Nereis occidentalis Hartman, 1945

Salazar-Vallejo, Sergio I., León-González, Jesús Angel De & Conde-Vela, Víctor M., 2021, Revision of the species confused with “ Nereis falsa ” de Quatrefages, 1866 (Annelida, Nereididae), European Journal of Taxonomy 779, pp. 1-70 : 49-53

Nereis occidentalis Hartman, 1945

Fig. 17

Nereis pelagica occidentalis Hartman, 1945: 20 , pl. 4 figs 1–6.

Nereis pelagica occidentalis – Hartman 1951:46.

Nereis (Nereis) occidentalis – Pettibone 1956: 291 (new status; partim).

Nereis falsa – Day 1973: 41. — Gardiner 1975: 152, fig. 15s–u.

Diagnosis

Nereis with posterior eyes completely exposed; tentacular belt 1.5 × as long as first chaetiger; tentacular cirri long, reaching chaetiger 8; jaws with 7–9 teeth; pharyngeal area II with 14–15 paragnaths in 2 rows, areas VII–VIII with 46 paragnaths in 3–4 transverse rows, basal row with larger paragnaths; median chaetigers with notopodial ligules conical, blunt; ventral ligules in median and posterior chaetigers markedly longer than neuracicular ligules.

Material examined

Holotype UNITED STATES • atoke; Sheepshead Shoal, Beaufort , North Carolina; 34°42′22″ N, 76°36′11″ W; 7 Jun. 1940; O. Hartman leg.; in colonies of Petaloproctus socialis Andrews , 1891; LACM 836 .

Paratypes UNITED STATES • 95 atokes; same collection data as for holotype; LACM 837 .

Description

BODY. Holotype (LACM 836) atokous, complete, 42 mm long, 2 mm wide at chaetiger 10 excluding parapodia, with 93 chaetigers. Body pale, dorsum with a light brown striate pattern along anterior chaetigers ( Fig. 12A ). Paratype (LACM 837) atokous complete, 40 mm long, 2 mm wide excluding parapodia, with 68 chaetigers.

PROSTOMIUM. Pyriform, longer than wide; eyes blackish, rounded, of similar size, in trapezoidal arrangement, about ⅐ prostomial width ( Fig. 17A ). Antennae half as long as prostomium, without gap between them, swollen basally, slightly shorter than palps. Palpophores 1.5× as long as wide, palpostyles subcylindrical ( Fig. 17A ).

TENTACULAR BELT. 1.5× as long as first chaetiger; anterior margin not covering posterior eyes ( Fig. 17A ). Tentacular cirri smooth, longest ones reaching chaetiger 8.

PHARYNX. Everted. Jaws brown with 7–9 accesory teeth. Paragnath formula: I: 3 in tandem; II: 14–15 in 3 oblique lines; III: 25 in ellipse; IV: 23–25 in a crescent-shaped group; V: 0; VI: 5– 3 in diamond; VII–VIII: 46 cones in 3–4 transverse rows, basal row with larger paragnaths.

PATTERN OF PARAPODIAL LIGULES. Anterior chaetigers with ligules tapered, blunt; median and posterior chaetigers with ligules subconical, slightly blunter in median ones, progressively sharper. Ligules with contorted glandular tubules.

CHAETIGERS 1–2. With neuraciculae only ( Fig. 17E ); with both noto- and neuraciculae thereafter. Dorsal cirrus as long as ventral one, 2 × as long as dorsal ligule. Dorsal and ventral ligules subequal, digitiform, 3 × as long as neuracicular ligule. Neuracicular ligule subconical; postchaetal lobe digitiform, shorter than neuracicular ligule. Supracicular neurochaetae: 10–12 homogomph spinigers and 3–4 heterogomph falcigers; subacicular neurochaetae: 8–9 heterogomoph spinigers, falcigers not observed.

ANTERIOR PARAPODIA ( Fig. 17F ). Dorsal cirrus longer than ventral cirrus; dorsal cirrus twice as long as dorsal ligule, ventral cirrus as long as ventral ligule. Dorsal and median ligules subequal; dorsal one subconical, blunt, 1.2× as wide as long; median one rounded, 1.2 × as long as neuracicular ligule. Neuracicular ligule subconical, as long as wide, 1.2× as long as ventral ligule; postchaetal lobe rounded, shorter than neuracicular ligule; ventral ligule digitiform, 1.2 × as wide as long. Notochaetae 16–20 homogomph spinigers. Supracicular neurochaetae: 15–18 homogomph spinigers and 4–6 heterogomph falcigers; subracicular neurochaetae: one heterogomph spiniger and 6–9 heterogomph falcigers with blades short ( Fig. 17F ).

MEDIAN PARAPODIA ( Fig. 17G ). With dorsal cirrus more than 2 × as long as ventral one, 2× as long as dorsal ligule. Dorsal and median ligules subequal, subconical; dorsal ligule 1.3× as wide as long; median ligule 1.2 × as long as wide, 3 × as long as neuracicular ligule; notacicular papilla present. Neuracicular ligule rounded to subconical; rounded postchaetal lobe, shorter than neuracicular ligule; ventral ligule subconical, 1.2× as long as wide, 1.2× as long as neuracicular ligule, 2 × as long as ventral cirrus. Notochaetae 6–8 homogomph spinigers. Supracicular neurochaetae: 11 homogomph spinigers and 2–3 thick heterogomph falcigers, blades denticulate, distal tooth incurved, fused to blade; subacicular neurochaetae: 3–4 heterogomph spinigers, thin, short, and 9–12 thick heterogomph falcigers, denticulate along cutting edge, distal tooth incurved, fused to blade.

