Bresedium Serène and Soh, 1970

Li, Jheng-Jhang, Shih, Hsi-Te & Ng, Peter K. L., 2020, Paralbunea dayriti, Zoological Studies 59 (16), pp. 1-32 : 2-4

Bresedium Serène and Soh, 1970

Type species: Sesarma edwardsii brevipes De

Man, 1889, by original designation.

Remarks: Bresedium Serène and Soh, 1970 , was established with Sesarma edwardsii brevipes De Man, 1889 , as the type species, and currently contains three taxa, viz. B. brevipes (De Man, 1889) , B. philippinense ( Rathbun, 1914) , and B. sediliense ( Tweedie, 1940) . Members of the genus were characterised by Serène and Soh (1970) as having a carapace broader than long and not prominently inflated, the lateral margin has two epibranchial teeth behind the external orbital tooth, the basal antennular article is at least twice as broad as long, the upper surface of the male palm is without distinct pectinated crest(s), the inner surface of the palm has a prominent vertical row of granules, the ambulatory legs are not elongated, the male telson is deeply inserted into the distal margin of pleonal somite 6, and the distal chitinous part of the G1 is elongate and slender. In many respects, Bresedium closely resembles members of Sesarmops , some species (notably S. impressus ) which also possess a male telson which is inserted into the distal margin of pleonal somite 6 and possess an elongate distal chitinous part of the G1.

Of the three species, B. sediliense is easily distinguished by having the dactylus of the male cheliped as long as the height of palm, and the G1 distal chitinous process is relatively broad, shorter, and bent obliquely, with the tip just visible externally when the telson is closed (cf. Tweedie 1940; present material). On the other hand, B. brevipes has proportionately longer dactylar fingers (longer than height of the palm), with the distal chitinous process of the G1 is slender, relatively longer, straight, in line with the rest of the G1 and the tip is not distinctly bent and completely hidden by the closed telson. Serène and Soh (1970: 399) suspected B. philippinense was a species of Bresedium but could not be sure. Ng et al. (2008: 223) confirmed that it belonged to the genus and treated it as a distinct species. Bresedium brevipes and B. philippinense are very similar and their taxonomy has been unclear, mainly because the type of B. philippinense was only briefly described and has never been figured. The reexamination of the type male of B. philippinense as well as a good series of specimens from the Philippines now shows it is actually a junior synonym of B. brevipes . Bresedium sediliense ( Tweedie, 1940) from Peninsular Malaysia is distinct from the other two species in that the dactylus of the chela is as long as the height of the palm ( Tweedie 1940: 8 b) and the elongate chitinous distal part of the G1 is inserted at an angle to the main shaft ( Tweedie 1940: 8 b). Bresedium brevipes (and B. philippinense ) has the dactylus of the chela longer than the height of the palm ( Figs. 2F , 3G ) and the chitinous distal part of the G1 is proportionately longer and continues in a straight line with the main shaft ( Figs. 5 , 6E–K ). The present paper will only deal with the taxonomy of Bresedium brevipes and B. philippinense as only they are present in Taiwan and the Philippines. The taxonomy of B. sediliense will be discussed in greater depth by CD Schubart and PKL Ng in an ongoing revision of these and other genera.

Figures

Fig. 2. Bresedium brevipes (De Man, 1889), life colouration. A, B, male (20.5 × 17.8 mm) (NCHUZOOL 16318), Gangkou R., Taiwan; C, male (17.9 × 15.5 mm) (ZRC 2019.1646), Gangzai R., Taiwan; D–F, male (25.1 × 21.5 mm) (ZRC 2016.0667), Kawasan, Cebu, Philippines.A, D, overall dorsal view; B, C, ventral view of cephalothorax; E, frontal view of cephalothorax; F, outer view of left chela.

Fig. 3. Bresedium brevipes (De Man, 1889). A, female (15.3 × 13.3 mm) (RMNH D1210), “Sydney”, Australia; B, D, male (25.0 × 21.8 mm, 24.0 × 21.3 mm) (ZRC 2009.0901), Brisbane, Australia; C, E, F, male (16.7 × 14.5 mm) (USNM 45750) (holotype of Sesarma (Sesarma) edwardsi philippinense Rathbun, 1914), Philippines; G, H, male (17.9 × 15.5 mm) (ZRC 2019.1646), Gangzai R., Taiwan; I, female (14.1 × 12.3 mm) (ZRC 2019.1645), Gangzai R., Taiwan.A–C, overall dorsal view; E, dorsal view of carapace; D, F, ventral view of anterior thoracic sternum and pleon; G, I, outer view of left chela; H, dorsal view of left chela.

Fig. 5. Bresedium brevipes (De Man, 1889). A–D, male (22.2 × 19.1 mm) (RMNH D1195), Batjan Island, Indonesia, right G1; E, F, male (21.3 × 18.5 mm) (ZRC), Taiwan, left G1; G, H, male (24.7 × 21.0 mm) (ZRC), Philippines, left G1. A, F, H, dorsal view; B, E, G, ventral view; C, D, distal part of G1. Scale bars = 1.0 mm.

Fig. 6. Bresedium brevipes (De Man, 1889). A–C, B. brevipes; D, Sesarma (Sesarma) edwardsi philippinense, holotype. A, male (22.0 × 19.0 mm) (NCHUZOOL 16324), Taiwan; B, male (22.3 × 18.9 mm) (NCHUZOOL 16318), Taiwan; C, male (19.3 × 17.4 mm) (NCHUZOOL 16319), Taiwan; D, male (16.7 × 14.5 mm) (USNM 45750) (holotype of Sesarma (Sesarma) edwardsi philippinense Rathbun, 1914), Philippines; E, male (20.7 × 17.9) (NCHUZOOL 16322), Taiwan; F–J, males 25.6 × 21.7 mm, 22.6 × 19.3 mm, 25.7 × 21.9 mm, 24.4 × 21.3 mm, 25.1 × 21.5 mm) (ZRC 2016.0667), respectively, Philippines; K, male (24.9 × 21.8) (ZRC 2009.0901), Australia; L, female (16.9 × 14.3 mm) (ZRC 2019.1643), Taiwan; M, ovigerous female (19.7 × 16.8 mm) (ZRC 2019.1667), Philippines. A–D, right side of carapace and P3; E–K, left G1s; L, M, vulvae.