Taxonomic revision of Isocheles Stimpson, 1858 and Loxopagurus Forest, 1964 (Decapoda: Anomura: Diogenidae) using morphological and multigene data, with the description of a new Eastern Pacific species

Author(s)

Vera-Silva, Ana L. ; Mantelatto, Fernando L.

• Document type: Journal article
• Source: JOURNAL OF CRUSTACEAN BIOLOGY; v. 42, n. 4, p. 25-pg., 2022-12-01.

Abstract

The genera Isocheles and Loxopagurus are endemic to America and occur in tropical and subtropical waters. There are five species of Isocheles, two of them are found in the Western Atlantic (I. sawayai and I. wurdemanni) and three in the Eastern Pacific (I. pilosus (), I. pacificus, and I. aequimanus ()). Loxopagurus is a monotypic genus and occurs only in southeastern South America. These two genera are morphologically similar, with differences in shape and size of chelae. The published information on the taxonomy of these genera is scant, and there have been some recent doubts about their phylogenetic relationship. Our study aimed to elucidate the phylogenetic relationship of Isocheles and Loxopagurus and evaluate their taxonomic validity and contextualization in Diogenidae Ortmann, 1892. We performed an integrative analysis using multigene data (16S rRNA, COI, and H3) and a detailed morphological evaluation, including redescriptions, seeking characters that allow the clear identification of these species. The type specimens of I. aequimanus, I. pilosus, and L. loxochelis () were lost and errors are common regarding the identification of the species of Isocheles. Characters that clearly delimit these species, such as the ornamentation and shape of the chelipeds and the number of teeth on the second article of the antenna, were stated. The morphological and molecular analyses corroborated the taxonomical validity of Isocheles and Loxopagurus as two distinct genera based on the differences of the shield and chelipeds, on the topology of the trees, and on the genetic divergence inferred from three molecular markers. We also verified that the five amplified species of Isocheles constitute five distinct clades and described a new species of Isocheles, using both molecular and morphological differences from congeners. An identification key for Isocheles is proposed. Although the type material of two out of the five species of Isocheles and the holotype of Loxopagurus loxochelis were lost, the designation of neotypes is not recommended in these cases. (AU)

• FAPESP's process: 09/54931-0 - Improvement and management of biological specimen collections at the Departamento de Biologia, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo
• Grantee: Carlos Alberto Garofalo
• Support Opportunities: Research Infrastructure Program - Biological specimen collections
• FAPESP's process: 10/50188-8 - Decapod crustaceans: multi-disciplinary characterization of the sea biodiversity of the State of São Paulo (taxonomy, spermiotaxonomy, molecular biology and population dynamics)
• Grantee: Fernando Luis Medina Mantelatto
• Support Opportunities: BIOTA-FAPESP Program - Thematic Grants
• FAPESP's process: 18/13685-5 - Integrative analysis of the Brazilian fauna of decapod crustaceans: taxonomy, phylogenetic systematics, spermiotaxonomy, morphology of post-embryonic development, ecology and conservation
• Grantee: Fernando Luis Medina Mantelatto
• Support Opportunities: BIOTA-FAPESP Program - Thematic Grants
• FAPESP's process: 21/08075-6 - Training of specialized human resources in the molecular taxonomy field: decapod crustaceans as a training model
• Grantee: Fernando Luis Medina Mantelatto
• Support Opportunities: BIOTA-FAPESP Program - Regular Research Grants