Cabira thailandica, 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 : 556-561

Cabira thailandica sp. nov.

Figs 13–15

Material examined. 76 specimens, collected from the Songkhla Sea , Gulf of Thailand, Western Pacific. Coll. MEM (Marine Ecosearch Management Co., Ltd.) mud mixed with sand and shells. Details of geographic positions and environmental characteristics of sampling stations are in Table 2. Holotype: PSUZC-POL-0200 (1 spec.), S52 (7°42’05”N, 100°40’15”E), 11 Feb 2015 , 23.0 m. Paratypes: PSUZC-POL-0201 (1 spec.), S09-10 (7°31’56”N, 100°42’47”E), 3 Jul 2014, 24.3 m; PSUZC-POL-0202 (1 spec.), S09-6 (7°32’13”N, 100°42’21”E), 20 Feb 2015, 23.6 m; PSUZC-POL-0203 (1 spec.), S02 (7°31’44”N, 100°28’15”E), 5 Feb 2015, 10.0 m; PSUZC-POL-0204 (7 specs., 4 specs. on SEM stubs), S03 (7°21’02”N, 100°31’45”E), 2 Dec 2015, 9.0 m; PSUZC-POL-0205 (1 spec.), S46 (7°40’58”N, 100°29’39”E), 22 Feb 2015, 14.5 m; PSUZC-POL-0206 (1 spec.), S19 (7°21’01”N, 100°36’54”E), 17 Jul 2015, 14.0 m; PSUZC-POL-0207 (1 spec.), S08 (7°29’10”N, 100°47’06”E), 16 Mar 2016, 25.0 m; PSUZC- POL-0208 (1 spec.), S14 (7°26’14”N, 100°36’13”E), 20 Sep 2017, 15.5 m; PSUZC-POL-0209 (1 spec.), S11-2 (7°31’01”N, 100°36’39”E), 27 Mar 2017, 18.9 m; PSUZC-POL-0210 (1 spec.), S11-9 (7°31’11”N, 100°36’18”E), 27 Mar 2017, 18.7 m; PSUZC-POL-0211 (1 spec.), S10-8 (7°28’44”N, 100°36’11”E), 5 May 2018, 18.5 m; PSUZC-POL-0212 (1 spec.), S09-3 (7°32’01”N, 100°42’41”E), 16 Aug 2018, 24.0 m; AM W.52912 (1 spec.), S05 (7°34’03”N, 100°33’57”E), 13 Oct 2015, 16.5 m ; AM W. 52913 (1 spec.), S06 (7°20’10”N, 100°36’59”E), 13 Oct 2015, 15.5 m .

