Nereis splendida Grube, 1840

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 : 10-20

Nereis splendida Grube, 1840

Figs 1 , 3–6

Nereis splendida Grube, 1840: 75–76 .

Nereis (Nereilepas) parallelogramma Claparède, 1868: 477–478 , pl. 9 fig. 7, pl. 10 fig. 2.

Nereis splendida – Grube 1874: 70 (synonymy). — Núñez 2004: 375–378, fig. 139. — Alós et al. 2004: 513 (synonymy).

Nereis falsa – Fauvel 1913: 63; 1916: 81–84, pl. 5 figs 1–11 (synonymy, partim); 1923: 337–338, fig. 129e–m; 1950: 353. — Fauvel & Rullier 1959: 517–518. — Rullier & Amoureux 1969: 120. — Gravina et al. 2015: 155, fig. 9 (synonymy) (non de Quatrefages, 1866).

Diagnosis

Nereis with tentacular belt 2× as long as first chaetiger; tentacular cirri reaching chaetiger 4–5. Jaws with 5–6 denticles; paragnaths arranged as follows: I: 2 in tandem; II: 21–22 in two rows; III: 28–40; IV: 35–36; V: 0; VI: 4–5; VII–VIII: 66 in 2 bands. Posterior parapodia with ventral ligule longer than neuracicular ligules and ventral cirri.

Material examined

Neotype ITALY • ♂ epitoke; Naples, Rade de Santa Lucia ; Campagnes de M. Albert 1 er de Monaco, 1885–1910, stn 311; electric light; 4 Aug. 1893; MNHN 423-311 .

Other material

Atokes

MEDITERRANEAN SEA • 1 spec. (22 mm long, 2 mm wide, 71 chaetigers; anterior and median parapodial ligules blunt, digitate, posterior ones tapered; pharynx fully exposed, area VI: 4+ 5 in diamond); MNHN A83b • 4 specs (without posterior regions, 16–31 mm long, 1.1–3.0 mm wide, 48– 57 chaetigers; longest tentacular cirri reach chaetigers 3–4; one medium-sized specimen with pharynx fully exposed); Chaine de l’Eider , Monaco, port; Campagnes de M. Albert 1 er de Monaco, 1885–1910, stn 531; 13 Sep. 1905; MNHN 423-531 • 1 spec. (30 mm long, 2 mm wide, 82 chaetigers; pharynx not exposed; longest tentacular cirri reach chaetiger 3; anal cirri as long as last 7–8 chaetigers); same collection data as for preceding; MNHN 495-1 .

Epitokes

ALGERIA • 2 ♂♂ (10–17 mm long, 2–3 mm wide, 50–79 chaetigers), 1 ♀ (22 mm long, 2 mm wide, 78 chaetigers); Algiers, entrance to port; 36°46′00″ N, 03°04′00″ E; light trap; 20 Aug. 1924; MNHN A83 (lot also includes 1 smaller ♂ epitoke of another species) .

MOROCCO • 3 ♂♂ (22.0– 24.5 mm long, 3.0 mm wide, 76–78 chaetigers; longest tentacular cirri reaching chaetigers 5–7; jaws with 7 accessory denticles); Rade de El Yadida (formerly Mazaghan); 33°14′ N, 08°30′ W; Campagnes de M. Albert 1 er de Monaco, 1885–1910, stn 779; electric light; 23 Jun. 1897; MNHN 423-779a • 5 ♂♂ (16.0– 20.5 mm long, 2.0– 2.5 mm wide, 74–78 chaetigers; longest tentacular cirri reaching chaetigers 5–7; jaws with 6–7 accessory denticles); same collection data as for preceding; MNHN 423-779b .

SENEGAL • 2 ♀♀ (pre-epitokes, dehydrated, one complete, one anterior fragment; complete one 31 mm long, 3 mm wide, 83 chaetigers; longest tentacular cirri reach chaetiger 5–6; chaetiger 47 with ventral cirri shorter than ventral ligule; oocytes loose in coelom from chaetiger 2, each about 150 μm in diameter); Dakar; 1947; R. Sourie leg.; MNHN 495-1947a .

