Three new diterpene alkaloids, (+)-8-epiagelasine T (1), (+)-10-epiagelasine B (2), and (+)-12-hydroxyagelasidine C (3), along with three known compounds, (+)-ent-agelasine F (4), (+)-agelasine B (5), and (+)-agelasidine C (6), were isolated from the sponge Agelas citrina, collected on the coasts of the Yucatán Peninsula (Mexico). Their chemical structures were elucidated by 1D and 2D NMR spectroscopy, HRESIMS techniques, and a comparison with literature data. Although the synthesis of (+)-ent-agelasine F (4) has been previously reported, this is the first time that it was isolated as a natural product. The evaluation of the antimicrobial activity against the Gram-positive pathogens Staphylococcus aureus, Streptococcus pneumoniae, Enterococcus faecalis showed that all of them were active, with (+)-10-epiagelasine B (2) being the most active compound with an MIC in the range of 1–8 µg/mL. On the other hand, the Gram-negative pathogenes Acinetobacter baumannii, Pseudomonas aeruginosa, and Klebsiella pneumoniae were also evaluated, and only (+)-agelasine B (5) showed a moderate antibacterial activity with a MIC value of 16 μg/mL.

A short-term Jolly–Seber mark-recapture model experiment is described. This experiment was aimed at estimating the rate of catch per unit effort (CPUE) and the catchability coefficient (q) of the Atlantic blue crab (Callinectes sapidus) in the fishing port of Sisal, Yucatan, Mexico. To estimate the local population size, 52 traps were deployed along four transects located in a coastal capture area of 3600 m⁻². The CPUE and q were compared between the daily mark-recapture Jolly–Seber experiment and the bi-monthly (carried out every 2 months) samplings. The average abundance was estimated at 3475 individuals. All three suggested scenarios, applied to estimate densities, gave similar estimates, i.e. 0.0386, 0.0350, 0.0365 crabs m⁻² for the first (Previously Cited Attraction Radius), second (CPUE per transect) and third (Catchability-Density Relationship), respectively. Based on the latter scenario, densities ranged from 27,900 (annual average) to 36,500 (Spring) crabs km⁻². The average CPUE of the daily mark-recapture experiment was estimated at 1.96 crabs trap⁻¹, whereas the average bi-monthly CPUE was estimated at 1.13 crabs trap⁻¹. The q (per trap) was estimated at 0.0186 for the daily mark-recapture experiment and at 0.0247 for the bi-monthly sampling. Both catchability and CPUE increased in individuals whose size ranged between 110 and 170 mm CW. However, no significant difference (ANCOVAs) was found between the daily and bi-monthly samplings neither in CPUE nor in catchability. The use of both mark-recapture data and the Jolly–Seber model proved to be a fast and reliable method for estimating the abundance and catchability of Atlantic blue crab.

Helminth communities in amphibians in Mexico have received little attention. During 2005 and 2006, we collected a total of 52 individuals of the marine toad (Rhinella marina) and 54 of the southern Gulf Coast toad (Incilius valliceps) in the Lagunas de Yalahau (Yucatán, Mexico), in order to study their helminth communities. We produced rarefaction and extrapolation sample-size-based and coverage-based curves to provide asymptotic diversity estimators based on Hill numbers to compare the communities. We calculated the first 3 Hill numbers, which are associated with estimators of species richness and species dominance. In general, all results showed that the sample size was large enough to register most of the species of parasites present in both host toad species. We found more helminth species and a higher diversity in the R. marina community than that in I. valliceps. However, extrapolation analysis showed that when a sample size of 50 individuals is reached, there are no statistical differences between the helminth communities. Our results suggest that amphibian communities in this part of the tropics follow the same pattern as described for Nearctic latitudes, equally the terrestrial habitat of the hosts is an important factor in the structure of its helminth communities.

The populations of Acropora palmata have decreased over the last four decades, and although there are several studies on their genetic diversity in the Caribbean, no studies have been published about the reefs from the southern Gulf of Mexico. This research aimed to determine, using five microsatellite markers, the genetic variation of three A. palmata populations in the Mexican Atlantic located in the southwest Gulf of Mexico, in the Campeche Bank, and in the Caribbean. The mean of genetic richness (Ng/N) in the studied reefs was 0.583; the lowest estimated value corresponded to the Campeche Bank reef. A low genetic diversity was registered in the studied reefs (reef mean He = 0.315 ± 0.052). The significant genetic structure observed among studied populations could be related to ocean currents from the region and specific biological characteristics, mainly, short larvae phase, high mortality, and high rate of self-recruitment. These results may be particularly useful for designing management strategies, considering the lack of studies of this type in the region.