Perinereis nuntia (Savigny in Lamarck, 1818)

Villalobos-Guerrero, Tulio F., 2019, Redescription of two overlooked species of the Perinereis nuntia complex and morphological delimitation of P. nuntia (Savigny in Lamarck, 1818) from the Red Sea (Annelida, Nereididae), Zoosystema 41 (24), pp. 465-496 : 468-469

Perinereis nuntia species complex

Perinereis group 3 – Hutchings et al. 1991: 271.

Perinereis nuntia species group – Wilson & Glasby 1993: 259. — Glasby & Hsieh 2006: 558.

DIAGNOSIS (MODIFIED AFTER Glasby & Hsieh 2006). — Prostomium with entire anterior margin, anterolateral edges wider than antennal diameter. Antennae present. Two pairs of eyes, anterior pair more widely spaced than posterior pair; lens anterolateral in anterior pair, posterolateral in posterior one. Palpophore with transverse groove present; palpostyles conical. Four pairs of tentacular cirri with distinct cirrophores. Apodous anterior segment, greater than length of chaetiger 1. Eversible pharynx with one pair of jaws, each with two or more canals emerging from pulp cavity. Both rings of pharynx with paragnaths, rarely absent on any of areas. Conical paragnaths on all areas, except AVI with 3-20 shield-shaped or pyramidal-shaped paragnaths on each side in a single row (sometimes few cones present); AIV occasionally with merged paragnaths. AVI-V-VI patterns: λ- shaped, χ- shaped, υ- shaped, or ɔc-shaped. Notopodia with dorsal and median ligules from third parapodia. Dorsal cirri displacing progressively on dorsal ligule. Dorsal ligule similar in size and shape to median ligule throughout body or barely uneven. Notoacicular process present. Neuropodial postchaetal lobe poorly developed, rounded. Neuropodial superior and inferior lobes present at least in anterior parapodia, blunt. Ventral ligule present throughout body. Single ventral cirri throughout body. Notoaciculae and notochaetae on chaetigers 1 and 2, absent, thereafter present. Aciculae black. Notochaeta: homogomph spinigers, present throughout body. Neurochaeta, supracicular fascicle: homogomph spinigers and heterogomph falcigers, both present throughout body. Neurochaeta, subacicular fascicle: heterogomph spinigers present at least in median and posterior chaetigers, heterogomph falcigers present throughout body (homogomph spinigers rarely present). Anal cirri with cirrophore. Paired esophageal caeca present. Glandular patches present in dorsal ligule.

REMARKS

Grube (1851) referred all the known nereidids having biramous parapodia and three ligules in Nereis Linnaeus, 1758 , which was simultaneously divided into three subgenera: Nereis (Heteronereis) , N. (Nereilepas), and N. ( Nereis ). The latter subgenus, which included N. nuntia , was characterized by the species bearing long dorsal cirri (projecting beyond dorsal ligule). Later, Kinberg (1865) established several genera using the arrangement of areas and occurrence of papillae/paragnaths on the pharynx. For instance, he proposed Neanthes by having similar-sized parapodia throughout body and only conical paragnaths on all pharyngeal areas; whereas Perinereis Kinberg, 1865 by having parapodia progressively changing throughout body and pharynx with conical and transverse paragnaths, lacking pectiniform (or rod-like, sensu Bakken et al. 2009) paragnaths. However, Kinberg overlooked N. nuntia . Few years later, Ehlers (1868) lumped all Kinberg’s genera with paragnaths in Nereis , and included N. nuntia in a group with similar-sized or slightly uneven parapodia throughout body and paragnaths on all areas. Afterward, Claparède (1870) separated a few species of Nereis in different subgenera.

Grube (1874) developed an accurate analysis of nereidids morphology, and despite the fact that he did not recognize several of the Kinberg’s genera, including Neanthes , he suggested that Kinberg’s classification of pharyngeal armament was useful for practical purposes. Thus, Grube (1874) proposed several subgenera of Nereis based on the occurrence of papillae and/or paragnaths on a single or both rings of pharynx; among them, N. ( Lycoris ) that was characterized by having only conical paragnaths on both rings. This subgenus was simultaneously divided into three groups mainly by the number and arrangement of paragnaths on AVI: 1) four or five paragnaths in quadrangle or cross, or more in a circular group (e.g. N. pelagica Linnaeus, 1758 and related species); 2) several paragnaths in a long single arched row, running towards the middle of AV (e.g. N. nuntia species complex); and 3) paragnaths in an oval or rounded patch of transverse rows, or a small linear transverse row of three cones (e.g. N. zonata Malmgren, 1867 and related species). Likewise, Grube (1874) also proposed N. ( Perinereis ) mainly by having AVI with 1-2 paragnaths transversely stretched. Later, von Marenzeller (1879) described a new species ( Nereis mictodonta ) related to N. nuntia -like species, and he stated that this group could not be included in the genus Perinereis nor Neanthes by sometimes having either conical and transverse paragnaths on AVI.

