Ancistrosyllis nakkaritae, 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 : 545-550

Ancistrosyllis nakkaritae sp. nov.

Figs 5–8

Material examined. Five 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- 0310 (1 spec.), S06 (7°20’9”N, 100°36’58”E), 15 Mar 2016, 15.5 m . Paratypes: PSUZC-POL-0311 (1 spec., on SEM stub), S06 (7°20’10”N, 100°36’59”E), 12 Feb 2015, 15.5 m; PSUZC-POL-0312 (1 spec.), S17 (7°36’16”N, 100°34’48”E), 7 Oct 2013, 18.0 m; PSUZC-POL-0313 (1 spec.), S02 (7°31’44”N, 100°28’15”E), 15 Mar 2016, 10.0 m; PSUZC-POL-0314 (1 spec.), S09-3 (7°32’1”N, 100°42’41”E), 16 Aug 2018, 24.0 m.

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

Diagnosis. Ancistrosyllis nakkaritae sp. nov. is characterized by the absence of eyespots; the presence of a minute, conspicuous median antenna; elongate lateral antennae and tentacular cirri; and the first dorsal and ventral cirri start from chaetiger one. Dorsal and ventral tentacular cirri papillate, as long as lateral antennae, longer than first dorsal cirri. Notopodial hooks from chaetiger 3.

Description. Holotype incomplete, 8.7 mm long, 0.6 mm wide with 44 segments. Paratypes incomplete with 2.9–6.7 mm long, 0.3–0.7 mm wide and 21–40 segments. Body whitish, dorsal numerous of long papillae on the dorsal and ventral body throughout.

Prostomium broad, papillose, with two elongate papillose digitiform lateral antennae (162 and 130 µm long), longer than the palps ( Figs 5A–B , 6A–D , 8A ). Median antenna very small, conspicuous present on the posterior of prostomium ( Figs 5B , 6B, D , 8A ). Eyespots absent, palps with small, digitate ventrolateral palpal papillae ( Figs 5A–B , 6C–D , 8A ). Proboscis retracted in holotype and paratypes.

Peristomium short with two pairs of elongate, digitate, papillose tentacular cirri (up to 203 µm in complete dorsal tentacular cirri) inserted laterally, shorter than palps and longer than first dorsal cirri; dorsal tentacular cirri longer than ventral tentacular cirri and slightly longer than lateral antennae ( Figs 5A–B , 6A–D , 8A ).

Parapodia sub-biramous, with reduced notopodial lobe; neuropodia truncate and straight. Dorsal cirri long, conical, papillose with numerous large, elongate papillae; present from first chaetiger. First dorsal cirri long, about twice length of dorsal cirri at chaetiger 2. Subsequent several dorsal cirri shorter than those of chaetiger 1 but at chaetiger 3 dorsal cirri gradually increase in length until those of midbody being of greater length than those of chaetiger 1. Ventral cirri present from first chaetiger, shorter than dorsal cirri, longer than neuropodial lobes ( Figs 5A, C , 6A–D , 7A–C , 8A, B ). Notopodia each with single aciculum, chaetae absent. Large notopodial hooks present from chaetiger 3; strongly curved with one hook per parapodium ( Figs 5A , 6A, D , 7B , 8A ). Neurochaetal bundles with 2–4 short limbate chaetae with bifid tips and 5–8 long, narrow, finely toothed non-limbate chaetae with bifid tips ( Figs 7A–D , 8B–C ).

Pygidium unknown.

Reproduction. Holotype with eggs (collected in Mar 2016), ( Fig. 7D ).

Etymology. The new species is named in honor of Miss Nuenghathai Nakkarit, the marine biologist at MEM who has worked with us from the beginning of the Songkhla Sea project.

Habitat. Found at 10 – 24 m depth, mud mixed with sand and shells.

Distribution. Songkhla Sea, Gulf of Thailand, Western Pacific ( Fig. 1B ).

Remarks. Ancistrosyllis nakkaritae 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. It mostly resembles A. fioronii Fiege & Böggemann, 1999 and A. kornkanokae sp. nov. of this group by having the first dorsal cirri start from chaetiger 1, the absence of eyespots and first notopodial hooks begin at chaetiger 3 ( Table 1).

