Abstract
A new pilargid species, Sigambra sundarbanensis sp. nov., is described from the rivers Matla and Thakuran, in the central Indian sector of the Sundarbans Estuarine System. This species is characterized by several characters such as the starting position of the notopodial hooks, the length of the median antenna and the variation in number of the neuropodial chaetae. These characters distinguish the new species from its congeners. Some parapodial glands have been found in individuals of this species. The new species closely resembles Sigambra parva (Day, 1963). Additionally, an updated key of genus Sigambra is provided, along with a table indicating their morphological variations and a global map showing their type localities.
Highlights
Pilargids are uncommon nereidiform marine annelids; most are free-living, and many are motile burrowers
We describe a new species of Sigambra from the rivers Matla and Thakuran in the Sundarbans Estuarine System (SES) delta
We report on some glandlike structures in parapodial spaces, which have not been reported from any species of this genus
Summary
Pilargids are uncommon nereidiform marine annelids; most are free-living, and many are motile burrowers. They are ubiquitous in sediments at various depths in estuarine or oceanic realms, most preferably in coarse to mixed substratum (Jumars et al 2015). The pharynx is bulbous, usually papillated, it has rigid structures, sometimes with circlets of marginal papillae. Pilargidae de Saint–Joseph, 1899 comprises about 112 accepted species, under 12 genera (WoRMS 2020). This family has been reviewed several times by Hartman (1947), Pettibone (1966), Salazar-Vallejo (1986) and Licher & Westheide (1997). Further investigations by Pleijel & Dahlgren (1998) and Dahlgren et al (2000) rejected the previous hypothesis of inclusion of pilargids within Hesionidae (Grube, 1850), and recognized them as non-overlapping families
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