Two new species of the marine littoral springtail genus Spinactaletes (Collembola: Actaletidae) from Costa Rica

Spinactaletes is a genus of obligatory marine littoral springtails characterized by marked sexual dimorphism. Males of most Spinactaletes species have spur-like sclerotized structures on the metathoracic legs, and many modified setae on the antennae that form the basis for almost all species level diagnostic characters. Females of most species have been impossible to identify when collected in isolation. The current distribution of the genus is restricted to the Antilles, Venezuela, and the Pacific coast of Mexico. However, this distribution is undoubtedly an artifact of collection effort. In this contribution, we report Spinactaletes for the first time from Central America (Costa Rica) and draw attention to the utility of the chaetotaxy of the internal metatibiotarsal face in the identification of females. We collected Costa Rican Spinactaletes at three localities on the Caribbean coast and at one locality on the Pacific coast. The material from the Caribbean coast includes new species, Spinactaletes campylorachis sp. nov. and Spinactaletes deltalus sp. nov., herein described. From the Pacific coast, we collected two females and a juvenile showing unique metatibiotarsal chaetotaxy, but formal description of the species is deferred until their males are found. Phylogenetic analysis of Actaletidae species, using morphological data, supports the basal position of Actaletes neptuni Giard, 1889 and Spinactaletes nemyops (Soto-Adames, 1987), but it cannot resolve relationships among species of Spinactaletes with metatibiotarsal spur. We suggest that molecular data will be needed to provide the phylogenetic backbone required to study character evolution and biogeography in this group.