Drepanophora birbira Powell, 1967

Harmelin, Jean-Georges, 2014, Alien bryozoans in the eastern Mediterranean Sea — new records from the coast of Lebanon, Zootaxa 3893 (3), pp. 301-338 : 322-324

Drepanophora birbira Powell, 1967

( Fig. 10 A–C, 11A–B; Table 10 )

Drepanophora birbira Powell, 1967a: 173 , text-fig. 2.

Material examined. A, Drepanophora birbira : Specimens from Lebanon: 1) Stn 2A, 1 small colony on pottery debris; 2) Stn 3A, 2 small colonies; 3) Stn 5A, 1 small colony; 4) Stn 17A, 2 small colonies. Specimens from Red Sea: 1) light micrographs of holotype of D. birbira , CMNI 1900-2925, Madote Island, Eritrea; 2) Ras Mohammed, South Sinai, Egypt, Yolanda wreck, 18 m, 15 May 1983, colonies on aluminium plates, JGH coll.; 3) SEM photos ascribed to D. tuberculata (Osburn) by Ostrovsky et al. (2011a), northern Bay of Safaga, Egypt. B, Drepanophora tuberculata : 1) light micrographs of USNM 11835, holotype of Rhynchozoon tuberculatum Osburn, 1914 ; 2) SEM micrographs of USNM specimen from Fort Lauderdale, Florida recorded as Rhynchozoon tuberculatum by Long and Rucker (1970).

Description. Colony encrusting, unilamellar, small. Autozooids elongate, with convex frontal shield entirely covered by small tubercles, separated by grooves partially filled with the slightly prominent edge of vertical walls; 5–8 small marginal pseudopores. Primary orifice longer than broad. Peristome thin and high, distally flared, composed of a distinct distal blade (perpendicular to plane of orifice, with rounded edge) and a collar higher at distal corners and lower proximally, bearing an avicularium on proximolateral edge and, beneath it on inner side, a hookshaped, downcurved, acute denticle that may appear less hooked when tip is eroded. Avicularium directed laterodistally, with narrow triangular rostrum, its tip pointed and slightly hooked, cross-bar thick, complete, its proximal part long, semi-elliptical, with broad, concave cryptocyst and small non-calcified opesia. Ooecium globular, resting on distally adjacent zooid, smooth, an oval foramen on each side. Ancestrula tatiform with 9 spines, opesia oval (175 x 145 µm), gymnocyst moderately long, budding 1 distal and 2 laterodistal daughter autozooids.

Remarks. Powell (1967a) named Drepanophora birbira for a single specimen from the Red Sea (Madote Island, near Massawa) that was deposited (mounted slide) at the National Museum of Canada, now kept at the Canadian Museum of Nature, Ottawa. The Lebanese specimens are similar to D. birbira in having a laterally alate peristome that is non-tubular (i.e. not including the proximal part of the ooecium), a narrow acuminate avicularium with a long subtriangular proximal part, a curved denticle below the avicularium and a frontal shield dotted with tubercles. Examination of optical photographs of the type (courtesy of J.M. Gagnon, curator CMNI) confirms the similarity and reveals also that two atypical features noted by Powell (1967a) in the diagnosis of D. birbira were misinterpretations: the second denticle facing the regular one in a single zooid is nothing more than an artefact and the asserted non-fenestrate nature of the ooecium concerns only one side of the latter (probably owing to secondary calcification) while a foramen is visible on the other side ( Fig. 11 , arrow).

Drepanophora tuberculata ( Osburn, 1914) , originally described from Tortuga Island, Florida, is considered to have a virtually circumtropical distribution ( Tilbrook et al. 2001). It superficially resembles D. birbira in the structure of the frontal shield and position of the avicularium on the outer edge of the peristome. However, as shown by optical photos of the type and SEM photos (courtesy JoAnn Sanner, USNM) of a specimen from Florida recorded as Rhynchozoon tuberculatum Osburn by Long and Rucker (1970), D. tuberculata clearly differs from the latter in the shape of the peristome (tubular in ovicelled zooids and forming a visor distal to the proximal edge of the ooecium), a less-curved denticle than in D. birbira , and the proximal part of the avicularium being rounded with a larger non-calcified opesia instead of long and semi-elliptical with a very broad cryptocyst. Moreover, in Atlantic specimens from West Africa ascribed to D. tuberculata , the ancestrula has six spines ( Cook 1985) instead of nine as in the Lebanese specimens of D. birbira .

Two different Drepanophora species from Safaga ( Egypt, Red Sea) are illustrated by Ostrovsky et al. (2011a). The first species, provisionally assigned to D. indica , clearly differs from the Lebanese specimens in having a more nodular frontal shield with larger marginal pseudopores, a shorter denticle and an ovicell with fenestrae placed more frontally. The second species, identified as D. tuberculata , is most likely conspecific with the specimens from Lebanon. Another Drepanophora species recorded from the Red Sea, D. incisor ( Thornely, 1905) , was listed without comment by Dumont (1981).

Figures

FIGURE 10. Drepanophora birbira Powell, 1967, Lebanon; A, B from Stn 3 A; C from Stn 17 A: A, part of colony showing non-ovicelled zooids; B, distal part of non-ovicelled zooid showing peristome with a distal blade, lateral wings, a hooked denticle and an adventitious avicularium; C, ovicell with lateral foramen. Scale bars: A, 200 µm; B, 50 µm; C, 100 µm.

FIGURE 11. Drepanophora birbira Powell, 1967, holotype (CMNI 1900 - 2925), Eritrea, Red Sea: A, photo of the portion of the type corresponding to Powell’s (1967, text-fig. 2) drawing reproduced in B (A courtesy of J. M. Gagnon, curator CMNI); note arrowed foramen on right side of ooecium (Powell’s drawing does not show the foramen).

Tables

TABLE 10. Drepanophora birbira, morphometrics of three colonies from Stns 3 A, 5 A and 17 A.

D. tuberculata	X	SD	Range	N
Az L	431	49	365–485	22
Az W	268	38	195–375	22
Ov L	175			1
Ov W	195			1