Ancistrosyllis suksani, Plathong & Plathong & Dean, 2022

Plathong, Sakanan, Plathong, Jintana & Dean, Harlan K., 2022, Two new species of Ancistrosyllis McIntosh, 1878 (Annelida: Pilargidae) from the Gulf of Thailand, Western Pacific, Zootaxa 5128 (2), pp. 195-210 : 205-209

publication ID	https://doi.org/ 10.11646/zootaxa.5128.2.2
publication LSID	lsid:zoobank.org:pub:01AAFD2B-BA1B-409B-B027-BA546B313BD8
DOI	https://doi.org/10.5281/zenodo.6499049
persistent identifier	https://treatment.plazi.org/id/9F688789-2C62-9C15-FF46-2EEDFB2EA99F
treatment provided by	Plazi
scientific name	Ancistrosyllis suksani
status	sp. nov.

Treatment

Ancistrosyllis suksani View in CoL sp. nov.

Figs 6–9 View FIGURE 6 View FIGURE 7 View FIGURE 8 View FIGURE 9

Material examined. Nine specimens collected from the Songkhla Sea and offshore in the Gulf of Thailand, coll. Marine Ecosearch Management Co., Ltd., mud mixed with sand and shells. Holotype: PSUZC-POL-0345 (1 spec.) , S02 (7°31’44”N, 100°28’15”E), 21 Sep. 2016, 10 m. Paratypes: S01 (7°46’29”N, 100°24’42”E), 16 Oct. 2013, 9.5 m; PSUZC-POL-0346 (3 specs., 1 spec. on SEM stub), S01-B1; PSUZC-POL-0347 (1 spec.), S01-B3; PSUZC-POL-0348 (1 spec., on SEM stub), S03 (7°21’02”N, 100°31’45”E), 13 Oct. 2015, 9 m; PSUZC-POL-0349 (1 spec.), GT-UR (8°20’16”N, 101°45’01”E), 9 Sep. 2015, 70 m; PSUZC-POL-0350 (2 specs., 1 spec. on SEM stub), GT-SW (9°22’59”N, 101°21’37”E), 22 May 2020, 50 m.

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

Diagnosis. Ancistrosyllis without eyespots; with a short median antenna and two short lateral antennae. With a pair of short tentacular cirri; dorsal and ventral cirri starting from chaetiger 1. Notopodial hooks from chaetiger 4. Three types of neurochaetae; short, stout, falcates with a small subdistal guard; short limbates with bifid tips; and long non-limbate capillaries with bifid tips.

Description. Holotype complete (pygidial cirri broken), 22.3 mm long, 0.7 mm wide, 99 segments. Paratypes incomplete, anterior region 1.8–8.2 mm long, 0.3–0.8 mm wide with 10–36 segments. Two posterior parts with pygidial cirri. Body depressed, light tan to light brown with numerous light yellow to brown papillae, widest in middle region, tapering anteriorly and posteriorly ( Fig. 6A–C View FIGURE 6 ).

Prostomium short, broad, bilobed, wider than long, with numerous brown papillae; short, small median antenna present on posterior prostomial region; two short lateral antennae present antero-laterally on prostomium, shorter than palps and tentacular cirri ( Figs 6B View FIGURE 6 , 7–D View FIGURE 7 , 9A View FIGURE 9 ). Eyespots absent. Palps biarticulate with very small ventrolateral palpal papillae ( Figs 7B, 7D View FIGURE 7 , 9B View FIGURE 9 ). Pharynx not observed, retracted in holotype and paratypes, extending to chaetiger 4 ( Fig. 6B View FIGURE 6 ).

Peristomium with two pairs of short, digitate, papillate tentacular cirri, longer than lateral antennae, inserted laterally. Dorsal cirri present from chaetiger 1, long, conical, papillose, twice as long as dorsal cirri of chaetiger 2. Ventral cirri present from chaetiger 1, shorter than dorsal cirri ( Figs 6B View FIGURE 6 , 7A–D View FIGURE 7 , 9A–B View FIGURE 9 ).

Parapodia subbiramous, notopodia reduced with a single acicula. Notopodial hooks present from chaetiger 4; large, strong falcate, 1–2 hooks per parapodium with the second one non-emergent ( Figs 6B, 6C View FIGURE 6 , 7A–B View FIGURE 7 ). Neuropodia well-developed conical lobes, conical with a single aciculum ( Figs 6A–B View FIGURE 6 , 7A–B View FIGURE 7 , 8A View FIGURE 8 , 9B View FIGURE 9 ).

Neurochaetae three types: two types of short chaetae and one type of long non-limbate chaeta; 1) short, stout falcates, with small subdistal guard approaching distal tips ( Figs 8 View FIGURE 8 A-C, 9C), 2) short limbate with bifid tips ( Figs 8A, B, D View FIGURE 8 , 9C View FIGURE 9 ) and 3) long non-limbate capillaries with bifid tips ( Fig. 8A, E View FIGURE 8 ). Each neuropodium with 5–7 long nonlimbate capillaries above neuroacicula and 1–2 short, stout falcates with a subdistal guard, 2–3 short bifid limbates, and 1 long non-limbate below neuroacicula ( Figs 8A–E View FIGURE 8 , 9C View FIGURE 9 ).

Pygidium conical with pair of anal cirri.

Small oocytes were found in the body and parapodia of large specimen collected in October 2013 ( Fig. 6D View FIGURE 6 ).

Etymology. The new species is named in honor of Mr. Suksan Jinanarong, the senior staff of Tetra Tech, Inc. ( Thailand) for his work on marine benthos of Songkhla Sea, Gulf of Thailand with our team (MEM and Coral Reefs and Benthos Research Unit) from the beginning of our research.

Habitat. Living in 9–70 m water depth, mud mixed with sand and shells.

Distribution. Gulf of Thailand, Western Pacific ( Fig. 1 View FIGURE 1 ).

Remarks. Ancistrosyllis suksani sp. nov. belongs to the group II of Ancistrosyllis characterized by the presence of both a median antenna and two lateral antennae. It resembles A. groenlandica McIntosh, 1878 in having the first dorsal and ventral cirri from chaetiger 1 and the first notopodial hooks from chaetiger 4 ( Table 1 View TABLE 1 ). However, A. suksani sp. nov. differs from A. groenlandica regarding neurochaetae in that it has three different types: 1) short, stout falcates with a subdistal guard approaching distal tips, 2) short bifid limbates, and 3) long non-limbate capillaries with bifid tips. Ancistrosyllis groenlandica has only two types of neurochaetae: short limbates and long non-limbate capillaries with slightly hooked tips ( Imajima 1987; Pettibone 1966). Moreover, the first notopodial hooks of A. suksani sp. nov. always starts from chaetiger 4, whereas in A. groenlandica the first notopodial hooks occurs variably from chaetiger 4 to 6 ( Imajima 1987; Pettibone 1966).

Ansistrosyllis suksani sp. nov. is clearly distinguished from other species of group II of Ancistrosylis species by having the first notopodial hooks at chaetiger 4, and having three types of neurochaetae ( Table 1 View TABLE 1 ).