Alacranes reef (22°31'35"N, 89°46'05"W; two specimens), Cayo Arenas reef (22°07'05"N, 91°24'17"W; three specimens), La Gallega reef (19°13'20"N, 96°07'39"W; two specimens), Ingenieros reef (19°08'41"N, 96°05'22"W; two specimens).

Fully expanded oral disc and tentacles 9–50 mm in diameter. Oral disc smooth, 4–22 mm in diameter, wider than column, dark-orange, brownish, greenish or dark-red, with white or yellowish endocoelic radial stripes tapering from tentacle bases (Figure 3A, B); mouth bright orange or pink (Figure 3B). Tentacles hexamerously arranged in 4–5 cycles (48–76 in number), moderately long (to 6–19 mm length), smooth, slender, tapering distally, inner ones longer than outer ones, contractile, dark-orange to reddish, sometimes with whitish or yellowish tips and pink or purple flashes (Figure 3A–C). Fossa well marked (Figure 3G). Poorly marked endocoelic marginal projections, 17–35, forming acrorhagi (Figure 3G), with holotrichs and basitrichs. Column cylindrical, short, smooth, 5–11 mm in diameter and 5–12 mm in height, dark-orange to dark-red. Pedal disc well-developed, 6–16 mm in diameter, wider than column (Figure 3C), bright-orange or pink. Mesenteries irregularly arranged in four cycles: first and second cycles perfect, others imperfect; more mesenteries proximally than distally (82–89 and 44–48 pairs respectively in specimens examined). Directives absent, 5–6 siphonoglyphs in specimens examined (Figure 3D, E). Gametogenic tissue not observed in specimens examined. Larvae observed in coelenteron of one specimen examined (Figure 3E). Retractor muscles diffuse to restricted; parietobasilar muscles weak with short mesogleal pennon (Figure 3F). Basilar muscles well-developed (Figure 3H). Marginal sphincter muscle endodermal, diffuse (Figure 3G). Longitudinal muscles of tentacles ectodermal (Figure 3I). Zooxanthellae present. Cnidom: basitrichs, holotrichs, microbasic b- and p-mastigophores and spirocysts (Figure 3J–U; see Table 2).

Anemonia sargassensis inhabits shallow waters of the lagoon reef zone, often above Thalassia testudinum blades, but is also found under stones and coral gravel, between 0.5–2 m. It is often reported on floating Sargassum (Carlgren and Hedgpeth 1952). Asexual propagation by longitudinal fission is common (Carlgren and Hedgpeth 1952) and bifurcated tentacles can occur (Hargitt 1908, 1912, Pax 1924, Corrêa 1964, present study).

Western Atlantic, from the northern coast of USA and Caribbean Sea, to the northern coast of Brazil (Carlgren and Hedgpeth 1952, Varela 2002, Zamponi et al. 1998).

Of the 20 valid species of Anemonia, four species have been recorded in the Gulf of Mexico and Caribbean Sea (Fautin 2013): Anemonia sargassensis, Anemonia melanaster (Verrill, 1901), Anemonia depressa Duchassaing & Michelotti, 1860, and Anemonia elegans Verrill, 1901. The anatomy described for Anemonia sargassensis is conflicting mainly in the presence of directives, siphonoglyphs, and marginal projections (e.g. Hargitt 1908, 1912, Pax 1924, Field 1949, Carlgren and Hedgpeth 1952). Just as in Field (1949), Carlgren and Hedgpeth (1952), and Corrêa (1964), we did not find directives in our specimens but 5–6 siphonoglyphs were present. Although some authors suggest that Anemonia sargassensis and Anemonia melanaster are synonymous (Cairns et al. 1986, Ocaña and den Hartog 2002, Wirtz et al. 2003), further studies are necessary to establish the current taxonomic status of both species. Differences between the other two species of the genus in the region, Anemonia depressa and Anemonia elegans, and Anemonia sargassensis are not clear based on the scarce information available and also require further revision.

Alacranes reef (22°22'54"N, 89°40'59"W; four specimens).