Description

Neotype

BODY. Complete, bent laterally, medially collapsed by label, anterior end breaking off at chaetiger 7, pharynx fully exposed. Length 15 mm, width 3 mm, 73 chaetigers. Dorsum brownish along body, wider transverse bands along non- natatory region, with a paler longitudinal tapered band finishing on chaetiger 18 ( Fig. 3A ). Divided into two regions: non-natatory region includes chaetigers 1–18; natatory region with parapodia markedly transformed along chaetigers 19–73.

PROSTOMIUM. As long as wide, dorsal groove present. Eyes black, enlarged, fused laterally, subequal, slightly smaller than ⅓ of prostomial width. Antennae tapered, divergent, ⅓ as long as prostomium, as

long as palpophores. Palpophores massive, expanded laterally, as long as wide, palpostyles rounded, small.

TENTACULAR BELT. 2 × as long as first chaetiger, anterior margin not covering posterior eyes ( Fig. 3A, C ). Tentacular cirri corrugated, longest one reaching chaetiger 8.

PHARYNX. Exposed ( Fig. 3B–C ). Paragnath formula: I: 2, small, in tandem; II: 24–26 in 2–3 oblique rows; III: 38 in oval group; IV: 40–42 in oval groups; V: 0; VI: 4–5 in diamond; VII–VIII: 54, larger, in 2 irregular rows.

PARAPODIA. Not dissected to avoid further damage (see below).

POSTERIOR REGION. Tapered into a blunt cone; pygidium with anus expanded, with 2–3 series of digitate anal cirri (Fig, 3D).

Male epitokes (MNHN A83)

BODY. Complete, 10–17 mm long, 2–3 mm wide, 50–79 chaetigers; specimens slightly damaged, almost colorless, with pharynges fully exposed.

PROSTOMIUM. As long as wide, dorsal groove present. Eyes blackish, enlarged, rounded, fused laterally, enlarged, anterior eyes about as large as ⅓ prostomial width ( Fig. 4A ).Antennae ⅓ as long as prostomium, tapered, longer than palps. Palpophores massive, blunt, subcylindrical, about as wide as long, palpostyles directed ventrally, rounded, small.

TENTACULAR BELT. 2× as long as first chaetiger, anterior margin not covering eyes. Tentacular cirri corrugated, longest ones reaching chaetiger 5 ( Fig. 4A ).

PHARYNX. Everted, jaws amber-colored, tips brownish, each with 7–8 teeth ( Fig. 4A–B ). Paragnath formula: I: 2 in tandem; II: 22–24 in 2–3 oblique rows; III: 36 in oval transverse group; IV: 38–40 in oval groups; V: 0; VI: 4–5 in diamond; VII–VIII: 38–44, not larger than other ones, in 2 irregular rows.

PATTERN OF PARAPODIAL LIGULES. Anterior chaetigers with ligules blunt, longer than wide in first few chaetigers, soon becoming as long as wide; natatory region with ligules tapered, 3–4× as long as wide.

REGIONS. Body divided into two regions: non-natatory region includes chaetigers 1–19, subdividided into two sections: 1) chaetigers 1–8 with dorsal and ventral cirri basally to medially swollen, 2) chaetigers 9–19 with both dorsal and ventral cirri cirriform; and natatory region with markedly transformed parapodia includes chaetigers 20–79 (to end of the body), plus pygidium.

CHAETIGERS 1–2. With neuraiculae only ( Fig. 4C ), with both noto- and neuraciculae thereafter. Dorsal cirrus cattail-like, 3× as thick and almost 2× as long as ventral one, basal swollen section 5× as wide and 4–5× as long as distal narrow section. Dorsal ligule digitiform, shorter than neuracicular ligule. Neuracicular ligule subconical, truncate, as long as ventral ligule; ventral ligule digitiform, slightly longer than dorsal one. Ventral cirrus with basal swollen section 4× as wide and 2× as long as distal narrow section. Supracicular neurochaetae: 3 homogomph spinigers and 2 heterogomph falcigers with blades 5–6 × as long as wide, spinulose, tendon barely developed; subacicular neurochaetae: 5 homogomph spinigers, with blades long or short, and 3 heterogomph falcigers, one with blade longer than the others.

