Aricidea (Acmira) anusakdii, 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/5D4169E8-76CF-4638-8E77-70D681CCCF3B
taxon LSID	lsid:zoobank.org:act:5D4169E8-76CF-4638-8E77-70D681CCCF3B
treatment provided by	ZooKeys by Pensoft
scientific name	Aricidea (Acmira) anusakdii
status	sp. nov.

Treatment

Aricidea (Acmira) anusakdii sp. nov. Figures 1A View Figure 1 , 2 View Figure 2 , 3 View Figure 3 , 4 View Figure 4

Material examined.

178 specimens, incomplete, collected from Songkhla Sea, the 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 View Table 2 . Holotype. PSUZC-POL-0047, Sta. S09-24, 21 Mar. 2017. Paratypes. PSUZC-POL-0048 (1 spec.), Sta. S09-6, 4 Mar. 2011; PSUZC-POL-0049 (1 spec.), Sta. S07, 4 Jun. 2014; PSUZC-POL-0050 (1 spec.), Sta. S08, 4 Jun. 2014; PSUZC-POL-0051 (1 spec.), Sta. S10-3, 5 May 2018; PSUZC-POL-0052 (1 spec.), Sta. S07, 22 Sep. 2016; PSUZC-POL-0053 (1 spec., coated with gold for SEM), Sta. S05, 23 Mar. 2012; PSUZC-POL-0054 (2 specs., coated with gold for SEM), Sta. S07, 1 Jun. 2013; PSUZC-POL-0055 (1 spec.), Sta. S08, 14 Oct. 2015; PSUZC-POL-0056 (1 spec., coated with gold for SEM), Sta. S07, 16 Mar. 2016; PSUZC-POL-0058 (1 spec.), Sta. S07, 22 Sep. 2016; PSUZC-POL-0059 (1 spec.), Sta. S10-9, 6 May 2018; PSUZC-POL-0060 (1 spec.), Sta. S09-3, 16 Aug. 2018; AM W.52894 (1 spec.), Sta. S12-3, 9 Feb. 2012; AM W.52895 (1 spec.), Sta. S10-9, 6 May 2018.

Description.

Holotype incomplete with 123 chaetigers, 25 mm long, 1.2 mm wide. Paratypes incomplete with 19-81 chaetigers, 3-13 mm long, 0.51-0.77 mm wide. Body robust, widest anteriorly, dorsoventrally flattened in branchial region (Fig. 2A View Figure 2 ), thinner with cylindrical segments in postbranchial region. Cilia scattered on dorsum along the body. Opaque white in alcohol, with red pigments on the distal and subdistal regions of each branchia (Fig. 2C View Figure 2 ). Prostomium wider than long (0.36 mm wide; 0.26 mm long); anterior margin of prostomium bilobed divided by a shallow notch which dorsally extends to the antenna (Figs 2B View Figure 2 , 4A View Figure 4 ). Two large nuchal grooves on posterior half of prostomium; two ciliated bands on middle prostomium, and a ciliary band border on the inferior mid-region (Figs 2A, B View Figure 2 , 4A View Figure 4 ). Short median antenna, proximally inflated, tapering to a short, blunt end, extending to posterior margin of prostomium (Figs 2A, B View Figure 2 , 4A View Figure 4 ). No eyes. Anterior region of the mouth with a middle lobe and a ciliary row on its middle-anterior margin; posterior buccal lip with 12-14 small longitudinal folds, extending to chaetiger 2 (Figs 2D View Figure 2 , 4B View Figure 4 ).

Two prebranchial chaetigers (Figs 2A, B View Figure 2 , 4A View Figure 4 ). Branchiae start from chaetiger 3, 53 pairs (48-68 pairs in paratypes), bearing numerous long and slender cilia on dorsal midline (Fig. 3A View Figure 3 ); last pair of branchiae shorter. Parapodia large and thick with numerous simple chaetae on noto- and neuropodia. Notopodial postchaetal lobes from chaetiger 1 long, digitiform; cirriform in branchial and postbranchial chaetigers (Fig. 3B, E, F View Figure 3 ). Neuropodial postchaetal lobes shorter than notopodial postchaetal lobes (Fig. 3A, C, F View Figure 3 ).

