Peniagone purpurea Theel 1882

Peniagone purpurea (Théel, 1882)

(Figs 6 A–D, 7)

Elpidia purpurea Théel, 1882: 21 –23, pls 7 (figs 4–6), 33 (figs 13–14), 44 (fig. 6) Elpidia ambigua Théel, 1882: 27 –28, pl. 33 (fig. 6)

Peniagone vexillum R. Perrier, 1900: 118

Peniagone ferruginea Grieg, 1921: 7 –8, fig. 3, pl. 1 (figs 4–6) Peniagone lacinora Agatep, 1967: 53 –55, pl. 3 (figs 1–9)

Peniagone lugubris Théel, 1882. Madsen, 1953: 153 –155, figs 2–3 Peniagone purpurea. Gebruk, 1990: 111 –113, fig. 46 [synonymy]

Material. M 48/1­343: 2 specimens (ZSM 20043074).

Description. The body is more or less flat, with a distinct brim along the lateral edges of the body, continuous with the velum (Fig. 6 A). The two specimens are 37 and 55 mm long and 12 and 24 mm wide. Preserved they are purple to dark purple (tentacle discs and around mouth). The ventral mouth is situated on an anterior bulge­like enhancement, while the posterior anus opens dorsally above the posterior tube feet. Ten conspicuous tentacles encircle the mouth (larger specimen: 7 preserved, smaller specimen: 1 preserved). The tentacle discs are large, almost circular in outline, and have an irregular margin, due to several retractile lobes. The posterior three­fifths of the ventral sole are bordered by 7–8 pairs of conspicuous conical tube feet. From anterior to posterior, they continuously decrease somewhat in size and become closer to each other. The anterior tube feet are well separated and situated on the ventral side of the specimen, while the posterior ones are in contact and are contiguous with the lateral brim. The most posterior pair of tube feet is considerably smaller than the preceding ones. The dorsal velum, continuous with the lateral brim, is conspicuous and composed of four basally fused papillae. The papillae are long and slender and the anterior pair is about twice as long as the posterior pair. A short distance from the velum there is a variable number of pairs of free papillae (1–3).

Calcareous deposits of the body wall are primary crosses with a well developed stem, more or less bent arms and four high apophyses, one on each arm (Fig. 6 B). The arms and apophyses of the primary crosses are irregularly equipped with small spines. Usually, the apophyses are shorter than the arms, but not always. In addition to the common primary crosses, in the tentacles also large spinous crosses and rods are present (Fig. 6 C). Similar spinous crosses also do occur in the tube feet (Fig. 6 D).

Remarks. In his revision of the family Elpidiidae, Gebruk (1990) synonymised the two species P. purpurea and P. ferruginea, till then recognised as valid (e.g. Hansen 1975). According to Gebruk, P. purpurea is characterised by the following features: calcareous deposits of dorsal body wall primary crosses of two types, both with four apophyses, which are usually shorter than arms, in one type arms are bent, while in the other type arms are about horizontal; dorsal velum large, papillae of velum free in their distal part. The current specimens fit with this diagnosis regarding the morphology of the dorsal velum, which is formed by four basally fused papillae. However, with reference to the supposed two types of primary crosses in the dorsal body wall, the current specimens differ somewhat. There are primary crosses with conspicuously bent arms as well as crosses with almost horizontal arms, but there are also intermediate forms with more or less bent arms. Likewise variable primary crosses are also present in the ventral body wall of both specimens investigated. It seems, that in reality these two " types " represent the extremes of a continuous range.

Distribution. (Fig. 7) Northern and southern Atlantic Ocean, southern Indian Ocean, northern Pacific Ocean and Southern Ocean, 2800–5880 m (Agatep 1967; Gebruk 1990; Grieg 1921; IFREMER BIOCEAN; Madsen 1953; Perrier 1902; Théel 1882; herein).