CHAETIGERS 9–19 ( Fig. 4D ). With dorsal cirrus cirriform, full of sperm. Dorsal cirrus slightly longer and wider than ventral ones, basal swollen section 3 × as thick and 2.5× as long as distal narrow section. Dorsal and median ligules digitiform, tapered, barely longer than wide, about as long as neuracicular ligule. Neuracicular ligule subconical, 1.5 × as long as ventral ligule; ventral ligule blunt, 1.5× as long as wide. Ventral cirrus with basal swollen section 2× as wide and as long as distal narrow section. Notochaetae 4 homogomph spinigers. Supracicular neurochaetae: 2 homogomph spinigers and 2 heterogomph falcigers; subacicular neurochaetae: 6 heterogomph falcigers.

ANTERIOR NATATORY PARAPODIA ( Fig. 4E ). With large expanded fan lobes basal to dorsal and ventral cirri, and on median and neuracicular ligules ( Fig. 4E ). Dorsal cirrus wider and longer than ventral cirrus, 2.5× as long as rounded dorsal lamellae, with spherical, centrally open expanded areas. Dorsal ligule digitiform, tapered, 5–6× as long as wide, as long as median ligule; median ligule arrowheadshaped, with lamella on ventral side. Neuracicular ligule digitiform; postchaetal lobe transformed into flabelliform lamella, as long as neuracicular ligule; ventral ligule digitate, about 5× as long as wide, as long as neuracicular ligule, with a small dorsal protuberance near base. Ventral cirrus with upper lamella digitiform, 7–8 × as long as wide, lower lamella flabelliform, about 2 × as long as wide. Noto- and neuropodial natatory chaetae sesquigomph, blades fusiform, 8–10 × as long as wide, one margin finely denticulate, tips tapered, usually eroded.

POSTERIOR NATATORY PARAPODIA ( Fig. 4F ). With slightly reduced modifications; glandular areas better defined in ligules, being smaller than those present in anterior natatory region. Dorsal cirrus slightly longer, as wide as ventral one, 3–4 × as long as digitiform dorsal lamella. Dorsal and median ligules subconical, subequal, tapered; dorsal ligule 1.2× as long as wide; median ligule arrowhead-shaped, with lamella on ventral side. Neuracicular ligule digitiform; postchaetal lobe transformed into flabelliform lamella, as long as neuracicular ligule; ventral ligule digitiform, tapered, about 5–6 × as long as wide, as long as neuracicular ligule. Ventral cirrus slightly longer than upper and lower lamellae; upper lamella digitiform, lower one flabelliform. Noto- and neuropodial natatory chaetae sesquigomph, blades fusiform, 7–9× as long as its widest area, very finely denticulate along one margin.

POSTERIOR REGION. Abruptly tapered ( Fig. 4G ). Pygidium expanded into a rosette with several rows of digitiform papillae-like anal cirri, each 2–4 × as long as wide.

Female epitoke (MNHN A83)

BODY. Complete, 22 mm long, 2 mm wide, 78 chaetigers, slightly damaged, almost colorless, with pharynx fully exposed.

PROSTOMIUM. As long as wide, dorsal groove present. Eyes blackish, enlarged, rounded, anterior ones about as large as ⅓ prostomial width ( Fig. 5A ). Antennae ⅓ as long as prostomium, slightly longer than palps. Palpophores massive, blunt, subconical, slightly wider than long, palpostyles rounded, small.

TENTACULAR BELT. 2× as long as first chaetiger, anterior margin not covering posterior eyes. Tentacular cirri corrugated, longest ones reaching chaetiger 8 ( Fig. 5A ).

PHARYNX. Everted, jaws amber-colored, tips brownish, each with 5–6 teeth ( Fig. 5A–B ). Paragnath formula: I: 2 in tandem; II: 10–12 in two oblique rows; III: 25 in oval transverse group; IV: 34–36 in oval oblique groups; V: 0; VI: 4 in diamond; VII–VIII: 44, larger, in 2 irregular rows.

PATTERN OF PARAPODIAL LIGULES. Anterior chaetigers with ligules blunt, as long as wide, or slightly longer than wide; median and posterior chaetigers with ligules tapered or digitate, about 2 × as long as wide, or longer.

REGIONS. Body separated into three regions: non-natatory region includes chaetigers 1–25 sub-dividided into two sections: 1) chaetigers 1–5 with dorsal and ventral cirri basally to medially swollen, 2) chaetigers 6–25 with both dorsal and ventral cirri cirriform; natatory region with markedly transformed parapodia includes chaetigers 26–65; and caudal region with slightly transformed parapodia includes chaetigers 66–78 (end of the body).

