Description of Calliactis tigris sp. nov.: reconciling taxonomy and phylogeny in hermit-crab symbiotic anemones (Cnidaria: Actiniaria: Hormathiidae)

• Published in: Organisms diversity & evolution 2019-12, Vol.19 (4), p.567-583
• Main Authors: Gusmão, Luciana C., Rodríguez, E., Daly, Marymegan
• Format: Article
• Language: English
• Subjects: Adamsia; Animal Systematics/Taxonomy/Biogeography; Biodiversity; Biomedical and Life Sciences; Calliactis; Cnidaria; Congeners; Crustaceans; Decapoda; Developmental Biology; Evolutionary Biology; Food supply; Genera; Hormathiidae; Invertebrates; Life Sciences; Marine crustaceans; Marine environment; Marine invertebrates; Mutualism; New species; Original Article; Paracalliactis; Phylogenetics; Phylogeny; Plant Systematics/Taxonomy/Biogeography; Shellfish; Stability; Substrates; Symbionts; Symbiosis; Synonymy; Taxonomic significance; Taxonomy
• ISSN: 1439-6092; 1618-1077
• DOI: 10.1007/s13127-019-00414-2

The symbiosis between sea anemones and hermit crabs is ubiquitous in the marine environment (except in the poles), occurring from shallow to deep waters; it involves one or more anemones living on a shell inhabited by a hermit crab. The anemone-crab partnership is a mutualism in which hermit crabs provide a hard substrate, increased access to oxygenated waters and food supply, in exchange for defense by the anemone. The vast majority of the sea anemone partners belong to three genera in family Hormathiidae: Adamsia , Calliactis , Paracalliactis . Given the remarkable nature of the symbiosis, hormathiid partners have been hypothesized to represent a monophyletic group. This has been rejected by Gusmão and Daly et al. ( 2010 ) and confirmed by our phylogenetic analysis using molecular markers (12S, 16S, 18S, 28S, COIII). We expand the results of Gusmão and Daly et al. ( 2010 ) by finding a monophyletic Paracalliactis , which was left untested in their analyses. Thus, characters of taxonomic significance associated to the symbiotic habit are interpreted as functional rather than phylogenetic. We reconcile taxonomy and the present evolutionary framework to avoid defining taxonomic groups based on characters prone to convergence. We formalize the synonymy of Adamsia and Calliactis and provide updated diagnoses for the valid genera Calliactis and Paracalliactis to bring more stability to the group. Under this new framework, we describe Calliactis tigris sp. nov. from Australia based on 21 specimens collected off the coast of New South Wales and Queensland and differentiate it from congeners and other hermit crab symbionts recorded in the Pacific Ocean.