Spurilla neapolitana

SPURILLA NEAPOLITANA (DELLE CHIAJE, 1841)

Eolis neapolitana Delle Chiaje: 1841: pl. 73, figs 14– 16, pl. 88, figs 13–15.

Flabellina neapolitana A. Costa, 1866: 71, pl. 1, fig. 1. Flabellina inornata A. Costa, 1866: 72, pl. 2, fig. 6.

Spurilla gabriellae Vannucci, 1952: 283.

Spurilla mograbina Pruvot-Fol, 1953: 55.

Spurilla dakariensis Pruvot-Fol, 1953: 55.

Material examined: Praia de Manguinhos (Buzios, Rio de Janeiro), 18 March 1998, 0-m depth, one specimen, 18-mm long. Praia de Manguinhos (Buzios, Rio de Janeiro), 23 June 2000, one specimen, 0-m depth, 25-mm long. Praia dos Ossos (Buzios, Rio de Janeiro), 51 specimens, 0-m depth, 4.5–20.5-mm long. Praia dos Ossos (Buzios, Rio de Janeiro), 26 March 1998, 15 specimens, 0-m depth, 4.5–25.5-mm long Praia dos Ossos (Buzios, Rio de Janeiro), 27 June 1999, one specimen, 0-m depth, 8.5-mm long. Praia dos Ossos (Buzios, Rio de Janeiro), 24 June 2000, 11 specimens, 0-m depth, 9–35-mm long. Praia dos Ossos (Buzios, Rio de Janeiro), 25 June 2000, seven specimens, 0-m depth, 11–21-mm long. Praia dos Ossos (Buzios, Rio de Janeiro), 24 July 2003, five specimens, 1 m depth, 11–20-mm long. Praia de Armação (Buzios, Rio de Janeiro), 22 March 1998, 24 specimens, 0-m depth, 9–26-mm long. Praia de Armação (Buzios, Rio de Janeiro), 23 March 1998, five specimens, 0-m depth, 7–20-mm long. Praia de Armação (Buzios, Rio de Janeiro), 24 March 1998, four specimens, 0-m depth, 8–12-mm long. Praia de Armação (Buzios, Rio de Janeiro), 30 June 1999, three specimens, 0-m depth, 13–14-mm long. Praia de Armação (Buzios, Rio de Janeiro), 1 July 1999, six specimens, 0-m depth, 9.5–27-mm long. Praia de Armação (Buzios, Rio de Janeiro), 22 June 2000, one specimen, 0-m depth, 18-mm long. Praia de Armação (Buzios, Rio de Janeiro), 25 June 2000, one specimen, 0-m depth, 20-mm long. Praia dos Ossos (Buzios, Rio de Janeiro), 24 July 2003, five specimens, 1-m depth, 11–20-mm long. Praia do Forte (Bahia), 14 July 2003, one specimen, 0-m depth, 19-mm long. Praia Mar Grande, Ilha de Itaparica (Bahia), 17 July 2003, two specimens, 0-m depth, 7.5–11-mm long.

External morphology: The oral tentacles are elongate, and the rhinophores are perfoliate with between nine and 14 lamellae. Short and fine propodial tentacles are situated on both sides of the mouth. The coloration is variable, from pale brown to pale orange, red–orange or intense red. Ontogenetic variations of coloration exist. The youngest specimens have paler bodies and translucent light spots (Fig. 1H). As they grow, further orange pigmentation is accumulated on the body (Fig. 1I, J, K). The oral tentacles of larger animals have the same colours as the body (a little translucent with whitish tips). The lamellated rhinophores are reddish with white apices. White spots occur on the back and cerata. The cerata are curved at the apex towards the midline of the dorsum; they are long and thick, narrower towards the tip, and are arranged in between six and eight arched groups on either side of the body. The largest cerata are situated on the middle part, and the smallest cerata are at the ends of each arch. The digestive gland inside them is pale brown, and the cnidosacs are pinkish white. The prominent pericardium is located between the first and second ceratal group. The genital opening lies under the first arch, which contains 13–21 cerata, and the anus lies under the second group. The tail is translucent and the foot sole is reddish. The youngest specimens have a whitish body, and brown cerata arranged in three or four groups.

Internal morphology: The radula is uniseriate with between ten and 13 curved teeth. The teeth have a central triangular cusp and numerous elongated denticles (Fig. 9A, B). There are 19–28 denticles on each side of the median cusp, although the small teeth of the radula can have between ten and 12 denticles, and the largest specimens possess teeth with 37–42 denticles on each side (Fig. 10A, B). Furthermore, it is common to find a small and fine denticle next to each side of the median cusp, although this can occur only on one of the sides, or may even be absent (Fig. 10C). The jaws have a smooth masticatory border (Fig. 10D).

Remarks: Spurilla neapolitana is a species that is variable in colour (Garcia-Gomez & Cervera, 1985; Just & Edmunds, 1985). Haefelfinger (1969) attributed this wide range of colour to variable feeding habits. Our specimens, like those from Brazil described by Marcus (1955) and those from Jamaica (Edmunds, 1964), have a predominantly orange body, with white spots covering the dorsum and cerata, and greenish brown digestive glands. Marcus (1955) also mentioned that young specimens are transparent and that the orange pigmentation is lacking.

