The development of schooling behaviour in Atlantic herring Clupea harengus

The timing of the development of schooling behaviour in Atlantic herring Clupea harengus and the quantitative and qualitative evolution of such behaviour in the larval and post-metamorphic stages were investigated with a simulation model and experimental observations of laboratory-reared fish. Herring larvae started to develop schooling behaviour between the lengths of 35 and 40 mm. This coincided with the beginning of metamorphosis, characterized by ontogenetic changes which require a switch to a different antipredator strategy from that employed by early larvae, while providing the sensory and anatomical mechanisms necessary for the formation of schools. Schooling behaviour was established at the end of metamorphosis (50–55 mm) and its characteristics continued to evolve throughout the early juvenile stage. A critical period in terms of vulnerability to predation is expected between the end of the larval and beginning of the juvenile stages, before schooling behaviour is fully developed. The implications of some of the results for the methodology of future studies are also discussed.     

School density affects the strength of collective avoidance responses in wild‐caught Atlantic herring Clupea harengus: a simulated predator encounter experiment

An experimental study in a semi‐controlled environment was conducted to examine whether school density in wild‐caught Atlantic herring Clupea harengus affects the strength of their collective escape behaviours. Using acoustics, the anti‐predator diving responses of C. harengus in two schools that differed in density were quantified by exposing them to a simulated threat. Due to logistical restrictions, the first fish was tested in a low‐density school condition (four trials; packing density = 1·5 fish m^?3; c. 6000 fish) followed by fish in a high‐density school condition (five trials; packing density = 16 fish m^?3; c. 60 000 fish). The C. harengus in a high‐density school exhibited stronger collective diving avoidance responses to the simulated predators than fish in the lower‐density school. The findings suggest that the density (and thus the internal organization) of a fish school affects the strength of collective anti‐predatory responses, and the extent to which information about predation risk is transferred through the C. harengus school. Therefore, the results challenge the common notion that information transfer within animal groups may not depend on group size and density.     

Estimation of digestion rates for herring Clupea harengus L. feeding on fish larvae

Two methods for estimating digestion rate were evaluated and the digestion rate to disappearance was estimated to be 0·30 h⁻¹ for herring Clupea harengus feeding on capelin Mallotus villosus larvae. Due to high individual variability in feeding rates in schooling fish species, groups should be fed in separate tanks and stomach contents collected from each group at a predetermined time.     

Inheritance of allozymes in Atlantic herring (Clupea harengus harengus)

Progeny from single pair crosses of Atlantic herring were examined to determine the heritability of genetic variation at seven polymorphic allozyme loci. Mendelian inheritance of codominant autosomal alleles was established for IDH-2, LDH-1, LDH-2, ME-2, PGM-1, and PGI-2. This demonstration of Mendelian inheritance is essential for accurate interpretation of allozymic variation among natural populations of this pelagic species.     

Laboratory experiments on the schooling and feeding behaviour of Trichogaster fasciatus (Pisces: Perciformes)

Laboratory experiments were performed on the schooling and feeding behaviour of Trichogaster fasciatus . There was a tendency on the part of individuals of similar size to school together; the instinct being stronger in younger specimens. Unavailability of similar-sized individuals led to schooling by members of different size-groups. Column feeding was exhibited by the fish. While feeding at the bottom, the fishes formed angles varying from 30°90°. Larger individuals formed a right angle more often than younger members of the species. Optimum degree of crowding seemed necessary for active feeding as confinement of single individual, or overcrowded condition, both resulted in a decline of feeding activity.     

外泌体在肿瘤免疫逃逸和耐受中的作用

肿瘤细胞能够通过多种机制抵御免疫防御或药物的抗肿瘤作用.近年研究发现,外泌体能够直接介导癌症的进展和远端转移灶的形成.更为重要的是,在肿瘤免疫微环境中,肿瘤来源外泌体不仅能够抑制树突状细胞(DC)、巨噬细胞、T细胞、NK细胞等免疫细胞功能,还能促进骨髓来源的抑制性细胞(MDSC)、调节性T细胞(Treg)等的免疫抑制功能,进而降低抗肿瘤免疫应答过程,帮助肿瘤细胞逃避机体免疫细胞识别.本文将概述肿瘤外泌体及其携带的关键介质分子在介导肿瘤免疫逃逸和耐受过程中扮演的角色,并对这一研究领域的最新进展作一综述.     

Influence of temperature on evasive responses of Atlantic herring larvae attacked by yearling herring, Clupea harengus L.

Predation encounters were staged in the laboratory between yearling herring, Clupea harengus L., 66 to 104 mm t.l. , and herring larvae, 8 to 30 mm t.l. ., at 8,11 and 14 o C. Video records were used to quantify prey behaviour. Prey responsiveness, reactive distance, response latency, and apparent looming threshold were not affected by temperature. Response speeds increased with temperature. Predator error rate and capture success showed no consistent thermal effects. Although the experiments could not fully evaluate the influence of temperature on the predators, results suggest that the predator's performance largely governs the outcome of an attack on a larva and that higher temperatures favour the predator by increasing the frequency of its encounter with prey.     