Fully expanded oral disc and tentacles 10–19 mm in diameter. Oral disc narrow, smooth, 3–8 mm in diameter, pale green or gray (Figure 4A). Tentacles hexamerously arranged in three cycles (24 in number), smooth, slender, relatively short (to 4–9 mm), tapering distally, inner ones longer than outer ones, contractile, whitish or gray, translucent, oral side with opaque white roundish spots (Figure 4A, B). Fosse well marked (Figure 4E). Column cylindrical, relatively elongate, 3–6 mm in diameter and 6–12 mm in height, with 12 longitudinal rows of verrucae from mid-column to distal margin (Figure 4B, G). Twelve endocoelic marginal projections forming acrorhagi (Figure 4B, E) with holotrichs, basitrichs, microbasic p-mastigophores, and spirocysts. Pedal disc well-developed, 4–8 mm in diameter, slightly wider than column (Figure 4B). Pedal disc and column white to pale green (Figure 4B). Mesenteries hexamerously arranged in 2–3 cycles: only first cycle perfect or first two cycles perfect and third imperfect; same number of mesenteries distally and proximally (12–32 pairs in specimens examined). Only first two cycles fertile (except directives); gonochoric (?), only spermatic cysts observed in specimens examined (Figure 4F). Two pairs of directives each attached to a well-developed siphonoglyph (Figure 4C). Retractor muscles diffuse; parietobasilar muscles well-developed with short mesogleal pennon (Figure 4D). Basilar muscles well-developed (Figure 4H). Marginal sphincter muscle endodermal, weak and diffuse (Figure 4E). Longitudinal muscles of tentacles ectodermal. Cnidom: basitrichs, microbasic b- and p-mastigophores, holotrichs, and spirocysts (Figure 4I–X; see Table 2).

Anthopleura pallida inhabits the intertidal to shallow subtidal zone attached to coral on sandy shores, at 0.5 m. It is azooxanthellate and it broadcast spawns (Daly and den Hartog 2004).

Western Atlantic, from Bermuda (Verrill 1900) to Virgin Islands (Duchassaing and Michelotti 1864). This is the first record for the coast of Mexico; found in Alacranes reef (see Table 1).

Currently there are three valid species of Anthopleura in the Gulf of Mexico and Caribbean Sea: Anthopleura krebsi (Duchassaing & Michelotti, 1860), Anthopleura texaensis (Carlgren and Hedgpeth, 1952), and Anthopleura pallida (Daly and den Hartog 2004). Anthopleura pallida is distinguished mainly in column color and shape, and the arrangement of verrucae in rows, only present from the margin to the mid-column (Daly and den Hartog 2004). However, in Anthopleura krebsi and Anthopleura texaensis, the column is stout rather than elongate, and the verrucae are arranged in rows along the entire column length, from margin to limbus (Daly and den Hartog 2004). Although we found the marginal sphincter muscle diffuse rather than circumscribed-diffuse, all other features including external and internal anatomy and cnidae fit well with the redescription of Anthopleura pallida by Daly and den Hartog (2004).

La Gallega reef (19°13'20"N, 96°07'39"W; thirteen specimens), Ingenieros reef (19°08'41"N, 96°05'22"W; two specimens).

Fully expanded oral disc and tentacles to 20–38 mm in diameter. Oral disc 10–22 mm in diameter, smooth, brown-yellowish, brown-reddish or pale olive-green, sometimes with white or yellowish radial stripes in endocoelic spaces of first two or three tentacular cycles (Figure 5A, B). Tentacles hexamerously arranged in five cycles (about 96 in number), smooth, simple, conical, moderately long (3–5 mm in length), tapering distally, inner ones longer than outer ones, contractile, olive-green, reddish or pale-orange (Figure 5A, B), often with white or yellowish spots on oral side and sometimes with purple flashes. Deep fosse (Figure 5I). Forty-eight endocoelic rounded marginal projections forming acrorhagi (Figure 5C, I) with holotrichs and basitrichs. Column cylindrical, 12–22 in diameter and 7–15 mm in height, densely covered with rounded vesicles, arranged in 96 longitudinal rows from margin to limbus (Figure 5C, G). Pedal disc well-developed, 12–19 mm in diameter (Figure 5C). Column and pedal disc light-brown, orange, reddish, yellowish or olive-green. Mesenteries hexamerously arranged in four cycles (48 pairs in specimens examined): first, second and some mesenteries of third cycle perfect, others imperfect; same number of mesenteries distally and proximally. All mesenteries fertile (except directives); gonochoric; oocytes and spermatic cysts well-developed in specimens collected in January and May (Figure 5E). Two pairs of directives each attached to a well-developed siphonoglyph (Figure 5D). Retractor muscles strong and restricted; parietobasilar muscles well-developed with a relatively long free mesogleal pennon (Figure 5E). Basilar muscles well-developed (Figure 5H). Marginal sphincter muscle endodermal, strong and circumscribed (Figure 5I). Longitudinal muscles of tentacles ectodermal (Figure 5F). Zooxanthellae present. Cnidom: basitrichs, microbasic b- and p-mastigophores, holotrichs and spirocysts (Figure 5J–T; see Table 2).

