Occurrence of deformed fish and their fitness-related traits in Kirikuchi charr, Salvelinus leucomaenis japonicus, the southernmost population of the genus Salvelinus

Kirikuchi charr, Salvelinus leucomaenis japonicus, is the southernmost population of the genus Salvelinus. It is endemic to the Kii Peninsula, central Honshu Island, Japan. As a consequence of anthropogenic disturbances, a few populations of Kirikuchi charr with low genetic diversity now survive only in small, isolated habitats. This study investigated the occurrence of deformed individuals and assessed differences between deformed and nondeformed fish in fitness-related traits, i.e., body size, body condition, growth rate, reproductive traits, survival rate, and habitat use, for two small isolated populations of Kirikuchi charr in the upper drainage of the Totsu River system of the Kii Peninsula. The two populations contained deformed fish in the respective proportions of 8.0-17.4% and 3.0-5.8% between 2003 and 2005. Annual survival rates of deformed fish were approximately half those of nondeformed fish. Other traits were not significantly different between deformed and nondeformed fish. These results indicate that the occurrence of deformities is an important ecological indicator that reflects the decline in fitness of small, isolated populations.     

Occurrence of mature male white-spotted charr (Salvelinus leucomaenis) in spring,an unusual season

Ichthyological Research -     

Incidence of a skeletal deformity (truncated upper jaw) in an isolated population of white-spotted charr Salvelinus leucomaenis

Although dorsal and caudal fin deformities (curvature), abnormal body color patterns, and fluctuating asymmetry of meristic characters have been previously reported for white-spotted charr (Salvelinus leucomaenis), the incidence of skeletally deformed individuals in the wild are extremely rare. Here, we report on skeletally deformed individuals of white-spotted charr with extremely truncated upper jaw, in a headwater reach of the Yoneshiro River, northern Honshu, Japan. In this study, we examined the genetic diversity of deformed and non-deformed populations of white-spotted charr using polymorphic microsatellite DNA markers. We also compared individual growth histories of deformed individuals with normal individuals using a back-calculation of fish lengths at previous ages from otolith annuli. We collected 41 and 100 individuals from the below- and above-waterfall sites, respectively. Of these, two individuals from the above-waterfall site were skeletally deformed, whereas the other individuals had a normal morphology. Microsatellite DNA genetic diversities of the above-waterfall population were notably lower than those of the just below-waterfall population. Individuals of the above-waterfall population had significantly higher internal relatedness and lower standardized heterozygosity values compared with those of the below-waterfall population, indicating higher inbreeding situation of the above-waterfall individuals compared with individuals in the below-waterfall site. Back-calculation of individual growth using otoliths revealed that deformed individuals grew significantly slower than sympatric normal individuals. Although incidence of deformed individuals in the wild might be related with accumulated inbreeding as suggested for other fishes, mechanisms for their long-term persistence in the wild remain unclear.     

Marine growth and survival of white-spotted charr,Salvelinus leucomaenis, in relation to smolt size

The relationships between marine growth and survival, and smolt sizes were examined for white-spotted charr (Salvelinus leucomaenis) populations in the Nairo River, Rebun Island, off northern Hokkaido Island, and the Haraki River, southern Hokkaido Island, Japan. Smolts in the Haraki River were much larger in size than those in the Nairo River, despite being similar size among age cohorts and between the sexes in each population. From scale analyses, smolt size-specific growth rates and survival were estimated by utilizing both observed and back-calculated size-frequencies. Inverse correlations between specific growth rates at sea and smolt size were found in both populations. However, the expected size increments at a given size of smolts in the Haraki River were significantly larger than of those in the Nairo River. For both populations, there were no significant effects of smolt ages (2 to 5 or 6 years) on growth rates at sea. Larger smolts had a consistent survival advantage, although the degree of size-dependent survival function seemed to differ between populations. The results suggested that growth and survival of individuals at sea are determined ultimately by size-, rather than age-, dependent factors depending upon local environmental conditions, supporting the hypothesis of a threshold size for smolting within populations.     

