Broodcare helpers in the cichlid fish Lamprologus brichardi: Their costs and benefits

‘Helping’ in birds and mammals involves seemingly altruistic behaviour. In the cichlid fish Lamprologus birchardi helpers are usually young of former broods staying in their parents' territories and participating in all kinds of parental duties (Broodcare, territory maintenance and defence). The discovery of helpers in fish offered the chance of attempting an extensive analysis of potential costs and benefits influencing the evolution of helpers in a vertebrate. Three factors proved to be of major importance in the cost-benefit analysis of helping as opposed to leaving for family-independent nonreproductive aggregations. Due to investment and to their rank within a family's hierarchy, helpers grow at a slower rate than non-helpers. This cost is compensated for by (i) a lower mortality risk to helpers caused by their access to a defended shelter and by protection afforded by bigger family members, and (ii) a positive contribution by helpers to the future reproductive success of their parents: females with helpers produce bigger clutches and consequently more free-swimming fry (=siblings). Other variables, such as the helpers' influence on the relative breeding success of their parents, broodcare experience through helping, the chances of territory take-over, parasitism of parents' reproduction and cannibalism are of minor importance. Similar social organizations in other fish are discussed with respect to their ecology and are compared with cooperatively breeding birds and mammals.     

Optimal foraging in an amphibious mammal. II. A study using principal component analysis

The organization of underwater foraging behaviour by mink (Mustela vison) was examined using multivariate analyses, thus enabling the role of fish density and the effect of cover in shaping the mink's hunting effort to be clarified. The effect of the mink's oxygen limitation was more strongly linked to the availability of cover for the prey than to the density of fish provided. Foraging economics accounted for approximately 51% of the variance in behaviour pattern whilst oxygen constraints took out a further 23%. Open waters are deemed unsuitable hunting grounds for this predator because mink lack the underwater endurance necessary for effective pursuit of detected prey.     

Prostaglandin and the osmoregulatory role of prolactin in a teleost

Prolactin stimulates elevation of plasma chloride concentrations in $\text{Fundulus grandis}$. Treatment of fish with inhibitors of prostaglandin synthesis (indomethacin or aspirin) prevents elevation of plasma chloride following prolactin injection. Prostaglandin E₁ stimulates increased plasma chloride concentrations in either indomethacin- or aspirin-treated fish. We theorize from these results that at least some of prolactin's actions with regard to teleostean osmoregulation are mediated by stimulation of prostaglandin synthesis.     

Relationship of chin spot size to dominance in the black-chinned mouthbrooding cichlid fish (Sarotherodon melanotheron)

Aggressive interactions of male Sarotherodon melanotheron were studied to determine the communicative value of chin spot size in relation to dominance. In addition, the effects of residency and size on the aggressiveness of this fish were determined. Two-factor analysis of variance was used for frequencies of each modal action pattern for residency and size. Results show that residency played a major role in the outcome of an aggressive interaction, whereas size had little effect. Dominance of each experimental fish was calculated using Barlow & Ballin's (1976) dominance index. A chin spot ratio was obtained by dividing the chin spot area by the total surface area of the individual fish. Simple linear regression was conducted to determine if dominance and chin spot size were correlated and a positive linear relationship was found to exist between the two variables.     

The ontogeny of feeding behaviour in four species of centrarchid fish

Relatively little work has been done on the ontogeny of feeding behaviour in fish. One of the aims of this study was to compare the ontogeny of feeding behaviour in four species of centrarchid fish of diverse feeding guilds. A second aim was to test Mayr's hypothesis that the locomotory acts involved in the ontogeny of feeding behaviour would be stereotyped. All four species initially displayed five feeding acts, with three of the acts disappearing from the repertoire at various intervals. The disappearance of the acts appeared to be related to the size and not to the age of the fry. The acts decreased in frequency as the fry aged and differences among the species in frequencies were minimal. The data supported Mayr's hypothesis but a modifying corollary was added to account for changes due to maturation.     

