Characterization of vibrational and visual signals which elicit spawning behavior in the male himé salmon (landlocked red salmon,Oncorhynchus nerka)

Himé salmon (landlocked red salmon, Oncorhynchus nerka) have an elaborate communication system, which ensures synchronous spawning by both sexes and successful fertilization. Both the vibrational and visual signals have been suggested to be involved in this communication system. To characterize these signals, vibrating or stationary three-dimensional models of various types were presented to the male, and male behavior elicited was examined. The results showed that the vibrating model mimicking certain aspects of the female behavior (prespawning act) elicits the spawning in the male (Figs. 2, 3, 5). Furthermore, it was found that (1) the presence of both the vibrational and visual cues (Figs. 6, 7), and (2) spatial coincidence of these two cues (Fig. 8) are necessary for eliciting this behavior. Based on these results it was supposed that the vibrational and visual informations converge at the central nervous system where they are integrated to elicit the spawning.     

Non-indigenous brook trout and the demise of Pacific salmon: a forgotten threat?

Non-indigenous species may be the most severe environmental threat the world now faces. Fishes, in particular, have been intentionally introduced worldwide and have commonly caused the local extinction of native fish. Despite their importance, the impact of introduced fishes on threatened populations of Pacific salmon has never been systemically examined. Here, we take advantage of several unique datasets from the Columbia River Basin to address the impact of non-indigenous brook trout, Salvelinus fontinalis, on threatened spring/summer-run chinook salmon, Oncorhynchus tshawytscha. More than 41 000 juvenile chinook were individually marked, and their survival in streams without brook trout was nearly double the survival in streams with brook trout. Furthermore, when brook trout were absent, habitat quality was positively associated with chinook survival, but when brook trout were present no relationship between chinook survival and habitat quality was evident. The difference in juvenile chinook survival between sites with, and without, brook trout would increase population growth rate (lambda) by ca. 2.5%. This increase in lambda would be sufficient to reverse the negative population growth observed in many chinook populations. Because many of the populations we investigated occur in wilderness areas, their habitat has been considered pristine; however, our results emphasize that non-indigenous species are present and may have a dramatic impact, even in remote regions that otherwise appear pristine.     

Stable isotopes reveal contrasting trophic dynamics between host–parasite relationships: A case study of Atlantic salmon (Salmo salar) and parasitic lice (Lepeophtheirus salmonis and Argulus foliaceus)

Across existing fish host–parasite literature, endoparasites were depleted in δ¹⁵N compared to their hosts, while ectoparasitic values demonstrated enrichment, depletion and equivalence relative to their hosts. δ¹³C enrichment varied extensively for both endo- and ectoparasites across taxa and host tissues. In our case study, sea lice (Lepeophtheirus salmonis) were enriched in δ¹⁵N relative to their farmed Atlantic salmon (Salmo salar) hosts, although the value contradicted the average that is currently assumed across the animal kingdom. Common fish lice (Argulus foliaceus) did not show a consistent trend in δ¹⁵N compared to their wild S. salar hosts. Both parasitic species had a range of δ¹³C enrichment patterns relative to their hosts. Farmed and wild S. salar had contrasting δ¹³C and δ¹⁵N, and signals varied across muscle, fin and skin within both groups. L. salmonis and A. foliaceus subsequently had unique δ¹³C and δ¹⁵N, and L. salmonis from opposite US coasts differed in δ¹⁵N. Given the range of enrichment patterns that were exhibited across the literature and in our study system, trophic dynamics from host to parasite do not conform to traditional prey to predator standards. Furthermore, there does not appear to be a universal enrichment pathway for δ¹³C nor δ¹⁵N in parasitic relationships, which emphasizes the need to investigate host–parasite linkages across species.     