Genetic diversity and population structure of white-spotted charr, Salvelinus leucomaenis, in the Lake Biwa water system inferred from AFLP analysis

The genetic variations—and the time dependence of such variations—of natural populations of the white-spotted charr ,Salvelinus leucomaenis, in the Lake Biwa water system as well as those of a hatchery-reared population were inferred from AFLP. Upon the application of principal coordinate analysis using 118 polymorphic AFLP fragments based on the Jaccard similarity index, specimens of each of six natural local populations from the inlet rivers of Lake Biwa grouped roughly together, suggesting that each local population was genetically differentiated. The hatchery-reared population was shown to be closely related to the local population in the Seri River, suggesting that the Seri River population originated from hatchery-reared charr due to extensive stocking. Furthermore, specimens of the Yasu River grouped in a somewhat different position from the other natural populations, agreeing well with its geographic distance from the other populations. The nucleotide diversities of six natural populations (Harihata River, Ishida River, two reaches of the Takatoki River, Ane River, and Yasu River) in 2002 or 2003 were relatively low (π = 0.067–0.146%) compared with that of the Seri River (0.278%) and the hatchery-reared charr (0.316%). The nucleotide diversity in the five local populations (Ishida River, two reaches of the Takatoki River, Ane River, and Yasu River) remained at a low level from 1994 to 2002/2003, but only the nucleotide diversity in the Harihata River actually decreased. From 1994 to 2002/2003, the nucleotide diversity in the Seri River remained at a higher level among the natural populations from 1994 to 2002/2003; it was enhanced by the artificial release of hatchery-reared charr before 1994. In order to conserve the genetic diversity of the white-spotted charr in the Lake Biwa water system, it is necessary to prevent the stocking of hatchery-reared charr in reaches where hatchery-reared charr have not previously been stocked.     

Immunohistochemical demonstration of urotensins I and II in the caudal neurosecretory system of the Japanese charr,Salvelinus leucomaenis,retained in sea water

This paper is concerned with part of the role and function of the caudal neurosecretory system of the charr,Salvelinus leucomaenis, studied by immunohistochemistry. In order to elucidate the different histologic changes, we examined the immunoreactivities of urotenisn I (UI) and urotensin II (UII) in 3 experimental groups: the feral (river) fish, the fresh-water aquarium-, and sea water aquarium-retained fish. Coexistence of UI and UII was demonstrated in most of the smaller and larger neurons distributed in and near the urophyseal system of all 3 groups. However, some of the larger neurons were immunoreactive only to a single hormone, UI or UII. Merely a few neurons indicated no reactivity for either UI or UII. No such clearcut differences were encountered immunohistochemically in the 3 groups. Neuronal and urophysial immuno-reactivity to UI of feral and fresh-water-retained fish was slightly stronger than that of sea water-retained fish. Moreover, in sea water-retained fish, the intensity of immunoreactivity for UI was variable, and the number of neurons positive for UII only was somewhat larger than that in feral and fresh-water-retained fish. A series of UII-positive cerebrospinal fluid (CSF)-contacting neurons were seen in the ependymal and subependymal layers ventral to the central canal of the spinal cord in every group. These CSF-contacting neurons might constitute another neurosecretory system aside from the ordinary caudal neurosecretory system equipped with urophysis. In contrast to the hypothalamohypophysial neurosecretory system, the caudal neurosecretory system did not show any significant changes among the 3 groups. This suggests that urotensins I and II have no essential role in osmoregulation of the charr.     

Introgressive hybridization between Dolly Varden Salvelinus malma and white‐spotted charr Salvelinus leucomaenis on Hokkaido Island, Japan

Intra‐ and interspecific phylogenetic analysis of Dolly Varden Salvelinus malma and white‐spotted charr Salvelinus leucomaenis throughout Hokkaido Island was conducted using nucleotide sequences of the mitochondrial DNA control region and three nuclear DNA markers [ribosomal DNA (ITS‐1), microsatellite ( u ‐85), SINE ( Fok ‐223)]. A total of 19 mtDNA haplotypes from 271 individuals of Dolly Varden, nine haplotypes from 134 white‐spotted charr were defined, and identified two well‐supported monophyletic clades for each species. Two haplotypes of Dolly Varden, however, were clustered together in the white‐spotted charr clade. Those haplotypes were found only from several rivers in the Shiretoko Peninsula, and a neighbouring river of that region. Analyses of ribosomal DNA and Fok ‐223 loci revealed that both species are characterized by having completely species‐specific diagnostic sequence and fragment patterns. Dolly Varden of the Shiretoko populations are typically allopatric in distribution where white‐spotted charr do not currently occur. In addition, incongruence in genetic relationships between mtDNA and nuclear DNA markers give strong evidence of historical mtDNA introgression between Dolly Varden and white‐spotted charr. Some white‐spotted charr diagnostic alleles in a nuclear microsatellite locus ( u ‐85) were found in some Shiretoko Dolly Varden populations, suggesting that introgressive hybridization might have also occurred in relatively recent contact and potentially ongoing evolutionary event. The present study presents an example of historical hybridization and introgression at the southernmost distribution limits of Dolly Varden.     