Bunodosoma cavernatum inhabits shallow waters, attached to rocks and coral rubble, in the lagoon zone; between 2–6 m.

Western Atlantic, from North Caroline to Barbados; along the Caribbean Sea and Gulf of Mexico (Carlgren and Hedgpeth 1952); and Caroline Islands, Micronesia (Bosc 1802). This is the first record for the coast of Mexico; found in the VRS (see Table 1).

Currently four valid species of Bunodosoma have been reported in the Gulf of Mexico and Caribbean Sea (González-Muñoz et al. 2012, Fautin 2013): Bunodosoma cavernatum, Bunodosoma granuliferum (Le Sueur, 1817), Bunodosoma kuekenthali Pax, 1910, and Bunodosoma sphaerulatum Duerden, 1902. Bunodosoma cavernatum differs from Bunodosoma granuliferum because it lacks the distinct chromatic pattern of the column with alternating pale and dark longitudinal bands but also based on molecular evidence (reviewed in González-Muñoz et al. 2012). Our specimens show that the circumscribed marginal sphincter muscle tends to split in two parts as suggested by Carlgren (1952) (Figure 5I). The distinction between Bunodosoma sphaerulatum and Bunodosoma kuekenthali and their Caribbean congeners are not clear based on the information available.

La Gallega reef (19°13'20"N, 96°07'39"W; six specimens).

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 6A, 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 6A, B). Deep fosse (Figure 6G). Twenty-four endocoelic marginal projections (Figure 6C, 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 6C). Pedal disc well-developed, 9–16 mm in diameter (Figure 6C). Column, verrucae, and pedal disc light-brown or beige (Figure 6C). 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 6E). Developing polyps in coelenteron (Figure 6F). Two pairs of directives each attached to a well-developed siphonoglyph (Figure 6D). Retractor muscles strong and restricted; parietobasilar muscles well-developed with relatively long and thick free mesogleal pennon (Figure 6E). Basilar muscles well-developed (Figure 6H). Marginal sphincter muscle endodermal, strong and circumscribed, palmate (Figure 6G). Longitudinal muscles of tentacles ectodermal (Figure 6I). Zooxanthellae present. Cnidom: basitrichs, microbasic b-mastigophores, macrobasic and microbasic p-mastigophores, and spirocysts (Figure 6J–Y; see Table 2).

Isoaulactinia stelloides inhabits shallow waters in the lagoon reef zone, at 1–2 m, near Actinostella flosculifera, Stichodactyla helianthus, and the zoanthid Palythoa caribaeorum (Duchassaing & Michelotti, 1860). It lives with the column burrowed in the sand but the pedal disc attached to rocks and coral rubble. Although we only observed developing oocytes in the two specimens histologically examined, Isoaulactinia stelloides has been reported as a simultaneous hermaphroditic, internally brooding, often with developing polyps in the coelenteron (Belém et al. 1996, Daly and den Hartog 2004); the latter have also been observed in the present study (Figure 6F).

Western Atlantic, from Bermuda to Barbados, and along the Caribbean Sea (Belém 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).

Currently Isoaulactinia has two valid species (Daly 2004, Fautin 2013): Isoaulactinia hespervolita Daly, 2004, and Isoaulactinia stelloides. According to Daly (2004) Isoaulactinia hespervolita differs from Isoaulactinia stelloides in having an unmarked oral disc and tentacles, spinose holotrichs in the column and being gonochoric rather than hermaphroditic. In addition, Isoaulactinia hespervolita has a reddish-orange to greenish-brown column, oral disc and tentacles; approximately 80 tentacles arranged in up to five cycles, and macrobasic p-mastigophores only in the column and tentacles (Daly 2004). We found additional microbasic b-mastigophores in the actinopharynx of Isoaulactinia stelloides but they were not abundant (Table 2). This category of nematocyst has not been previously reported in the actinopharynx of either of the species (Belém et al. 1996, Daly and den Hartog 2004).

Isla Verde reef (19°13'26"N, 96°05'56"W; three specimens); Isla Sacrificios reef (19°10'36"N, 96°05'39"W; three specimens).

