Websterinereis pettiboneae, de Leon-Gonzalez, Jesus Angel & Balart, Eduardo F., 2016

de Leon-Gonzalez, Jesus Angel & Balart, Eduardo F., 2016, A new species of Websterinereis from the Gulf of California and redescription of Websterinereisfoli (Fauvel, 1930) (Annelida, Nereididae), ZooKeys 614, pp. 15-26 : 17-20

Taxon classification Animalia Phyllodocida Nereididae

Websterinereis pettiboneae sp. n. Figs 1, 2

Type material.

Holotype (UANL 7845) and 3 Paratypes (LACM-AHF Poly 9104), San Lorenzo Channel, La Paz Bay, Gulf of California, Mexico, Stn 12 (24°23'11.4"N, 110°18'55.5"W), July 2006.

Additional material.

Lorenzo Channel, La Paz Bay, Gulf of California, Mexico, (2 specimens), Stn 28 (24°23'12"N, 110°18'55.1"W), April 2006; (1 specimen), Stn 5 (24°23'12.2"N, 110°18'55.1"W), July 2006; (2 specimens), Stn 27 (24°23'12"N, 110°18'54.9"W), July 2006; (1 specimen), Stn 1 (24°23'12.8"N, 110°18' 54.2W), October 2006; (4 specimens, 2 epitokes), Stn 3 (24°23'12.8"N, 110°18'54.8"W), October 2006; (1 specimen), Stn 5 (24°23'12.2"N, 110°18'55.1"W), October 2006; (12 specimens), Stn 9 (24°23' 11.7N, 110°18'55.4"W), October 2006; (1 epitokous specimen), Stn 12 (24°23'11.4"N, 110°18'55.5"W), October 2006; (1 specimen), Stn 13 (24°23'11.5"N, 110°18'54.8"W), October 2006; (3 specimens), Stn 3 (24°23'12.8"N, 110°18'54.8"W), 3 October 2007; (3 specimens), Stn 9 (24°23' 11.7N, 110°18'55.4"W), 3 October 2007; (1 specimen), Stn 13 (24°23'11.5"N, 110°18'54.8"W W), 3 October 2007.

Description.

Holotype complete with restricted blackish pigmentation (Fig. 1A); prostomium with anteriorly truncate, extended dark area, leaving pale mid-dorsal thin band, not reaching anterior prostomial margin; palpophores with some pigmentation over external, subdistal surfaces; tentacular segment with continuous dorsal transverse wide band, reduced to progressively thinner bands along anterior and posterior segmental margins.

Body 12 mm long, 0.8 mm wide including parapodia, with 60 chaetigers. Prostomium subpyriform, longer than wide. Two pairs of black oval eyes in rectangular arrangement, distal pair with larger lens than proximal pair. Antennae tapered, extended beyond tips of palpostyles. Palps and palpostyles globose. One apodous anterior segment, 1.5 times longer than first chaetiger. Tentacular cirri short, tapered, longest reaching chaetiger 3 (Fig. 1A).

Pharynx with brown jaws, each with six teeth. Maxillary ring lacking paragnaths or papillae; oral ring with subconical papillae in area VI, and five globose papillae in line along areas VII–VIII.

Parapodia of first two chaetigers uniramous, remainder biramous. In anterior parapodia notopodia with subulate dorsal ligules, notopodial prechaetal lobes short triangular, and ventral ligules subtriangular, rounded distally; neuropodia with postchaetal lobes distally rounded, superior and inferior lobes not distinct, ventral ligules subulate. Dorsal cirri inserted basally, four times longer than ventral cirri, and 1.4 times than notopodial dorsal ligule (Fig. 1B). Median parapodia with digitiform dorsal ligules, notopodial prechaetal lobes reduced to small ridge; ventral ligules triangular; neuropodial postchaetal lobes subconical, ventral ligules reduced to small subulate protuberance. Dorsal cirri three times longer than ventral cirri (Fig. 1C). Posterior parapodia with dorsal ligules reduced, half as long as those of median parapodia, notopodial prechaetal lobes absent, ventral ligules triangular; neuropodial postchaetal lobes subtriangular, ventral ligules reduced, conical. Dorsal cirri 2.5 times longer than ventral cirri, with red pigmented glandular areas (Fig. 1D).

