Heterozygosity and phylogenetic relationship of Japanese threespine stickleback (<Emphasis Type="Italic">Gasterosteus aculeatus</Emphasis>) populations revealed by microsatellite analysis

Heterozygosity and phylogenetic relationships were analyzed using eight microsatellite loci for nine freshwater and one anadromous populations of threespine stickleback Gasterosteus aculeatus from northern Japan. Fis values and Hardy–Weinberg tests indicated that nine of the populations were in heterozygote deficit. Furthermore, on-going isolation of most of the populations by artificial destruction of population connection and habitat deterioration suggested that nearly all of the populations are likely to be in a threatened condition. Phylogenetic analysis revealed that there were two distinctive phylogenetic groups, each of which was composed of two and three freshwater populations. These populations included in the groups except ones recently established were located in inland waters and isolated from anadromous populations, so that they may have been able to keep unique genetic features. Therefore, it is necessary to protect as many populations as possible within the local population network including these inland populations. On the other hand, for freshwater populations located near the river mouth but recently isolated from anadromous populations by weir construction, it is important to remove or ameliorate the barrier and recover the gene flow. Microsatellite markers are important tools to monitor the population network and gene flow.     

Costly plastic morphological responses to predator specific odour cues in three-spined sticklebacks (<Emphasis Type="Italic">Gasterosteus aculeatus</Emphasis>)

Predation risk is one of the major forces affecting phenotypic variation among and within animal populations. While fixed anti-predator morphologies are favoured when predation level is consistently high, plastic morphological responses are advantageous when predation risk is changing temporarily, spatially, or qualitatively. Three-spined sticklebacks (Gasterosteus aculeatus) are well known for their substantial variability in morphology, including defensive traits. Part of this variation might be due to phenotypic plasticity. However, little is known about sticklebacks’ plastic ability to react morphologically to changing risks of predation and about the proximate cues involved. Using a split-clutch design we show that odour of a predatory fish induces morphological changes in sticklebacks. Under predation risk, i.e., when exposed to odour of a predator, fish grew faster and developed a different morphology, compared to fish reared under low predation risk, i.e., exposed to odour of a non-predatory fish, or in a fish-free environment. However, fast growing comes at cost of increased body asymmetries suggesting developmental constraints. The results indicate that sticklebacks are able to distinguish between predatory and non-predatory fishes by olfactory cues alone. As fishes were fed on invertebrates, this reaction was not induced by chemical cues of digested conspecifics, but rather by predator cues themselves. Further, the results show that variation in body morphology in sticklebacks has not only a strong genetical component, but is also based on plastic responses to different environments, in our case different predation pressures, thus opening new questions for this model species in ecology and evolution.     

Taste preferences and feeding behavior in threespine stickleback <Emphasis Type="Italic">Gasterosteus aculeatus</Emphasis> in marine and fresh waters

Taste preferences of four classic taste substances (NaCl, CaCl₂, and sucrose, all—10%; and citric acid—5%), and 21 free amino acids (L-isomers, 0.1–0.001 M) for adult threespine stickebacks Gasterosteus aculeatus is determined in marine and fresh waters. Gustatory responses were compared in the fish caught in marine and placed in marine water or in freshwater and in the fish caught in a stream mouth during spawning migration and in a closed freshwater water body. Taste preferences of threespine sticklebacks depend little on water salinity. Of amino acids, cysteine, glutamic acid, and aspartic acid are attractive, as well as glutamine for the fish living permanently in fresh water. Differences in the reaction of fish to agar-agar pellets with NaCl, CaCl₂, and sucrose are considered to be insignificant. Maximum changes occur in the attitude of threespine sticklebacks to citric acid whose taste is palatable to fish in fresh water. It is assumed that the components of marine water render a modifying action on gustatory receptors, the function of receptor cell, and influence susceptibility of fish to the taste of citric acid and, probably, of some other substances. The foraging behavior of fish in fresh water is more active, they consume more pellets, make more numerous repeated grasps, and keep pellets longer in the mouth cavity before swallowing or rejection. It is concluded that, in migratory fish, the abrupt change of external osmotic conditions is not accompanied by noticeable changes on taste preferences and the majority of substances retain their gustatory properties.     

