Neanthes mossambica ( Day, 1957 )

Villalobos-Guerrero, Tulio F., Kara, Jyothi & Idris, Izwandy, 2021, Redescriptions of Neanthes Kinberg, 1865 (Annelida: Errantia: Nereididae) species from worldwide regions, European Journal of Taxonomy 760 (1), pp. 101-135 : 123-129

Neanthes mossambica ( Day, 1957)

Fig. 5

Nereis (Neanthes) mossambica Day, 1957: 78–80 , text-fig. 3e–h, j–k [type locality: Morrumbene Estuary, Mozambique].

Nereis (Neanthes) mossambica – Hartman 1959: 265. — Day 1967: 318–320, fig. 14.8.g–k.

Neanthes mossambica – Fauchald 1972: 409 (group IIB 2b). — Wilson 1984: 226 (group IIB 2b) (all previous in species list). — Villalobos-Guerrero & Idris 2021: 560 (table 1), 562 (table 2).

Nereis mossambica – Day 1974: 73 (table 5), 87 (habitat).

Type material

Holotype MOZAMBIQUE • atokous ♀; Inhambane, Morrumbene Estuary ; NHMUK 1961.16.22 .

Paratype MOZAMBIQUE • 1 atokous; same collection data as for holotype; SAM-A-20984 .

Comparative material

Syntypes de Neanthes indica brunnea ( Day, 1957)

MOZAMBIQUE • 2 atokous; Inhambane, Morrumbene Estuary ; J.H. Day leg.; NHMUK 1961.16.23 • 1 atokous; same collection data as for preceding; SAM-A-20983 .

Description

COLOUR AND MEASUREMENTS. Holotype atokous female, complete but with regenerating posterior end, in good condition, 32 (12) mm TL, 8 (4) mm L15, 1.3 (1) mm W15, with 68 (47) chaetigers. Body colour yellowish, with brownish pigmentation in dorsum of prostomium, palps, and present throughout in dorsum of anterior segments ( Fig. 5A–B ).

PROSTOMIUM. Campanulate, 1.4 times longer than wide ( Fig. 5B ); anterior end broad, distally complete; anterolateral gap beside palpophore broad, 1.5 times as wide as antennal diameter; dorsal groove distinct, shallow, running through distal three-quarters of prostomium. Nuchal organs deeply embedded, medium size, subequal to diameter of posterior pair of eyes.

PALPOPHORES. Sub-conical, longer than wide, as long as four-fifths of entire prostomium ( Fig. 5A ); with distinct sub-distal transverse groove. Palpostyles ovoid, thin, with diameter as wide as one-fifth of palpophore.

ANTENNAE. Tapered, slender, long, extending forwards slightly beyond end of palpophore and posteriorly to half-length of prostomium; antennae well separated, with gap as wide as basal diameter of antennae.

EYES. Paired eyes blackish, arranged in a trapezoid form ( Fig. 5B ); gap between both pairs one-third as wide as diameter of posterior pair of eyes; anterior pair of eyes sub-rounded, 1.2 times as wide as basal diameter of antennae, gap between both eyes 3.5 times as wide as diameter of eyes, with lens slightly distinct, whitish, covering 10% of eye; posterior pair of eyes rounded, as wide as basal diameter of antennae, with lens barely distinct, dark, placed in middle of eye and covering 15% of it.

APODOUS ANTERIOR SEGMENT. Segment 3.5 times wider than long, 1.4 times as long as chaetiger 1, with rounded anterior margin ( Fig. 5B ), dorsum without marked transverse wrinkle.

TENTACULAR CIRRI. Slender, smooth ( Fig. 5B ); postero-dorsal cirri extending posteriorly to chaetiger 8 (4), twice as long as antero-dorsal cirri; antero-dorsal cirri extending posteriorly to chaetiger 4 (2); postero-ventral cirri extended over opposite side of prostomium; antero-ventral cirri nearly as long as postero-ventral cirri and extending slightly beyond palpophore; dorsal cirrophores cylindrical, ventral cirrophores ring-shaped, postero-dorsal cirrophores 1.5 times as long as antero-dorsal cirrophores, antero-ventral cirrophores 1.5 times as wide as postero-ventral cirrophores.

