Nereis dhritiae, Pradhan & Villalobos-Guerrero & Mohapatra, 2025
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https://doi.org/10.11646/zootaxa.5729.2.6 |
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lsid:zoobank.org:pub:46FE176D-9A63-4E32-9D34-C7C4AEA325B4 |
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https://treatment.plazi.org/id/955487DD-FFF6-F015-21CB-049DC1E39258 |
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Plazi |
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Nereis dhritiae |
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sp. nov. |
Nereis dhritiae sp. nov.
urn:lsid:zoobank.org:act:
Fig. 3 View FIGURE 3
Type material. India, Bay of Bengal. Holotype: EBRC /ZSI/An-18598, Digha, Purba Medinipur ( 21°37’15.6”N 87°31’02.1”E), West Bengal, 4 May 2025, sandy beach, coll. J. Pradhan. GoogleMaps Paratypes: Three specimens ( EBRC /ZSI/ An-18599), same data collection data as for holotype GoogleMaps .
Additional material. India, Bay of Bengal. Four specimens ( EBRC /ZSI/An-18600), same data collection as for holotype; 14 Jun 2025 . Six specimens ( EBRC /ZSI/An-186001), same data collection as for holotype, 12 July 2025 . Twenty-four specimens ( EBRC /ZSI/An-18602), same data collection as for holotype, 30 Jul 2025 .
Diagnosis. Species of Nereis infra group I.B.2 sensu Salazar-Vallejo et al. (2021). Specimens with one paragnath on area V; area III without laterally isolated paragnaths; areas VI–V–VI ridge pattern λ-shaped; areas VII–VIII with a distinct anterior band consisting of small cones; homogomph falciger with blade consisting of distinct terminal tendon and 1–2 fine teeth; heterogomph falcigers with camerate shaft divided into two partitions; tentacular cirrostyles smooth, short, posterodorsal extending to chaetiger 3.
Description. Holotype complete, in good condition ( Fig. 3A View FIGURE 3 ), 16.6 (16.6−33.6) mm TL, 4.1 (2.3−9.1) mm L15, 1.5 (0.7−2.2) mm W15, with 58 (56−87) chaetigers. General body yellowish. Dorsum of prostomial posterior region black, seeming masked prostomium ( Fig. 3A, B View FIGURE 3 ); prostomial anterior region reddish-brown ( Fig. 3C View FIGURE 3 ). Palps, tentacular cirrophores, and anterior dorsum of body brown ( Fig. 3C View FIGURE 3 ). Anterior margin of maxillary ring pale brown. Anterior and posterior dorsal margins of first 12 segments (including tentacular belt) with one transverse brown band; anterior band thick (covering half of segment), posterior band narrow (covering one-quarter of segment) with one dorsolateral darker patch on each side ( Fig. 3A, B View FIGURE 3 ). Parapodial glands located in ligules and dorsal cirri cirrophores, granulose, brown, becoming more evident from about chaetiger 22, more intense posteriorly.
Prostomium campanulate ( Fig. 3B, C View FIGURE 3 ); anterior region distally entire, sub-quadrangular, as long as posterior region; anterolateral gap between antenna and palpophore narrow, as wide as basal diameter of antennae. Nuchal organs deeply embedded.
Palpophores barrel-shaped ( Fig. 3B, C View FIGURE 3 ), slightly longer than wide, as long as prostomium; sub-distal transverse groove indistinct. Palpostyles spherical ( Fig. 3B, C View FIGURE 3 ), one-half as wide as diameter of palpophore.
Antennae tapered, conical, medium size ( Fig. 3B View FIGURE 3 ), as long as prostomial posterior region, extending slightly beyond palpophore; antennae slightly separated by gap as wide as basal diameter of antenna.
Paired eyes in sub-trapezoid arrangement, blackish ( Fig. 3B View FIGURE 3 ); gap between both pairs reduced, eyes nearly coalesced. Anterior pair of eyes sub-rounded, diameter 2.7 times wider than that of base of antennae, with gap between eyes twice as wide as eye diameter; lenses visible, purplish, oval, placed anterolaterally, covering 40% of eye. Posterior pair of eyes rounded, with diameter as wide as that of base of antennae, not covered by tentacular belt, with gap between eyes twice as wide as eye diameter; lenses visible, purplish, oval, placed centrally, covering 25% of eye.