Mechanisms of prey choice by planktivorous fish: perceptual constraints and rules of thumb

Visually foraging planktivorous fish feed preferentially on larger, energetically more valuable zooplankton. Laboratory studies of bluegill sunfish, Lepomis macrochirus, feeding on different size classes of Daphnia indicate that, at low prey densities, these fish generally select among prey encountered simultaneously by pursuing whichever one appears largest, i.e. projects the largest retinal image. At high prey densities, however, bluegills take fewer small Daphnia than predicted for fish foraging by this apparent size rule. The pattern of prey selection observed suggests that bluegills employ the apparent size rule, not as the sole determinant of prey choice, but only to direct their attention to an individual prey item. In this way, fish may consider prey encountered simultaneously in a sequential manner. The fish can then evaluate the actual size of the apparently largest prey item, and ignore it if it is below a minimum threshold actual size. The less-preferred small prey, however, are never completely excluded from the diets of the fish. This partial preference may be the result of perceptual constraints; fish may be able to evaluate the actual size of zooplankton prey only when they occur within the fish's binocular visual field.     

An enzootic nuclear polyhedrosis virus of pink shrimp: Ultrastructure,prevalence, and enhancement

A nuclear polyhedrosis virus exists in pink shrimp, Penaeus duorarum, from waters of the northern Gulf of Mexico. This virus is rod-shaped, 269 nm long, and possesses an outer envelope surrounding its nucleocapsid. The nucleocapsid is 50 nm in diameter. The virus occurs in nuclei of host hepatopancreatic and midgut cells, and is both free in the nucleus and occluded within pyramidal-shaped polyhedral inclusion bodies (PIB's). Histochemically and ultrastructurally, the shrimp PIB's appear to be ribonucleoprotein and in fine structure bear close resemblance to polyhedral inclusion bodies of Baculovirus species from insects. However, the lattice line-to-line spacing is greater than that usually reported for insect PIB's. Crowding and chemical stress of shrimp in aquaria may enhance and increase the virus infection and prevalence. In limited experiments, shrimp fed heavily infected hepatopancreatic tissues had much higher mortality than controls fed only fish. The virus appears to be enzootic in pink shrimp in nature. Cytopathological changes in infected cells of shrimp appear similar to those in insects infected with certain species of Baculovirus. The name Baculovirus penaei n.sp. is proposed for the shrimp virus.     

Mechanisms and development of parent-young vocal recognition in the piñon jay (Gymnorhinus cyanocephalus)

Mutual, vocal parent-young recognition is achieved by piñon jays (Gynnorhinus cyanocephalus) by the time the young leave the nest at 21 days to form stable crèches of dependent young. Both parents and young beging producing individualistic calls, upon which recognition is based, when the young are 14 days old. Playbacks of nestlings' begging calls to adults and parents' approach calls to nestlings showed that mutaul recognition of each other's calls is learned between nestling age of 14 and 20 days. Sonographic and statistical analyses of the begging calls of nestling and fledgling jays showed the calls to be highly individualistic. Both univariate and multivariate (PCA) statistical methods were used to determined amounts of significant variation within and among the calls of different individuals and to isolate parameters which might be used by parents in offspring recognition. The analyses support two major conclusions. First, 20.4% of all variance measured in the calls is due to variation among individuals' calls. The data imply that adults may recognize their offspring's calls based on gestalt perception of simultaneous variation in a number of parameters. Second, each young bird's calls vary gradually with time, requiring parents to ‘track’ the calls of their offspring over time. These conclusions are only tentative until a correlation between statistically significant variation and biologically significant variation is demonstrated.     

