Development of digestive enzymes in larvae of Mayan cichlid Cichlasoma urophthalmus

The development of digestive enzymes during the early ontogeny of the Mayan cichlid (Cichlasoma urophthalmus) was studied using biochemical and electrophoretic techniques. From yolk absorption (6?days after hatching: dah), larvae were fed Artemia nauplii until 15?dah, afterward they were fed with commercial microparticulated trout food (45% protein and 16% lipids) from 16 to 60?dah. Several samples were collected including yolk-sac larvae (considered as day 1 after hatching) and specimens up to 60?dah. Most digestive enzymes were present from yolk absorption (5?C6?dah), except for the specific acid proteases activity (pepsin-like), which increase rapidly from 8?dah up to 20?dah. Three alkaline proteases isoforms (24.0, 24.8, 84.5?kDa) were detected at 8?dah using SDS?CPAGE zymogram, corresponding to trypsin, chymotrypsin and probably leucine aminopeptidase enzymes, and only one isoform was detected (relative electromobility, Rf?=?0.54) for acid proteases (pepsin-like) from 3?dah onwards using PAGE zymogram. We concluded that C. urophthamus is a precocious fish with a great capacity to digest all kinds of food items, including artificial diets provided from 13?dah.     

Partial characterization of digestive proteases of the three‐spot cichlid Cichlasoma trimaculatum (Günter 1867)

Partial characterization of digestive proteases in the three‐spot cichlid Cichlasoma trimaculatum juveniles was conducted. It was determined that there is higher alkaline proteases activity (3.95 ± 0.32 IU mg^?1 protein) compared to acidic proteases (2.01 ± 0.57 IU mg^?1 protein). Optimal temperature for alkaline proteases is 60 °C which resulted in more thermostability to temperature changes. On the other hand, optimal temperature for acidic proteases is 50 °C. Optimal pH for acidic proteases was pH 2, while for alkaline proteases, it was pH 10, which resulted in more stability in relation to pH changes than acidic protease. The use of specific inhibitors and the SDS‐PAGE electrophoresis analysis revealed seven types of bands for alkaline proteases, which make evident the main presence of serine proteases. In acidic proteases, more than 98 g kg^?1 of the activity was inhibited with pepstatin A inhibitor. Therefore, it is evident that C. trimaculatum digestion is composed by acidic and alkaline proteases; thus, it should be considered an omnivorous fish.     

Digestibility studies in juveniles of the Mexican cichlid, Cichlasoma urophthalmus (Günther)

Abstract. A simple trial is described to determine the effects of brown fish meal, solvent extracted soybean meal, raw wheat meal, raw starch and dextrin on diet digestibility in juveniles of the Mexican cichlid, Cichlasoma urophthalmus (Gümher). The effects of possible anti-nutrients in the feedstuffs used were assessed with the purpose of designing practical diets. The results did not show any effect attributable to anti-nutrients, but showed that high dietary fibre levels reduced digestibility. The carbohydrates of soybean meal were poorly digested compared with the other sources utilized. These results suggest that the substitution of fish meal by soybean meat and other plant proteins could be increased to reduce costs of practical diets for this species.     

Phosphorus and calcium requirements in the diet of the American cichlid Cichlasoma urophthalmus (Günther)

An experiment was carried out with Cichlasoma urophthalmus (Günther) juveniles to determine the phosphorus requirement and its interaction with dietary calcium. Twelve isoenergetic and isoproteic diets were prepared using a basal artificial diet containing vitamin-free casein, dextrin, starch, corn oil, fish oil, vitamin mixture and a mineral mixture free of calcium and phosphorus. Calcium and phosphorus levels were determined in the casein. To the basal diets were added different concentrations of phosphorus as potassium monophosphate (0.5, 1.0, 1.5 and 2.5 g kg^–1) and calcium as calcium carbonate (0.5, 0.75, 1.0, 1.5, 2.0, 2.5, 3.0 and 4.0 g kg^–1). These concentrations resulted in varying Ca–P ratios (1:1, 1.33:1, 1.5:1, 1.6:1 and 2.0:1). Calcium and phosphorus concentrations in the water were 84 mg kg^–1 and 0.003 mg kg^–1, respectively. The diet with 0.5 g kg^–1 phosphorus resulted in deficiency signs such as reduced growth, high conversion ratio, high fat content and low bone mineralization. Increased levels of dietary calcium and phosphorus both gave improved growth and mineralization. Mineralization continued to increase with dietary phosphorus levels above that required for maximum growth. The optimum level of phosphorus in the diet was 1.5 g kg^–1, the optimum calcium level was 1.8 g kg^–1 and the optimum Ca–P ratio was 1.3. Carcass lipid levels were inversely related to dietary phosphorus.     

