Cytoskeletal dynamics of the teleostean fin ray during fin epimorphic regeneration

Teleost fishes can regenerate their fins by epimorphic regeneration, a process that involves the transition of the formerly quiescent tissues of the stump to an active, growing state. This involves dynamic modifications of cell phenotype and behavior that must rely on alterations of the cytoskeleton. We have studied the spatial and temporal distribution of three main components of the cytoskeleton (actin, keratin and vimentin) in the regenerating fin, in order to establish putative relationships between cell cytoskeleton and cell behavior. According to our results, the massive rearrangement undergone by the epidermis right after injury, which takes place by cell migration, correlates with a transient down-regulation of keratin and a strong up-regulation of actin in the epidermal cells. During the subsequent epidermal growth, based on cell proliferation, keratin normal pattern is recovered while actin is down-regulated, although not to normal (quiescent) levels. The epidermal basal layer in contact with the blastema displays a particular cytoskeletal profile, different to that of the rest of the epidermal cells, which reflects its special features. In the connective tissue compartment, somatic cells do not contain vimentin, but keratin, as intermediate filament. Proliferative and migrative activation of these cells after injury correlates with actin up-regulation. Although this initial activation does not involve keratin down-regulation, blastemal cells were later observed to lack keratin, suggesting that such cytoskeletal modification might be needed for connective tissue cells to dedifferentiate and form the blastema. Cell differentiation in the newly formed, regenerated ray is accompanied by actin down-regulation and keratin up-regulation.     

Male mate choice in the gynogenetic–sexual complex of crucian carp,<Emphasis Type="Italic"> Carassius auratus</Emphasis>

The asexual all-female Japanese crucian carp, Carassius auratus langsdorfii (Teleostei: Cypriniformes), reproduces gynogenetically, relying on the sperm of males of the sexual "host," C. auratus subspp. Theoretically, frequency-dependent mating preference of males to conspecific females can lead to the coexistence of asexual and sexual fish, if all else is equal. Our specific questions are whether males prefer conspecific females over asexual females and whether individuals show dominance hierarchies that potentially cause frequency-dependent mating preference. In an individual choice experiment, a tank was partitioned into three compartments with the middle one for a single male and the two outer ones for a sexual and an asexual female. The males of C. auratus bürgeri demonstrated a significant preference for ovulated conspecific females over ovulated asexual females. In contrast, in a group mating experiment, a single experimental tank included two males, a sexual female, and an asexual female together, and males chased and mated with both asexual and sexual females equally. Male mate preference was weak in group mating, which is typical in natural populations. Males and females of crucian carp showed no apparent agonistic behavior to each other in the group mating experiment. This is different from other gynogenetic complexes with the dominance hierarchy of males showing strong frequency-dependent mating preference (e.g., Poeciliopsis). We conclude that male mate preference is unlikely to be a strong frequency-dependent force maintaining the coexistence of asexual–sexual complexes of Japanese crucian carp. Received in revised form: 5 February 2001 Electronic Publication     

Phylogenetic Relationships Among Microsporidia Based on rDNA Sequence Data, With Particular Reference to Fish-Infecting Microsporidium Balbiani 1884 Species.

Recently, large discrepancies have been identified between microsporidian systematics based on molecular and traditional characteristics. In the current study the 530f-580r region of the rRNA gene of eight microsporidian species was cloned and sequenced. Included were two unclassified species of Microsporidium Balbiani, 1884 and an unidentified microsporidian that infects the musculature of different sea bream species. Sequence identities in excess of 98% indicated that these three species almost certainly are members of the same genus. Phylogenetic analyses of all microsporidian sequence data available for this region of the gene (20 species) and for partial small subunit sequences (51 species of 21 genera) revealed these species to be distinct from the family Pleistophoridae Doflein, 1901 and closely related them to the genus Sproguea Weissenberg, 1976. This clade was found to comprise a sister taxon to that containing the vast majority of fish-infecting species. Broad cladistic divisions were found between terrestrial insect-infecting and fish-infecting species, which together are distant from the aquatic insect-infecting microsporidia. The rRNA gene of certain fish-infecting genera was found to be more highly conserved than previously reported. This has implications for its utility in diagnostic assays and phylogenetic studies at, or close to, the species level.     

Development and achievements of marine fish-rearing technology in France over the last 15 years

This paper summarises the development, over the last15 years, of the rearing techniques of the two mostimportant finfish cultivated in France: the sea bass,Dicentrarchus labrax and the sea bream, Sparus auratus.The historical background and the main achievementsthat led to the present industrial production levelare summarised i.e. control of environmentalfactors, intensification of rearing densities, simplification and improvement of feeding sequences,resolution of the main skeletal deformities,utilisation of closed recirculating systems, etc...The new research orientations that are presentlyinvestigated to continue the promotion of marine fishfarming in France are also discussed.     

Effect of exogenous lactate on pulsation rate and oxygen consumption of the isolated heart of thermally acclimated goldfish

1. 1.Pulsation rate as well as oxygen consumption of 10°C-acclimated golfish heart was higher in the lactate medium than in the glucose medium, but such differences was indistinct in 25°C-acclimated fish.

2. 2.Lactate and glycogen content and its consumption of the isolated heart dependent on the acclimation temperature.

3. 3.These results suggest that temperature acclimation induces change in availability of the substrates to the heart.