CHAETIGERS 1–2. With neuraciculae only ( Fig. 5D ); with both noto- and neuraciculae thereafter. Dorsal cirrus thicker, slightly longer than ventral cirrus, basal swollen section 4 × as wide and 3× as long as distal narrow section. Neuracicular ligule subconical, slightly shorter than ventral ligule; ventral ligule digitiform, 1.2× as wide as long. Ventral cirrus with basal swollen section 3× as wide and 2 × as long as distal narrow section. Supracicular neurochaetae: 4 homogomph spinigers and 2 heterogomph falcigers with blades 4–5 × as long as wide, spinulose, tendon barely developed; subacicular neurochaetae: 4 heterogomph spinigers and 6 heterogomph falcigers with blades 6–8× as long as wide, spinulose, tendon barely developed.

CHAETIGERS 6–25 ( Fig. 5E ). Full of oocytes, with dorsal cirrus slightly longer and wider than ventral cirrus, 2.5× as long as dorsal ligule. Dorsal and median ligules digitiform, slightly longer than wide, slightly longer than median ligule. Neuracicular ligule subconical, slightly longer than ventral ligule; ventral ligule digitiform, slightly longer than wide. Notochaetae 4 homogomph spinigers. Supracicular neurochaetae: 4 homogomph spinigers and 3 heterogomph falcigers with blades 2–3× as long as wide, spinulose, tendon barely developed; subacicular neurochaetae: 4 heterogomph spinigers and 4 heterogomph falcigers with blades 2–3 × as long as wide, spinulose, tendon barely developed.

NATATORY PARAPODIA ( Fig. 5F ). With large expanded fan lobes on neuracicular ligule and at base of ventral cirri; smaller fans along lower surface of median ligules. Dorsal cirrus barely longer and wider

than ventral cirrus, glandular masses absent. Dorsal ligule subconical, 3× as long as wide, glandular areas barely visible; median ligule arrowhead-shaped, with lamella on ventral side. Neuracicular ligule digitiform, 1.2× as long as postchaetal lobe; postchaetal lobe transformed into flabelliform lamella, ventrally bilobated; ventral ligule digitiform, basally swollen, 3–4 × as long as wide. Ventral cirrus with upper lamella digitiform, 4× as long as wide, lower lamella flabelliform, about 2–3× as long as wide. Noto- and neuropodial natatory chaetae sesquigomph, blades fusiform, 7–9 × as long as wide, one margin very finely denticulate, tips tapered, usually eroded.

CAUDAL REGION ( Fig. 5G ). With reduced parapodial transformation; with a small fan lobe over superior surface of neuracicular ligules and glandular areas better developed in parapodial ligules, tubular glands homogeneous, slightly rugose, projected along parapodial ligules and forming a mass basal to dorsal cirri. Dorsal cirrus slightly shorter and wider than ventral cirrus, slightly longer than dorsal ligule. Dorsal ligule digitiform, 2–3 × as long as wide; median ligule subconical, blunt, slightly longer than dorsal ligule, 1.2× as long as neuracicular ligule. Neuracicular ligule subconical, about 4× as wide as long; postchaetal lobe transformed into rounded lamella, 0.3× as long as neuracicular ligule; ventral ligule digitate, 4× as long as wide, 1.5 × as long as ventral cirrus. Ventral cirrus with upper and lower lamellae digitiform, 2× as long as wide. Noto- and neuropodial natatory chaetae sesquigomph; blades fusiform, 7–9× as long as wide, very finely denticulate along one margin.

POSTERIOR END. Tapered ( Fig. 5C ). Pygidium conical, blunt, without rosette of papillae, anal cirri missing.

OOCYTES. Round, granulose, with yolk droplets, each oocyte about 160μm in diameter.

Atokes

BODY. Largest specimen (MNHN 423-531), without posterior region, 31 mm long, 3.0 mm wide, 57 chaetigers. Another long specimen (MNHN 495-1) complete, 30 mm long, 2 mm wide, 82 chaetigers. Body subcylindrical; dorsum brownish, with a paler middorsal blood vessel, integument darker along anterior chaetigers with some darker oblique lines ( Fig. 6A ), sometimes blackish ( Fig. 6G ); other specimens paler. Parapodia paler.

