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A new species of Nicon Kinberg, 1866 from the east Pacific coast of Ecuador is described. The new species is characterized by a long, thin dorsal ligule on median and posterior parapodia and infracicular sesquigomph falcigers in the neuropodia. A key to all species of Nicon is provided.
Annelida, polychaetes, Nereididae, intertidal, Ecuador, taxonomy, systematics
Ecuador possesses a great variety of coastal environments resulting in a high diversity of marine species; however, taxonomic studies on marine invertebrates are few, especially in the case of the polychaetes. In Ecuador (excluding the Galapagos), only 29 families, 53 genera and 75 species of polychaetes have been recorded.
The importance of the family Nereididae is manifested by their high diversity and abundance in all marine substrates, occurring in all oceans from the supralittoral to the abyssal zone. This family includes 44 genera and approximately 460 valid species (de León-González, 2009). Nicon is one of the least species rich genera of Nereididae. The genus was first described by
Samples were collected in March 2009 (dry season) in the intertidal zone of two sandy beaches located in the Esmeraldas Province, northern Ecuador (Fig. 1). Bunche beach (0°37'55"N, 80°02'14"W) is a protected area characterized as a low energy beach, with soft sloping banks and very fine particle sand, and Cabo San Francisco beach (0°39'11"N, 80°04'10"W) is characterized as a high energy environment, subjected to frequent and severe storms, with high slopes. Fresh-water discharges affect both beaches. Sediment samples were sieved through a 1mm mesh. Specimens were fixed in 10% formalin and later preserved in 70% ethanol. Terminology of parapodial structures was taken from
Map of Ecuador indicating the sampling sites, Bunche and Cabo San Francisco Beaches.
Nicon maculata Kinberg, 1866.
Prostomium pyriform to subpyriform, with two pairs of eyespots, paired frontal antennae and biarticulate palps. Four pairs of tentacular cirri with distinct cirrophores, smooth or articulated. Parapodia of first two chaetigers subbiramous, notopodium represented by a single ligule with dorsal cirri at its base. Subsequent notopodia with dorsal and ventral ligules with or without a small notopodial prechaetal lobe decreasing in far posterior parapodia. Neuropodia with superior and inferior prechaetal lobes, digitiform or conical postchaetal lobe present or absent along body, and a ventral ligule which can be reduced in posterior parapodia; ventral cirri short, tapered. All notochaetae homogomph spinigers; neurochaetae homogomph, heterogomph or sesquigomph falcigers, may be accompanied by homogomph and heterogomph spinigers, and simple chaetae. Pygidium with paired anal cirri. Pharynx with paired mandibles, without paragnaths or papillae.
This generic diagnosis was modified from
urn:lsid:zoobank.org:act:149CDBF9-ACD0-4D7E-8407-BD8ADF3955C6
http://species-id.net/wiki/Nicon_orensanzi
Figures 2, 3Holotype (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.
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 2C–D, 3D–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 2F–G, 3F). Pygidium lacking in holotype, with terminal anus and two thin lateral cirri on others specimens.
Nicon orensanzi sp. n. Holotype. A Anterior end, dorsal view B Parapodium 10, anterior view C Parapodium 25, anterior view D Parapodium 60, anterior view E–G. Infracicular sesquigomph falcigers of parapodia 10, 25 and 50 respectively. Scale bars: A= 1 mm; B–D= 100 µ; E–G= 30µ.
Nicon orensanzi sp. n. Paratype (UANL 7840). A Anterior end, dorsal view B Mandibles; Holotype (LACM) C Parapodium 9, anterior view D Parapodium 29, anterior view E Parapodium 62, anterior view F Infracicular sesquigomph falcigers of parapodium 62. Scale bars: A= 1 mm; B= 0.1 mm; C–E= 100 µ; F= 30µ.
Bunche beach, Esmeraldas Province, Ecuador
This species is only known from Bunche and Cabo San Francisco beaches, Esmeraldas Province, Ecuador.
Of the six species originally included in the genus Nicon by
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.
