108 research outputs found
Social system, reproduction of helpers and sperm competition in the cooperatively breeding fishes (Julidochromis spp.) in Lake Tanganyika
No full textTestis size depends on social status and the presence of male helpers in the cooperatively breeding cichlid Julidochromis ornatus
No full textCooperatively breeding animals, in which helpers may participate in reproduction with dominant breeders, are ideal species for examining intraspecific variation in testis size because they often exhibit both monogamous breeding (low risk of sperm competition) and polyandrous breeding (high risk) within a population. However, little is known about testis investment as a result of sperm competition in these animals. The substrate-brooding cichlid fish Julidochromis ornatus has a cooperatively breeding system, in which some males mate monogamously and other males reproduce as dominant breeders or helpers within cooperatively breeding groups, in which male helpers frequently sire young. We examined the relationship between testis investment and male social status in relation to the risk of sperm competition. As predicted from sperm competition models, in groups with male helpers, both the male breeders and the male helpers invested more in testes mass, compared to breeding males without male helpers. We also found a positive relationship between the testes mass of male breeders and their male helpers, suggesting that males increase their investment in reproductive capability under the risk of sperm competition. Sperm competition models also predict that larger testes are associated with increased siring success. Our paternity analysis supported this prediction; we found a positive relationship between testis investment by male helpers and the number of offspring they sired. Copyright 2006.cooperative breeding; Lake Tanganyika; paternity; social status; sperm competition risk; testis investment
Seasonal occurrence and sexual maturation of Japanese pygmy squid (Idiosepius paradoxus) at the northern limits of their distribution
No full textThe distribution of aquatic animals is severely limited by water temperature. However, little is known about migration pattern, over-wintering and reproduction at the northern limits of their distribution. To investigate the sexual maturation of the Japanese pygmy squid (Idiosepius paradoxus) and its ability to survive during winter at the northern limits of its distribution, we conducted monthly collections at Usujiri in northern Japan and carried out low temperature tolerance experiments. Squids were collected only during four months in autumn and early winter. In autumn, all squids were large and sexually mature, and many egg masses were found on the surface of seagrass, whereas in early winter, only small immature squids were collected. A warm northward-flowing current reached near Usujiri in autumn. These results suggest that squids were transported by the current and some small squids were recruits that hatched at Usujiri. Field data and low temperature tolerance experiments showed that I. paradoxus can not survive in the low seawater temperature that occurs at Usujiri in winter. The migration pattern in I. paradoxus may differ from the major pattern where young fish are passively transported and never reproduce at the northern limits
Group composition, relatedness, and dispersal in the cooperatively breeding cichlid Neolamprologus obscurus
No full textInsufficient data render comparative analyses of the evolution of cooperative breeding mere speculation: A reply to Dey et al.
No full textOnly children by choice vs. only children by circumstances: why do some women have only one child?