PROSTOMIUM. 2 × as long as wide, dorsal groove present. Eyes blackish, of similar size, anterior eyes oval, directed anterolaterally, about ⅛ of prostomial width, slightly more separated than posterior eyes ( Fig. 6B ). Antennae half as long as prostomium, without gap between them, tips reaching palpostyle tips. Palpophores almost 2× as long as wide; palpostyles slightly longer than wide ( Fig. 6B ) or rounded ( Fig. 6G ).

TENTACULAR BELT. 1.5 × as long as first chaetiger; anterior margin straight, not covering posterior eyes. Tentacular cirri smooth to regularly contracted ( Fig. 6B ), partially dehydrated, without tips ( Fig. 6G ), longest ones reaching chaetigers 3–4.

PHARYNX. Not everted, observed by previous dissections. Jaws with 6 denticles (5 in smallest specimen, MNHN 423-531). Paragnath formula: I: 2 in tandem; II: 21–22 (24–26 in smallest specimen) in 2–3 rows; III: 40 (28 in smallest specimen) in oval group; IV: 35–36 (27–28 in smallest specimen) in oval groups; V: 0; VI: 5 (4 in smallest specimen) in diamond; VII–VIII: 2–3 rows of 66 large paragnaths (same in smallest specimen).

PATTERN OF PARAPODIAL LIGULES.Anterior and median chaetigers with ligules blunt, about 2 × as long as wide, becoming blunt subconical to digitiform, about 2.5 × as long as wide medially, posterior chaetigers with ligules subconical, blunt; ventral ligules progressively longer than neuracicular ligule in posterior chaetigers.

CHAETIGERS 1–2. With neuraciculae only ( Fig. 6C ); with both noto- and neuraciculae thereafter. Dorsal cirrus slightly longer, as wide as ventral cirrus, 2× as long as parapodial ligules. Dorsal ligule digitiform, 2 × as long as neuracicular ligule. Neuracicular ligule subconical, longer than wide; ventral ligule digitiform, 1.2× as long as neuracicular ligule. Supracicular neurochaetae: 7 homogomph spinigers and 4 heterogomph falcigers with blades 5–6 × as long as wide, spinulose, tip incurved; subacicular neurochaetae: 7 heterogomph spinigers and 10 heterogomph falcigers with blades 6–7 × as long as wide, spinulose, tip incurved.

MEDIAN PARAPODIA ( FIG. 6D ). With dorsal cirrus longer than dorsal ligule, slightly longer than ventral cirrus. Dorsal and median ligules subequal, as long as wide, as long as neuracicular ligule, subconical to rounded, glandular areas unpigmented, extended along ligular bases. Neuracicular ligule subconical, as long as wide, subequal to ventral ligule; ventral ligule digitiform, 1.3× as long as ventral cirrus. Notochaetae 12 homogomph spinigers. Supracicular neurochaetae: 6 homogomph spinigers and 3 heterogomph falcigers with blades 3 × as long as wide, spinulose, tip incurved, tendon barely visible, in smaller specimen distinct ( Fig. 6I ); subacicular neurochaetae: 6 heterogomph spinigers, blades decreasing in size ventrally, and 6 heterogomph falcigers with blades 2–3 × as long as wide, spinulose, tip incurved, tendon visible.

POSTERIOR CHAETIGERS ( Fig. 6E ). With dorsal and ventral cirri 6–8× as long as wide, dorsal cirrus longer than dorsal ligule. Dorsal and median ligules subconical, blunt, slightly longer than wide, 1.2 × as long as neuracicular ligule; glandular areas unpigmented, extended along ligular bases. Neuracicular ligule subconical, blunt, as long as ventral ligule; ventral ligule digitiform, slightly longer than wide, 1.2× as long as ventral cirrus. Notochaetae: 6 homogomph spinigers and 1 homogomph falciger with blade 4× as long as wide, spinulose, tip incurved, tendon visible. Supracicular neurochaetae: 7 homogomph spinigers and 3 heterogomph falcigers with blades 2× as long as wide, spinulose, tip incurved, tendon visible; subacicular neurochaetae: 5 homogomph spinigers and 3 heterogomph falcigers with blades 2× as long as wide, spinulose, tip incurved, tendon visible.

