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Background: The Bocas del Toro Archipelago is located off the Caribbean coast of Panama. Until now, only 19 species of heterobranch sea slugs have been formally reported from this area; this number constitutes a fraction of total diversity in the Caribbean region. Results: Based on newly conducted fieldwork, we increase the number of recorded heterobranch sea slug species in Bocas del Toro to 82. Descriptive information for each species is provided, including taxonomic and/or ecological notes for most taxa. The collecting effort is also described and compared with that of other field expeditions in the Caribbean and the tropical Eastern Pacific. Conclusions: This increase in known diversity strongly suggests that the distribution of species within the Caribbean is still poorly known and species ranges may need to be modified as more surveys are conducted.

A list of the marine invertebrate species identified until now from the rocky intertidal shore at Montepío, Veracruz, is presented. The information was obtained from 10 years of collections made by the Colección Nacional de Crustáceos and additional records were compiled from published information. The species list includes the life form in relation to the substrate, epifauna or criptofauna, as well as its type of distribution considering the 2 main zoogeographic provinces recognized for the Gulf of Mexico: Carolinean and Caribbean; the species found only in the Gulf of Mexico are also noted. The list includes 195 species belonging to 9 groups of which Crustacea is the most diverse with 73 species, followed by Mollusca with 69 and Echinodermata with 18; the less diverse groups were Chelicerata with 2 species and Platyhelminthes and Sipuncula with 1 species each. Seventy-four species represent new locality records and 7 are new records for Veracruz. A total of 5 517 invertebrate species have been reported for the Mexican portion of the Gulf of Mexico, thus 3.5% of this total can be found in Montepio. More species were part of the epifauna (70%) than the criptofauna (30%) which is composed mainly by molluscs, polychaetes and sipunculids. A larger tropical affinity was observed in the obtained species composition; however, an important number of species are more subtropical or Carolinean (86) and 51 species occur only in the Gulf of Mexico.

Autonomous reef monitoring structures (ARMS) have been proposed as a standardized, passive, nondestructive sampling tool. This study assessed the ability of ARMS to capture the cryptic species diversity of two coral reefs by recording species richness and taxonomic representativeness using conventional taxonomy. The capacity of ARMS, as artificial substrates, to favor the establishment of nonindigenous species over native species was also evaluated. The use of ARMS allowed the detection of 370 species morphotypes from nine phyla, yielding 13 new records of geographic distribution expansion, one exotic species for the Gulf of México and the Caribbean Sea, and six newly described species. It was also possible to make spatial comparisons of species richness between both reefs. ARMS captured cryptic diversity exceptionally well, with the exception of echinoderms. Furthermore, these artificial structures did not hinder the colonization ability of native species; in fact, the colonization patterns on the structures themselves represented the spatial differences in the structure of benthic assemblages. This study represents the first effort to make a conventional taxonomic description of the cryptic fauna of the Yucatan Peninsula using ARMS. It is recommended to assess coral reef species diversity, but more taxonomists specialized in marine invertebrates are needed.

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