A comparison of probabilistic and stochastic formulations in modelling growth uncertainty and variability.

We compare two approaches for inclusion of uncertainty/variability in modelling growth in size-structured population models. One entails imposing a probabilistic structure on growth rates in the population while the other involves formulating growth as a stochastic Markov diffusion process. We present a theoretical analysis that allows one to include comparable levels of uncertainty in the two distinct formulations in making comparisons of the two approaches.

Hemolymph osmolality and cation concentrations in Litopenaeus vannamei during exposure to artificial sea salt or a mixed-ion solution: relationship to potassium flux.

Interest in culturing the Pacific white shrimp Litopenaeus vannamei in low-salinity and brackish-well waters has led to questions about the ability of this species to osmo- and ionoregulate in environments containing low concentrations of ions and in environments with ionic ratios that differ from those found in sea water. After seven days, hemolymph osmolality and potassium, sodium and calcium values were all significantly affected by salinity (as artificial sea salt) with values decreasing with decreasing salinity. These decreases were small, however, relative to decreases in salinity, indicating iono- and osmoregulation with adjustment for gradients. The hemolymph osmolality and sodium and calcium concentrations in shrimp exposed to either 2 g/L artificial sea salt or 2 g/L mixed-ion solution (a mixture of sodium, potassium, calcium, and magnesium chlorides that approximate the concentrations and ratios of these cations found in 2 g/L dilute seawater) did not differ significantly. However, hemolymph potassium levels were significantly lower in shrimp held in the mixed-ion environment. Potassium influx rates were similar in shrimp held in either artificial sea salt or mixed ions. The results of this study indicate that salinity affects hemolymph-cation concentrations and osmolality. Further, differential potassium-influx rates do not appear to be the basis for low hemolymph potassium levels observed in shrimp held in mixed-ion environments.

Modeling shrimp biomass and viral infection for production of biological countermeasures.

In this paper we develop a mathematical model for the rapid production of large quantities of therapeutic and preventive countermeasures. We couple equations for biomass production with those for vaccine production in shrimp that have been infected with a recombinant viral vector expressing a foreign antigen. The model system entails both size and class-age structure.

Immune gene discovery by expressed sequence tag analysis of hemocytes and hepatopancreas in the Pacific White Shrimp, Litopenaeus vannamei, and the Atlantic White Shrimp, L. setiferus.

A pilot program was undertaken in immune gene discovery in two sister species of litopenaeid shrimp, the Pacific white shrimp, Litopenaeus vannamei and the Atlantic white shrimp, L. setiferus. RNA from the hemocytes and hepatopancreas of single individuals from each species was recovered, 4 cDNA libraries (one from each tissue/species) were made by a PCR-based method and a total of approximately 2045 randomly selected clones were sequenced. A total of 268 expressed sequence tags (ESTs) were found that corresponded to 44 immune function genes. The most common immune-function ESTs (172) were antimicrobial peptides, which were restricted to the hemocyte libraries. Lectins were the largest group of immune-function ESTs found in the hepatopancreas. Analysis of these libraries indicates that EST approaches are effective for immune gene discovery in shrimp and that the diversity of these PCR-generated libraries would support full-scale EST collection.

Protein synthesis in vitro in cultures of the subepidermal adipose tissue and the ovary of the shrimp Penaeus semisulcatus.

In vitro culture systems were developed for subepidermal adipose tissue (SAT) and ovary of the shrimp Penaeus semisulcatus. Both tissues were cultured in sea water-based media buffered with HEPES to pH 7.4 in an oxygen enriched atmosphere. Various incubation conditions were tested in order to define those supporting optimal rates of protein synthesis. Best results for de novo protein synthesis were obtained when amino acids and other supplements were added according to Landureau's medium composition for the SAT and Eagle's MEM for the ovary. Streptomycin was found to inhibit protein synthesis in SAT cultures. These in vitro systems are appropriate for future studies of serum lipoprotein synthesis and its hormonal control.