Ocyropsis crystallina ( Rang, 1828 )

Oliveira, Otto M. P. & Migotto, Alvaro E., 2006, Pelagic ctenophores from the São Sebastião Channel, southeastern Brazil, Zootaxa 1183, pp. 1-26 : 15-17

Ocyropsis crystallina ( Rang, 1828)

( Fig. 5 )

Ocyroe crystallina Rang, 1828 .

Ocyroe crystallina — Mayer, 1900a; Moser, 1910.

Ocyropsis crystallina Mayer, 1912 .

Ocyropsis crystallina— Jinbiao, 1977; Harbison et al., 1978; Harbison & Madin, 1979, 1982; Harbi­ son, 1985; Mianzan, 1999.

Ocyropsis crystallina crystallina Harbison & Miller, 1986 .

Ocyropsis crystallina crystallina— Matsumoto & Harbison, 1993.

Examined material

31.vii.2003, Baía do Segredo, Canal de São Sebastião , 23°49'27"S 45°25'19"W, O.M.P.Oliveira coll., adult (ca. 50 mm in width), lobes damaged, Fig. 5 A–C ;

22.ix.2003, Near Farol dos Moleques, Canal de São Sebastião , 23°49'27"S 45°24'42"W, O.M.P.Oliveira coll., three juveniles (5–11 mm in width), one reared to 13.x.2003, other reared to 23.x.2003, Fig. 5D ;

31.xiii.2004, Near Ponta da Sela, Canal de São Sebastião, 23°52'18"S 45°27'17"W, O.M.P.Oliveira coll., one juvenile (ca. 12 mm in width), very damaged, preserved in 95% ethanol;

27.xi.2004, Baía do Segredo, Canal de São Sebastião , 23°49'27"S 45°25'19"W, ca. 10 adults (up to 50 mm in width), observed during snorkelling ;

27.xi.2004, Baía do Segredo, Canal de São Sebastião , 23°49'27"S 45°25'19"W, O.M.P.Oliveira coll., two adults (36–48 mm in width), preserved in 95% ethanol .

Description

Body compressed along tentacular plane, translucent milky white in color, with two well­developed oral lobes arising between apical organ and mouth ( Fig. 5A ). Lobes with strong musculature. Polar field elongated at stomodeal axis, with apical organ at center of aboral extremity of body ( Fig. 5C ). Wide comb plates arranged in short rows, with up to 25 plates in stomodeal rows of adults. Subtentacular rows of comb plates reaching ca. 2/3 length of substomodeal rows. Flattened pharynx with constriction at half its length, opening into a wide, prehensile mouth. Axial and oral tentacles absent. Tentilla absent along mouth margin. Gonads formed at walls of substomodeal meridional canals from oral extremity of comb plates to near extremities of lobes.

Juvenile with 1–3 comb plates in each row and two tentacular bulbs, each associated with a branching, extendable axial tentacle.

Biological notes

Ocyropsis crystallina , a typical inhabitant of oceanic waters (Harbison & Miller,

1986), is apparently uncommon in southeastern Brazilian coastal waters. These cteno­ phores are able to swim relatively fast in escape situations, moving the lobes as if they were “flying” in the water. The lobes help in the hunting process: the comb beats give propulsion, the animal moves with its oral end forward and the lobes capture and handle the prey, transporting it to the mouth. Harbison et al. (1978) described the feeding behavior, stressing that the species feeds on siphonophores, other ctenophores, pteropods, large copepods, small fishes, amphipods, and euphausiids.

In the laboratory, we observed that a juvenile of this voracious ctenophore is able to turn its mouth toward the prey and ingest many Artemia nauplii in a few minutes, until the pharynx is filled up with nauplii. This juvenile, collected in a plankton tow, was 12 mm in width and used its tentacles to capture prey. This specimen was reared in the laboratory for four weeks. After the first ten days, it lost the tentacles, and only traces of the tentacular bulbs remained ( Fig. 5D ). During this period, there was a gradual change in juvenile feeding strategies, from a technique in which the axial tentacles were employed to capture prey to the one in which the oral lobes played the main role in the process of capturing and handing prey. The specimen was preserved after four weeks, when it had reached 17 mm in width.

Remarks

This species seems to be well established. The specimens studied here are similar to those described by Mayer (1912) and can be regarded as Ocyropsis crystallina crystallina according to the definition of Harbison and Miller (1986). Although in principle we accept diagnoses of Harbison and Miller (1986) for the two subspecies ( O. crystallina crystallina and O. crystallina guttata ), in this paper we do not distinguish between them, since we think that morphological variations are inherent to species and because the specific level allows the inclusion of intermediary morphotypes.

Distribution

Tropical western Atlantic ( Moser 1910, Mayer 1912, Harbison et al. 1978, Mianzan 1999), subtropical northwest Atlantic ( Harbison et al. 1978, Harbison & Miller 1986, Matsumoto & Harbison 1993), temperate northwest Atlantic ( Harbison et al. 1978), tropical Indian Ocean ( Harbison et al. 1978), western subtropical Pacific Ocean ( Jinbiao 1977, Harbison & Miller 1986). First record for the southwestern subtropical Atlantic.

Figures

FIGURE 5.—Ocyropsis crystallina (Rang, 1828). A, total view of a damaged adult, in stomodeal plane; B, view of the body surface at the aboral portion; C, closed view of the aboral portion in stomodeal plane; D, total view of a subadult specimen, in stomodeal plane. Legend: ao, apical organ; au, auricle; lo, lobe; mo, mouth; ph, pharynx; sscr, substomodeal ctene row; stcr, subtentacular ctene row.