Perinereis misrai, Prajapat, Villalobos-Guerrero & Vachhrajani, 2024

Prajapat, Vaishali, Villalobos-Guerrero, Tulio F. & Vachhrajani, Kauresh D., 2024, Two new species of Perinereis Kinberg, 1865 (Annelida: Nereididae) from the rocky shore of Maharashtra, India, including notes and an identification key to Group 1, European Journal of Taxonomy 935, pp. 256-282 : 269-274

Perinereis misrai sp. nov.

urn:lsid:zoobank.org:act:08082AAD-2FAC-4BA4-BD90-FD7B367FCCE5

Fig. 3 , Table 1

Diagnosis

Species of subgroup 1A. Specimens with crescent-shaped bars on area VI; areas VI–V–VI ridge pattern π-shaped; area III with laterally isolated paragnaths; areas VII–VIII with anterior band of paragnaths consisting of one row; distal region of dorsal ligule anteriorly bluntly conical, becoming posteriorly slightly shorter; dorsal cirri longer than distal region of dorsal ligule on all chaetigers; falcigers with camerated shaft divided into two partitions; postero-dorsal tentacular cirri extending to chaetiger 6–11.

Etymology

The new species is named to honour Dr Amales Misra, a renowned Indian researcher from the Zoological Survey of India (ZSI), who contributed extensively to the taxonomy and ecology of annelids from India, particularly nereidids. The specific epithet is a noun in the genitive case (ICZN 1999, Art. 31.1.2).

Type material

Holotype INDIA • Mumbai , Malabar Hill; 18°57′18.0″ N, 72°47′43.0″ E; 11 May 2023; V. Prajapat and K. Vachhrajani leg.; rocky shore; MSUB-ZL-AN-PCh-06 .

Paratypes INDIA • 5 specs; same collection data as for holotype; 18°57′21.5″ N, 72°47′44.9″ E; ZSI-WRC ANN/27 .

Description (holotype (MSUB-ZL-AN-PCh-06))

COLOURATION AND MEASUREMENTS. Atoke, complete, in good condition, 57 (42−79) mm TL, 7 (3.9−7.2) mm L10, 1.5 (1.5−2.2) mm W10, and 122 (85−128) chaetigers. Body color brownish ( Fig. 3 A−B); dorsum of prostomium, anterior surface of cirrophores of tentacular cirri, and first four anterior segments with brown pigmentation, reducing intensity in next few segments.

PROSTOMIUM. Campanulate ( Fig. 3B ); anterior region distally entire, sub-quadrangular, slightly longer than posterior region; anterolateral gap between antenna and palpophore wide, 1.3 × as wide as basal diameter of antennae. Nuchal organs deeply embedded, slightly oblique, 1.5 × as wide as posterior pair of eyes.

PALPOPHORES. Sub-conical, thick, 1.3 × as long as wide, as long as entire prostomium; sub-distal transverse groove distinct ( Fig. 3B ). Palpostyles oval, one-third as wide as diameter of palpophore.

ANTENNAE. Tapered, conical, long as long as anterior region of prostomium ( Fig. 3B ); antennae nearly joined, gap one-third as wide as basal diameter of antennae.

EYES. Paired, in sub-rectangular arrangement, blackish ( Fig. 3B ); gap between both pairs three-quarters as wide as diameter of posterior pair. Anterior pair oval, with eye diameter slightly wider than that of antennae, with gap between eyes 4 × as wide as eye diameter; lenses visible, whitish, oval, placed anterolaterally, covering about 40% of eye. Posterior pair oval, with diameter as wide as that of antennae, not covered by tentacular belt; lenses visible, whitish, oval, placed centrally, covering about 40% of eye.

TENTACULAR BELT. Nearly as long as chaetiger 1, with straight anterior margin; dorsum without transverse wrinkle.