The caudal spinal cord of coho salmon (Oncorhynchus kisutch): Immunocytochemical evidence of a “caudal serotoninergic system”

Summary The caudal spinal cord of the coho salmon was investigated by means of immunocytochemistry using antisera against serotonin, urotensin I, urotensin II, somatostatin and a urea-extract of bovine Reissner's fiber (AFRU). Populations of serotonin-immunoreactive (IR) neurons were found rostral and dorsal to the urophysis in close spatial association with caudal secretory neurons. Thick, smooth serotonin-IR processes extended toward the external surface of the spinal cord where they displayed conspicuous terminal dilatations. Thin, beaded serotonin-IR fibers appeared to innervate populations of caudal secretory and somatostatin-IR cerebrospinal fluid-contacting neurons. Most caudal neurosecretory cells displayed both urotensin I and urotensin II immunoreactivities; only a minority reacted exclusively with either urotensin I or urotensin II antisera. Urotensin II-IR and somatostatin-IR cerebrospinal fluid (CSF)-contacting neurons were found as an integral component of the central canal wall in the caudal spinal cord and filum terminale; their dendritic processes appeared to contact Reissner's fiber, which displayed a weak AFRU-immunoreactivity while inside the central canal, but became strongly reactive in the interior of the terminal ventricle as it formed the massa caudalis. The distribution of serotoninergic processes points to a regulatory role in the function of caudal secretory and CSF-contacting neurons and to a putative serotonin release into the subarachnoid space and/or meningeal vasculature. It is also suggested that the CSF-contacting neurons of the central canal may participate in a feedback mechanism controlling the secretory activity of the subcommissural organ.Supported by Grant A/1095-1 from the International Foundation for Science, Sweden, to C.Y.; Grant I/63-476 from Volkswagen-Stiftung to E.R.; and Grant S-85-39 from the Dirección de Investigaciones, Universidad Austral de Chile     

Differential responses of kin and nonkin salmon to patterns of water flow: does recirculation influence aggression?

Studies conducted in laboratory streams have shown that juvenile salmonid fish (parr) can differentiate between their kin and nonkin and may be less aggressive towards their kin. Chemicals produced by salmonids are also known to be used as cues to aid kin recognition. We tested the hypothesis that the ability of Atlantic salmon, Salmo salar, to recognize kin and hence modulate their level of aggression is influenced by the amount of water recirculation, which would be expected to affect the concentration of odour. Levels of aggression were similar between pairs of kin and pairs of nonkin when there was negligible recirculation of water. However, when water was recirculated, pairs of nonkin were on average 1.56 times more aggressive than pairs of kin, owing to an increase in attacks by the dominant fish. The data do not support the idea that odour concentration affects kin recognition and hence reduces aggression among siblings. Instead they indicate that recirculation of water instigates heightened aggression in dominant fish but only towards nonkin subordinates. The study suggests that the advantages for juvenile salmonids of associating with kin vary spatially, being influenced by water flow dynamics. Copyright 2000 The Association for the Study of Animal Behaviour.     

Behavioral and electrophysiological evidences that the lateral line is involved in the inter-sexual vibrational communication of the himé salmon (landlocked red salmon,Oncorhynchus nerka)

Characteristic vibrational signals are suggested to be exchanged between the sexes during the spawning behavior in the himé salmon (landlocked red salmon, Oncorhynchus nerka). To check whether the lateral line is used to detect and process these vibrational signals, we examined how Co²⁺, which is known to block the mechano-electrical transduction in the lateral line detector, affects both the spawning behavior and lateral line response of the male himé salmon. The results showed that Co²⁺ blocked both the spawning behavior towards the vibrating model (Fig. 2) and the lateral line response to the vibrational stimuli (Figs. 5, 6), if the fish were forced to swim in the water containing 1.0 mM Co²⁺ for 1 to 1.5 h or longer in the presence of 0.25 mM Ca²⁺. 0.1 mM Co²⁺ had similar but weaker effects. These results indicate that the vibrational signals from the vibrating model are detected and processed by the lateral line system to elicit the spawning behavior. These are the first experimental evidences that the lateral line sense is involved in the communicational behavior of the fish.     

