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- Perinereis malabarensis sp. nov. (1)
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Two new species of Perinereis with single bar-shaped paragnaths on area VI (Group 1) from the rocky shores of Mumbai, Maharashtra, India, are described with barely (Subgroup 1A) or largely (Subgroup 1B) expanded proximal region of dorsal ligule in posterior parapodia. Perinereis malabarensis sp. nov. can be distinguished from the morphologically similar 1B species P. euiini Park & Kim, 2017 by the paragnath count in area I, the laterally isolated paragnaths in area III, and the length of the dorsal cirrus and dorsal ligule. Additionally, P. misrai sp. nov. is more similar to 1A species P. falsovariegata Monro, 1933 and P. villalobosi Rioja, 1947, but differs by the paragnath count in areas III–V and VII–VIII, the isolated paragnaths in area III, and the number of rows in the anterior band of areas VII–VIII. The morphological characters of the current 44 species within Perinereis G1 are compared, and an identification key to the species belonging to this group is also provided.
The present study redescribes four species of Neanthes Kinberg, 1865 (Nereididae de Blainville, 1818) based on their type specimens collected from different worldwide localities: Neanthes chilkaensis (Southern, 1921) from India, N. galetae (Fauchald, 1977) from Panama, N. helenae (Kinberg, 1865) from St Helena Island, and N. mossambica (Day, 1957) from Mozambique. The morphology of the types was re-examined for the first time after the species were originally described, and incorporated the recent improvements in the standards and terminology for describing nereidid features. The arrangement of paragnaths on area VI stood out among the diagnostic features used to distinguish these four species. Neanthes chilkaensis and N. helenae are the unique nereidids bearing p-bar paragnaths on the area VI. Both species are also distinctive as the former species only exhibited p-bar paragnaths on the area VII–VIII and the latter ventrolateral projections on the apodous segment. Further examination revealed that N. nanciae (Day, 1949) from St Helena is a junior synonym of N. helenae. Moreover, N. galetae and N. mossambica are distinguishable from other species also by the development of dorsal cirri, neuropodial postchaetal lobe and ventral ligule, the presence/absence of merged paragnaths on area IV, paired oesophageal caeca, among other features. This study has further contributed to the morphological delimitation of the species in Neanthes as a first step towards revising the genus.