| Symposium proposal |
| Organizer: | Kinya G. Ota (Academia Sinica, Taiwan) |
| animals. In particular, the breeding of ornamental animals has produced extremely diversified phenotypes. Goldfish (Carassius auratus) is a widely known representative example of this phenomenon, and early researchers (for example, Darwin and Bateson) were intrigued by this teleost species. Ornamental strains of goldfish were first established by breeders and fanciers in East Asia during the early middle ages, with tight connections existing between goldfish and the local cultural and geological characteristics. These ornamental animals were then spread all over the world due to their visual attractiveness and viability. This worldwide distribution and physiological robustness facilitated research in the fields of physiology, neuroscience, morphology, and developmental biology. However, there is currently little opportunity for goldfish researchers studying different topics to meet and discuss their progress. The main aim of this symposium is to congregate researchers who use goldfish in projects from diverse research fields, including evodevo, neuroscience, morphology, and genomics. The speakers will include Anne-Claire Fabre (Universität Zürich, Switzerland), who investigates goldfish morphological evolution using geometric morphometric approaches, Masayuki Yoshida (Hirosima Univ. Japan), who uses the goldfish to investigate brain activity and behavior, Yoshihiro Omori (Nagahama Institute of Bioscience and Technology, Japan), who applied genomics to identify mutated loci of ornamental morphology, and Kinya G. Ota (Academia Sinica, Taiwan), who works on goldfish evodevo. Researchers will present their own projects, exploring the general topic of how complicated phenotypes are changed under artificial selection. We hope that this symposium will enhance our understanding of the relationship between evolution of macro-phenotypes and different types of selection pressure. |
S13-1
A morphometric study of skull variation in Goldfishes: Morphospace expansion through domestication
Anne-Claire Fabre1, Dominic Stalder1, Marcelo R. Sánchez-Villagra1
1Palaeontological Institute and Museum, University of Zurich, 8006 Zurich, Switzerland
Previous studies on domesticated vertebrates have shown that they display a higher disparity (morphological diversity) in comparison to wild closely relative species. Dogs and pigeons represent extremes within their respective clades. Domesticated species of mammals and birds show some similar morphological changes in comparison to wild species (e.g., shortening of the anterior part of the neurocranium). It is to be tested if there are commonalities also in domestic fish diversification, and if these may result from underlaying similar developmental biases. Goldfish (Carassius auratus) display a tremendous diversity in shape, size, and color, and even unique innovations in their postcranial anatomy, but their skulls have never been systematically studied. 3D geometric morphometrics applied on data generated by non-invasive imaging serves to quantify patterns of variation. In this study, we explored the morphological variation of domesticated goldfish in comparison to wild cyprinids using the skull as a marker. To do so, we used a geometric morphometrics approach to quantify the neurocranial shape of five domesticated goldfishes and 10 wild species of Cyprinidae. Wild species were sampled in order to represent as much as possible the diversity in form and size (from less than 5 cm to over 1 meter), over a wide geographic distribution and the phylogeny. A total of 44 landmarks were taken in order to capture the diversity in form of the neurocranium. To compare shape independently from scale, size and location we performed a generalized Procrustes analyses. We evaluate the distribution of the species using a principal component analyses onto which the phylogeny was mapped. We assess the impact of size on shape using a phylogenetic generalized least square analysis. We assess the shape difference between domesticated and wild species using a MANOVA. Finally, we tested whether domesticated species are more disparate than wild cyprinid species using an analysis of disparity. Our preliminary results show that wild species have a higher disparity than domesticated ones. However, when taking into account the phylogeny, domesticated specimens showed 1.7 times more variation than the wild ones. Some morphological changes in goldfishes have also been recorded for other domesticated species. Expansion of the sampling will serve to test the whole magnitude of the shape changes, and examine how some areas of the morphospace have been explored. Specific areas of interest are the orbital rings, opercular series and masticatory apparatus. Moreover, extending beyond the skull, the Weberian apparatus is fully understudied in Goldfishes beyond the classic description of Watson.
Goldfish are just one example of the great potential of fish models to investigate patterns and processes of morphological diversification associated with domestication, given the advantages for experimental work, short life span and husbandry.
