Zeuxo sp.

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 : 43-44

Zeuxo sp. SG#1

( Figs. 24A–D )

Material examined. Station SG86: 9 specimens (HAN-EXP-0.0-TAN02); 3 specimens (HAN-EXP-2.5-TAN08); 6 specimens, including 1 manca (HAN-EXP-5.0-TAN01, HAN-EXP-05.0-TAN07); 4 adults, including 1 male (HAN-EXP-7.5-TAN07 and HAN-EXP-7.5-TAN09); 2 mancae (HAN-EXP-10.0-TAN03). Station SG87: 3 males, 1 female with brood pouch, 6 non-ovigerous females, 3 mancae (HAN-PRO-07.5-TAN01, HAN-PRO-07.5-TAN02, HAN-PRO-07.5-TAN03, HAN-PRO-07.5-TAN04, HAN-PRO-07.5-TAN05, HAN-PRO-07.5-TAN06, HAN- PRO-07.5-TAN07, HAN-PRO-07.5-TAN08, HAN-PRO-07.5-TAN09). Station SG88: 2 adults (LAZ-EXP-00.0- TAN01); 2 males, 2 ovigerous females, 36 non-ovigerous females, 36 mancae, 8 incomplete specimens (LAZ-EXP-02.5-TAN01, LAZ-EXP-02.5-TAN02, LAZ-EXP-02.5-TAN03, LAZ-EXP-02.5-TAN04, LAZ-EXP-02.5-TAN05); 8 non-ovigerous females, 4 incomplete specimens (LAZ-EXP-05.0-TAN01, LAZ-EXP-05.0-TAN02, LAZ-EXP-05.0-TAN03); 1 non-ovigerous female (LAZ-EXP-10.0-TAN01). SG89: 6 non-ovigerous females (LAZ-PRO-10.0-TAN08). Station SG90: 5 males, 3 ovigerous females, 1 female with oostegites, 32 non-ovigerous females, 18 mancae (SEN-EXP-0.0-TAN01, SEN-EXP-0.0-TAN02, SEN-EXP-0.0-TAN03, SEN-EXP-0.0-TAN04, SEN-EXP-0.0-TAN05, SEN-EXP-0.0-TAN06, SEN-EXP-0.0-TAN07, SEN-EXP-0.0-TAN08, SEN-EXP-0.0-TAN09, SEN- EXP-0.0-TAN10); 5 males, 1 ovigerous female, 1 female with oostegites, 18 non-ovigerous females, 11 mancae (SEN-EXP-2.5-TAN01, SEN-EXP-2.5-TAN02, SEN-EXP-2.5-TAN03, SEN-EXP-2.5-TAN04, SEN-EXP-2.5- TAN05, SEN-EXP-2.5-TAN06); 9 males, 6 ovigerous females, 45 non-ovigerous females, 19 mancae (SEN-EXP-5.0-TAN02, SEN-EXP-5.0-TAN03, SEN-EXP-5.0-TAN04, SEN-EXP-5.0-TAN05, SEN-EXP-5.0-TAN06, SEN- EXP-5.0-TAN07, SEN-EXP-5.0-TAN08); 3 males, 5 ovigerous females, 71 non-ovigerous females, 4 mancae, 13 incomplete specimens (SEN-EXP-07.5-TAN01, SEN-EXP-07.5-TAN02, SEN-EXP-07.5-TAN03, SEN-EXP-07.5- TAN04, SEN-EXP-07.5-TAN05, SEN-EXP-07.5-TAN06); 22 males, 20 ovigerous females, 123 non-ovigerous females, 40 mancae, 12 incomplete specimens (SEN-EXP-10.0-TAN01, SEN-EXP-10.0-TAN02, SEN-EXP-10.0-TAN03, SEN-EXP-10.0-TAN04, SEN-EXP-10.0-TAN05, SEN-EXP-10.0-TAN06, SEN-EXP-10.0-TAN07). Station SG91: 3 adults and 4 mancae (SEN-PRO-0.0-TAN08); 2 ovigerous females, 14 non-ovigerous females, 7 mancae (SEN-PRO-05.0-TAN01, SEN-PRO-05.0-TAN02, SEN-PRO-05.0-TAN03, SEN-PRO-05.0-TAN04); 1 male, 1 ovigerous female, 6 non-ovigerous females (SEN-PRO-07.5-TAN01, SEN-PRO-07.5-TAN02, SEN-PRO-07.5-TAN03, SEN-PRO-07.5-TAN04); 11 specimens, including 1 ovigerous female (SEN-PRO-10.0-TAN08, SEN-PRO-10.0-TAN09).

Remarks. Within the genus Zeuxo , at least eight species [i.e., Z. insularis ( Miller, 1940) , Z. zorro Bamber & Bird, 1997 , Z. amiti Bamber, 2008c , Z. russi Edgar, 2008 , Z. andaminimus Bamber & Chatterjee, 2010 , Z. kermadecensis Bird, 2015 , Z. shitipingensis Tzeng & Hsueh, 2015 , Z. molybi Okamoto & Kakui, 2022 ] have a pigmented band between their eyes ( Miller 1940; Bamber & Bird 1997; Bamber 2008c; Edgar 2008; Bamber & Chatterjee 2010; Bird 2015; Tzeng & Hsueh 2015; Okamoto & Kakui 2022). The present material is most similar to Z. molybi as both species have a densely pigmented band between the eyes and along the posterior margin of each pereonites as well as sparsely mottled patterns on the posterior half of the cephalothorax and on the pleon ( Figs. 24B–D ). Both species also possess four articles on the uropod endopod, although this character may exhibit large intraspecific variation depending on overall body size. The most important character distinguishing Zeuxo sp. SG#1 and Z. molybi is the lack of pigmentation on the antennules of the present material ( Figs. 24A–D ), a condition that was found to be very consistent in the large number of specimens examined. Based on this subtle but significant difference on the antennules and the environmental difference between tropical Singapore and the type locality of Z. molybi in the colder waters of Chiba, Japan, it is likely that Zeuxo sp. SG#1 is an undescribed species. Zeuxo sp. SG#1 was found only from intertidal macroalgal turfs on seawalls at Lazarus Island, Pulau Hantu and Sentosa (Pulau Blakang Mati) in the Singapore Strait.

Figures

FIGURE 24. Zeuxo sp. SG#1 Singapore: (A) mancae II, dorsal (SEN-PRO-00.0-TAN08) and lateral (SEN-EXP-02.5-TAN06) habitus, respectively; (B) female with oostegites, SEN-EXP-02.5-TAN03, dorsal and lateral habitus, respectively; (C) ovigerous females, dorsal (SEN-EXP-05.0-TAN02) and lateral (SEN-EXP-00.0-TAN02) habitus, respectively; (D) adult males, dorsal (SEN-EXP-02.5-TAN01) and lateral (SEN-EXP-00.0-TAN04) habitus, respectively. Scale bar: A = 500 µm; B–D = 1 mm.