Rapid molecular sexing of three-spined sticklebacks, <Emphasis Type="Italic">Gasterosteus aculeatus</Emphasis> L., based on large Y-chromosomal insertions

There is a need for rapid and reliable molecular sexing of three-spined sticklebacks, Gasterosteus aculeatus, the supermodel species for evolutionary biology. A DNA region at the 5′ end of the sex-linked microsatellite Gac4202 was sequenced for the X chromosome of six females and the Y chromosome of five males from three populations. The Y chromosome contained two large insertions, which did not recombine with the phenotype of sex in a cross of 322 individuals. Genetic variation (SNPs and indels) within the insertions was smaller than on flanking DNA sequences. Three molecular PCR-based sex tests were developed, in which the first, the second or both insertions were covered. In five European populations (from DE, CH, NL, GB) of three-spined sticklebacks, tests with both insertions combined showed two clearly separated bands on agarose minigels in males and one band in females. The tests with the separate insertions gave similar results. Thus, the new molecular sexing method gave rapid and reliable results for sexing three-spined sticklebacks and is an improvement and/or alternative to existing methods.     

Growth history and migration of the threespine stickleback <Emphasis Type="Italic">Gasterosteus aculeatus</Emphasis> in Otsuchi Bay,northeastern Japan

 Both growth and migratory history of the Pacific Ocean forms of the threespine stickleback Gasterosteus aculeatus collected in Otsuchi Bay, northeastern Japan, were examined using otolith microstructure and analysis of strontium (Sr) and calcium (Ca) concentrations with wavelength dispersive X-ray spectrometry by an electron microprobe. Age of the juveniles (21.6–25.9 mm in total length) examined ranged from 101 to 128 days (115 ± 8.5 days; mean ± SD), hatching being estimated as having occurred between March and April 2001. The Sr : Ca ratios in the otoliths changed with both ontogenic development and salinity of the habitat. The otolith Sr : Ca ratios increased gradually from 4.1 × 10⁻³ around the core to 7.5 × 10⁻³ around the edge of the otolith. The fluctuation pattern of otolith Sr : Ca ratios was different from those observed in both freshwater resident and anadromous forms in previous studies. These results suggested that the fish sampled spend their lives in the estuarine and sea environment without freshwater life after hatching. Received: June 5, 2002 / Revised: September 11, 2002 / Accepted: September 24, 2002 Acknowledgments We thank Mr. K. Morita and crews of the Otsuchi Marine Research Center, Ocean Research Institute, The University of Tokyo for their assistance in collecting specimens. This work was supported in part by Grant-in-Aid No. 13760138 from the Ministry of Education, Culture, Sports, Science and Technology, Japan. Correspondence to:Takaomi Arai     

Optimal mechanisms for finding and selecting mates: how threespine stickleback (<Emphasis Type="Italic">Gasterosteus aculeatus</Emphasis>) should encode male throat colors

Male threespine stickleback (Gasterosteus aculeatus) use nuptial colors to attract mates and intimidate rivals. We quantified stickleback color and environmental lighting using methods independent of human perception to evaluate the information transmitted by male signals in a habitat where these signals are displayed. We also developed models of chromatic processing based on four cone photopigments (peak absorptions at 360, 445, 530, and 605 nm) characterized microspectrophotometrically in G. aculeatus and three other stickleback species. We show that a simple opponent mechanism receiving equally weighted inputs from cones with peak absorptions at 445 nm and 605 nm efficiently encodes variation in male throat colors. An orthogonal opponent mechanism—the difference between outputs of 530-nm cones and mean of outputs of 445- and 605-nm cones—produces a neural signal that could be used for species recognition and would be largely insensitive to variation in male throat color. We also show that threespine stickleback throats/photopigments are optimized for this coding scheme. These and other findings lead to testable hypotheses about the spectral processing mechanisms present in the threespine stickleback visual systems and the evolutionary interactions that have shaped this signal/receiver system.Abbreviations LWS long-wave sensitive - MWS middle-wave sensitive - SWS short-wave sensitive - UVS ultra-violet sensitive     