Tentacular belt 1.3 times longer than chaetiger 1, with rounded anterior margin ( Fig. 3B View FIGURE 3 ). Tentacular cirrostyles smooth ( Fig. 3B, C View FIGURE 3 ); anterior and posterior cirrostyles located anterodorsally to tentacular belt. Anterodorsal cirrostyles extending backwards to chaetiger 2–3; anteroventral cirrostyles extending upwards beyond palpophore. Posterodorsal cirrostyles extending backwards to chaetiger 4–5; posteroventral cirrostyles extending sideward to middle of prostomial posterior region. Dorsal and ventral cirrophores distinct; dorsal cylindrical, ventral ring-shaped.
Proboscis everted, with maxillary and oral rings cylindrical, wider than long ( Fig. 3C, D View FIGURE 3 ). Jaws mostly amber; 12–13 (13–17) teeth: 7 (7–11) subterminal teeth, 5–6 ensheathed proximally ( Fig. 3E View FIGURE 3 ); 3 canals emerging from pulp cavity ( 2 in rest of specimens), broadly separated from each other ( Fig. 3F View FIGURE 3 ). Reddish-brown paragnaths on maxillary and oral rings ( Fig. 3C, D View FIGURE 3 ), consisting of conical and few merged paragnaths; plate-like basements absent. Area I: 1 (1−4), small cone ( Fig. 3C View FIGURE 3 ); Areas IIa: 28 (17–27) and IIb: 26 (17–25), two to three slightly regular rows of uneven cones in drop-shaped patch, distal cones larger ( Fig. 3C View FIGURE 3 ); Area III: 19 (15–22), oval patch of uneven cones, proximal cones larger, without distinct laterally isolated cones ( Fig. 3D View FIGURE 3 ); Areas IVa: 24 (17–37) and IVb: 29 (19–35), lemniscate patch with uneven proximal cones in oval arrangement ( Fig. 3D View FIGURE 3 ) and 5 (5–8) merged paragnaths of small and medium size located distally; Area V: 1, small cone placed slightly behind level of paragnaths on Area VI ( Fig. 3C View FIGURE 3 ); Areas VIa: 6 (4–6) and VIb: 5 (5–6), irregular oval patch of even cones ( Fig. 3C View FIGURE 3 ); Areas VII–VIII: 79 (66–89), two well-separated bands of cones, with anterior band consisting of one transverse row of even paragnaths (furrows with one small cone and ridges with three or four cones on each region), and posterior band with uneven cones in three slightly regular transverse rows displaced somewhat from each other, distal row with larger cone, most paragnaths present on ridges, only one or two cones on furrows ( Fig. 3D View FIGURE 3 ). Areas VI–V–VI ridge pattern λ-shaped ( Fig. 3C View FIGURE 3 ). Gap between Area VI and Areas VII–VIII narrow, as wide as palpostyle ( Fig. 3C View FIGURE 3 ). Paired oesophageal caeca present.
Notopodia consisting of dorsal cirrus with cirrostyle and cirrophore, dorsal ligule, and median ligule in biramous parapodia; notopodial prechaetal lobe not developed throughout.
Dorsal cirri composed of cirrostyle and compressed cirrophore ( Fig. 3G–K View FIGURE 3 ). Cirrostyles long, cirriform; 3.5 times longer than cirrophore in anteriormost chaetigers, 2.5 times longer than that in following chaetigers. Cirrostyle extending markedly beyond dorsal ligule throughout body; attached basally to cirrophore in anteriormost chaetigers, medially in following chaetigers ( Fig. 3G–K View FIGURE 3 ). Cirrophores of similar length and compressed throughout body ( Fig. 3G–K View FIGURE 3 ); 2 irregular patches of glands present throughout, more distinct in middle chaetigers ( Fig. 3J View FIGURE 3 ), covering ligule almost entirely.
