Macrobrachium placidulum ( De Man, 1892 )

Shokita, Yixiong Cai Shigemitsu, 2006, Report On A Collection Of Freshwater Shrimps (Crustacea: Decapoda: Caridea) From The Philippines, With Descriptions Of Four New Species, Raffles Bulletin of Zoology 54 (2), pp. 245-270 : 264

Macrobrachium placidulum ( De Man, 1892)

Palaemon (Macrobrachium) placidulus De Man, 1892: 489 , pl.28: fig. 48 [type localities: Celebes (Sulawesi), Pulau Selajar , Flores, and Timor].

Macrobrachium placidulum – Holthuis, 1950: 253, fig. 51c; Chace & Bruce, 1993: 35, fig. 14.

Macrobrachium placidum – Shokita, 1979: 275.

Macrobrachium horstii – Hwang & Yu, 1982: 164, fig. 5.

Macrobrachium cf. horstii – Shy & Yu, 1998: 30.

Material examined. – 1 male, cl 14 mm, UR, Manuanga River, Cebu Island, Phippines , 29 Jul.1985 ; 2 males, cl 12.8 -14 mm, 1 ovig. female, cl 12.5 mm, UR, Aninoan River, Mindoro Island, Philipines , 25 Aug.1985 ; 3 males, cl 11.5-13 mm, UR, Iraan River , Philippines, no date .

Remarks. – Macrobrachium placidulum is related to M. lepidactyloides and M. placidum by having a distinct gap between fingers of the minor second pereiopod, and the gap is filled with stiff setae. It, however, could be easily separated from the latter two species by the less inflated palm and the shorter fingers which are always distinctly shorter than the palm. Shokita (1979) recorded Macrobrachium placidum from Okinawa, Ryukyu Island. Re-examination of his specimens shows that it is M. placidulum instead. M. placidum , which has only been found from west Sumatra and Java, has a more inflated palm in the major male second pereiopod and the fingers are longer. Hwang & Yu (1982) and Shy & Yu (1998) assigned some Taiwanese specimens to M. horstii . According the figures that they provides and the re-examination of the reported material, there is a distinct gap filled with stiff setae between fingers of the male miner second pereiopod, a character does not fit the description of M. horstii . It is in fact, M. placidulum instead.

Distribution. – Philippines, Taiwan, Ryukyus.