The effect of school size on the structure and dynamics of minnow schools

Varying the number of fish in schools of minnows (Phoxinus phoxinus) affects their three-dimensional structure and internal dynamics. Previous authors have suggested that single pairs of fish can be considered a school, but internal organization and structure of two-fish schools are quantitatively different from those for larger schools. Time series analyses show that correlations between fishes' instantaneous velocities increase with school size and as interfish distances decrease. Average cross-correlations of fishes' velocities indicate that leader/follower relationships are common in two-fish schools, but they are not seen for schools with more fish in them. Pairs of fish tend to swim one behind another and on the same level, but larger schools take on a more three-dimensional appearance.     

Effects of a protein-free diet on the DNA-synthesizing and dividing cells in the lymphoid organs of rats. Changes induced by phytohemagglutinin and cortisone invivo

Levels of ³H-thymidine-labeled lymphocytes on autoradiographs of cell smears and mitotic indices (M.I.) were determined in the popliteal lymph nodes (PLN), spleen and thymus of rats fed with a balanced or a protein deprived (PD) diet for 7 weeks. The latter diet reduced the number of labeled cells per 10³ in the spleen but not in the PLN's and the thymus. The M.I.'s were reduced 50% in the spleen and dropped drastically in the thymus. Subplantar injection of phytohemagglutinin (PHA) provoked a sharp increase in the M.I.'s of the PLN's and the spleen, and also moderately increased the labeling index in the PLN's in normal rats. In PD rats PHA no longer influenced the mitoses in the PLN's and the spleen while it considerably increased the proportion of labeled cells in the latter. These discrepancies between DNA-synthesis and mitoses in the thymus and the spleen suggest a premitotic block of the cell cycle after protein deprivation. The effects of a 5 day-cortisone treatment resembled in a large measure the changes induced by a protein-free diet including the arrest of the cell cycle. The thymic lymphocytes were more sensitive to the hormone in PD than in normal rats. On the contrary, in the PLN's and the spleen mainly cortisone-resistant cells remained alive among the DNA-synthesizing lymphocytes after protein deprivation. All these data agree with the hypothesis of an intervention of endogenous glucocorticoids in the protein deficiency-induced lymphoid involution.     

Comparison of the in vivo clearance of des-AA and des-AABB rat fibrin monomers prepared by different methods

Solubilization of fibrin monomers (Fm's) is usually performed with dilute acetic acid, urea or sodium bromide. These solvents can affect the biological properties of Fm's. Therefore we describe a new method to keep Fm's in solution, under milder conditions i.e. by generating them in Dcate solutions and avoiding non-physiological conditions. The in vivo behaviour of iodinated rat Fm's injected in rats and prepared by this new method was compared with that of Fm's dissolved in acetic acid, urea or sodium bromide.Fm's prepared in Dcate solutions accumulate rapidly, within 10 minutes after injection, in all organs tested, predominantly in kidney, liver and lung, probably by interaction with endothelial cells. The blood radioactivity remains nearly constant during the first 90 minutes and decreases thereafter exponentially. Fm's dissolved in sodium bromide behave similarly. However, Fm's dissolved in acetic acid or urea behave differently and do not accumulate in organs. This suggests that Fm's loose their capability to accumulate in organs and probably to interact with endothelial cells when they have been dissolved in acetic acid or urea.The slow exponential clearance phase does not differ significantly between the various Fm's and their $\text{T}\text{1}\text{2'S}$ are estimated to lie between 5 and 7 hours.     

Alzheimer's disease and Down's syndrome: Sharing of a unique cerebrovascular amyloid fibril protein

The cerebrovascular amyloid protein from a case of adult Down's syndrome was isolated and purified. Amino acid sequence analysis showed it to be homologous to that of the β protein of Alzheimer's disease. This is the first chemical evidence of a relationship between Down's syndrome and Alzheimer's disease. It suggests that Down's syndrome may be a predictable model for Alzheimer's disease. Assuming the β protein is a human gene product, it also suggests that the genetic defect in Alzheimer's disease is localized on chromosome 21.     