Increased ambient temperature alters the parental care behaviour and reproductive success of the three-spined stickleback (<Emphasis Type="Italic">Gasterosteus aculeatus</Emphasis>)

The effects of environmental warming on aquatic poikilotherms, such as fish, are likely to be manifest during periods of high metabolic demand. For species that invest heavily in parental-care, such as the three-spined stickleback, Gasterosteus aculeatus L., their reproductive success may be adversely affected. In two separate experiments with temperatures raised by 2°C to 6°C above 16–17°C ambient over a whole breeding season, we quantified changes to parental-care behaviour and the resultant reproductive success of G. aculeatus. As temperature increased, male parental-care behaviour was altered, particularly the fanning of the fertilised eggs. Fanning behaviour was highly variable among individual fish however it increased over the course of incubation. Furthermore, all egg incubating fish consistently fanned at a faster rate in higher temperatures. The male fish responded to the increased temperature by putting more effort into fanning. The consequence was that these fish had a higher rate of incubation failure and an increased likelihood of mortality. The pattern of alteration to parental care behaviour and decreased reproductive success with higher temperature was remarkably consistent across the individual fish, which suggests consequences at the population level of increased ambient temperatures.     

Unusual number of pectoral fin rays in an Icelandic population of threespine stickleback (<Emphasis Type="Italic">Gasterosteus aculeatus</Emphasis>) recently isolated in freshwater

Threespine stickleback most often have 10 pectoral fin rays, and it seems to be a highly canalized trait. We observed an unusually high frequency of stickleback with 11 pectoral fin rays in a population recently isolated from the marine environment in a freshwater lagoon in Iceland. These new morphologies may be beneficial for the fish in the new habitat but may disappear because of strong canalizing selection for the typical 10 pectoral fin rays.Co-ordinating editor: Kaitala     

Variations of life history strategy of the arctic lamprey <Emphasis Type="Italic">Lethenteron camtschaticum</Emphasis> from the Utkholok River (Western Kamchatka)

Morphobiological traits of the lamprey from the Utkholok River (Western Kamchatka) are investigated for the first time. All present forms of lamprey (typically anadromous, anadromous early maturing forma praecox, resident) do not differ by diagnostic characters and belong to one species Lethenteron camtschaticum. Males prevail among mature specimens of various forms, smolts, and ammocoetes at later developmental stages. The forma praecox is represented by males by 92%. A hypothesis is suggested explaining the relationships of the forms and the mechanism of realization of different types of life history strategy in relation to energy resources of water bodies and the kind of feeding of different groups of ammocoetes (organic detritus or Pacific salmon carcasses decomposed after spawning).     

Life cycle of <Emphasis Type="Italic">Uromyces appendiculatus</Emphasis> var. <Emphasis Type="Italic">azukicola</Emphasis> on <Emphasis Type="Italic">Vigna angularis</Emphasis>

Field observations and inoculation experiments revealed that Uromyces appendiculatus var. azukicola has an autoecious and macrocyclic life cycle and produces spermogonia, aecia, uredinia, and telia on Vigna angularis var. angularis and V. angularis var. nipponensis. From inoculation experiments, it was suggested that this rust fungus has different host relationships from other varieties. Morphological examinations revealed that the characteristics of urediniospores and teliospores are different among varieties, although aeciospores are morphologically similar to each other.Contribution no. 182, Laboratory of Plant Parasitic Mycology, Institute of Agriculture and Forestry, University of Tsukuba, Japan     

Enhanced ambient UVB light affects growth,body condition and the investment in innate and adaptive immunity in three-spined sticklebacks (<Emphasis Type="Italic">Gasterosteus aculeatus</Emphasis>)

