Akanthinotanais gerlachi Sieg, 1977: 35–38

Kong, Chim Chee, 2024, A synopsis of the Tanaidacea (Crustacea: Peracarida) of Singapore, with a review of tanaidacean diversity in Southeast Asia and the South China Sea, Zootaxa 5451 (1), pp. 1-75 : 40-41

Akanthinotanais gerlachi Sieg, 1977: 35–38 , figs. 21–23.

Material examined. Station SG86: 9 specimens, including 1 male (HAN-EXP-00.0-TAN01); 4 specimens (HAN- EXP-02.5-TAN09); 3 specimens (HAN-EXP-05.0-TAN05); 3 specimens, including 1 female with brood pouch and 1 female with oostegites (HAN-EXP-07.5-TAN08). Station SG88: 2 adults (LAZ-EXP-07.5-TAN06); 1 adult (LAZ-EXP-10.0-TAN02). Station SG89: 2 adults (LAZ-PRO-02.5-TAN02); 2 adults, 1 manca (LAZ-PRO-05.0- TAN04); 2 adults, 1 manca (LAZ-PRO-07.5-TAN10); 1 adult (LAZ-PRO-10.0-TAN09). Station SG91: 4 adults, including 1 female with brood pouch (SEN-PRO-00.0-TAN09); 3 adults (SEN-PRO-02.5-TAN08); 5 adults (SEN- PRO-05.0-TAN10); 4 adults, 1 manca (SEN-PRO-07.5-TAN09).

Remarks. Pseudotanaids can be easily recognised by their greatly reduced pereonite-1 ( Jakiel et al. 2019). Akanthinotanais , which was recently promoted from subgenus to genus rank ( Jakiel et al. 2018), can be differentiated from the other four pseudotanaid genera by the presence of simple instead of blade-like seta on the carpi of pereopods 2 and 3 ( Jakiel et al. 2019). This genus occurs globally from the intertidal to the abyssal zone up to 4910 m depth ( Kudinova-Pasternak 1986; Błażewicz et al. 2021) and is currently represented by 14 species ( Anderson 2023). The type species Akanthinotanais gerlachi was originally described from the Maldives at 5–32 m depth and later recorded from a coral reef in the Gulf of Mexico ( Cházaro-Olvera et al. 2018). Key morphological characters of female of all Akanthinotanais species, except A. rossi Błażewicz, Jakiel, Bamber & Bird 2021 , were tabulated and compared in Tzeng & Hsueh (2021).

The present material from Singapore closely resembles A. gerlachi based on the following shared characters: (1) similar body length; (2) body relatively elongate (i.e., about 5 times longer than wide); (3) pereonite-2 about twice as long as pereonite-1; (4) antennule and cephalothorax of similar length; (5) uropod and pleotelson of similar length; (6) uropod endopod and exopod biarticulated; and (7) uropod exopod slightly shorter than endopod. Until the microstructures on the present material, especially setation on the pereopods, have been examined, it remains uncertain whether they belong to the same species as A. gerlachi . These A. cf. gerlachi specimens from Singapore are very small with body length ranging between 0.7–1.2 mm, making them the smallest tanaidacean species recorded from local waters. This species was found only from intertidal macroalgal turfs on seawalls at Lazarus Island, Pulau Hantu and Sentosa (Pulau Blakang Mati) in the Singapore Strait.