A new species of freshwater crab genus Fredius Pretzmann, 1967 (Crustacea: Brachyura: Pseudothelphusidae) from a naturally isolated orographic forest enclave within the semiarid Caatinga in Ceara, northeastern Brazil

Author(s)

Santos, Livanio C. ^{[1, 2]} ; Tavares, Marcos ^[3] ; Silva, Jose R. F. ^[2] ; Cervini, Marcelo ^[4] ; Pinheiro, Allysson P. ^[1] ; Santana, William ^{[1, 5]}

Affiliation

^[1] Univ Reg Cariri, Lab Crustaceos Semiarido LACRUSE, Crato, Ceara - Brazil

^[2] Univ Fed Ceara, Programa Posgrad Ecol & Recursos Nat, Fortaleza, Ceara - Brazil

^[3] Univ Sao Paulo, Museum Zool, Sao Paulo - Brazil

^[4] Univ Estadual Sudoeste Bahia, Dept Ciencias Biol, Jequie, BA - Brazil

^[5] Univ Sagrad Coracao, Lab Systemat Zool LSZ, Bauru, SP - Brazil

• Document type: Journal article
• Source: PeerJ; v. 8, JUN 29 2020.
• Web of Science Citations: 0

Abstract

A new species of freshwater crab, Fredius ibiapaba, is described and illustrated from a mid-altitude forested patch in Ipti (Ibiapaba plateau, Ceara, northeastern Brazil), between 635 to 782 m. The new species can be separated from its congeners by the morphology of its first gonopod: proximal half remarkably swollen, sloping abruptly downwards distally to a nearly right-angular shoulder; mesial lobe much smaller than cephalic spine; cephalic lobe moderately developed; auxiliary lobe lip, delimiting field of apical spines, protruded all the way to distal margin of auxiliary lobe. Comparative 16S rDNA sequencing used to infer the phylogenetic placement of Fredius ibiapaba n. sp. revealed that it is the sister taxon of F. reflexifrons, a species which occurs allopatrically in the Amazon and Atlantic basin's lowlands (<100 m). Fredius ibiapaba n. sp. and F. reflexifrons are highly dependent upon humidity and most probably were once part of an ancestral population living in a wide humid territory. Shrinking humid forests during several dry periods of the Tertiary and Quaternary likely have resulted in the fragmentation of the ancestral humid area and hence of the ancestral crab population. Fredius reflexifrons evolved and spread in a lowland, humid river basin (Amazon and Atlantic basins), whilst F. ibiapaba n. sp. evolved isolated on the top of a humid plateau. The two species are now separated by a vast intervening area occupied by the semiarid Caatinga (AU)

• FAPESP's process: 13/01201-0 - Biodiversity and endemic patterns of Majoidea (Crustacea, Decapoda, Brachyura) in Brazil
• Grantee: William Ricardo Amancio Santana
• Support Opportunities: BIOTA-FAPESP Program - Regular Research Grants