Isoaulactinia stelloides

Diagnosis. Fully expanded oral disc and tentacles to 24 - 38 mm in diameter. Oral disc smooth, slightly wider than column, 9 - 11 mm in diameter, light- or olive-green, sometimes with small white stripes near tentacles bases (Figure 6 A, B). Tentacles hexamerously arranged in four cycles (about 48 in number), simple, smooth, moderately long (9 - 14 mm in length), conical, tapering distally, inner ones longer than outer ones, contractile, olive-green with white bands along entire length (Figure 6 A, B). Deep fosse (Figure 6 G). Twenty-four endocoelic marginal projections (Figure 6 C, G) with basitrichs and macrobasic p-mastigophores. Column cylindrical, 8 - 12 in diameter and 13 - 22 mm in height, with approximately 48 longitudinal rows of verrucae along entire column, but more conspicuous distally (Figure 6 C). Pedal disc well-developed, 9 - 16 mm in diameter (Figure 6 C). Column, verrucae, and pedal disc light-brown or beige (Figure 6 C). Mesenteries hexamerously arranged in three cycles (24 pairs in specimens examined): all cycles perfect; same number of mesenteries distally and proximally. First and second cycles fertile (except directives); hermaphroditic (?), only oocytes observed in specimens examined (Figure 6 E). Developing polyps in coelenteron (Figure 6 F). Two pairs of directives each attached to a well-developed siphonoglyph (Figure 6 D). Retractor muscles strong and restricted; parietobasilar muscles well-developed with relatively long and thick free mesogleal pennon (Figure 6 E). Basilar muscles well-developed (Figure 6 H). Marginal sphincter muscle endodermal, strong and circumscribed, palmate (Figure 6 G). Longitudinal muscles of tentacles ectodermal (Figure 6 I). Zooxanthellae present. Cnidom: basitrichs, microbasic b-mastigophores, macrobasic and microbasic p-mastigophores, and spirocysts (Figure 6 J-Y; see Table 2).

Distribution. Western Atlantic, from Bermuda to Barbados, and along the Caribbean Sea (Belem et al. 1996, Daly and den Hartog 2004). This is the first record for the coast of Mexico; found in the VRS (see Table 1).