Deterioration of chum salmon (Oncorhynchus keta) muscle during spawning migration—III. Changes in protein composition and protease activity of juvenile chum salmon muscle upon treatment with sex steroids

• 1.1. Changes in protein composition and protease activity of juvenile chum salmon muscle upon treatment with sex steroids were investigated.
• 2.2. A slight breeding color was observed on chum salmon following the oral administration of 17α-methyltestosterone. Sarcoplasmic protein significantly decreased, while ninhydrin-positive substances from protein-free fractions significantly increased upon treatment with 17α-methyltestosterone. Autolytic activity of the fish treated with 17α-methyltestosterone drastically increased.
• 3.3. Estradiol-17β did not significantly influence the protein composition and autolytic activity.
• 4.4. These results indicate that androgen is closely related to the deterioration of chum salmon muscle.

     

Cloning and sequence analysis of cDNAs encoding the MHC class II β chain in Atlantic salmon (Salmo salar)

Atlantic salmon (Salmo salar) cDNAs encoding the major histocompatibility complex (Mhc-Sasa) class II chain were isolated from a leucocyte library by a polymerase chain reaction (PCR) approach. Three different cDNAs (c144, c22, and c157) encoding the entire mature chain have been analyzed. Clone c144 differs from clone c157 in 12.6% of the nucleotides in the 1-encoding region. The corresponding differences between clones c144 and c22, and clones c22 and c157, are 10.3% and 5.2%, respectively. This variation is, at least in part, most likely attributable to allelism. The similarity indices between the highly conserved 2 domains from Atlantic salmon and corresponding sequences from humans (DQ), chicken (BL), carp (TLAII-1), and rainbow trout (O. M. No. 55) are 45%, 40%, 66%, and 97%, respectively. Variable residues in the 1 domains from Atlantic salmon correspond with polymorphic sites of 1 domains from higher vertebrates. The frequency of substitutions in the 1-encoding region exceeds that in the 3-untranslated (UT) region with several folds, indicating extensive 1 polymorphism in Atlantic salmon.The nucleotide sequence data reported in this paper have been submitted to the GenBank nucleotide sequence database and have been assigned the accession numbers (C 144) X 70165, (C 157) X 70166, and (C 22) X 70167.This study was supported by grants from the Norwegian Fisheries Research Council (NFFR) and the Norwegian Agricultural Research Council (NLVF).     

Atlantic salmon growth in strongly food-limited environments: Effects of egg size and paternal phenotype?

I manipulated egg size and followed individual mass trajectories from the egg stage in Atlantic salmon to test for effects of size, and for interactions between size and paternal body mass, on offspring performance in strongly food-limited environments. Egg size had a strong effect on body mass at yolk absorption, causing juveniles originating from large eggs to outgrow their siblings from small eggs. This corroborates previous findings of egg size effects under more benign environments, and demonstrates that positive effects of egg size on offspring success are manifested even under strong food-limitation. Previously reported negative effects of being large during the critical period for survival in dense populations are thus likely related to social interactions, rather than to effects of density on total food abundance in the environment. The effect of egg size on offspring performance, and hence the optimal egg size, was independent of paternal body mass.     

Structure and ultrastructure of the silk glands and spinneret of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae)

This study provides comprehensive documentation of silk production in the pest moth Helicoverpa armigera from gland secretion to extrusion of silk thread. The structure of the silk glands, accessory structures and extrusion apparatus are reported. The general schema of the paired silk glands follows that found for Lepidoptera. Morphology of the duct, silk press, muscle attachments and spigot are presented as a three-dimensional reconstruction and the cuticular crescent-shaped profile of the silk press is demonstrated in both open and closed forms with attendant muscle blocks, allowing advances in our knowledge of how the silk press functions to regulate the extrusion of silk. Growth of the spigot across instars is documented showing a distinctive developmental pattern for this extrusion device. Its shape and structure are related to use and load-bearing activity.     

Consumption of salmon by Alaskan brown bears: a trade-off between nutritional requirements and the risk of infanticide?