Some specimens from the Pacific Ocean have pink or orange coloration and brown or grey digestive glands (Gosliner, 1980). Other Pacific animals have yellowish to pink colour and green, brown, or grey digestive glands (Kerstitch, 1989).

Gosliner (1980) observed in his animals that the white pigment may be absent, differing from our animals in that white spots are always present.

Besides the orange or pinkish colour, specimens from the Eastern Atlantic and Mediterranean Sea have yellowish, greenish, or brown coloration (Schmekel & Portmann, 1982; Garcia-Gomez & Cervera, 1985; Just & Edmunds, 1985).

The circular white spots also exhibit variability. According to Schmekel & Portmann (1982) the spots cover the posterior and dorsal faces of the cerata, especially behind the pericardium. Garcia-Gomez & Cervera (1985) only found white spots in some examined specimens, mainly on the anterior faces of the cerata. Just & Edmunds (1985) found white spots on both the body and cerata, and, furthermore, found that the dorsum might be white. Specimens from Huelva (south-western Spain) studied by us have brown–orange or pinkish bodies and cerata (Fig. 8D). Some specimens have a very pale colour, with opaque white pigment on the dorsum (Fig. 8E). Some specimens from O Grove (north-western Spain) were also examined. These specimens had green cerata (Fig. 8F), and circular white spots covering the body and cerata.

A great majority of authors found that the masticatory border of the jaws is smooth (MacFarland, 1909; Marcus, 1955; Marcus & Marcus, 1967; Gosliner, 1980; Schmekel & Portmann, 1982; Garcia-Gomez & Cervera, 1985). However, Bergh (1877) described jaws with a denticulate margin, and Gosliner (1985) proposed that in S. neapolitana the denticulation of the jaws varies intraspecifically. The Eastern and Western Atlantic specimens examined in this paper have smooth jaw margins (Fig. 9C).

The uniseriate radula comprises teeth with denticles on either side of a triangular central cusp. The presence of a very small denticle next to the central cusp was illustrated by Marcus (1955), who did not, however, comment about it in the description. The teeth of our animals have this small denticle on either side of the cusp, although in one radula the denticle may be on one side only or absent. The radular teeth of the Brazilian specimens are clearly different from those of Huelva: the specimens from Huelva lack a median cusp, and in its place have two small denticles (Fig. 9D, E). This characteristic has been observed previously by other authors (Garcia-Gomez & Cervera, 1985) who examined animals collected from the Eastern Atlantic (Cádiz and Huelva) and the Mediterranean Sea. They compared the radular teeth of these specimens, and verified that there is considerable variability in the central zone of the tooth. One specimen from Cubellas (Spanish Mediterranean Sea) studied by Garcia-Gomez & Cervera (1985) has identical teeth to those of our animal from El Portil (Huelva), in that both have two small central denticles. The radulae of the specimens from northwestern Spain comprise about 22 teeth with numerous denticles on each side (Fig. 9F).

Spurilla chromosoma Cockerell in Cockerell & Eliot, 1905 is very similar to S. neapolitana, but possesses ceratal rows in the anterior region of the body (Marcus, 1961; Gosliner, 1985), whereas S. neapolitana presents horseshoe-shaped arches. The newest teeth of S. neapolitana are up to seven times the width of the oldest (this characteristic is present in our animals). In S. chromosoma the teeth are uniform in width or increase only slightly. Another difference is that S. chromosoma has rhinophores with a few lamellae arranged diagonally, whereas in S. neapolitana there are numerous transverse lamellae (Gosliner, 1985).

Distribution: Cape Verde Islands (Pruvot-Fol, 1953); Morocco (Pruvot-Fol, 1953); Senegal (Pruvot-Fol, 1953); Texas (Marcus & Marcus, 1958); Mediterranean Sea (Bergh, 1864, 1876, 1877; Pruvot-Fol, 1954; Schmekel & Portmann, 1982; Garcia-Gomez & Cervera, 1985); French Atlantic coast (Pruvot-Fol, 1954; Just & Edmunds, 1985); Hawaii (Gosliner, 1980); Mexican Pacific coast (Bertsch, 1979); Jamaica (Edmunds, 1964); Miami (Edmunds, 1964); Florida (Engel, 1925; Edmunds, 1964; Marcus & Marcus, 1967; Marcus & Marcus, 1970); Puerto Rico (Marcus & Marcus, 1970); Curaçao (Marcus & Marcus, 1970).

Brazil: Gaibu, PE, Alagoas (MacFarland, 1909), Is. São Sebastião, São Paulo (Marcus, 1955), Praia de Manguinhos, Praia dos Ossos, Praia de Armação (Buzios, Rio de Janeiro), Praia do Forte, Praia Mar Grande, Ilha de Itaparica (Bahia) (present paper).