Jose Christopher E. Mendoza

Rapid evolution of troglomorphic characters suggests selection rather than neutral mutation as a driver of eye reduction in cave crabs

This study asked whether reductive traits in cave organisms evolve at a slower pace (suggesting neutral evolution under relaxed selection) than constructive changes, which are likely to evolve under directional selection. We investigated 11 subterranean and seven surface populations of Sundathelphusa freshwater crabs on Bohol Island, Philippines, and examined constructive traits associated with improved food finding in darkness (increased leg and setae length) and reductive traits (reduced cornea size and eyestalk length). All changes occurred rapidly, given that the age of the most recent common ancestor was estimated to be 722–271 ka based on three mitochondrial markers. In order to quantify the speed of character change, we correlated the degree of morphological change with genetic distances between surface and subterranean individuals. The temporal pattern of character change following the transition to subterranean life was indistinguishable for constructive and reductive traits, characterized by an immediate onset and rapid evolutionary change. We propose that the evolution of these reductive traits—just like constructive traits—is most likely driven by strong directional selection.

MACROPHTHALMUS (EUPLAX) H. MILNE EDWARDS, 1852, A VALID SUBGENUS OF OCYPODOID CRAB (DECAPODA: BRACHYURA: MACROPHTHALMIDAE), WITH DESCRIPTION OF A NEW SPECIES FROM THE PHILIPPINES

Abstract The taxonomy of the rare Macrophthalmus leptophthalmus (H. Milne Edwards, 1852) is reviewed. On the basis of distinctive features of the carapace, eyes, and epistome, M. leptophthalmus is assigned to the subgenus, Euplax H. Milne Edwards, 1852, new status, a taxon that has been incorrectly synonymised under Macrophthalmus (Venitus) Barnes, 1967. A related species, Macrophthalmus (Euplax) dagohoyi, new species, is described from subtidal mangroves in Bohol, central Philippines. Macrophthalmus (Euplax) dagohoyi can easily be distinguished from M. (Euplax) leptophthalmus by different carapace, cheliped, walking leg and sternal characters. A key to the genera and subgenera of Macrophthalmidae is also presented.

Descriptions of five new species of false spider crabs (Decapoda: Brachyura: Hymenosomatidae) from the Philippines

Abstract Five new species of the family Hymenosomatidae are described from the central Philippines. Amarinus abatan, new species, is compared with its congeners, especially with the morphologically similar A. crenulatus, A. wolterecki, and A. pumilus, but the new species is distinguished by differences in the rostrum, carapace, third maxillipeds, ambulatory legs, and male pleopods. Two new species related to Elamena truncata differ from that species and from each other by the shape of the carapace and the relative lengths of the ambulatory legs. Two new Neorhynchoplax species are similarly differentiated from congeners and each other by the differing shapes of their rostrum, carapace, and ambulatory legs.

New records of coral-associated crabs (Decapoda: Brachyura: Carpilioidea, Trapezoidea) from Easter Island

A review is made of those brachyurans that are symbiotic or otherwise associated with scleractinian corals on Easter Island, southeastern Pacific Ocean. A total of seven species is reported, including three species from two families not previously known from the island. Earlier records of Trapezia are analyzed and, although as many as six species have been previously reported, we conclude that only three species are known to occur on the island with certainty.

A new species of Isolapotamon Bott, 1968 (Decapoda, Brachyura, Potamidae) from Mindanao, with notes on the Philippine Isolapotamon species

The genus Isolapotamon Bott, 1968 (Brachyura: Potamidae) is represented in the Philippines by four poorly known species, all found on the large southern island of Mindanao. Isolapotamon mindanaoense (Rathbun, 1904) is re-described based on newly collected material, and an update on its distribution is also provided. A fifth species, I. maranao sp. nov., is here described from the northwestern region of Mindanao. It differs from its congeners primarily in the morphology of the male first pleopods, although minor external differences are also observed in the form of the carapace, ambulatory legs and of the male thoracic sternum and abdomen. A key to the Philippine species of Isolapotamon Bott, 1968, is provided.

A new species of false spider crab of the genus Elamena H. Milne Edwards, 1837 (Crustacea: Decapoda: Brachyura: Hymenosomatidae), from Davao Gulf, Philippines

A new species of hymenosomatid crab of the genus Elamena H. Milne Edwards, 1837, is described from the island of Samal, in the Davao Gulf, Mindanao, southern Philippines. Elamena samalensis sp. nov. belongs to the Elamena truncata species-group and is most similar to E. simplidenta Ng & Chuang, 1996, in the general form of the carapace and in the presence of only one subdistal tooth on the ambulatory dactyli. It can be distinguished from this species, however, by its more projecting rostrum, relatively longer and more slender ambulatory legs, and by the pointed apex of the female pleotelson.

Harryplax severus, a new genus and species of an unusual coral rubble-inhabiting crab from Guam (Crustacea, Brachyura, Christmaplacidae)

Abstract Harryplax severus, a new genus and species of coral rubble-dwelling pseudozioid crab is described from the island of Guam in the western Pacific Ocean. The unusual morphological features of its carapace, thoracic sternum, eyes, antennules, pereopods and gonopods place it in the family Christmaplacidae Naruse & Ng, 2014. A suite of characters on the cephalothorax, pleon and appendages distinguishes Harryplax severus gen. & sp. n. from the previously sole representative of the family, Christmaplax mirabilis Naruse & Ng, 2014, described from Christmas Island in the eastern Indian Ocean. This represents the first record of Christmaplacidae in the Pacific Ocean. With the discovery of a second genus, a revised diagnosis for Christmaplacidae is provided.

Sundathelphusa miguelito, a new species of freshwater crab from the southern Philippines (Brachyura, Gecarcinucidae)

A new species of the freshwater crab genus Sundathelphusa Bott, 1969 (Gecarcinucidae) is described from the island of Mindanao in the southern Philippines. The Philippine Islands host the greatest species diversity of this genus, although only four species were previously known from Mindanao. The new species is most similar to S. mistio (Rathbun, 1904) and S. montanoanus (Rathbun, 1904) in the general carapace outline and leg proportions, but it can be distinguished by features of the carapace, thoracic sternum and gonopods. With this discovery, there are now 29 species of Sundathelphusa known from the Philippines.

A new genus and species of deep-water xanthid crab (Decapoda, Brachyura, Xanthidae) from the Philippines

A new genus and species of deep-water xanthid crab is described from the Philippines. Takedax gabrielae gen. et sp. nov. resembles Medaeops Guinot, 1967, in the cristate anterior margins of the ambulatory meri. It is also similar to Monodaeus Guinot, 1967, in the long cheliped fingers, the shape of the ambulatory legs, and the form of the merus of the third maxilliped. Takedax gen. nov. is separated from both known genera by a suite of characters related to the carapace, epistome, pereiopods, male thoracic sternum, and male abdomen.