Cabira saithipae, 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 : 551-556

Cabira saithipae sp. nov.

Figs 9–12

Material examined. Eight specimens, collected from Songkhla Sea , the Gulf of Thailand, Western Pacific. Coll. MEM (Marine Ecosearch Management Co., Ltd.), mud mixed with sand and shells. Holotype: PSUZC-POL-0338 (1 spec.), S09-5 (7°32’01”N, 100°42’30”E), 17 Aug 2018 , 24.0 m. Paratypes: PSUZC-POL-0339 (1 spec.), S14 (7°26’14”N, 100°36’13”E), 5 Mar 2014, 15.5 m; PSUZC-POL-0340 (1 spec.), S18-1 (7°21’38”N, 100°37’01”E), 3 Jun 2015, 16.0 m; PSUZC-POL-0341(1 spec.), S18-2 (7°21’34”N, 100°37’06”E), 3 Jun 2015, 16 m; PSUZC-POL- 0342 (1 spec.), S09-3 (7°32’01”N, 100°42’42”E), 2 Mar 2016, 24.0 m; PSUZC-POL-0343 (2 specs., 1 on SEM stub), S08 (7°29’10”N, 100°47’06”E), 18 May 2016, 25.0 m; PSUZC-POL-0344 (1 spec.), S09-1 (7°32’13”N, 100°42’42”E), 17 Aug 2018, 24.0 m.

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

Diagnosis. Cabira saithipae sp. nov. is characterized by the presence of minute papilliform lateral antennae and tentacular cirri, the lack of a median antenna, and dorsal and ventral cirri beginning on chaetiger 1. Notopodial hooks occur from chaetiger 8. Three types of neurochaetae in the anterior parapodia: long, slender, non-limbate chaeta, short, broad chaeta with strongly recurved tips, and short, broad chaeta with curved tips.

Description. Holotype largest specimen, incomplete, 11.1 mm long and 0.46 mm wide, for about 64 chaetigers. One paratype complete with one anal cirri (other anal cirri broken), about 50 chaetigers, 7.2 mm long and 0.3 mm wide. Other paratypes incomplete, 15 – 38 chaetigers, 1.8–6.6 mm long, 0.2–0.4 mm wide. Body whitish, papillose and annulated. Holotype, present large conical papillae at dorsal and ventral of chaetigers 7–17 ( Fig. 9A, D ).

Prostomium bilobed, short, broad, wider than long. Median antenna and eyespots absent; palps small, paired minute ventrolateral palpal papillae. One pair of small, short, button-like lateral antennae, basally papillose ( Figs 9A–B , 10A–C , 12A ). Pair of nuchal organs on the posterolateral margin of the prostomium ( Fig. 10C ).

Peristomium fused with prostomium, two pairs of small basally papillose, conical, tentacular cirri inserted laterally ( Figs 10A–C , 12A ). Proboscis not everted in holotype, everted in smallest paratype with rows of denticles ( Fig. 9C ).

Dorsal tentacular cirri slightly longer than ventral cirri ( Fig. 10E–F ). Dorsal and ventral cirri are small, papilliform, from first chaetiger.

Parapodia sub-biramous, reduced; notopodial lobes reduced with small dorsal cirrus similar in size throughout. Notopodia with single acicula and 1–2 notopodial hooks. First notopodial hooks start at chaetiger 8 in all specimens; hooks small with strongly curved tip ( Figs 11B , 12A ). Neuropodia reduced, very short with acicular lobe. Anterior chaetigers from chaetiger 2–17 (chaetiger 2–21 in one paratype) with three types of neurochaetae: 1) long, slender, non-limbate chaeta with subdistally foliose, finely denticulate, tip falcate, 2) short chaeta with strong recurved tip and 3) short chaeta with curved tips; about 4–6 chaetae per fascicle; 3 at upper acicular lobe and 3 at the lower acicular lobe. Each parapodia with 1–2 short strong recurved chaetae, 1–3 short slightly recurved chaetae, and 2–3 long, slender, non-limbate chaetae ( Figs 11A–F , 12B–C ). Two types of neurochaetae from chaetiger 18–26 or 27, lacking the short broad chaeta with strongly recurved tip, each with four chaetae per fascicle; one short, narrow chaeta with curved tips and 3 non-limbate capillary chaetae; from chaetiger 28 to posterior parapodia, neuropodia with three capillary chaetae; one long chaeta, longer about twice the length of short ones and two short chaetae, length almosty equal.

