Hesione keablei, Salazar-Vallejo, 2018

Salazar-Vallejo, Sergio I., 2018, Revision of Hesione Savigny in Lamarck, 1818 (Annelida, Errantia, Hesionidae), Zoosystema 40 (12), pp. 227-325 : 270-272

Hesione keablei n. sp.

( Figs 26 , 27 )

urn:lsid:zoobank.org:act:B5ECB11E-9705-4301-A130-8A2D99D19BB3

Hesione splendida ? – Monro 1931: 11-12, Textfig. 6.

TYPE MATERIAL. — Australia. Holotype, AM W.2939, Queensland, June Reef , outer barrier reef (14°17’S, 143°46’E), 1928, British Great Barrier Expedition 1928-1929.

ADDITIONAL MATERIAL. — Australia. 1 specimen, AM 4409 , Little Upolo Cay, 38 km NNE off Cairns, Queensland, Australia; under coral rocks, 19.VII.1970, I. Loch coll. [complete, distorted by compression into small container; colorless, integument shiny; body 43 mm long, 5 mm wide; left parapodia of chaetigers 9 and 11 removed for observation (kept in vial); anterior eyes twice larger than posterior ones; right antennae remaining, digitate, tip eroded, 3-4 times as long as wide, left one lost; tentacular and parapodial cirri on site; dorsal cirrophore 4 times as long as wide, cirrostyles basally cylindrical, smooth, medially annulated, distally articulated; neuraciculae thick, black; acicular lobe double, tines digitate, of similar size; ventral cirri smooth to irregularly contracted, surpassing chaetal lobe; about 25 neurochaetae per bundle, each honey-colored, most without blades; blades bidentate, subdistal tooth smaller, margin denticulated; no guards; oocytes 70-80 µm in diameter] .

Indonesia, Sulawesi. 1 specimen, UF 38 , Southern Outer Barrier Reef (-0.491111, 122.0725; 00°29’27.9996”S, 122°04’21.0000”E), barrier reef, 1 -3 m depth, 22.IX.1999, G. Paulay coll. [44 mm long, 6 mm wide; body with anterior region markedly contracted, prostomium hidden under tentacular segment; longest tentacular cirri reach chaetiger 3; dorsal cirri shorter than body width (excluding parapodia); acicular lobe double, both tines long, sometimes about of the same length, blunt; neuraciculae black, one very thick, the other very thin; neurochaetae about 20 per bundle, with guards and teeth eroded, subdistal tooth minute, guard approaching distal tooth, but mostly broken; probably easily eroded in older specimens]. New Caledonia. 1 specimen, MNHN MUSORSTOM 100 DW, SMIB 5 Expedition, Ride de Norfolk, 200 km SE off Nouméa , Sta. 100DW (23°22.9’S, 168°05.2’E), 80 -120 m depth, 14.IX.1989, B. Richer coll. [29 mm long, 3 mm wide; slightly macerated, laterally bent; body without pigmentation, anterior eyes twice as large as posterior ones, acicular lobe double, tines blunt, of similar size; neurochaetal blades bidentate, eroded, a few blades with tiny guards]. French Polynesia. 1 specimen, UF 23 , Tuamotu Islands, Rangiroa Atoll, circa 1 km S of NW Point of Atoll , off Motu Maeherehonae (-14.928666, -147.857833; 14°55’43.1976”S, 147°51’28.1988”W), outer reef slope, under rocks, 6 -12 m depth, 10.XI.2001, G. Paulay coll. (body partially dehydrated without pigmentation; eyes and antennae minute; dorsal cirri multiarticulate, ventral cirri smooth; acicular lobe double, each tine very long, slightly capitate; neurochaetal blades short, subapical tooth minute, all guards broken).

ETYMOLOGY. — This species is being named after Stephen Keable, Curator of Marine Annelids, Australian Museum, Sydney, in recognition of his unrestricted support to our research activities in Mexico and elsewhere. The name is a noun in genitive ( ICZN 1999: art. 31.1.2).

DISTRIBUTION. — Indonesia to the French Polynesia, in coral to mixed substrates, mostly in shallow water but one specimen found in 80-120 m depth.

DIAGNOSIS. — Hesione with prostomium wider posteriorly; parapodia with dorsal cirri basally cylindrical, dorsal cirrophore twice as long as wide; larger acicula blackish; acicular lobe double; neurochaetal blades bidentate, subdistal tooth smaller than distal one, but without guards.

DESCRIPTION

Holotype, AM W.2939, complete, bent ventrally, colorless in ethanol; integument smooth, shiny ( Fig. 26A ); a midventral dissection up to chaetiger 10 previously made; several parapodia already removed. Body subcylindrical, tapered posteriorly, 58 mm long, 5 mm wide; left parapodium of chaetiger 4 removed for observation (kept in vial).