The risk of infanticide may alter foraging decisions made by females, which otherwise would have been based on nutritional requirements and forage quality and availability. In systems where meat resources are spatially aggregated in late summer and fall, female brown bears ( Ursus arctos) would be faced with a trade-off situation. The need of reproductive females to accumulate adequate fat stores would likely result in a decision to frequent salmon streams and consume the protein- and lipid-rich spawning salmon. In contrast, aggregations of bears along salmon streams would create conditions of high risk of infanticide. We investigated consumption of salmon by brown bears on Admiralty and Chichagof Islands in Southeast Alaska from 1982 to 2000 using stable isotope analysis and radiotelemetry. While nearly all males (22 of 23) consumed relatively large amounts of salmon (i.e., >10% relative contribution to seasonal diet), not all females ( n =56) did so. Five of 26 females for which we had reproductive data, occupied home ranges that had no access to salmon and thus did not consume salmon when they were mated or accompanied by young. Of females that had access to salmon streams ( n =21), all mated individuals ( n =16) had ¹⁵N values indicative of salmon consumption. In contrast, 4 out of 16 females with cubs avoided consuming salmon altogether, and of the other 12, 3 consumed less salmon than they did when they were mated. For 11 of 21 females with access to salmon streams we had data encompassing both reproductive states. Five of those altered foraging strategies and exhibited significantly lower values of ¹⁵N when accompanied by young than when mated, while 6 did not. Radiotelemetry data indicated that females with spring cubs were found, on average, further away from streams during the spawning season compared with females with no young, but both did not differ from males and females with yearlings and 2-year-olds. Females with young that avoided salmon streams were significantly lighter indicating that female choice to avoid consumption of salmon carries a cost that may translate to lower female or cub survivorship. The role of the social hierarchy of males and females, mating history, and paternity in affecting the risk of infanticide and foraging decisions of female brown bears merit further investigation.     

Rhythmic electromyographic activities of trunk muscles characterize the sexual behavior in the Himé salmon (landlocked sockeye salmon,Oncorhynchus nerka)

Summary In order to describe precisely the fixed action patterns of salmon sexual behavior, we recorded the electromyographic (EMG) activities of trunk and jaw muscles from freely behaving male and female Himé salmon (landlocked sockeye salmon,Oncorhynchus nerka). A series of action patterns (quivering and spawning act in males, digging, covering, prespawning act and spawning act in females, and the swimming and turning movements in both sexes) were characterized by rhythmic activities of the trunk muscles. Each of these activity patterns is quantitatively distinct from the others in such parameters as frequency, bout duration, duty value, intersegmental phase delay, and spatial distribution of rhythmic activities. However, all of these rhythms share a qualitatively homologous pattern with the forward swimming movement: rhythmic activities alternate on both sides of the body (bilateral coupling) and are posteriorly propagated (intersegmental coupling). In addition, a 31 intersegmental phase coupling occurs in the most anterior trunk muscles during the spawning act in some males. Based on these observations, we discussed the biomechanics for these motor patterns (oviposition, ejaculation, body vibration, and mouth opening), and the neural mechanisms for the pattern generation. A possibility was pointed out that the locomotor pattern generator in the spinal cord may be modulated by descending supraspinal signals and recruited to generate such diverse forms of action patterns in sexual behavior.Abbreviations CPG central pattern generator - EMG electromyography - AC adductor mandibulae (cephalic portion) - AM adductor mandibulae (mandibular portion) - DO dilator operculi - GH geniohyoideus - LAP levator arcus palatitni - LPe musculus lateralis profundus (epaxial portion) - LPh musculus lateralis profundus (hypaxial portion) - LS musculus lateralis superficialis - PD protractor dorsalis - PI protractor ischii - RD retractor dorsalis - RI retractor ischii     

Sequence analysis of MHC class I α2 from sockeye salmon (Oncorhynchus nerka)

Most studies assessing adaptive MHC diversity in salmon populations have focused on the classical class II DAB or DAA loci, as these have been most amenable to single PCR amplifications due to their relatively low level of sequence divergence. Herein, we report the characterization of the classical class I UBA α2 locus based on collections taken throughout the species range of sockeye salmon (Oncorhynchus nerka). Through use of multiple lineage-specific primer sets, denaturing gradient gel electrophoresis and sequencing, we identified thirty-four alleles from three highly divergent lineages. Sequence identity between lineages ranged from 30.0% to 56.8% but was relatively high within lineages. Allelic identity within the antigen recognition site (ARS) was greater than for the longer sequence. Global positive selection on UBA was seen at the sequence level (dN:dS = 1.012) with four codons under positive selection and 12 codons under negative selection.     

