Early development of two commercially valuable fish from the lower Amazon River, Brazil (Characiformes: Serrasalmidae)

We described the early development of Myloplus asterias and M. lobatus, two fish species of the Serrasalmidae using morphological, meristic, and morphometric characteristics. These herbivores serrasalmids are heavily fished because of their commercial importance in the Amazon. The individuals were collected between 2016 and 2020 in the limnetic zone of open water and macrophyte stands in the Lower Amazon River floodplain. We tested different growth models to identify the development pattern of these species. During the initial ontogeny, these two species can be differentiated mainly by the myomeres total number, 37 to 39 in M. asterias vs. 40 to 41 in M. lobatus, the pigmentation pattern, and dorsal-fin ray numbers. These characteristics are effective in distinguishing these species from other serrasalmids. The morphometric relationships were also different between these two species, showing distinct patterns in growth between the analyzed features. An identification key for larvae of some sympatric Serrasalmidae species from the Amazon basin is presented. Our expectation is that this study will contribute to the knowledge of the initial ontogeny and the biology of fish species in the Neotropical region.(AU)

Descrevemos o desenvolvimento inicial de Myloplus asterias e M. lobatus, duas espécies de peixes da família Serrasalmidae usando características morfológicas, merísticas e morfométricas. Esses serrasalmídeos herbívoros são fortemente pescados devido à sua importância comercial na Amazônia. Os indivíduos foram coletados entre 2016 e 2020 na zona limnética de águas abertas e em bancos de macrófitas na planície de inundação do baixo rio Amazonas. Testamos diferentes modelos de crescimento para identificar o padrão de desenvolvimento dessas espécies. Durante a ontogenia inicial, essas duas espécies podem ser diferenciadas pelo número total de miômeros; 37 a 39 em M. asterias vs. 40 a 41 em M. lobatus; pelo padrão de pigmentação e número de raios da nadadeira dorsal. Essas características são eficazes para distinguir essas espécies de outros serrasalmídeos. As relações morfométricas também foram diferentes entre as duas espécies, com distintos padrões de crescimento entre as características analisadas. Uma chave de identificação para larvas de algumas espécies simpátricas de Serrasalmidae da bacia amazônica é apresentada. Nossa expectativa é que este estudo contribua para o conhecimento da ontogenia inicial e da biologia das espécies de peixes da região Neotropical.(AU)

Cuantificación de hormonas 17β - estradiol y progesterona en el caracol rosa Lobatus gigas (Mollusca, Gastropoda)

La cuantificación de las hormonas esteroides en moluscos se lleva a cabo con diferentes técnicas utilizando la hemolinfa o gónadas. Lobatus gigas es un gasterópodo de interés comercial en el Caribe, indexado en CITES como una especie protegida. Los estudios hormonales de esta especie aún no están disponibles. Por lo tanto, el objetivo de este estudio fue determinar la presencia de las hormonas esteroides 17ß - estradiol y progesterona en L. gigas a través de un método no invasivo y comparar dos técnicas para su cuantificación. Cada dos meses en un período de un año, se recolectaron las heces de diez organismos en Xel-Há, Quintana Roo, México. Las muestras se analizaron con cromatografía líquida de alta resolución y EIA. Los valores más altos de ambas hormonas se presentaron de marzo a septiembre y disminuyeron en noviembre y enero. La comparación de las concentraciones obtenidas con HPLC y EIA, mostró que los resultados son similares para el 17β-estradiol (Passing - Bablock r = 0.673; -0.17 ng / ml). En contraste, los resultados de la progesterona con ambas técnicas no mostraron ajuste (Passing - Bablock r = 0.389; -1.43 ng / ml). Nuestros resultados sugieren que la técnica de EIA es adecuada para el estudio de hormonas en esta especie. El conocimiento generado permitirá monitorear y seleccionar organismos reproductores que se encuentren acondicionados en laboratorios y de esta manera no incidir en la recolecta de masas ovígeras silvestres.

Quantification of steroid hormones in molluscs is performed with different techniques, using the hemolymph or gonads. Lobatus gigas is a Caribbean gastropod of commercial interest indexed in CITES as a protected species. Hormonal studies of this species are as yet unavailable. The objective of this study is to determine the presence of the steroid hormones 17ß - estradiol and progesterone in L. gigas using a non-invasive method, and to compare two techniques for their quantification. Every two months over the course of one year, the feces of ten organisms were collected in Xel-Ha park Quintana Roo, México. The samples were analyzed with High resolution liquid chromatography and Enzyme-linked immunosorbent assays. The values of both hormones were highest during the months of March to September then decreased during November and January. Comparison of the concentrations obtained with HPLC and EIA, presented similar results for 17β-estradiol (Passing - Bablock r = 0.673; mean differences -0.17 ng / ml). In contrast, the progesterone results with both techniques showed no adjustment (Passing - Bablock r = 0.389; mean differences -1.43 ng / ml). Our results suggest that the enzyme-linked immunosorbent assay is suitable for the study of hormones in L. gigas. The knowledge generated will allow the monitoring and selection of breeding organisms that are conditioned in laboratories and thus will not affect the collection of wild egg masses.

Formulation and in-vitro characterization of hibiscus lobatus leaves mucilage as suspending agent.

The aim of the present investigation was to evaluate the mucilage obtained from leaves of hibiscus lobatus as a suspending agent. Sulphamethoxazole suspension was prepared by using four different suspending agents each at two different concentrations. The prepared suspensions were evaluated for pH, viscosity, sedimentation volume, degree of flocculation and redispersibility. The suspending effect of hibiscus mucilage was compared with suspensions prepared by using other suspending agents. The results indicating that hibiscus mucilage could be used as suspending agent. The suspension having 2% mucilage has high viscosity, slightly basic pH and easily redispersible properties.