Langerhans (1880) recognized the generic level of Perinereis with no further details. Horst (1889), based mainly in Grube (1874), extended the N. ( Perinereis ) definition by including those species in which the AVI have either only transverse paragnaths, or both conical and transverse paragnaths. He included P. marionii (Audouin & Milne-Edwards, 1833) and P. mictodonta , but N. nuntia was not mentioned. Later, de Saint-Joseph (1898) recognized as valid several of the Kinberg’s names, either as genus or subgenus, based only on the pharyngeal characters, excluding all parapodial features. As a consequence, Perinereis was considered as valid only by the presence of conical and transverse paragnaths, whereas Neanthes was regarded as a subgenus of Nereis by having only conical paragnaths; nevertheless, it is noteworthy that N. nuntia was not considered in his proposal. Afterward, Gravier (1902) slightly improved the de Saint-Joseph’s classification but recognized that it is still necessary a greater understanding of subgenera delimitation. Gravier (1899, 1902) proposed the inclusion of N. nuntia into N. ( Neanthes ) by having apparently only conical paragnaths, particularly on AVI; likewise, he supported Horst definition of Perinereis and described a new species ( P. heterodonta ) with conical and transverse paragnaths on such pharyngeal area. The generic level and the expanded definition of Perinereis prevailed mainly within French annelidologists (de Saint-Joseph 1906; Fauvel 1911, 1914, 1918, 1919, 1921, 1932), whereas the subgeneric level and the older definition by Grube prevailed within German, Dutch and English annelidologists ( Ehlers 1897, 1905, 1920; Augener 1913, 1918; McIntosh 1910; Horst 1924).

Augener (1913) suggested N. nuntia into N. ( Perinereis ), as for N. vallata Grube & Kröyer in Grube, 1858 and his new subspecies N. (Perinereis) heterodonta var. mictodontoides . Afterward, Fauvel (1919) did not recognize the species closer to P. nuntia (known and valid at the moment), referring them only as varieties of P. nuntia . He regarded it as a polymorphic and widespread species distributed in the Red Sea, Persian Gulf, Indian Ocean, South Africa, Chile, Indo-Pacific, and Japan. Therefore, a general diagnosis of the species complex was provided for the first time, many species were synonymized, and several varieties arose from these assumptions: Perinereis nuntia var. brevicirris , P. nuntia var. djiboutiensis , P. nuntia var. heterodonta , P. nuntia var. vallata , and P. nuntia var. typica . The earlier species variety P. heterodonta var. mictodontoides Augener, 1913 and P. mictodonta were regarded as synonym of the brevicirris type ( Fauvel 1919). Later, Fauvel (1921) proposed P. nuntia var. majungaensis from Madagascar, and kept recognizing the six varieties in further works.

Perinereis nuntia species complex has been retained in this genus ever since ( Fauvel 1932, 1953; Hartman 1959; Day 1967; Paik 1975; Wu et al. 1985; Hutchings et al. 1991; Wilson 1993). Wilson & Glasby (1993) developed a revisionary effort of the P. nuntia species complex using type and/or non-type materials of many related species. They provided a diagnosis for the complex, several species were recognized to species level, and others were regarded as synonyms; in total, 12 species were considered as valid within the complex. Later, Glasby & Hsieh (2006) emended the P. nuntia species complex diagnosis, described three new related species and redescribed another two from the East Asia seas.

Based on phylogenetic analysis of nereidins using morphological data, Bakken & Wilson (2005) established Perinereis as a polyphyletic group since their species were present in two distant clades. Some species, including the type species of the genus, P. novaehollandiae Kinberg, 1865 , which is a junior synonym of P. amblyodonta (Schmarda, 1861) , are nested with two Pseudonereis and three Neanthes species (currently regarded in Pseudonereis, sensu Bakken 2007 ); whereas the other three Perinereis species ( P. variodentata , P. nuntia and P. vallata ) were related with Neanthes / Nereis species. Despite this evidence, P. nuntia species complex is retained in Perinereis nowadays ( Glasby & Hsieh 2006; Park & Kim 2007; Glasby 2015), although its morphology is notoriously different from the type species. For instance, according to Augener (1922) and my observations on some Australian specimens of P. amblyodonta (ZMB 5274), P. nuntia is mainly distinguished from P. amblyodonta by having dorsal ligule of similar size and shape or slightly uneven throughout the body, whereas in P. amblyodonta it is notoriously expanded in posterior parapodia. Likewise, the dorsal cirrus in P. nuntia is medially placed on dorsal ligule, but it is subterminal in posterior parapodia of P. amblyodonta . Finally, P. nuntia has a single transverse row of several (≥3) shield-shaped bars and/ or conical (sometimes pyramidal) paragnaths on each side of AVI, whereas P. amblyodonta has one large shield-shaped bar on the same area.

This phylogenetic and morphological evidence suggests that the P. nuntia species complex belongs to a different genus, perhaps within the closely related genus Neanthes or Nereis ; nevertheless, these two genera also undergo similar taxonomic problems since both are also regarded as polyphyletic ( Bakken & Wilson 2005). In order to elucidate the taxonomic problems, it is essential to restrict the definition of the genera by reviewing the species within. It would aid in delimiting their morphology, and consequently, in avoiding speculative new combinations, as could be the case of the P. nuntia species complex.