Sigalionidae Kinberg, 1856

Aungtonya, Charatsee & Eibye-Jacobsen, Danny, 2016, A New Species of the Genus Ehlersileanira (Polychaeta: Sigalionidae) from the Andaman Sea, Thailand, Species Diversity 21, pp. 111-116 : 111-114

Family Sigalionidae Kinberg, 1856 Ehlersileanira Pettibone, 1970

Type species. Sthenelais incisa Grube, 1877: 519–520 (by original designation).

Diagnosis. Prostomium dorsally fused with tentacular parapodia. Three small antennae, each with ceratophore and short style, all biarticulate; ceratophore of median antenna with lateral auricles and/or ctenidia; lateral antennae fused with dorsal side of tentacular parapodia. Dorsal tentacular crests and inner tentacular lobes absent. Nuchal organs present or absent. Inner and outer palpal sheaths present. Facial tubercle present. Segment 2 with ventral buccal cirri. Segment 3 without dorsal cirri, dorsal tubercles present or absent. Ventral cirri with outer basal knob. Elytral surface smooth; outer lateral margin entire, without papillae and tubecels. Notopodia with well developedposterior upper lobe and anterior lower lobe, anterior upper lobe with circlets of stylodes, and large distal stylode. Ctenidial pads present between notopodium and dorsal tubercle or elytrophore. Notochaetae present as simple, coarsely to finely spinous capillaries. Neuropodia with posterior upper and lower lobes basally covering base of chaetae, anterior upper and lower lobes indistinct. Parapodial stylodes present. Neurochaetae present as compound spinigers with canaliculate blades; upper simple spinous capillaries sometimes present.

Remarks. The characters in bold text in the above diagnosis are particularly important in recognizing members of this genus, although they are not necessarily autopomorphies for the genus. It is the combination of these characters that distinguishes species of Ehlersileanira from other genera.

According to Aungtonya (2003, 2005), auricles, ctenidia, and dorsal tentacular crests are defined. An auricle is an ear-shaped lobe ( Fauchald 1977), whereas a ctenidium is a comb-like structure ( Lawrence 1989). A ctenidium is usu- ally found between elytrophores or between dorsal tubercles and notopodia or on the lateral lips of the mouth in Fimbriosthenelais and Sthenelais ( Pettibone 1971: figs 1b, 15b; Aungtonya 2003: figs 4b, 6d). The appendages on the ceratophore of the median antenna in Ehlersileanira ( Pettibone 1970b: 19, fig. 10b) and Horstileanira ( Pettibone 1970c: 378, fig. 11b) are lateral auricles, not ctenidia ( Aungtonya 2003: fig. 1b, e). The ctenidium on the dorsal surface of segment 1, previously mentioned by Pettibone (1970c, 1971, 1992) in Fimbriosthenelais , Horstileanira , Labiosthenolepis , Sthenelais , and Willeysthenelais , has been renamed the dorsal tentacular crests ( Aungtonya 2003: figs 1d–f, 2f, 3c–d).

Aungtonya (2005) discussed the confusion in the use of the terms ‘neuropodial bracts’ and ‘neuropodial lobes’ in earlier papers. Pettibone referred to neuropodial bracts when describing the lobes in Ehlersileanira (1970b: fig. 11a– c), Euthalenessa (1970a: fig. 2a–c), and Horstileanira (1970c: 378) , as well as in Sthenelais (1971: fig. 2b–d) and Willeysthenelais (1971: fig. 7a–c). Subsequently, she mentioned the lobes covering the base of the neurochaetae in Labiosthenolepis (1992: 615) and Labioleanira (1992: 621) , but she returned to using the term bracts in a paper on Pelogeniinae (1997: fig. 2c–e). This variation in use of terms has created some confusion. The general meaning of “bract” in botany is a modified leaf in whose axil an inflorescence or flower arises, or else a floral leaf or a leaf-like structure ( Lawrence 1989). In the present paper, the term ‘neuropodial lobe’ is used for structures covering the bases of the chaetae, following Aungtonya (2005).

According to Pettibone (1970b), the genus Ehlersileanira lacks dorsal cirri and dorsal tubercles on segment 3, but small tubercles are present in the species reported in this study ( Fig. 1D ).

Figures

Fig. 1. Ehlersileanira andamanensis n. sp. A–B, anterior end, dorsal view, with dorsal tentacular cirri and second parapodium on left removed; C, close-up of ceratophore of median antenna, showing auricles and one ctenidium; D, anterior end, dorsal view, (right elytron of segment 2 removed, and specimen was recoated); E, anterior end, ventral view; F, neuropodium of segment 3, anterior view. SEM micrographs all of PMBC 19633. Scales=1.0mm (A), 200µm (D–E), 100µm (B, F), and 10µm (C). Abbreviations: acl=acicular lobe, au=auricle, buc=buccal cirrus, ct=ctenidium, dtu=dorsal tubercle, ipas=inner palpal sheath, lan=lateral antenna, man=median antenna, opas=outer palpal sheath, pa=palp, st=stylode, vc=ventral cirrus.