Aricidea (Aricidea) thammapinanae, Plathong & Hernández-Alcántara & Harris & Plathong, 2020

Plathong, Jintana, Hernandez-Alcantara, Pablo, Harris, Leslie & Plathong, Sakanan, 2020, Description of two new species of Paraonidae (Annelida) from the Gulf of Thailand, Western Pacific, ZooKeys 951, pp. 1-20 : 1

publication ID	https://dx.doi.org/10.3897/zookeys.951.51686
publication LSID	lsid:zoobank.org:pub:923C9D0D-E386-4AB8-BFFD-2022949D1564
persistent identifier	https://treatment.plazi.org/id/6B8798D3-662C-4097-8DC9-83A5640E332C
taxon LSID	lsid:zoobank.org:act:6B8798D3-662C-4097-8DC9-83A5640E332C
treatment provided by	ZooKeys by Pensoft
scientific name	Aricidea (Aricidea) thammapinanae
status	sp. nov.

Treatment

Aricidea (Aricidea) thammapinanae sp. nov. Figures 1B View Figure 1 , 5 View Figure 5 , 6 View Figure 6 , 7 View Figure 7 , 8 View Figure 8 , 9 View Figure 9

Material examined.

13 specimens, collected from Songkhla Sea, Gulf of Thailand, 24 m depth. Coll. MEM (Marine Ecosearch Management Co., Ltd.), in mud mixed with sand and shells. Details of geographic positions and environmental characteristics of sampling stations are in Table 2 View Table 2 . Holotype. PSUZC-POL-00021 (1 spec., complete), Sta. S21, 16 Aug. 2018. Paratypes. PSUZC-POL-00022 (1 spec.), Sta. S21, 21 Aug. 2012; PSUZC-POL-00023, (1 spec., coated with gold for SEM), Sta. S21, 15 Mar. 2013; PSUZC-POL-00024 (1 spec.), Sta. S21, 3 Jun. 2013; PSUZC-POL-00025 (1 spec.), 23 Mar. 2017; PSUZC-POL-00026, (1 spec., coated with gold for SEM), Sta. S21, 23 Sep. 2017; PSUZC-POL-0027, (1 spec., coated with gold for SEM), Sta. S16, 21 Aug. 2012; PSUZC-POL-0062 (2 specs.), Sta. S21, 16 Aug. 2018; AM W.52904 (1 spec.), Sta. S50, 27 Feb. 2015.

Description.

Holotype complete with approximately 50 chaetigers (posterior region coiled, difficult to count segments), 5.47 mm long, 0.3 mm wide (Fig. 5A-C View Figure 5 ); two complete paratypes with 29 and 45 chaetigers, others incomplete with 21 to 32 chaetigers, 1.8-4.5 mm long and 0.01-0.23 mm wide. Body small, new preserved specimens reddish-orange in prebranchial and branchial regions (Fig. 5A View Figure 5 ); dorsal ciliary bands present on the prebranchial and branchial chaetigers. Prostomium conical, distally rounded, longer than wide; one pair of small black or brown eyes present; two pairs of long ciliary bands, one pair located above nuchal grooves and other at lateral margins of prostomium. Median antenna biarticulated, basal portion clavate, distal portion triangular, ciliated on distal end; basal portion of median antenna about two times longer than distal portion, extending to chaetiger 1 (Figs 6B, D View Figure 6 , 9A View Figure 9 ). Nuchal organs as pair of oblique, deep slits. Posterior buccal lip with six longitudinal folds, extending to chaetiger 1, with one pair of ciliary patches above the buccal region (Figs 6C View Figure 6 , 9B View Figure 9 ). Numerous small filaments along body, and thin papillae present on the body (Fig. 6F View Figure 6 ) and notopodial pores (Fig. 7F View Figure 7 ).

Postbranchial region presents numerous dark red or brown pigmented papillae adjacent to neurochaetal rami on all chaetigers (Fig. 5A, C View Figure 5 ). First two notopodial postchaetal lobes very short, usually hidden by chaetae; those of chaetiger 3 much larger, broadly triangular, with a short, rounded distal protuberance. Notopodial postchaetal lobes digitate on branchial segments, filiform on following segments. Neuropodial postchaetal lobes small, inconspicuous (Figs 6B, E View Figure 6 , 9A View Figure 9 ).

Three prebranchial chaetigers; 8 pairs of branchiae (4 to 8 in paratypes) present on chaetigers 4 to 11, robust, conical, with lateral margins markedly ciliated; last pair smaller. Anterior noto- and neurochaetae fringed with capillaries (Fig. 6A, B View Figure 6 ); notochaetae longer than neurochaetae, decreasing in number from anterior to posterior segments. Modified neurochaetae bidentate (Fig. 8B, E, F View Figure 8 ), beginning in chaetiger 17 (10-19 in paratypes), superior tooth small, inferior tooth large, surrounded by pubescence on distal region of shaft, with very long subterminal spine arising from concave side of shaft; spine almost twice as long as shaft, with pubescence throughout, starting from chaetiger 10-19. Posterior neurochaetae arranged in two rows, first row with both simple and modified bidentate chaetae, and second row with only simple chaetae; up to 5 bidentate chaetae per fascicle per row, accompanied by 10-12 long capillary chaetae (Fig. 8B View Figure 8 ). Pygidium with three anal cirri, two lateral and one triangular, short mid-ventral (Fig. 8E View Figure 8 ).

Reproduction.

Holotype and paratypes of Aricidea ( Aricidea ) thammapinanae sp. nov. collected in March, August, and September had eggs in the coelomic cavities of postbranchial chaetigers.

Etymology.

The species epithet thammapinanae , is after the family name of Ms Vorramaz Thammapinan. This species is named in honor of her initiation, coordination, and assistance to the research project in Songkhla Sea.

Habitat.

At 20-24 m depth, mud with sand and shells.

Distribution.

Songkhla Sea, Gulf of Thailand, Western Pacific.

Remarks.

This is a small species of the subgenus Aricidea ( Aricidea ) having a maximum length of 5.47 mm (holotype) and with only 4-8 pairs of branchiae. The presence of eggs (Fig. 7C View Figure 7 ) in individuals collected during several sampling months implies that the small size of this new taxon is a specific characteristic. The presence of bidentate chaetae is unusual in species belonging to the subgenus Aricidea ( Aricidea) . Until now, 15 species have been described in this subgenus but only Aricidea ( Aricidea ) capensis Day, 1961 from South Africa ( Day 1961) has bidentate modified chaetae (Table 1 View Table 1 ). However, the species presents clearly different characteristics from those observed in A. ( Aricidea ) thammapinanae sp. nov., since the bidentate modified chaetae of A. ( Aricidea ) capensis Day, 1961 are smooth, without pubescence along the shaft or on the subterminal spine. Besides the antenna, extending to chaetiger 2, is faintly annulated, eyes are lacking, 14 branchial pairs are present, and all prebranchial notopodial lobes are small and slender (Table 1 View Table 1 ). In contrast, the proposed new species has bidentate modified neurochaetae with pubescence on the distal shaft and along the subterminal spine, a biarticulated antenna that extends to chaetiger 1, and a pair of eyes. Only 4-8 branchial pairs are present, and on chaetiger 3, distinctive broad triangular notopodial lobes with short distal protuberances.