Histology of reproductive cycle of tropical gar Atractosteus tropicus females (Lepisosteiformes:Lepisosteidae) in Tabasco, Mexico. In Southeast Mexico, A. tropicus is a species with great ecological, economic, cultural and aquaculture value, however wild populations have diminished due to diverse anthropological causes. The objective of this study was to characterize the reproductive cycle of A. tropicus, with a description of complete gonad structure and the changes in germinal and somatic elements during oogenesis, for better management and use of this species. Six sexually mature females (N=72) were captured monthly with drag nets during one year cycle (
Evaluación de oligosacáridos de manano (MOS) en dietas balanceadas para juveniles de pejelagarto (Atractosteus tropicus) Evaluation of Mannan oligosaccharides (MOS) in balanced diets for tropical gar juveniles (Atractosteus tropicus
This research study is focused on the lipid requirements of Petenia splendida (0.65 ± 0.19 g) juveniles. Fish were fed with trout commercial diet (Silver Cup™ - 45% protein and 16% lipids), as control diet - CD (which is usually used to feed this species at commercial scale), and four isoproteic (45% crude protein) diet formulated with different lipid levels (5, 10, 15 and 20%). Diets were administered for 60 days by triplicate per treatment. Our results showed that fish fed with 10, 15 and 20% lipid levels were significantly higher (P < 0.05) in average weight and total length. Same treatments were significantly lower (P < 0.05) in terms of FCR compared to those shown in 5% and CD. However, fish fed 20% lipid level, showed a significant decrease in WG and a significant (P < 0.05) increase in FCR compared to those shown in 15% lipid level. Fish fed with 15% showed the highest weight gain and the lowest FCR compared with the rest of the treatments. Lipid efficiency ratio (LER) showed significant (P < 0.05) differences among experimental groups. Compared to other diets containing lipid levels (5, 10, and 20%) fish fed 15% diet recorded the lowest protein and lipid content in whole body. Additionally, based on second order polynomial regression analysis of WG, it was demonstrated that 16.2% lipid provides an optimal growth for P. splendida.
The effect of adding inulin to balanced diets for tropical gar (Atractosteus tropicus) larvae on growth, survival, digestive enzyme activity, and antioxidant activity was evaluated. The diets were supplemented with 0.5, 1.0, 1.5, 2.0, and 2.5% inulin in addition to a control diet (0% inulin). A total of 1800 larvae of A. tropicus distributed in 18 tanks were used; the larvae were fed five times a day (8:00, 11:00, 13:00, 15:00, and 18:00) with Artemia nauplii from the absorption of the yolk (from 3–7 days after hatching, DAH) up to 10 DAH, which was mixed with the experimental feeds from 8–11 DAH (co-feeding) and exclusively with the balanced diets from 12 DAH to 21 DAH. Larvae fed the control diet (0% inulin) had the highest growth in weight and length, followed by fish fed the 2.5 and 2.0% inulin inclusions. However, survival showed that the fish fed with the inclusion of 2.5% inulin had the highest percentage (34.7%) compared to the rest of the treatments. On the other hand, the highest digestive enzymatic activities (acid and alkaline proteases, amylase, and lipase) were recorded in the larvae fed with 2 and 2.5% inulin. Likewise, catalase (CAT) and superoxide dismutase (SOD) activities were higher in larvae fed the control diet with 0% inulin. Supplementation of 2.0% to 2.5% inulin in the diet is recommended for A. tropicus larvae as it improves survival and digestive enzyme activity during this early stage of life.
Tropical gar A. tropicus plays an important ecological role, as a regulator of other fish stocks, in the water bodies of Mexico but their wild populations are being reduced. One conservation alternative is breeding which requires the study of germ and somatic structures of testis to characterize the reproductive cycle, basic knowledge required to create exploitation and conservation models. Three sexually mature males were captured on a monthly basis (N=24), in wild populations of Pomposu lagoon, municipality of Jalpa de Mendez (18°19'59" N - 93°01'12" W), Tabasco, Mexico. The capture technique was trawl net; they were transported live to the Tropical Aquaculture Laboratory, DACBiol, UJAT. Males were sacrificed by decapitation; testis fragments from all of the specimens collected were processes using a routine histological procedure, that consisted of dehydration for ascending etanol series, xylol, and inclusion in paraffin, with a sliding microtome 7µm thick cuts, and were dyed with hematoxylin-eosin (HE). The diameter of 20 seminiferous tubules (Tse), height of germinal epithelium (Egl), gonadosomatic index (GSI) and gonad volume (Gv) were determined on a monthly basis, as well as the gonadosomatic index GSI=PG/PT(100) and the gonad volume vG=4/3 pa2.b. Morpho-physiological characteristics of the testis show that it consists of a network of tubules anastomosed with non-restricted cystic spermatogenesis, and a permanent germinal epithelium. As far as we are concerned, this is the first time that this type of epithelium is reported in Holostei (Lepisosteiformes: Lepisosteidae). Five reproductive classes were identified: Class I Recrudescence, Class II Early Maturation, Class III Intermediate Maturation, Class IV Advanced Maturation, Class V Regression, that when contrasted with the monthly value of the "GSI, GV, Tse" sexual indicators it shows a variation pattern: January-February shows low values with empty testis, with discontinuous germinal epithelium in regeneration; in March spermiogenesis increased and spermatogenesis decreased. Generally speaking, these variations show that at a population level they do not mature synchronously, but with an annual seasonal reproductive cycle with spermatogenesis throughout the year, where temperature and precipitation seem to play an important role as a factor that stimulates reproductive activity and therefore spermiation.
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