Vol. 62, 2023

(update: 2023.913)

Minuca panema (Coelho, 1972): Resurrection of a Fiddler Crab Species from Brazil Closely Related to Minuca burgersi (Holthuis, 1967) (Crustacea, Decapoda, Brachyura, Ocypodidae)

Carl. L. Thurman¹, Hsi-Te Shih^2,*, and John C. McNamara^3,4

¹Department of Biology, University of Northern Iowa, 1227 West 27th St., Cedar Falls, IA 50614-0421, USA. E-mail: thurman@uni.edu (Thurman). Tel: +1 319 273-2276
2Department of Life Science and Research Center for Global Change Biology, National Chung Hsing University, Taichung 402, Taiwan. *Correspondence: E-mail: htshih@dragon.nchu.edu.tw (Shih). Tel/Fax: 886-4-22856496
3Departamento de Biologia, FFCLRP, Universidade de São Paulo, Ribeirao Preto 14040-901, Brazil. E-mail: mcnamara@ffclrp.usp.br (McNamara).Tel: +55 16 3315 3687
4Centro de Biologia Marinha, Universidade de Sāo Paulo, 11600-000 SP, Brazil

(Received 6 November 2022 / Accepted 9 July 2023 / Published 13 September 2023)
Communicated by Benny K.K. Chan

We redescribe a species of fiddler crab, Minuca panema (Coelho, 1972), from the Atlantic coast of South America. It is closely related to M. mordax (Smith, 1870), and until now, the taxon has been considered to be synonymous with another closely related species Minuca burgersi (Holthuis, 1967). However, we found that two clades of M. burgersi sensu lato were restricted to the Caribbean Basin. This distribution differs from than that of M. panema, which occurs primarily along the eastern coast of South America, ranging from the island of Trinidad to Praia da Armação, Santa Catarina, Brazil. Based on our field studies, the geographical boundary between M. burgersi sensu stricto and M. panema is the Tobago Basin, north of Trinidad. Since the two species diverged only 3 to 4 million years ago, as dated from the phylogeny of the genus Minuca Bott 1954, there are few reliable morphological features that can be used to distinguish them clearly. In live crabs, there is a striking difference in coloration between the cherry-red South American M. panema and the rusty-red Caribbean M. burgersi sensu lato. In males, the pattern of tubercles on the inner surface of the major cheliped varies between the two species. In females, the vulva is slightly larger in M. burgersi sensu stricto. Ocean tides and currents together with siltation owing to freshwater outflow from the Amazon and Orinoco rivers most likely have driven the divergence of these species. In the Caribbean, small tidal amplitudes have minimized long-distance gene flow in M. burgersi sensu stricto from isolated insular lagoons. In contrast, large tidal amplitudes and exposed habitats on riverbanks along the eastern Atlantic coast of South America have enabled long-distance dispersal in M. panema. DNA analysis reveals that haplotypes of cytochrome c oxidase subunit 1 are not shared between the species. Since natural selection and/or genetic drift have yet to produce extensive morphological
divergences between M. panema and M. burgersi sensu stricto, we speculate that changes in the genes regulating mitochondrial DNA functions have led to speciation at the molecular level. According to the mitonuclear compatibility concept, we propose that mitochondrial DNA may be at the forefront of speciation events and that co-evolved mitonuclear interactions are responsible for some of the earliest genetic
incompatibilities arising among isolated populations.

Key words: Morphology, 16S rDNA, 28S rDNA, Cytochrome c oxidase subunit I (COI), Biogeography

Citation: Thurman CL, Shih HT, McNamara JC. 2023. Minuca panema (Coelho, 1972): resurrection of a fiddler crab species from Brazil closely related to Minuca burgersi (Holthuis, 1967) (Crustacea, Decapoda, Brachyura, Ocypodidae). Zool Stud 62:45. doi:10.6620/ZS.2023.62-45.

Supplementary materials: Table S1