Physical and chemical water requirements of the white‐clawed crayfish (Austropotamobius pallipes) in western France

• 1. In France, the distribution of the native white‐clawed crayfish (Austropotamobius pallipes) is restricted, fragmented and mainly located in headwater streams. To conserve this indigenous species, it is necessary to characterize its habitat preferences.
• 2. Seven brooks in the Deux‐Sèvres Département (western France) containing wild populations of A. pallipes were studied to determine its ranges of tolerance to 19 physical and chemical water parameters. On two brooks, the Sèvre Nantaise and the Verdonnière, sites with and without A. pallipes were compared. Each site was sampled twice monthly from November 2002 to November 2004.
• 3. It was found that the white‐clawed crayfish was able to tolerate wide ranges of values of some of the measured parameters. The Magot site harboured the largest A. pallipes population (17.5 crayfish m^?2) and had dissolved oxygen concentrations as low as 4.93 mg L^?1, while water temperature rose above 20°C for several consecutive days during summer and nitrate concentrations were always found to be above 30 mg L^?1. These unusual findings could call into question the status of A. pallipes as a bioindicator of good water quality.
• 4. Principal component analyses (PCA) suggested that an increase of organic matter was a discriminant factor for the presence or absence of A. pallipes. In addition, sites with and without crayfish on the Sèvre Nantaise brook showed showed significant differences (p<0.05) in total organic carbon (TOC), and those on the Verdonnière brook in turbidity and total suspended solids (TSS).

Copyright © 2006 John Wiley & Sons, Ltd.     

Milky hemolymph syndrome associated with an intranuclear bacilliform virus in snow crab <Emphasis Type="Italic">Chionoecetes opilio</Emphasis> from the Sea of Japan

Milky hemolymph syndrome (MHS) is a previously undescribed disease in snow crab Chionoecetes opilio. Outbreaks of this disease occurred in reared and wild populations from the Sea of Japan when the water temperature was 2–3°C. The common symptom of the disease was a distinct milky or opaque coloration of the hemolymph. Some severely affected crabs also showed yellow or ivory discoloration on the ventral shell and uncalcification of the arthrodial membranes of walking legs. Histopathological changes consisted of widespread cellular degeneration characterized by enlarged nuclei with marginal hyperchromatosis and basophilic intranuclear inclusions in the interstitial connective tissues of various organs. Electron microscopy analyses of degenerated cells revealed a nonoccluded, enveloped bacilliform virus within the nuclei. The virus morphologically resembles white spot syndrome virus (WSSV) or unassigned intranuclear bacilliform viruses (IBVs) reported from other crustaceans. However, we could not detect WSSV from diseased tissues by PCR using WSSV-specific primers, and the tissues targeted by the virus differed from those targeted by IBVs. This is the first report of a virus from the genus Chionoecetes. Thus, we have tentatively designated the virus presumably associated with MHS as Chionoecetes opilio bacilliform virus (CoBV) until its relationship with other crustacean viruses can be clarified.     

First observation of herpes-like virus particles in northern pike, Esox lucius L., associated with bluespot-like disease in Ireland

Circular whitish granular lesions, 5-12 mm in diameter, were observed on the skin and fins of a wild northern pike, Esox lucius, caught in a lake in the Republic of Ireland. Histological examination of the lesions revealed hypertrophied cells in the epidermis with deeply basophilic enlarged nuclei and dark-staining granular material in the cytoplasm. Transmission electron microscopy of these cells revealed naked hexagonal herpes-like virus nucleocapsids (97 +/- 7 nm) in their nuclei while the cytoplasm contained multiple aggregates of enveloped viral particles. This is the first report of herpes-like virus particles in northern pike originating outside North America, where esocid herpesvirus-1 (EsHV-1) has previously been reported. Shared clinical, histological, morphological and epidemiological findings suggest that the observed particles in this report may also be EsHV-1.     