Ancistrosyllis nakkaritae sp. nov. differs from A. fioronii and A. kornkanokae sp. nov. in having the first ventral cirri from chaetiger 1 instead chaetiger 2 as in A. fioronii ( Fiege & Böggemann 1999) and chaetiger 3 in A. kornkanokae sp. nov.. Moreover, the lateral antennae and tentacular cirri in A. nakkaritae sp. nov. are longer than those of A. fioronii and A. kornkanokae sp. nov., and the median antenna in A. nakkaritae sp. nov. is conspicuously smaller. A. nakkaritae sp. nov. also differs from A. fioronii by having two types of neurochaetae and a higher

A. carolinensis Gar- Western Atlantic, North Absent Globular tentacular 1 2 6 Low, rounded Rounded or trun- Gardiner 1976 diner, 1976 Carolina to the Gulf of cirri cate,

Mexico conical retractile acicular lobes

A. falcata Day, 1957 South Africa, Inhaca Present Fusiform, papillose 1 1 7 Reduced Truncate, bent Day 1957 Island tentacular cirri downwards

A. hamata Hartman , Pacific Ocean, Southern Absent Short, subequal 1 3 4–7 Short, rounded Short, truncate, Hartman 1960 1960 California tentacular cirri longer than notopodia

A. matlaensis Mandal & R. Matla, Sundarban Absent Conical , papillose 1 2 7 Reduced Truncate, straight Mandal & Deb Deb, 2018 Estuarine System, India tentacular cirri 2018 A. papillosa Jones, 1961 Florida, intertidal Present Long tentacular cirri 1 3 3 Reduced Conical, well devel- Jones 1961 (longer than palps) oped number of neurochaetae per fascicle than A. fioronii with up to 12 chaetae per bundle while A. fioronii has only a single type neurochaeta with 4 – 6 chaetae per bundle ( Fiege & Böggemann 1999). Furthermore, A. nakkaritae sp. nov. also differs from A. kornkanokae sp. nov. by all neurochaetae with bifid tips, papillae on the body surface and the parapodia are numerous and longer and larger. The neurochaetae of A. kornkanokae sp. nov. are unidentate and the papillae on the body surface are smaller than in A. nakkaritae .

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 5. Light photographs of Ancistrosyllis nakkaritae sp. nov. stained with Shirlastain-A (Holotype, PSUZC-POL-0310) A. Anterior region, dorsal view; B. Close up prostomium, dorsal view; C. Close up long papillae at dorsal cirri, lateral view; D. Eggs in parapodia region, dorsal view.Abbreviations: dc: dorsal cirri, dtc: dorsal tentacular cirri, la: lateral antenna, ma: median antenna, nh: notopodial hook, pa: palp, pr: prostomium, tc: tentacular cirri, vc: ventral cirri, vpp: ventrolateral palpal papilla.

FIGURE 6. Scanning electron micrographs of Ancistrosyllis nakkaritae sp. nov. (PSUZC-POL-0311) show A.Anterior region, dorsal view; B. Anterior end, dorsal view; C. Same, lateral view. Abbreviations: dc: dorsal cirri, la: lateral antenna, ma: median antenna, nc: neurochaetae, nh: notopodial hook, tc: tentacular cirri, vc: ventral cirri, vpp: ventrolateral palpal papilla.

FIGURE 7. Scanning electron micrographs of Ancistrosyllis nakkaritae sp. nov. (PSUZC-POL-0311) show A. First four chaetigers, ventral view; B. Anterior parapodia, dorsal view; C. Anterior neurochaetae, ventral view; D. Same, close up short limbate chaetae with bifid tip, lateral view; E. Short limbate chaeta. Abbreviations: dc: dorsal cirri, nh: notopodial hook, nlc: non-limbate capillary chaeta, slc: short limbate chaeta, vc: ventral cirri.

FIGURE 8. Line drawings of Ancistrosyllis nakkaritae sp. nov. illustrate A. Anterior region, dorsal view; B. Parapodia, lateral view; C. Close up Short limbate chaeta Abbreviations: dc: dorsal cirri, la: lateral antennae, ma: median antenna, nh: notopodial hook, nlc: non-limbate capillary chaeta, pa: palp, slc: short limbate chaeta, tc: tentacular cirri, vc: ventral cirri, vpp: ventrolateral palpal papilla.