PHARYNX. Non-everted, previously dissected. Jaws reddish in distal quarter, remaining amber, with 8 (5) blunt, wear denticles; pulp cavity with two canals. Brownish conical paragnaths on maxillary and oral rings ( Fig. 5C ), except reddish in areas VII–VIII; merged paragnaths and plate-like basements absent. Area I: 6 (2), triangular patch of uneven cones, single distal cone smaller; areas IIa: 15 (15) and IIb: 15 (17), three irregular rows of uneven cones in sub-triangular patch, cones in outer-most row larger ( Fig. 5C ); area III: 32 (23), four slightly regular rows of uneven cones in rectangular patch, without distinct laterally-isolated cones, distal cones smaller ( Fig. 5C ); areas IVa: 31 (25) and IVb: 32 (24), bow-shaped patch with proximal half consisting of four irregular rows and distal half with three irregular rows of uneven cones ( Fig. 5C ); area V: 0 (0) ( Fig. 5C ); areas VIa: 1 (1) and VIb: 1 (1), coarse cone, distally wear in VIa ( Fig. 5C–D ); areas VII–VIII: 50 (42), two well-separated bands of cones, with anterior band consisting of two transversely slightly displaced rows of coarse cones (furrow row and ridge row with one cone on each region) ( Fig. 5C ), and posterior band with three transverse rows slightly displaced from each other (furrow row middle with one cone on each region, distal ridge row with two or three coarse cones on each region, proximal ridge row with one small cone on each region) ( Fig. 5C ). Areas VI–V–VI ridge pattern, λ-shaped. Gap between area VI and areas VII–VIII narrow, as wide as distal end of palpophore.

PAIRED OESOPHAGEAL CAECA. Absent.

PARAPODIA. Without glandular, dorsal patches. Notopodia consisting of dorsal cirrus, dorsal ligule (distal and proximal), notopodial prechaetal lobe, and median ligule in biramous parapodia. Neuropodia consisting of neuroacicular ligule with inferior and postchaetal lobes, ventral ligule, and ventral cirrus; superior lobe absent throughout.

DORSAL CIRRI. Cirriform, long, extending markedly beyond distal region of dorsal ligule throughout ( Fig. 5E–I ); dorsal cirri 5–5.5 times as long as proximal region of dorsal ligule in anteriormost and anterior parapodia ( Fig. 5E–F ), 3–4 times as long as that in middle parapodia ( Fig. 5G–H ), 2–2.5 times as long as that in posterior parapodia ( Fig. 5I ); attached basally to dorsal ligule in anteriormost parapodia ( Fig. 5E ), one-third in anterior parapodia ( Fig. 5F ), medially in following parapodia ( Fig. 5G–I ).

DORSAL LIGULE. Proximal region even towards posterior end ( Fig. 5E–I ); shorter than distal region of dorsal ligule in anteriormost and anterior parapodia ( Fig. 5E–F ), as long as that in following parapodia ( Fig. 5G–I ); glandular patches absent. Distal region well developed with similar length throughout ( Fig. 5E–I ); subulate, slender, as long as median ligule in anterior parapodia, conical and smaller than that in following parapodia; projecting beyond notoacicula throughout; glandular patches absent.

NOTOPODIAL PRECHAETAL LOBE. Present from parapodia 5 to parapodia 18; bluntly conical, half as long as median ligule in anterior parapodia ( Fig. 5F ), then reducing and tapering gradually to notoacicular process that disappears in about parapodia 36 ( Fig. 5H–I ).

MEDIAN LIGULE. Subulate, slender in anterior parapodia ( Fig. 5E–F ), conical in following parapodia ( Fig. 5G–I ), becoming slightly longer from middle parapodia towards posterior end.

NEUROACICULAR LIGULE. Smaller than ventral ligule in anteriormost parapodia ( Fig. 5E ), as long as in following parapodia ( Fig. 5F–I ), twice as wide as ventral ligule throughout.

NEUROPODIAL INFERIOR LOBE. Slightly developed and longer than neuroacicular ligule in first 14 parapodia ( Fig. 5E–F ), absent in following chaetigers.

NEUROPODIAL POSTCHAETAL LOBE. Present throughout; bluntly conical, except conical in posterior parapodia; as long as neuroacicular ligule in anteriormost parapodia ( Fig. 5E ), smaller than that in following parapodia ( Fig. 5F–I ).

