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Notes: Fed and starved yearling roach, Rutilus rutilus. were subjected to a sublethal copper contamination of 80 μg Cu × l−1 for 7 days. Copper accumulation was determined by atomic absorption spectroscopy. In both fed and starved fishes, the gill tissues showed significant uptake of copper, while the liver tissues of only starved specimens showed significant accumulation. Refeeding roach after 7 days of starvation and contamination resulted in a significant decrease of liver copper content. No copper release from the liver occurred if, after cessation of exposure, starvation was continued. Analysis of liver ultrastructure demonstrated no pathological lesions or copperspecific alterations. Cellular changes represented combined influences of nutrition and of copper. Qualitative as well as quantitative results provide evidence that the nutritional status of a fish is of great importance in modifying its response to sublethal copper contamination.

Notes: Using histochemical methods, morphofunctional aspects of the alimentary tract of larval coregonids were investigated. Larvae of Coregonus lavaretus were reared for 34 days with either zooplankton or one of two dry diets. Ontogeny, localization and diet-related modifications of the following enzymes were examined: trypsin (luminal digestion), aminopeptidase, maltase, alkaline phosphatase (brush border-bound digestion) and unspecific esterase (intracellular nutrient processing). All of the enzymes studied were present in 13-day-old larvae. Except for the intracellularly located unspecific esterase, there was an ontogenetic enhancement of enzyme staining intensities accompanied by a significant increase in the volume of the intestinal mucosa. Enzyme activities differed within and between intestinal regions. This finding suggests that a spatial gradient of nutrient breakdown and absorption already exists in the morphologically and physiologically incompletely developed digestive system of larval coregonids. Digestive enzyme activities were modified in response to the dietary regimen. There was no obvious correlation between enzymic response and growth performance of the larvae.

Notes: Gonadogenesis of zebrafish Danio rerio was investigated by means of light microscopy to test the suitability of gonad histology as an endpoint in hazard assessment of endocrine-active compounds. At age 2 weeks post-fertilization (pf), primordial germ cells were found in a dorsocaudal position in the body cavity. At 4 weeks pf, the majority of the fish (86%) possessed paired gonads with meiotic germ cells; these gonads represented presumptive ovaries. At week 5 pf, 87% of the fish examined had ovaries with perinucleolar oocytes. Further development of the gonads in female zebrafish up to week 11 pf was characterized by an increase in gonad size as well as in the number and size of perinucleolar oocytes. Starting with week 5, some fish showed alterations of gonad morphology, including a decrease in the number and size of the oocytes, an enhanced basophilia and irregular shape of the oocytes, and finally their degeneration into residual bodies. With the decline in oocyte number, stromal cells became more numerous and they infiltrated the gonadal matrix. In several 7 week-old zebrafish with altered gonadal morphology, enhanced numbers of gonial cells arranged in cyst-like groups appeared. These gonads were interpreted as presumptive testes. In one fish out of 32 individuals examined, spermatocytes were detected, in addition to the gonial cells. During the subsequent weeks, the percentage of fish showing early testes with spermatogonia, spermatocytes and spermatids increased and reached 40% at 11 weeks pf. The sequence of gonadal alterations taking place in some of the individuals from week 5 pf onwards was interpreted to reflect the transition of protogynic ovaries into testes. The developmental pattern described identifies zebrafish to be a juvenile hermaphrodite. The results of this study are of relevance for the use of gonadal histopathology as endpoint in endocrine disruption testing, particularly in order to avoid false diagnoses of ‘intersex gonads’ in zebrafish.

Notes: A comparative study of larval growth in the different species of the genus Clarias in different regions revealed that in spite of strong differences in egg and larval size, the growth potential was quite similar. Differences in growth between species and regions were strongly correlated with the applied feeding strategy, the applied growth parameter and period of measuring. To evaluate feeding strategies, standardized procedures for measuring growth are needed. Recalculating the results of the mentioned study according to these standardized procedures revealed that both in India and Indonesia, the growth rate of C. batrachus larvae was too low. This is probably due to low feeding levels in India and premature weaning in Indonesia.The basic biology and nutritional physiology of the larvae of C. gariepinus have been studied extensively. At the start of exogenous feeding, the larvae have an advanced digestive system with a functional pancreas, liver and nutrient absorption capabilities, but lack a functional stomach. The advanced digestive system is further exemplified by the development of the enzymatic complex. Probably because of the rapid development of the digestive system, feeding live food organisms is mostly practiced for a few days only and is soon replaced by wet and/or dry diets. It is hypothesized that the requirement of live food or specific larval diets during the first days of exogenous feeding is related to the absence of pepsin digestion during this period. Further optimization of the feeding strategies should focus on this conclusion.

