Syllis hampirmenyatu, Martínez & Martín, 2020

Martínez, María José & Martín, Guillermo San, 2020, Syllidae (Annelida) from East Timor and the Philippines (Pacific Ocean), with the description of three new species of Syllis Savigny in Lamarck, 1818, Zootaxa 4834 (2), pp. 231-263 : 243-246

Syllis hampirmenyatu n. sp.

Figures 5 , 6

LSID: urn:lsid:zoobank.org:act:A335743F-82B8-4CF2-B040-7E2A26E9288B

Material examined. EAST TIMOR. East of Atauro Island , 08°13’48”S 125°36’56”E, outer reef, coral reef slope, dead coral rubble, 16 m depth, 20 Sep 2012, coll. A. Murray & P.A. Hutchings, holotype ( AM W.53024) and 3 paratypes ( AM W.45645), one of them used for SEM .

Description. Holotype and one paratype complete specimens, other two paratypes incomplete. Holotype, largest complete specimen, 11 mm long, 0.5 mm wide, with 84 chaetigers. Body elongated, thin, somewhat filiform ( Figs 5 A–C, 6A), without colour pattern. Prostomium oval, with four red eyes in trapezoidal arrangement ( Fig. 5A ); eyespots not seen. Palps robust, elongated, somewhat longer than prostomium ( Figs 5A , 6B ). Median antenna arising from middle of prostomium, between posterior eyes, approximately twice as long as the combined length of prostomium and palps, with 18 articles ( Figs 5A , 6B ); lateral antennae shorter than median one, with 15 articles ( Figs 5A , 6B ). Peristomium shorter than subsequent segments; well-visible nuchal organs ( Fig. 6B , arrows, C); dorsal tentacular cirri similar in length to median antenna, with 16–17 articles ( Fig. 5A ); ventral tentacular cirri similar to lateral antennae, with about 10 articles ( Fig. 6B ). Dorsal cirri longer on anterior segments, with 17-19 articles, becoming shorter at midbody (7 articles) and posterior (5 articles) segments ( Figs 5 A–C, 6B, E); with slight variation in size, meaning that a short one is followed by a slightly longer one, and the next one is again short and the next one slightly longer, along the body; articles relatively shorter and thicker at bases, gradually decreasing thickness towards distal end, ending in rounded tips ( Figs 5 A–C, 6B, E). Thin, digitiform ventral cirri, shorter than parapodial lobes ( Fig. 6E ). Parapodial lobes with two lips, anterior one rounded, posterior one digitiform, longer than anterior one ( Fig. 6B, E ). Compound chaetae heterogomph falcigers, with relatively short articles except those of anteriormost chaetae ( Figs 5D , 6D, F ), bidentate, with proximal tooth clearly smaller and thinner than distal one, almost absent in some posterior chaetae ( Figs 5F , 6K ). Anterior parapodia ( Fig. 6B, E ), with 8–10 compound chaetae, with slightly elongated, bidentate articles, short, straight marginal spines; dorsal ones long and relatively thick, with articles ca. 44 µm long; progressively shorter and narrower ventrally, most ventral articles ca. 17 µm long ( Figs 5D , 6D, F ). Number of chaetae per parapodium progressively decreasing towards posterior segments. Midbody parapodia with 3–4 compound chaetae, with blades shorter and wider than those of anterior parapodia, 22 µm long dorsally, 16 µm ventrally; shafts of most dorsal chaeta rather thick, appearing fused with blade, still clearly distinguishable ( Figs 5E , 6 G–J). Posterior parapodia each with three compound chaetae, similar but shorter than those on midbody, not fused either; blades 16 µm dorsally, 14 µm ventrally ( Figs 5F , 6K ). Dorsal and ventral simple capillary chaetae not seen. Anterior parapodia with four aciculae, one with rounded tip and three with oblique tips ( Fig. 5G ); midbody parapodia with two aciculae, with oblique tips ( Fig. 5H ); posterior parapodia with solitary, acuminate acicula ( Fig. 5I ). Pharynx long, extending along 10 segments; pharyngeal tooth, acute, on anterior pharyngeal margin ( Fig. 5A ). Proventricle shorter and similarly wider than pharynx, extending along approximately five segments ( Fig. 5A ), with about 32 muscle cell rows. Pygidium short, with two anal cirri with about 10-12 articles ( Fig. 5C ).

Remarks. Syllis hampirmenyatu n. sp., is characterized by having an elongated thin body, short and non-markedly thickened cirri, formed by relatively few articles and with a rounded tip, decreasing in length towards posterior segments, and posterior parapodium with three chaetae with short and wide blades appearing to be fused with shafts, but still clearly distinguishable from each other, bidentate, with proximal tooth clearly smaller and thinner than distal one. It belongs to the same group as Syllis gracilis Grube, 1840 , an Atlanto-Mediterranean species having only two very thick chaetae per parapodia at midbody, with completely fused shafts and blades, as well as much thicker dorsal cirri ( San Martín 2003). Syllis picta ( Kinberg 1865) , from the Indo-Pacific, also has three chaetae per parapodia at midbody, with thickened shafts, especially the most dorsal chaeta that has also fused shaft and blade still showing the line of fusion perceptible. Moreover, these two species have very short, unidentate blades and the midbody cirri are clearly thickened ( Álvarez-Campos et al. 2015a; Ba-Akdah et al. 2018). Syllis ypsiloides Aguado, San Martín & Ten Hove, 2008 , from Indonesia and the Philippines, also has fused shaft and blade in the most dorsal midbody chaetae and the ends of blades are more pointed than the other species ( Aguado et al. 2008). There seem to be numerous species with these characteristics (i.e., midbody chaetae with enlarged shaft and different degrees of blade fusion) all over the world, which have been misdentified as Syllis gracilis ( Álvarez-Campos et al. 2017a).

Etymology. The specific name comes from the Indonesian Hampir, meaning “almost” and Menyatu, meaning “fused”; it refers to the degree of fusion of the dorsal-most midbody chaetae. East Timor is one of the two independent states that constitute the island of Timor, where Indonesian, among other languages, is spoken. Therefore, it seemed appropriate that the etymology of this new species described had a meaning in Indonesian.

Habitat. Dead coral rubble, around 16 m depth.

Distribution. Only known from the type locality at East Timor.

Figures

FIGURE 5. Syllis hampirmenyatu n. sp. Holotype (AM W.53024), drawn from preserved specimen. A) anterior end, dorsal view. B) midbody segments, dorsal view. C) pygidium and anal cirri, dorsal view. D) compound chaetae, anterior parapodium. E) compound chaetae, midbody parapodium. F) compound chaetae, posterior parapodium. G) aciculae, anterior parapodium. H) aciculae midbody parapodium. I) acicula, posterior parapodium. Scale bars: 20µm.

FIGURE 6. Syllis hampirmenyatu n. sp. Paratype (AM W.45645). Scanning Electron Micrographs. A) complete specimen, anterior end (right), posterior end (left), lateral view. B) prostomium, dorsal view. Nuchal organs indicated by arrows. C) detail of nuchal organ. D) compound chaetae, anterior parapodium. E) anterior parapodia, lateral view. F) detail of compound chaeta, anterior parapodium. G) detail of compound chaeta, midbody parapodium. H), I), J) compound chaetae, midbody parapodium. K) compound chaetae, posterior parapodium.