POSTERIOR PARAPODIA ( Fig. 17H–I ). With dorsal cirrus inserted medially, 1.5 × as long as dorsal ligule. Dorsal and median ligules subequal, subconical, tapered; dorsal ligule 1.3× as long as wide; median ligule 2× as long as wide, 3.5 × as long as neuracicular ligule; notoacicular papilla absent. Neuracicular ligule subconical, as long as wide; ventral ligule subconical, tapered, 1.5× as long as wide, 2 × as long as neuracicular ligule, subequal to ventral cirrus. Notochaetae: 2–4 homogomph spinigers and 1 homogomph falciger ( Fig. 17J ), blades with 12–14 narrow teeth, stout distal tooth, incurved, fused to blade. Supracicular neurochaetae: 6–8 homogomph spinigers and 1–2 heterogomph falcigers similar to those of median parapodia; subacicular neurochaetae: 4–6 heterogomph spinigers and 2 heterogomph falcigers, similar to those of median parapodia ( Fig. 17K–L ).

POSTERIOR REGION. Tapered. Pygidium damaged, anus terminal; anal cirri as long as last 17 chaetigers ( Fig. 17B ).

Remarks

Hartman (1945) regarded this species as a subspecies of Nereis pelagica Linnaeus, 1758 , but Pettibone (1956) thought they were different and regarded it as a distinct species, although further comments about this conclusion were not given. Because there is no available redescription of N. pelagica , here the description and illustrations in Chambers & Garwood (1992: 38–40) are followed.

Nereis occidentalis Hartman, 1945 differs from N. pelagica in the following features: N. occidentalis has larger paragnaths basally in pharyngeal areas VII–VIII, whereas N. pelagica has larger paragnaths distally; in N. occidentalis , the ventral ligules are longer than the neuracicular ligules in middle and posterior chaetigers, whereas in N. pelagica they are subequal; in N. occidentalis , parapodial ligules are subconical with pointed tips, whereas in N. pelagica they are digitiform with blunt tips; in N. occidentalis , the notopodial homogomph falcigers have several narrow teeth and a distal, stout tooth with a tendon, whereas in N. pelagica these falcigers are not denticulate.

As discussed elsewhere ( Conde-Vela & Salazar-Vallejo 2015), Pettibone (1956) raised this species to species level and described it with specimens from Laguna Madre, Texas, Gulf of Mexico. Some features of those specimens resemble those of N. occidentalis , such as the length of the tentacular cirri, the arrangement of paragnaths on the pharynx (although she did not indicate most paragnath numbers) and the shape of blades of both notopodial and neuropodial falcigers. However, there are some relevant parapodial differences between specimens from Texas and typical N. occidentalis : in the anterior chatigers of N. occidentalis , median ligules are rounded and neuracicular ligules are as long as ventral ligules, whereas in specimens from Texas the median ligules are digitiform and neuracicular ligules are shorter than ventral ligules; in the middle chaetigers of N. occidentalis , medial ligules are 3 × as long as neuracicular ligules, whereas in specimens from Texas, median ligules are 2× as long as neuracicular ligules; in the posterior chaetigers of N. occidentalis , ventral ligules are 2× as long as neuracicular ligules, whereas in specimens from Texas, ventral ligules are shorter than neuracicular ligules. These variations might be intraspecific variations, but clarifying this will depend of a future study. Taylor (1984: 31.39, fig. 31.38) identified specimens from the Gulf of Mexico Florida coasts as Nereis falsa , and he included a plate combining figures made of North Carolinean specimens by Hartman (1945) and Gardiner (1975); Taylor’s specimens are similar to ones from Texas, requiring a further examination of them to clarify the affinities between these local populations.

Dueñas-Ramírez (1980) reported N. occidentalis from the Colombian Caribbean and included a brief description and illustration; his specimens differ from N. occidentalis in having larger overlapping eyes, in contrast to the smaller and separated eyes and dorsal ligules with relatively narrow bases in the Carolinian specimens of N. occidentalis .

Distribution

North Carolina, United States.

Figures

Fig. 17. Nereis occidentalis Hartman, 1945. A–B, I: holotype (LACM 836); C–H, J–L: paratype (LACM 837). A. Anterior region, dorsal view. B. Posterior region, dorsal view. C. Pharynx, dorsal view. D. Same, ventral view. E. Chaetiger 2, right parapodium, posterior view. F. Chaetiger 11, right parapodium, posterior view. G. Chaetiger 34, right parapodium, posterior view. H. Chaetiger 62, right parapodium, posterior view. I. Chaetiger 87, right parapodium, posterior view. J. Same, notopodial homogomph falciger. K. Same, neuropodial subacicular heterogomph spiniger. L. Same, neuropodial subacicular heterogomph falciger.

Fig. 12. Nereis riisei Grube & Örsted in Grube, 1857, non-type specimen (ECOSUR P2256). A. Anterior region, dorsal view. B. Anterior end, dorsal view. C. Chaetiger 2, left parapodium, anterior view. D. Chaetiger 30, left parapodium, anterior view. E. Chaetiger 90, left parapodium, anterior view. F. Chaetiger 168, left parapodium, anterior view. G. Posterior region, dorsal view, after Shirlastain-A staining.