Hesione reticulata von Marenzeller 1879

Hesione reticulata von Marenzeller, 1879

(Fig. 47)

Hesione reticulata von Marenzeller, 1879: 129-131, pl. 3, fig. 4. — Izuka 1912: 192-194, pl. 2, fig. 7. — Imajima & Hartman 1964: 80. — Jimi et al. 2017: 32-37, figs 1-3.

Hesione pantherina – Fauvel 1937: 59, 60. — Wu et al. 1975: 75, pl. 2, figs 7, 8 (non Risso, 1826).

Hesione splendida – Hessle 1925: 13, 15. — Imajima 2003: 132, 134, fig. 78 (non Savigny in Lamarck, 1818).

NON- TYPE MATERIAL. — New Caledonia. 1 specimen, UF 151, Noumea, Île Nou, Anse Kuendo, sand and reef slope, fringing rock, under rocks, 0-3 m depth, 27.I.1999, G. Paulay coll.

DISTRIBUTION. — Japan to New Caledonia, in shallow water mixed bottoms.

DIAGNOSIS. — (Modif. after Jimi et al. 2017) Hesione with rectangular prostomium; parapodia with dorsal cirri basally cylindrical, dorsal cirrophore twice as long as wide; larger acicula blackish; acicular lobe double, tines short, massive, blunt, upper tine slightly longer than lower one; neurochaetal blades bidentate, 3-5 times as long as wide; subdistal tooth smaller; guards approaching distal tooth.

DESCRIPTION

Specimen macerated, UF 151, body wall broken along a posterior right section (removed for molecular analysis); body colorless in ethanol, progressively wider, tapered posteriorly, 52 mm long, 7 mm wide.

Prostomium as wide as long, anterior margin truncate, lateral margins rounded, medially expanded, posterior margin exposed, posterior depression as long as ¼ prostomial length. Antennae not visible. Eyes colorless.

Tentacular cirri macerated, transparent, tips broken, reaching chaetiger 3. Lateral cushions projected, smooth, probably by maceration.

Parapodia with chaetal lobes projected, truncate, twice as long as wide (Fig. 47B, D); dorsal cirri with cirrophores too relaxed, four times as long as wide, cirrostyles basally cylindrical, annulated medially and distally, as long as body width (excluding parapodia). Ventral cirri smooth, surpassing chaetal lobe.

Neuraciculae blackish. Acicular lobe double (Fig. 47B, C [insets], B, D), tines digitate, upper tine slightly longer than, or up to 1/3 longer than lower tine; in one median parapodium lower tine larger, probably a maceration artifact.

Neurochaetae about 15 per bundle in anterior chaetigers (Fig. 47C), about 20 in median chaetigers (Fig. 47E), handles honey-colored, blades bidentate, at a certain angle from handle, most eroded or with adsorbed particles, decreasing in size ventrally, 5-8 times as long as wide in anterior chaetigers (Fig.47D), 4-5 times in posterior chaetigers (Fig. 47C); subdistal teeth smaller, guards, if complete, approaching distal tooth.

Posterior region tapered into a blunt cone; pygidium macerated, relaxed, with 7 blunt papillae.

Pharynx exposed; dorsal papilla rounded, as long as wide. Oocytes not seen.

Pigmentation

Living specimen (Fig. 47A) with longitudinal, irregular brownish bands, with oval pale areas in each chaetiger and over central areas of lateral cushions; bands extending towards lateral cushions.Tentacular, dorsal cirri and neuropodial lobes pale. A middorsal reddish line showing the dorsal blood vessel; middorsal lines slightly darker than the others.

REMARKS

Hesione reticulata von Marenzeller, 1879 resembles, as indicated in the key below, H. picta Müller, 1858. These two species differ in two main features related to their integument and pigmentation. In H. reticulata integument is rugose because there are transverse and longitudinal striae, and living specimens have a complex, reticulate pigmentation pattern, whereas in H. picta the dorsum is rather smooth, annulated, but without longitudinal striae, and living specimens have transverse dark brown bands. On the other hand, by their pigmentation pattern, H. reticulata resembles H. intertexta Grube, 1878 by having longitudinal lines throughout the body, and short antennae. However, because H. reticulata has an acicular lobe double, it differs from H. intertexta that has a single acicular lobe. The species has been recently redescribed, a neotype was proposed (Jimi et al. 2017), and the acicular lobe was confirmed as double. The specimens recorded by Imajima (2003: 132), albeit partially, might belong to this species; in one of his illustrations, a thick acicular lobe can be noted, which can be confused with a single tine, but as shown elsewhere (Jimi et al. 2017), the shorter tine is difficult to be observed.