Hesione beneliahuae, Salazar-Vallejo, 2018

Salazar-Vallejo, Sergio I., 2018, Revision of Hesione Savigny in Lamarck, 1818 (Annelida, Errantia, Hesionidae), Zoosystema 40 (12), pp. 227-325 : 238-241

Hesione beneliahuae n. sp.

( Figs 5 , 6 )

urn:lsid:zoobank.org:act:1862BD5B-7FA6-49AD-9A24-05F9D55B429E

TYPE MATERIAL. — Western Indian Ocean. Mascarene Islands. Holotype. UF 658 , Réunion Island, Saint-Leu, Sec Jaune (-21.153333, 55.28111666; 21°09’11.9988”S, 055°16’52.0200”E), 17.VIII.2007, 6- 15 m depth, H. Bruggemann, N. Hubert, F. Michonneau & G. Paulay coll.

ADDITIONAL MATERIAL. — Red Sea , Saudi Arabia. 1 specimen, UF 3658 , offshore of Farasan Banks, Dolphen Lagoon (19.00533, 40.14815; 19°00’19.1880”N, 040°08’53.3400”E), reef lagoon, barrier reef flat, and fore reef wall, 4.III.2013, 1- 25 m depth, A. Anker, P. Norby & G. Paulay coll. [21 mm long, 2 mm wide; no pigmentation] .

Persian Gulf, Saudi Arabia. 1 specimen, UF 4222 , Abu Sahim (22.65865, 38.88435; 22°39’31.1400”N, 038°53’03.6600”E), 5-9 m [without posterior end (removed for molecular analysis); 22 mm long, 3 mm wide, 13 chaetigers; longest tentacular cirri with broken tips, reach chaetiger 3; dorsal cirri longer than body width, including parapodia; acicular lobes of different size along body, subequal in some anterior and posterior chaetigers, in others upper tines twice longer or 1/3 longer than lower ones] .

ETYMOLOGY. — This species is named to honor the late Dr M. Nechama Ben-Eliahu, in recognition of her many publications on taxonomy of polychaetes, and her efforts supporting scientific collections ( Chipman & ten Hove 2014). The name is a noun in genitive ( ICZN 1999: art. 31.1.2).

DISTRIBUTION. — Western Indian Ocean, including the Red Sea, the Persian Gulf and La Réunion Island, in shallow water (1-25 m) mixed or sandy bottoms.

DIAGNOSIS. — Hesione with prostomium rectangular; parapodia with dorsal cirri basally cylindrical, dorsal cirrophore as long as wide; larger neuracicula blackish; acicular lobe double, upper tine slightly

longer than lower one; neurochaetal blades bidentate, subdistal tooth smaller than distal one, but without guards.

DESCRIPTION

Holotype, UF 658, complete, whitish, shiny, poorly defined pale brown bands in prostomium, and barely visible dorsally along chaetigers 1-3 ( Fig. 5B ) in ethanol; slightly distorted by fixation into a small container; cirri corrugated, many dorsal cirri missing; a posterolateral dissection on right side removed parapodia of chaetigers 11-15 for molecular analysis. Body subcylindical, tapered posteriorly, 34 mm long, 3.5 mm wide.

Prostomium rectangular, slightly as long as wide, anterior margin truncate, lateral margins straight, posterior margin barely exposed, longitudinal depression very shallow, restricted to prostomial posterior fourth. Antennae long, digitate, 3-4 times as long as wide. Eyes brownish, anterior ones twice larger, and slightly more separated than posterior ones ( Fig. 5C ).

Tentacular cirri irregularly contracted, difficult to be pulled posteriorly; relative length to anterior chaetigers unknown. Lateral cushions barely projected, some divided into anterior and posterior sections, others with three sections.

Parapodia with chaetal lobes truncate ( Fig. 5D ), most dorsal cirri lost; dorsal cirrophores about as long as wide, cirrostyles basally smooth, cylindrical, medially annulated, distally articulated; shorter than body width. Ventral cirri basally smooth, irregularly contracted medially and distally, surpassing chaetal lobe.

Neuraciculae blackish, two, larger one 3 times thicker than smaller one. Acicular lobes double, tines digitate; upper one tapered, slightly longer than lower one, blunt, medially wider ( Fig. 5D [inset]).

