Discodermia adhaerens van Soest, Meesters & Becking, 2014

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 : 139-141

Discodermia adhaerens van Soest, Meesters & Becking, 2014

Figs. 9

Synonymy and other records. Discodermia adhaerens van Soest, Meesters & Becking, 2014: 416 . Discodermia adhaerens ; Calderón-Gutiérrez et al. 2018:10, Table 1, S3 Table, S5 Table.

Material examined. CNPGG–1484, 1485, Cenote S-1, La Quebrada anchialine cave, Cozumel, Quintana Roo ,

Mexico (20°26’16.75’’N, 86°59’47.44’’W). Depth 4.5 m, January 12, 2015; coll. F. Calderón-Gutiérrez and German Yáñez.

Description. Thinly encrusting sponge barely 1 mm in thickness, several specimens collected measure ca. 9 cm 2 ( Fig. 9a ). Color orange when alive, light gray preserved in alcohol. Surface smooth with slender channels in meander-like shape, visible under light microscopy, no apparent oscules when alive, nor preserved in alcohol ( Fig. 9b ). Consistency difficult to describe, due to the thinness of the specimens.

Skeleton. A thin carpet of discotriaenes closely packed together conform the ectosomal skeleton, with cladomes that cover the outside surface and their rhabdomes heading to the choanosome ( Fig. 9b ). The choanosomal skeleton is a complex link of desmas strongly bound by tubercled zygosis. Additionally, long thin oxeas are present.

Spicules. ( Fig. 9 c-g) Discotriaenes with different cladome deviations or irregular shaped disc, few ovals to round shaped, with serrated and also smooth margins, the upper surface is usually smooth, but some cladomes show a small warty area, 90‒213 × 70‒213 µm. The rhabds are conical and short 15.6‒36.4 × 3.9‒10.4 µm. Desmas tend- ing to tetraclone type 260‒310 × 169‒210 µm. Oxeas with wispy thin endings, often broken by its thin diameter 390‒970 × 8‒10 µm, some with rare stylote modification. Acanthose microrhabds mainly in strongylote category 10.4‒23.4 µm.

Geographic distribution. Open ocean: Bonaire. Anchialine cave: Cozumel ( Mexico).

Ecology. Discodermia adhaerens inhabits two different environments: 1) The upper dysphotic zone, at 146 m deep in the open ocean, Bonaire ( van Soest et al. 2014). 2) The dark zone of anchialine caves, at 4.5 m deep in La Quebrada, and at 11 m deep in El Aerolito, Cozumel ( Calderón-Gutiérrez et al. 2018), suggesting the preference of the species for aphotic environments. Its population size along the La Quebrada anchialine cave was estimated as 1,297±782 individuals ( Calderón-Gutiérrez et al. 2018).

Remarks. The samples studied are identical to Discodermia adhaerens , except that the original description reports thinner oxeas (5–7 µm), and slightly longer acanthomicrorhabds (15–25 µm). Discodermia polymorpha has been found in numerous marine caves in the Mediterranean Sea, at 3-20 m from the entrance of caves, and is also recorded in the bathyal zone of the open ocean at 210‒360 m ( Pisera & Vacelet 2011, Gerovasileiou & Voultsiadou 2012). However, D. polymorpha differs from the present material in shape (spherical to massive) and spiculation categories: presence of micro-oxeas, absence of wispy and thin oxeas, and discotriaenes with larger rhabds (60‒65 µm). Discodermia species recorded in the Caribbean and southwest Florida are: D. dissoluta Schmidt, 1880 from Cuba is a massive lobulated sponge, violet color and very large desmas 524‒1000 µm, discotriaenes 160 µm cladome diameter, 110 µm in rhabd, with 15 and 55 µm for acanthorhabds; inhabits framework reef caves, and shallow to deep-sea environments 0‒150 m deep ( Kobluk & van Soest 1989; Pomponi et al. 2001). D. polydiscus (Bowerbank, 1869) recorded from Saint Vincent and Barbados, has an extreme variation on growth forms, it is irregular, variously creeping sponge, ramose, sprawling or cup shaped, except encrusting forms; yellowish-white color; inhabits 91–217 m deep ( van Soest & Stentoft 1988, Pomponi et al. 2001). The present material conforms to D. adhaerens within the description of van Soest et al. 2014.

Figures

FIGURE 9. Discodermia adhaerens van Soest, Meesters & Becking, 2014. a) CNPGG‒1484 in situ; b) ectosomal layer of discotriaenes (LM); c) overall set of spicules (LM); d) discotriaenes (SEM); e) desmas (LM); f) wispy thin endings of oxeas (LM); g) acanthose microrhabds (SEM).