Fully expanded oral disc and tentacles to 18–22 mm in diameter. Oral disc smooth, 3–5 mm in diameter, beige and translucent (Figure 7B). Tentacles hexamerously arranged in 3–4 cycles (about 24–52 in number), moderately long (about 5–8 mm length), tapering distally, inner ones longer than outer ones, contractile, gray or beige, translucent, with tips whitish or yellowish and scattered bluish dots along the entire length (Figure 7B, C). Column short, smooth, 3–6 mm in diameter and 6–10 mm in height, bright-brown with faint stripes corresponding to mesenterial insertions. Column distally with 4–6 outgrowths (pseudotentacles). Pseudotentacles branched, ending in globular-shaped vesicles with batteries of macro- and micro-basic p-amastigophores and basitrichs; bluish with gray or brown circle in center (Figure 7A–C). Pedal disc well-developed, circular, 3–7 mm in diameter, light brown or beige, translucent (Figure 7C). Mesenteries hexamerously arranged in 2–3 cycles (12–24 pairs in specimens examined): first cycle perfect and sterile, others imperfect and fertile; more mesenteries proximally than distally (two and three cycles, respectively). Hermaphroditic (Figure 7G). Two pairs of directives each attached to a well-developed siphonoglyph (Figure 7D). Retractor muscles diffuse, strong; parietobasilar muscles with short and thick mesogleal pennon (Figure 7E, F). Basilar muscles relatively poorly developed (Figure 7H). Marginal sphincter muscle absent. Ectodermal longitudinal muscles in distal column. Longitudinal muscles of tentacles ectodermal (Figure 7I). Zooxanthellae present (Figure 7F). Cnidom: basitrichs, macrobasic and microbasic p-amastigophores, and spirocysts (Figure 7J–V; see Table 2).

Lebrunia coralligens inhabits narrow fissures of live coral with only the end of the pseudotentacles visible, between 3–6 m. During the day, the tentacles remain contracted and the pseudotentacles fully expanded allowing the zooxanthellae (particularly abundant in this area) to capture sunlight; at night the situation is the opposite, allowing tentacles to capture food (Sebens and DeRiemer 1977).

Western Atlantic, from Bahamas to Brazil, and along the Caribbean Sea (Wilson 1890, Manjarrés 1978, Acuña et al. 2013, Varela 2002, Herrera-Moreno and Betancourt 2002). Lebrunia coralligens has been recorded in the Mexican Caribbean (Jordán-Dahlgren 2008), and in the VRS (González-Muñoz 2005, see Table 1).

Currently there are two valid species of Lebrunia, both of them distributed in the Western Atlantic (Fautin 2013). They differ in the branched pseudotentacles: those of Lebrunia danae are long and dark-brown whereas those of Lebrunia coralligens are shorter, bright bluish-gray, with rounded ends (González-Muñoz et al. 2012).

La Gallega reef (19°13'20"N, 96°07'39"W; one specimen).

Fully expanded oral disc and tentacles up to 52 mm in diameter. Central part of oral disc smooth, narrow, to 16 mm diameter, beige; mouth oval with a well-developed conchula (Figure 8C). Tentacles small, vesicle-like, arranged in double radial rows covering almost entire oral disc, on endocoelic and exocoelic spaces, 24–26 tentacles per double row; reddish or pinkish rows of tentacles alternating with pale brown rows (Figure 8A–D). Deep fosse (Figure 8G). Column elongated, funnel-shaped, to 60 mm in height, wider distally than proximally; column diameter: distally 38 mm, mid-column 27 mm, proximally 13 mm (Figure 8E). Column with longitudinal rows of vesicles (6–8 vesicles per row) distally (Figure 8B, E). Pedal disc well-developed, narrow, 19 mm in diameter. Column and pedal disc white to pale-brown; mesenterial insertions visible distally (Figure 8E). Mesenteries irregularly arranged in three cycles (28 pairs in specimen examined): first cycle perfect, others imperfect. Gametogenic tissue not observed in specimen examined. Two pairs of directives, only one pair attached to a single well-developed siphonoglyph. Retractor muscles strong, circumscribed, with main muscle lamella divided in two parts; parietobasilar muscles strong with thick mesogleal pennon (Figure 8F). Basilar muscles well-developed (Figure 8H). Marginal sphincter muscle endodermal, strong and circumscribed, pinnate (Figure 8G). Longitudinal muscles of the tentacles ectodermal (Figure 8I). Zooxanthellae absent. Cnidom: basitrichs, microbasic p-mastigophores, and spirocysts (Figure 8J–P, Table 2).