Histopathology of vitamin C deficiency in a cichlid, Cichlasoma urophthalmus (Günther)

Abstract. This paper describes the histopathological changes observed in the Mexican native cichlid Cichlasoma urophthalmus (Günther) when try with an initial weight of between 160 and 170 mg were fed with diets deficient in vitamin C for 90 days. The epidermis showed an extensive inflammatory response, with spongiosis and also degenerative changes in the basal cells. Muscle showed a range of pathological changes including inflammation, changes in the number and position of the nuclei, vacuolation and necrosis, granular degeneration, and fibre loss. Gills showed thickening of the primary lamellae, oedema, hyperplasia, telangiectasis and atrophy of the bony supporting structures. Ganglia and neurones of nervous tissue were abnormal with changes which ranged from slight inflammation to central chromatolysis. The hepalopanereas was also affected and focal necrosis of the hepatocytes was frequently observed. The pancreas showed major changes with shrinkage of the acinar cells and reduction of zymogen granule content. Fish fed diets containing 0 and 40 mg vitamin C kg^-1 of diet were infected with Mycobacterium sp. and miliary tuberculosis was found affecting kidney, spleen, choroid gland, stomach, heart and muscle. The association between fish tuberculosis and vitamin C deficiency is discussed.     

Changes in digestive enzyme activities during the early ontogeny of the South American cichlid (Cichlasoma dimerus)

Fish Physiology and Biochemistry - Cichlasoma dimerus is a neotropical cichlid that has been used as a biological model for neuroendocrinology studies. However, its culture is problematic in terms...     

Partial characterization of digestive proteases in tropical gar Atractosteus tropicus juveniles

Tropical gar (Atractosteus tropicus) is an economically and socially important freshwater species from Southeastern Mexico, with a high aquaculture potential. With this in mind, the purpose of this study was to characterize the digestive proteases of tropical gar juveniles through biochemical and electrophoretic analyses. Twenty specimens with an average weight of 73.6 ± 12.7 g were used to obtain stomach and intestinal tissue from which multienzymatic extracts were prepared. The general activities of the acid and alkaline proteases were evaluated, as well as the specific activities of trypsin, chymotrypsin, leucine aminopeptidase and carboxypeptidase A. The effect of the pH and temperature on the proteases was also analyzed, together with the composition of the multienzymatic extracts using protease inhibitors and electrophoretic tests. Results showed that A. tropicus have a functional stomach in which protein hydrolysis starts with pepsin and which contains endo- and exopeptidases (trypsin, chymotrypsin, leucine aminopeptidase and carboxypeptidase A) and proteases that are resistant to high temperatures (45 and 55 °C for alkaline and acid proteases, respectively) and pH values. Using zymogram technique, we found two acid protease isoforms (0.35 and 0.71 rf) and five alkaline protease isoforms (83.7, 43.7, 27.5, 24.0 and 19.4 kDa), which decrease or disappear with the different inhibitors. Thus, this species is considered to be a carnivore capable of adapting to its environment by consuming different types of proteins from preys and also could adapt rapidly to consume a compound diet with different animal protein sources.     

Acute toxicity of Trichlorfon (Dipterex) to fry of Cichlasoma urophthalmus Günther

Abstract. Fry of Cichlasoma urophthalmus Günther were exposed to various concentrations of the organophosphate pesticide Trichlorfon, ranging from 1·25 to 80 mg/l in laboratory conditions. Mortality reached 100% in the highest concentrations (60 and 80 mg/l) in the first 24h. The intermediate concentration (40 mg/l) resulted in 50% mortality after 24h, and no mortality was observed in lower levels of the pesticide. LC50 at 24, 48 and 72h were 26·5, 23·7 and 17·2 mg/l respectively.
Some of the surviving fish were transferred to clean fresh water for a post-treatment growth trial. All the fish grew well with no apparent adverse effects as judged by their growth indices after 8 weeks.     