Notes: Epidermal mucous cells of fish are affected by acidified water. This study provides baseline data of brown trout, Salmo trutta, to distinguish environment-related alterations of mucous cells from changes caused by biological (tissue heterogeneity, ontogeny) or methodological (fixation and histochemical procedures) factors. Knowledge of such factors is unconditionally required before acid-related mucous cell alterations can be discerned.〈section xml:id="abs1-2"〉〈title type="main"〉ZusammenfassungAuf dem Weg zu einer Verwendung epidermaler Schleimzellen in Freilanduntenuchungen zum Säurestreß bei FischenDie Schleimzellen in der Haut von Fischen verändern sich unter dem Einfluß von saurem Wasser. Die vorliegende Studie liefert für die Bachforelle, Salmo trutta, Grundlagendaten, um umweltbezogene Schleimzellenveränderungen unterscheiden zu können von Veränderungen, die biologischen (Gewebe-heterogenität, Ontogenie) oder methodischen (Fixierungs-und Färbeprozesse) Faktoren zuzuschreiben sind. Kenntnis derartiger Faktoren ist unersetzlich, sollen pH-induzierte Veränderungen der Schleimzellen sicher angesprochen werden.〈section xml:id="abs1-3"〉〈title type="main"〉RésuméL'utilisation de cellules muqueuses de la peau en vue du discernement du stress cause par l'eau acide chez les poissonsLes cellules muqueuses de la peau des poissons altèrent sous l'influence de l'eau acide. l'étude présente fournit des dates de base de la truite (Salmo trutta) afin de distinguer entre les altérations des cellules muqueuses, provoquées par des facteurs biologiques (hétérogénéité du tissue, ontogénie) et celles causées par des facteurs méthodiques (procès de fixation et histochimique). La connaissance des ces facteurs est indispensable avant de pouvoir discerner les altérations se référant à l'acidité.

Notes: The influence of water-borne iron (500 μg × 1-1 and 2 mg × 1-1) on the liver of Poecilia reticulata is studied by means of electron microscopy. The uptake and effect of iron is affected by a. the chemical speciation of the metal: Iron complexed with tri-polyphosphates is more deleterious than inorganic Fe3+; b. the nutritional status of the fish: In food-deprived Poecilia reticulata iron is absorbed and enhances starvation-induced liver damage. In fed animals, there is no uptake at all. Mild alterations of hepatocyte ultrastructure are attributed to an unspecific stress response.

Notes: Six different diets, commonly used in the Philippines for rearing milkfish, Chanos chanos, try, were tested by means of growth, survival and histology. These diets included:a) live food (Anemia nauplii); b) two different dry feeds; c) natural feed supplements (rice bran, egg yolk); d) a mixture of live and dry feeds. The mixed diet was found to give the best results, closely followed by live food. The dietary value of one of both artificial feeds improved with increasing age of the fish, whereas the other was clearly inadequate. The same was true for the natural compounds. Results obtained from statistical and histological analyses were congruent; the latter provided additional insights not obtained with statistic data alone.〈section xml:id="abs1-2"〉〈title type="main"〉ZusammenfassungHistologische Beobachtungen zur Aufzucht von Milchfisch, Chanos chanos, Larven, unter Benutzung verschiedener DiätenSechs verschiedene Futtersorten, die alle auf den Philippinen benutzt werden zur Aufzucht von Larven des Milchfisches, Chanos chanos, wurden mittels Wachstum, Überlebensrate und histologischer Parameter getestet. Die Diäten umfassten:a) Lebendfutter (Artemia Nauplien); b) zwei verschiedene Trockenfutter; c) natürliche Futtermittel (Reis-Kleie, Eidotter); d) eine Mischung von Lebend-und Trockennahrung. Die besten Resultate erbrachte die gemischte Diät, dicht gefolgt vom Lebendfutter. Der Nährwert eines der beiden Trockenfutter verbesserte sich mit zunehmendem Alter der Fische, während das zweite Trockenfutter eindeutig nicht geeignet war. Letzteres traf auch für die narürlichen Futtermittel zu. Statistische und histologische Befunde waren übereinstimmend, doch gewährten letztere zusätzliche Erkenntnisse, die mit den statistischen Daten allein nicht zu erhalten waren.〈section xml:id="abs1-3"〉〈title type="main"〉RésuméObservations histologiques pour l'élevage de larves de Chanos chanos avec de différentes diètesSix divers types de nourritures, utilisées sur les Philippines pour l'élevage de Chanos chanos, ont été testé selon la croissance, le coefficient de survie et de paramètres histologiques. Les diètes comprenaient: a) nourriture vivante (Anemia nauplii); b) deux types de nourritures synthétiques; c) nourriture naturelle (son du riz, du jaune d'oeuf), d) un melange de nourriture vivante et synthétique. Le meilleur résultat a apporté la diète mélangée, succédée de très près de la nourriture vivante. La valeur nutritive d'une des deux nourritures synthétiques s'améliorait avec la croissance des poissons, tandis que la deuxième des nourritures synthétiques ainsi que la nourriture naturelle étaient nettement inadéquat. Les constatations statistiques et histologiques étaient concordantes. Les constatations histologiques cependant apportaient des connaissances additionnelles qu'on aurait pas recu avec les données statistiques seules.