With ongoing environmental change, ultraviolet-B radiation (UVB) reaching the Earth’s surface has increased over recent decades with consequences for terrestrial and also aquatic ecosystems. Despite evidence for direct physiological and immunological responses of aquatic animals following enhanced UVB exposure, studies investigating indirect impacts of ambient UVB radiation are scarce and mainly used only single doses and/or artificially high amounts of UVB. In the present study, the influence of chronic exposure to elevated UVB levels on growth, body condition and immune function was investigated in three-spined sticklebacks (Gasterosteus aculeatus). Fish were kept outdoors for 68 ± 2 days under two different spectral conditions; one group was exposed to natural solar radiation (UVB-normal), while the other group received additional UVB light for four hours daily (UVB-enhanced). Enhanced UVB radiation was within the range of UVB levels measured at the study site. Fish length and weight were determined at the beginning and end of the experiment to compare growth and body condition between the two treatment groups. At the end of the experiment, the splenosomatic index and the granulocyte-to-lymphocyte ratio were determined as immune parameters. Fish from the UVB-enhanced group showed a reduced growth and body condition as well as a lower splenosomatic index compared to the UVB-normal group. Furthermore, UVB-treated fish had a higher granulocyte-to-lymphocyte ratio representing a relatively higher activation of innate compared to adaptive immunity. Consequently, increased but ecologically relevant levels of ambient UVB negatively affect growth and body condition and have a considerable impact on immunity in three-spined sticklebacks.     

Changes in morphological characteristics of an introduced population of the threespine stickleback <Emphasis Type="Italic">Gasterosteus aculeatus</Emphasis> in Lake Towada,northern Japan

A freshwater population of the threespine stickleback Gasterosteus aculeatus occurs at an elevation of 400m in Lake Towada in the mountains of northern Japan. Morphological characteristics of each sex of this population were studied between 1985 and 1992. The 1985 fishes were larger in standard length than even anadromous populations, as well as all other freshwater populations, so the large body size of this population was unusual for the species. The population was also characterized by large ratios of head length, eye diameter, and gill raker length, and a higher ovary volume in 1992 than in 1985, but it was not readily characterized by meristic characters. The population may have been introduced within the last 20 years (probably in the early 1980s). The large body size of the population may not reflect a defense against predators because coexisting fishes were not important predators on threespine stickleback adults. It is supposed that the change of body size was induced by environmental changes in prey abundance in the lake and/or by the longevity of fishes.     

New combinations and typifications in <Emphasis Type="Italic">Bistorta</Emphasis>, <Emphasis Type="Italic">Persicaria</Emphasis>, <Emphasis Type="Italic">Polygonum,</Emphasis> and <Emphasis Type="Italic">Rumex</Emphasis> (Polygonaceae)

New combinations are proposed in anticipation of the Polygonaceae treatment in the forthcoming volume of Intermountain Flora: Polygonum kelloggii var. esotericum, P. kelloggii var. watsonii , Rumex densiflorus var. pycnanthus , R. salicifolius var. utahensis, and R. occidentalis var. tomentellus. Typifications are proposed to facilitate ongoing studies in Polygonaceae and to maintain current usage.     

Screening of population genetic SCAR markers for mykiss <Emphasis Type="Italic">Parasalmo</Emphasis> (<Emphasis Type="Italic">Oncorhynchus</Emphasis>) <Emphasis Type="Italic">mykiss</Emphasis> from Kamchatka

Using AP-PCR, the genome of Kamchatka mykiss (Parasalmo (O.) mykiss) was examined. Polymorphic fragments, implying geographic differences among the samples, were selected, cloned, and sequenced. Based on these sequences, longer, specific SCAR primers were selected and constructed. Using the BLAST software program, the sequences were analyzed for analogy to those from the GenBank database. It seemed likely that all sequences obtained belonged to earlier unexamined repeated sequences, variable in the populations of the species of interest. A total of seven SCAR markers, characterized by population-significant variability of the DNA products in Kamchatka geographic group of rainbow trout were constructed. These markers can be used for further investigation of the species Parasalmo (O.) mykiss. The SCAR marker sequences were deposited in GenBank under the accession numbers EU805500 to EU805506.     

