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 : 59-61

Key to atokes of the Nereis splendida Grube, 1840 species group

(formerly “ N. falsa ” de Quatrefages, 1866 species group)

1. Prostomium with posterior eyes partially covered by anterior margin of tentacular belt; dorsum usually brownish; pharyngeal areas VII–VIII with a single row of paragnaths ..............................2

– Prostomium with posterior eyes completely exposed....................................................................4

2. Longest tentacular cirri reaching chaetigers 7–8; dorsum with a solid brownish pigmentation along anterior chaetigers, fading in median and posterior ones ......................................................... ................................................................................................. N. mezianei sp. nov. (Gulf of Guinea)

– Longest tentacular cirri reaching chaetigers 2–4...........................................................................3

3. Dorsum with two diffuse transverse brownish bands, anterior ones wider, better defined; dorsal and median ligules of similar width in posterior chaetigers .......................................................... ............................................ N. rava Ehlers, 1868 sensu Gravina et al. 2005 (Mediterranean Sea)

– Dorsum with irregular transverse bands; dorsal ligules 2–3 × as wide as median ones in posterior chaetigers ....................................... N. marginata Grube & Örsted in Grube, 1857 (Caribbean Sea)

4. Pharyngeal areas VII–VIII with 2–3 transverse rows of paragnaths...........................................5

– Pharyngeal areas VII–VIII with a single row of large paragnaths.............................................11

5. Anterior chaetigers with notopodial ligules short, globose, usually as long as wide, round, slightly longer than neuracicular ligules.........................................................................................6

– Anterior chaetigers with notopodial ligules digitate, usually longer than wide.....................9

6. Tentacular cirri long, longest one reaching chaetiger 8; pharyngeal area II with 14–15 paragnaths ................................................. N. occidentalis Hartman, 1945 (North Carolina, USA)

– Tentacular cirri short, longest one reaching chaetiger 3–5..................................................7

7. Jaws with 4 teeth; pharyngeal area II with 11 paragnaths in 2 rows; ventral ligules in median and posterior chaetigers markedly longer than neurochaetal lobes ................................................. .............................................. N. callaona Grube & Kröyer in Grube, 1857 (Southeastern Pacific)

– Jaws with 6–7 teeth.........................................................................................................................8

8. Pharyngeal area II with 28 paragnaths, area III with about 50 paragnaths .................................... ................................................................................................................ N. callaona sensu Augener, 1918 (Western Africa) (size relationships of parapodial ligules to neuracicular ligules unknown)

– Pharyngeal area II with 18–20 paragnaths, area III with 30 paragnaths; ventral ligule markedly longer than neuracicular ligule .............. N. lucipeta Ehlers, 1908 reinstated (Southern Africa)

9. Median and posterior chaetigers with ventral ligules as long as neuracicular ligules; pharyngeal area II with 16 paragnaths, area III with 36 paragnaths ...................................................................... .................................................................................... N. lunulata Ehlers, 1901 stat. nov. (Patagonia)

– Median and posterior chaetigers with ventral ligules slightly to markedly longer than neuracicular ligules.................................................................................................................................10

10. Anterior prostomial lobe 2× as long as wide; pharyngeal area II with about 22 paragnaths ...... ........................................................................... N. splendida Grube, 1840 (Mediterranean Sea)

– Anterior prostomial lobe wider than long; pharyngeal area II with about 30 paragnaths ............. ........................................... N. falsa sensu Liñero-Arana & Reyes-Vásquez 1979 (Caribbean Sea)

11. Tentacular belt pale; median and posterior parapodia with ventral ligules surpassing neuracicular ligules ................................................ N. riisei Grube & Örsted in Grube, 1857 (Grand Caribbean)

– Tentacular belt blackish; median and posterior parapodia with ventral ligules reaching tip of neuracicular ligules .................................................. N. ambigua Treadwell, 1937 (Eastern Pacific)

Remarks

Nereis perivisceralis Claparède, 1868 is not included in the key because it has notopodial homogomph falcigers with blades with 1–2 large basal denticles, instead of a series of spines ( Gravina et al. 2015: 152, fig. 4).

On the other hand, Nereis rava Ehlers, 1868 apparently has three different body patterns in the Mediterranean, especially regarding the anterior end features. The original illustration by Ehlers (1868: pl. 21 fig. 10) was repeated by Fauvel (1923: 340, fig. 131e), and it shows the anterior margin of the tentacular belt as crenulated, not covering the posterior eyes, the anterior eyes are not round, but oval with their longest axis horizontal, and the tentacular cirri are long, reaching about chaetiger 6. Núñez (2004: fig. 138a) illustrated an alternative anterior end pattern: the anterior margin of the tentacular belt is smooth, not covering the posterior eyes, the anterior eyes are round, and the tentacular cirri are short, reaching about chaetiger 2–3, although they were described as reaching chaetiger 8 ( Núñez 2004: 373). The third pattern was illustrated by Gravina et al. (2015: 158, fig. 8e): they show the anterior margin of the tentacular belt as smooth, partially covering the posterior eyes, the anterior eyes are round, and the tentacular cirri are very short, barely reaching chaetiger 2. These differences might be explained by the use of different fixatives, ethanol by Ehlers, formaline by the others, but in the key above we follow the characterization of Gravina et al. (2015) for this Mediterranean species.

Key to male epitokes of the Nereis splendida Grube, 1840 species group

(formerly “ N. falsa ” de Quatrefages, 1866 species group)

1. Non-natatory region with 27 chaetigers; palpophores not expanded laterally beyond prostomial lateral margins, narrower than prostomium ...... N. splendida Grube, 1840 (Mediterranean Sea)

– Non-natatory region with 20 chaetigers; palpophores expanded laterally beyond prostomial lateral margins, about as wide as ⅔ of prostomial width ............ N. lucipeta Ehlers, 1908 ( South Africa)