The ontogeny of schooling behaviour in the striped jack

The ontogeny of schooling behaviour was investigated in laboratory-reared striped jack Pseudocaranx dentex larvae and juveniles. Mean separation angle between nearest individuals averaged 78 and 82° in 10- and 12-mm fish, respectively, and decreased to 57° in 16-mm fish. In addition, interindividual distance decreased from three times body length in 12-mm fish to twice the body length in 16-mm individuals; this value continued to decrease gradually to 1·3 at 19 mm to 0·79 at 30 mm. Mutual attraction due to visual recognition was observed in 12-mm fish and increased with total length. The optokinetic response ( R_o , the ability of a fish to keep station with moving patterns) first appeared in 4–6-mm larvae. In spite of the traditional emphasis of the importance of R_o in schooling behaviour, the onset of R_o was insufficient to result in school formation. The emergence of mutual attraction seems essential for the ontogeny of schooling.     

Fourteen new microsatellite markers for Atlantic herring Clupea harengus

Fourteen new microsatellite loci were developed and tested on Atlantic herring Clupea harengus with 39 individuals from Iceland and 49 individuals from Norway. The microsatellites, which contain di, tri and tetranucleotide repeats, are polymorphic (7-30 alleles), with observed heterozygosity ranging between 0·69 and 1·00 and expected heterozygosity between 0·55 and 0·97.     

The effect of dietary docosahexaenoic acid on schooling behaviour and brain development in larval yellowtail

The onset of schooling behaviour and brain growth in larval yellowtail Seriola quinqueradiata larvae fed on Artemia enriched with oleic acid (OA), eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA) for 10 days was investigated. Larvae from the DHA groups schooled with parallel orientation while those of the EPA groups showed only aggregation. Larvae of the OA groups were dispersed. DHA and EPA groups showed significantly smaller nearest neighbour distance compared with OA groups, and DHA groups showed significantly smaller values of nearest neighbour angle compared with the other groups. The relative volume of the tectum opticus (TO) of the DHA group was significantly larger in two experiments and also the relative volume of the cerebellum (CE) of that group was significantly larger in one experiment. Dietary DHA is probably critically important for the development of the brain, particularly TO, during the larval stages, and that development of TO may be the key factor of the ontogeny of schooling behaviour.     

Population structure of Atlantic herring, Clupea harengus L.

During the last decade, genetic studies have been carried out on samples of Atlantic herring, CIupea harengus L., from the Baltic, North Sea, British Isles, Norwegian sea-waters and in the western part of the North Atlantic Ocean. Based on direct comparisons of samples drawn from several areas, the available information on allozyme variation was compiled into a comparable data set and analysed for population structure and genetic distance. The results are discussed in relation to the present stock model for herring.     

Differential utilization of storage lipids and storage proteins by Northwest Atlantic herring (Clupea harengus harengus)

Utilization of storage lipids and storage proteins by non-feeding north-west Atlantic herring was assessed under conditions of: (1) concurrent gonad maturation and overwintering periods with differing rates of gonad development for males and females (spring-spawncrs); (2) overwintering, reproductively dormant and spent males and females (autumn-spawners); and (3) approximately equivalent rates of gonad development during late summer for males and females (autumn-spawners). Storage lipids were depleted by all non-feeding fish but storage proteins were depleted only by herring with measurable gonad development during the observation period independently of season (female spring-spawners, maturing male and female autumn-spawners). The analyses indicate that storage lipids sustain routine and active metabolism while storage proteins are utilized to develop gonad. Therefore, the relative investment into reproduction versus routine and active metabolism can be evaluated separately for non-feeding herring using readily obtainable tissue proximate composition data.     

Purification and properties of malic enzyme from herring Clupea harengus spermatozoa

Herring spermatozoa exhibit higher activity of malic enzyme (ME) than Atlantic salmon (Salmo salar), brown trout (Salmo trutta), carp (Cyprinus carpio) and African catfish (Clarias gariepinus) spermatozoa. Two molecular forms of ME are present in herring spermatozoa: an NAD-preferring malic enzyme with very high activity and an NADP-specific malic enzyme with much lower activity (ratio about 33:1). NAD-preferring ME was purified by chromatography on DEAE-Sepharose, Red Agarose and Sephadex G-200 to a specific activity of 36 μmol/min/mg protein and NADP-specific ME on DEAE-Sepharose and 2′5′-ADP Sepharose. The molecular mass for NAD-preferring and NADP-specific ME determined by SDS-PAGE was equal to 61 and 64 kDa, respectively. High activity of ME suggests adaptation of herring spermatozoa to metabolism at high oxygen tension for herring spawn.     