Dorsal ligule of similar length throughout ( Fig. 3G–K View FIGURE 3 ), becoming posteriorly slightly narrower; digitiform in anterior chaetigers ( Fig. 3H View FIGURE 3 ), bluntly conical in following chaetigers; slightly shorter than median ligule in anterior chaetigers, somewhat longer than that in following chaetigers; projecting distinctly beyond notoacicula throughout; barely glandular.
Median ligule well developed, of similar length throughout ( Fig. 3G–K View FIGURE 3 ); bluntly conical, thick in anterior chaetigers, narrower in following chaetigers.
Neuropodia consisting of neuroacicular ligule, ventral ligule, and ventral cirrus with cirrostyle and indistinct cirrophore; inferior, superior and postchaetal lobes not developed throughout.
Neuroacicular ligule as wide and long as ventral ligule in anterior and middle chaetigers ( Fig. 3G, H View FIGURE 3 ), 1.5 times wider and twice longer than that in posterior parapodia ( Fig. 3J, K View FIGURE 3 ).
Ventral ligule well developed throughout; bluntly triangular, thick in anteriormost and anterior chaetigers ( Fig. 3G, H View FIGURE 3 ), bluntly conical and slender in following chaetigers ( Fig. 3I–K View FIGURE 3 ); smaller than median ligule throughout.
Ventral cirrostyles cirriform, slender; two-thirds as long as ventral ligule throughout body ( Fig. 3H, I, K View FIGURE 3 ).
Body of aciculae mostly black throughout body. Notoaciculae absent in first two chaetigers ( Fig. 3H View FIGURE 3 ). Neuroaciculae extending beyond distal end of notoaciculae in anterior and middle chaetigers ( Fig. 3H, I View FIGURE 3 ), as long as notoaciculae in following chaetigers ( Fig. 3J, K View FIGURE 3 ).
Notochaetae consisting of homogomph spinigers and homogomph falcigers ( Fig. 3L View FIGURE 3 ); spinigers present in anterior chaetigers, replaced by falcigers from about chaetiger 20; 9–17 spinigers present in anterior chaetigers; 1 falciger in middle chaetigers, and 2 in posterior chaetigers.
Supracicular neurochaetae consisting of homogomph spinigers and heterogomph falcigers throughout ( Fig. 3M, N View FIGURE 3 ); 3–4 spinigers present in anteriormost chaetigers, 10–12 spinigers in anterior chaetigers, 2–8 spinigers in middle chaetigers and posterior chaetigers; 2–3 falcigers present in anteriormost chaetigers, 5–9 falcigers in anterior chaetigers, 4–7 falcigers in middle chaetigers, and 1–2 falcigers in posterior chaetigers.
Subacicular neurochaetae consisting of heterogomph spinigers ( Fig. 3O View FIGURE 3 ) and heterogomph falcigers throughout; 5–6 spinigers present in anteriormost chaetigers, 2–3 spinigers in following chaetigers; 3–4 falcigers present in anteriormost chaetigers, 11–14 falcigers in anterior chaetigers, 2–7 falcigers in middle chaetigers and 5–6 falcigers in posterior chaetigers.
Blade of homogomph spinigers finely serrated throughout, with proximal serrations slightly thicker in middle and posterior chaetigers ( Fig. 3N View FIGURE 3 ). Blade of heterogomph spinigers finely serrated throughout ( Fig. 3O View FIGURE 3 ). Blade of homogomph falcigers short and narrow ( Fig. 3L View FIGURE 3 ); terminal tooth incurved with distinct tendon; serrations present in about one-third to one-half of total blade length, two fine teeth in middle chaetigers, decreasing to one (sometimes none) posteriorly. Blade of heterogomph falcigers tapering, medium and long (b/a ratio: 1.9–2.3) throughout ( Fig. 3M View FIGURE 3 ); finely serrated, terminal tooth incurved with distinct tendon. Shaft of falcigers camerate, homogomph with longitudinal undivided cavity ( Fig. 3L View FIGURE 3 ), and heterogomph divided sub-distally into two distinct longitudinal partitions ( Fig. 3M View FIGURE 3 ).
Pygidium with cirrophores of anal cirri barely developed; anal cirri short, as long as last 1–3 chaetigers.
