Beroe forskalii Milne Edwards, 1841

Ruiz-Escobar, Fernando, Valadez-Vargas, Diana K. & Oliveira, Otto M. P., 2015, Ctenophores from the Oaxaca coast, including a checklist of species from the Pacific coast of Mexico, Zootaxa 3936 (3), pp. 435-445 : 441-443

Beroe forskalii Milne Edwards, 1841

( Fig. 4 ; Table 3)

Material examined. Oaxaca, Mexico: Four specimens; one specimen 55 mm long at Puerto Ángel Bay, 15°39'54.04" N, 96°29'36.73" W, 7 December 2013, surface, coll. A. Ramos-Silva, placed in 70% ethanol, dissolved after 24 h; UMAR-CTEN-005, 2 specimens (Zipolite, 15°38'49'' N, 96°31'46'' W, 2 m, 25 January 2014, coll. F. Ruiz-Escobar); UMAR-CTEN-006, one specimen (Carrizalillo, 15°51'26.64" N, 97°4'48.89" W, surface, 15 February 2014, coll. F. Ruiz-Escobar).

Description. Body long, very flattened at the tentacular plane, typically conical, at least in the aboral half, with a broad mouth ( Fig. 4 B). Apical organ at the aboral extremity, surrounded by two sets of seven branched aboral papillae, of pink color, the five proximal longer, and two distal shorter. Subtentacular and substomodeal ctene rows about the same length, extending from near the aboral end to about 1/7 of the body distance to the mouth. Meridional canals covered by the ctene rows, with a small uncovered part, never reaching the circular canal around the mouth. Numerous anastomosed diverticulae connecting the meridional canals, and these with the circular canal. Paragastric canals running along both surfaces of the pharynx, also connecting with the anastomosed branches between every two subtentacular meridional canals. Gonads present along the meridional canals and nearest parts of the diverticulae; testes formed between subtentacular and substomodeal meridional canals; ovaries formed between subtentacular and substomodeal meridional canals.

Remarks. The morphology of the studied specimens is similar to those described by Wrobel & Mills (2003). Although the macrociliary patterns were not checked, we had no doubts about species identification, since we found only large adult specimens with full morphological characteristics. It would be different if we had seen juveniles (viz Oliveira & Migotto 2014), whose morphology is sometimes less distinctive.

Distribution. This species is widely distributed in the Atlantic and Pacific Oceans, as well as in the Mediterranean Sea ( Wrobel & Mills 2003; Oliveira & Migotto 2014). In the Eastern Pacific, it occurs along most of the USA coast to Canada ( Wrobel & Mills 2003) and south as far as the Peruvian coast (Oliveira et al., in press).

Total length of the body 50.2 mm

Maximum width of the body 22.2 mm

Length of the subtentacular ctene rows 37.1 mm

Length of the substomodeal ctene rows 38.2 mm

Maximum width between substomodeal and subtentacular ctene rows up to 5.2 mm Maximum width between subtentacular ctene rows up to 7.6 mm Width of the mouth 17.5 mm

Number of ctene plates in subtentacular ctene rows 97–107

Number of ctene plates in substomodeal ctene rows 92–105

Length of the polar field 2785 µm

Length of the papillae up to 823 µm Diameter of the meridional canals up to 950 µm Diameter of the diverticulae up to 253 µm Diameter of the paragastric canals up to 654 µm Diameter of the adradial canal up to 591 µm Diameter of the radial canal up to 443 µm Width of the ctene plates 190–1160 µm Distance between ctene plates 169–401 µm Diameter of the statocyst 189 µm

Figures

FIGURE 4. Beroe forskalii Milne Edwards, 1841. A, stomodeal view of adult swimming vertically; B, adult in stomodeal view; C, preserved specimen, view of the aboral portion; D, preserved specimen, closed view of substomodeal ctene plates. Legend: ao, apical organ; di, diverticulum; fg, female gametes; mg, male gametes; mo, mouth; sscp, substomodeal ctene plate; sscr, substomodeal ctene row; stcr, subtentacular ctene row.