Immunohistochemical demonstration of calbindin-D 28K (CABP28K) in the spinal cord motoneurons of teleost fish

Summary The distribution and localization of the calciumbinding protein, calbindin-D 28K (CaBP28K), in the spinal cord motoneurons of larvae of the teleost fish, Apteronotus leptorhynchus (Gymnotidae) and Pollimyrus isidori (Mormyridae), and in the adult goldfish, Carassius auratus (Cyprinidae), were determined by means of immunohistochemistry. Sections of whole larvae and goldfish spinal cord were reacted with a polyclonal antibody to rat renal CaBP28K. CaBP28K was located by the PAP technique (Sternberger). It was found in the soma, dendrites, axons and axon terminals of spinal motoneurons but not in those of electromotoneurons of Apteronotus leptorhynchus, whereas it occurred in both motoneurons and electromotoneurons of the larval electric organ of Pollimyrus isidori. In these species CaBP28K was also present in the electromotoneuron axon terminals that make synaptic contacts with the pedicles of the electrocytes. In adult Carassius auratus, CaBP28K was found in the soma, dendrites and axons of certain spinal motoneurons. The results indicate that, in teleosts, the motoneurons containing CaBP28K may represent a well-defined population within the spinal cord; the role of this protein in these cells remains to be determined.     

Cytoskeletal organization and collagen orientation in the fish scales

Summary Immunofluorescence and electron microscopy were used to analyze the relationships between the organization of collagen fibrils in elasmoid scales, and the orientation of microtubules and actin microfilaments in the scleroblasts producing this collagenous stroma. Attention was focused on the basal plate of the scales because of the highly ordered three-dimensional arrangement of the collagen fibrils in superimposed plies forming an acellular plywood-like structure. The collagen fibrils are synthesized by the scleroblasts forming a monolayered pseudo-epithelium, the hyposquama, at the lowest surface of the scale. Fully developed scales with a low collagen deposition rate were compared with regenerating scales active in fibrillogenesis. When an ordered array of the collagen fibrils is found, the innermost collagen fibrils are coaligned with microtubules and actin microfilaments. Thus, because of this coalignment, microtubules and actin microfilaments of the hyposquamal scleroblasts are subjected to consecutive alterations during the formation of the plies of the basal plate. The sequence of events when the collagen fibrils change their direction from one ply to the other in the basal plate is deduced from immunofluorescence and phase-contrast-microscopic observations. During the formation of the orthogonal plywood-like structure in the regenerating scales, first microtubules may change their curse with a rotating angle of about 90°; then, actin microfilaments are disorganized and reorganized by interacting mechanically with the microtubules with which they are coaligned. Collagen fibrils are synthesized in a direction that is roughly perpendicular to that of the preceding ply. The unknown signals inducing the change in direction of the cytoskeleton may be transmitted throughout the hyposquama via gap junctions.This work is dedicated to the memory of Jacques Escaig     

Size-dependent mortality of red sea bream, Pagrus major, juveniles released with fluorescent otolith-tags in News Bay, Japan

Totals of 2^.67 x 10⁵ and 7^.56 x 10⁵ juvenile red sea bream of three size groups (10, 20 and 40 mm t.l.) marked with a fluorescent substance in the otolith were released in News Bay, Oita Prefecture, Japan, in July 1987 and June 1988, respectively; the aim was to estimate growth and mortality of different developmental stages.
Of fish released in 1987 and 1988, 10 618 and 4413, respectively were recaptured during those two years. Released fish remained in the bay until the end of summer, and afterwards migrated out towards open waters. Fish of the 40-mm group released in 1987 grew to over 200 mm t.l. in one year. Mean growth rate for 19 days after release was higher in the 40-mm group (0^.87 mm day⁻¹) than in the 20-mm group (0^.74mm day⁻¹). Survival rates over 19 days were 59^.0 and 10^.1 % for 40-mm and 20-mm fish, respectively, in 1987, and those over 30 days were 69^.2, 3^.3 and 0^.0% for 40-mm, 20-mm and 10-mm fish, respectively, in 1988.
Cannibalism was indicated by the presence of marked otoliths for 20-mm fish in the stomachs of a few 40-mm individuals recaptured 2 days after release. Size-dependent growth and size-selective mortality were both noted in juvenile red sea bream, i.e. the relative size differential between larger and smaller individuals was maintained in the period between marking and recapture, and mortality was inversely proportional to size.     

鲫鱼(Carassius auratus)外周血细胞显微和亚显微结构的观察

本文记载了用光镜和电镜观察鲫鱼外周血细胞所得的结果。 用光镜观察以Wright氏染液染色的血涂片,可区分出下列各种类型的血细胞:红血细胞,淋巴细胞,血栓细胞,单核细胞,中性、嗜酸和嗜碱粒细胞。此外,在外周血液中还可以看到少量未成熟的红血细胞。 在外周血液中,嗜酸和嗜碱粒细胞的数量极少。但在头肾和脾等造血组织中这类细胞的数量较多。 鲫鱼外周血液中各种血细胞的超微结构,基本上和人类以及其他鱼类相应血细胞的超微结构相似。     

Real‐time PCR validation of visually identified snapper Chrysophrys auratus (Sparidae) eggs

In this study, a total of 212 eggs were visually identified as snapper Chrysophrys auratus. Real‐time PCR confirmed visual identification in 69% of cases but corroboration varied widely among plankton samples. The use of molecular tools to support visual identification prior to adopting daily egg production stock assessment methods should be considered.