Additional Material. S02 (7°31’44”N, 100°28’15”E), 6 May 2014 (3 specs.), 21 May 2015 (1 spec.), 10 m; S03 (7°21’02”N, 100°31’45”E), 6 May 2014 (1 spec.), 2 Dec 2015 (6 specs.), 13 Oct 2015 (1 spec.), 9.0 m; S04 (7°49’22”N, 100°29’11”E), 20 May 2015 (2 specs.), 14 Oct 2015 (1 spec.), 17.5 m; S05 (7°34’03”N, 100°33’57”E), 6 May 2014 (4 specs.), 21 May 2015 (5 specs.), 13 Oct 2015 (3 specs.), 2 Dec 2015 (2 specs.), 15 Mar 2016 (1 spec.), 18 Oct 2016 (1 spec.), 16.5 m; S06 (7°20’10”N, 100°36’59”E), 6 May 2014 (2 specs.), 10 Sep 2014 (1 spec.), 2 Dec 2015 (1 spec.), 15 May 2016 (1 spec.), 17 May 2016 (1 spec.), 15.5 m; S07 (7°44’01”N, 100°43’02”E), 6 May 2014 (1 spec.), 26 Jan 2015 (2 specs.), 14 Oct 2015 (3 specs.), 18 May 2016 (2 specs.), 26.5 m; S08 (7°29’10”N, 100°47’06”E), 16 Mar 2016 (1 spec.), 18 May 2016 (1 spec.), 19 Oct 2016 (1 spec.), 25.0 m; S09-3 (7°32’01”N, 100°42’41”E), 2 Mar 2016 (1 spec.), 24.0 m; S09-7 (7°32’19”N, 100°42’24”E), 1 Mar 2016 (1 spec.), 23.7 m; S10-4 (7°28’14”N, 100°36’39”E), 15 Feb 2015 (1 spec.), 19.0 m; S14 (7°26’13”N, 100°36’12”E), 20 Feb 2015 (3 specs.), 15.5 m; S17 (7°36’16”N, 100°34’48”E), 7 Oct 2015 (2 specs.), 18.0 m; S18-1 (7°21’38”N, 100°37’01”E), 3 Jun 2015 (4 specs.), 16.0 m; S18-2 (7°21’34”N, 100°37’06”E), 3 Jun 2015 (2 specs.), 16.0 m; S19 (7°21’01”N, 7°21’01”E), 17 Jul 2015 (5 specs.), 14.0 m; S21 (7°33’16”N, 100°46’43”E), 17 Feb 2015 (1 spec.), 24.0 m; S23 (7°49’20”N, 100°33’17”E), 14 Jul 2015 (3 specs.), 20.5 m; S25 (7°16’28”N, 100°48’46”E), 13 Jul 2015 (1 spec.), 6 Oct 2015 (1 spec.), 22.0 m; S38 (7°37’29”N, 100°42’53”E), 3 Jun 2015 (3 specs.), 22.0 m; S40 (7°26’50”N, 100°44’49”E), 26 Sep 2011 (1 spec.), 21.0 m; S45 (7°47’46”N, 100°28’10”E), 22 Feb 2015 (1 spec.), 14.3 m; S47 (7°34’04”N, 100°31’37”E), 22 Feb 2015 (11 specs.), 14.0 m; S48 (7°47’38”N, 100°42’29”E), 22 Feb 2015 (1 spec.), 24.6 m; S50 (7°35’01”N, 100°46’58”E), 21 Feb 2015 (2 specs.), 22.5 m; S53 (7°27’59”N, 100°31’47”E), 23 Feb 2015 (1 spec.), 14.3 m.

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

Diagnosis. Cabira thailandica sp. nov. is characterized by the presence of minute papilliform lateral antennae and tentacular cirri; median antenna absent; dorsal cirri begin on chaetiger 1 and ventral cirri from chaetiger 3. Notopodial hooks occur from chaetiger 7. Single type of neurochaetae, long, slender, non-limbate capillary chaeta with bidentate tips.

Description. A small species, holotype complete, 14.4 mm long and 0.3 mm wide for 53 chaetigers. Body papillose, whitish, transparent with brown and light tan eggs visible in the body cavity, widest anteriorly. Paratypes, one complete about 48 chaetigers (13.8 mm long, 0.9 mm wide), one with the last six chaetigers regenerating (350 μm long, 126 μm wide), no hooks present in the regenerating region but with two small digitate anal cirri about 57 μm long (others incomplete, 1.6–21.1 mm long, 0.37–0.74 mm wide with 14–80 segments).

Prostomium bilobed, short, broad, wider than long (163 µm length and 355 µm wide); median antenna and eyespots absent. One pair of lateral antennae; short, small, conical and papillose. Palps posterior on prostomium with longitudinal folds. Pair of nuchal organs on the posterolateral margin of the prostomium ( Fig. 13C ). Peristomium fuse with prostomium, two pairs of short, conical, papillose tentacular cirri insert laterally ( Fig. 11A–C ). Dorsal tentacular cirri slightly shorter than ventral cirri.

Parapodia sub-biramous; notopodia reduced, each with very short papillated dorsal cirri, single acicular, and strongly curved notopodial hooks start from chaetiger 7 ( Figs 13A–B , 14B , 15A–B ). Dorsal cirri present from first chaetiger, continue throughout body. Ventral cirri present from chaetiger 3 ( Fig. 13A ). Neuropodia short, reduced, all long narrow, non - limbate capillary chaetae with bidentate tips, vary in length, up to six chaetae per fascicle ( Figs 14A, B, D, E , 15C ).