SUBTERMINAL CHAETIGERS ( Fig. 6F, H ). With dorsal cirrus 2–4 × as long as dorsal ligule, about 2× as long as ventral cirrus. Dorsal and median ligules digitiform, of similar size, 2 × as long as wide, 2× as long as neuracicular ligule. Neuracicular ligule subconical, slightly longer than wide, almost blunt; ventral ligule digitiform, 2× as long as wide, 2× as long as neuracicular ligule. Notochaetae 7 homogomph spinigers (blades mostly lost), falcigers absent. Supracicular neurochaetae: 4 homogomph spinigers and 2 heterogomph falcigers (blades lost); subacicular neurochaetae: 2 heterogomph spinigers and 7 heterogomph falcigers with blades 2× as long as wide, spinulose, tip incurved, tendon visible.

POSTERIOR REGION. Tapered into a blunt cone ( Fig. 6H ). Pygidium with anus terminal, anal cirri as long as last 7–8 chaetigers (MNHN 495-1).

Remarks

Fauvel (1916: 81) used the name N. falsa for some Mediterranean nereidids and he included as junior synonyms of N. falsa two species described from Naples by Claparède (1868): N. parallelogramma and N perivisceralis ; he also included N. lucipeta Ehlers, 1908 from South Africa. In a subsequent publication, Fauvel (1916: 81) added N. splendida Grube, 1840 as a synonym, another Mediterranean species, as well as a record by Ehlers (1913: 496) for the Cape Peninsula, South Africa. By expanding this synonymy, Fauvel’s conclusions generated the “ N. falsa species group,” which he would define later ( Fauvel 1923: 337). The list of synonyms includes, after Fauvel, N. parallelogramma Claparède, 1868 , N. perivisceralis Claparède, 1868 , Lycoris pulsatoria Rathke, 1843 and N. lucipeta Ehlers, 1908 . This group contains species of Nereis with pharyngeal area V without paragnaths and areas VII–VIII with a single row or 2–3 rows of paragnaths, anterior parapodia with two blunt notopodial ligules, notopodial homogomph falcigers in posterior chaetigers, with blades sinulose, sometimes with a distal ligament or tendon ( Fauvel 1923). Two other species, N. callaona and N. victoriana Augener, 1918 , were regarded as similar to N. falsa by Salazar-Vallejo & Jiménez-Cueto (1997: 374), and Reish (1954: 104) regarded N. pseudonereis and N. robusta Kinberg, 1866 as junior synonyms of N. callaona .

This progression of synonymies based on generally similar specimens of different species, without paying attention to some features of the pharynx, was incorrect, especially because N. falsa was based on L. pulsatoria ? from the Black Sea, which does not match these features. Furthermore, some aspects of the taxonomic history of Hediste diversicolor deserve mention, as it is also complex and not fully resolved. For example, there are no type specimens and there was no indication of the type locality. Furthermore, specimens identified as H. diversicolor from the Baltic Sea, which could be the type locality, include at least two different species, and this has complicated resolving what we should regard as this biological species ( Oug et al. 2014). Some names are available for the regional forms, in case there is more than one, taking into account that Malmgren (1867: 48–49) proposed Hediste to include N. diversicolor , listing N. sarsi Rathke, 1843 , described from Molde, Norway, and N. depressa Frey & Leuckart, 1847 , described from Helgoland, Germany, as junior synonyms. Ehlers (1868: 554) added N. brevimanus Johnston, 1840 , described from Ireland, to the list of synonyms. Black Sea population haplotypes differ from those present in nearby areas ( Vasileiadou et al. 2016); if this difference promotes regarding Black Sea specimens as belonging to a different species, N. falsa de Quatrefages, 1866 would be available for them.

