Crassimarginatella crassimarginata ( Hincks, 1880 )

Ramalho, Laís V., Rodríguez-Aporta, Raquel & Gofas, Serge, 2022, Preliminary account on the bryozoans of the Alboran platform (Western Mediterranean), with description of two new species, Zootaxa 5094 (1), pp. 53-91 : 65-66

Crassimarginatella crassimarginata ( Hincks, 1880)

( Fig. 4 )

Membranipora crassimarginata Hincks, 1880: 71 , pl. 9, fig. 1, 1a.

Crassimarginatella crassimarginata: Hastings 1945: 73 , fig. 1a; Harmelin 1973: 483, fig. 3f (not fig. 3e, g); Harmelin & d’Hondt 1993: 68, fig. 7 (not fig. 8).

Material examined. MNCN 25.03/4284 , MNCN 25.03/4285 : BV12, 112– 120 m; coll. UMA; one living and one dead fragment, respectively. MNCN 25.03/4286 : BV13, 95–99 m; UMA coll.; one living fragment, five dead fragments.

Description. Colony encrusting, uni- or multilaminar ( Fig. 4A ). Zooids oval, longer than wide [L 512–589–696 (N 12, SD 55), W 332–414–486 μm (N 17, SD 48)]; gymnocyst narrow, being slightly more developed at the proximal region; cryptocyst narrow and crenulate ( Fig. 4–D ). A distal and two lateral septula visible in the zooids located at the colony margin ( Fig. 4A ). Vicarious avicularia as large as autozooids [L 545–645–768 (N 3, SD 113), W 356–390–419 μm (N 3, SD 31)], elliptical or elongate oval; thick and complete crossbar, splitting the avicularium almost at the middle ( Fig. 4A, B ), distal opesia and proximal window framed by a narrow crenulate cryptocyst; mandible semicircular. Ovicell hemispherical, subimmersed in distal zooid, wider than long [L 101–149–174 (N 3, SD 40), W 252–281–321 μm (N 3, SD 35)] with a smooth ooecial surface and a transverse slit-like ectooecial fenestra ( Fig. 4C ); ooecia often broken in the Alboran material ( Fig. 4B, D ).

Remarks. Crassimarginatella crassimarginata has two different populations: the “Atlantic” population, characterized by a rounded mandible, and recorded from Madeira (type locality), the Canary Islands, and the Azores; and the “Mediterranean” population whose avicularia have triangular, pointed mandibles ( Harmelin 1973). Harmelin & d’Hondt (1993), studying the bryofauna from the Strait of Gibraltar, observed that the C. crassimarginata populations of the Gulf of Cadiz (BALGIM DR 49, 521 m) and the Alboran Sea (BALGIM DW 132, 170 m) were of the Atlantic type. Hastings (1945) examined material of C. crassimarginata from Madeira present in Norman's collection, and found avicularia with variable shape of the rostrum and mandible: some long and narrow, as in Hincks’ figure (1880: fig. 1a), others with a semicircular mandible, and others broader in proportion to their width; but she did not specify if this variability was inter- or intraspecific. However, Harmelin (1973) did not consider these differences to be specific.As in the colonies from Madeira, the Gulf of Cadiz and the Alboran Sea studied previously ( Hastings 1945; Harmelin & d’Hondt 1993), the specimens analysed here have avicularia with semicircular mandibles, sometimes quite elongate, but never pointed triangular as in the Mediterranean morphotype.

Figures

FIGURE 4. Crassimarginatella crassimarginata (Hincks, 1880) (MNCN 25.03/4285). A. General view of the colony. B. Detail showing an avicularium and a zooid with incomplete ovicell. C. Detail of a fertile zooid showing a complete ovicell. D. Detail of a fertile zooid showing an incomplete ovicell. Scale bars: A, 1 mm; B, D, 200 µm; C, 100 µm.