Pygidium with two anal cirri (0.05 mm long).

Reproduction. Holotype and paratype were collected in August 2018, body with eggs ( Fig. 9E ).

Etymology. The new species name is honor to Miss Kanoknapat (Saithip) Plathong, older sister of Sakananauthor.

Habitat. Found at 16 – 25 m depth, in mud mixed with sand and shells.

Distribution. Only known from type locality - Songkhla Sea, Gulf of Thailand.

Remarks. Cabira saithipae sp. nov. belongs to the second group (Group II) of Cabira species which have more than one type of chaetae ( Table 2). It mostly resembles C. brevicirris Rangarajan, 1964 from Palk Bay, Southern India which also has long non-limbate chaetae, short chaetae with strong recurved tips, and short chaetae with curved tips. However, C. saithipae sp. nov. differs from C. brevicirris by having all three types of neurochaetae in antererior chaetigers from chaetiger 2 to 17–21, while C. brevicirris has only two types of neurochaetae beginning at chaetigers 4–13 ( Rangarajan 1964; Mandal et al. 2007). In addition, Cabira saithipae sp. nov. has large conical papillae on the posterior edge of the annulations from chaetigers 7–17 both dorsally and ventrally. These conical papillae are absent in C. brevicirris which has mainly square papillae. Moreover, the appearance of the first ventral cirri and the first notopodial hooks in C. saithipae sp. nov. occurs at chaetiger 1 and chaetiger 8, respectively while the first ventral cirri of C. brevicirris , begin at chaetiger 1 or 3 and the first notopodial hooks occurs at chaetiger 6 – 8 ( Rangarajan 1964).

Cabira saithipae sp. nov. also differs from C. thailandica sp. nov. in that there are three types of neurochaetae and bidentate tipped chaetae are lacking while C. thailandica sp. nov. has only a single type of neurochaetae with bidentate tips. Additionally, the first ventral cirri and first notopodial hooks begin at chaetiger 1 and 8, respectively in C. saithipae sp. nov. while they begin at chaetiger 3 and 7 in C. thailandica sp. nov. ( Table 2).

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 9. Light photographs of Cabira saithipae sp. nov. stained with Shirlastain-A (A, B, D, E, PSUZC-POL-0338 holotype; C, PSUZC-POL-0338; F, PSUZC-POL-0341) A. Anterior region, dorsal view in circle shows large conical papillae; B. Close up prostomium, dorsal view; C. Pharynx, ventral view; D. Close up large conical papillae, dorsal view; E. Eggs in parapodia region, dorsal view; F. Pygidium lateral view. Abbreviations: d: denticle, dc: dorsal cirri, la: lateral antennae, pa: palp, pr: prostomium, py: pygidium, tc: tentacular cirri, vpp: ventrolateral palpal papilla.

FIGURE 10. Light photograph and scanning electron micrographs of Cabira saithipae sp. nov. (A, PSUZC-POL-0338 holotype; B–F, PSUZC-POL-0343) show A. Light photo, color in alcohol, lateral view; B. Anterior region, lateral view; C. Prostomium, lateral view; D. Lateral antenna, left side, frontal view; E. Lateral antennae, right side, lateral view; F. Tentacular cirri, left side, lateral view.Abbreviations: dtc: dorsal tentacular cirri, la: lateral antenna, nh: notopodial hook, no: nuchal organ, p: papillae, pa: palp, pr: prostomium, tc: tentacular cirri, vtc: ventral tentacular cirri, vpp: ventrolateral palpal papilla.

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 12. Line drawings of Cabira saithipae sp. nov. illustrate A. Anterior region, dorsal view; B. Parapodia, in circle is short broad recurved tip chaeta, lateral view; C. Close up short recurved tip chaeta. Abbreviations: dc: dorsal cirri, la: lateral antenna, nh: notopodial hook, nlc: non-limbate capillary chaeta, pa: palp, src: short recurved tip chaeta, tc: tentacular cirri, vc: ventral cirri, vpp: ventrolateral palpal papilla.