Common snook (Centropomus undecimalis) is one of the most important marine species under commercial exploitation in the Gulf of Mexico; for this reason, interest in developing its culture is a priority. However, larviculture remains as the main bottleneck for massive production. In this sense, our objective was to determine the changes of digestive enzymes activities using biochemical and electrophoretic techniques during 36 days of Common snook larviculture fed with live preys (microalgae, rotifers, and Artemia). During larviculture, all digestive enzymatic activities were detected with low values since yolk absorption, 2 days after hatching (dah) onwards. However, the maximum values for alkaline protease (6,500 U mg protein(-1)), trypsin (0.053 mU × 10(-3) mg protein(-1)), and Leucine aminopeptidase (1.4 × 10(-3) mU mg protein(-1)) were detected at 12 dah; for chymotrypsin at 25 dah (3.8 × 10(-3) mU mg protein(-1)), for carboxypeptidase A (280 mU mg protein(-1)) and lipase at 36 dah (480 U mg protein(-1)), for α-amylase at 7 dah (1.5 U mg protein(-1)), for acid phosphatases at 34 dah (5.5 U mg protein(-1)), and finally for alkaline phosphatase at 25 dah (70 U mg protein(-1)). The alkaline protease zymogram showed two active bands, the first (26.3 kDa) at 25 dah onwards, and the second (51.6 kDa) at 36 dah. The acid protease zymogram showed two bands (RF = 0.32 and 0.51, respectively) at 34 dah. The digestive enzymatic ontogeny of C. undecimalis is very similar to other strictly marine carnivorous fish, and we suggest that weaning process should be started at 34 dah.

In Mexico, aquaculture is a growing sector, but it continues to be developed using non‐native species. The natural ecosystems of the lowland humid tropics of southeastern Mexico have been well‐described by ecologists and are host to a very high diversity of species, including a substantial ichthyofauna. Cichlid fish, commonly known in southeast Mexico as ‘mojarras’, are an important fish resource and are widely consumed. Several species are now under considerable pressure and consequently the generation of biotechnology for the culture of native fish species is necessary and worthwhile. This paper examines and describes the experiences and knowledge generated over recent years regarding the aquaculture of native cichlids in the southeast of Mexico. Although the scientific and technological capacity for research and development for native species culture exists, there is an evident lack of information on new technologies among producers, as scientific research is not translating fully into technical assistance. Research and extension should be emphasized in order to develop a comprehensive knowledge base on native species and to enable their cultivation.

Para describir los cromosomas del cariotipo en mitosis y meiosis de la mojarra tenguayaca P. splendida, se procesaron 60 larvas y doce jóvenes (seis hembras y seis machos) procedentes de Tabasco, México. Se emplearon los procedimientos citológicos clásicos para peces pequeños y grandes, con algunas modificaciones que permitieron obtener campos cromosómicos en meiosis y mitosis. Analizamos al microscopio 100 laminillas, contando 290 dispersiones cromosómicas. En mitosis, 76.7 % de los conteos dieron número modal diploide de 2N=48 cromosomas, mientras en meiosis el 55.2 % mostró 24 cromosomas en condición haploide. Se analizaron ocho de las mejores fotografías para establecer el cariotipo y se identificaron tres pares de cromosomas birrámeos metacéntricos-submetacéntricos (msm) y 21 pares de cromosomas monorrámeos subtelocéntricos-acrocéntricos (sta) con número fundamental (N.F) de 54 brazos. Se corroboró el cariotipo mediante el análisis de campos cromosómicos en estadio haploide y diploide de la meiosis I. Las dispersiones cromosómicas tuvieron un número mayor en larvas que en jóvenes. No hubo diferencias heteromórficas para distinguir cromosomas sexuales. Sin embargo, se observó la presencia de cuerpos cromáticos en forma de puntos, como una característica propia de los microcromosomas ?B?. Para esta familia, el cariotipo de P. splendida es primitivo o tipo ?A?; y es estrechamente parecido al del género Cichlasoma. El origen de los cromosomas supernumerarios es un fenómeno aun desconocido en los cíclidos por lo que faltan estudios relacionados con el daño causado por la contaminación y la hibridación.

Karyotype of the tropical gar Atractosteus tropicus Lepisosteiformes: Lepisosteidae) and chromosomal variation in their larval and adults. The karyotype of the tropical gar Atractosteus tropicus is described from conventional Giemsa-staining of 295 mitotic chromosome slides from 120 larvae and 15 adults (five females and ten males) from Tabasco, southern of Mexico. The diploid number 2n = 56 chromosomes was calculated (73 spreads from 206 larval and 208 adult metaphases). Variation on chromosome number was from 46 (4.4%) to 64 (3.9%) chromosome elements on larval samples, whereas 58 (11.7 %) chromosomes were the second most abundant after the diploid number of 2n = 56 (35%). Such variation was related with the presence of mobile microchromosomes. The karyotype was determined from six clear chromosome spreads photographed from three females and three males. The averaged karyotype was integrated by eight pairs of metacentric (m) chromosomes, four submetacentric (sm) pairs, eight telocentric (t) pairs and eight pairs of telocentric microchromosomes (*t). The fundamental number was FN = 80 chromosome arms. We saw no sexual differences on chromosome structure.

In Mexico, the biology of Procambarus has been more studied than the biology of other Cambarids because of its diversity and potential use in aquaculture. We determined the karyotype of the Mexican tropical freshwater crayfish Procambarus (Austrocambarus) llamasi from 189 metaphase spreads from gill tissues of 17 adults. They had 98-120 chromosomes (mode 2n=120 chromosomes). There are 60 pairs of monoarm, telocentric chromosomes. Sex chromosomes were not detected and we propose that the P. llamasi karyotype can be used to distinguish this species from other Mexican crayfish. Additionally, we suggest using karyological data in aquaculture and conservation biology.