Notes: A field survey was carried out to study the occurrence and distribution of viruses causing diseases of major impact in fish farming, namely viral haemorrhagic septicaemia (VHS), infectious haematopoietic necrosis (IHN) and infectious pancreatic necrosis (IPN) in farmed and wild fish in Switzerland. The presence of VHS virus (VHSV), IHN virus (IHNV) and IPN virus (IPNV) in the tissue samples was tested by virus isolation in cell cultures, and subsequent virus identification by immunofluorescence. The sera were screened for anti-VHSV antibodies (VHSV-AB) using a serum plaque neutralization test with complement addition. These data were then compared with results of a similar survey performed in 1984/85, and with data from routine diagnostic work completed at the Centre for Fish and Wildlife Health (FIWI) of the University of Bern from 1978 to 2001. Sampling sites included private and government fish farms as well as natural habitats from all major river catchments in Switzerland. In 2000/01, 522 tissue samples and 1910 sera were collected from 3400 fish. In 1984/85 1239 tissue samples and 694 sera were collected from 1628 fish. During the last 24 years of routine diagnostics at the FIWI, 1776 tissue samples were examined for presence of viruses. The results of the tissue analysis from the surveys in 1984/85 and 2000/01 showed low numbers of sites with virus-positive fish (five VHSV, three IPNV and three VHSV, one IPNV, respectively) in Swiss fish farms and rivers. The sites with virus-positive fish were located throughout the country. The decline in virus-positive cases observed between the two surveys agrees with data from the routine diagnostic work of the FIWI which show a decrease in total virus isolations from approximately 35 cases per year in the late 1970s, to approximately 10 cases per year during the last 10 years. However, in 1984/85 8.3% (58 of 694 serum samples) and in 2000/01 6.3% (121 of 1910 serum samples) proved to be positive for VHSV-AB. The 58 positive samples in 1984/85 originated from 40 of 175 sites (23%) and the 121 positive samples in 2000/01 were from 84 of 217 (29%) sites. These results are indicative of a wider distribution of VHSV than expected from the results of the virus isolations.

Notes: This study presents an overview of the distribution of proliferative kidney disease (PKD) in wild and farmed fish in Switzerland based on two sources: (1) the results of routine diagnostic work at the National Fish Disease Laboratory, and (2) the results of a country-wide survey for PKD. The first case of PKD in Switzerland was diagnosed in 1979 and since 1981, a few cases have been found every year. Affected species were rainbow trout, brown trout and grayling from rivers and fish farms. Most of the diseased fish were found in the lower altitude regions of the country (Swiss midlands). A seasonal distribution of the cases was evident: PKD-positive fish occurred only from June to November withprominent peaks in August and September. Among infected fish all length classes were present, but the highest numbers of affected fish were found in the length classes 〈10 cm and 16–20 cm. The evaluation of the samples from a survey of the occurrence of PKD in 2000/2001 revealed a much broader geographical distribution of the infection than expected from routine diagnostic observations. Fish from 56 of 139 rivers analysed by histological examination were positive for parasites. Fish from 131 of these sites were examined macroscopically. Of these, trout from 45 sites showed gross alterations indicative for PKD. Most of the positive fish were found in the Swiss midlands north of the Alps. Fish from six of 65 fish farms investigated were found to be PKD-positive by histopathological analysis, and in four of these cases fish could be identified as infected on the basis of gross examination.