<Emphasis Type="Italic">Ty</Emphasis>1<Emphasis Type="Italic">/copia</Emphasis>- and <Emphasis Type="Italic">Ty</Emphasis>3<Emphasis Type="Italic">/gypsy</Emphasis>-like DNA sequences in <Emphasis Type="Italic">Helianthus </Emphasis>species

Two repeated DNA sequences isolated from a partial genomic DNA library of Helianthus annuus, p HaS13 and p HaS211, were shown to represent portions of the int gene of a Ty3 /gypsy retroelement and of the RNase-Hgene of a Ty1 /copia retroelement, respectively. Southern blotting patterns obtained by hybridizing the two probes to BglII- or DraI-digested genomic DNA from different Helianthus species showed p HaS13 and p HaS211 were parts of dispersed repeats at least 8 and 7 kb in length, respectively, that were conserved in all species studied. Comparable hybridization patterns were obtained in all species with p HaS13. By contrast, the patterns obtained by hybridizing p HaS211 clearly differentiated annual species from perennials. The frequencies of p HaS13- and p HaS211-related sequences in different species were 4.3x10(4)-1.3x10(5) copies and 9.9x10(2)-8.1x10(3) copies per picogram of DNA, respectively. The frequency of p HaS13-related sequences varied widely within annual species, while no significant difference was observed among perennial species. Conversely, the frequency variation of p HaS211-related sequences was as large within annual species as within perennials. Sequences of both families were found to be dispersed along the length of all chromosomes in all species studied. However, Ty3 /gypsy-like sequences were localized preferentially at the centromeric regions, whereas Ty1/ copia-like sequences were less represented or absent around the centromeres and plentiful at the chromosome ends. These findings suggest that the two sequence families played a role in Helianthusgenome evolution and species divergence, evolved independently in the same genomic backgrounds and in annual or perennial species, and acquired different possible functions in the host genomes.     

Diel vertical movements,and effects of infection by the cestode <Emphasis Type="Italic">Schistocephalus solidus</Emphasis> on daytime proximity of three-spined sticklebacks <Emphasis Type="Italic">Gasterosteus aculeatus</Emphasis> to the surface of a large Alaskan lake

We conducted a field study in Iliamna Lake, Alaska, to test the hypothesis that proximity of three-spined sticklebacks Gasterosteus aculeatus to the lake’s surface during the daytime varies with macroparasitic cestode parasite Schistocephalus solidus infection in a manner consistent with enhanced vulnerability to avian predators. Extensive sampling in the lake and likelihood-based modeling revealed that sticklebacks displayed a diel vertical migration, being closer to the surface at night than during the evening and early morning. Additional sampling, also coupled with a likelihood-based modeling approach, showed that fish caught at the surface of the lake during the day were more often parasitized (76 vs. 65%), more heavily parasitized (26.8 vs. 22.7% of their body mass), and had larger individual parasites (0.24 vs. 0.20 g) than those caught at night. Parasite infection was related, non-linearly, to fish size, which also differed between day and night sampling at the surface. We performed statistical competitions among nested hierarchies of models that accounted for this effect of length. The most likely models indicated that fish captured during the day had greater parasite prevalence, higher parasite burdens, and larger parasites than did fish captured at night. Proximity to the surface during the day in this very clear lake would likely increase the vulnerability of sticklebacks to predation from birds, enabling completion of the parasite’s lifecycle.     

Expression patterns of class I <Emphasis Type="Italic">KNOX</Emphasis> and <Emphasis Type="Italic">YABBY</Emphasis> genes in <Emphasis Type="Italic">Ruscus aculeatus</Emphasis> (Asparagaceae) with implications for phylloclade homology

STM (RaSTM) and YAB2 (RaYAB2) homologues were isolated from Ruscus aculeatus (Asparagaceae, monocots), and their expressions were analyzed by real-time polymerase chain reaction (PCR) to assess hypotheses on the evolutionary origin of the phylloclade in the Asparagaceae. In young shoot buds, RaSTM is expressed in the shoot apex, while RaYAB2 is expressed in the scale leaf subtending the shoot bud. This expression pattern is shared by other angiosperms, suggesting that the expression patterns of RaSTM and RaYAB2 are useful as molecular markers to identify the shoot and leaf, respectively. RaSTM and RaYAB2 are expressed concomitantly in phylloclade primordia. These results suggest that the phylloclade is not homologous to either the shoot or leaf, but that it has a double organ identity.