Nicon orensanzi, Leon-Gonzalez, Jesus Angel de & Trovant, Berenice, 2013

Leon-Gonzalez, Jesus Angel de & Trovant, Berenice, 2013, A new species of Nicon Kinberg, 1866 (Polychaeta, Nereididae) from Ecuador, Eastern Pacific, with a key to all known species of the genus, ZooKeys 269, pp. 67-76 : 69-73

Nicon orensanzi sp. n. Figures 2, 3

Material examined.

Holotype (LACM-AHF 4999), Paratype (LACM-AHF 5000) and Paratype (UANL 7840) collected at Bunche beach (0°39'01.98"N, 80°03'55.01"W), Esmeraldas Province, Ecuador, March 21 2009, coll. Berenice Trovant and Santiago Tineo. Additional material: seven anterior fragments, same data as holotype; two complete specimens and three anterior fragments, Cabo San Francisco beach (0°38'16.35"N, 80°3'14.07"W), Esmeraldas Province, Ecuador, March 20 2009, coll. Berenice Trovant and Santiago Tineo.

Description.

Holotype incomplete posteriorly, with 85 chaetigers, 19mm long, 1.4mm wide. Prostomium pyriform, with frontal cleft extending to middle of prostomium. Two pairs of eyespots in trapezoidal arrangement, anterior pair slightly larger, with lenses. Pair of small cirriform antennae extending slightly beyond palps. Palps biarticulate, globose, with subspherical palpostyles. Peristomium longer than next segment, with four pairs of short tentacular cirri, longest reaching chaetiger two (Figs 2A, 3A). Pharynx lacking papillae or paragnaths, armed with pair of toothed mandibles (Fig. 3B). Anterior notopodia with short cirriform dorsal cirri, subtriangular dorsal ligule, and subulate notopodial ventral ligule. Small triangular prechaetal lobe, restricted to limited number of anterior chaetigers, reducing in size posteriorly, last present about chaetigers 28-30. Anterior neuropodia with superior and inferior lobe, subulate ventral ligule, ventral cirrus with inflated base (Figs 2B, 3C), postchaetal neuropodial lobe subulate, present in first 18 chaetigers, not visible in anterior view. Median and posterior notopodia with dorsal ligule long cirrus-like; prechaetal lobe absent, notopodial ventral ligule triangular, decreasing in size in posterior chaetigers. Median and posterior neuropodia with superior and inferior lobes poorly defined, neuropodial postchaetal lobe absent, neuropodial ventral ligule subulate, decreasing in size in posterior chaetigers until disappearing completely, ventral cirri cirriform, shorter than dorsal one (Figs 2 C–D, 3 D–E). All notochaetae homogomph spinigers, with long, thin blades. Anterior supracicular neurochaetae 6 long-bladed homogomph spinigers superiorly; 6 short-bladed heterogomph spinigers inferiorly. Anterior infracicular chaetae homogomph spinigers with long blade, and sesquigomph falcigers with anterior part ending in a blunt tooth (Fig. 2E). Median and posterior supracicular neurochaetae with long-bladed homogomph spinigers. Infracicular neurochaetae with a few homogomph spinigers superiorly, and sesquigomph falcigers inferiorly, anterior end sharper (Figs 2 F–G, 3F). Pygidium lacking in holotype, with terminal anus and two thin lateral cirri on others specimens.

Type locality.

Bunche beach, Esmeraldas Province, Ecuador

Distribution.

This species is only known from Bunche and Cabo San Francisco beaches, Esmeraldas Province, Ecuador.

Discussion.

Of the six species originally included in the genus Nicon by Kinberg (1866) two have been transferred to other genera ( Nicon eugeniae , currently Nereis eugeniae from Strait of Magellan and Nicon loxochini , currently Platynereis magalhensis from Strait of Magellan) and three species are considered indeterminable due to their incomplete descriptions and the poor condition of the available syntypes ( Nicon maculata from La Plata, Argentina, Nicon pictus from Brazil, Nicon tahitianus from Tahiti, and Nicon virgini from Strait of Magellan) (Pettibone, 1971). Of these species, only Nicon maculata is considered valid at the present time. No type species was designated by Kinberg. Hartman (1949) designated Nicon pictus as the type species, even though she did not provide a diagnosis or figures. Pettibone (1971) later revised the genus and designated Nicon maculata as the type species. Currently this genus consists of ten species: Nicon maculata Kinberg, 1866 from La Plata, Argentina, Nicon moniloceras (Hartman, 1940) from Catalina Island, USA, Nicon aestuarensis Knox, 1951 from New Zealand, Nicon polaris Hartman, 1967 from the Antarctic peninsula, Nicon abyssalis Hartman, 1967 from the Antarctic peninsula, Nicon japonicus Imajima, 1972 from Japan, Nicon yaquinae Fauchald, 1977 from off the Oregon coast, USA, Nicon sinica Wu & Sun, 1979 from the Yellow Sea, Nicon rotunda Hutchings & Reid, 1990 from Australia, and Nicon pettibonae de León-González & Salazar-Vallejo, 2003 from the Loyalty Islands, New Caledonia. Pettibone (1971) also considered that Nicon abyssalis and Nicon polaris had doubtful generic affinities with Nicon ; however, we believe that Nicon abyssalis possesses the generic characters of Nicon and therefore should be included in the genus. Nicon polaris was described based on an epitoke; however, the possession of an expanded elytra-shaped dorsal cirrus in the chaetiger 7 makes it doubtful that it belongs to Nicon ; a similar structure is found in Kainonereis , currently a genus in inquirenda described from an epitokous stage by Chamberlin (1919).

Species of Nicon may be separated into two groups based on the presence or absence of notopodial prechaetal lobes. Those species with a notopodial prechaetal lobe are: Nicon aestuarensis , Nicon japonicus , Nicon polaris , Nicon rotunda , and Nicon sinica ; while Nicon abyssalis , Nicon maculata , Nicon moniloceras , Nicon pettibonae and Nicon yaquinae lack a superior notopodial lobe. Some important characteristics of Nicon species are listed in Table 1.

Nicon orensanzi sp. n. is a member of the first group but differs in its long, thin notopodial dorsal ligule in median and posterior parapodia. Nicon orensanzi sp. n. and Nicon pettibonae are the only species in the genus with neuropodial infracicular sesquigomph falcigers in all parapodia. These two species differ in the shape of their sesquigomph falcigers, the presence of heterogomph falcigers, and a reduced dorsal ligule in the posterior parapodia of Nicon pettibonae .

Etymology. The new species is dedicated to Dr. José María (Lobo) Orensanz, who has made significant contributions to the taxonomy of polychaetes and has been a mentor to the authors of this paper.