It has been indicated that Nereis splendida cannot be used as a senior synonym for N. falsa (Salazar- Vallejo et al. 2017), because it was preoccupied by Nereis splendida de Blainville, 1825 . Because this is a junior homonym, its name should be replaced ( ICZN 1999, arts 52.2, 57.2), and the next available name should be used instead. However, contrary to previous conclusions, there is an alterative for retaining N. splendida Grube, 1840 , and this refers to the fact that the two species involved do not belong in the same genus ( ICZN 1999, art. 59.2). Nereis splendida de Blainville, 1825 refers to a nephtyid polychaete, which would be a junior synonym of Nephtys hombergi Savigny in Lamarck, 1818 according to Audouin & Milne-Edwards (1833: 257) and de Quatrefages (1866a: 434). Consequently, “the junior name is not to be rejected, even if one species-group name was originally proposed in the current genus of the other” ( ICZN 1999, art. 59.2). Alós et al. (2004: 513) did not indicate their reasons for retaining N. splendida Grube, 1840 , but the above article provides the explanation for it.

Some additional details must be understood. First, the composition of the type material. Augener (1918: 186) noted that what was then regarded as the type material of N. splendida Grube, 1840 actually contained three specimens, two of them belonging to Ceratonereis Kinberg, 1865 , and the originally described specimen of N. falsa .

Second, the type material is lost. Birger Neuhaus (ZMB, 2019 in email) indicated “We had unspecified type material of Nereis splendida , catalogue number ZMB ‘Vermes’ 5160; the material was lost at some time. I checked our loan records and found that Augener received this lot on loan to Hamburg around 19.II.1914 from my predecessor Anton Collin, and returned the specimens on 11.VIII.1921. He does not seem to have had the specimens on loan a second time.”

The next available name is N. splendida Grube, 1840 . This name could be used for Mediterranean records of what has been regarded as N. falsa . As indicated above, N. falsa would be available for the Black Sea populations currently regarded as Hediste diversicolor , once significant differences are found and its independent specific status is confirmed. However, Claparède left no type material because he emphasized that ( Claparède 1867: 12 [341 in translation]) “the Annelida can only be well studied at the seaside and by means of living individuals.” Because there is no type material, and especially because the species-group name is in conflict, the designation of a neotype is necessary to define the nominal taxon ( ICZN 1999, art. 75.1). These are the qualifying conditions:

- a neotype of Nereis splendida Grube, 1840 is proposed to clarify the taxonomic status of the species ( ICZN 1999, art. 75.3.1)

- the above description, the key below, and the publication by Gravina et al. (2015, as Nereis falsa ) characterize the species and its differences from similar species in the area or from elsewhere ( ICZN 1999, art. 75.3.2)

- the description above matches the original description and the labeling ensures the recognition of the neotype ( ICZN 1999, art. 75.3.3)

- as indicated above, the type material was lost ( ICZN 1999, art. 75.3.4)

- the neotype is a mature male specimen with some modifications for swimming and swarming. Despite the modifications of cephalic appendages and parapodia, the pharynx armature is not modified ( Fauvel 1916; Pamungkas & Glasby 2015), and the neotype matches the original description. Because no other topotype specimen was available, this different life stage is code compliant ( ICZN 1999, art. 75.3.5)

- the neotype was collected in Naples harbor, and Grube (1840: 2) indicated that most of his specimens, if no locality was given, as is the case for N. splendida , were collected in the Gulf of Naples, and the neotype was collected from the same area ( ICZN 1999, art. 75.3.6)

- the neotype has been deposited in the Muséum national d’histoire naturelle, Paris, a recognized scientific institution ( ICZN 1999, art. 75.3.7)

Most specimens that have been preserved for about 100 years risk having the blades of compound falcigers detach, and this is why additional specimens must be studied to reveal the specific morphology of the homogomph falcigers in median or posterior chaetigers. It seems that the blades in median chaetigers have tips better defined and more acute than those present along more posterior chaetigers. Observations of the inner margin denticulation are also difficult because it can be eroded, and we think this feature is also better defined along median chaetigers.

