Mendamanus ailurostoma Bamber, 1999

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 : 15-17

Mendamanus ailurostoma Bamber, 1999

( Figs. 4A–G )

Mendamanus ailurostoma Bamber 1999: 176–181 , figs. 5–7.

Material examined. Station SG22: 2 males (CR1209-P02-03), 3 December 2009; 2 non-ovigerous females and 2 males (CR0511-P02-01-04), 9 May 2011; 1 damaged specimen (CR1211-P02-03), 7 December 2011; 1 non-ovigerous female (CR0112-P02-02-02), 20 January 2012; 1 damaged specimen (CR0512-P02-01-01), 1 non-ovigerous female (CR0512-P02-02) and 1 ovigerous female and two males (CR0512-P02-03), 23 May 2012; 1 non-ovigerous female and 1 male (CR1113-P02-03-02), 13 November 2013; 2 males (CR0514-P02-03-02), 7 May 2014 ; 1 damaged specimen (CR1114-P02-02-01) and 1 male (CR1114-P02-03-02), 11 November 2014; 3 damaged specimens (CR1115-P02-02-01) and 1 non-ovigerous female (CR1115-P02-03-02), 2 November 2015; 1 male (CR1016-P02-01) and 2 ovigerous females (CR1016-P02-02-03), 5 October 2016; 4 damaged specimens (CR1117-P02-01-02) and 2 damaged specimens (CR1117-P02-02-02), 8 November 2017; 1 non-ovigerous female (CR0518-P02-01), 9 May 2018; 1 ovigerous female (CR1118-P02-02), 14 November 2018; 2 ovigerous females (CR1219-P02-01-01), 1 damaged specimen (CR1219-P02-02) and 2 ovigerous females and 1 damaged specimen (CR1219-P02-03-01), 4 December 2019; 1 ovigerous female (CR0820-P02-03), 5 August 2020. Station SG23: 2 ovigerous female (CR1112-P06-01), 6 November 2012. Station SG25: 3 ovigerous females (CR1110-P08-03-01), 16 November 2010; 1 male (CR1115-P08-03-02), 5 November 2015. Station SG26: 1 damaged specimen (CR0515- PS06-02-02), 14 May 2015.

Remarks. Mendamanus Bamber, 1999 is solely represented by M. ailurostoma , which is distinguished from other apseudids by having a reduced fixed finger on the male chela ( Bamber 1999). Mendamanus , together with Atlantapseudes Băcescu, 1978a and Typhlapseudes Beddard, 1886 , are the only genera within Apseudinae that lack an exopod on pereopod-1 but possess an exopod on the cheliped ( Błażewicz-Paszkowycz & Bamber 2007). The absence of a row of lanceolate spines on the propodus of pereopod-5 is also a diagnostic character of this genus ( Bamber et al. 2012). Mendamanus ailurostoma is an uncommon species as it was previously known only from the shallow subtidal (2–60 m) sandy bottoms of Bruneian waters ( Bamber 1999; 2013b; Bamber et al. 2012).

The specimens from Singapore match the description of M. ailurostoma from Brunei ( Bamber 1999) but these specimens, which include males and ovigerous females, possess hyposphenia on pereonites 2–6 ( Figs. 4E–F ), which were not mentioned in the description by Bamber (1999). It is likely that hyposphenia are absent in the Bruneian specimens because these conspicuous structures are unlikely to be overlooked and would have been mentioned if present. It is, however, important to note that hyposphenia is rarely considered a reliable taxonomic character in apseudomorphans as it has been shown to exhibit intraspecific variations ( Jóźwiak & Błażewicz-Paszkowycz 2011). The present material represents the first record of M. ailurostoma outside Brunei and was collected from silty bottoms along the Singapore Strait at 12–54 m depth, which is within the bathymetric range of the records in Brunei. This species is especially abundant at station SG22, which is located at the eastern end of the Singapore Strait ( Fig. 2 ).

Genus Siegius Allsopp, 2017

Bilobatus Sieg 1993: 45 ; Guţu 2002: 42; 2006: 99.

Siegius Allsopp, 2017: 584 .

Figures

FIGURE 2. Sampling stations in the West Johor (red), East Johor (green) and Singapore (blue) Straits, Singapore. Refer to Table 1 for details. This map was modified from nautical chart GSP1 ‘Anchorages and Aids to Navigation’ (Maritime Port Authority of Singapore 2012).

FIGURE 4. Mendamanus ailurostoma Bamber, 1999 from Singapore: (A) non-ovigerous female, dorsal habitus; (B) ovigerous female, lateral habitus; (C) rostrum and pereopod-1 coxal spines (arrows); (D) lateral spines (arrows) on pereonites 3–6; hyposphenia (arrows) on (E) pereonite-2 and (F) pereonite-6; (G) male cheliped with reduced fixed finger (arrow). A, C–D: CR1117-P02-02-02; B, F: CR1016-P02-02-03; E: CR1114-P02-03-02; G: CR1016-P02-01-01. Scale bar:A–B = 1 mm; C = 500 µm; D–G = 200 µm.