Calyptotheca alexandriensis

Description. Colony erect, foliaceous, comprising an open honeycomb of anastomosing bifoliate fronds forming a spheroidal mass (Fig. 2 A). Intracolonial overgrowths occasionally developed. Uniporous septulae present in lateral and transverse vertical walls, situated close to the basal wall (Fig. 4 C). Colour vivid deep orange to red when alive (Fig. 2 A – C), fading to pale brown in spirit or dry. Ancestrula and early astogeny unknown. Autozooids subrectangular, about 1.75 x longer than wide (Figs 3 A, 4 A). Frontal shield moderately convex, densely pseudoporous, pseudopores subcircular, about 10 – 35 µm in diameter, decreasing in size from the centre to the edge of the frontal shield, sunken, calcification around the pseudopores in the form of a polygonal network with low pustules often present at the corners; marginal areolar pores not clearly distinct from pseudopores; zooidal boundaries well defined, marked by thin but well-defined salient walls. Primary orifice broader than long (Figs 3 B, 4 D), inclined to face distofrontally, with a broad, U-shaped sinus divided from the semielliptical poster by a pair of rounded, non-serrated condyles. Closure plates cover some orifices, imperforate and with an irregularly granular surface (Fig. 4 B). Ovicells present in a high proportion of zooids (Figs 3 C, 4 A, B), hyperstomial, bulbous, wider than long, ectooecium uncalcified, endooecial calcification resembling frontal shield but with smaller, more closely spaced pseudopores; floor of incompletely developed ovicells with a scattering of 10 – 20 irregularly arranged pores of variable size (Figs 3 A, 4 A, B). Ovicellate zooids without apparent orificial dimorphism. Avicularia suboral (Figs 3 B, 4 D, F), present in the majority of, possibly all, zooids, oriented predominantly laterally but slightly distally, all avicularia on the same side of a frond apparently oriented in the same direction, either facing left or right; plane of avicularium inclined at a steep angle to the frontal surface of the colony; small in size, about 0.08 – 0.09 mm long; opesia semicircular; pivotal bar complete, more or less straight, longer than opesia; rostrum arch-shaped, with a hook-like distal end. Vicarious avicularia not observed. Measurements. See Table 1.

Remarks. The shape of the primary orifice, with a broad sinus and condyles, evenly pseudoporous frontal shield, presence of adventitious avicularia and ovicell morphology permit this bryozoan to be assigned to Calyptotheca. As noted above, Calyptotheca is a speciose genus (Bock et al. 2017). There is considerable variability in the shape, disposition and orientation of the adventitious avicularia. Cumming & Tilbrook (2014) identified a subgroup of species having suboral avicularia, like that seen in the new species from Egypt. However, in most of these species the avicularium is oriented parallel to the length of the autozooid, whereas in C. alexandriensis n. sp. it is oriented transversely. Only two species of Calyptotheca have been recorded previously from the Mediterranean Sea according to a recent review of bryozoans from the Mediterranean Sea (Rosso & Di Martino 2016). Hayward (1974) originally described Calyptotheca rugosa from Chios in Greece. This species is encrusting, unlike C. alexandriensis n. sp., and also differs from C. alexandriensis n. sp. in having rare, rounded suboral avicularia and partially immersed ovicells. A second species of Calyptotheca, found in the Strait of Gibraltar as well as the Atlantic (Azores), was described as Calyptotheca obscura (Osburn, 1952) by Harmelin et al. (1989). This species has transversely oriented adventitious avicularia of similar morphology to those of C. alexandriensis n. sp. but, unlike C. alexandriensis n. sp., the avicularia are positioned around the edges of the autozooids rather than suborally. The colour of C. obscura is dark red whereas that of C. alexandriensis n. sp. is very dark orange, and C. obscura has encrusting colonies and denticulate condyles contrasting with the erect colonies and smooth condyles of C. alexandriensis n. sp. Dumont (1981) recorded five species of Calyptotheca from the Red Sea: Calyptotheca acutirostris (Canu & Bassler, 1929), Calyptotheca heteroavicularia Dumont, 1981, Calyptotheca nigra Dumont, 1981, Calyptotheca sudanensis Dumont, 1981, and Calyptotheca wasinensis (Waters, 1909). All of the species from the Red Sea have encrusting colonies in contrast to the erect colonies of C. alexandriensis n. sp.. Adventitious avicularia in C. acutirostris are located proximolaterally of the orifice and directed distally, those of C. heteroavicularia are suboral and directed proximally, C. nigra lacks adventitious avicularia, and in C. wasinensis the adventitious avicularia are scattered around the edges of the autozooids. Only those of C. sudanensis are suboral and directed laterally, as in C. alexandriensis n. sp., but this reef-associate has small, brown- or green-coloured colonies quite unlike the large deep orange colonies of C. alexandriensis n. sp.. A website devoted to the bryozoans of the Northern Bay of Safaga in the Red Sea contains SEM images of six species of Calyptotheca: C. wasiensis, C. nigra, C. sudanensis, C. cf. wasiensis, Calyptotheca sp. 1, and Calyptotheca sp. 2 (Ostrovsky et al., accessed 20 March 2017). Images of the four specimens identified as C. sudanensis show the closest resemblance to C. alexandriensis n. sp., particularly with respect to the transverse suboral avicularium, although this appears to be smaller and restricted to one side of the sinus in the Safaga material. In addition, the floor of the ovicells appears to lack the large pores seen in C. alexandriensis n. sp. The lack of descriptive text means that colony-form and colour cannot be compared between the material from Safaga and Alexandria. In possessing a transversely oriented suboral avicularium, C. alexandriensis n. sp. resembles the species Calyptotheca subimmersa (MacGillivray, 1879) from Australia. However, the avicularium of C. subimmersa is smaller than that of C. alexandriensis n. sp., rounded rather than arch-shaped, and opens in the plane of the frontal surface of the zooid instead of being steeply inclined.

Distribution. Eastern Harbour, Alexandria, Egypt.

Etymology. Named for Alexandria, the type locality.

Material examined. Holotype: TBAB BR- 2015 - 2 - 10 (Fig. 3), Mediterranean, Alexandria, Eastern Harbour, 0 – 1 metre depth on metallic marina supports, collected by Mohamed M. Dorgham and Khaled M. Abdelsalam, December 2015. Paratypes: TBAB BR- 2016 - 2 - 11 (Fig. 2 A), NHMUK 2016.12. 22.1 (Fig. 4), details as for holotype.