TENTACULAR CIRRI. Smooth ( Fig. 3B ). Antero-dorsal cirri extending posteriorly to chaetiger 4 (3–4). Anteroventral cirri slightly longer than palpophore, as wide and long as posteroventral cirri. Posterodorsal cirri longest, extending posteriorly to chaetiger 6 (5−11). Posteroventral cirri extending over half of prostomial posterior region. Dorsal cirrophores of tentacular cirri cylindrical; posterodorsal cirrophores 1.5 × as long as wide, slightly longer than anterodorsal cirrophores. Ventral cirrophores ring-shaped; posteroventral cirrophores shortest and narrowest, three-quarters as wide as anteroventral cirrophores.

PROBOSCIS. Everted ( Fig. 3 B−C), with maxillary and oral rings cylindrical, wider than long. Jaws denticulate, dark brown amber, 8 (7−8) short, with blunt tips ( Fig. 3D ); inner margin of fang curved; 2 canals emerging from pulp cavity ( Fig. 3D ). Paragnaths dark brown on both maxillary and oral rings ( Fig. 3 B−C); consisting of uniform-base cones, except crescent-shaped bars on area VI; plate-like basements absent. Area I: 1 (1−2), sole cone or sometimes two in longitudinal line ( Fig. 3B ). Areas II (left): 6 (4−7), II (right): 8 (4−7), two or three irregular rows of uneven cones in small triangular patch, inner cones thicker and longer ( Fig. 3B ). Area III: 10 (10−11), two (or three) slightly regular transverse rows of uneven cones in rectangular patch, distal cones smaller, with 2 (1−2) isolated lateral paragnaths, distal one much smaller ( Fig. 3C ). Areas IV (left): 10 (9−10), IV (right): 10 (9−11), two (or three) irregular rows of uneven cones in slightly crescent patch ( Fig. 3C ). Area V: 3 (3−4), triangular patch of even cones, two proximal cones in transverse row and single distal cone (sometimes almost linear patch) ( Fig. 3B ). Areas VI (left): 1, VI (right): 1, transverse crescent-shaped bar ( Fig. 3B ). Areas VIIVIII: 26 (22–26), paragnaths in two well-separated anterior and posterior bands of even cones; anterior band consisting of one (furrow) transverse row, one single cone on each furrow; posterior band with two (furrow and ridge) transverse rows slightly displaced from each other, furrow row proximal with one cone on each region, ridge row distal with one or two cones on regions A and B, and one cone in remaining regions ( Fig. 3C ). Ridges of areas VI – V – VI with π -shaped pattern. Gap between area VI and areas VII – VIII broad, as wide as palpophore width. Paired oesophageal caeca present ( Fig. 3E ).

NOTOPODIA. Consisting of dorsal cirrus, dorsal ligule (distal and proximal regions), and median ligule in biramous parapodia; notopodial prechaetal lobe absent.

DORSAL CIRRI. Cirriform, longer than proximal region of dorsal ligule and extending beyond distal region of dorsal ligule in all chaetigers ( Fig. 3F–H ); 1.5 × as long as distal region of dorsal ligule throughout, except 2–2.5 × longer in posteriormost chaetigers ( Fig. 3J ); attached to one-third of dorsal ligule in anterior chaetigers ( Fig. 3G ), medially in middle chaetigers ( Fig. 3H ), two-thirds in posterior chaetigers ( Fig. 3I ), three-quarters in posteriormost chaetigers ( Fig. 3J ).

DORSAL LIGULES. Distal region longer than proximal region in anterior chaetigers ( Fig. 3 F−G), becoming shorter than proximal one towards posterior end, 2 / 5 as long as proximal region in posteriormost chaetigers ( Fig. 3J ). Proximal region compressed in anterior and middle chaetigers ( Fig. 3 G−H), distended and sub-oval in following chaetigers ( Fig. 3 I−J); one prominent ovoid and one irregular patch of dark brown glands in all chaetigers, covering ¾ of ligule area ( Fig. 3G, I–J ). Distal region becoming shorter towards posterior end ( Fig. 3F–H ); bluntly conical in anteriormost and anterior chaetigers ( Fig. 3G ), narrowly fusiform in middle chaetigers ( Fig. 3H ), conical in following chaetigers ( Fig. 3 I−J); subequal to median ligule in most chaetigers, slightly longer in posteriormost chaetigers.

