Possible involvement of the ampullary electroreceptor system in detection of frequency-modulated electrocommunication signals in Eigenmannia

Behavioral and electrophysiological experiments were conducted to examine whether frequency-modulated electrocommunication signals are detected by the ampullary electroreceptor system in Eigenmannia. First, frequency-modulated electric organ discharges were found to contain a low-frequency component that could be detected by the ampullary system. Second, fish were successfully trained to distinguish a frequency-modulated signal, which contained a low-frequency component as in natural signals, from an artificial signal in which the low-frequency component was eliminated but still modulated in frequency. Subsequently, the trained fish responded without reinforcement to a low-frequency sinusoidal signal which mimicked the low-frequency component in the frequency-modulated signal, suggesting that the fish used the ampullary system to detect frequency modulation. Finally, physiological recording from ampullary afferent fibers demonstrated that they respond to frequency-modulated signals as predicted from the signal's low-frequency component. Electrophysiological study also showed that detection of frequency modulation by the ampullary system is immune to the presence of other constant electric organ discharges. Accepted: 28 June 1998     

Theamylase gene-enzyme system of fishes

Summary Amylases from the mosquitofish (Gambusia affinis holbrooki, Pisces: Poeciliidae) and rat were purified and compared withDrosophila amylases in terms of structure and function. At the structural level, amino acid compositions of the three amylases were compared. At the functional level, amylase activities were compared on various substrates and in the presence of inhibitors.While the amylases from all three organisms had properties typical of alpha-amylases, both structural and functional differences were observed. Using resemblance coefficients of distance and similarity from numerical taxonomy, it was determined that the amylases from the rat andDrosophila were more similar to each other than either was to amylase from the mosquitofish, and that structural differences between the amylases did not reflect functional differences, i.e. there was no correlation between amylase structural and functional distances.     

Renin-angiotensin system in antarctic fishes

• 1.1. The presence of a renin-angiotensin-like system has been investigated in the Antarctic fishes Chionodraco hamatus (Fam. Channichthydae) and Pagothenia (Trematomus) bernacchii (Fam. Notothenidae).
• 2.2. A renin-like activity is present in plasma and kidney of both the white blooded (Chionodraco) and the red blooded (Pagothenia) species.
• 3.3. An angiotensin converting enzyme-like activity has been demonstrated in plasma, gills and kidneys of both species. The activity is inhibited by high temperature.
• 4.4. From our data a renin-angiotensin-like system is present in the Antarctic fishes studied but the cascade of enzymes is active only at low temperatures.

     

The auditory system of cartilaginous fishes

Reviews in Fish Biology and Fisheries - Cartilaginous fishes (Chondrichthyes), including sharks, skates, rays, elephant fishes and chimaeras, have been in existence for over 400 million years and...     

Sex differences in the electrocommunication signals of the electric fish Apteronotus bonapartii

The South American weakly-electric knifefish (Apteronotidae) produce highly diverse and readily quantifiable electrocommunication signals. The electric organ discharge frequency (EODf), and EOD modulations (chirps and gradual frequency rises (GFRs)), vary dramatically across sexes and species, presenting an ideal opportunity to examine the proximate and ultimate bases of sexually dimorphic behavior. We complemented previous studies on the sexual dimorphism of apteronotid communication signals by investigating electric signal features and their hormonal correlates in Apteronotus bonapartii, a species which exhibits strong sexual dimorphism in snout morphology. Electrocommunication signals were evoked and recorded using a playback paradigm, and were analyzed for signal features including EOD frequency and the structure of EOD modulations. To investigate the androgenic correlates of sexually dimorphic EOD signals, we measured plasma concentrations of testosterone and 11-ketotestosterone. A. bonapartii responded robustly to stimulus playbacks. EODf was sexually monomorphic, and males and females produced chirps with similar durations and amounts of frequency modulation. However, males were more likely than females to produce chirps with multiple frequency peaks. Sexual dimorphism in apteronotid electrocommunication signals appears to be highly evolutionarily labile. Extensive interspecific variation in the magnitude and direction of sex differences in EODf and in different aspects of chirp structure suggest that chirp signals may be an important locus of evolutionary change within the clade. The weakly-electric fish represent a rich source of data for understanding the selective pressures that shape, and the neuroendocrine mechanisms that underlie, diversity in the sexual dimorphism of behavior.     