Anterior parapodia with notochaetae represented by four supra-acicular homogomph spinigers; supra-acicular neurochaetae include two homogomph spinigers and two heterogomph falcigers with thick handle and short triangular blade (Fig. 1E); infra-acicular neurochaetae represented by five heterogomph falcigers (Fig. 1F). Median parapodia with supra-acicular notochaetae represented by two supra-acicular homogomph spinigers; supra-acicular neurochaetae include two homogomph spinigers and one heterogomph falciger with thick handle and short triangular blade (Fig. 1G), infra-acicular neurochaetae represented by four heterogomph falcigers (Fig. 1H). Posterior parapodia with notochaetae represented by two supra-acicular heterogomph spinigers; supra-acicular neurochaetae with a single heterogomph falciger (Fig. 1I); infra-acicular neurochaetae three heterogomph falcigers, similar to supra-acicular falcigers.

Pygidium with terminal anus and two anal cirri.

Epitokous female. Best preserved specimen with 64 chaetigers, 9 mm long and 0.5 mm wide (excluding parapodia). Prostomium pentagonal, wider than longer, with frontal median dorsal groove. Antennae minute, shorter than anterior end of palpi. Two pairs of eyes in trapezoidal arrangement, anterior pair enlarged, oval in shape, posterior pair rounded in shape. Biarticulate palps globose, each with spherical palpostyle. Tentacular ring with four pairs of tentacular cirri, posterodorsal pair extending back to anterior margin of sixth chaetiger (Fig. 2 A). Pharynx equal to non-epitokous specimens.

Body divided into unmodified anterior region and a heteronereidid region; parapodia of first 19 chaetigers similar of those of atokous specimens (Fig. 2B). Parapodia of heteronereidid region moderately compressed. Notopodia formed by dorsal cirrus accompanied by two basal lobes, a small notopodial dorsal ligule, and subulate ventral ligule; with two enlarged postchaetal lobes. Neuropodia with superior and inferior lobes fused, foliose postchaetal lamellae present; neuropodial ventral ligule subtriangular in median parapodia and digitate in posterior parapodia. Ventral cirri long and thin, accompanied by two basal lobes (Fig. 2 C–D). Last eleven chaetigers unmodified. Normal chaetae replaced on chaetigers 20 by natatory chaetae with broad, paddle-shaped appendages, inner margin slightly denticulate (Fig. 2E). Anterior parapodia with four homogomph spinigers in notopodial supra-acicular position; neuropodia with three supra-acicular homogomph spinigers and one heterogomph falciger; infra-acicular chaetae five heterogomph falcigers. Median parapodia with two homogomph spinigers and 15-18 natatory chaetae in notopodial supra-acicular position; neuropodial infra-acicular chaetae two homogomph spinigers and two heterogomph falcigers, with 14-15 natatory chaetae. Posterior parapodia with two heterogomph falcigers and 13-14 natatory chaetae in notopodial supra-acicular position; neuropodial infra-acicular chaetae one homogomph spiniger, one heterogomph falciger, and 18-20 natatory chaetae.

Pygidium similar to those of atokous specimens.

Etymology.

Specific name is in honor of Marian H. Pettibone for her great work on increasing the knowledge of polychaetes.

Remarks.

Websterinereis pettiboneae sp. n. resembles Websterinereis foli in the shape of the compound falcigers, although there is greater variation in the shape of compound falcigers in Websterinereis foli . These species differ in the following features: Websterinereis pettiboneae has longer tentacular cirri reaching chaetiger 3, notopodial prechaetal lobes are triangular, and notopodial dorsal and ventral ligule are progressively smaller in posterior parapodia. In Websterinereis foli the longest tentacular cirri reaches chaetiger one, with a thin, cirriform prechaetal notopodial lobe inserted at the base of the notopodial ventral ligule, and the dorsal and ventral ligule increasing slightly in posterior parapodia.

Distribution.

Websterinereis pettiboneae sp. n. is known only from Canal de San Lorenzo, La Paz Bay, Gulf of California, Mexico.

Density.

The mean density of Websterinereis pettiboneae sp. n. varied from 2.5 ± 2.5 individuals per m2, in May 2005, to a maximum of 587.5 ± 110.8 individuals per m2 recorded in July 2008 (Fig. 3). In general, densities were higher during the warmer and colder months and the lower densities between them; it suggests two peaks of recruitment for this species in the rocky reefs of southern Gulf of California. However, no significant relationship between temperature or salinity with worm density could be established.