The effect of progressive hypoxia on swimming activity and schooling in Atlantic herring

Schools of herring exposed to progressive hypoxia show a peak in velocity during severe hypoxia, at 15–34% oxygen saturation, followed by a decrease in swimming speed until school disruption occurred. The observed increase in swimming speed during severe hypoxia reveals a graded response, since the lower the fish's swimming speed prior to severe hypoxia ( U ₉₅₋₅₀, the speed at oxygen saturations between 95 and 50%), the greater the relative increase in swimming speed. The oxygen saturations at which both peak velocity and school disruption occurred were lower for fish with lowest U ₉₅₋₅₀, suggesting that the fish with the slowest speed U ₉₅₋₅₀ reach their critical P_O2 (at which there is respiratory distress) last, i.e. at lower oxygen saturation. At a functional level, it is suggested that herring encountering hypoxia increase their speed in order to find more favourable conditions, and the magnitude of this increase is modulated by their respiratory distress. It is also hypothesised that the observed increase in speed may be related to an increase in the rate of position shifting within the school. Since the oxygen saturation at which the response to hypoxia occurs and the magnitude of the response are related to the fish's preferred speed prior to severe hypoxia, it is suggested that such a preferred speed should be measured in experiments testing the effect of hypoxia on fish behaviour.     

Strategic Escape Direction: Orientation,Turning, and Escape Trajectories of Zebra‐Tailed Lizards (Callisaurus draconoides)

A prey's body orientation relative to a predator's approach path may affect risk of fleeing straight ahead. Consequently, prey often turn before fleeing. Relationships among orientation, turn, and escape angles and between these angles and predation risk have not been studied in terrestrial vertebrates and have rarely been studied in the field. Escape angles are expected to lead away from predators and be highly variable to avoid being predictable by predators. Using approach speed as a risk factor, we studied these issues in the zebra‐tailed lizard, Callisaurus draconoides. Lizards fled away from human simulated predators, but most did not flee straight away. Escape angles were variable, as expected under the unpredictability hypothesis, and had modes at nearly straight away (i.e., 0°) and nearly perpendicular to the predator's approach path (90°). The straight away mode suggests maximal distancing from the predator; the other mode suggests maintaining ability to monitor the predator or possibly an influence of habitat features such as obstacles and refuges that differ among directions. Turn angles were larger when orientation was more toward the predator, and escape angles were closer to straight away when turn angles were larger. Turning serves to reach a favorable fleeing direction. When orientation angle was more toward the predator, escape angle was unaffected, suggesting that turn angle compensates completely for increased risk of orientation toward the predator. When approached more rapidly, lizards fled more nearly straight away, as expected under greater predation risk. Turn angles were unrelated to approach speed.     

Host Location by Apterous Aphids After Escape Dropping from the Plant

In response to approaching enemies aphids may drop from their host plant to the ground. The risk of predation on the ground, desiccation and host loss, create the need for efficient host location by the dropping aphids. Most studies have focused on the factors that influence dropping behavior; only a few have addressed host location after dropping from the plant. We assessed post-dropping behavior in apterous Macrosiphoniella artemisiae (Boyer de Fonscolombe) (Aphididae), which feed on Artemisia arborescens L. Vibration of the apical bud induced dropping in 36% of the colony members. Dropping rates were highest in mature aphids (63%). In the experimental arena (without ground predators), nearly all mature aphids that were dropped 13 cm from the plant, found their way back in ca. 40 s. The location process may be based on visual cues, as M. artemisiae is capable of visually discriminating between host and non-host targets and apparently does not react to volatiles emitted from the plant.     

Variation in egg mass within two Atlantic herring Clupea harengus stocks

The main objective of this study was to investigate if egg size (mass) at spawning is invariant for Scotia-Fundy summer and autumn (SFSH) and Icelandic summer (ISSH) spawning herring Clupea harengus. Oocyte dry mass measurements for SFSH females collected in 2001 and ISSH females collected in 1999 and 2000 showed a large variation. Difference in egg dry mass among fish was found to vary by as much as twofold in each stock. For ISSH, variation in egg mass was also apparent from oocyte volume measurements made jointly with a histological examination of the ovaries. Approximately 20% of the variation in egg mass could be explained by maternal whole-body mass or total length, indicating that length or age composition in the stocks can potentially influence the recruitment success. This implies that fisheries management strategies should aim to maintain a broad range in age composition.     

Critical involvement of dietary docosahexaenoic acid in the ontogeny of schooling behaviour in the yellowtail

To investigate involvement of the central nervous system in the ontogeny of behaviour, diets of differing quality were used to rear yellowtail Seriola quinqueradiata larvae and juveniles. Artemia nauplii enriched with oleic acid (OA), eicosapentaenoic acid (EPA), or two different concentration levels of docosahexaenoic acid (DHA) were fed to yellowtail larvae (L^T 7 mm; 13 days old) for 12 days, and their behavioural development was analysed together with growth, survival, activity and fatty acid composition. Yellowtail fed with DHA–enriched Artemia showed mutual attraction behaviour at 11 mm L^T, while those fed with OA– or EPA–enriched Artemia did not show this behaviour at the same size. While fish in the OA group showed poor growth, survival and activity index, fish in the EPA group were similar to the two DHA groups. In addition, most fish tested, including the OA group, showed clear optokinetic responses. Fatty acid composition of the diet was reflected in that of the fish body. Therefore, dietary DHA in the larval stage is considered to be essential for the development of schooling behaviour in the yellowtail.