Influence of Moult Cycles on Digestive Enzyme Activities during Early Larval Stages of Panulirus ornatus

The tropical spiny lobster, Panulirus ornatus, has a complex life cycle characterised by a series of moults that occur throughout pelagic larval stages. Significant morphological, physiological, and biochemical changes commonly coincide with moulting and can have dietary implications when culturing this species. Digestive enzyme activities respond to nutritional requirements and have provided useful insight into nutrient use dynamics associated with first-feeding in P. ornatus. Beyond first-feeding, however, information on digestive enzyme activities in P. ornatus is scarce. Greater knowledge of fluctuations in digestive enzyme activities during moult cycles should facilitate better formulation of feeds and more efficient feeding regimens. As an initial step towards this goal, the present study evaluated the influence of moult cycles on digestive enzyme activities during early larval stages of P. ornatus. The investigation focused exclusively on early larval stages (stages I-III) when delivery of appropriate feeds and nutrition can dramatically affect subsequent growth and survival

Experimental Analysis of Functional Variation within Protein Families: Receiver Domain Autodephosphorylation Kinetics

ABSTRACT Plants and microorganisms use two-component signal transduction systems (TCSs) to mediate responses to environmental stimuli. TCSs mediate responses through phosphotransfer from a conserved histidine on a sensor kinase to a conserved aspartate on the receiver domain of a response regulator. Typically, signal termination occurs through dephosphorylation of the receiver domain, which can catalyze its own dephosphorylation. Despite strong structural conservation between receiver domains, reported autodephosphorylation rate constants ( k dephos ) span a millionfold range. Variable receiver domain active-site residues D + 2 and T + 2 (two amino acids C terminal to conserved phosphorylation site and Thr/Ser, respectively) influence k dephos values, but the extent and mechanism of influence are unclear. We used sequence analysis of a large database of naturally occurring receiver domains to design mutant receiver domains for experimental analysis of autodephosphorylation kinetics. When combined with previous analyses, k dephos values were obtained for CheY variants that contained D + 2/T + 2 pairs found in 54% of receiver domain sequences. Tested pairs of amino acids at D + 2/T + 2 generally had similar effects on k dephos in CheY, PhoB N , or Spo0F. Acid or amide residues at D + 2/T + 2 enhanced k dephos . CheY variants altered at D + 2/T + 2 exhibited rate constants for autophosphorylation with phosphoramidates and autodephosphorylation that were inversely correlated, suggesting that D + 2/T + 2 residues interact with aspects of the ground or transition states that differ between the two reactions. k dephos of CheY variants altered at D + 2/T + 2 correlated significantly with k dephos of wild-type receiver domains containing the same D + 2/T + 2 pair. Additionally, particular D + 2/T + 2 pairs were enriched in different response regulator subfamilies, suggesting functional significance. IMPORTANCE One protein family, defined by a conserved domain, can include hundreds of thousands of known members. Characterizing conserved residues within a conserved domain can identify functions shared by all family members. However, a general strategy to assess features that differ between members of a family is lacking. Fully exploring the impact of just two variable positions within a conserved domain could require assessment of 400 (i.e., 20 × 20) variants. Instead, we created and analyzed a nonredundant database of receiver domain sequences. Five percent of D + 2/T + 2 pairs were sufficient to represent 50% of receiver domain sequences. Using protein sequence analysis to prioritize mutant choice made it experimentally feasible to extensively probe the influence of positions D + 2 and T + 2 on receiver domain autodephosphorylation kinetics

Anaesthetic induced relaxation of the winged pearl oyster, Pteria penguin, varies with oyster size and anaesthetic concentration