“ Nereis falsa ” resembles N. pelagica Linnaeus, 1758 , the type species of the genus ( Fauvel 1923: 335–336), in pharyngeal ornamentation and parapodial development; their main differences are in the size and dentition of the homogomph falciger blades. In “ N. falsa ” the blades of falcigers are longer (3× as long as wide), the distal tooth is incurved and they have denticulate cutting edges, whereas in N. pelagica the blades are shorter (2.0–2.5 × as long as wide), without a distal tooth and the cutting edges are smooth to barely rugose. On the other hand, Gravina et al. (2015: 162, key) indicated that “ N. falsa ” is more similar to N. rava Ehlers, 1864 , because both have similar parapodial development in posterior chaetigers, without expanded dorsal ligules, and because the homogomph falciger blades are denticulate. These two species differ because of some fine details in the blades of homogomph falcigers. In N. rava , these blades are medially expanded, and there is a thicker distal tooth, without a ligament, whereas in “ N. falsa ” the blades are tapered, and the distal tooth is incurved, with a ligament or tendon. Another relevant difference is that in N. rava there is a single transverse row of paragnaths in areas VII–VIII, whereas there are 2–3 rows in “ N. falsa ”. In the latter species, most accounts indicate that there can be 3 or 4–5 paragnaths in area VI in the same population ( Fauvel 1923; Gravina et al. 2015), and it would be interesting to evaluate whether these differences are linked with some other morphological features.

It must be emphasized that according to Hartman (1959), N. pelagica includes 18 junior synonyms (and some subspecies) described from the Atlantic; the Northwestern Pacific records ( Imajima 1972) differ from the Northeastern Atlantic forms, as illustrated by Chambers & Garwood (1992: 38), in cephalic appendages, as well as parapodial and chaetal features, including in epitokes. Some of the junior synonyms have also been confused with “ N. falsa ” due to the pigmented glandular parapodial ligules.

As indicated below, N. splendida r esembles “ N. falsa ” recorded for the Caribbean Sea ( Liñero-Arana & Reyes-Vásquez 1979) in having anterior chaetigers with digitate notopodial ligules, ventral ligules longer than neuracicular ligules in median and posterior chaetigers, and pharyngeal areas VII–VIII with 2–3 transverse rows of paragnaths. Their main differences are in prostomial shape and pharyngeal paragnath numbers in area II. In N. splendida the anterior prostomial lobe is 2× as long as wide, and area II has about 22 paragnaths, whereas in the Caribbean specimens the anterior prostomial lobe is wider than long, and area II has about 30 paragnaths.

Distribution

Mediterranean Sea and adjacent localities in the Northeastern Atlantic, in shallow water. The record by Rullier & Amoureux (1969: 120) cannot be confirmed because their specimens could not be located.

Figures

Fig. 1. Nereis splendida Grube, 1840, non-type juvenile (MNHN 423-531), after methyl green staining. A. Chaetiger 9, right parapodium, anterior view. B. Chaetiger 25, right parapodium, anterior view. C. Chaetiger 46, right parapodium, anterior view.

Fig. 3. Nereis splendida Grube, 1840, neotype (MNHN 423-311), male epitoke. A. Anterior region, dorsal view, depressed by cover slip. B. Anterior end, dorsal view. C. Anterior end, ventral view. D. Posterior region, dorsal view.

Fig. 4. Nereis splendida Grube, 1840, non-type, largest male epitoke (MNHN A83), after Shirlastain-A staining. A. Anterior region, dorsal view.B. Anterior end, ventral view.C. Chaetiger 2, right parapodium, anterior view. D. Chaetiger 15, right parapodium, anterior view. E. Chaetiger 30, right parapodium, anterior view. F. Chaetiger 74, right parapodium, posterior view (chaetae omitted). G. Posterior region, dorsal view.

Fig. 5. Nereis splendida Grube, 1840, non-type, female epitoke (MNHN A83), after Shirlastain-A staining. A. Anterior region, dorsal view. B. Anterior end, ventral view. C. Posterior region, dorsal view. D. Chaetiger 2, right parapodium, anterior view. E. Chaetiger 15, right parapodium, anterior view. F. Chaetiger 30, right parapodium, anterior view. G. Chaetiger 73, right parapodium, anterior view (chaetae omitted).

Fig. 6. Nereis splendida Grube, 1840, non-type, atokous specimens. A–F. MNHN 423-531. A. Anterior region, dorsal view. B. Anterior end, dorsal view. C. Chaetiger 2, right parapodium, anterior view. D. Chaetiger 15, right parapodium, anterior view. E. Chaetiger 30, right parapodium, anterior view. F. Chaetiger 55, right parapodium, anterior view (inset: homogomph falciger tip). G–H. MNHN 495-1. G. Anterior region, dorsal view. H. Posterior region, left lateral view. I. Another specimen (MNHN 423- 531), chaetiger 30, right parapodium, homogomph falciger tip.