ABSTRACT
Talitrids are a highly diverse group of amphipod crustaceans that have colonized various terrestrial habitats. Three genera have successfully adapted to cave habitats on islands in the Pacific and Atlantic Oceans. However, the evolutionary origin of the Pacific troglobitic talitrids has remained unknown. We estimate the phylogenetic position of the troglobitic Minamitalitrus zoltani, which inhabits limestone caves on Minamidaito Island in the Northwestern Pacific, on the basis of the traditional multi-locus dataset. For the analyzed talitrids, we also reconstruct ancestral states of the maxilliped palp and male gnathopod 2. Our results indicate that Minamitalitrus zoltani is sister to the epigean Nipponorchestia curvatus with a deep divergence. Nipponorchestia curvatus inhabits coastal habitats in Japan, but is not indigenous to Minamidaito Island. A previous study estimated that the Atlantic troglobitic species had invaded subterranean habitats multiple times, but we provide new insight into the troglobisation history in talitrids. We also recover secondary shifts of character states of the maxilliped palp and male gnathopod 2 within the lineage composed of Minamitalitrus and its phylogenetically close genera. Our findings highlight the need for the genus-level reclassification of these genera; we split Nipponorchestia into two genera, establishing a new genus for Nipponorchestia nudiramus.
Subject(s)
Amphipoda/classification , Caves , Phylogeny , Animals , Bayes Theorem , Ecosystem , Evolution, Molecular , Japan , MaleABSTRACT
An independently derived, blind, cave-dwelling amphipod, Minamitalitrus zoltani gen. nov., sp. nov. is described from the Hoshino-do cave on the island on Minami-Daito jima, Okinawa, Japan. This genus belongs to the Talitrus group of 15 genera and is the first record of the group from Japan. Several characters support the new genus, particularly the reduced biramous pleopods.
Subject(s)
Amphipoda/anatomy & histology , Amphipoda/classification , Caves , Animals , Female , Japan , Male , Species SpecificityABSTRACT
The genus Jesogammarus contains 16 species in two subgenera, Jesogammarus and Annanogammarus. To examine relationships among species in the genus, a molecular phylogenetic study including eight species of the former subgenus and four of the latter was conducted using partial DNA sequences of the mitochondrial COI and 12S rRNA genes. MP, NJ, and ML trees based on the combined COI and 12S data indicated monophyly of the subgenus Annanogammarus, though the monophyly of Jesogammarus was left unresolved. Consistent with few morphological differences, Jesogammarus (A.) naritai and J. (A.) suwaensis showed low genetic differentiation and did not show reciprocal monophyly, which suggests a close affinity of these taxa.
Subject(s)
Amphipoda/classification , Amphipoda/genetics , DNA, Mitochondrial/chemistry , Electron Transport Complex IV/genetics , Phylogeny , RNA, Ribosomal/genetics , Animals , Base Sequence , DNA Primers , Molecular Sequence Data , Polymerase Chain Reaction , Sequence AlignmentABSTRACT
-A new species of anisogammarid amphipod, Jesogammarus (Jesogammarus) mikadoi sp. nov., is described from freshwater habitats in northern Honshu, Japan. The species is distinguished from its congeners by having dorsal setae on pereonites 5-7 and pleonites 1-3.
Subject(s)
Amphipoda/anatomy & histology , Amphipoda/classification , Ecosystem , Animals , Biological Evolution , Fresh Water , Japan , Species SpecificityABSTRACT
Two new anisogammarid species belonging to the genus Jesogammarus were obtained from freshwater habitats from northern Japan. They are Jesogammarus (J.) fujinoi sp. nov. and Jesogammarus (J.) shonaiensis sp. nov. The former new species is diagnosed by the pleonites without spine and the telson without distolateral spine. The other new species differs from the congeneric species in having many dorsal spines on pleonites 1-3.
Subject(s)
Crustacea/anatomy & histology , Crustacea/classification , Fresh Water/parasitology , Animals , Female , Japan , Male , Sex Characteristics , Species SpecificityABSTRACT
Three new species of the genus Gammarus are described from Lijiang, Yunnan Province, South China. Gammarus elevatus sp. nov. is characterized by mid-dorsal keel on pleonites 1-3 and compressed elevation on urosomites 1-2; G. denticulatus sp. nov. by many small spinules and setae on pleonites 1-3; G. stagnarius sp. nov. by lack of calceoli on antenna 2 and shorter inner ramus of uropod 3. These amphipods are compared with other known Gammarus species from China.