Stress and mortality of pearl oysters during nucleus implanting for round pearl and mabé pearl production can be reduced using appropriate anaesthetics that allow improved access to nucleus implanting sites. This study evaluated the efficacy of three different concentrations of benzocaine (0.25, 0.50 and 1.20 g L-1) and 1-propylene phenoxetol (2.50, 3.00 and 3.50 mL L-1) when presented to ‘small’ (dorso-ventral height [DVH], 78.7 ± 1.6 mm), ‘medium’ (DVH, 118.2 ± 2.0 mm) and ‘large’ (DVH, 149.3 ± 1.1 mm) cohorts of the winged pearl oyster, Pteria penguin. Results showed the following general trends across treatments with both anaesthetics: (1) greater proportions of large oysters became relaxed compared to small oysters; (2) large oysters required shorter exposure times to become relaxed than small oysters; (3) for each size class of oyster, an increase in anaesthetic concentration resulted in an increased proportion of relaxed oysters; and (4) ‘mantle collapse’ (where the mantle collapses away from the shell) was only recorded in large oysters in treatments with higher concentrations of anaesthetics. The most effective concentration of benzocaine to use with small, medium and large Pt. penguin was the highest level tested in this study (1.20 g L-1). Similarly, the highest concentration of 1-propylene phenoxetol tested (3.5 mL L-1) was also the most effective with all three size classes of Pt. penguin. These treatments caused mantle collapse in large oysters, for which use of lower, less effective anaesthetic concentrations may be considered preferable, to avoid potentially negative impacts of mantle collapse on subsequent mabé pearl production. As well as efficacy, choice of anaesthetic should consider ease of preparation and preparation time. Benzocaine requires dissolving in methyl alcohol and heating to 88–92˚C, while 1-propylene phenoxetol is readily soluble in seawater

Natural rarity places clownfish colour morphs at risk of targeted and opportunistic exploitation in a marine aquarium fishery

As fish stocks become depleted, exploitation eventually fails to be cost-efficient. However, species or morphs of species can suffer from continual exploitation if their rarity results in increased value, justifying the cost-efficiency of targeted or opportunistic exploitation. The trade in coral reef fishes for public and private aquaria is an industry in which naturally rare species and rare morphs of species command high prices. Here we investigate the relationship between price and the natural prevalence of colour morphs of two highly demanded clownfish species using a localised case study. The export prices for colour morphs increased with decreasing prevalence of occurrence (y = 4.60x−0.51, R2 = 0.43), but price increase was inversely less than the observed reduction in prevalence. This renders rare colour morphs (i.e., those at relatively low prevalence) at risk of opportunistic exploitation. Using ecological data, we also demonstrate how this increased value can subject rare colour morphs with aggregated distributions to targeted exploitation. These findings are discussed in relation to the broader marine aquarium trade, identifying taxa potentially at risk from exploitation motivated by rarity and addressing potential management strategies

Diffusive limit for a quantum linear Boltzmann dynamics

In this article, I study the diffusive behavior for a quantum test particle interacting with a dilute background gas. The model I begin with is a reduced picture for the test particle dynamics given by a quantum linear Boltzmann equation in which the gas particle scattering is assumed to occur through a hard-sphere interaction. The state of the particle is represented by a density matrix that evolves according to a translation-covariant Lindblad equation. The main result is a proof that the particle's position distribution converges to a Gaussian under diffusive rescaling.Comment: 51 pages. I have restructured Sections 2-4 from the previous version and corrected an error in the proof of Proposition 7.

Contract Aware Components, 10 years after

The notion of contract aware components has been published roughly ten years ago and is now becoming mainstream in several fields where the usage of software components is seen as critical. The goal of this paper is to survey domains such as Embedded Systems or Service Oriented Architecture where the notion of contract aware components has been influential. For each of these domains we briefly describe what has been done with this idea and we discuss the remaining challenges.Comment: In Proceedings WCSI 2010, arXiv:1010.233

A vertebrate case study of the quality of assemblies derived from next-generation sequences

The unparalleled efficiency of next-generation sequencing (NGS) has prompted widespread adoption, but significant problems remain in the use of NGS data for whole genome assembly. We explore the advantages and disadvantages of chicken genome assemblies generated using a variety of sequencing and assembly methodologies. NGS assemblies are equivalent in some ways to a Sanger-based assembly yet deficient in others. Nonetheless, these assemblies are sufficient for the identification of the majority of genes and can reveal novel sequences when compared to existing assembly references