Sex differences in the electrocommunication signals of Sternarchogiton nattereri (Gymnotiformes: Apteronotidae)

In this study we examined electrocommunication behavior in Sternarchogiton nattereri (Apteronotidae), a weakly electric fish from South America. We focused on variation between females and males lacking external dentition and used playbacks of simulated conspecifics to elicit chirps (modulations of their electric organ discharge, EOD). Chirp responses were not affected by the frequency of the playback stimulus. EOD frequency, chirp rate, and chirp duration were not sexually dimorphic; however, the amount of chirp frequency modulation was significantly greater in toothless males than in females. These results reinforce that sex differences in chirp structure are highly diverse and widespread in the Apteronotidae.     

On the micro-circulatory system of the gills of certain freshwater teleostean fishes

The micro-circulatory system of the lamellae is in the form of a network of more or less parallel blood channels. A row of pillar cells separates two contiguous blood channels. All the pillar cells are situated in the same plane between the upper and lower basement membranes to which they remain fixed in position by means of columns. Histochemical investigations show that the basement membrane as well as the columns are collagenous in nature. Though both basement membranes and the columns are PAS positive (magenta colour), reticulin is not present as they do not respond to silver techniques. The development of new blood channels in the micro-circulatory system of Channa striatus has been studied. They arise as buds from the wall of the pre-existing vessels. There is some evidence to show the possible transformation of the smooth muscle cells of the tunica media of blood vessels into the pillar cells of the micro-circulatory system. Various aspects of the physiology of the micro-circulatory system of the gills have been discussed.     

Photodynamic potentialities of some phenothiazine derivatives

Summary The quantum yields of fluorescence and phosphorescence and the triplet lifetimes were determined for 29 phenothiazine derivatives; the _p values are varying from 0.2 to 1. The irradiation of phenothiazine derivatives in aerated solutions yields from the triplet state to the formation of singlet oxygen and more especially of superoxide ions and cation-radicals characteristic of the dye. Relative values of the formation rate were determined for these two mechanisms. Production of cation-radicals was correlated with phototoxicity in vivo. Chlorination enhances the two phenomena and acetylation reduces to nothing. A maximum value was estimated for the quantum yield of photoionization.     

Parasite fauna in salmonidean fishes from the Paanaiarvi-Olanga lake-river system

The data on parasite fauna in the brown trout Salmo trutta, white fish Coregonus lavaretus, and grayling Thymall thymallus from the Paanajarvi-Olanga lake-river system (White Sea basin) are presented. As like-river systems in this area remain in natural conditions, without any anthropogenic pressure, the parasite fauna in salmonoideans from these water bodies had not been changed and has an archetypical state. The parasite fauna core is established in fishes aged 3+. Parasite species forming the core of the parasite fauna infected the brown trout, grayling and whitefish in different degree.     

The taste system in fishes and the effects of environmental variables

The adaptability of the taste system in fish has led to a large variety in taste bud morphology, abundance and distribution, as well as in taste physiology characteristics in closely related species with different modes of life and feeding ecology. However, the modifications evoked in the sense of taste, or gustation, particularly during ontogeny when fishes are subject to different environmental variables, remain poorly studied. This review paper focusses on current knowledge to show how plastic and resistant the taste system in fishes is to various external factors, linked to other sensory inputs and shifts in physiological state of individuals. Ambient water temperature is fundamental to many aspects of fish biology and taste preferences are stable to many substances, however, the taste-cell turnover rate strongly depends on water temperature. Taste preferences are stable within water salinity, which gives rise to the possibility that the taste system in anadromous and catadromous fishes will only change minimally after their migration to a new environment. Food-taste selectivity is linked to fish diet and to individual feeding experience as well as the motivation to feed evoked by attractive (water extracts of food) and repellent (alarm pheromone) odours. In contrast, starvation leads to loss of aversion to many deterrent substances, which explains the consumption by starving fishes of new objects, previously refused or just occasionally consumed. Food hardness can significantly modify the final feeding decision to swallow or to reject a grasped and highly palatable food item. Heavy metals, detergents, aromatic hydrocarbons and other water contaminants have the strongest and quickest negative effects on structure and function of taste system in fish and depress taste perception and ability of fishes to respond adequately to taste stimuli after short exposures. Owing to phenotypic plasticity, the taste system can proliferate and partially restore the ability of fishes to respond to food odour after a complete loss of olfaction. In general, the taste system, especially its functionality, is regarded as stable over the life of a fish despite any alteration in their environment and such resistance is vital for maintaining physiological homeostasis.     

Carbohydrase activity in the digestive system of some teleost fishes.

