Aricidea (Acmira) chilikensis Choudhury, Dutta, Patro & Rastogi, 2025, sp. n.
Creators: name: Choudhury, Amita Kumari
name: Dutta, Joydeep
name: Patro, Shesdev
name: Rastogi, Gurdeep
Publisher: name: Zenodo
Year: 2025
Subjects: Biodiversity
Taxonomy
Animalia
Annelida
Polychaeta
Spionida
Paraonidae
Aricidea
Aricidea chilikensis

description: Aricidea (Acmira) chilikensis sp. n. Choudhury, Dutta & Patro
Figures 1–3
Material examined
Holotype: Length 8.79 mm, Width 0.31 mm (ZSI / EBRC /An-15937), Chilika Lagoon, southern sector (19°36ʹ14.16”N, 85°11ʹ33.14”E), Odisha, India, 30/06/2023, Coll. Amita Kumari Choudhury.
Paratypes (02 numbers): ZSI / EBRC /An-15938, Length- 14.76 mm, Width- 0.64 mm, incomplete specimen, ZSI / EBRC /An-15939, Length- 10.12 mm, Width- 0.35 mm, incomplete specimen.
Other materials: 03 individuals, length (8.01–17 mm), width (0.28–0.59 mm) (004. MSR / BoL-24); same data as holotype.
Etymology
The species is named after the site of its collection which is the Chilika Lagoon.
Habitat
In soft mud sand, depth 2.6 m, water temperature 30°C, salinity 20 PSU.
Diagnosis
Median antenna cylindrical, widest at the base with a tapered blunt end, branchiae anteriorly short, gradually increasing in size and elongated in last 4–5 chaetigers, modified neurochaetae distally strongly curved with a single long arista.
Description
Based on holotype, length: 8.79 mm, width: 0.31 mm.
Holotype complete with 101 chaetigers, body length 8.79 mm, width 0.31 mm; paratypes incomplete with 78–88 chaetigers, 10.12–14.76 mm long and 0.35–0.64 mm wide. Body wide, dorsoventrally flattened in branchial region, cylindrical in post-branchial region (Figure 3A). Prostomium triangular, width 2× times the length, distally rounded, with reddish pigment spots present along the anterior and lateral prostomial margin. Eye absent. Nuchal organs are a pair of oblique, deep slits. Median antennae are well-developed with central insertion, cylindrical, elongated, widest at the base and tapering to a blunt end, extending up to chaetiger 2 (Fig 1A, 3B).
Twenty-three pairs of branchiae are present on chaetiger 4–26. Branchiae arranged on dorsum, basally inflated without a ciliary band. Anterior branchiae are foliaceous, blunt-tipped, gradually increase in size and overlap along the midline of the body. Posterior-most (in last 4–5 chaetigers) are elongated, cirriform, blunt-tipped and longer than the anterior ones (Fig 1A, 3B). The first two notopodial postchaetal lobes are short and round (Figure 1B). Notopodial postchaetal lobes gradually increase from chaetiger 3, progressively longer in the branchial region to long, thin, filiform in the posterior region (Figure 1C). Neuropodial postchaetal lobes are absent. Inter-ramal papilla present till branchial region. Chaetae well-developed. Notochaetae all slender capillaries (Figure 2A). Notochaetae of the anterior region are comparatively thicker and longer than the postbranchial region. Neurochaetae includes slender capillary and modified chaetae starting from chaetiger 33. Modified neurochaetae distally strongly curved with a terminal long arista. Up to 6–8 modified chaetae per neuropodium (Fig. 2b, 3c). Mid-dorsal transversal line of prebranchial and branchial chaetigers without ciliary band. Pygidium, rounded with four reddish pigment spots and two anal cirri of similar size (Figure 2C).
Remarks
According to WoRMS database, a total of 26 species belong to the genus Aricidea (Acmira) (Read and Fauchald 2024). Further, Aricidea elongata Imajima 1973 and Aricidea rosea; Reish, 1968 which are not included under the subgenus Acmira, also possess hook and terminal distal arista in the posterior modified neuropodial region. Including these two species, the total species number under the subgenus leads to 28. A comparative table of the morphological characteristics of the species of the genus Aricidea (Acmira) is provided in Table 1.