MEDIAN LIGULES. Well developed and long throughout body, bluntly conical in anterior and middle chaetigers ( Fig. 3 G−H), becoming slightly narrower and acuminate in following chaetigers ( Fig. 3 I−J).

NEUROPODIA. Consisting of neuroacicular ligule with superior and inferior lobes, ventral ligule, and ventral cirrus; postchaetal lobe reduced throughout ( Fig. 3F–J ).

NEUROACICULAR LIGULES. Sub-rectangular throughout, truncate in anterior and middle chaetigers, becoming sub-rounded in following chaetigers; shorter than ventral ligule in most chaetigers ( Fig. 3G– I ), subequal to ligule in posteriormost chaetigers ( Fig. 3J ); neuroacicular ligule 1.5–1.8 × as wide as ventral ligule in all chaetigers.

SUPERIOR LOBES. Rounded ( Fig. 3 F−G), slightly longer than inferior lobe in anteriormost chaetigers, shorter in following chaetigers.

INFERIOR LOBES. Rounded ( Fig. 3 F−I), slightly longer than neuroacicular ligule in anteriormost and anterior chaetigers, subequal in following chaetigers.

VENTRAL LIGULES. Well developed throughout, distinctly shorter than median ligule in all chaetigers ( Fig. 3G–J ); digitiform and thick in anteriormost chaetigers, bluntly conical in anterior chaetigers, becoming narrowly fusiform in following chaetigers.

VENTRAL CIRRI. Long and slender throughout; subequal to ventral ligule in anteriormost chaetigers ( Fig. 3F ), ⅔ as long as ligule in anterior chaetigers ( Fig. 3G ), half as long as ligule in following chaetigers ( Fig. 3H–J ).

ACICULAE. Mostly dark brown to black throughout. Notoaciculae absent in first 2 chaetigers ( Fig. 3F ). Notoaciculae distinctly shorter than neuroaciculae throughout ( Fig. 3G–J ). Neuroaciculae nearly as long as median ligule in anteriormost chaetigers, distinctly shorter in following chaetigers, ⅔ as long as ligule in anterior chaetigers, ½ as long as ligule in following chaetigers.

NOTOCHAETAE. All homogomph spinigers throughout; 8–10 spinigers present in anterior chaetigers, 5–7 in middle chaetigers, and 3–4 in posterior chaetigers.

UPPER NEUROCHAETAE. Consisting of homogomph spinigers and heterogomph falcigers throughout; 3–4 spinigers present in anteriormost, anterior and middle chaetigers, 4–5 spinigers in following chaetigers; 3–4 falcigers present in anteriormost and anterior chaetigers, 5–7 falcigers in following chaetigers.

LOWER NEUROCHAETAE. Consisting of heterogomph spinigers and heterogomph falcigers throughout; 1–2 spinigers present in anteriormost chaetigers, 3–4 spinigers in anterior chaetigers, 1–2 spinigers in following chaetigers; 5–7 falcigers present in all chaetigers.

BLADES OF CHAETAE. Both homogomph and heterogomph spinigers ( Fig. 3K ) long, finely serrated, with teeth evenly spaced. Heterogomph falcigers tapering with pointed tip and even teeth; slender and medium length, straight, entirely serrated ( Fig. 3 L−M). Shaft of falcigers camerated, with cavity divided sub-distally into three distinct longitudinal partitions ( Fig. 3M ).

PYGIDIUM. With long anal cirri, as long as last 6–7 chaetigers.

Variation

Total body length: 42–79 mm. Length to chaetiger 10: 3.9–7.2 mm. Body width at chaetiger 10: 1.2– 2.3 mm. Number of total chaetigers: 85–128. Longest tentacular cirri extending to chaetiger 5–11 (mean 8–9). Jaws with 6–8 (mean 7) teeth. Number and pattern of paragnaths: area I: 1–2 (mean 1–2); area II: 4–8 (mean 5–6); area III: 10–11 (mean 10) in central patch, 1–2 cones isolated laterally; area IV: 8–11 (mean 9–10); area V: 3 (rarely 4); area VII–VIII: 22–26 (mean 23–25). Anal cirri as long as last 5–8 chaetigers.