Modified neurochaetae from chaetiger 37 (from 18-44 in paratypes) to posterior body region; up to nine modified chaetae per fascicle, each a curved spine with blunt shaft surrounded by pubescence (Fig. 2F View Figure 2 ), accompanied by about four simple chaetae on the superior and inferior parts of bundle (Figs 2E View Figure 2 , 4C View Figure 4 ). All other chaetae long and slender capillaries (Figs 2C View Figure 2 , 3D View Figure 3 ); notochaetae longer than neurochaetae (Fig. 3B, C View Figure 3 ). Pygidium unknown.

Reproduction.

Holotype and paratypes of A. (Acmira) anusakdii sp. nov. collected in March, May, June, and August had eggs in their branchial chaetigers. Eggs were also found in October in non-type material.

Etymology.

The species was named in honor of, and to remember, Mr Anusakdi Plathong, Sakanan’s deceased father.

Habitat.

At 10-26.5 m depth, in mud mixed with sand and shells substrates.

Distribution.

Songkhla Sea, Gulf of Thailand, Western Pacific.

Remarks.

Currently, the subgenus Aricidea ( Acmira) Hartley, 1981 is represented by 20 species, including the new species described in the present study. The species that make up this subgenus can be separated by the features of modified neurochaetae (teeth, hood, distal arista, and pubescence), the length and shape of the median antenna, the number of prebranchial chaetigers and the number of branchiae ( Arriaga-Hernández et al. 2013). Previously, only one species, A. ( Acmira ) simonae Laubier & Ramos, 1974, had been described with two prebranchial chaetigers. However, this taxon, originally described from Marseille, France, and common in Mediterranean and Black Sea is entirely different from the new species collected in Thailand. Aricidea ( Acmira ) simonae has smooth neuropodial spines, without pubescence, a very short antenna on the insertion area, bears only 20-32 pairs of branchiae and lacks neuropodial lobes. Aricidea ( Acmira ) anusakdii sp. nov. has curved spines with blunt shafts surrounded by pubescence, an antenna that reaches the posterior margin of the prostomium, has neuropodial lobes and bears a significantly higher number of branchial pairs (48-68 pairs).

Apart from A. ( Acmira ) simonae and A. ( Acmira ) anusakdii sp. nov., eight species of this genus also have smooth modified spines, lacking hood and distal arista, of which only A. ( Acmira ) hirsuta Arriaga-Hernández, Hernández-Alcántara & Solís-Weiss, 2013 from the southern Gulf of Mexico, A. ( Acmira ) horikoshi Imajima, 1973 from Japan and A. ( Acmira ) flava Zhou & Reuscher, 2013 from China, and probably A. ( Acmira ) simplex from South Africa and A. ( Acmira ) strelzovi from Antarctica, have modified spines with distal or subdistal pubescence. However, in these first three species the branchiae initially appear in chaetiger 4, bearing 7-15, 27 and 5 branchial pairs respectively. Clearly, these characteristics distinguish these species from A. ( A. ) anusakdii sp. nov., which, has two prebranchial chaetigers and a much greater number of branchiae (48-68 pairs). Aricidea ( Acmira ) anusakdii sp. nov. can also be separated from A. ( Acmira ) hirsuta because the new species has neuropodial lobes, which are absent in A. ( Acmira ) hirsuta (Table 3 View Table 3 ).

Although the modified spines in A. ( Acmira ) mirifica and A. ( Acmira ) finitima have no hood and do not bear distal or subdistal pubescence, in the first species the spines sometimes bear a short distal arista and in the second they almost always bear arista. Nonetheless, both these species can also be separated from the new species because they have three prebranchial chaetigers, their antennae are longer (reaching chaetiger 1-3 or 6), and they bear fewer branchiae, 12 and 14-27 pairs, respectively.

It is important to note that previously, the presence of lobes and notches on the anterior margin of the prostomium had only been reported in two species: A. ( Acmira ) simonae , which has three lobes in ventral view (Laubier and Ramos 1973) and other differences, smooth neuropodial spines, a very short antenna on the insertion area, bears only 20-32 pairs of branchiae and lacks neuropodial lobes, with the new species has been previously argued; and Aricidea ( Acmira ) trilobata Imajima, 1973, distributed on the continental shelves of Japan and California (Blake, 1996), which also bears three lobes on the anterior edge of the prostomium and the branchiae start from chaetiger 4. However, unlike the new species, this last species also bears three lobes on the anterior edge of the prostomium, the branchiae start from chaetiger 4, the median antenna extending to chaetiger 2 and only bears 18 to 20 branchial pairs.