Effects of the eyefluke, Diplostomum spathaceum, on the behaviour of dace (Leuciscus leuciscus)

The behaviour of dace infected with Diplostomum spathaceum was investigated in the laboratory. As the number of parasites present in the eye increased, the efficiency with which the fish fed on Gammarus pulex declined. The loss of efficiency was compensated for by an increase in the time devoted to feeding. Heavily infected fish spent more time in the surface layers of the water. This may increase the likelihood that a gull might eat the fish and thereby continue the life-cycle of the parasite. The parasite modifies the behaviour of its host in a way that increases the parasite's chances of survival at the expense of the host.     

ATP and ADP hydrolysis in fish, chicken and rat synaptosomes

Ecto-enzymes capable of hydrolyzing ATP and ADP (NTPDase) are present in the central nervous system of various species. In the present investigation we studied the synaptosomal NTPDase (ATP diphosphohydrolase, apyrase, E.C. 3.6.1.5) from fish, chicken and rats under different conditions and in the presence of several classical inhibitors. The cation concentration required for maximal activity was 0.5 mM for fish, 1.0 mM for chickens and 1.5 mM for rats with both substrates. The results showed that the pH optimum for all animal preparations was close to 8.0. The temperature used was 25–27°C for fish and 35–37°C for chicken and rat preparations. The inhibitors azide and fluoride only inhibited the preparation at high concentrations (10 mM). Lanthanum (0.1–0.4 mM), N-ethylmaleimide (0.4–3.0 mM) and ouabain (0.5–3.0 mM) had no effect on NTPDase activity from fish, chickens or rats. Orthovanadate (0.1–0.3 mM) only inhibited fish synaptosomal NTPDase. Trifluoperazine (0.05–0.2 mM) and suramin (0.03–0.3 mM) inhibited NTPDase at all concentrations tested. Suramin was the most potent compound in causing inhibition, presenting inhibition at 30 μM. Our results demonstrate that the synaptosomal NTPDase response to several factors is similar in fish, chickens and rats, and that the enzyme presents functional homology.     

Integrated aquaculture in Chinese lakes and paddy fields

While pond culturing is still the staple of Chinese freshwater fisheries, its extensive development is handicapped by the increasing shortage of land resource for cereal production in face of China’s population growth. Accordingly, people have looked towards the development of aquaculture in lakes (and reservoirs) in the 1970s. This paper reviews the successful integrated measures taken in an experiment for raising fish in Donghu lake (East lake) of Wuhan. By way of (1) stocking the right kinds of fish; (2) producing a large number of sizeable fingerlings; (3) improving fish screens; (4) controlling predatory fish; and (5) applying the ‘driving and concentrating’ bulk harvesting fishing method, fish production of the lake has increased steadily from 180 t in 1971 to 800 t in 1978, and then to 1840 t in 1995, all in an area of 1500 ha, and all without any supplementary feeding. Integrated aquaculture in paddy fields, known to be beneficial to both rice and fish production, has been regaining momentum in recent years. The paper summarizes its underlying principle, its benefits—economical, social and ecological—and the prospect of its development in China.     

Long-Term GPS Tracking of Ocean Sunfish Mola mola Offers a New Direction in Fish Monitoring

Satellite tracking of large pelagic fish provides insights on free-ranging behaviour, distributions and population structuring. Up to now, such fish have been tracked remotely using two principal methods: direct positioning of transmitters by Argos polar-orbiting satellites, and satellite relay of tag-derived light-level data for post hoc track reconstruction. Error fields associated with positions determined by these methods range from hundreds of metres to hundreds of kilometres. However, low spatial accuracy of tracks masks important details, such as foraging patterns. Here we use a fast-acquisition global positioning system (Fastloc GPS) tag with remote data retrieval to track long-term movements, in near real time and position accuracy of <70 m, of the world''s largest bony fish, the ocean sunfish Mola mola. Search-like movements occurred over at least three distinct spatial scales. At fine scales, sunfish spent longer in highly localised areas with faster, straighter excursions between them. These ‘stopovers’ during long-distance movement appear consistent with finding and exploiting food patches. This demonstrates the feasibility of GPS tagging to provide tracks of unparalleled accuracy for monitoring movements of large pelagic fish, and with nearly four times as many locations obtained by the GPS tag than by a conventional Argos transmitter. The results signal the potential of GPS-tagged pelagic fish that surface regularly to be detectors of resource ‘hotspots’ in the blue ocean and provides a new capability for understanding large pelagic fish behaviour and habitat use that is relevant to ocean management and species conservation.     

