Chalinula cf. molitba ( De Laubenfels, 1949 )

Sim-Smith, Carina, Hickman, Cleveland & Kelly, Michelle, 2021, New shallow-water sponges (Porifera) from the Galápagos Islands, Zootaxa 5012 (1), pp. 1-71 : 11-12

Chalinula cf. molitba ( De Laubenfels, 1949)

( Fig. 5 )

Haliclona molitba De Laubenfels 1949: 9–10

Haliclona crassiloba De Laubenfels, 1950: 45–47

Haliclona pseudomolitba De Weerdt, Rützler & Smith, 1991: 197–198 ; fig. 3d, 4g –h, 5a–b, d

Reniera carmabi Van Soest, 1980: 14–15 . fig. 4

Chalinula molitba De Weerdt, 2000: 55–59 , fig. 2e, f, 3s, w, 42a–f

Material examined. MCCDRS9439, Los Hermanos Islands, 0.867° S, 90.782° W, 6 m, 18 Jan 2003.

Type locality. Bermuda .

Habitat and distribution. Caribbean, Gulf of Mexico, Bermuda, Brazil, Galápagos Islands.

Description. Thinly encrusting sponge, ≤ 10 mm thick, covered in short cylindrical or volcano shaped oscules that are around 5 mm high and 4 mm in diameter. Colour in life is lilac, with faint tan patches, oscules have a sharp, whitish margin; colour in ethanol is golden brown ( Fig. 5A–B ). Texture is extremely soft, compressible, easily torn, surface is smooth to the touch.

Skeleton. No ectosomal skeleton is present. The choanosomal skeleton is an isotropic reticulation of spicules that are completely encased in spongin. Most secondary tracts are unispicular, but occasionally they are 2–3 spicules in length. Free spicules are also present at low density in the choanosome ( Fig. 5C ).

Spicules. Megascleres —small oxeas; 113 (103–129) × 7 (5–9) µm (n = 20) ( Fig. 5D ).

Remarks. The holotype of Chalinula molitba ( De Laubenfels, 1949) was described as a violet coloured, amorphous sponge with a reticulated skeleton of fibres that were around 30 µm in diameter and lightly cored by oxeas (100 × 2 µm). De Weerdt (2000) redescribed the species after examining over 60 specimens, to include a wide variety of characteristics, ranging from: tubular to encrusting specimens; spongin- to spicule-dominated skeletons with scarce spongin; and strongyloxeas (45–99 × 0.5–2.6 µm) to oxeas (66–144 × 1.3–7 µm).

Chalinula molitba is an eastern Atlantic species that has not been recorded from the eastern Pacific. However, the gross morphology, skeletal architecture and colour in life of our specimen fits well within the range of specimens of C. molitba described in De Weerdt (2000). Given the wide range of characteristics in De Weerdt’s C. molitba specimens, it is probable that they are not all the same species, but separation of these specimens, and ours, is likely to require re-examination using molecular tools. Molecular techniques such as sequencing mitochondrial DNA markers are becoming increasingly important for resolving accurate species boundaries (see Swierts et al. 2017) and answering broad questions of whether the purported distribution of sponges across the Panama isthmus is real. The Galápagos specimen has been given a tentative assignment to this species until further taxonomic work on the species is conducted.

Only one species of Chalinula has been reported from the eastern Pacific: Chalinula ecbasis ( De Laubenfels, 1930) from California. That species differs from the Galápagos specimen in that it is a digitate or ramose sponge, up to 10 cm high, with apical oscules.

Ávila and Carballo (2008) reported that the western Pacific sponge, Chalinula nematifera ( De Laubenfels, 1954) had invaded the Mexican Pacific coast. Although no taxonomic description of the sponges are provided by Ávila and Carballo (2008), the images provided do not match with the species description of C. nematifera , which is a thinly encrusting, vibrant mauve sponge with distinctive pale wavy ‘surface threads’, and very small oscules (oscules were not observed by De Laubenfels) ( De Laubenfels 1954; De Weerdt 2002; Rossi et al. 2015). In contrast, the Mexican Pacific specimens ( Fig 1 . in Ávila and Carballo (2008)) were pale lilac in colour, possessed obvious volcano shaped oscules, and lacked the wavy surface threads. The external morphology of the Mexican Pacific specimens is similar to the Galápagos specimen of C. cf. molitba , but further taxonomic work is required to confirm whether they are the same species.

Genus Haliclona Grant, 1841

Diagnosis. Chalinidae with unispicular secondary lines (from De Weerdt 2002).

Subgenus Haliclona Grant, 1836

Diagnosis. Choanosomal skeleton consisting of a very regular, ladder-like reticulation of uni- to paucispicular primary lines, regularly connected by unispicular secondary lines. Ectosomal skeleton, if present, a unispicular tangential isotropic reticulation; occasionally with the oxeas ‘intercrossing’. Oxeas short, rather robust, fusiform or with acerate points. Spongin moderate to abundant (from De Weerdt 2002).

Figures

FIGURE 1. Sponge collection sites around the Galápagos Archipelago in this study.

FIGURE 5. Chalinula cf. molitba (De Laubenfels, 1949). MCCDRS9439: A. In situ. B. Deck photo of a small sample; C. Cross section of the choanosome. D. Oxeas.