Humberto Villarreal

Effect of temperature on lipids, proteins, and carbohydrates levels during development from egg extrusion to juvenile stage of Cherax quadricarinatus (Decapoda: Parastacidae)

The influence of temperature on biochemical composition, survival and duration of development of Cherax quadricarinatus from egg extrusion to juvenile was analyzed. Berried females were individually subjected to each of 22, 25, 28 and 31 degrees C (n=5 per temperature). Egg samples were obtained every 3 days from egg extrusion to juvenile stage for biochemical analysis. Duration of development and survival decreased with increasing temperature. At 22 and 25 degrees C half of the initial lipid content was consumed during development. At 28 and 31 degrees C, 80% of the initial amount of lipids was consumed. For proteins, depletion rate was significantly lower at 25 degrees C (36% of the initial amount) than at 22, 28 and 31 degrees C (61-65% of the initial amount). For carbohydrates, a significant consumption was observed only at 22 degrees C. Total energy consumption was lower at 22 and 25 degrees C than at 28 and 31 degrees C. We conclude that 22-25 degrees C is the optimal temperature range for C. quadricarinatus egg incubation, although 25 degrees C might be better in terms of development duration in terms of survival, energy cost and protein consumption.

Effect of temperature and salinity on the oxygen consumption of laboratory produced Penaeus californiensis postlarvae

Abstract The routine rate of oxygen consumption by Penaeus vannamei postlarvae (mean weight = 0.15 g) was determined at four temperatures and five salinities. The time course of oxygen depletion in the chambers was independent of the dissolved oxygen (DO) level down to 1.3 mg/1. Oxygen consumption during normoxic conditions increased with temperature and ranged from 0.0060 mg/g/min at 25 ppt and 20°C, to 0.0183 mg/g/min at 35 ppt and 32°C. Salinity had only a marginal effect on consumption. At high salinities, there was an increase in the metabolic demand, probably caused by an apparent loss in the capacity to maintain the osmotic and ionic balances as temperature increased. A critical point (Pc), where oxygen consumption by the shrimp changes from being independent of DO level to being dependent, was found. Pc was correlated to temperature. Below Pc, oxygen consumption was reduced to approximately 34% of the normal rate.

VARIATION IN LIPID, PROTEIN, AND CARBOHYDRATE CONTENT DURING THE EMBRYONIC DEVELOPMENT OF THE CRAYFISH CHERAX QUADRICARINATUS (DECAPODA: PARASTACIDAE)

Eggs of 20 females were sampled to analyze lipid, protein, and carbohydrate content during the embryonic development of Cherax quadricarinatus. Sampling was performed on recently spawned eggs to first juvenile stage. Ten eggs were sampled every 48 h during the first two weeks and every 72 h thereafter for biochemical analysis. Total proteins, lipids, and carbohydrates were measured. Proteins were the most abundant egg component (63.2%), followed by lipids (32.3%), and carbohydrates (4.4%). A steady decrease of lipid content was observed (y 5 895.38 2 9.93x, r 2 5 0.94; y 5 lipid concentration, x 5 days). For proteins, two different depletion rates were observed, with the initial rate maintained for 30 days (y1 5 1,443.0 2 4.46x1, r 2 5 0.90) and an increased depletion rate after hatching (y2 5 1,936.60 2 21.10x2, r 2 5 0.96). Carbohydrates were always present as a minor constituent, and its concentration did not change significantly. Water content increased from 52% in recently spawned egg to 85% in juveniles. Energy equivalents were calculated from each component, and the overall energy expenditure is represented by the equation y 5 13.86 2 0.11x (r 2 5 0.95). Relevant morphological features for each sample day are indicated.

Effect of size and temperature on the oxygen consumption of the brown shrimp Penaeus californiensis (Holmes, 1900)

Abstract 1. 1. The routine rate of oxygen consumption by Peneaus californiensis was determined for the size groups with average weights of 0.26, 2.31 and 10.01 g at five temperatures (19, 23, 27, 31 and 35°C). 2. 2. Oxygen consumption (mg O2/g min) was independent of dissolved oxygen (DO) level down to 1.8mg/l, increased with temperature (P 3. 3. The thermal coefficient (Q10) indicated a higher sensitivity by preadults to temperature variations.

Effect of temperature on oxygen consumption and heart rate of the australian crayfish Cherax tenuimanus (Smith)

Abstract 1. 1. Oxygen consumption at 18°C was 60% of the rate at 22 and 26°C. 2. 2. Critical points, where the rate of oxygen consumption changed, were defined at 22°C (2.89 mg DO) and 26°C (3.46 mg DO). Linear regressions were fitted showing that oxygen consumption declined significantly (81.5% ±4.5) below the critical point. 3. 3. Oxygen consumption was proportional to weight. Allometric relationships resulted in variable temperature-related coefficients for respiratory dependence on weight, a reflection of the crayfish adaptation towards re-establishment of a new equilibrium state. 4. 4. Heart beat rate was lower at 18°C, and highest at the acclimation temperature (22°C). Stress at 26°C was evident.

Gonadic conditioning of the calafia mother-of-pearl oyster, Pinctada mazatlanica (Hanley, 1856), under two temperature regimes.

