Effects of the light-dark cycle and scheduled feeding on behavioral and reproductive rhythms of the cyprinodont fish, Medaka, Oryzias latipes

Medaka were maintained on a 16:8 light-dark cycle and fed once daily on one of 5 different feeding schedules. The daily rhythm of agonistic behavior rapidly entrained to the scheduled feeding time and maintained this entrainment during a 3-day starvation period. In contrast the daily rhythms of egg laying and courtship stayed entrained to the L:D cycle regardless of the feeding schedule. Thus, temporal integration of this fish with its daily environment can involve multistimuli which concurrently and differentially entrain externally expressed circadian systems.     

Effects of the light-dark cycle and scheduled feeding on behavioral and reproductive rhythms of the cyprinodont fish,Medaka,Oryzias latipes

Summary Medaka were maintained on a 168 light-dark cycle and fed once daily on one of 5 different feeding schedules. The daily rhythm of agonistic behavior rapidly entrained to the scheduled feeding time and maintained this entrainment during a 3-day starvation period. In contrast the daily rhythms of egg laying and courtship stayed entrained to the L:D cycle regardless of the feeding schedule. Thus, temporal integration of this fish with its daily environment can involve multistimuli which concurrently and differentially entrain externally expressed circadian systems.We thank Mark Goodrich and Steve Huber for fish maintenance and technical assistance; and Don Dovala for aid in developing the automatic feeder. The research was funded in part by NIH, AM 25191 and NIEHS, ES No. 01985.     

Intertidal habitat: does the shore level affect the nutritional condition of the shanny (Lipophrys pholis,Teleostei, Blenniidae)?

The nutritional condition of the shanny (Lipophrys pholis, Teleostei, Blenniidae), an intertidal fish, is affected by the shore level on whihc it dwells. Depending on the altitude within the intertidal, zone access to food is restricted for a certain time. A progressive decrease in the feeding time for an individual remaining on an increasingly higher shore level leads to a poorer nutritional condition compared to an individual staying at a lower shore level. Trade-off mechanisms between the feeding time and competition for space and/or predation pressure seem to be responsible for the still high abundance ofL. pholis on the upper shore. Possible consequences for growth and reproduction as well as distribution patterns are discussed.     

Transfer and isolation effects on the feeding behaviour of the angelfish,Pterophyllum scalare

The feeding behaviour of juvenile angelfish (Pterophyllum scalare) has been used as an indicator of their recovery following handling and transfer to a new environment, both with and without conspecifics. Isolated specimens fed less readily than group-housed fish, or those transferred to the test aquaria in groups of three or five, and continued to do so for at least ten days following isolation. Feeding rank-order frequently changed following isolation, suggesting that better foragers may not take the greatest risks in isolation.     

The relationship of phosphodiesterase and cyclic AMP to the process of fluid secretion in the salivary glands of the ixodid tick Amblyomma americanum.

Phosphodiesterase (PDE) activity in the salivary glands of the female. Amblyomma americanum decreased as the tick progressed from a slow to a rapid phase of feeding, while the rate of fluid secretion increased when glands were stimulated with cyclic AMP and theophylline. Dopamine stimulated PDE activity and an 'inhibitory' factor was found in glands obtained from rapidly engorging ticks which decreased PDE activity. These findings are discussed as they relate to the process of fluid secretion by salivary glands of feeding ixodid ticks.     

Nassariid gastropods as destructive agents in preservation and fossilization of marine fishes

Experimental investigations on the feeding activity of the gastropodNassarius moestus in intertidal environments in the Sea of Cortez (Gulf of California) show them to be effective agents influencing processes of marine fish taphonomy. Time-lapse documentation reveals that potential whole-body preservation of fish carcasses is largely prevented through the rapid destruction of soft tissues, muscles, and ligaments, followed by disarticulation and subsequent disassociation of skeletal elements. Dissociated bones are subject to differential dispersal through hydrodynamic transport and physical wear through abrasion. Transformation of whole-body carcasses into thoroughly defleshed and disarticulated skeletons by large groups of scavenging snails was commonly observed to take place within one tidal cycle. The loss of information during taphonomic processes via destructive biological agents may ultimately bias the fossil record in a significant way and thus have implications for the paleoecological interpretation of fossil teleost assemblages.     

Circadian-Rhythmik und Gruppenverhalten beiLeucaspius delineatus (Pisces,Cyprinidae)

Summary In constant illumination fish groups and isolated fish exhibit a free running rhythm. The period length of the day active animals decreases with increasing light intensity and vice versa. The results correspond to the circadian rule, the validity of which has proved correct now for fish, too. The synchronization within fish groups is also influenced by socio-ecological factors.     

