Redescription and molecular characterisation of the fish parasitic isopod Norileca indica (Milne Edwards, 1840) (Crustacea: Isopoda: Cymothoidae) with a key to the genus

Norileca indica (Milne Edwards, 1840) is fully redescribed based on ovigerous females collected from Maputo Bay, Mozambique, from the branchial cavity of the fish host Selar crumenophthalmus Bloch, 1793. An identification key to the species of Norileca Bruce, 1990 is given. Furthermore, a fragment of the mitochondrial cytochrome oxidase I (COI) gene from N. indica was sequenced for the first time. This is the first molecular characterisation of a species of Norileca.     

Disruption of bacterial quorum sensing: an unexplored strategy to fight infections in aquaculture

Disease outbreaks—some of them caused by pathogenic bacteria—are considered to be one of the largest constraints to development of the aquaculture sector. So far, antibiotics and disinfectants have only had limited success in the prevention or cure of aquatic disease. Moreover, the frequent use of biocides, especially in subtherapeutic doses, is leading to the rapid development of resistance. Therefore, there is an urgent need to develop alternative ways to control infections caused by bacterial pathogens in aquaculture. Many of these pathogens are found to control virulence factor expression by a cell-to-cell communication system. Hence, disruption of bacterial quorum sensing has been proposed as a new anti-infective strategy and several techniques that could be used to disrupt quorum sensing have been investigated. These techniques comprise (1) the inhibition of signal molecule biosynthesis, (2) the application of quorum sensing antagonists (including natural occurring as well as synthetic halogenated furanones, antagonistic quorum sensing molecules and undefined exudates of higher plants and algae), (3) the chemical inactivation of quorum sensing signals by oxidised halogen antimicrobials, (4) signal molecule biodegradation by bacterial lactonases and by bacterial and eukaryotic acylases and (5) the application of quorum sensing agonists. The few reports that deal with disruption of quorum sensing of aquatic pathogens, together with the results obtained with human and plant pathogens, indicate that this new approach has potential in fighting infections in aquaculture. However, before this new strategy can be applied in aquaculture, the impact of quorum sensing disruption on the virulence of aquatic pathogens and the impact of the proposed quorum sensing disrupting techniques on the aquaculture system of interest should be studied in more depth.     

Characterization of freshwater pearl mussel (Margaritifera margaritifera) riverine habitat using River Habitat Survey data

• 1. The feasibility of using River Habitat Survey (RHS) data to describe freshwater pearl mussel (Margaritifera margaritifera) macrohabitat in the River Spey, north‐east Scotland, was investigated.
• 2. Mussels were found to be positively associated with a number of RHS variables. These included: boulder/cobble river bed substrates, broken/unbroken standing waves (channel flow types), aquatic liverworts/mosses/lichens and broadleaf/mixed woodland/bankside tree cover. Negative associations with gravel‐pebble/silt substrates and emergent reeds/sedges/herbs were also found.
• 3. Two binary logistic regression models, based on seven and four variables, respectively, were constructed in order to predict the presence/absence of mussels at any given site. Predictive success rates of 83% and 78% were achieved.
• 4. Another binary logistic regression model, based on four variables, was constructed in order to predict the occurrence of ‘optimal’ M. margaritifera habitat (overall mussel densities ≥ 1 m^?2). A predictive success rate of 83% was achieved.
• 5. The results indicate two potentially important applications of RHS for the conservation management of M. margaritifera: (1) for monitoring the effects of physical changes on extant mussel beds (and predicting their effects on mussel populations), and (2) for determining the habitat suitability of historically occupied sites for re‐introductions.

Copyright © 2003 John Wiley & Sons, Ltd.     

Quality costs in intensive fish culture: an analysis of African catfish farms in The Netherlands

A quality cost analysis was performed with the cooperation of six full-time African catfish, Clorias gariepinus, farmers in The Netherlands. The relative distribution of the quality costs does not fit a common quality cost model. Possible explanations for this observation are the absence of (1) feedback from customers and (2) well-defined quality criteria. The results show that it is likely that a considerable reduction in quality costs can be achieved with respect to sorting and rewatering. A further reduction is possible if agreement on quality criteria for African catfish can be reached.     