Aricidea (Acmira) chilikensis sp. n. can be distinguished from other members of the subgenus by the shape of the median antenna, structure and pattern of the branchia, and modified neurochaetae. Among the 28 species, 18 species possess single or multiple terminal distal aristae in the modified posterior neuropodial region. Fifteen species, Aricidea (Acmira) bbkingi Barroso, Paiva & Ranauro, 2020, A. (A.) catherinae, Aricidea (Acmira) elongata Imajima, 1973, Aricidea (Acmira) filamentosa Barroso, Paiva & Ranauro, 2020, Aricidea (Acmira) finitima Strelzov, 1973, Aricidea (Acmira) katzmanni Erdoğan-Dereli & Çinar, 2020, Aricidea (Acmira) laubieri Hartley, 1981, A. (A.) lopezi, Aricidea (Acmira) meridionalis Laubier & Ramos, 1974, Aricidea (Acmira) mirifica Strelzov, 1973, Aricidea (Acmira) philbinae Brown, 1976, Aricidea (Acmira) pseudoassimilis Erdoğan-Dereli & Çinar, 2020, Aricidea (Acmira) rosea Reish, 1968, Aricidea (Acmira) rubra Hartman, 1963 and Aricidea (Acmira) taylori Pettibone, 1965 have single terminal distal arista similar to A. (A.) chilikensis sp. n.
Amongst the above 15 species, majority have posterior branchiae that are relatively longer than anterior branchiae, however, the last few pairs are equal or short in most species, whereas in A. (A.) chilikensis sp. n., the last pairs are the longest. Aricidea (Acmira) chilikensis sp. n. is characterised by branchiae that are shorter on anterior chaetigers and that gradually increase in size posteriorly, with posterior-most branchiae relatively elongated and narrow. In A. (A.) bbkingi, A. (A.) catherinae, A. (A.) elongata, and A. (A.) pseudoassimilis, the branchiae located at the posterior end are not elongated, indicating a more uniform length throughout. In contrast, A. (A.) philbinae exhibits elongated branchiae in the anterior region, making it distinctive. In species such as A. (A.) laubieri, the posterior pair of branchiae are smaller, while in A. (A.) filamentosa, A. (A.) finitima, and A. (A.) katzmanni, only the last two pairs of branchiae are shorter than the others, giving these species a characteristic appearance. In A. (A.) lopezi, branchiae are present from chaetiger 4 to 53 (while in A. (A.) chilikensis sp. n., they are present from chaetiger 4 to 26). (Continued) Similarly, A. (A.) mirifica and A. (A.) rosea possess only a single short pair of branchiae located at the very end of the body. A. (A.) rubra has antennae that end in a sharply pointed tip (A. (A.) chilikensis sp. n., has cylindrical, elongated antennae that are widest at the base and taper to a blunt end) and possesses up to 30 pairs of branchiae (23 pairs in A. (A.) chilikensis sp. n., In A. (A.) taylori, the branchiae are ciliated except at the distal tip, while cilia are absent in A. (A.) chilikensis sp. n.
In addition, the median antenna of A. (A.) chilikensis sp. n. is widest at the base tapering to a blunt end. Among the above 15 species, A. (A.) meridionalis shows antenna and branchial characters similar to A. (A.) chilikensis sp. n. Aricidea (Acmira) chilikensis sp. n. differs from A. (A.) meridionalis by lacking a ciliary band on both sides of the branchia and on the mid-dorsal transversal line of branchial and prebranchial chaetigers (vs. present in A. (A.) meridionalis). Further, the terminal and subterminal region of modified neurochaetae display small hairs which are absent in A. (A.) chilikensis sp. n.
description: Published as part of Choudhury, Amita Kumari, Dutta, Joydeep, Patro, Shesdev & Rastogi, Gurdeep, 2025, A new species of the genus Aricidea (Acmira) Hartley, 1981 (Polychaeta: Paraonidae) from Chilika Lagoon, east coast of India, pp. 45-55 in Journal of Natural History 59 (1 - 4) on pages 46-53, DOI: 10.1080/00222933.2024.2439620, http://zenodo.org/record/14765071