Carybdea xaymacana Conant, 1897

Acevedo, Melissa J., Straehler-Pohl, Ilka, Morandini, André C., Stampar, Sergio N., Bentlage, Bastian, Matsumoto, George I., Yanagihara, Angel, Toshino, Sho, Bordehore, César & Fuentes, Verónica L., 2019, Revision of the genus Carybdea (Cnidaria: Cubozoa: Carybdeidae): clarifying the identity of its type species Carybdea marsupialis, Zootaxa 4543 (4), pp. 515-548 : 524

Carybdea xaymacana Conant, 1897

Figs. 1 E–I; 7B, D, F

Material examined: Five (5) specimens from Smithsonian Institution (USNM 54457, 54458, 54461); polyps and newly released medusae from the cultures of R. Petie, member of the working group of Assistant Prof. A. Garm, University of Copenhagen, Denmark, originally sampled by B. Werner, C. E. Cutress, and J. P. Studebaker (1971) in Puerto Rico.

Diagnosis: Gastric phacellae epaulette shaped, single rooted; Velarial canals 2 per octant; biforked; Pedalia knee bend volcano-shaped to triangular.

Description: Adult medusa: Bell ( Fig. 1E ), highly transparent, colourless, bell-shaped, scattered with very small colourless nematocyst warts; mammilation scatters bell from apex to bell margin (bigger nematocyst warts at interradial furrows, smaller nematocyst warts on bell sides): apex plane convex ( Fig. 1E ), slight horizontal constriction near the top present. Bell height up to 24 mm, bell width up to 27 mm.

Pedalia ( Fig. 1H ), 4, simple, unbranched flattened, scalpel-shaped, measures approx. 1/3 – 1/2 bell height in length, situated in each interradial corner, with irregular, white nematocyst bands on outer keel of pedalia, very small warts scatter outer half of pedalia, carrying single, flesh coloured tentacles in the interradial corners of the bell rim, pedalial canal strongly depressed at base (diamond-shaped in diameter), going straight through pedalium, showing a volcano-shaped to triangular knee bend with small peak appendage on outer knee bend.

Rhopalia, 4, located inside heart-shaped rhopalial niche ostium, with triangular covering scale ("angle" rounded), scale scattered with very small nematocysts, approx. 1/7 to 1/8 of bell height up from margin; rhopalium with 6 eyes (2 median lens eyes + 2 lateral slit eyes + 2 lateral pit eyes).

Velarium ( Fig. 1I ), with very small nematocyst warts, containing 2 velarial canals per octant, broad in width, forked at tips, sharp tips, seldom dendritic, at times with more than 2 branches; canals flanking frenulum simpler, sometimes unforked, canals flanking pedalia more complex with 2 to 3 main branches and sometimes with single side branches.

Manubrium (1/3 – 1/2 bell height in length), 4 lobes, cruciform without nematocyst warts, and connected to flat and shallow stomach; stomach communicates perradially with 4 gastric pockets leading into velarial canals. Gastric phacellae ( Figs. 3F, G ), 4, epaulette-shaped, mounted on 4 stomach corners, consisting of 30–35 filaments per quadrant originating from a single root.

Gonads, 4 pairs, narrow leaf-like, separated by unperforated interradial septum, extending from stomach rim to bell margin, tapering toward stomach rim and bell margin; differences in the gonads between both sexes can be observed under the microscope, as for other carybdeid species; ripe gonads milky whitish.

Early development of newly released medusae from polyps ( Figs. 7B, D, F ): Bell ( Fig. 7B ), yellowish, tetraradial, slightly pyramidal shaped with large, ovoid (0.14 mm x 0.06 mm) nematocyst warts, both sides of the interradial furrow; bell height up to 1.4 mm, bell width up to 1.2 mm.

Tentacles, 2 (primary) ( Fig. 7B ), located on opposite corners, lacking pedalia, resembling pearl-string with spherical, orange coloured, and lens-shaped, white nematocyst batteries ( Fig. 7D ); during further growth medusa develops a second pair of tentacles between primary tentacles.

Rhopalial niche ostia not yet developed, rhopalium with 6 eyes ( Fig. 7F ) (2 median lens eyes + 2 lateral slit eyes + 2 lateral pit eyes).

Gastric filaments, 4, one per quadrant.

Remarks: The species C. xaymacana was first reclassified as C. marsupialis var. xaymacana by Mayer (1910) and then as C. marsupialis xaymacana by Bigelow (1938). Later, Kramp (1961) and Studebaker (1972) listed both C. xaymacana and C. murrayana as synonyms of C. marsupialis , but Gershwin (2005) hinted at the separation of these species.

Reported distribution of C. xaymacana: Caribbean Sea

Figures

FIGURE 1. Characters for identification of Carybdea species (species in order of appearance in the text). C. marsupialis: A) adult medusa (preserved) B) epaulette-shaped gastric phacellus C) pedalial canal with rounded knee bend without appendage D) octant of velarium with 3 canal roots, note slender, very sharp tipped velarial canals. C. xaymacana: E) adult medusa (preserved) F) single rooted gastric phacellum, original drawing of Bigelow (1938) G) gastric phacellus H) pedalial canal, note knee bend with appended peak (arrow) I) octant of velarium, note two broad, biforked, sharp-tipped velarial canals. Carybdea confusa: J) adult medusa (preserved) K) single stemmed, single rooted gastric phacellus L) pedalial canal knee bend with appended thorn (arrow) M) octant of velarium, note two multiple branched, round tipped velarial canals. Scale bar: 1 cm.

FIGURE 3. Characters for identification in species of the family Carybdeidae (species in order of appearance in the text; preserved specimens). C. brevipedalia: A) adult medusa (preserved) B) linear gastric phacellus C) gastric filament, note long stem (arrow) D) peaked (arrow) pedalial canal knee bend E) octant of velarium with 3 canal roots. C. rastonii: F) adult medusa (preserved) G) linear gastric phacellus H) pedalial canal with rounded knee bend I) octant of velarium, note two broad, blunt tipped velarial canals. Scale bar: 1 cm.

FIGURE 7. Comparison between smaller stages of C. marsupialis (left column) and C. xaymacana (right column): A and B) general view of the small cubomedusae, 4 tentacles in C. marsupialis and 2 tentacles in C. xaymacana; C and D) comparison of the tentacles; E and F) detail of the rhopaliar niche. Photographs taken of live specimens (with exception of E): E. Obis.