Alternative mating tactics of arctic charr,Salvelinus alpinus,in Thingvallavatn,Iceland

Synopsis During the spawning season the operational sex ratio of the large benthivorous (LB) arctic charr morph in Thingvallavatn is skewed in favour of males which compete intensely on the spawning site. The skewness is caused by males staying longer on the spawning ground than females. LB males employ two mating tactics. Either they guard the female or they attempt sneak-matings with guarded females. The tactics seem to obey a pure conditional strategy where relative size is the important criterion. Generally, the larger males use the guarding tactic and the smaller the sneaking tactic. Assessment of size is a part of the strategy. Relative size influences male behaviour irrespective of which tactic they employ. Guarding is more successful when courting is considered, both with respect to relative frequency and duration of courting acts. Females are aggressive towards the sneakers especially when they are small. This could be interpreted as female choice in favour of large males, but also as a defence against egg predation. A small dwarflike benthivorous morph (SB) is found in the same area. It is mainly active during night and on rare occasions SB-males are seen sneaking into the nest of LB-females. In such cases they are attacked vigorously by both LB sexes.     

Behaviour of Arctic charr Salvelinus alpinus during an induced mating season in captivity: how male relative size influences male behavioural investment and female preference over time

The behaviour of sexually mature Arctic charr Salvelinus alpinus specimens (fifth farm generation) was observed in captivity for four consecutive days. Only agonistic interactions between males of different size were facilitated on the first 2 days, while both agonistic and courtship interactions were possible from the third day up to the end of the experiment. The reliability of behavioural analysis was assessed in order to reduce the possibility of observer errors within the generated datasets. The behavioural investment of big males, small males and females was analysed using general linear models (two‐way repeated measures ANOVAs with time and male size as factors). A peak in the agonistic interactions between males occurred during the first day of interactions, where the agonistic investment of big males was significantly higher than that of small males. This resulted in an increased investment in submissive behaviour by the small males, who consistently performed submissive behaviours from the second day of interactions up to the end of the trial. Big males were found to invest significantly more than small males in courtship behaviours for the duration of the trial. Even though females performed inter‐sexual behaviours towards both big and small males for the entire observation period, female interaction rate towards big males was higher than towards small males. This study suggests that both male investment in mating behaviour and female preference might be related to male characteristics such as body length and that S. alpinus behavioural patterns and mate choice cues might be strongly context‐related and characterized by high levels of behavioural plasticity (i.e. presence–absence of certain behavioural units or potential reversal of a mate choice cue) within the same species. Finally, in light of this, some conservation measures are discussed. In particular, effective management plans should take into account the high level of behavioural plasticity likely to be occurring in this species.     

Effect of ozone exposure on the compositions of gill and erythrocyte membrane lipids and proteins of Japanese charr (Salvelinus leucomaenis)

• 1.1. Compositions of lipids and proteins of erythrocytes (RBC) and gills from Japanese charr (Salvelinus leucomaenis) which were exposed to 0.4 and 0.7 ppm ozone for 30 min were compared with those of the control.
• 2.2. On exposure to ozone, both RBC and gill membrane phospholipid content, especially phosphatidylethanolamine (PE), dropped.
• 3.3. The decrease of PE was brought about by the decrease of docosahexaenoic acid content which comprised the major component of PE.
• 4.4. RBC membrane protein with 215 and 225 kDa, which is equivalent to cytoskeletal protein, selectively disappeared on exposure to ozone.

     

Aphanomyces frigidophilus sp. nov. from eggs of Japanese char,Salvelinus leucomaenis

Aphanomyces frigidophilus sp. nov. was obtained from eggs of Japanese char,Salvelinus leucomaenis, from Tochigi Prefectural Fisheries Experimental Station, Utsunomiya, Japan. Vegetative hyphae were delicate, slightly wavy, moderately branched. Zoosporangia were isodiametric with the vegetative hyphae. Oogonia were abundant, originating on short stalks from lateral sides of hyphae. Oogonia were spherical, subspherical or pyriform, with a single subcentric oospore inside. Outer surfaces of oogonia were roughened with short papillate, crenulate or irregular ornaments. Antheridia and oospore germination were not observed. Zoospore germination and vegetative growth were found from pH 5.0 to 11.0. Zoospore production was highest at 10°C, whereas rapid growth occurred at 20–25°C. Vegetative growth of the fungus declined from the maximal level at 25°C to less than half maximal at 30°C and completely disappeared at 35°C.     

