Paraonis amazonica, Ribeiro, Rannyele Passos, Alves, Paulo Ricardo, Almeida, Zafira da Silva de & Ruta, Christine, 2018

Ribeiro, Rannyele Passos, Alves, Paulo Ricardo, Almeida, Zafira da Silva de & Ruta, Christine, 2018, A new species of Paraonis and an annotated checklist of polychaetes from mangroves of the Brazilian Amazon Coast (Annelida, Paraonidae), ZooKeys 740, pp. 1-34 : 19-24

Paraonis amazonica sp. n. Figs 12, 13, 14

Type locality.

Brazil, Maranhão: São Luís, 02°35'56"S, 44°21'11.8"W, mangrove, 21 October 2010, R.P. Ribeiro.

Material examined.

Holotype: São Luís, 02°35'56"S, 44°21'11.8"W, one specimen, complete, 21 October 2010 (NPM-Pol 906). Paratypes: São Luís, 02°35'56"S, 44°21'11.8"W, one specimen, incomplete, 18 August 2010 (NPM-Pol 907); 80 specimens, all incomplete, 27 January 2011 (NPM-Pol 908); two specimens, both complete, 21 October 2010 (NPM-Pol 929); two specimens, both incomplete, 18 March 2012 (MNCN 16.01/17766). Caranguejos Island, 02°49'33.6"S, 44°28'51.1"W, three specimens, all incomplete, 26 January 2011 (NPM-Pol 930); 11 specimens, all incomplete, 28 March 2011 (MNCN 16.01/17765).

Distribution.

Only known from the type locality.

Diagnosis.

Rounded prostomium, clearly wider than longer. Dorsal brownish pigmentation reaching the beginning of the prostomium. Rounded to foliaceous branchiae (4-8 pairs), from the fourth segment. Neurochaetae of two types: acicular chaeta with lateral spine beginning in pre-branchial segments, and hook-shaped chaeta with terminal spines in post-branchial segments.

Description.

Complete holotype, 2.68 mm long, 0.17 mm wide (chaetiger 8), and 46 chaetigers. Three complete paratypes with 2.43-2.94 mm long, 0.18-0.20 mm wide and 36-54 chaetigers. Incomplete paratypes up to 4.607 mm long, 0.283 mm wide, and 16-61 chaetigers. Fixed individuals with brown pigmentation that reaches the distal end of the prostomium and extends along the body. Anteriorly flattened body, wider than longer, cylindrical from the 8th chaetiger and in all middle body region (Fig. 12A, B). Branchial region dorsoventrally flattened. Rounded prostomium, wider than longer (Fig. 12B, D). Absence of antenna, palpode, ciliated bands and eyes in the prostomium (Fig. 12A, B). The anterior segments are short, wider than longer. Long and biannulate segments in the post-branchial region. One pair of nuchal organs located on the posterior edge of the prostomium (Fig. 13A). Notopodial post-chaetal lobes absent in the pre-branchial region, the first notopodial post-chaetal lobe appear in the fifth branchial chaetiger. Notopodial post-chaetal cirrifom lobes, longer from the middle and posterior regions. Branchiae from chaetiger 4, rounded to foliaceous, flat, short, 4-8 pairs, first and last pairs are shorter (Fig. 12D). Notopodial capillary chaetae throughout the body. Curved capillary chaetae in the neuropodium and notopodium of the pre-branchial and branchial segments (Fig. 13B). Capillary neurochaetae progressively thinner, longer, and straight in the post-branchial segments. Capillary notochaetae of the posterior segments thicker than those anterior and median segments. Pre-branchial and branchial segments with 3-5 chaetae capil laries in the notopodium and 2-5 in the neuropodium. Post-branchial segments with 1-2 chaetae capillary in the notopodium, absent in the neuropodium. First acicular neuropodial chaetae with a lateral spine in chaetiger 2-8, and 2-3 chaetae in the branchial segments (Figs 13B, 14A). Neuropodium in the post-branchial middle segments and posterior end segments with one acicular chaeta with a lateral spine (Figs 13B, C, 14 A–C). Hook-shaped neurochaetae with terminal spine beginning in post-branchial chaetigers, 1-2 chaetae. Neuropodium in the post-branchial middle chaetigers with 2-4 hook-shaped chaetae with a terminal spine. Neuropodium in posterior chaetigers with two hook-shaped chaetae with a terminal spine (Figs 13B, C, 14B, C). Pygidium rounded with two anal lobes and three anal cirri: two dorsolateral and one medium-ventral (Figs 12C, 14D).

Colour.

Specimens in alcohol show brownish pigment spots all over the body, two pairs of reddish brown lateral spots in the pygidial lobes of some specimens.

Etymology.

Named after the Amazon Coast, region where type locality is located.

Remarks.

Paraonis amazonica sp. n. differs from all other species by the presence of acicular and hook-shaped modified neurochaetae. Currently, there are five valid species named in the genus Paraonis : Paraonis fulgens (Levinsen, 1884); Paraonis paucibranchiata Cerruti, 1909; Paraonis pycnobranchiata Fauchald, 1972; Paraonis pygoenigmatica Jones, 1968; and Paraonis strelzovi Hartmann-Schröder, 1980 (see Table 1). Several species first described as Paraonis were established as a synonymy of Aricidea ( López 2008), Levinsenia ( Gaston 1984), Paradoneis ( Mackie 1991), and Paraonides ( Parapar et al. 2012). Paraonis tenera Grube, 1873 is a species considered nomen oblitum by Strelzov (1973) because its description was inaccurate, being based on a single specimen and probably referring to a species of Aricidea .

Among the five valid species of Paraonis , P. fulgens , P. paucibranchiata , and P. strelzovi also have the first pair of branchiae in the fourth chaetiger as seen in P. amazonica sp. n. However, P. fulgens has more than 25 pairs of branchiae and the first post-chaetal lobe starts in the third chaetiger, whereas P. amazonica sp. n. has 4-8 pairs of branchiae and first post-chaetal lobe in the 9th chaetiger. In addition, P. fulgens (about 120 chaetigers in total) seems to be longer than P. amazonica sp. n. (up to 54 chaetigers in complete individuals). However, longer animals could be found, since incomplete individuals of P. amazonica sp. n. showed up to 61 chaetigers. Only four pairs of branchiae are described in P. paucibranchiata and P. strelzovi whereas P. amazonica sp. n. has 4-8 pairs of branchiae. Moreover, P. paucibranchiata differs from P. amazonica sp. n. by the presence of eyes and longer and straighter branchiae. The other two species mainly differ on the first chaetiger with branchiae and post-chaetal lobe. Paraonis pygoenigmatica has approximately 20 pairs of branchiae that begin in the sixth chaetiger, joined to the first dorsal lobes. In P. pycnobranchiata , the branchiae (about 19) are present from chaetiger 6-25. P. amazonica sp. n. and P. pycnobranchiata have the same pigmentation pattern consisting in small pigment spots scattered along the body.

Species of Paraonis are usually reported in marine, inshore and continental shelf environments ( Glasby and Wilson 2003). There are some exceptions, such as P. fulgens , recorded in the intertidal zone from Caribbean Sea ( Helguera et al. 2011), P. strelzovi in mangroves from Australia ( Hartmann-Schröder 1980), and P. pygoenigmatica recorded in estuarine areas from Brazil ( Barros et al. 2001). Paraonis amazonica sp. n. is the first record of a Paraonis species found in muddy bottoms in mangrove vegetated areas.