Hesione harrisae, Salazar-Vallejo, 2018

Salazar-Vallejo, Sergio I., 2018, Revision of Hesione Savigny in Lamarck, 1818 (Annelida, Errantia, Hesionidae), Zoosystema 40 (12), pp. 227-325 : 257-259

Hesione harrisae n. sp.

( Fig. 17 )

urn:lsid:zoobank.org:act:E5DDED97-BF16-483F-BC1F-04FA0C33294C

TYPE MATERIAL. — Caribbean Sea, Puerto Rico. Holotype, LACM 8631 , Mayaguez, Cabo Rojo Light , 20.I.1946, W. G. Hewatt coll.

ETYMOLOGY. — This species is named after Leslie Harris, Collection Manager of the Allan Hancock Polychaete Collection, in the Los Angeles County Museum of Natural History, in recognition of her knowledge of polychaetes in general, and because of her longlasting and enthusiastic support to our research requests. The name is a noun in genitive ( ICZN 1999: art. 31.1.2).

DISTRIBUTION. — Only known from the type locality in Puerto Rico, Caribbean Sea .

DIAGNOSIS. — Hesione with prostomium laterally curved; parapodia with dorsal cirri basally cylindrical, dorsal cirrophore twice as long as wide; larger acicula blackish; acicular lobe single, tapered; neurochaetal blades unidentate, 6-8 times as long as wide; guards approaching distal tooth.

DESCRIPTION

Holotype, LACM 8631, complete, subcylindrical, tapered posteriorly, without pigmentation ( Fig. 17A ) in ethanol; several dorsal or ventral cirri lost, most neurochaetal blades lost; right parapodia of chaetigers 5 and 6, and left parapodium of chaetiger 11 removed (6 + 11 in vial). Body straight, 30 mm long, 3 mm wide. Prostomium as wide as long, anterior margin truncate with a shallow depression, lateral margins rounded, slightly expanded posteriorly ( Fig. 17B ), posterior margin deeply cleft about as 1/3 prostomial length (reaching level of posterior eyes), lon- gitudinal depression indistinct. Antennae minute, rounded, about as long as wide, 1/3 as long as interocular distance. Eyes feebly pigmented, anterior eyes darker, twice as large as, and more separated than posterior eyes.

Tentacular cirri damaged, twisted. Lateral cushions slightly projected, without distinctive divisions in anterior chaetigers, in posterior ones barely separated into two sections, surface smooth.

Parapodia with chaetal lobes wider than high, truncate ( Fig. 17C ); dorsal cirri with cirrophores twice as long as wide; cirrostyle cylindrical, smooth basally, articulated medially and distally, as long as body width (details undefined, tips eroded or broken). Ventral cirri smooth, surpassing chaetal lobe.

Neuraciculae blackish, larger one markedly thicker and darker than smaller one. Acicular lobe single, tapered, long, about 10 times longer than lower, rounded tine; upper tine as long as chaetal bundle width ( Fig. 17C [inset]).

Neurochaetae about 30 per bundle, blades unidentate (sometimes a tiny subdistal tooth present), blades at a certain angle from handles, decreasing in size ventrally, 6-8 times as long as wide, each with a distal tooth, guards often broken, if entire, approaching distal tooth ( Fig. 17D, E ).

Posterior region tapered into a blunt cone ( Fig. 17F ); pygidium swollen (now collapsed), integument slightly eroded, anus with 6 blunt papillae.

Pharynx everted, with three distinctive rings of similar length, margin smooth, slightly eroded; dorsal papillae rounded, about as long as wide. Oocytes about 100 µm in diameter.

REMARKS

Hesione harrisae n. sp. could be confused with H. praetexta Ehlers, 1887 , reinstated (see below), another Grand Caribbean species because both have markedly different acicular lobes, and thin, long neurochaetal blades. However, in H. harrisae n. sp. the upper acicular lobe is at least 5 times as long as the lower one, and its neurochaetal blades are mostly unidentate, whereas in H. praetexta the upper acicular lobe is about 3 times longer, and the neurochaetal blades are bidentate. Further, H. harrisae n. sp. was identified as H. praetexta because both have a markedly longer acicular lobe, but in H. praetexta blades are bidentate, whereas in H. harrisae n. sp. they are unidentate.

As indicated in the key below, there is another species with unidentate neurochaetal blades: H. osbornae n. sp. (see below). However, there are two main differences between these two species: in H. harrisae n. sp. the neurochaetal blades are 6-8 times as long as wide, and their guards reach distal teeth, whereas in H. osbornae n. sp. neurochaetal blades are about 15 times as long as wide, and guards surpass distal teeth.

Figures

FIG. 17. — Hesione harrisae n. sp., holotype, LACM 8631: A, anterior region, dorsal view; B, anterior end, dorsal view, pharynx exposed (arrow points to dor- sal papilla); C, chaetiger 11, right parapodium, anterior view (inset: acicular lobe); D, chaetiger 6, left parapodium, neurochaetal blades (insets: tips of blades); E, chaetiger 11, right parapodium, neurochaetal blades (insets: tips of blades); F, Posterior region, dorsal view. Scale bars: A, 1 mm; B, 0.6 mm; C, 0.3 mm; D, E, 50 µm; F, 1.4 mm.