Comparative studies of α-lactalbumin and lysozyme: The proteins of kangaroo (Megaleia rufa and Macropus giganteus) and horse (Equus caballus)

Summary As part of a study of the whey proteins of various mammals, a comparison is made of the -lactalbumins and lysozymes of the kangaroo and horse. In the milk of the red kangaroo (Megaleia rufa) there is only one -lactalbumin and it occurs throughout lactation, but no lysozyme has been detected. There are two -lactalbumins in the milk of the grey kangaroo (Macropus giganteus), one, designated -lactalbumin Zone B, is present throughout lactation; the second, designated -lactalbumin Zone A, is present only in late lactation. One lysozyme is also present. The milk of the horse (Equus caballus) contains one -lactalbumin and at least one lysozyme. Partial amino acid sequences are proposed from sequence determination and from analyses of tryptic peptides compared with the known sequences of other -lactalbumins and lysozymes.     

Responses of Adult Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae) to Light and Combinations of Attractants and Light

Responses of adult Indianmeal moth, Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae) to light alone and to a combination of attractant(s) and green/UV lights were studied. When P. interpunctella adults were given a choice between dark areas and areas illuminated with UV, green, or white light, they rested preferentially on surfaces in the illuminated areas. UV light elicited the strongest of the positive phototactic responses. Light traps were not as effective as traps baited with pheromones or food lures in capturing adult moths, and combining green or UV light with these attractants did not significantly increase the trap catches. Gravid females required a period of darkness to realize maximum oviposition, and illumination above 8 lx during the scotophase of a 24-hr light–dark cycle inhibited oviposition.     

Does CO2 enhance short-term storage success of Chinook salmon (Oncorhynchus tshawytscha) milt?

Successful short-term storage of salmonid milt depends on numerous factors, including temperature, fluid volume, and gaseous environment, with storage at low temperatures under an atmosphere of 100% O2 being the most common method. Salmonid sperm maintained in a storage environment with elevated carbon dioxide (CO2) levels, such as the approximately 4% CO2 in exhaled air, are not motile when activated. While these modest levels of CO2 inhibit sperm motility, the effect is reversible within hours after exposure to a CO2-free oxygenated environment. Therefore, the effect of CO2 (as a component gas in the storage environment) on chinook salmon (Oncorhynchus tshawytscha) sperm motility and viability was examined. The hypothesis of the current investigation was that CO2-exposure with subsequent CO2 removal would be beneficial during short-term chinook salmon milt storage. Milt samples were collected from mature (adult) and precocious (jack) male chinook salmon and stored under various CO2 and O2 levels at 3 to 4 degrees C for up to 14 days. Milt samples were then removed from the incubation environments and maintained under CO2-free humidified air with continuous mixing for 4 h at 10 degrees C before analysis of motility. The resultant motility of samples incubated under 3.5% or less CO2 was not different than controls during the 14 d incubation period; motility of samples stored under higher CO2 tensions were significantly lower. The motility of samples incubated under 3.5% CO2 reached the maximum recovered motility after 2 h exposure to CO2-free humidified air, while the motility of sperm incubated under 13.4% CO2 levels recovered no motility even after 6 h exposure to CO2-free humidified air. The motility of samples incubated under normoxia was significantly greater than that of samples incubated under hyperoxia (approximately 90% O2) at both 7 and 14 d, regardless of the CO2 level. Sperm viability was relatively unaltered by any of the incubation conditions examined. The results of this investigation suggest that there is no apparent advantage to storage of chinook salmon sperm in the presence of CO2 and that storage under hyperoxia negatively affects sperm function compared to storage under normoxia.