Underground environments are increasingly recognized as reservoirs of faunal diversity. Extreme environmental conditions and limited dispersal ability of underground organisms have been acknowledged as important factors promoting divergence between species and conspecific populations. However, in many instances, there is no correlation between genetic divergence and morphological differentiation. Lucifuga Poey is a stygobiotic fish genus that lives in Cuban and Bahamian caves. In Cuba, it offers a unique opportunity to study the influence of habitat fragmentation on the genetic divergence of stygobiotic species and populations. The genus includes four species and one morphological variant that have contrasting geographical distributions. In this study, we first performed a molecular phylogenetic analysis of the Lucifuga Cuban species using mitochondrial and nuclear markers. The mitochondrial phylogeny revealed three deeply divergent clades that were supported by nuclear and morphological characters. Within two of these main clades, we identified five lineages that are candidate cryptic species and a taxonomical synonymy between Lucifuga subterranea and Lucifuga teresinarum. Secondly, phylogeographic analysis using a fragment of the cytochrome b gene was performed for Lucifuga dentata, the most widely distributed species. We found strong geographical organization of the haplotype clades at different geographic scales that can be explained by episodes of dispersal and population expansion followed by population fragmentation and restricted gene flow. At a larger temporal scale, these processes could also explain the diversification and the distribution of the different species.

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Population genetic studies carried out on penaeid shrimps have disclosed different patterns of population subdivision, revealing new aspects of shrimp biology as well as the effects of historical contingency molding those patterns. However, the stability of observed allele frequencies over time still remains untested. The objective of this article is to show the analysis of the temporal variation of allozymes in a shrimp species inhabiting Cuba which proves that the genetic structure of this species could significantly change in time. The study involves four populations of Farfantepenaeus notialis sampled in a period of 8 years. The significant statistics obtained from partitions observed in 1995 were not detected in 2003 (as suggested by AMOVA and F(ST)), whereas temporal genetic differentiation and heterozygosity became highly significant. The results strongly suggest that the effect of migrations could be the cause for the loss of F. notialis genetic structure in 2003. It is therefore imperative to call attention on the vulnerability of these populations when facing unstable environmental and habitat conditions.

Crustacean serine proteases (Brachyurins, EC 3.4.21.32) exhibit a wide variety of primary specificities and no member of this family has been reported for spiny lobsters. The aim of this work was to study the diversity of trypsins in the digestive gland of Panulirus argus. Several trypsin-like proteases were cloned and the results suggest that at least three gene families encode trypsins in the lobster. Three-dimensional comparative models of each trypsin anticipated differences in the interaction of these enzymes with proteinaceous substrates and inhibitors. Most of the studied enzymes were typical trypsins, but one could not be allocated to any of the brachyurins groups due to amino acid substitutions found in the vicinity of the active site. Among other changes in this form of the enzyme, conserved Gly216 and Gly226 (chymotrypsin numbering) are substituted by Leu and Pro, respectively, while retaining all other key residues for trypsin specificity. These substitutions may impair the access of bulky residues to the S1 site while they make the pocket more hydrophobic. The physiological role of this form of the enzyme could be relevant as it was found to be highly expressed in lobster. Further studies on the specificity and structure of this variant must be performed to locate it within the brachyurins family. It is suggested that specificity within this family of enzymes is broader than is currently believed.

Recently, a barcoding study and a molecular phylogenetic analysis of the Cuban species of the cave-fish genus Lucifuga Poey, 1858 revealed the existence of different evolutionary lineages that were previously unknown or passed unnoticed by morphological scrutiny (i.e., cryptic candidate species). In the present study, Lucifuga gibarensis is described as a new species restricted to anchialine caves in the northeastern karst region of the main island. The species was earlier described as a variety of Lucifuga dentata, but since the name was introduced as a variety after 1960, it is deemed to be infrasubspecific and unavailable according to the International Code of Zoological Nomenclature Art. 15.2. The new species differs from L. dentata by pigmented eyes vs. eyes absent and lack of palatine teeth vs. present. Lucifuga gibarensis seems to be most similar to the Bahamian species L. lucayana by showing pigmented eyes, 13 or 14 precaudal vertebrae and ten caudal fin rays. However, differs from it by a larger size of the pigmented eye (1.1–1.9 vs. 0.9–1.0% SL) and number of posterior lateral line neuromasts (30–33 vs. 34–35).