Actinoporus elegans inhabits sandy bottoms, at 1–2 m; the column is burrowed in the sand but the pedal disc is strongly attached to rocks. When disturbed, it contracts the oral disc suddenly, completely burrowing the entire body.

Western Atlantic, from the northern coast of Brazil to Guadeloupe, Jamaica, and Curaçao (Corrêa 1973), and Cape Verde Islands (Wirtz 2009). This is the first record for the coast of Mexico; found in the VRS.

Currently there are two valid species of Actinoporus: Actinoporus elegans and Actinoporus elongatus Carlgren, 1900 (Fautin 2013). Actinoporus elongatus is reported for India, Mozambique and Australia (Carlgren 1900, Menon 1927, Clayton and Collins 1992), and it lacks the longitudinal rows of vesicles in the distal column of Actinoporus elegans (Carlgren 1900, Corrêa 1973). Additional color patterns observed for Actinoporus elegans in coral reefs off the coast of Venezuela include tentacles and oral disc almost completely white with dark-brown stripes, or completely bright orange (unpublished data).

Alacranes reef (22°31'35"N, 89°46'05"W; eight specimens), Serpientes reef (21°26'22"N, 90°28'25"W; five specimens).

Fully expanded oral disc and tentacles 9–48 mm in diameter. Oral disc smooth, wider than column, 3–20 mm in diameter, pale-brown translucent, with small white stripes in endocoelic spaces, sometimes forming a white ring; some specimens also with pink flashes (Figure 9A). Mouth bright yellow, orange, or white; often with purple ring around lips (Figure 9A). Tentacles hexamerously arranged in 5–6 cycles (96–192 in number), smooth, thin, short (2.5–15.5 mm), inner ones longer than outer ones, contractile (Figure 9A, B), tapering distally, pale-brown with a longitudinal row of white dots along entire length (Figure 9A, B); some specimens also with bright-pink flashes mainly at tips. Column trumpet-shaped in extended position, dome-shaped when contracted, 5–24.5 mm in diameter and 4–31 mm in height, divided into narrow, smooth capitulum and wrinkled-texture scapus (Figure 9B). Capitulum pale-brown to yellowish, scapus bright to dark orange often with small white stripes or white flashes slightly above limbus (Figure 9B). Pedal disc well-developed, circular to irregular, wider than column, 6–36 mm in diameter, with mesenterial insertions visible, pale-brown and translucent (Figure 9C). One or two rows of cinclides proximally, near limbus; dark-red or brown (Figure 9B). Mesenteries hexamerously arranged in four cycles; same number of mesenteries proximally and distally (to 48 pairs in specimens examined): first cycle perfect, others imperfect; third and fourth cycles poorly developed, without filaments or acontia. Gametogenic tissue not observed in specimens examined. Two pairs of directives each attached to a well-developed siphonoglyph (Figure 9E). Retractor muscles weak and diffuse; parietobasilar muscles poorly developed (Figure 9E, F). Basilar muscles poorly developed (Figure 9H). Marginal sphincter muscle mesogleal, strong, transversally stratified (Figure 9G). Longitudinal muscles of tentacles ectodermal. Acontia numerous, bright orange (Figure 9C), with basitrichs. Zooxanthellae present. Cnidom: basitrichs, microbasic p-mastigophores, and spirocysts (Figure 9J–Q; see Table 2).

Calliactis tricolor typically dwells on the shells of living hermit crabs often carrying more than one individual (Figure 9D), between 10–30 m. This peculiar symbiotic relationship has been widely studied (reviewed in Gusmão and Daly 2010).

Western Atlantic, from the northern coast of USA to the northern coast of Brazil, along the Caribbean Sea and Gulf of Mexico (Carlgren and Hedgpeth 1952, Zamponi et al. 1998). This is the first record for the coast of Mexico; found in Serpientes and Alacranes reefs.

Of the 18 valid species currently considered as valid of Calliactis, only two have been reported in the Gulf of Mexico and Caribbean Sea (Fautin 2013): Calliactis polypus (Forsskål, 1775) and Calliactis tricolor. These two species differ in the color of the cinclides, white in Calliactis polypus and dark-red in Calliactis tricolor (Gusmão 2010). In addition, Calliactis tricolor is distributed almost exclusively in the western Atlantic whereas Calliactis polypus has a wide distribution range, being found in the Red Sea, Hawaii, French Polynesia, Australia, South Africa, East Africa, Maldives, Cape Verde Islands, Japan, Galapagos, and Louisiana (Gusmão 2010, Fautin 2013).