No full textIn an attempt to stimulate further theory and research on only children, we introduce two conceptual distinctions: Only children as independent variables vs. only children as dependent variables; and only children by choice vs. only children by circumstances. What little scientific research exists on only children to date focuses almost exclusively on only children as independent variables and fails to make a distinction between only children by choice and only children by circumstances. A focus on only children by choice as dependent variables explores the question of why some women choose to have only one child. As an empirical illustration, analyses of prospectively longitudinal data with a nationally representative sample in the United Kingdom (National Child Development Study) show that women who experience pregnancy complications are significantly less likely to have another child and significantly more likely to have only one child. Our results suggest that increased chances of pregnancy complications that American women now experience alone can explain about 10% of the increase in the number of only children in the United States in the last half century. If certain genes incline women to have pregnancy complications, it is possible that only children by circumstances are genetically more similar to children with siblings than to only children by choice
Prognostic phenotypic and genotypic factors associated with photodynamic therapy response in patients with age-related macular degeneration
No full textTakashi Tsuchihashi,1 Keisuke Mori,1 Kuniko Horie-Inoue,2 Yasushi Okazaki,3 Takuya Awata,4,5 Satoshi Inoue,2 Shin Yoneya1 1Department of Ophthalmology, 2Division of Gene Regulation and Signal Transduction, Research Center for Genomic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA; 3Division of Translational Research, Research Center for Genomic Medicine, 4Division of Endocrinology and Diabetes, Department of Medicine, 5Division of RI Laboratory, Biomedical Research Center, Saitama Medical University, Iruma, Saitama, Japan Background: This study aimed to demonstrate the phenotypic and genotypic factors associated with photodynamic therapy (PDT) for age-related macular degeneration (AMD).Methods: The study included 149 patients with exudative AMD treated by PDT. Eight phenotypic factors and ten genotypic factors for three single nucleotide polymorphisms (SNPs; rs800292, rs1061170, rs1410996) in the complement factor H (CFH) gene, rs 11200638-SNP in the high temperature requirement A-1 (HTRA1) gene, two SNPs (rs699947, rs2010963) in the vascular endothelial growth factor (VEGF) gene, and four SNPs (rs12948385, rs12150053, rs9913583, rs1136287) in the pigment epithelium-derived factor (PEDF) gene were evaluated. Results: A significant association with best-corrected visual acuity change was demonstrated in the greatest linear dimension, presence or absence of pigment epithelial detachment, and HTRA1-rs11200638 genotype statistically (P=3.67×10-4, 1.95×10-2, 1.24×10-3, respectively). Best-corrected visual acuity in patients with AA genotype of HTRA1-rs11200638 significantly decreased compared with that in patients with GG genotype (P=1.33×10-3). Logistic regression analyses demonstrated HTRA1-rs11200638 genotype was most strongly associated with best-corrected visual acuity outcome from baseline at 12 months after photodynamic therapy (P=4.60×10-3; odds ratio 2.363; 95% confidence interval 1.303–4.285).Conclusion: The HTRA1-rs11200638 variant showed the most significant association. Therefore, this variant may be used as a prognostic factor to estimate the PDT response with significant predictive power. Keywords: age-related macular degeneration, photodynamic therapy, phenotypic and genotypic factors, high temperature requirement A-1, greatest linear dimension, pigment epithelial detachmen
Niche differentiation depends on body size in a cichlid fish: a model system of a community structured according to size regularities
No full textThe dynamics of dissolved organic carbon concentration at the mountainous river in Japan
No full textEvolutionary transitions to cooperative societies in fishes revisited
No full textUnravelling the evolution of complex social organization in animals is an important aim, not least because it helps to understand the evolutionary roots of human sociality. Recent advances in comparative methods allow to approach this question in a phylogenetic context. The validity of such comparative approaches depends strongly on the quality of information regarding the behaviour, sociality, and reproduction of animals in natural systems, and on the quality of the phylogenetic reconstruction. Applying a novel comparative approach, a recent study of Dey et al. (2017, Nature Ecology & Evolution, 1, 137) concluded that evolutionary transitions to cooperative breeding in cichlid fishes were not associated with the social mating pattern. Here we argue that this result was adversely affected by equivocal classifications of mating patterns, and inadequate phylogenetic data. In order to illustrate the impact of the mating system misclassifications, we scored mating patterns as reported in the original literature and re‐analysed the dataset based on Dey et al.’s tree topology. The result suggests that the mating system does in fact significantly explain the evolutionary transition to cooperative breeding in lamprologine cichlids, but we submit that a reliable conclusion cannot be reached before improving the behavioural information and the underlying phylogenetic reconstruction. The problems identified in this case study are not unique and we urge caution in the interpretation of results from comparative phylogenetic studies in general. We do agree with Dey et al. (2017) though that the lamprologine cichlids of Lake Tanganyika may constitute a fundamental test case for the theory of social evolution, but better information on their behaviour and phylogenetic relationships is needed to allow meaningful analyses
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