Nereis marginata Grube & Örsted in Grube, 1857

Figs 8–9

Nereis (Nereis) marginata Grube & Örsted in Grube, 1857: 160–161.

Nereis (Nereis) marginata – Salazar-Vallejo & Eibye-Jacobsen 2012: 1396.

Diagnosis

Nereis with posterior eyes partially covered by anterior margin of tentacular belt; tentacular belt 2× as long as first chaetiger; tentacular cirri short, reaching chaetiger 4; pharyngeal areas VII–VIII with 5 large paragnaths in a single row; posterior chatigers with dorsal ligules 2–3 × as wide as median ones.

Material examined

Holotype UNITED STATES VIRGIN ISLANDS • Saint John (the vial has a label signed by Kröyer inside that says it is Nereis riisei, i.e., a very incorrect label); Kröyer leg.; NHMD 109266 (previously ZMUC POL- 1483).

Other material

ANTIGUA AND BARBUDA • 1 spec.; NW Antigua; 17°16′ N, 62°02′ W; R/V Pillsbury, Cruise 6907, stn 967; 22 m depth; 20 Jul. 1969; ECOSUR P3119 • 1 spec.; NW Redonda Island; 17°00′ N, 62°30′ W; R/V Pillsbury, Cruise 6907, stn 956; 37 m depth; 19 Jul. 1969; ECOSUR P3119 .

COLOMBIA • 1 spec.; N Gulf of Urabá; 8°32′ N, 77°02′ W; R/V Pillsbury, Cruise 6607, stn 349; 54 m depth; 11 Jul. 1966; ECOSUR P3120 .

DOMINICAN REPUBLIC • 2 specs; R/V Pillsbury, Cruise 7006, stn 1254; 20 m depth; 14 Jul. 1970; ECOSUR P3104 • 1 spec.; Cape Beata; 17°35′ N, 71°25′ W; R/V Pillsbury, Cruise 7006, stn 1284; 20 m depth; 19 Jul. 1970; UMML 22.1176 • 1 spec.; Bahia de las Aguilas; R/V Pillsbury, 17°52′N, 71°41′W; Cruise 7006, stn 1272; 24 m depth; 18 Jul. 1970; ECOSUR P3121 • 1 spec.; S of Cabo Falso; 17°41′ N, 71°41′ W; R/V Pillsbury, Cruise 7006, stn 1271; 18 m depth; 18 Jul. 1970; ECOSUR P3122 .

GRENADA • 2 specs; S Grenada; 11°55′ N, 61°43′ W; R/V Pillsbury, Cruise 6907, stn 853; 17 m depth; 3 Jul. 1969; UMML 22.1177 .

JAMAICA • 3 specs; NE Morant Cays; 17°28′ N, 75°57′ W; R/V Pillsbury, Cruise 7006, stn 1196; 26 m depth; 3 Jul. 1970; UMML 22.1174 • 2 specs; W Pedro Bank; 17°09′ N, 78°57′ W; R/V Pillsbury, Cruise 7006, stn 1252; 26 m depth; 14 Jul. 1970; UMML 22.1175.

NICARAGUA • 1 spec.; E Nicaragua; 13°58′ N, 82°04′ W; R/V Pillsbury, Cruise 7101, stn 1343; 25 m depth; 30 Jan. 1971; ECOSUR P3117 .

TURKS AND CAICOS • 1 spec.; NE Grand Turk; 21°36′ N, 71°01′ W; R/V Pillsbury, Cruise 7106, stn 1421; 83 m depth; 19 Jul. 1971; ECOSUR P3124 .

Description

Holotype (NHMD 109266)

BODY. Atoke specimen, without posterior region, 50 mm long, 3 mm wide, 96 chaetigers.

PROSTOMIUM. Pyriform, longer than wide, dorsal groove present. Eyes in trapezoidal arrangement, with lenses, anterior eyes rounded, smaller than oval posterior ones. Antennae thin, terminal, with a small gap between them (Fig. 8A–B). Palpophores globose, directed downward, 1.5× as long as wide, palpostyles rounded.

TENTACULAR BELT. 2 × as long as first chaetiger, anterior margin slightly covering posterior eyes. Tentacular cirri smooth, longest ones reaching anterior margin of chaetiger 4 (Fig. 8A–B).

PHARYNX. Not observed, withdrawn.

PATTERN OF PARAPODIAL LIGULES. Anterior chaetigers with dorsal ligules tapered, blunt, median ligules rounded; median and posterior chaetigers with ligules subconical, becoming wider towards posterior chaetigers. Ligules with contorted glandular tubules.

CHAETIGERS 1–2. With neuraciculae only, with both noto- and neuraciculae thereafter.

