Copidozoum exiguum ( Barroso, 1920 )

Souto, Javier, Berning, Björn & Ostrovsky, Andrew N., 2016, Systematics and diversity of deep-water Cheilostomata (Bryozoa) from Galicia Bank (NE Atlantic), Zootaxa 4067 (4), pp. 401-459 : 407

Copidozoum exiguum ( Barroso, 1920)

( Figs 6–8 , Table 3 )

Callopora exigua Barroso, 1920: 355 , figs 1–4.

Copidozoum exiguum: Hayward & Ryland 1978: 144 , fig. 2A; Harmelin & d’Hondt 1992: 34, pl. 2, fig. A; Zabala et al. 1993: 67, fig. 1; Hayward & Ryland 1998: 178, fig. 50; Reverter-Gil & Fernández-Pulpeiro 1999a: 36, fig. 1A.

Material examined. MNCN 25.03/3925, 3926, locality DR09; MNCN 25.03/3927, 3928, locality V01; OLL 2015/892, locality V01; OLL 2015/893, 894, locality DR05.

Remarks. The Galicia Bank specimens correspond to published descriptions and figures of Copidozoum exiguum (e.g. Zabala et al. 1993; Hayward & Ryland 1998; Reverter-Gil & Fernández-Pulpeiro 1999a), which was first described from off Santander (N Spain) by Barroso (1920) as Callopora exigua . The species is apparently widespread, occurring in the upper bathyal between 180 and 2018 m depth along the continental shelf of the NE Atlantic and western Mediterranean. Its geographic distribution ranges from the Tunisian shelf ( Harmelin 1979) to the Western Approaches to the English Channel, and it is commonly found on the coral Lophelia ( Hayward & Ryland 1978, 1998; Harmelin & d’Hondt 1992; Zabala et al. 1993). Reverter-Gil & Fernández-Pulpeiro (1999a) already reported this species from different localities on the continental slope close to Galicia Bank between 450 and 688 m depth.

We here illustrate the ancestrula of C. exiguum for the first time ( Fig 7 ). It is similar to an autozooid but smaller and with 14 marginal spines. The ancestrula is surrounded by five autozooids, one distal, two distolateral and two proximolateral.

SD, standard deviation; N, number of measurements

The ooecium of the hyperstomial ovicell is formed by the distal kenozooid, which is invisible from frontal view. The ectooecium is smooth and almost entirely calcified except for a crescentic membranous area on its proximal edge. The borders of this area are thickened.

Copidozoum exiguum is an abundant species, found at nine localities on Galicia Bank, ranging from 826 to 1138 m depth. The majority of the colonies encrust corals while one was found on a shell and another one on a rock.

Figures

FIGURES 6 – 8. Copidozoum exiguum: 6, general view of colony (MNCN 25.03 / 3925); 7, ancestrula and periancestrular zooids (MNCN 25.03 / 3927); 8, autozooid with ovicell and avicularium (MNCN 25.03 / 3925).

Tables

TABLE 3. Measurements (in mm) of Copidozoum exiguum.

	Mean	SD	Minimum	Maximum	N
Autozooid length	0.588	0.0442	0.511	0.689	23
Autozooid width	0.430	0.0459	0.349	0.517	23
Opesia length	0.457	0.0252	0.415	0.504	23
Opesia width	0.327	0.0305	0.280	0.386	23
Ooecium length	0.182	0.0117	0.168	0.192	4
Ooecium width	0.221	0.0119	0.204	0.231	4
Avicularium cystid length	0.256	0.0353	0.206	0.292	7
Avicularium cystid width	0.218	0,0 167	0.195	0.238	7
Avicularium length	0.259	0.0163	0.228	0.279	7
Avicularium width	0.121	0.0148	0.102	0.139	7
Ancestrula length	0.316				1
Ancestrulawidth	0.261				1