Ancistrosyllis kornkanokae, Plathong & Dean & Plathong, 2021

Plathong, Jintana, Dean, Harlan K. & Plathong, Sakanan, 2021, Four new species of Pilargidae (Annelida: Pilarginae) from the Gulf of Thailand, Zootaxa 5071 (4), pp. 537-562 : 541-542

Ancistrosyllis kornkanokae sp. nov.

Figs 2–4

Material examined. Twenty one specimens, collected from the Songkhla Sea , Gulf of Thailand, Western Pacific. Coll. MEM (Marine Ecosearch Management Co., Ltd.), mud mixed with sand and shells. Holotype: PSUZC-POL- 0187 (1 spec.), S02 (7°31’44”N, 100°28’15”E), 15 Mar 2016 , 10.0 m. Paratypes: PSUZC-POL-0188 (1 spec.), S07 (7°44’01”N, 100°43’02”E), 11 Oct 2012, 26.5 m; PSUZC-POL-0189 (1 spec. on SEM stub), S06 (7°20’10”N, 100°36’59”E), 20 Feb 2013, 15.5 m; PSUZC-POL-0190 (1 spec.), S09-17 (7°31’55”N, 100°43’06”E), 16 Mar 2013, 24.0 m; PSUZC-POL-0191 (1 spec.), S21 (7°33’17”N, 100°46’43”E), 3 Jun 2013, 24.0 m; PSUZC- POL-0192 (1 spec.), S24 (7°39’22”N, 100°49’01”E), 30 Oct 2014, 27.0 m; PSUZC-POL-0193 (1 spec.), S01 (7°46’29”N, 100°24’42”E), 20 May 2015, 9.5 m; PSUZC-POL-0194 (1 spec.), S19 (7°21’01”N, 7°21’01”E), 17 Jul 2015, 14.0 m; PSUZC-POL-0195 (3 specs., 1 spec. on SEM stub), S08 (7°29’10”N, 100°47’06”E), 16 Mar 2016, 25.0 m; PSUZC-POL-0196 (1 spec. on SEM stub), S09-3 (7°32’1”N, 100°42’41”E), 16 Aug 2018, 24.0 m; PSUZC-POL-0197 (1 spec.), S08 (7°29’10”N, 100°47’06”E), 5 May 2016, 25.0 m; PSUZC-POL-0198 (1 spec.), S03 (7°21’02”N, 100°31’45”E), 18 Oct 2016, 9.0 m; PSUZC-POL-0199 (3 specs., 1 spec. on SEM stub), S14 (7°26’14”N, 100°36’13”E), 18 Aug 2018, 15.5 m.

Additional Material. 2 specs., S07 (7°44’01”N, 100°43’02”E), 18 May 2016, 26.5 m; 2 specs., S09-10 (7°31’56”N, 100°42’47”E), 17 Mar 2013, 24.3 m.

Type locality. Songkhla Sea , Gulf of Thailand ( Fig. 1A ) .

Diagnosis. Ancistrosyllis lacking eyespots; median and lateral antennae present; tentacular cirri elongate. Dorsal cirri from chaetiger 1; ventral cirri from chaetiger 3. Notopodial hooks from chaetiger 3; neurochaetae with 2–3 short limbate chaetae per bundle, each with curved pointed tips and non-limbate capillary chaetae.

Description. Holotype complete, 14.2 mm long and 0.45 mm wide for 66 chaetigers. Body whitish, transparent with eggs within body cavity. Paratypes incomplete, depressed, tapered anteriorly, 1.1–6.7 mm long, 0.26–0.50 mm wide with 9–34 chaetigers. Prostomium bilobed, short, broad, papillose, wider than long (163 µm length and 355 µm wide); lateral antennae shorter than palps ( Figs 2A, B, D , 3A ). Posterior prostomial margin with minute papilla like median antenna (23 µm length and 26 µm wide) ( Figs 2B–D , 4A ). Eyespots absent, palps with small ventrolateral palpal papillae ( Figs 2A, D , 3A ). Proboscis retracted in holotype, visible in SEM specimen.

Peristomium short; tentacular cirri two pairs, elongate, papillose, subequal, dorsal tentacular cirri slightly longer than ventrals ( Figs 2A–B, D , 4A ).

Parapodia sub-biramous with reduced notopodial lobe; neuropodia truncate, straight. Dorsal cirri from first chaetiger, long, slender, papillose, longer than tentacular cirri; first dorsal cirri 3.8 times length of that of chaetiger 2; dorsal cirri increase in length from chaetiger 3 to about chaetiger 10 then decrease in length to posterior region. Ventral cirri from chaetiger 3, shorter than dorsal cirri.

Notopodia each with single aciculum; large, strongly curved notopodial hooks ( Figs 2D , 3A–C , 4B ) from chaetiger 3 ( Figs 2A, 2D , 4B ) with 1–2 hooks per parapodium to the end of body. Neurochaetal bundles with 2–3 short limbate chaetae with curved pointed tips (unidentate) and up to six long, narrow, finely non-limbate capillary chaetae ( Figs 3A, B, D–F , 4 ). Pygidium with two short, digitate, papillose anal cirri.