Spatial and temporal changes in genetic structure and diversity of isolated white-spotted charr (Salvelinus leucomaenis) populations

Hydrobiologia - In Japan, numerous artificial dams constructed for erosion control or hydroelectric power generation have affected almost all rivers and resulted in isolation and fragmentation of...     

Estrogen-responsive neural circuits governing male and female mating behavior in mice

Decades of knockout analyses have highlighted the crucial involvement of estrogen receptors and downstream genes in controlling mating behaviors. More recently, advancements in neural circuit research have unveiled a distributed subcortical network comprising estrogen-receptor or estrogen-synthesis-enzyme-expressing cells that transforms sensory inputs into sex-specific mating actions. This review provides an overview of the latest discoveries on estrogen-responsive neurons in various brain regions and the associated neural circuits that govern different aspects of male and female mating actions in mice. By contextualizing these findings within previous knockout studies of estrogen receptors, we emphasize the emerging field of “circuit genetics”, where identifying mating behavior-related neural circuits may allow for a more precise evaluation of gene functions within these circuits. Such investigations will enable a deeper understanding of how hormone fluctuation, acting through estrogen receptors and downstream genes, influences the connectivity and activity of neural circuits, ultimately impacting the manifestation of innate mating actions.     

Segregation in spawning and early life history among polymorphic Arctic charr, Salvelinus alpinus, in Thingvallavatn, Iceland

The relationships among time of spawning, incubation temperature, timing of first feeding and early growth were examined in four sympatric morphs of Arctic charr in Thingvallavatn, Iceland. Large benthivorous charr spawn in July-August at sites with cold ground-water flow. Planktivorous and piscivorous charr spawn in September-November and are not confined to ground-water sites. The spawning of small benthivorous charr overlaps with that of other morphs. Progeny of large benthivorous charr start feeding 2-3 months earlier than the progeny of autumn spawners. This results in differential size distribution and growth rates of young in the spring.     

日本食蚧蚜小蜂的交配行为及雌蜂生殖系统观察

日本食蚧蚜小蜂Coccophagus japonicus Compere是橡副珠蜡蚧Parasaissetia nigra Nietner的优势寄生蜂之一,为明确其交配行为及雌蜂生殖系统构成,本研究在室内观察了该蜂的交配行为、雄蜂交配能力、雌蜂生殖系统等。结果表明:日本食蚧蚜小蜂的交配过程可分为交配前行为、交配、交配后行为3个阶段,整个交配过程平均时间为76.2 s,其中,交配时间为20.6 s;小蜂羽化当天即可交配,雌、雄蜂具有多次交配的习性,雄蜂的交配能力随其日龄的增加而减弱,1日龄的雄蜂交配能力最强,为6.3次/d,雄蜂一生平均能交配36.9次;雌蜂的生殖系统由1对卵巢、1对侧输卵管、1条中输卵管、1个受精囊和外生殖器等组成,卵巢管数量存在变异,其中95.78%雌蜂卵巢具6(3+3)条卵巢管,2.78%雌蜂卵巢具5(3+2)条卵巢管,1.22%的雌蜂卵巢具7(3+4)条卵巢管,0.22%的雌蜂卵巢是具4(2+2,1+3)条卵巢管,还有极个别的雌蜂仅有1个卵巢,由3条卵巢管组成。研究结果表明日本食蚧蚜小蜂有多次交配习性,卵巢存在一定变异。     

Effects of water depth and structural complexity on survival and settlement of white-spotted charr (Salvelinus leucomaenis)

Hydrobiologia - Both climate change and dam operations are affecting water levels in river systems worldwide and their influence can be especially drastic in upper streams, where juvenile salmonids...     

Daily patterns of courtship and mating behavior in the male Japanese quail

Crowing behavior was monitored constantly in male Japanese quail housed singly over 30 successive days. The photoperiod was 16h of light and 8 h of dark. A daily pattern in crowing was observed in which the frequencies were elevated in the afternoon and at the beginning of darkness. However, peak crowing occured 2 h prior to the onset of light. These rhythms were highly correlated among individuals and extremely repeatable over the sequential days of observation.In a second experiment, males which were paired with females were observed for frequencies of crowing, courtship, and mating behavior during the lighted portion of the day. In this experiment, the same photoperiod (16L:8D) was maintained. Paired males exhibited a daily pattern in crowing similar to that observed in the singly housed males. The frequency of mating was the highest between 1200 and 1300 h and lowest at 1400 h. Mating success was highest at midday, as were the number of males exhibiting mating behavior. These diurnal patterns in sexual behavior may depend on environmental cues such as photoperiod, which, in turn, may stimulate endocrine triggers.