Pletholophus guangzhouensis Dai, Chen, Huang & Wu, 2024

Dai, Yu-Ting, Chen, Zhong-Guang, Hu, Cheng-Lin, Ouyang, Shan, Huang, Xiao-Chen & Wu, Xiao-Ping, 2024, Description of a new freshwater mussel species of Pletholophus, Simpson, 1900 (Bivalvia, Unionidae) from Guangdong, China, Zoosystematics and Evolution 100 (4), pp. 1191-1200 : 1191-1200

Pletholophus guangzhouensis Dai, Chen, Huang & Wu sp. nov.

Fig. 2

Material examined.

Holotype China • ♀; Guangdong, Guangzhou City, Conghua District, Liuxi River ; 23 ° 32 ' 02 " N, 113 ° 35 ' 03 " E; 9 January 2021; leg. local people; ex. Y. T. Dai & L. Guo; 24_NCU_XPWU_PGU 01 . Paratypes China • 9 shells; same collection data as for the holotype; specimen vouchers are shown in Table 4 .

Diagnosis.

Periostracum greenish-yellow in young individuals, darkish-brown in old individuals; with fine and dense growth lines and two faint ridges on the posterior dorsal; periostracum often painted with a few elegant, feebly rays. Hinge undeveloped. Beak cavities shallow, open. In both valves, only one peudocardinal and lateral tooth. Peudocardinal teeth reduced to mere raised threads, lateral teeth long and narrow. Nacre bluish-white, iridescent. Glochidia hooked, subtriangular in shape, medium size, shell length less than shell height. The surface of glochidia have deep and dense small holes.

Shell description.

Shell medium-sized, not inflated, thin but strong. Length 34.47–51.19 mm, width 6.55–16.21 mm, height 22.86–33.76 mm (Table 4 ). Shell ovoid, anterior rounded, short, posterior long and wide, slightly obtuse angle, posterior ridge developed. Umbo not prominent, compressed, as high as dorsal margin, located at 1 / 4 of the dorsal margin, and often eroded. Dorsal margin straight, rear end curved down-wards, with a low wing behind; ventral margin weakly curved. Periostracum greenish-yellow in young individuals, darkish-brown in old individuals; with fine and dense growth lines and two faint ridges on the posterior dorsal; periostracum often painted with a few elegant, feebly rays. Lines arranged in irregular concentric circles. Hinge undeveloped. Beak cavities shallow, open. In both valves, only one peudocardinal and lateral tooth. Peudocardinal teeth reduced to mere raised threads, and lateral teeth long and narrow. Mantle attachment scars on the edge of shells obvious. Both anterior adductor muscle scars and posterior adductor muscle scars shallow, irregularly crescent-shaped. Nacre bluish-white, iridescent.

Glochidia morphology description.

Glochidial shells typically anodontin hooked shells and subtriangular in shape, with the ventral angle slightly protruding dorsally. Medium size, length 0.226 ± 0.003 mm, height 0.247 ± 0.015, shell length less than shell height. The ventral angle of each glochidia valve with an anchor-shaped styliform hook. The hook covered by lanceolate macrospines arranged in 2–3 diagonal rows near the ventral terminus and reduced to a single row distally. Microspines and micropoints cover the entire ventral terminus and less than one-third of the hook lateral lobes. The fossae on the shell surface deep and dense, with distinct small holes.

Etymology.

The name of this species is derived from Guangzhou City, in which its type locality is located. For the common name of Pletholophus guangzhouensis , we recommend “ Guangzhou micro tooth mussel ” (English) and “ Guang Zhou Wei Chi Bang ” (广州微齿蚌) (Chinese).

Distribution.

The species is endemic to the Liuxi River, located in Conghua District, Guangzhou City, Guangdong Province.

Figures

Figure 2. The shell morphology of Pletholophus guangzhouensis sp. nov. A. holotype; B – J. paratypes.