Lymphocystis disease virus persists in the epidermal tissues of olive flounder, Paralichthys olivaceus (Temminch & Schlegel), at low temperatures

Olive flounder artificially infected with lymphocystis disease virus (LCDV) were reared at 10, 20 and 30 °C for 60 days, to compare LCD-incidence. In the fish reared at 20 °C, lymphocystis cells appeared on the skin and fins at 35 days post-challenge, and the cumulative LCD-incidence was 80% at 60 days. High levels of LCDV, with a mean polymerase chain reaction (PCR) titre of 10⁶ PCR-U mg⁻¹ tissue, were detected in the fins and skin of LCD-affected fish at 20 °C, but were not detected in the spleen, kidney, brain and intestinal tissues of these fish. No LCD clinical signs were observed in the fish reared at 10 °C and 30 °C; however, a low level of LCDV (10³ PCR-U mg⁻¹ tissue) was detected in the fins and skin of these fish. By increasing the rearing temperature from 10 to 20 °C, lymphocystis clusters appeared on the skin and fins of the fish with no previous LCD clinical signs within 33 days after the temperature change. It was shown that permissive cells for LCDV infection exist in the epidermis of olive flounder. At low temperatures, small amounts of LCDV were able to persist over a period extended for a further 45 days in the fish epidermis, even though the fish showed no LCD clinical signs. The optimum growth temperature of LCDV is near 20 °C.     

An evaluation of fish health‐management practices and occupational health hazards associated with Pangasius catfish (Pangasianodon hypophthalmus) aquaculture in the Mekong Delta,Vietnam

This study aimed to evaluate the current status on the use of probiotics, disinfectants and antimicrobials in hatcheries, nurseries and grow‐out farms producing Pangasius catfish (Pangasianodon hypophthalmus) in the Mekong Delta, Vietnam. Semi‐structured interviews were conducted with 83 aquaculture enterprises (15 hatcheries, 32 nurseries and 36 grow‐out farms). Farmers reported use of a total of 24 different antimicrobials, e.g. for treatment of bacillary necrosis and motile aeromonad septicaemia, and a variety of disinfectants, probiotics and nutritional supplements. In contrast to small‐scale farmers, all large‐scale grow‐out farmers studied were certified and therefore had higher levels of formal education and specialized aquaculture training to diagnose and treat diseases. All farmers prepared their own medicated feed with a high risk of treatment failure, negative environmental impact from released antimicrobials and resistance development. Small‐scale farmers were at particular occupational health risks when handling antimicrobials and other chemicals, e.g. mixing medicated feed with bare hands. There is an urgent need to improve knowledge and use innovative approaches, e.g. private‐public partnerships, to assure a prudent use of chemicals, to improve capacity and access to disease diagnosis, particularly for small‐scale grow‐out farmers and nurseries. Efforts to control use of antimicrobials in aquaculture should be coordinated with the livestock and human health sectors taking an One‐Health approach.     

Incidence of white muscle disease, a viral like disease associated with mortalities in hatchery-reared postlarvae of the giant freshwater prawn Macrobrachium rosenbergii (De Man) from the south-east coast of India

Incidence of post‐larval mortalities of 30–100% was reported from commercial freshwater prawn, Macrobrachium rosenbergii (De Man) hatcheries in Andhra Pradesh and Tamil Nadu (south‐eastern states of India) since 2001. Infected postlarvae (PL) exhibited clinical symptoms with lethargy, anorexia and whitening of abdominal muscles and the disease was identified as white muscle disease (WMD). The waterborne infection of WMD was induced in the laboratory by exposing uninfected and healthy M. rosenbergii PL to the filtered muscle homogenates of the naturally infected PL, resulting in mortality that reached 99% within 10 days post infection. Histopathological examination of the infected animals revealed highly necrotic musculature. Degenerated muscle areas showed aggregations of melanized nuclei, many of which looked like inclusion bodies. Bacteriological examination of affected PL showed the presence of Staphylococcus spp. as a predominant organism, while laboratory challenge of healthy PL with this bacterial isolate did not reproduce WMD.