Etymology. The new species name is in honor of Miss Kornkanok Charoenmas of the Marine Ecosearch Management Company who has worked on the data base and distribution maps of the benthos in Thailand for more than 10 years.

Habitat. Found in 9 – 27 m depth, in mud mixed with sand and shells.

Distribution. Songkhla Sea, Gulf of Thailand, Western Pacific.

Remarks. Ancistrosyllis kornkanokae sp.nov. belongs to the second group of species in the genus Ancistrosyllis characterized by the presence of both a median antenna and two lateral antennae and the absence of eyespots ( Table 1). Further, A. kornkanokae sp. nov. also has elongate, digitate, papillose tentacular cirri which differentiates this species from the other species in this group. Dorsal cirri are from chaetiger 1, longer than those present along subsequent chaetigers. Ventral cirri short, conical, papillose from chaetiger 3. It resembles A. fioronii Fiege & Böggemann, 1999 from North Sea, Atlantic Ocean; A. hartmanae Pettibone, 1966 from Chesapeake Bay, USA; and A. nakkaritae sp. nov. in group two by having a median antenna, two lateral antennae, and first notopodial hooks begin at chaetiger 3.

However, A. kornkanokae sp. nov. differs from A. fioronii and A. nakkaritae sp. nov. because they all have the first ventral cirri from different chaetigers. The first ventral cirri are present at chaetiger 3 in A. kornkanokae but in A. fioronii and A. nakkaritae sp. nov., first ventral cirri start from chaetiger 2 and chaetiger 1, respectively. Moreover, tentacular cirri in A. kornkanokae are longer than A. fioronii (in A. fioronii has short tentacular). A. kornkanokae sp. nov. also differs from A. fioronii by have two types of neurochaetae as short limbate chaeta and long non - limbate chaeta with unidentate tips. Whereas A. fioronii has only one type of non - limbate capillary neurochaeta with bidentate tip ( Fiege & Böggemann 1999).

Ancistrosyllis kornkanokae sp. nov. differs from A. nakkaritae sp. nov. in that all neurochaetae are unidentate but in A. nakkaritae sp. nov., all neurochaetae have bifid tips.

Ancistrosyllis kornkanokae sp. nov. mostly resembles A. hartmanae Pettibone, 1966 in having the first dorsal and ventral cirri occurring on similar chaetigers (chaetiger 1 and chaetiger 3, respectively) and first hooks occur from chaetiger 3 ( Pettibone 1966). However, in A. hartmanae eyespots are present and the tentacular cirri are short, while in A. kornkanokae sp. nov. eyespots are absent and the tentacular cirri are longer ( Table 1).

Figures

FIGURE 1. Sampling sites in the Songkhla Sea, Gulf of Thailand, showing stations where new species of Ancistrosyllis and Carbira specimens were collected. A. Ancistrosyllis kornkanokae sp. nov. (triangles); B. Ancistrosyllis nakkaritae sp. nov. (squares); C. Cabira saithipae sp. nov. (circles); D. Cabira thailandica sp. nov. (stars).

FIGURE 2. Scanning electron micrographs of Ancistrosyllis kornkanokae sp. nov. (PSUZC-POL-0189) showA.Anterior region, dorsal view; B. Prostomium, dorsal view; C. Median antenna, lateral view; D. Anterior end, lateral view. Abbreviations: dc: dorsal cirri, la: lateral antenna, ma: median antenna, nh: notopodial hook, pr: prostomium, tc: tentacular cirri, vpp: ventrolateral palpal papilla.

FIGURE 3. Scanning electron micrographs of Ancistrosyllis kornkanokae sp. nov. (A–C, PSUZC-POL-0189; D–F, PSUZC- POL-0196) show A. Anterior parapodia, dorsal view; B. Anterior parapodia, ventral view; C. Notopodial hook, lateral view; D. Neurochaetae, in the box shows Short limbate chaeta, lateral view; E. Close up short limbate chaeta with unidentate tip, lateral view; F. Tip of long capillary non limbate chaetae with unidentate tip. Abbreviations: dc: dorsal cirri, nlc: non-limbate capillary chaeta, nc: neurochaetae, nh: notopodial hook, slc: short limbate chaetae, vc: ventral cirri.

FIGURE 4. Line drawings of Ancistrosyllis kornkanokae sp. nov. illustrate A. Anterior end, dorsal view; B. Neurochaetae, lateral view; C. Close up short limbate chaetae with unidentate tips. Abbreviations: dc: dorsal cirri, la: lateral antenna, ma: median antenna, nc: neurochaetae, nh: notopodial hook, pa: palp, slc: short limbate chaeta, tc: tentacular cirri, vc: ventral cirri, vpp: ventrolateral palpal papilla.