Subgenus Paresperella Dendy, 1905
Mycale (Paresperella) psila (De Laubenfels, 1930)
Fig. 10. Images of spicules and skeletal arrangement of Mycale (Paresperella) psila (de Laubenfels, 1930). A, (LM) Mycalostyles; B, (SEM) Mycalostyles’ ends detail; C, (SEM) Anisochelae I; D, (SEM) Anisochelae II; E, (LM) Toxa; F, (SEM) Sigmas; G, (SEM) Detail of serrated edges. H, Drawing of tangential view of ectosomal structure; I, Drawing of transversal view of choanosomal structure.
Paresperella psila.- De Laubenfels, 1930: 36; De Laubenfels, 1932: 70
Esperella serratohamata.- Lambe, 1895; 130 [not Esperia serratohamata Carter, 1880]
Mycale psila.- Bakus, 1966: 459; Bakus and Green, 1987
Material examined. LEB-ICML-UNAM-329, Isla Lobos (Sinaloa), 23º13’49’’N, 106º27’43’’W, 6 m, 20.iii. 2001. LEB-ICML-UNAM-853, Majahuita (Jalisco), 20°29’06’’N, 105° 35’03’’W, 10 m, 08.vi.2003. LEB-ICML-UNAM-896, Isla el Crestón (Sinaloa), 23º11’02’’N, 106º25’37’’W, 7 m, 12.ix.2003. LEB-ICML-UNAM- 1118, Punta Pinta, Pto. Peñasco (Sonora), 31º20’14’’N, 96º05’20’’W 4 m, 04.iii.2005.
Description. Specimens of this species are thinly to thickly encrusting up to 2.5 mm thick. Live colors range from light yellow to almost white in some specimens, and turn pale brown in alcohol. Maximum substratum coverage of 9 cm long × 5 cm wide. Surface is smooth, but feels slightly hispid. The species presents numerous projections, 2.5 to 5.5 mm high and 1.3 to 1.8 mm thick. The consistency is soft but the projections are firm. Oscules are frequently oval, 0.4 to 1.2 mm in diameter. The body of the sponge and the surface harbor sand, and small fragments of shells.
Spicules. Megascleres are mycalostyles, and microscleres are anisochelae in two categories, toxas, and the typical serrated sigmas of the subgenus in two size classes.
Mycalostyles with shaft that is usually curved, tapering gradually to a sharp point (Fig. 10A, B), 245-325 μm long × 2.5-10 μm wide. With elliptical heads 2.5-7.5 μm in diameter, sometimes weakly mucronate.
Anisochelae I) with head about ca 55% of total spicule length (Fig. 10C). Size: 27-35 μm long.
Anisochelae II) with palmate head ca 56% of total length of the spicule (Fig. 10D). Size: 11-14 μm long.
Toxas are slender, central curve often marked, lateral curves often gentle, gradually tapering to sharp endings (Fig. 10E). Size: 42-63 μm long.
Sigmas with serrated edges (Fig. 10F, G), ‘S-C’ shaped, in two categories. Size category I: 130 to 188 μm long. Size category II: 37 to 60 μm long.
Skeleton.The ectosomal skeleton is made of a tangential reticulation of paucispicular (1-5 spicules), or pluriespicular tracts of mycalostyles (11-18 spicules). Meshes formed by the reticulation are 60 to 200 μm wide. Anisochelae-I are mostly organized in rosettes (Fig. 10H). The choanosomal skeleton is made of ascending tracts of mycalostyles, 150 μm thick (Fig. 10I). Tracts branch towards the ectosome where they diverge in paucispicular tufts 40-100 μm thick that support and slightly pierce the ectosomal reticulum and surface peel.
Distribution and habitat. Northeast Pacific Ocean: Vancouver (Canada) (as Esperella serratohamata Lambe, 1894), San Juan (Washington) (Bakus, 1966), California (De Laubenfels, 1930, 1932; Bakus and Green, 1987), and México (Sonora, Sinaloa, Jalisco and Guerrero) (Fig. 1), on sublittoral rocks.
Remarks. See Bakus (1966).