Pygidium with two long, digitate and papillose anal cirri.

Etymology. The new species is named after Thailand, the country where the specimens were collected.

Habitat. Found at 10 – 27 m depth, in mud mixed with sand and shells.

Distribution. Widely present in the Songkhla Sea, Gulf of Thailand, Western Pacific.

Remarks. Cabira thailandica sp. nov. is characterized by the absence of both eyespots and a median antenna, the presence of two short, papillate lateral antennae, dorsal cirri from the first chaetiger, ventral cirri from chaetiger 3 and notopodial hooks from chaetiger 7. All neurochaetae are narrow, non - limbate chaetae with bidentate tips. It belongs to group I of Cabira species by having only a single type of neurochaetae ( Table 2).

Cabira thailandica sp. nov. resembles C. incerta Webster, 1879 from Western Atlantic and C. rangarajani Mandal, Harkantra & Salazar - Vallejo, 2007 from Indian Ocean (Arabian Sea) in that all three species have a single type of neurochaetae and the first notopodial hooks beginning on chaetiger 7 ( Webster 1879; Mandal et al. 2007). However, C. thailandica sp. nov. can be distinguished from C. incerta and C. rangarajani by having bidentate neurochaetae which are lacking in C. incerta and C. rangarajani .

Cabira thailandica sp. nov. differs from C. saithipae sp. nov. by having a single type of long, non - limbate chaeta with bidentate tips, the first ventral cirri occur at chaetiger 3 and first notopodial hooks begin on chaetiger 7. Cabira saithipae sp. nov. has three types of neurochaetae, ventral cirri begin at chaetiger 1 and notopodial hooks start from chaetiger 8.

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 11. Scanning electron micrographs of Cabira saithipae sp. nov. (PSUZC-POL-0343) show A–D. Anterior parapodia and neurochaetae, D. Show short recurved tip chaeta (in circle) and non-limbate chaeta (in the box), lateral view; E. Close up short recurved tip chaeta, lateral view; F. Tip of non-limbate capillary chaeta with subdistally foliose, finely denticulate, tip falcate, lateral view.Abbreviations: ac: acicular chaeta, dc: dorsal cirri, nc: neurochaetae, nh: notopodial hook, nlc: non-limbate capillary chaeta, src: short recurved tip chaeta.

FIGURE 13. Scanning electron micrographs of Cabira thailandica sp. nov. (PSUZC-POL-0204) show A. Anterior region, lateral view; B. Same, dorsal view; C. Prostomium, lateral terior chaetiger with notopodial hook, dorsal view; C. Anterior parapodia, lateral view; D. Neurochaetae, show bidentate tip (in circle), lateral view; E. Close up bidentate tip, lateral view. Abbreviations: dc: dorsal cirri, nc: neurochaetae, nh: notopodial hook, nlc: non-limbate capillary chaeta, vc: ventral cirri vpp: ventrolateral palpal papilla.

FIGURE 14. Scanning electron micrographs of Ancistrosyllis thailandica sp. nov. (PSUZC-POL-0204) show A. Anterior chaetiger without notopodial hook, left side, lateral view; B. Anterior chaetiger with notopodial hook, dorsal view; C. Anterior parapodia, lateral view; D. Neurochaetae, show bidentate tip (in circle), lateral view; E. Close up bidentate tip, lateral view. Abbreviations: dc: dorsal cirri, nc: neurochaetae, nh: notopodial hook, nlc: non-limbate capillary chaeta, vc: ventral cirri.

FIGURE 15. Line drawings of Cabira thailandica sp. nov. illustrate A. Anterior end, lateral view; B. Anterior parapodia, ventral view; C. Close up tip of neurochaeta. Abbreviations: dc: dorsal cirri, la: lateral antenna, nc: neurochaetae, nh: notopodial hook, pa: palp, vc: ventral cirri, tc: tentacular cirri, vpp: ventrolateral palpal papilla.