Lysippe Malmgren, 1866

Jirkov, Igor A., 2016, Lysippe nikiti sp. nov. (Polychaeta, Terebellomorpha) from the deep Pacific and Indian Oceans with an amendment to the generic diagnosis of Lysippe, Zootaxa 4117 (1), pp. 125-134 : 126

Lysippe Malmgren, 1866 , emended

= Lysippides Hessle, 1917 ; Paralysippe Williams, 1987 ; Pseudampharete Hilbig, 2000 ; Samytha Malmgren, 1866 Type species: Lysippe labiata Malmgren, 1866 .

Diagnosis. Prostomium of Ampharete - type: subdivided by a U-shaped groove; median lobe anteriorly rounded. Two large nuchal organs in posterior corners of median lobe (may be completely withdrawn and invisible). Lower lip enlarged, longitudinally grooved. Two pairs of nephridial pores/papillae dorsally from the notopodia of segments IV and V; no median nephridial papillae behind branchiae. Neuropodia of two types, their uncini generally similar. Modified notopodia, dorsal ridges and enlarged neuropodia absent.

Remarks. Lysippe always has 14 uncinigers with neuropodia in the form of tori (uncini are situated in a furrow), while the number of segments with notopodia may be 12–14. In other genera with a varying number of thoracic segments ( Ampharete , Amage , and Sosane ), the number of segments with tori varies accordingly.

Paleae may be poorly developed or absent (as in the new species) but, in my opinion, this character should not be included in the generic diagnosis ( Jirkov 2011).

Nephridiopores absent dorsally behind the branchiae, contrary to Ampharete and Anobothrus , which have a pair of nephridial papillae, usually clearly visible, between or just after the middle branchiae. Instead, two pairs of nephridial pores are present much further back and laterally ( Fig. 1 A, arrowed). This is a good taxonomic character; unfortunately the papillae are usually barely visible.

The segmental origin of branchiae is slightly different between Lysippe and other species rich genera ( Fig. 2 ); for example, the branchiae that originate on the 5th segment (if present) are: the innermost pair in Amage , the second pair from the innermost in Ampharete and Anobothrus , the third pair from the innermost in Lysippe and the outermost pair in Sosane . The terminology used to count ampharetid segments differs from author to author. The paleal segment may be counted as the 1st (Noguera et al. 2010), 2nd ( Orrhage 2001; Jirkov 2013; Imajima et al. 2012) or 3rd ( Malmgren 1866; Fauvel 1927; Hilbig 2000); it is clearly not the 1st but whether it is the 2nd or 3rd requires confirmation. It is here counted as the 2nd segment.

There is some doubt about origin of ampharetid buccal tentacles (see Noguera et al. 2010). Amongst the L. labiata specimens examined here, some have everted tentacles ( Fig. 3 ); their placement is very similar to that of terebellids and provides indication of their homology and prostomial origin. Вuccal tentacles of ampharetids probably differ from terebellids mainly in the position of attachment of their buccal tentacles.

Figures

FIGURE 1. Lysippe labiata and L. sexcirrata. L. labiata A, B — anterior of worms with withdrawn and everted nuchal organs; C — posterior end left view; D – E — pygidia. Specimens from R / V Maslov cruise 10 station 49 69 ° 29 ’ N 56 ° 00 ’ E depth 38 m, bottom temperature + 1,19 ° C. F — pygidium of L. sexcirrata R / V Sevastopol cruise 5 station 1157 64 ° 56 ’ N 24 ° 25 ’ W depth 155 m, bottom temperature + 8,17 ° C. no — nuchal organs; np — nephridiopores.

FIGURE 2. Position of branchiae of 5 th segment (filled grey) in different ampharetid genera (after Jirkov 2001).

FIGURE 3. Lysippe labiata with everted buccal tentacles.