VENTRAL LIGULE. Well-developed and conical throughout ( Fig. 5E–I ); smaller than median ligule throughout, more distinct in posterior parapodia ( Fig. 5I ); extending beyond distal region of dorsal ligule in parapodia 1 and 2 ( Fig. 5E ).

VENTRAL CIRRI. Cirriform, slender; two-thirds as long as ventral ligule in anteriormost and anterior parapodia ( Fig. 5E–F ), one-third as long as that in middle parapodia, levelling base of that in posterior parapodia.

ACICULAE. Black, with basal end uncoloured. Notoaciculae absent in first two chaetigers ( Fig. 5E ). Neuroaciculae extending beyond distal end of notoaciculae throughout, more distinct in anteriormost and anterior parapodia ( Fig. 5F ), with proximal half 1.2–1.4 times as wide as notoaciculae.

NOTOCHAETAE. All homogomph spinigers ( Fig. 5J ); 18–20 spinigers present in anterior parapodia, 13–16 spinigers in middle parapodia, 5–9 spinigers in posterior parapodia.

SUPRACICULAR NEUROCHAETAE. Consisting of homogomph spinigers and heterogomph falcigers ( Fig. 5K ), both present throughout; 5–6 spinigers in anteriormost parapodia, 11–12 spinigers in anterior parapodia, 6–9 spinigers in middle parapodia, 4–7 spinigers in posterior parapodia; 3–4 falcigers present in anteriormost and anterior parapodia, 2–3 falcigers in middle parapodia, 1–2 falcigers in posterior parapodia.

SUBACICULAR NEUROCHAETAE. Consisting of heterogomph spinigers ( Fig. 5L ) and heterogomph falcigers ( Fig. 5M ), both present throughout; 4–5 spinigers in anteriormost parapodia, 6–8 spinigers in anterior and middle parapodia, 3–4 spinigers in posterior parapodia; 7–8 falcigers in anteriormost parapodia, 9–10 falcigers in anterior parapodia, 6–8 falcigers in middle parapodia, 3–4 falcigers in posterior parapodia.

BLADES. Both homogomph ( Fig. 5J ) and heterogomph ( Fig. 5L ) spinigers with blades finely serrated towards toothed edge, evenly spaced, long (B/A ratio 10.9–22.5). Heterogomph falcigers with blades of medium and long sizes (B/A ratio 1.7–2.3), slender, convex, terminal tooth blunt with inconspicuous tendon; serrations present in about half to two-fifths (0.39–0.48; Fig. 5K, M ) of total blade length. Shaft of supracicular falcigers thicker than subacicular ones in posterior parapodia; camerated, with cavity divided sub-distally into two longitudinal partitions ( Fig. 5M ).

PYGIDIUM. In regeneration, with anal cirri as long as last 6 chaetigers; cirrophores of anal cirri barely developed.

Remarks

Among all the currently know species of Neanthes , N. mossambica from Mozambique resembles N. chilkaensis from India, N. indica brunnea from Mozambique, and N. talehsapensis from the Gulf of Thailand. These species share proximal region of dorsal ligule of similar size throughout the body (or slightly enlarged in posterior parapodia), presence of neuropodial postchaetal and notopodial prechaetal lobes at least in some anterior chaetigers, absence of neuropodial superior lobes, areas VII–VIII with two well-defined bands of more than 20 paragnaths, and area I with two or more paragnaths (see Villalobos- Guerrero & Idris 2021: table 2).

Nonetheless, N. mossambica is distinguishable from them all by the following diagnostic features: (I) one paragnath on area VI, in contrast to 5–7 in N. chilkaensis , 4–6 in N. indica brunnea , 4–5 in N. talehsapensis ; (II) the absence of oesophageal caeca, in contrast to its presence in N. chilkaensis and N. indica brunnea ; (III) the area VI with conical paragnaths only, in contrast to both conical and p-bars in N. chilkaensis ; (IV) the smooth tentacular cirri, in contrast to multi-articulated in N. chilkaensis ; (V) the area V without paragnaths, in comparison to their presence in N. chilkaensis ; (VI) the area VII– VIII with conical paragnaths only, in comparison to p-bars only in N. chilkaensis ; (VII) the prostomium longer than wide, in contrast to that as long as wide in N. talehsapensis ; (VIII) the aciculae mostly black, in contrast to those rather pale colour in N. talehsapensis ; (IX) the notopodial prechaetal lobes distinctly smaller than median ligule throughout, in contrast to those that are subequal in anterior chaetigers of N. talehsapensis ; (X) 23–32 paragnaths on area III, in comparison to 5–9 in N. indica brunnea ; (XI) the dorsal cirri extending markedly beyond distal region of dorsal ligule, in contrast to those not extending beyond in N. indica brunnea ; (XII) the presence of neuropodial postchaetal lobe throughout, in contrast to that in anterior chaetigers only in N. indica brunnea ; (XIII) the heterogomph falciger blades with blunt terminal tooth and inconspicuous tendon in middle and posterior parapodia, in contrast to those with hammer-headed terminal tooth and distinct tendon in N. indica brunnea ; (XIV) the antennae well separated from each other, in comparison to those closely together in N. indica brunnea ; and (XV) the dorsum of segments with pigmentation bands, in contrast to a pigment band present only in the apodous segment of N. indica brunnea .