ANTERIOR PARAPODIA (Fig. 8C). With dorsal cirrus basally inserted, incomplete; dorsal ligule subconical, blunt, 1.4 × as wide as long, 1.5 × as long as median ligule; prechaetal lobe absent; median ligule rounded, 1.1× as long as wide, slightly longer than neuracicular ligule. Neuracicular ligule digitiform, 2× as long as wide, slightly longer than ventral ligule; ventral ligule digitiform, slightly longer than wide. Notochaetae 9 homogomph spinigers. Supracicular neurochaetae: 6 homogomph spinigers and 2 heterogomph falcigers with blades 6.8× as long as wide, distal tooth incurved, fused to blade (Fig. 8G); subacicular neurochaetae: 6 heterogomph spinigers, 10 heterogomph falcigers with blades 8 × as long as wide, similar in size and shape as supracicular ones and 1 heterogomph falciger with blade 4.2× as long as wide, distal tooth incurved, fused to blade (Fig. 8H).

MEDIAN PARAPODIA (Fig. 8D). With dorsal cirri thin, as long as dorsal ligule; dorsal ligule subconical, tapering, 1.3× as wide as long, with massive dark glands. Median ligule subconical, blunt, as long as wide, 4× as long as neuracicular ligule. Neuracicular ligule subconical, 1.5× as long as wide; ventral ligule subconical or digitiform, 2× as wide as long, 2× as long as neuracicular ligule. Notochaetae: 6 homogomph spinigers and 1 homogomph falciger with blade 7 × as long as wide, distal tooth incurved, fused to blade. Supracicular neurochaetae: 5 homogomph spinigers, 2 heterogomph falcigers with blades 8 × as long as wide, distal tooth incurved, fused to blade (Fig. 8I) and 1 thick heterogomph falciger with blade 2.7× as long as wide; subacicular neurochaetae: 1 heterogomph spiniger and 6 heterogomph falcigers with blades 4.2× as long as wide, distal tooth incurved, fused to blade (Fig. 8J).

POSTERIOR PARAPODIA (Fig. 8E). In fair condition, dorsal and ventral cirri missing. Dorsal ligule subconical, tapering, widened, 1.7× as wide as long, with massive dark glands, as long as median ligule; median ligule subconical to digitiform, 4 × as long as neuracicular ligule, with massive dark glands. Neuracicular ligule subconical, as long as wide; ventral ligule digitiform, 3× as long as neuracicular ligule, with massive dark glands. Notochaetae: 2 homogomph spinigers and 1 homogomph falciger with blade 7.1 × as long as wide, similar to those of median parapodia (Fig. 8F). Supracicular neurochaetae: 1 homogomph spiniger, 2 heterogomph falcigers with blades 5× as long as wide and 1 thick heterogomph falciger with blade 2.9 × as long as wide, distal tooth incurved, fused to blade (Fig. 8K); subacicular neurochaetae: 2 heterogomph falcigers with blades 5.8× as long as wide, distal tooth incurved, fused to blade, similar to those of median parapodia.

POSTERIOR REGION. Missing.

Atokes

BODY. Atoke specimen (UMML 22.1174) complete, in good condition, 30 mm long, 2 mm wide, 62 chaetigers. Another specimen (ECOSUR P3104) with dark brown pigmentation throughout body; pigmentation present on prostomium and palpophores, tentacular belt fully pigmented (Fig. 8A–B). Dorsal pigmentation pattern as one anterior, transverse band on each segment along anterior body, breaking into several rectangular patches towards posterior chaetigers. Glands present in notopodial and ventral ligules throughout body (Fig. 9A–B, H–K).

PROSTOMIUM. Pyriform, longer than wide, dorsal groove present. Eyes rounded, subequal, in trapezoidal arrangement (Fig. 9A, C). Antennae cirriform, as long as prostomium, with a small gap between them (Fig. 9C). Palpophores globose, 1.5× as long as wide, palpostyles rounded.

TENTACULAR BELT. 1.5× as long as first chaetiger, anterior margin slightly covering posterior eyes. Tentacular cirri smooth, longest ones reach chaetiger 4 (Fig. 9A, C).

PHARYNX. Dissected; jaws brown, with 10 teeth. Paragnath formula: I: 1; II: 18–20 in arc; III: 15 in rectangle; IV: 14–16 in arc; V: 0; VI: 8–10 in oval; VII–VIII: 5 in a single band.

PATTERN OF PARAPODIAL LIGULES. Anterior chaetigers with dorsal ligules subconical, blunt, median ligules rounded; median and posterior chaetigers with ligules subconical, becoming wider toward posterior chaetigers; ligules with contorted glandular tubules.