The optimum dietary protein level for the Mexican cichlid Cichlasoma urophthalmus (Günther): a comparison of estimates derived from experiments using fixed-rate feeding and satiation feeding

Optimum dietary protein levels of young Cichlasoma urophthalmus (Günther) of 0.3 g mean weight were determined at 28°C using two methods, a fixed feeding rate of 6% body weight per day and satiation feeding. In the fixed rate trials nine isoenergetic diets were formulated with protein levels ranging from 347 to 561 g kg^?1 using brown fish meal (anchovy) as the only protein source. In the satiation feeding trials, ten diets were formulated based on brown fish meal (mackerel) ranging from 0 to 450g kg^?1 protein. When fish were fed a fixed rate diet, the best absolute growth was obtained with diets between 435 and 560 g kg^?1 protein. Broken-line analysis showed that, in terms of weight gain (%), the optimum protein level was about 453 g kg^?1. When fish were fed to satiation, the best absolute growth was obtained with the 383 g kg^?1 protein diet, and broken-line analysis suggested an optimum of about 325 g kg^?1. The difference between the two results, using the two techniques, is very marked. The probable mechanism underlying these data is discussed.     

Effects of stocking density on the growth rates of Cichlasoma urophthalmus (Günther) cultured in floating cages

Abstract. An experimental growth trial in floating cages at three different stocking densities was carried out. 15–19-cm mean total length, 18.5-g mean individual weight fish were stocked at 25, 50 and 1OO per m³. A 40% protein balanced diet was used as feed. The results of the study showed no statistically significant differences in growth among the three treatments. Food conversion ratios ranged from 3.10 to 3.34, and spiecific growth rates were between 1.40 and 1.48%/day.     

The requirement of Cichlasoma urophthalmus (Günther) fry for pantothenic acid and the pathological signs of deficiency

Abstract. Fry of Cichlasoma urophthalmus (Günther) weighing 160-175 mg were fed for 75 days on diets containing seven different levels of calcium pantothenate. Fish fed on the three lowest inclusion levels (up to 0,10 and 20 mg/kg) exhibited a variety of external signs and high mortalities. Fish fed on the higher inclusion levels (40, 60, 80, 120 and 320 mg/kg) did not show external pathologies. At the end of the experiment there was no significant difference in these diets (P<0.01) in final weight, individual weight gain, individual food intake, food conversion ratio, and specific growth rate. Marked interlamellar lesions were observed in gills of fish fed on the lowest inclusion level diets. The lesions ranged from oedema, hyperplasia covering all the secondary lamellae to the complete fusion of adjacent filaments. These fish also developed necrosis of the pancreas, whilst fish fed diets up to 80 mg/kg showed marked glycogen deposition in the hepatic cells. For the first time it is reported that fish deficient in pantothenic acid showed ceroid deposition in the hepatic cells and spleen. Fish fed on diets containing 80-320 mg/kg did not show external or histological changes. It is thus recommended that the diet of C. urophthalmus fry must be supplemented with at least 80 mg/kg diet to give maximum growth and to avoid gross and histologicai signs of deficiency.     

红头丽体鱼红魔丽体鱼杂交子一代胚胎发育及仔鱼形态学观察

对红头丽体鱼[Cichlasoma synspilum（♀）]红魔丽体鱼[C.citrinellum（♂）]杂交子一代（F1）（俗称血鹦鹉）的胚胎及仔鱼形态发育进行观察,描述了各发育时期的发育时序和形态特征。平均受精率为（91.333.06）%,平均孵化率为（91.672.08）%;血鹦鹉的受精卵呈椭圆球形,黏性,有浅黄、白灰和红褐3种颜色,无油球,平均卵长径为（1.890.04）mm;发育过程可分为6个阶段：受精卵阶段、卵裂阶段、原肠期、神经胚期、器官形成期和孵出期,并进一步分为28个发育分期;在水温（300.5）℃下历时约52 h 36 min完成孵化。初孵仔鱼全长（3.710.05）mm,卵黄长径为（1.740.09）mm,短径为（1.250.07）mm,于第3天开始摄食轮虫,孵出后第5天卵黄囊完全消失。第13 天全长（11.861.02）mm,各鳍条基本形成,进入稚鱼期。     