Neanthes mossambica was briefly described, scarcely illustrated and placed within the subgenus Nereis (Neanthes) by Day (1957) using two atokous specimens collected from the Morrumbene Estuary, Mozambique. Both the holotype and paratype match the original description. The species has always been considered within Neanthes , either recognized at the subgeneric ( Hartman 1959; Day 1967; Raghunath 1976) or generic ( Pillai 1965; Fauchald 1972; Wilson 1984) level, except Day (1974) who for an unknown reason enlisted the species as Nereis mossambica . The combination Neanthes mossambica that prevails nowadays was used for the first time by Pillai (1965) while comparing his new species Neanthes manatensis from Manat, Philippines. Both species are morphologically similar, however, as Pillai (1965) aptly mentioned, they can be distinguished by the number of paragnaths on the area I, and also on areas III and VII–VIII.

Neanthes mossambica was briefly characterised by Day (1967) but based solely on the original description. No more attempt to describe the morphology of the species was performed. The original description includes a short, implicit comparison with three other Neanthes species (formerly in Nereis ): Neanthes chilkaensis , N. talehsapensis , and N. glandicincta ( Southern, 1921) from near Calcutta, India. The first two species were distinguished above in detail from N. mossambica . Neanthes glandicincta was recently redescribed using a syntype and specimens from Myanmar and Singapore ( Lee & Glasby 2015) and characterised with individuals from Malaysia and Thailand ( Ibrahim et al. 2019; Azmi et al. 2021). Neanthes mossambica can be easily distinguished from N. glandicincta by the absence of neuropodial superior lobe (present in N. glandicincta ), the presence of two bands of paragnaths on area VII–VIII (one or none bands in N. glandicincta ), the presence of heterogomph falcigers throughout the body (absent in anterior parapodia in N. glandicincta ), among other features.

The species has been recorded in India ( Raghunath 1976) and Bangladesh ( Muir & Hossain 2014), although these records are questionable since no species’ characterisations were provided.

Distribution

Mozambique: Tinga-Tinga and Fern Bank, both in Morrumbene Estuary ( Day 1974).

Ecology

Estuarine habitats, among mangrove swamps ( Day 1974).

Reproduction

Unknown.

Figures

Fig. 5. Neanthes mossambica (Day, 1957). Holotype (NHMUK 1961.16.22) from Morrumbene, Mozambique, atokous female. A. Entire body in dorsal view. B. Anterior end in dorsal view. C. Noneverted pharynx in ventral view (arrow indicates p-bar). D. Area VI of non-everted pharynx in ventral view (arrow pointing anteriorly). E. Left parapodium from chaetiger 1 in posterior view. F. Right parapodium from chaetiger 9 in anterior view. G. Left parapodium from chaetiger 21 in posterior view. H. Right parapodium from chaetiger 40 in anterior view. I. Right parapodium from chaetiger 63 in anterior view with ventral cirri contracted and hidden behind the neuroacicular ligule. J. Homogomph spiniger from notochaetae (chaetiger 9). K. Heterogomph spiniger from subacicular neurochaetae (chaetiger 9). L. Heterogomph falciger from supracicular neurochaetae (chaetiger 9). M. Heterogomph falciger from subacicular neurochaetae (chaetiger 9). Roman numerals refer to the areas and Arabic numbers to chaetigers. Scale bars: A = 2 mm; B = 1 mm; C = 0.5 mm; D = 0.1 mm; E–I = 0.2 mm; J–M = 20 µm.