Aplysina airapii, Gómez & González-Acosta & Sánchez-Ortíz & Hoffman & Hernández-Guerrero, 2018

Gómez, Patricia, González-Acosta, Bárbara, Sánchez-Ortíz, Carlos, Hoffman, Zvi & Hernández-Guerrero, Claudia J., 2018, Amended definitions for Aplysinidae and Aplysina (Porifera, Demospongiae, Verongiida): on three new species from a remarkable population in the Gulf of California, Zootaxa 4455 (2), pp. 322-342 : 330-332

Aplysina airapii sp. nov.

( Figs. 3 , 5 )

Material examined. Holotype CNPGG‒1396 El Gallo, 24°27’54.76”N 110°23’14.75”W, 16/XII/2011, 5 m. Paratypes: USNM‒1283360 Punta Norte, Cerralvo Is., 24°22’31.05”N 109°55’57.04”W, 17/XII/2011. CNPGG‒ 1336 Punta Norte, Cerralvo Is., 24°22’31.05”N 109°55’57.04”W, 17/XII/2011, 10 m. CNPGG‒1341, 1342 El Gallo, 14/XII/1990.

Additional material examined. Paratype USNM-21501 Verongia thiona de Laubenfels, 1930 Laguna Beach , California, USA. 14/III/1926, as abundant.

Description. Massive sponge, with short, conical, tubular processes on top, consisting of up to 16 low tubes. The entire sponge is about 5.5 cm wide, 21.7 cm long, and 10.5 cm in height ( Fig. 3 C-D). Each tube with an apical pseudoscule up to 2 mm in diameter; some of these bear an elevated diaphragm, which contracts so tightly that it cannot be seen in some tubes. Small samples CNPGG‒1336, 1341, 1342, (2 cm wide, 4 cm long and 2.3 cm in height), are probably juvenile with the same habit and skeletal arrangement as for the larger specimens. The color when alive is pale yellow with purple tinges at the top of the tube, turning black in alcohol. The consistency is firm, slightly compressible. The surface is regularly conulose, although the conules are not clearly seen when alive; they are <1.0 to 1.2 mm in height, and 1‒3 mm apart in preserved material.

Skeleton. Anastomosed hexagonal meshes form a uniplanar layer delineating the atrium wall along the tube. From this uniplanar mesh, arise a succession of dendritic fibers at regular intervals going ortogonal to the surface. These fibers run along the tube wall without anastomoses. Atrium fibers are stratified 90‒350 µm in diameter with reddish amber bark, forming meshes 468‒1610 µm wide with amber-colored pith 60‒180 µm in diameter, on average three-quarters of the fiber diameter. Dendritic fibers are thinner than that of the atrium, 110‒160 µm in diameter, with a lighter-colored bark and a black pith 80‒100 µm in diameter with unusual nodules on average, 80 % of the fiber diameter ( Fig. 5 ).

Ecology. A. airapii sp. nov. also occurs on rocky reef substratum (boulders, walls and small caves) from 5 to 15 m depth. It is common on both exposed and sheltered shores at Espiritu Santo Is. The opistobranch mollusc Tylodina fungina Gabb, 1865 is again a predator.

Distribution. A. airapii occurs around Espiritu Santo Island (El Gallo Is., Los Islotes Is., Punta Lobos, specimens from the last two locations were only observed), and Cerralvo Island (Punta Norte), Baja California Sur in La Paz Bay.

Etymology. The species name Airapi is derived from an indigenous designation for the locality in Baja California Sur (from La Paz to Loreto) inhabited by pre-Hispanic settlers called Guaycuras, who encountered the Spaniards.

Remarks. The unique skeletal arrangement, dimensions of skeletal components, and external morphology, render Aplysina airapii sp. nov. readily distinguishable from any other Eastern Pacific Aplysina . A uniplanar reticulation at the atrium walls, from which dendritic fibers originate and run orthogonally to the surface, is an arrangement not previously recorded in any aplysinid specimen, not even as a tendency. Aplysina encarnacionae sp. nov. (described above) is similar to A. airapii sp. nov. but has a higher proportion of polygonal anastomosed fibers and longer dendritic ones, which sometimes anastomose. In addition, the overall shape of the two species is quite different. The species that most closely resembles A. airapii sp. nov. in external morphology is Aplysina sinuscaliforniensis sp. nov. (described below) which is massive with tubular processes, and similar color in vivo, i.e. pale yellow with purple tinges. Both species occur in sympatry and can be misidentified in the field. Therefore skeletal slides are necessary to ascertain their identity, through the traditional anastomosed skeleton in A. sinuscaliforniensis sp. nov., devoid of dendritic fibers, and smaller dimensions of skeletal elements when contrasted to those in A. airapii sp. nov.

The possession of dendritic fibers in Verongiida was previously more a trait of Pseudoceratinidae and Aplysinellidae that lack anastomosed fibers. The paratype of Verongia thiona (transferred to Aiolochroia ; Van Soest et al. 2017) bears dendritic fibers and was compared with the new species. The specimen shows characters diverging both from the Aiolochroia pattern, as well as from A. airapii sp. nov. This is a gross encrustation, with a typical conulose surface ( Fig. 9 ), with different skeletal arrangement. “ Verongia ” thiona has an anastomosed polygonal skeleton with unevenly and short dendritic fibers ( Fig. 9 C, D ). De Laubenfels (1932) refers to this trait as "Endosomal structure ... by rather scattered fibers in reticulation… with a very irregular mesh size which averages more than 1 mm.” In addition, fiber measurements of de Laubenfels are 80‒150 µm, and pith diameter of 50‒110 µm. These skeletal elements were re-measured here on freshly prepared sections, exhibiting fiber diameters of 60‒110 µm, pith diameter of 20‒80 µm, and forming meshes of 500‒830 µm. A skeletal pattern far from being the scheme of the present new species, further differing by its general habit.

Morphologic studies on the paratype of “ V”. thiona , and comparison with those of Aiolochroia genus, proved that “ V”. thiona shares more features with Aplysina than with any other genera in Verongiida . Aiolochroia crassa in particular, exhibits a dendritic pattern and some reticulated areas in the subsurface region (occasionally in deeper areas too); it has erratic fibers of large diameter surpassing 500 µm, and has rounded distinctive conules (e.g. Bergquist & Cook, 2002; Hajdu et al. 2011). The above stated morphologic features are not close to those seen in “ V”. thiona , nor to those in A. airapii sp. nov. The new species has a different dendritic structural arrangement; dendritic fibers have their origin on the uniplanar anastomosed framework, only present along the atrium wall. Besides, its conules are conical instead of rounded, it also has a unique color alive, not a variety of colors as A. crassa . The entire scenario leads to conclude that V. thiona belongs to Aplysina with features proper of the genus.

Figures

FIGURE 3. A‒B. Aplysina encarnacionae sp. nov., C‒D. Aplysina airapii sp. nov. at Espiritu Santo Island, BCS, Mexico. Underwater photographs in vivo.

FIGURE 5. Aplysina airapii sp. nov., A. General structure of the skeletal assemblage, uniplanar layer of fibers delineating the atrium wall, and dendritic fibers conforming the tube wall. B. Detail of anastomosed fiber. C. Detail of dendritic fibers.

FIGURE 9. Ƒerongia thiona de Laubenfels, 1930 (=Aplysina thiona), A‒B. Paratype USNM‒21501 Laguna Beach, California, U.S.A., C. Detail of fibers showing bark and pith. D. General structure of the skeleton, ectosomal area included.