Abstract Gonadic conditioning of pearl oyster Pinctada mazatlanica was studied under two water temperature regimes using cultured specimens. Before starting conditioning, specimens were induced to spawn with thermal shock. Two different regimes were evaluated, controlled temperatures (CT) and gradually increasing temperatures (IT). In both trials, specimens were fed daily with Isochrysis galbana and Chaetoceros gracilis in a proportion of 7:3. Gonad and muscle samples were excised from the oysters every 15 days and processed for histological analysis. Condition Index and Muscle Condition Index were calculated. Similarly, oocyte frequency and oocyte diameter measurements were made. ANOVA analyses were used to test significant differences in the frequency and diameter of postvitellogenic oocytes, and values of both condition indexes between temperature regimes, and over time. The IT showed more suitable conditions for gonad conditioning than CT, although the time needed for reaching maturity was higher in the former regime. For CT, a temperature of 24°C was the best for conditioning, since there were no traces of atretic oocytes, partially spawned specimens, and there were less previtellogenic oocytes and more postvitellogenic oocytes filling the follicles. At 20°C, no positive results were noticed. Condition indexes appear to be reliable indicators of gonad activity during conditioning in both trials. The ANOVA analysis detected significant differences in almost all the statistical treatments run for oocyte frequency, oocyte diameter and condition indexes according to temperature regime and over time.

Presence of ciliate colonies on the exoskeleton of the freshwater crayfish Cherax tenuimanus (Smith) [Decapoda: Parastacidae]

Dense colonies of the protozoan Epistylis sp. were found on the exoskeleton of one-year-old Cherax tenuimanus being reared at a commercial farm near Woongoolba, Qld. The ciliate has not been considered to be directly harmful to C. tenuimanus. Large colonies however were found covering pereiopods and maxillipeds, and extending to the brachiostegite and the ventral portion of the abdomen, and are believed to be responsible for the death by asphyxia of several crayfish. Probable causes of the ciliate bloom on the crustacean carapace are (i) a dramatic reduction in ecdysal frequency, related to temperature, (ii) bacterial blooms resulting from excessive organic matter in the pond, and (iii) the lack of alternative sites for colonization by the ciliate.

Differential gonadal development of grafted and ungrafted specimens of the Calafia mother-of-pearl oyster, Pinctada mazatlanica (Bivalvia: Pteriidae)

Summary The present work deals with the existence of differential gonadal development between grafted and ungrafted specimens of the pearl oyster, Pinctada mazatlanica. Oysters were collected as spat and extensively cultured until they were suitable for pearl formation. A mantle allograft was placed within the gonadal tissue and the treated oysters were maintained under the same culture conditions as untreated oysters. After a year of Keshi pearl formation, samples of gonadal tissue, digestive gland, and muscle were excised from each oyster and used for histological and biochemical analyses. The histological examination of gonads was supported with measurements of the oocyte frequency and diameter and the use gonadic and muscle performance indices. For biochemical analyses, the concentration of carbohydrates, proteins, lipids, and triacylglycerides was studied. A two-way ANOVA was applied for differences in the oocyte diameter, index values, and biochemical composition of specimens over time and experimental treatments. All histological and biochemical results showed that grafted oysters achieved greater gonadal performance and were in better reproductive condition than the controls. They presented higher gonadic index values and lower muscle performance index values than untreated specimens. In addition, grafted oysters showed higher concentrations of lipids and triacylglycerides in the gonadal tissue and digestive gland and lower concentrations of proteins in the muscle than ungrafted oysters. Apparently the mantle allograft stimulates redirection of energy flows to reproduction and gonadal development. The muscle and digestive gland (particularly the former) are the main sources for this energy-requiring process. A neuroendocrine control involving the formation of a complex relationship between both mantle and gonadal tissues is suggested. More studies of the histological, histochemical, biochemical, and endocrine composition of mantle of pearl oysters are required to confirm these findings.

Growth, metabolic and physiological response of juvenile Cheraxquadricarinatus fed different available nutritional substrates.

There are many factors in intensive culture conditions which vary the physiological response of organisms in culture affecting performance such as growth, metabolic levels in blood, respiratory metabolism and the inflection point of dissolved oxygen concentration. The study was conducted under high density culture conditions with multitrophic systems. Results show that the species can tolerate intensive culture conditions without affecting their growth and survival and has the ability to leverage multiple food sources. This work also shows that Cheraxquadricarinatus has the ability to maintain a low routine metabolic rate, is highly tolerant to limited dissolved oxygen conditions and thus uses energy efficiently. The metabolic rate in juvenile C. quadricarinatus was 0.07 ± 0.003 mg O2/g/h while the critical level of oxygenconcentration, when the organism passes from regulator to conformer is 0.483 ± 0.002 mg O2/L. This is significantly lower than previously reported for cultured decapod species.

Energy storage during the transition from endogenous to exogenous feeding in Australian redclaw crayfish Cherax quadricarinatus (Von Martens, 1898)

Summary The Australian redclaw crayfish Cherax quadricarinatus hatches at an advanced stage. Two post-hatching stages rely on yolk reserves before the organism becomes a juvenile. After a juvenile appears, the yolk is depleted and young crayfish might spend a few days among female pleopods before starting to feed independently. During this phase, the juvenile organism needs alternative energy sources. Offspring from three females were analyzed with histological and histochemical techniques, from hatching until reaching the 2-week juvenile stage, to trace digestive system development and internal organ lipid and glycogen accumulation. Neutral lipids are stored in specialized cells of the hepatopancreatic tissue until the juvenile stage is reached. An increasing rate of accumulation was found. Glycogen was stored in hepatopancreas and tail muscle cells until post-embryo II, and no increasing or decreasing rate was found in storage functions.