Characterization of microbiota and histology of cultured sea cucumber Isostichopus badionotus juveniles during an outbreak of skin ulceration syndrome.

Due to the dramatic reduction of sea cucumber Isostichopus badionotus populations in the Yucatan Peninsula by overfishing and poaching, aquaculture has been encouraged as an alternative to commercial catching and restoring wild populations. However, the scarcity of broodstock, the emergence of a new disease in the auricularia larvae stage, and the development of skin ulceration syndrome (SUS) in the culture have limited aquaculture development. This study presents the changes in the intestine and skin microbiota observed in early and advanced stages of SUS disease in cultured juvenile I. badionotus obtained during an outbreak in experimental culture through 16S rRNA gene sequencing and histological evidence. Our results showed inflammation in the intestines of juveniles at both stages of SUS. However, more severe tissue damage and the presence of bacterial clusters were detected only in the advanced stages of SUS. Differences in the composition and structure of the intestinal and skin bacterial community from early and advanced stages of SUS were detected, with more evident changes in the intestinal microbial communities. These findings suggest that SUS was not induced by a single pathogenic bacterium. Nevertheless, a decrease in the abundance of Vibrio and an increase in Halarcobacter (syn. Arcobacter) was observed, suggesting that these two bacterial groups could be keystone genera involved in SUS disease.

Acaricidal activity of Havardia albicans and Caesalpinia gaumeri methanolic leaf extracts on Rhipicephalus microplus and its toxicity to laboratory animals.

The acaricidal activity of methanolic extracts from the leaves of Havardia albicans (Kunth Britton and Rose) and Caesalpinia gaumeri (Greenm) were tested on the larvae and adults of the cattle tick Rhipicephalus microplus Canestrini using the larval immersion test and the adult immersion test, respectively. The toxicity of these extracts was also evaluated on laboratory animals using toxicity bioassays at different concentrations: skin irritability (500 mg/ml), acute oral toxicity (5000 mg/kg), ocular irritability (1000 mg/ml) and dermal toxicity (5000 mg/kg). The acaricidal activity of the H. albicans extracts on R. microplus larvae showed a LC50 of 7.0% (4.3-11.4) and a LC99 of 25.5% (14.26-201.5). The acaricidal activity of the C. gaumeri extracts on larvae showed a LC50 of 7.8% (5.74-10.65) and a LC99 of 38.32% (22.22-146.48). The H. albicans extracts showed moderate acaricidal activity in the inhibition of egg laying (54.4 ± 12.4) and the inhibition of larval hatching (48.7 ± 6.8) in R. microplus adults. The C. gaumeri extracts also showed moderate acaricidal activity in the inhibition of egg laying (51.0 ± 11.2). However, none of the evaluated extracts showed significant toxicity on laboratory rodents. These plants show the potential to control R. microplus and could be administered topically or orally in animals. Further studies are needed to identify the active compound(s) and to evaluate the effects of these plants on R. microplus in vivo.