Diagnostic features of the species of Nicon (modified from
Species | Neuropodial chaetae | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Supracicular | Infracicular | Notopodia | |||||||||||
TC | ho sp | he sp | ho f | he f | sf | ho sp | he sp | ho f | he f | sf | DL | PL | |
Nicon abyssalis | 2 | X | X | - | - | - | X | X | - | X | - | CI | - |
Nicon aestuarensis | 5 | X | X | - | X | - | - | X | - | X | - | ST | X |
Nicon japonicus | 2 | X | - | - | X | - | - | X | - | X | - | ST | X |
Nicon maculata | 10 | X | - | - | X | - | X | - | - | X | - | SU | - |
Nicon moniloceras | 9 | X | - | - | X | - | - | X | - | X | - | DI | - |
Nicon pettibonae | 5 | X | - | - | X | X | X | - | - | X | X | ST | - |
Nicon polaris | 5 | X | X | - | X | - | - | X | - | X | - | ST | X |
Nicon rotunda | 2 | X | - | - | X | - | X | - | X | X | - | ST | X |
Nicon sinica | 9 | X | - | - | X | - | - | X | - | X | - | CO | X |
Nicon yaguinae | 2 | X | X | - | X | - | ? | ? | ? | ? | - | ST | - |
Nicon orensanzi sp. n. | 2 | X | X | - | - | - | X | - | - | - | X | E | X |
1 | Superior notopodial lobe present | 2 |
– | Superior notopodial lobe absent | 7 |
2 | Tentacular cirri short, reaching chaetiger 2 | 3 |
– | Tentacular cirri reaching chaetiger 5 | 5 |
3 | Heterogomph falcigers present on supra- and subacicular fascicle, dorsal ligule subtriangular | 4 |
– | Heterogomph falcigers absent, with sesquigomph falcigers in infracicular position, dorsal ligule long and thin on median and posterior parapodia | Nicon orensanzi sp. n. |
4 | With homogomph falcigers in neuropodial subacicular position | Nicon rotunda |
– | Homogomph falcigers lacking | Nicon japonica |
5 | Tentacular cirri reaching chaetiger 5, dorsal ligule subtriangular | 6 |
– | Tentacular cirri reaching chaetiger 9, dorsal cirri conical | Nicon sinica |
6 | Mandibles with 6 oblique teeth, blade of falcigers short, with a terminal tooth directed downward | Nicon polaris |
– | Mandibles with up to 10 teeth; blade of falcigers longer, with blunt terminal end | Nicon aestuarensis |
7 | Tentacular cirri short, reaching chaetiger 2 | 8 |
– | Tentacular cirri reaching chaetiger 5 | 9 |
8 | Dorsal ligule cirriform , reduced in posterior chaetigers; falcigers with prolonged blade | Nicon abysssalis |
– | Dorsal ligule subtriangular, similar in size throughout; falcigers with long, anteriorly blunt blade distinctly serrated along inner margin | Nicon yaquinae |
9 | Tentacular cirri reaching chaetiger 5; subtriangular dorsal ligule; supra and infracicular sesquigomph falcigers present | Nicon pettibonae |
– | Tentacular cirri to chaetiger 9–10 | 10 |
10 | Longest pair of tentacular cirri partially annulated on distal end; falcigers with long blade, denticulate along inner margin | Nicon maculata |
– | All tentacular cirri annulated, with cylindrical articles; falcigers with short blades, denticles on proximal inner margin | Nicon moniloceras |
This publication is part of a work carried out by Berenice Trovant as a requirement for obtaining a MSc degree in ‘Biodiversity in tropical areas and its conservation’ at the Universidad Internacional Menéndez Pelayo (UIMP, Spain), a Masters program funded by the Spanish National Research Council (CSIC, Spain) and carried out at the Universidad Central del Ecuador. We thank to Santiago Tineo for their help in fieldwork. Authors would also like to thank two anonymous reviewers and Chris Glasby whose comments and suggestions were much appreciated and very helpful in improving the manuscript.