Determination of morphometric parameters in the Mexican mojarra, Cichlasoma urophthalmus (Günther), for the design and construction of box graders

Abstract. The morphometric relationships, standard length-weight, standard length-width and weight-width for Cichlasoma urophthalmus (Günther) in the weight range 0.78-262g were: log₁₀ weight =−4.35 + 2.95 × (log₁₀ standard length); log₁₀ width =−0.73 + 0 99 × (log₁₀ Standard length) and log₁₀ width = 0.74 + 0.33 × (log₁₀, weight). Two box graders were designed and tested based on these data. The operation efficiency (expressed as a percentage of the sample used to test it) was 96.1 % and 95% for the two graders. Results indicated a tendency to undergrading (small fish detained by the bars) by the first grader and overgrading (large fish going between the bars) by the second, the latter as a result of the major variability in the body shape from fish as they grow. The results are satisfactory, and larger graders for commercial use could be constructed based on these relationships.     

The effects of temperature, body weight and hypoxia on the oxygen consumption of the Mexican mojarra, Cichlasoma urophthalmus (Günther)

Abstract. The oxygen consumption rate of the Mexican cichlid, Cichlasoma urophthalmus Günther, was determined using closed-circuit respirometry at 20,25,30 and 36°C over a weight range of l·91–116g. Oxygen consumption rates ranged from 31 to 4500mg/kg/h and were slightly higher than for other cichlid species reported. Q10 was 2·49 between 20°Cand 30°C, but showed a direct increase with temperature. The species is an oxygen conformer, with an estimated critical oxygen tension of 70 mmHg at 28°C. This confers good low oxygen tolerance and some advantages for culture. The fish were able to withstand virtual anoxia for up to 2h. The significance of these results is discussed.     

The effects of water temperature on food intake, growth and body composition of Cichlasoma urophthalmus (Günther) juveniles

The optimum growth, food intake, food conversion efficiency, final body composition and mortality of juvenile Cichlasoma urophthalmus (Günther) was studied at different temperatures, ranging from 22.5 to 36.3^°C. The results showed that food intake and specific growth rate increase rising to an apparent optimum at about 33.1^°C. Multiple regression equations were derived which can be used to predict food intake and specific growth rate when temperature and initial body weight are known.     

Evaluation of Larval Growth and Survival in Mexican Mojarra,Cichlasoma urophthalmus,and Bay Snook,Petenia splendida,Under Different Initial Stocking Densities

Two experiments were conducted to evaluate the initial stocking density in larvae of Bay snook, Petenia splendida, and Mexican mojarra, Cichlasoma urophthalmus, using a recirculation system. Five initial stocking densities (0.5, 1, 5, 10, and 20 larvae/L) were evaluated by triplicate for 45 d. Weight and total length (TL) were measured every 15 d, and fish production was calculated for each density. The larvae stocked at the lowest densities (0.5 and 1 larvae/L) presented the highest growth for both species: C. urophthalmus (0.78 g and 45‐mm TL, and 0.76 g and 45‐mm TL, respectively) and P. splendida (0.80 g and 52‐mm TL, and 0.79 g and 49‐mm TL, respectively). However, lowest fish production was recorded (35 and 69 fish per tank, respectively, for C. urophthalmus and 34 and 70 fish per tank, respectively, for P. splendida) compared with those at densities of 5, 10, and 20 larvae/L (336, 584, and 604 fish per tank, respectively, for C. urophthalmus and 341, 679, and 912 fish per tank, respectively, for P. splendida). The polynomial model for biomass production related to the stocking density shows that the optimum stocking densities for C. urophthalmus and P. splendida are 12 and 14 larvae/L, respectively.