Remarks

Among all the 1A members of Perinereis , P. misrai sp. nov. resembles P. falsovariegata Monro, 1933 from South Africa and P. villalobosi Rioja, 1947 from the Mexican Pacific by having dorsal cirri distinctly projecting beyond the distal region of dorsal ligule in mid-body parapodia, neuropodial superior lobes, areas VI–V–VI ridge pattern π-shaped, and by lacking notopodial prechaetal lobes. However, P. misrai is distinguished from P. falsovariegata and P. villalobosi by the paragnath count in areas III, IV, V and VII–VIII, the laterally isolated groups of paragnaths in area III, and the number of rows in the anterior band of areas VII–VIII. Perinereis misrai has fewer paragnaths on areas III (10−11), IV (9−11) and VIIVIII (21–26) than P. falsovariegata (III: 20−24, IV: 23−27, VII–VIII: aprox. 30) and P. villalobosi (III: 17−57, IV: 15−54, VII–VIII: 41–45). In P. misrai , area V has three paragnaths, contrary to one (rarely two) in P. falsovariegata and P. villalobosi . In P. misrai , area III has laterally isolated paragnaths, in contrast to their absence in P. falsovariegata and P. villalobosi . Finally, in P. misrai , the areas VII–VIII has an anterior band with only a furrow row of paragnaths, contrary to two rows (one on furrows and one on ridges) in P. falsovariegata and P. villalobosi .

Perinereis misrai sp. nov. is the first species of the subgroup 1A originally described from the West and South Indian Shelf province and the third described from the Western Indo-Pacific realm (sensu Spalding et al. 2007), just after P. arabica Mohammad, 1971 and P. iranica Bonyadi-Naeini et al., 2018 , both from the Persian Gulf. Perinereis misrai can be distinguished from these two species with biogeographic affinities by the size of dorsal and tentacular cirri, the number of paragnaths in several areas, and the occurrence of isolated groups of paragnaths in area III. In P. misrai , the dorsal cirri are 2–2.5 × as long as the distal region of dorsal ligule in posterior chaetigers, contrary to up to 1.5 × longer in P. arabica and P. iranica . In P. misrai , the tentacular cirri are longer (extending to chaetigers 6–11) than those of the two species (extending to chaetiger 5 in P. arabica and chaetiger 2 in P. iranica ). In P. misrai , the areas of the maxillary ring have fewer paragnaths (area I: 1−2, area II: 4−7, area III: 10−11, area IV: 9−11) than in P. arabica (area I: 16, area II: 18−20, area III: 16, area IV: 23) and P. iranica (area I: 4−6, area II: 12−16, area III: 30−45, area IV: 40−47). Finally, P. misrai has area III with laterally isolated paragnaths, in contrast to their absence in P. arabica and P. iranica .

Habitat

Specimens of this new species were found in the same habitat as the previous species (see above).

Figures

Fig. 3. Perinereis misrai sp. nov. from Mumbai, Maharashtra, India. A–C, F–N. Holotype (MSUB- ZL-AN-PCh-06), atoke. D–E. Paratype (ZSI-WRC ANN/27), atoke. A. Whole body in dorsal view. B. Anterior end and everted proboscis in dorsal view. C. Everted proboscis in ventral view. D. Left jaw in ventral view, arrows pointing to inner canals. E. Paired oesophageal caeca (arrows) in dorsal view. F–J. Parapodia in anterior view; numbers refer to the chaetiger. K. Heterogomph spiniger from neuropodial subacicular fascicle (chaetiger 25). L. Heterogomph falciger from neuropodial subacicular fascicle (chaetiger 61). M. Heterogomph falciger from neuropodial supracicular fascicle (chaetiger 61). Scale bars: A = 9 mm; B = 0.45 mm; C–D, N = 0.5 mm; E = 0.35 mm; F, J = 0.15 mm; G–I = 0.22 mm; K = 18 μm; L–M = 10 μm.