High frequency of-β-hexosaminidase deficiency in lymphoblastoid cell lines

The activity of seven lysosomal enzymes was determined in 25 lymphoblastoid cell lines. These lines included normal controls transformed with Epstein-Barr virus, Burkitt's lymphomas and other lymphomas with or without EBV genome.Four lines were deficient in total β-hexosaminidase activity. The deficiency was as severe as that of the variant O (Sandhoff's disease) of clinical β-hexosaminidase deficiency. The electrophoretic pattern was also similar to that observed in Sandhoff's disease.The possible mechanisms explaining the high frequency of β-hexosaminidase deficiency in lymphoblastoid cell lines are discussed.     

Simplifying principles for chemical and enzyme reaction kinetics

Tihonov's Theorems for systems of first-order ordinary differential equations containing small parameters in the derivatives, which form the mathematical foundation of the steady-state approximation, are restated. A general procedure for simplifying chemical and enzyme reaction kinetics, based on the difference of characteristic time scales, is presented. Korzuhin's Theorem. which makes it possible to approximate any kinetic system by a closed chemical system, is also reported. The notions and theorems are illustrated with examples of Michaelis-Menten enzyme kinetics and of a simple autocatalytic system. Another example illustrates how the differences in the rate constants of different elementary reactions may be exploited to simplify reaction kinetics by using Tihonov's Theorem. All necessary mathematical notions are explained in the appendices. The most simple formulation of Tihonov's 1st Theorem ‘for beginners’ is also given.     

Migratory Patterns of Wild Chinook Salmon Oncorhynchus tshawytscha Returning to a Large,Free-Flowing River Basin

Upriver movements were determined for Chinook salmon Oncorhynchus tshawytscha returning to the Yukon River, a large, virtually pristine river basin. These returns have declined dramatically since the late 1990s, and information is needed to better manage the run and facilitate conservation efforts. A total of 2,860 fish were radio tagged during 2002–2004. Most (97.5%) of the fish tracked upriver to spawning areas displayed continual upriver movements and strong fidelity to the terminal tributaries entered. Movement rates were substantially slower for fish spawning in lower river tributaries (28–40 km d^-1) compared to upper basin stocks (52–62 km d^-1). Three distinct migratory patterns were observed, including a gradual decline, pronounced decline, and substantial increase in movement rate as the fish moved upriver. Stocks destined for the same region exhibited similar migratory patterns. Individual fish within a stock showed substantial variation, but tended to reflect the regional pattern. Differences between consistently faster and slower fish explained 74% of the within-stock variation, whereas relative shifts in sequential movement rates between “hares” (faster fish becoming slower) and “tortoises” (slow but steady fish) explained 22% of the variation. Pulses of fish moving upriver were not cohesive. Fish tagged over a 4-day period took 16 days to pass a site 872 km upriver. Movement rates were substantially faster and the percentage of atypical movements considerably less than reported in more southerly drainages, but may reflect the pristine conditions within the Yukon River, wild origins of the fish, and discrete run timing of the returns. Movement data can provide numerous insights into the status and management of salmon returns, particularly in large river drainages with widely scattered fisheries where management actions in the lower river potentially impact harvests and escapement farther upstream. However, the substantial variation exhibited among individual fish within a stock can complicate these efforts.