Ptychognathus altimanus ( Rathbun, 1914 )

Lagare, Nickel Jean S., Mapi-Ot, Emmarie F., Molina, Ziljih S., Neri, Jemateo B., Nuñeza, Olga M. & Mendoza, Jose Christopher E., 2020, On a collection of freshwater and estuarine crabs (Crustacea: Brachyura) from Mindanao Island, the Philippines, Zootaxa 4868 (3), pp. 301-330 : 314-315

Ptychognathus altimanus ( Rathbun, 1914)

Fig. 5A

Varuna altimana Rathbun 1914: 70 .— Tesch 1918a: 88, pl. 4 fig. 5.— Estampador 1937: 539.

Material examined. 21 males, 12.2 by 18.9 mm—21.1 by 19.9 mm, 2 females, 15.8 by 15.3 mm, 13.1 by 12.9 mm, ( ZRC; NJL161014–36 ) Tagoloan River, Brgy. Poblacion, Tagoloan town , Misamis Oriental prov., coll. N.J. Lagare, 24 & 25 Sep. 2016 ; 1 male, 24.6 by 21.5 mm ( ZRC; NJL182401 ), Brgy. La Union, San Isidro town , Davao Oriental prov., coll. N.J. Lagare, 21–23 Sep. 2018 .

Remarks. Varuna altimana was described by Rathbun (1914) based on a single male specimen collected from a river in Point Jamelo (= Hamilo Point), on the western coast of Batangas Province, Luzon I., Philippines. This species was subsequently transferred to the genus Ptychognathus by Tesch (1918a), and has also been recorded from Indonesia ( Ambon & Nias), southern Japan (Ryukyu Is. & Wakayama Prefecture, Honshu I.), and Taiwan ( Tesch 1918a; Serène & Moosa 1971; Minei 1972; Nomoto et al. 1999; Kishino & Wada 2001; Naruse et al. 2005). In the Philippines, P. altimanus has been recorded by Estampador (1937) from other localities in Luzon I. (Ilocos Norte, Ilocos Sur), as well as in Mindoro I. (Puerto Galera), Panay I. (Dumangas), Negros I. (Dumaguete), and Jolo I. (Paticul).

This species may be easily confused with another co-occurring and far more common species, Varuna litterata (see below), and Naruse et al. (2005) provided the distinguishing characters to separate the two. Nevertheless, adult P. altimanus (especially males) is most readily distinguished from V. litterata by the relatively much wider exopod of the third maxilliped, which can be as wide as or wider than the ischium ( Naruse et al. 2005: fig. 1B). The present material from Mindanao was collected along the banks of rivers with brackish water, being quite common in the Tagoloan River.

New Mindanao record.

Figures

FIGURE 5. Colour photos of recently preserved crabs (dorsal habitus). A, Ptychognathus altimanus (Rathbun, 1914), male 21.1 by 19.9 mm (ZRC), Tagoloan, Misamis Oriental; B, Ptychognathus pusillus Heller, 1865, male, 13.1 by 10.7 mm (ZRC), Tagoloan, Misamis Oriental; C, Ptychognathus riedellii (A. Milne-Edwards, 1868), male, 28.9 by 25.0 mm (ZRC), Oroquieta, Misamis Occidental; D, Pyxidognathus granulosus A. Milne-Edwards, 1879, female, 15.4 by 17.3 mm (ZRC), Maigo, Lanao del Norte; E, Utica gracilipes Adams & White, 1848, male, 24.2 by 22.8 mm (ZRC), Iligan, Lanao del Norte; F, Varuna litterata (Fabricius, 1798), male, 42.1 by 37.5 mm (ZRC), Dapitan, Zamboanga del Norte.G, Austruca perplexa (H. Milne Edwards, 1852), male, 13.9 by 10.6 mm (ZRC), Tagoloan, Misamis Oriental; H, Ocypode ceratophthalmus (Pallas, 1772), male, 30.8 by 27.8 mm (ZRC), Manukan, Zamboanga del Norte. Scale bars: 10 mm.