The activity of carbohydrases in Puntius sophore (Ham.), Channa gachua (Ham.) and Cirrhinus mrigala (Ham.) has been studied. The carbohydrases have been found in the stomach, intestinal bulb, intestine, pyloric caeca and the hepato-pancreas. The hepatopancreas is the main site of production of these enzymes and it is in this organ and the intestine that their activity is highest. Their pH optimum lies between 5.4 and 6.4. The enzyme equipment in the teleost is adapted to their respective food and feeding habits both qualitatively and quantitatively. In Puntius (omnivorous) and Cirrhinus (herbivorous) all three carbohydrases, namely amylase (EC 3.2.1.1.), sucrase (EC 3.2.1.26.) and raffinase, while in Channa (carnivorous) only amylase and sucrase have been found to be active. In Cirrhinus mrigala, which is predominantly a herbivorous species, the concentration of carbohydrases is higher than those in the other two fishes.     

Caste developmental potentialities in the termite Nasutitermes novarumhebridarum

The normal development pathway and caste system of Nasutitermes novarumhebridarum (N. & K. Holmgren) (Isoptera; Termitidae) conform to the general Nasutitermes pattern. Queen-removal experiments in N. novarumhebridarum resulted in the production of replacement reproductives derived from workers (ergatoids), but never from the sexual brood (nymphs and alates). Three moults are necessary to complete the tranformation from the worker to the ergatoid. This pathway is longer than those previously konwn in other termites, in which two moults are sufficient. In a colony with functional ergatoids, some nymphs gave rise to worker-like individuals. The caste potentialities of N. novarumhebridarum differ from those of the sympatric species, N. princeps and N. polygynus, in which imaginal replacement reproductives are easily obtained. Colony reproduction in N. novarumhebridarum seems to be accomplished exclusively by independent alate founders, which colinize massive, but finite and widely spaced resoures such as dead or damaged tree trunks. N. princeps and N. polygynus societies abundantly use colony budding to expand their territory, and exploit various sources of dead wood scattered over their foraging range. We suggest that N. novarumhebridarum caste potentialities are adapted to channelling a maximum of resources into the production of dispersing alates that can colonize new nest sites.

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Résumé Les voies de développement et le système de castes chez Nasutitermes novarumhebridarum sont conformes au schéma général du genre Nasutitermes. L'enlèvement expérimental de la reine chez N. novarumhebridarum entraîne le développement de sexués de remplacement à partir d'ouvriers (ergatoïdes), mais jamais à partir de la lignée sexuée (nymphes et ailés). La transformation de l'ouvrier en ergatoîde fonctionnel nécessite trois mues. Ce développement est plus long que ceux décrits précédemment chez d'autres termites, où deux mues sont suffisantes. Dans une société où se sont développés des ergatoïdes fonctionnels, quelques nymphes se sont transformées en individus rappelant les ouvriers. Les potentialités des castes de N. novarumhebridarum diffèrent de celles des espèces sympatriques N. princeps et N. polygynus, chez lesquelles des sexués de remplacement imaginaux pauvent être obtenus aisément. La reproduction des sociétés de N. novarumhebridarum semble s'effectuer uniquement par des ailés essaimants, qui colonisent des sources de nourriture massives, mais limitées et largement espacées, tels les troncs d'arbres morts ou endomagés. N. princeps et N. polygynus étendent fréquemment leurs territoires par le bourgeonnement de nouvelles sociétés, et exploitent des sources de bois mort variées, dispersées dans leur champ d'exploitation. Nous suggérons que les potentialités des castes chez novarumhebridarum sont adaptées pour diriger un maximum de ressources vers la production d'ailés qui se dispersent et peuvent ainsi coloniser de nouveaux sites favorables.

     

Principles of the maximum development of the reserve potentialities of the bone marrow CFUf system following exposure to ionizing radiation

In this work, the regularities in the occurrence of a highly pronounced postirradiation increase in CFUf of bone marrow (CFUf "peak") were investigated and quantitative approaches permitting to predict absolute CFUf "peak" values at various radiation doses developed.     

The hemoglobin system of Antarctic and non-Antarctic notothenioid fishes

Studies of the hemoglobin system of fish of the suborder Notothenioidei have been extended to non-Antarctic species of Pseudaphritis urvillii and Notothenia angustata. The two species belong to families that were the first to diverge within the suborder. The degree of amino acid sequence identity with Antarctic notothenioids and other non-Antarctic fish species is analyzed with respect to phyletic and ecological diverence.