Beroe forskalii Milne Edwards, 1841

Oliveira, Otto M. P. & Migotto, Alvaro E., 2014, First occurrence of Beroe forskalii (Ctenophora) in South American Atlantic coastal waters, with notes on the use of macrociliary patterns for beroid identification, Zootaxa 3779 (4), pp. 470-476 : 471-473

Beroe forskalii Milne Edwards, 1841

( Figures 1–2 ; Table 1 )

Beroe forskalii Milne Edwards, 1841 — Chun 1880; Tamm & Tamm 1991, 1993; Haddock & Case 1999; Mianzan 1999; Wrobel & Mills 2003; Lindsay & Hunt 2005; Lindsay 2006; Shiganova & Malej 2009.

Material examined. MZUSP 00012, a single specimen 2.5 cm long from Canal de São Sebastião , 23.8° S, 45.4° W, coll. A. Migotto 8 July 2010, reared to 10 July 2010 then fixed in 4% formalin .

Description. Body sac-shaped, pinkish, with broad mouth; body width tapering from middle to aboral extremity of body ( Fig. 1A ); compressed along tentacular plane ( Fig. 1C ). Eight meridional canals extending from aboral region towards mouth and connected with a circular canal around mouth by a mesh of anastomosing canals; these with lateral diverticulae, mostly with blind ends in aboral half of body, but forming anastomoses along oral half ( Fig. 1F ). Diverticulae from subtentacular meridional canals connected with paragastric canal ( Fig. 1E ). Ctene rows located above meridional canals arising at aboral region. Substomodeal ctene rows extending for about 3/4 the length of the meridional canals to oral region. Subtentacular ctene rows limited to aboral 2/3 of body. Mouth wide, semicircular, occupying whole oral region, opening into large pharynx that occupies most of central inner part of animal. Two opposite paragastric canals, extending from aboral pole of pharynx to circular canal around mouth, crossing at tentacular plane. Aboral extremity of body mitriform ( Fig. 1D ). Apical organ including a statolith at center of polar fields. Aboral papillae prominent, branched ( Fig. 1G ), projecting from margins of polar fields, forming an “hourglass” figure, oriented in stomodeal plane when in aboral view ( Fig. 1B ). Each papilla with first- and sometimes second-order branches in a pinnate arrangement; branches curving toward exterior of polar field. The animal is a simultaneous hermaphrodite, with gonads formed at lateral walls of meridional canals and nearby diverticulae ( Fig. 1E ). Ovaries restricted to portion of meridional canals under ctene rows. Testes lying along all meridional canals and adjacent diverticula. Gonads of adjacent meridional canals facing those of same gender on the adjacent canal, i.e. female gonads face in stomodeal-stomodeal and tentacle-tentacle patterns; male gonads face in a stomodeal-tentacular arrangement. Macrocilia are robust (length 5–7 times width), with about 20 small teeth along edge ( Fig. 2 ), covering extensive area of oral portion of stomodeal cavity, arranged in long tapering stripes that run from lip toward center of stomodeum.

Remarks. The young individual on which the above description is based, was very active for the three days it was kept in the aquarium, swimming quickly, sometimes with the mouth open. It resembled Beroe mitrata Moser, 1907 , except for the presence of anastomoses and the pointed end of the aboral portion ( Wrobel & Mills, 2003). Based on the shape of their macrocilia, these two species form a distinct group within the genus Beroe ( Tamm & Tamm 1993) . In these two species, the macrocilia are very similar, differing only by their pattern of distribution along the stomodeal cavity, comprising a carpet covering all of the oral portion of the stomodeum in B. mitrata and long tapering stripes that run from the lip toward the center of the stomodeum in B. forskalii ( Tamm & Tamm 1993) . On this basis, inter alia, the specimen from São Sebastião Channel was certainly B. forskalii . The first description of what was probably this species was made by Forskål (1775), as Beroe rufescens . This name was not used by later researchers after Milne Edwards (1841) questioned its validity. The combination Beroe forskalii has been used in at least 20 publications in the last 50 years and, following the nomenclatural Principle of Stability ( ICZN 1999), its use may continue. The author of the combination Beroe forskalli is taken as Milne Edwards (1841), not Chun (1880), following the Principle of Priority ( ICZN 1999).

Distribution. Beroe forskalii is distributed worldwide (e.g. Moser 1910; Mianzan 1999; Lindsay & Hunt 2005; Shiganova & Malej 2009; Oliveira et al. submitted).

Figures

FIGURE 1. Beroe forskalii Milne Edwards, 1841. A, Entire specimen in stomodeal plane; B, same, aboral view; C, same, in tentacular plane; D, view of the aboral end in stomodeal plane; E, close-up of meridional canals and diverticula with male and female gonads; F, close-up of anastomosing diverticula near the mouth; G, close-up of the aboral end of the body. Abbreviations: adc, adradial canal; ao, apical organ; di, diverticule; fg, female gonads; ap, anal pore; mg, male gonads; mo, mouth; pa, papilla; pc, paragastric canal; pf, polar field; sscr, substomodeal ctene ro w; stcr, subtentacular ctene row; ssmc, substomodeal meridional canal; stmc, subtentacular meridional canal.

FIGURE 2. Beroe forskalii Milne Edwards, 1841. A, Partial oral view of the specimen, after two months of preservation in 4% formalin; B, interior view of stomodeum through the partially opened mouth, showing the macrociliary stripes; C, DIC image of macrocilia oriented toward the base of the stomodeum (two rows of teeth visible); D, DIC image of macrocilia oriented toward the mouth (only one row of teeth visible); E, DIC image of distal ends of macrocilia oriented toward the base of the stomodeum. Abbreviations: eaz, epithelial adhesive zone; lip, lip edge; mc, macrocilium; mcs, macrociliary stripes; mct, macrocilium teeth; mo, mouth; sscr, substomodeal ctene row; stcr, subtentacular ctene row.