Genes required for mitotic spindle assembly in Drosophila S2 cells

The formation of a metaphase spindle, a bipolar microtubule array with centrally aligned chromosomes, is a prerequisite for the faithful segregation of a cell's genetic material. Using a full-genome RNA interference screen of Drosophila S2 cells, we identified about 200 genes that contribute to spindle assembly, more than half of which were unexpected. The screen, in combination with a variety of secondary assays, led to new insights into how spindle microtubules are generated; how centrosomes are positioned; and how centrioles, centrosomes, and kinetochores are assembled.     

I plasma concentrations of adrenocorticotrophic hormone and alpha-melanocyte-stimulating hormone in ferrets (Mustela putorius furo) with hyperadrenocorticism

OBJECTIVE: To determine plasma concentrations of adrenocorticotrophic hormone (ACTH) and alpha-melanocyte stimulating-hormone (alpha-MSH) in healthy ferrets and ferrets with hyperadrenocorticism. ANIMALS: 16 healthy, neutered, privately owned ferrets, 28 healthy laboratory ferrets (21 sexually intact and 7 neutered), and 28 ferrets with hyperadrenocorticism. PROCEDURES: Healthy ferrets were used for determination of reference plasma concentrations of ACTH and a-MSH. Diagnosis of hyperadrenocorticism was made on the basis of history, clinical signs, urinary corticoid-to-creatinine ratios, ultrasonography of the adrenal glands, and macroscopic or microscopic evaluation of the adrenal glands. Blood samples were collected during isoflurane anesthesia. Plasma concentrations of ACTH and alpha-MSH were measured by radioimmunoassay. RESULTS: Plasma concentrations of ACTH in 23 healthy neutered ferrets during the breeding season ranged from 4 to 145 ng/L (median, 50 ng/L). Plasma concentrations of alpha-MSH in 44 healthy neutered or sexually intact ferrets during the breeding season ranged from < 5 to 617 ng/L (median, 37 ng/L). Reference values (the central 95% of the values) for ACTH and alpha-MSH were 13 to 100 ng/L and 8 to 180 ng/L, respectively. Plasma concentrations of ACTH and alpha-MSH in ferrets with hyperadrenocorticism ranged from 1 to 265 ng/L (median, 45 ng/L) and 10 to 148 ng/L (median, 46 ng/L), respectively. These values were not significantly different from those of healthy ferrets. Plasma ACTH concentrations of sexually intact female ferrets in estrus were significantly higher than those of neutered females. CONCLUSIONS AND CLINICAL RELEVANCE: Ferrets with hyperadrenocorticism did not have detectable abnormalities in plasma concentrations of ACTH or alpha-MSH. The findings suggest that hyperadrenocorticism in ferrets is an ACTH and alpha-MSH-independent condition.     

The basics of bio-flocs technology: The added value for aquaculture

The expansion of the aquaculture production is restricted due to the pressure it causes on the environment by the discharge of waste products in the water bodies and by its dependence on fish oil and fishmeal. Aquaculture using bio-flocs technology (BFT) offers a solution to both problems. It combines the removal of nutrients from the water with the production of microbial biomass, which can in situ be used by the culture species as additional food source. Understanding the basics of bio-flocculation is essential for optimal practice. Cells in the flocs can profit from advective flow and as a result, exhibit faster substrate uptake than the planktonic cells. The latter mechanisms appear to be valid for low to moderate mixing intensities as those occurring in most aquaculture systems (0.1–10 W m^− 3). Yet, other factors such as dissolved oxygen concentration, choice of organic carbon source and organic loading rate also influence the floc growth. These are all strongly interrelated. It is generally assumed that both ionic binding in accordance with the DLVO theory and Velcro-like molecular binding by means of cellular produced extracellular extensions are playing a role in the aggregation process. Other aggregation factors, such as changing the cell surface charge by extracellular polymers or quorum sensing are also at hand. Physicochemical measurements such as the level of protein, poly-β-hydroxybutyrate and fatty acids can be used to characterize microbial flocs. Molecular methods such as FISH, (real-time) PCR and DGGE allow detecting specific species, evaluating the maturity and stability of the cooperative microbial community and quantifying specific functional genes. Finally, from the practical point of view for aquaculture, it is of interest to have microbial bio-flocs that have a high added value and thus are rich in nutrients. In this respect, the strategy to have a predominance of bacteria which can easily be digested by the aquaculture animals or which contain energy rich storage products such as the poly-β-hydroxybutyrate, appears to be of particular interest.     

Landscape geological age explains large scale spatial trends in oribatid mite diversity

Landscape Ecology - To understand the overwhelming species richness in soil the focus of attention has traditionally been on local soil conditions, such as physical and chemical characteristics....