Variations. Total body length: 16.6–33.6 mm. Length to chaetiger 15: 2.3–9.1 mm. Body width at chaetiger 15: 0.7–2.2 mm. Number of total chaetigers: 56–87. Posterodorsal tentacular cirri extending to chaetiger 4–5. Jaws with 12–17 teeth. Number and pattern of paragnaths: Area I: 2–4 paragnaths (single paragnath in holotype); Area IIa: 17–27 and IIb: 17–25; Area III: 15–22 in arranged in three rows; Area IV: 17–35; Area V: 1; Area VI: 4–6, arranged in regular two rows; Area VII–VIII: 66–89, arranged in four irregular rows. Anal cirri as long as last 2–3 chaetigers.
Etymology. The specific epithet dhritiae is named in honour of Dr. Dhriti Banerjee, the first woman Director of the Zoological Survey of India, Kolkata, India, in recognition of her scientific efforts and contributions to animal taxonomy.
Type locality. Digha ( 21°37’15.6”N 87°31’02.1”E), West Bengal, Bay of Bengal , India ( Fig. 1 View FIGURE 1 ) GoogleMaps .
Habitat. Dwelling in wooden dock piles on sandy beaches ( Fig. 1C View FIGURE 1 ), which are submerged during high tide. The species is also associated with other invertebrates, such as scale worms ( Polynoidae ), small molluscs, isopods, crustaceans, and gobies.
Distribution. This species is only known from the type locality.
Remarks. Nereis dhritiae sp. nov. belongs to the artificial infra group I.B.2 sensu Salazar-Vallejo et al. (2021), which is represented by species with blades of homogomph falcigers finely denticulate, similar dorsal ligules throughout the body, parapodial ligules tapered (longer than wide), and pharyngeal areas VII–VIII with a discontinuous row of paragnaths. The typical representative species in infragroup I.B.2 is N. zonata Malmgren, 1867 from Greenland ( Salazar-Vallejo et al. 2021).
Nine species of Nereis have been recorded from India (sensu Sivadas & Carvalho 2020): Nereis couteri Gravier, 1899 , N. falcaria (Willey, 1905) , N. gaikwadi Day, 1973 , N. heteromorpha Horst, 1924 , N. jacksoni Kinberg, 1865 , N. lamellosa Ehlers, 1868 , N. persica Fauvel, 1911 , N. talehsapensis Fauvel, 1932 , and N. zonata . However, N. heteromorpha , and N. talehsapensis belong to Neanthes as currently circumscribed (see Villalobos-Guerrero & Idris 2021). Among the remaining seven species, the following three are included in I.B.2 here: Nereis dhritiae sp. nov., N. gaikwadi , and N. persica , in addition to N. zonata .
Nereis dhritiae sp. nov. can readily be distinguished from N. gaikwadi , N. persica and N. zonata by having blades of homogomph falcigers consisting of a terminal incurved tooth with a distinct tendon (absent in the three species). Also, N. dhritiae sp. nov. is different from N. persica and N. zonata by the presence of one paragnath on area V (absent in the two species) and the anterior row of area VII–VIII with only small paragnath (large only in N. persica , mixed sizes in N. zonata ).
Nereis dhritiae sp. nov. resembles N. gaikwadi in several features; for instance, the presence of one paragnath on area V, the anterior row of areas VII–VIII with only small paragnaths, the body pigmentation patterns, and others. Even when the original description by Day (1973) is brief and scarcely illustrated, and no further studies on the species (type material housed in the Natural History Museum, London, NHMUK) under catalogue numbers 1972.55/ holotype and 1972.56/ paratype) have been conducted, some original diagnostic characteristics are still helpful in separating the two species.
Besides the blade shape of homogomph falcigers mentioned above, N. dhritiae sp. nov. differs in having up to two teeth, in contrast to only one in N. gaikwadi . In N. dhritiae sp. nov., the areas VII–VIII have well-separated anterior and posterior rows, with the latter comprising a combination of large and small paragnaths. In contrast, the rows in N. gaikwadi are mixed, consisting solely of small paragnaths. Finally, the tentacular cirrostyles in N. dhritiae sp. nov. are smooth, in contrast to distally articulated ones in N. gaikwadi . Based on these differences among the Nereis members recorded from India, N. dhritiae sp. nov. is proposed as a new species.
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.
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