Neurochaetae about 20 per bundle, handles honey-colored, blades bidentate, at a certain angle from handle, 3-5 times as long as wide, decreasing in size ventrally, each with smaller subdistal tooth, sharp to blunt, about 1/3 as wide as larger tooth, often eroded to blunt tips; guards completely absent ( Fig. 5E ).

Posterior region tapered into a blunt cone ( Fig. 5F ); pygidium smooth, anus projected with about 5 lobate papillae.

Pharynx not exposed. Oocytes not seen.

Pigmentation

Body reddish, with reddish bands dorsally over a whitish background, extended over lateral cushions ( Fig. 5A ), but lateral pigmentation better defined along chaetigers 1-7; reddish bands wide, with anterior margin well defined, posterior margin irregular, each band positioned along chaetal lobes, but leaving a pale, oval area over dorsal cirri; bands progressively longer along chaetigers 1-7, thereafter becoming paler medially along chaetigers 8-9, and from chaetiger 10 the central area paler such that the wide transverse bands become progressively separated into two thinner transverse bands. Prostomium reddish with a pentagonal whitish, central area. Tentacular, dorsal cirri and chaetal lobes pale.

Variation

A small specimen (UF 3658) has anterior eyes only slightly larger than posterior ones, and acicular lobes of different length along the body; in chaetigers 1-3 acicular lobes are subequal, in chaetigers 4-7 upper tines are about twice longer than lower ones, and in other chaetigers lower tines are 1/3 as long as the upper ones. Chaetal blades lack guards completely and marginal teeth are visible in upper chaetae ( Fig. 6A ), or barely visible at all ( Fig. 6B [inset]); a newly emerged neurochaetae, still with its transparent sheet ( Fig. 6C [inset]) confirms the complete absence of guards.

REMARKS

Hesione beneliahuae n. sp. resembles H. splendida Savigny in Lamarck, 1818 because they both have a shiny integument, and both are present in the Western Indian Ocean. However, they differ in two main features: acicular lobes and neurochaetal blades. In H. beneliahuae n. sp. acicular lobes are double, both tines blunt, of similar length, or lower tine shorter, and neurochaetal blades have no guards at all, whereas in H. splendida acicular lobes are single, and neurochaetal blades have guards approaching distal tooth.

On the other hand, H. beneliahuae n. sp. resembles H. keablei n. sp. (see below) because both species have blades without guards. However, they differ because in H. beneliahuae n. sp. dorsal cirrophores are as long as wide, and its prostomium is rectangular with well-defined eyes, whereas in H. keablei n. sp. the dorsal cirrophores are twice as long as wide, and its prostomium is wider posteriorly, with poorly defined eyes.

Another similar species is present in the Gulf of Manaar. A juvenile specimen (MNHN-IA-PNT90a [formerly jar 372]; 12 mm long, 2 mm wide), probably collected with other specimens reported by Fauvel (1929) from Krusadai Island, was found in a Tubipora mass. This species also has acicular lobe double, and neurochaetal blades without guards. It is regarded as a different species because its anterior eyes are displaced posteriorly, diffuse, and markedly as wide as long, as two brownish short, lateral transverse bands. The specimen is macerated and better material is needed to formally describe the species.

Figures

FIG. 5. — Hesione beneliahuae n. sp., holotype, UF 658:A, living specimen, dorsal view, head to the right, B, anterior region, dorsal view;C, anterior end, oblique dorsal view; D, chaetiger 8, left parapodium, anterior view (inset: acicular lobe); E, same, blades of upper, medial and lower neurochaetae (inset: lower blade tip); F, posterior region, dorsal view. Scale bars: A, 3.5 mm; B, 1.8 mm; C, 0.5 mm; D, 0.4 mm; E, 25 µm; F, 1.5 mm.

FIG. 6. — Hesione beneliahuae n. sp., non-type specimen, UF 3658, chaetiger 10, right parapodium, neurochaetal blades: A, upper chaetae, one with eroded subdistal tooth; B, lower chaetae, with entire teeth (inset: close-up of teeth); C, newly emerged blade, still covered with transparent sheet (inset: close up of teeth). Scale bars: A, 15 µm; B, C, 12 µm.