Transgenesis in fish

Gene transfer into fish embryo is being performed in several species (trout, salmon, carps, tilapia, medaka, goldfish, zebrafish, loach, catfish, etc.). In most cases, pronuclei are not visible and microinjection must be done into the cytoplasm of early embryos. Several million copies of the gene are generally injected. In medaka, transgenesis was attempted by injection of the foreign gene into the nucleus of oocyte. Several reports indicate that the injected DNA was rapidly replicated in the early phase of embryo development, regardless of the origin and the sequence of the foreign DNA. The survival of the injected embryos was reasonably good and a large number reached maturity. The proportion of transgenic animals ranged from 1 to 50% or more, according to species and to experimentators. The reasons for this discrepancy have not been elucidated. In all species, the transgenic animals were mosaic. The copy number of the foreign DNA was different in the various tissues of an animal and a proportion lower than 50% of F1 offsprings received the gene from their parents. This suggests that the foreign DNA was integrated into the fish genome at the two cells stage or later. An examination of the integrated DNA in different cell types of an animal revealed that integration occurred mainly during early development. The transgene was found essentially unrearranged in the fish genome of the founders and offsprings. The transgenes were therefore stably transmitted to progeny in a Mendelian fashion. Southern blot analysis revealed the presence of possible junction fragments and also of minor bands which may result from a rearrangement of the injected DNA. In all species, the integrated DNA appeared mainly as random end-to-end concatemers. In adult trout blood cells, a small proportion of the foreign DNA was maintained in the form of non-integrated concatemers, as judged by the existence of end fragments. The transgenes were generally only poorly expressed. The majority of the injected gene constructs contained essentially mammalian or higher vertebrates sequences. The comparison of the expression efficiency of these constructs in transfected fish and mammalian cells indicates that some of the mammalian DNA sequences are most efficiently understood by the fish cell machinery. Chloramphenicol acetyl transferase gene under the control of promoters from Rous sarcoma virus, and human cytomegalovirus, was expressed in several tissues of transgenic fish. Chicken -crystallin gene was expressed in several tissues of transgenic fish. Rainbow trout growth hormone cDNA driven by the Rous sarcoma virus promoter was expressed in transgenic carps leading to a faster growth of these animals. The antifreeze protein gene from flounder was expressed in transgenic salmon. These data indicate that transgenesis in fish is relatively easy but that fish gene sequences must be preferably used to obtain a good expression of the transgenes. Fish is a good biological model, specially for developmental studies and it is an increasing part of human food. For these reasons, transgenesis in fish is most likely to be more and more practised in the coming years.     

Temperature dependence of neurotransmitter release in the antarctic fish Pagothenia borchgrevinki

The quantal contents of endplate potentials from extraocular muscles of an antarctic fish Pagothenia borchgrevinki were measured over a range of temperatures. Quantal release was maximal at about 5 degrees C but showed little dependence on temperature between -2 degrees C and 10 degrees C. Above 10 degrees C quantal content declined until release ceased about 18 degrees C. In view of the fact that the ambient temperature at which these fish live is constant at -1.9 degrees C, the results suggest that Pagothenia borchgrevinki is only partially adapted to its environment despite 25 million years acclimatization.     

Modification of the skin feeding site by tick saliva mediates virus transmission

A tick vector of Thogoto (THO) virus was shown to secrete a factor in saliva which potentiates the transmission of THO virus to uninfected ticks feeding on an apparently non-viraemic host. The effect of the saliva activated transmission (SAT) factor on the virus occurred at the site of inoculation in the skin and was apparent even when the virus was introduced 3 days after the SAT factor. The results suggest that tick saliva can play an important role in disease transmission by virtue of host modification at the site of feeding.     

Modification of the skin feeding site by tick saliva mediates virus transmission.

A tick vector of Thogoto (THO) virus was shown to secrete a factor in saliva which potentiates the transmission of THO virus to uninfected ticks feeding on an apparently non-viraemic host. The effect of the saliva activated transmission (SAT) factor on the virus occurred at the site of inoculation in the skin and was apparent even when the virus was introduced 3 days after the SAT factor. The results suggest that tick saliva can play an important role in disease transmission by virtue of host modification at the site of feeding.     

A method for chromosome preparations from large fish specimens using in vitro short-term treatment with colchicine

This paper describes a new technique for preparing mitotic fish chromosomes using short-term in vitro treatment with colchicine. The results show that a large number of good quality metaphases (many suitable for chromosome banding) can be obtained by this technique, which requires an average of 1 h and 30 min for all steps. The procedure considerably reduces the time normally required for chromosome preparations in fish.This work was supported by grants FUNCUNESP, FAPESP and CNPq.The authors are grateful to Mr Renato Devidé for technical assistance.     