Prostomium trapezoidal, about twice as long as wide, anterior margin truncate, lateral margins progressively expanded ( Fig. 26B ), posterior margin covered by anterior margin of tentacular segment, longitudinal depression shallow, extended along posterior prostomial half. Antennae long, medially widened, 5-6 times as long as wide. Eyes pale brown, anterior ones twice as large and more distant to each other than posterior eyes.

Tentacular cirri smooth, longest ones (without tips) reaching chaetiger 3. Lateral cushions projected, smooth, entire along anterior body half, barely separated into two sections along posterior body half.

Parapodia with chaetal lobes truncate ( Fig. 26C ), most dorsal cirri without tips; dorsal cirrophores twice as long as wide, cirrostyles basally cylindrical, annulated, medially annulated, distally articulated; shorter than body width. Ventral cirri smooth, surpassing chaetal lobe.

Aciculae blackish, thick, probably two. Acicular lobes double, tines digitate, blunt, of similar size ( Fig. 26C [inset]).

Neurochaetae about 25 neurochaetae per bundle, honeycolored, most without blades, blades bidentate, 3-4 times as long as wide, subdistal tooth smaller, margin denticulated; no guards.

Pharynx not exposed. Oocytes not seen.

Variation

One small specimen, MNHN-IA-PNT98b (formerly jar Musorstom 100DW), herein regarded as conspecific is shown in figure 28. This identification takes into account a posteriorly expanded prostomium and well-developed lateral cushions ( Fig. 27A ), poorly defined eyes ( Fig. 27B ), dorsal cirrophores twice as long as wide and acicular lobes blunt, of similar size ( Fig. 27C ). However, there are two small differences. A few chaetal blades show a slightly longer tooth along its cutting edge ( Fig. 27D [inset]), and because they are in the same position where guards typically are, they could be regarded as tiny guards or as elongated teeth. Another difference refers to the depth where this specimen was found because it was collected in deeper water (80-120 m). To better define its status as the same or as an independent species requires more and better specimens, but it is herein regarded as conspecific.

REMARKS

Hesione keablei n. sp., together with H. beneliahuae n. sp., differ from all other species in the genus because their neurochaetal blades have no guards at all. These two species differ, however, because H. keablei n. sp. has dorsal cirrophores twice as long as wide, its prostomium is wider posteriorly, and the eyes are poorly defined, whereas in H. beneliahuae n. sp. the dorsal cirrophores are as long as wide, the prostomium is rectangular, and the eyes are well-defined.

Monro (1931: 11-12) recorded a similar species after a single specimen collected during the Great Barrier Reef Expedition, in Jukes Reef. He indicated it was a “well-preserved specimen measuring” 54 mm long, 5 mm wide, that it had “a square dorsal mark paler in color than the rest of the body”, and “two fingershaped retractile processes” as acicular lobe. For chaetal blades he emphasised: “I cannot find any trace of a chaetal guard on the blades.” Regretfully, this specimen was not found during a visit to the Natural History Museum, London. Monro (1931: 12) also referred to an earlier record by Pruvot (1930: 29). Pruvot found another large specimen (46 mm long) of an unidentified species whose chaetal blades did not have guards. This specimen differs from H. keablei n. sp., however, by having acicular lobes single, and long neurochaetal blades. So it may belong to another species, probably close to H. intertexta ; such a large specimen was not found in Paris, but other specimens from the same study were regarded as belonging to H. intertexta . The record by Fauvel (1922: 493) as H. pantherina of two colorless specimens collected in the Wallaby Archipelago (13°22’6.57”S, 141°41’40.83”E) could not be confirmed.

Figures

FIG. 26. — Hesione keablei n. sp., holotype, AM W.2939: A, anterior region, dorsal view; B, anterior end, dorsal view; C, chaetiger 4, left parapodium, anterior view; D, neurochaetal blades from the upper, medial and lower part (inset: close up of tip), and from a shorter chaetae showing acute teeth; E, posterior region, dorsal view. Scale bars: A, 2 mm; B, C, 0.7 mm; D, 20 µm; E, 1.8 mm.

FIG. 27. — Hesione keablei n. sp., non type specimen, MNHN-IA-PNT98b (formerly jar Musorstom 100DW): A, anterior region, dorsal view; B, prostomium, after Methyl green staining, dorsal view (arrows point to antennae); C, chaetiger 9, left parapodium, anterior view (inset: acicular lobe); D, same, neurochaetal blades (inset: close-up showing longer teeth along cutting edge). Scale bars: A, 0.8 mm; B, C, 0.2 mm; D, 15 µm.