CHAETIGERS 1–2 (Fig. 9H). With neuraciculae only, with both noto- and neuraciculae thereafter. Dorsal cirrus basally inserted, 1.2× as long as dorsal ligules; dorsal and ventral ligules subconical, blunt, subequal, 1.5 × as wide as long, several times longer and wider than neuracicular ligule. Neuracicular ligule subconical. Ventral cirrus as long as ventral ligule.

ANTERIOR PARAPODIA (Fig. 9I). With dorsal cirrus 2 × as long as dorsal ligule; dorsal ligule subconical, blunt, 2× as wide as long, as long as median one; median ligule rounded, as long as wide, 1.2× as long as neuracicular one. Neuracicular ligule rounded, as long as wide, as long a ventral ligule; postchaetal lobe subconical, as long as neuracicular one; ventral ligule digitiform to rounded, 2 × as wide as long. Ventral cirrus as long as ventral ligule. Notochaetae 6–7 homogomph spinigers. Supracicular neurochaetae: 7–9 homogomph spinigers and 2–3 heterogomph falcigers with blades 7× as long as wide, distal tooth incurved, fused to blade; subacicular neurochaetae 3–4 heterogomph spinigers, 3–4 heterogomph falcigers with blades 8× as long as wide and 1–2 heterogomph falcigers with blades 4× as long as wide, distal tooth incurved, fused to blade.

MEDIAN (Fig. 9J) AND POSTERIOR (Fig. 9K) PARAPODIA. With dorsal cirri 1.2–1.5× as long as dorsal ligule. Dorsal ligule subconical, tapering, widened, 1.2–1.5 × as wide as long, with massive dark glands, slightly longer than median ligule; median ligule subconical, tapering, 3–4 × as long as neuracicular

ligule. Neuracicular ligule subconical, blunt; ventral ligule digitiform, 2 × as long as neuracicular ligule. Ventral cirrus slightly shorter than ventral ligule in median parapodia, becoming slightly longer than ventral ligule toward posterior parapodia. Notochaetae: 2–4 homogomph spinigers and 1 homogomph falciger with blade 7 × as long as wide (Fig. 9E). Supracicular neurochaetae: 2–6 homogomph spinigers, 1–2 heterogomph falcigers with blades 5 × as long as wide and 1 thick heterogomph falciger (Fig. 9F) with blade 3× as long as wide, distal tooth incurved, fused to blade; subacicular neurochaetae: 2–3 heterogomph falcigers with blades 5× as long as wide, distal tooth incurved, fused to blade (Fig. 9G).

POSTERIOR REGION. With pygidium tripartite; anal cirri subulate, as long as last 7 chaetigers (Fig. 9D).

Remarks

Nereis (Nereis) marginata is a neglected Caribbean species; it was originally described based on a single specimen with about 90 chaetigers from St John, U.S. Virgin Islands (formerly St Jean).

The original description is succinct and has no illustrations; perhaps because of this, Hartman (1959) regarded N. marginata as indeterminable. The type material of N. (Nereis) marginata (NHMD 109266) was examined. The holotype consists in a single specimen with the pharynx previously removed. The parapodia have black spots on the distal part of the ligules throughout body. Additional specimens from the Caribbean Sea were examined and match the type material.

Nereis marginata resembles N. rava, from the Mediterranean Sea (following Gravina et al. 2015). These two species have posterior eyes partially covered by the tentacular belt’s anterior margin and short tentacular cirri reaching chaetigers 2–4. Their main differences are in pigmentation pattern and in the relative size of the notopodial ligules on posterior chaetigers. In N. marginata the dorsum has transverse irregular bands, its dorsal ligules are 2–3 × as wide as median ones and the ventral ligules surpass neuracicular ligules, whereas in N. rava the dorsum has two transverse bands, its dorsal and median ligules are of similar width and ventral ligules reach neuracicular ligules in length.

On the other hand, N. marginata also resembles N. riisei in pharyngeal formula and both parapodial and chaetal morphology, but they can be separated by using several features of the anterior end, parapodia and chaetae. In N. marginata, the posterior eyes are partially covered by the tentacular belt, whereas in N. riisei they are completely exposed; in N. marginata, the dorsal ligules are wider than long throughout body and become markedly wider toward posterior chaetigers, whereas in N. riisei they are of subequal length and width, becoming slightly wider toward posterior chaetigers; in N. marginata, median ligules in anterior chaetigers are much wider than neuroacicular ligules, whereas in N. riisei they are of similar width; in N. marginata, the ventral cirri become longer than ventral ligules toward posterior chaetigers, whereas in N. riisei they are shorter than the ventral ligules throughout the body; N marginata has neuropodial heterogomph falcigers with blades of different sizes in supra- and infracicular neuropodial fascicles, whereas in N. riisei they are of similar size. These differences are consistent within the material examined, so Nereis marginata is here regarded as a valid species.

Distribution

Caribbean Sea, in mixed bottoms up to 80 m depth.