The role of motile aeromonads in the fish disease, ulcerative disease syndrome (UDS)

Ulcerative Disease Syndrome (UDS) is an epizootic fish disease characterized by the presence of severe, open dermal ulcers on the head, midbody, and dorsal regions of the fish. Aeromonas hydrophila and A. sobria were recovered more often from UDS fish than other bacteria from the genera Vibrio, Alteromonas and Plesiomonas. Representative isolates of A. hydrophila, A. sobria, V. anguillarum, V. vulnificus, Alteromonas putrefaciens, and P. shigelloides taken from UDS and healthy fish were assayed for virulence-associated factors. The aeromonads produced a wide variety of hydrolytic enzymes and expressed cell surface characteristics linked to virulence whereas the other bacterial species rarely produced the same enzymes or cell surface characteristics. The role of aeromonads in UDS is believed to be opportunistic or secondary and these bacteria are thought to play an important role in this degenerative disease.     

The performance of the octopus circulatory system: A triumph of engineering over design

Summary Despite the very considerable difficulties presented by the basic molluscan anatomy and the possession of a blood pigment with an oxygen carrying capacity that never exceeds 4.5 vols%, the cephalopod circulatory system contrives to deliver oxygen at a rate fully comparable with that of an active fish. This is achieved by adding accessory pumps to push blood through the gills, by a multiplicity of pulsatile veins and by raising the systemic blood pressure considerably above the levels found in other molluscs. Detailed control of blood distribution is a necessity in a system where the peripheral resistences may be expected to change dramatically when the animal starts to move and large parts of the central nervous system are apparently dedicated to this task. In this account we have reviewed blood pressure and flow at rest and in exercise. We have further examined the evidence which indicates how the animals modulate the cardiac output, drawing attention to the very different response found in cephalopods and the higher vertebrates.     

Registration of feeding behaviour in rats by recording food approach behaviour.

A method is described in which food approach behaviour of rats is recorded to study feeding behaviour. Between rats, differences in food approach behaviour were observed. For each rat, food approach behaviour was constant over a long period of time. This allows conversion of approach behaviour data into quantified feeding behaviour. Examples of long-term feeding behaviour and of reproducibility of food intake are given.     

The relationship of phosphodiesterase and cyclic AMP to the process of fluid secretion in the salivary glands of the ixodid tickAmblyomma americanum

Summary Phosphodiesterase (PDE) activity in the salivary glands of the female.Amblyomma americanum decreased as the tick progressed from a slow to a rapid phase of feeding, while the rate of fluid secretion increased, when glands were stimulated with cyclic AMP and theophylline Dopamine stimulated PDE activity and an inhibitory factor was found in glands obtained from rapidly engorging ticks which decreased PDE activity. These findings are discussed as they relate to the process of fluid secretion by salivary glands of feeding ixodid ticks.Journal article No. 3360 of Agricultural Experiment Station, Oklahoma State University, Stillwater, Oklahoma. This research was supported in part of NSF grant PCM-24140A02 from the National Science Foundation.     

Registration of feeding behaviour in rats by recording food approach behaviour

Summary A method is described in which food approach behaviour of rats is recorded to study feeding behaviour. Between rats, differences in food approach behaviour were observed. For each rat, food approach behaviour was constant over a long period of time. This allows conversion of approach behaviour data into quantified feeding behaviour. Examples of long-term feeding behaviour and of reproducibility of food intake are given.     

Effects of pressure on oxygen consumption in cottid fish from Lake Baikal

Summary Rates of oxygen consumption in shallow dwelling cottid fish from Lake Baikal were unaffected by a change in pressure from 11 to 51 ata. The metabolic rate of deep cottids decreased by 72% when the pressure was decreased by 50% from that corresponding to habitat depth. Recovery from decreased pressures was incomplete in deep fish, suggesting that measurements of in deep dwelling fish in the literature may underestimate actual rates.Acknowledgments. Thanks are due to the US and USSR Academies of Sciences and the crew of the Titov. Support was provided by grants from The National Geographic Society, The George Baker Trust, The Max and Victoria Dreyfus Foundation, and The Griffis Foundation, Inc.     

The growth of Atlantic salmon (Salmo salar L.) myosatellite cells in culture at two different temperatures

Temperature is known to affect fish growth, and in Atlantic salmon there is an influence on muscle cellularity. Primary muscle cell culture makes it possible to investigate direct effects of temperature on myogenic cells. Salmon myosatellite cells were cultured for the first time in this study. The cells were cultured at either 5°C or 11°C. Increased temperature led to an increase in differentiation rate and especially hypertrophic growth (Q₁₀=4.0). No nuclear proliferation was evident in the satellite cell population isolated at either temperature. This may be due to the presence of different subpopulations of myogenic cells at different developmental ages or the presence of indirect factors in vivo.