Diplastrella cozumella, Gómez & Calderón-Gutiérrez, 2020

Gómez, Patricia & Calderón-Gutiérrez, Fernando, 2020, Anchialine cave-dwelling sponge fauna (Porifera) from La Quebrada, Mexico with the description of the first Mexican stygobiont sponges, Zootaxa 4803 (1), pp. 125-151 : 144-145

Diplastrella cozumella sp. nov.

Fig. 12

Synonymy and other records. Diplastrella sp.; Calderón-Gutiérrez et al. 2018:Table 1, S3 Table, S5 Table.

Material examined. HOLOTYPE CNPGG‒1496, Cenote S-1, La Quebrada anchialine cave, Cozumel , Quin- tana Roo, Mexico (20°26’16.75’’N, 86°59’47.44’’W). Depth 4.7 m, January 12, 2015; coll. F. Calderón-Gutiérrez and German Yáñez. PARATYPES CNPGG‒1495, same data as holotype. CNPGG‒1545, 1546, 1547, 1548, same locality. Depth 5.2 m, October 23, 2015 ; coll. F. Calderón-Gutiérrez and German Yañez.

Description. Thinly encrusting sponge, the size range of samples is 1.1‒ 5 cm long, 0.5‒2 cm wide and less than 1 mm thick ( Fig. 12a ). Color mustard yellow when alive, light grey in alcohol, crystal glows in dry state. Surface microhispid, velvety looking owing to the protruding tylostyles ( Fig. 12b ). Several oscules in clusters at whitish areas of preserved specimens. Consistency incompressible owe to the thinly encrusting body and detaches easily from the rock.

Skeleton. A single basal layer of microscleres covers the entire body surface pierced by many tylostyles, the latter protruding upright or leaned to the surface with almost 1 mm outside it, with tips upwards. Microscleres are also placed around the bases of tylostyles.

Spicules. ( Fig. 12 c-g) Peculiar tylostyles smooth and straight, always with prominent trilobate heads to up to six lobes, with concave endings or ending in a hollow-like shape, probably in two overlapping size categories, overall range 270‒800 × 7.8‒15 µm, head 14.3‒26 µm in width, 4.4‒18.2 µm in length. Two categories of asters occur, 1) large spheraster-like, 25‒49.4 µm as the more common microsclere, some tend to an oxyspheraster-like in a smaller size 7.8‒18.2 µm. 2). Small diplasters in low numbers, and overlapping in size with the previous one, with an average size of 7.8 µm, are difficult to see.

Etymology. The specific name refers to the type locality, Cozumel Island.

Geographic distribution. Only known from the type locality.

Ecology. This is a stygobite species. Observed at the entrance of the cave and throughout up to Cenote Km-1, from 4.5 and 7.6 m deep, generally on the floor and under rocks. Its population size along the cave was estimated as 6,486±1,801 individuals ( Calderón-Gutiérrez et al. 2018).

Remarks. Diplastrella cozumella sp. nov. is markedly distinguished by the trilobed trait on tylostyle heads with concave endings, a trait that does not occur in another congeneric taxon. Two western Atlantic species of Diplastrella , lack this type of tylostyle, in addition to have different spicule sizes. D. megastellata Hechtel, 1965 from Jamaica and also recorded in a marine cave at the Bahamas ( Slattery et al. 2013), has thicker tylostyles 9‒26 µm, and large branching spherasters 29‒79 µm. D. spirastrelloides van Soest, 2017 recorded in the Guyana shelf at 94 m depth, also has thicker tylostyles 5‒24 µm, and larger spiraster-like 11‒26 µm. Two more species of Diplastrella have been observed in marine caves from the Mediterranean ( Gerovasileiou & Voultsiadou 2012), D. bistellata (Schmidt, 1862) and D. ornata Rützler & Sarà, 1962 , again not conspecific with the new species.

Figures

FIGURE 12. Diplastrella cozumella sp. nov. a) Holotype CNPGG‒1496 in vivo; b) surface with protruding tylostyles (ethanol); c) overall set of spicules (LM); d) tylostyle endings (LM); e) diplaster to spheraster (SEM); f) tylostyle with blunt end (LM); g) tylostyles with multilobed tylo, and concave endings (SEM).