Feasibility of compensatory growth in early juveniles of "red claw" crayfish Cherax quadricarinatus under high density conditions

The aim of this work is to study the feasibility to induce compensatory growth in Cherax quaricarinatus crayfish at an early stage of development under high density, the typical conditions of nursery phase. An advantageous characteristic of this species is the capacity to face temporary starvation, especially at early stages of development. This would help to design feeding strategies avoiding overfeeding, and diminishing operating costs in aquaculture. In this sense, during the last 8 years it was analyzed in this species the application of intermittent feeding, known as unfavorable feeding condition followed by daily feeding (favorable feeding condition). This alternative feeding protocol was used in the present study to trigger compensatory growth. Juveniles weighing 0.07 ± 0.01 g were distributed in 2 feeding regimes: C (control): juveniles fed daily during 60 days, and IF (intermittent feeding): juveniles deprived of food for 4 days and then fed for the following 4 days, these 4 days’ cycles were repeated during the first 20 days, on day 21 they were daily fed until day 60. Juveniles were stocked in each tank under 0.0096 crayfish/cm2 density, and zootechnical and biochemical parameters were evaluated throughout 60 days. A very suitable and similar survival (~ 65%) was maintained between feeding regimes, and the previously unfavorable feeding condition did not promote greater aggression among juveniles. There was a small compensatory response, but no recovery occurred probably because the favorable feeding condition was too short to trigger a strong compensatory response. Hyperphagia and improvement of feed conversion were not observed in juveniles of IF, suggesting that the high density was the key for these primary compensatory mechanisms to be absent. The competition for food, could have affected and changed the priority in allocating energy resources for accelerated growth. Lipids and glycogen content from body mass were strongly depleted after unfavorable feeding condition, but there was almost a 100% recovery during favorable feeding condition. We suggest that this response was detrimental to body mass as a priority and as a strategy for juveniles to extend survival during the ‘double’ nutritional stress caused by intermittent feeding and high density. The applicability of this alternative feeding strategy during an intensive production system can be viable, however, some changes must be considered in order to trigger compensatory growth. We suggest that a long-term of the favorable feeding condition could trigger a strong compensatory response if the high density tested in the study is maintained. We believe that juveniles of the current study had to face two nutritionally stressful factors: food restriction and high density. This could change the priority in allocation of energetic reserves and then the other suggestion would be to reduce the density if the same alternative feeding protocol is maintained.Fil: Stumpf, Liane. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Biodiversidad y Biología Experimental y Aplicada. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biodiversidad y Biología Experimental y Aplicada; ArgentinaFil: Sarmiento Cárdenas, Paul Nicolás. Universidad Nacional de Colombia; ColombiaFil: Timpanaro, Santiago. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Biodiversidad y Biología Experimental y Aplicada. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biodiversidad y Biología Experimental y Aplicada; ArgentinaFil: Lopez, Laura Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Biodiversidad y Biología Experimental y Aplicada. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biodiversidad y Biología Experimental y Aplicada; Argentin

Effects of intermittent starvation on the survival, growth, and nutritional status of the freshwater prawn Macrobrachium borellii Nobili, 1896 (Decapoda: Caridea: Palaemonidae)

We examined the effect of the double restriction-recovery cycle on survival, growth, and nutritional status of the freshwater prawn Macrobrachium borellii (Nobili, 1896), native to floodplain rivers of Argentina. The restriction period consisted of intermittent starvation (alternating four-day feeding with no feeding for four days) and a recovery period of continuous feeding following the restriction period. Survival was high over a 20-week trial with cycles of food scarcity. Prawns showed a slight impact on their growth throughout the entire first cycle of restriction-recovery; however, compensatory growth was not triggered. The reduction of growth was markedly more drastic after the second restriction period, but compensatory growth was not exhibited when the second recovery period was reestablished. Any possible impact of the double cycle of intermittent starvation on energy reserves and structure of the hepatopancreas was compensated by a posterior cycle of continuous feeding. The results demonstrated that M. borelli can successfully support long-term food scarcity throughout the juvenile and adult phases, at least intermittently and followed by a recovery period. The high nutritional flexibility is an adaptation to fluctuations in food availability and an advantage for successful ornamental aquaculture.Fil: Stumpf, Liane. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Biodiversidad y Biología Experimental y Aplicada. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biodiversidad y Biología Experimental y Aplicada; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental. Laboratorio de Biología de la Reproducción y Crecimiento de Crustáceos Decápodos; ArgentinaFil: Timpanaro, Santiago. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental. Laboratorio de Biología de la Reproducción y Crecimiento de Crustáceos Decápodos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Biodiversidad y Biología Experimental y Aplicada. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biodiversidad y Biología Experimental y Aplicada; ArgentinaFil: Battista, Ariadna Gabriela. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental. Laboratorio de Biología de la Reproducción y Crecimiento de Crustáceos Decápodos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Biodiversidad y Biología Experimental y Aplicada. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biodiversidad y Biología Experimental y Aplicada; ArgentinaFil: Lopez, Laura Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Biodiversidad y Biología Experimental y Aplicada. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biodiversidad y Biología Experimental y Aplicada; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental. Laboratorio de Biología de la Reproducción y Crecimiento de Crustáceos Decápodos; Argentin

Impact of low-cost diets on maturation of the red claw crayfish Cherax quadricarinatus: An integrative approach during a long-term study

The onset of sexual maturity represents a complex step in animal life involving morphological, physiological, and behavioral changes. From this point onward, the energy income from food will be involved in three energetic-demanding-competing processes: metabolism-homeostasis, growth, and reproduction. Hence, in cultured species formulated feeds need to cover all nutritional requirements of the growing phase and the additional cost demanded by reproduction. Two low-cost diets, AD1: 0.56 and 2 CE: 0.64 U$S kg−1 manufactured with local supplies specifically formulated for Cherax quadricarinatus, were evaluated in a prolonged assay with females at the transition from juvenile to mature. Protein content was 440,2 and 380 g kg−1 and lipid content was 134,8 and 114,9 g kg−1 for AD1 and AD2, respectively. Females were obtained in the laboratory from our reproductive stock and were fed daily at 1.5% of their weight/day. The female mean initial total length was 6.5 ± 0.6 cm and mean body mass was 6.8 ± 0.7 g, which represents juveniles at the beginning of vitellogenesis. The experiment ended after three molting events when females achieved the full mature condition (⁓16–20 g). Somatic indices, growth, feed efficiency, biochemical composition of the ovary and hepatopancreas, ovarian growth, and histological alterations in hepatopancreas were analyzed. Both diets demonstrated that the high demands of both somatic and ovarian growth in maturating females were not covered, contrasting with previous results in early juveniles. This highlights the enormous energetic cost of vitellogenesis at the start of sexual maturity and the differential nutrients demand during crayfish growth. Biochemical analysis demonstrated a lower oocyte quality due to the experimental diets, as well as decreased reserves both of lipids and carbohydrates and a possible impact on carotenoids content. The hepatopancreas also showed partial histological damage and differences in its biochemical content. Although further analysis is required, lower embryo survival, hatching rate, and early performance of juveniles are expected in progeny from females fed with both diets. The low-cost diets tested are useful as a baseline from which modified formulations can be considered to achieve a more adequate composition enhancing somatic and gonad growth as well as feed efficiency in maturing females