Ariadna Sánchez

Haemolymph metabolic variables and immune response in Litopenaeus setiferus adult males: the effect of an extreme temperature

Abstract The stress of captivity could be the main reason for the loss of sperm quality of Litopenaeus setiferus (L) males in captivity. The aim of this study was focused on the physiological and immunological response of adult male shrimp exposed to a temperature extreme (33 °C) in order to understand how the stress modulates the physiological, immunological and reproductive behavior of L. setiferus males. We used some blood metabolic variables, sperm quality and immune response as indicators of stress measured daily during the 10-day experiment. The high temperature provoked loss of osmotic capacity (OC), a reduction in blood metabolites at day 5, a reduction in hemocyte pro Phenoloxidase (proPO) activity and a dramatic reduction in sperm quality in comparison to that observed in freshly captured wild shrimp populations. The ratio between proPO and granular cells (small granular and large granular cells) (proPO/GC) showed a cyclic behavior with lower peaks at days 3, 7 and 10 and high peaks at days 0, 5–6 and 8–9, evidencing migration and recovery of cells and proPO every 48–96 h, depending on the intensity of the stress. Such hemocyte migration was directed to the ampule and spermatophore where bacterial growth could be enhanced by abnormal and dead sperm cells. In such circumstances, a rapid mobilization of reserves could help to promote tissue regeneration in male testes and vas deferens. Such use of reserves could explain the reduction in blood metabolites observed at day 5 in present study. Although blood metabolites recovered after day 5, the loss of OC suggests that shrimp lose their osmotic homeostasis, possibly associated with the entrance of water due to inflammation of tissues provoked by melanization.

Acclimation of Adult Males of Litopenaeus Setiferus Exposed at 27 °C and 31 °C: Bioenergetic Balance

The reduction of reproductive performance of adult males of Litopenaeus setiferus in captivity has been limiting the massive nauplii production, mainly by lowering the spermatophore attachment success associated with the male reproductive tract degenerative and the male reproductive melanization syndromes. Both syndromes had been related to the captivity and management stress. In this study the bioenergetic alterations were measured after seven days in captivity through absorption efficiency (AE), absorption (A), routine respiratory rate (R ROUT ), apparent heat increment (R AHI ), ammonia excretion (U) and post-prandial nitrogen excretion (PPNE), as indexes of captivity stress in adult males of L. setiferus kept at 27 and 31 °C. All this parameters were integrated through the production equation (P T ) = A − (R AHI + R ROUT + U) At 31 °C, the equation values were higher than those observed at 27 °C, except for R ROUT and ammonia excretion. The amount of energy directed to P T at 31 oC was 1784.99 J g−1 afdw d−1, in contrast with shrimp exposed at 27 °C, where it was 1269.22 J g−1 afdw d−1 (P > 0.05). The O:N ratio obtained was lower than 10, indicating the use of a proteic substrate (P > 0.05). The reduction of the metabolic responses at high temperature shows what the adaptation capability of this shrimp is to tolerate a wide range of temperatures, also reflecting the adaptation mechanisms associated with its distribution in shallow coastal waters.

The effects of exposure to critical thermal maxima on the physiological, metabolic, and immunological responses in adult white shrimp Litopenaeus vannamei (Boone)

Exposure to thermal stress was shown to have a significant effect on the osmotic pressure of the hemolymph, glucose levels, total count of hemocyte (TCH), and proPO activity in adult white shrimp Litopenaeus vannamei. Exposure of the shrimp to CTMax significantly increased the osmotic pressure of the hemolymph relative to the control group. In organisms reaching CTMax, temperature elicited a secondary stress response that included an increase in hemolymph glucose of 31 mg mL−1. Metabolites in hemolymph such as cholesterol, acylglycerides, and total protein were not significantly affected by exposure to CTMax. CTMax exposure affected several immunological parameters causing decreases in TCH and proPO activity. We suggested that biomarkers such as osmolality, glucose levels, TCH, and proPO activity could be used as sensitive predictors of exposure to CTMax in white shrimp.

Digestive Physiology of Octopus maya and O. mimus: Temporality of Digestion and Assimilation Processes

Digestive physiology is one of the bottlenecks of octopus aquaculture. Although, there are successful experimentally formulated feeds, knowledge of the digestive physiology of cephalopods is fragmented, and focused mainly on Octopus vulgaris. Considering that the digestive physiology could vary in tropical and sub-tropical species through temperature modulations of the digestive dynamics and nutritional requirements of different organisms, the present review was focused on the digestive physiology timing of Octopus maya and Octopus mimus, two promising aquaculture species living in tropical (22–30°C) and sub-tropical (15–24°C) ecosystems, respectively. We provide a detailed description of how soluble and complex nutrients are digested, absorbed, and assimilated in these species, describing the digestive process and providing insight into how the environment can modulate the digestion and final use of nutrients for these and presumably other octopus species. To date, research on these octopus species has demonstrated that soluble protein and other nutrients flow through the digestive tract to the digestive gland in a similar manner in both species. However, differences in the use of nutrients were noted: in O. mimus, lipids were mobilized faster than protein, while in O. maya, the inverse process was observed, suggesting that lipid mobilization in species that live in relatively colder environments occurs differently to those in tropical ecosystems. Those differences are related to the particular adaptations of animals to their habitat, and indicate that this knowledge is important when formulating feed for octopus species.

Sexual maturation and embryonic development in octopus: use of energy and antioxidant defense mechanisms using Octopus mimus as a model.

Sexual maturation and reproduction influence the status of a number of physiological processes and consequently the ecology and behaviour of cephalopods. Using Octopus mimus as study model, the present study was focused in the changes in biochemical composition that take place during gonadal maturation of octopus females and its consequences in embryo and hatchlings characteristics, putting special attention to energetic metabolites, digestive enzymes and antioxidant defence mechanisms. To do that, a total of 32 adult females of Octopus mimus were sampled during ovarian maturation and the biochemical composition (metabolites and digestive enzymes) of digestive gland (DG) and ovaries (only metabolites) were followed during physiological and functional maturation. Levels of protein (Prot), triacyl glycerol (TG), cholesterol (Chol), glucose (Glu) and glycogen (Gly) were evaluated. In DG also the activity of alkaline and acidic enzymes was measured. Simultaneously, groups of eggs coming form mature females were also sampled along development, and metabolites (Prot, TG, Glu, Gly, TG, Chol), digestive enzymes activity (Lipases, alkaline and acidic), antioxidant defence mechanisms and radical oxygen species (ROS) were evaluated. Results obtained showed that ovarium is a site for reserve of some nutrients for reproduction. Presumably, TG where stored at the beginning of the maturation processes followed by Chol, both at the same time were energetically supported by Glu, derived from Gly following gluconeogenic pathways. Also, was observed that embryos during organogenesis nutrients and enzymes (metabolic, digestive and REDOX system) where maintained without significant changes and in a low activity. Results obtained in the present study shows that that activity could be not energetically costly. In contrast, was observed that during the embryo growth there were mobilization of nutrients and activation of the metabolic and digestive enzymes, joint with increments in consumption of yolk and glycogen, and reduction in molecules associated with oxidative stress, allowing paralarvae hatch with the antioxidant defence mechanisms ready to support the ROS production.