Tornabene, L.

Mesophotic coral ecosystems, which occur at depths of ~40 to 150 m, have received recent scientific attention as potential refugia for organisms inhabiting deteriorating shallow reefs. These ecosystems merit research in their own right, as they harbor both depth-generalist species and a distinctive reef-fish fauna. Reef ecosystems just below the mesophotic are globally underexplored, and the scant recent literature that mentions them often suggests that mesophotic ecosystems transition directly intothose of the deep sea. Through submersible-based surveys in the Caribbean Sea, we amassed the most extensive database to date on reef-fish diversity between ~40 and 309 m at any single tropical location. Our data reveal a unique reef-fish assemblage living between ~130 and 309 m that, while taxonomically distinct from shallower faunas, shares strong evolutionary affinities with them. Lacking an existing name for this reef-faunal zone immediately below the mesophotic but above the deep aphotic, wepropose “rariphotic.” Together with the “altiphotic,” proposed here for the shallowest reef-faunal zone, and the mesophotic, the rariphotic is part of a depth continuum of discrete faunal zones of tropical reeffishes, and perhaps of reef ecosystems in general, all of which warrant further study in light of globaldeclines of shallow reefs.

Two new Lipogramma basslets are described, L. barrettorum and L. schrieri, captured during submersible diving to 300 m depth off Curaçao, southern Caribbean. Superficially resembling L. robinsi in having 11–12 bars of pigment on the trunk, L. barrettorum is distinct from L. robinsi in having a stripe of blue-white pigment along the dorsal midline of the head (vs. a cap of yellow pigment), in patterns of pigment on the median fins, and in having 8–10 gill rakers on the lower limb of the first arch (vs. 11–12). Lipogramma schrieri is distinct from all congeners in having seven or eight dark bars of pigment on the trunk and broad, irregular, whitish blue markings on the dorsal portion of the head. The new species are genetically distinct from one another and from seven other Lipogramma species for which genetic data are available. A phylogenetic hypothesis derived from mitochondrial and nuclear genes suggests that the new species belong to a clade that also comprises L. evides and L. haberi. Collectively those four species are the deepest-living members of the genus, occurring at depths predominantly below 140 m. This study thus provides further evidence of eco-evolutionary correlations between depth and phylogeny in Caribbean reef fishes. Tropical deep reefs are globally underexplored ecosystems, and further investigation of Caribbean deep reefs undoubtedly will provide samples of species for which no genetic material currently exists and reveal more cryptic species diversity in the genus.

Bathygobius is currently represented by three species in the western Atlantic (B. soporator, B. curacao and B. mystacium) based on diagnostic morphological features. Our combined genetic and morphological analyses indicate that there are at least six species of Bathygobius comprising eight genetic lineages in the western Atlantic. Two lineages are identified as B. curacao and B. mystacium. Four lineages possess char- acters that would previously have led to their identification as B. soporator. Two of those are morphologically indistin- guishable and are recognized here tentatively as a single species, B. soporator. A third “B. soporator” lineage is dis- tinct, and Gobius lacertus is resurrected here as Bathygobius lacertus for that lineage. The fourth “B. soporator” lineage is also distinct and is described as a new species. Two other closely related genetic lineages are morphologically indis- tinguishable and are treated as a single new species. Redescriptions of B. soporator, B. mystacium and B. curacao are provided. Comments are made on the identification of larval Bathygobius from Belize.