii.2005. LEB-ICML-UNAM-1353, faro San Rafael (Baja California Sur), 24º17’53’’N, 110º20’43’’W, 9 m, 26.x.2006. LEB-ICML-UNAM-1494, Isla Venados (Sinaloa), 23º10’15’’N, 106º26’42’’W, 4 m, 26.iii.2007. LEB-ICML-UNAM-1539, Cabo San Lucas (Baja California Sur), 22º52’45’’N, 109º54’15’’W, 1.5 m, 25.x.2007. LEB-ICML-UNAM-1589, Las Monas, Isla Isabel (Nayarit), 21º50’59’’N, 105º52’46’’W, 6 m, 25.ix.2007. LEB-ICML-UNAM-1591, Isla Redonda, Islas Marietas (Nayarit), 20º42’04’’N, 105º34’31’’W, 5 m, 10.iv.2002.
Description. Thin sheet to thick cushion-shaped sponge, 0.4 to 1 cm in thickness, which may extend 12 cm or more on rock surface (Fig. 3A). Alive the sponge is light orange to light red. It is light brown in alcohol. The surface is smooth, and pierced by small pores 200-500 μm in diameter, giving it a punctate appearance clearly visible through the transparent dermal membrane, which is detachable in parts. The pores bear many sieve-like ostia, 80 to 110 μm in diameter. The surface in situ also shows a clear vein pattern of superficial canals, 0.5 to 3 mm in diameter, that lead to slightly elevated small contracted oscules, 2-5 mm in diameter. Consistency is soft, but firm upon preservation in alcohol. Alive the sponge exudes some slime.
Spicules. The species bears mycalostyles as megascleres, and three types of microscleres: anisochelae, sigmas and very long toxas (Table 1). The mycalostyles are straight or slightly curved, sharp and thicker towards the middle of the spicule (Fig. 4A), and with a more or less pronounced head that varies between individuals (Fig. 4B). Measurements: 177-290 × 2-7 μm. Head diameter: from 2.5 to 7 μm.
Table 1. Distribution and comparative data for the dimensions of spicules (in μm) of Mycale (Aegogropila) magnitoxa sp. nov. specimens. Values in parentheses are means.
Anisochelae of three sizes (Fig. 4D-F). I) 28-42 μm in length, with a palmate head that is ca. 62% of total length of the spicule. This category forms rosettes in the ectosome. II) 18.7-25 μm in length, with palmate head ca. 53% of total length of the spicule. III) 11.5-15 μm, palmate head ca. 56% of total length of the spicule. Sigmas are ‘C’ shaped in two size classes. The larger are numerous, robust, 70-120 × 6-8 μm (Fig. 4G). Smaller and fine sigmas are 25-35 × 1.3 μm, thinly scattered and very slender, and consequently sometimes hard to find. They were not found in some specimens.
Toxas of two types (Fig. 4C): the longest with small central bend, 187-352.5 × 2-5 μm. The shorter is deeply curved 60-157.5 × 1.3 μm.
Skeleton. Plumoreticulate. The ectosomal skeleton is a tangential, triangular or polygonal meshed reticulation (45 a 60 μm wide) of multispicular fibers of mycalostyles (20 to 60 μm in thickness) (Fig. 4H). In some areas it is confused, and with single scattered megascleres. It is easily detachable. Anisochelae I form rosettes in the ectosome. The choanosomal skeleton consists of plumose bundles of megascleres (80-110 μm) ending at the surface (Fig. 4I). Spongin reinforces the skeletal fibres to a varying degree. Microscleres scattered throughout choanosome.
Distribution and habitat. Sea of Cortés (Mexican Pacific Ocean). Baja California Sur, Sinaloa, Nayarit, Jalisco and Colima, on rocks, from the intertidal to 18 m depth (Fig. 1).
Etymology. The proposed name magnitoxa alludes to the large size of their toxas.
Taxonomic remarks. Only two species of Mycale (Aegogropila) are known in the Northeastern Pacific: M. (A.) adhaerens (Lambe, 1893) (see next species) and M. (A.) bamfieldensis Reiswig and Kaiser, 1989. Nevertheless, these two species are clearly different from M. (A.) magnitoxa sp. nov.; the first one has no toxas, and M. (A.) bamfieldense differs from the new species by possessing micracanthoxeas and by having much smaller toxas (19-70 μm).
In the West Atlantic and Caribbean there are three species of the subgenus Aegogropila with long toxas; M. (A.) arndti Van Soest 1984 from the Caribbean, which has sigmas in three categories, and toxas up to 85 μm long (Hajdu and Rützler, 1998), M. (A.) escarlatei Hadju et al., 1995 from the Western Tropical Pacific, with microancanthoxas and toxas in two categories up to 140 μm long (Hadju et al., 1995), and M. (A.) lilianae which posses the longest toxas (300 μm) but clearly differs from M. (A.) magnitoxa sp. nov. by the presence of micracanthoxeas.
The closest NE Atlantic species to M. (A.) magnitoxa is M. (A.) contarenii (Martens, 1824). M. (A.) contarenii is a yellow, yellowish green, ochrous or orange-green massive, semi-encrusting and occasionally lobate sponge, with a surface typically covered by small conules (Van Soest and Hajdu, 2002), while M. (A.) magnitoxa sp. nov., is a red, or light red encrusting sponge with a smooth even surface. This morphological overview distinguishes the two species easily, but these species also differ in their spicules. Toxas are much longer (77 μm to 350 μm) in M. (A.) magnitoxa sp. nov. than in M. (A.) contarenii (70 μm), and the toxas of M. (A.) contarenii have a widely extended central bend. The larger sigmas of M. (A.) contarenii are generally shorter than 70 μm, while M. (A.) magnitoxa sp. nov. presents sigmas usually longer than 100 μm.