S13-2
Bold goldfish in behavioral neuroscience
Masayuki Yoshida1
1Graduate School of Integrated Sciences for Life, Hiroshima University
Goldfish Carassius auratus have been used in a wide range of studies in the behavioral neuroscience field. Besides the ease of keeping and breeding them, the “boldness” of the goldfish in artificial situations makes researchers able to use them in various behavioral tests and neurophysiological manipulations. Given this advantage, we have used goldfish to study the neural bases of emotional fear learning. Goldfish were trained to acquire classical conditioned cardiac deceleration, a measure of conditioned fear, using the delay conditioning paradigm: light conditioned stimulus and electric-shock unconditioned stimulus. This procedure was successful even in a goldfish immobilized by neuromuscular blockade, enabling us to apply surgical and physiological manipulations to the subject fish. It is known that, in mammals, the telencephalon, namely the amygdala, and the cerebellum are both required in this type of classical fear conditioning. In teleost fish including goldfish, on the other hand, it has been found that although an intact cerebellum was essential for the acquisition of conditioned fear responses, ablation of the telencephalon did not impair learning. Cerebellar neural circuits are well conserved through vertebrate evolution, and hence the cerebellum is suggested to be an “old” center for fear conditioning, while the telencephalon is possibly a new player in this type of learning. This calls to mind the relationship of the mesencephalon and cerebral cortex in visual processing. We further investigated the behavior of cerebellar neurons in classical fear conditioning in goldfish. We have found that a particular class of cerebellar neurons, Purkinje cells, shows fear-learning-dependent plastic changes, suggesting the change in the pattern of responses in this type of neuron to unconditioned stimulus is a part of the neural representation of classical conditioned fear. It is probable that the above findings could not be obtained using “wild” Carassius, such as the ginbuna Carassius auratus langsdorfii.
S13-3
Diversity of morphological phenotypes in domesticated goldfish strains and their whole genome analysis
Yoshihiro Omori1, Tetsuo Kon1, Kentaro Fukuta2, Atsushi Toyoda3, Hideki Noguchi2,4
1Laboratory of Functional Genomics, Graduate School of Bioscience, Nagahama Institute of Bioscience and Technology
2Center for Genome Informatics, Joint Support-Center for Data Science Research, Research Organization of Information and Systems
3Comparative Genomics Laboratory, National Institute of Genetics
4Advanced Genomics Center, National Institute of Genetics
The goldfish (Carassius auratus) is a domesticated cyprinid teleost, which was domesticated from wild goldfish during the Chinese Song Dynasty (960–1279). During the 1,000-year breeding history of goldfish strains, a wide variety of coloration and body, fin, eye, hood, and scale morphologies of the strains were established mainly in China and Japan. Currently, there are approximately 200 variants and 80 genetically established goldfish strains all over the world. Together with the diverse phenotypes, goldfish are also interesting from evolutionary perspectives because their genome experienced a recent whole-genome duplication (WGD) event. However, the contribution of WGD to genetic and phenotypic diversity in goldfish strains has been poorly understood. Recently, we generated a high-quality reference sequence of the goldfish genome by using long-read DNA sequencing technology. We identified the 50 chromosomes which were further divided into the L- and S- subgenomes. We observed asymmetric subgenome evolution in the goldfish genome; the L-subgenome is preserved to stay more similar to the ancestral state, whereas the S-subgenome experiences more gene losses. We performed whole-genome sequencing of various goldfish strains bred in Japan. Genome-wide association studies (GWAS) and analysis of strain-specific variants showed genetic loci associated with several goldfish phenotypes, including the dorsal fin loss, long-tail, telescope-eye, albinism, and heart-shaped tail. We would like to discuss the relationship between accumulated mutations in the asymmetrically evolved subgenomes and the generation of diverse phenotypes in the goldfish domestication history.
S13-4
Discontinuous morphological evolution in ornamental goldfish
Kinya Ota1
1Yilan Marine Research Station, ICOB, Academia Sinica, Taiwan
Peculiar morphologies of ornamental goldfish have intrigued early biologists in the fields of evolutionary biology. For example, twin-tail ornamental goldfish strains gave Bateson, one of the most influential early biologists, insight into how animal morphologies can change over time nature. Bateson used the variations of twin-tail morphology to exemplify discontinuous variation in his protest against Darwin’s gradual evolution hypothesis, suggesting that this teleost species is suitable for the study of morphological evolution. However, ornamental goldfish has not been examined in the context of evolutionary developmental biology. Here, we discuss how discontinuous morphological evolutions can be caused by continuous changes of gene expression patterns and molecular developmental process in ornamental goldfish, based on our recent studies in twin-tail goldfish. We will also discuss other examples of discontinuous morphological evolution in ornamental goldfish, in aiming to establish this teleost species as a model animal for the research of drastic morphological evolution.
S13-5
Developmental mechanisms change for morphological transition from midline single to paired bilateral status in vertebrate ventral appendages
Gembu Abe1
1Graduate School of Life Sciences, Tohoku University, Japan
Vertebrates have various appendages, which have been evolved for their own lifestyle, modified by natural and/or artificial selection. The twin-tail goldfish shows the representative example: bilaterally paired anal and caudal fins. Our previous molecular genetic study revealed that a stop codon mutation in one of the two recently duplicated chordin genes is important for the highly diverged fin morphology. This allowed us to discuss how the twin-tail morphology was established and how genome duplication is related to morphological evolution. However, some issues still need to be discussed in the context of evolutionary developmental biology. For example, the relationship between the bifurcated anal and caudal fins of twin-tail goldfish and paired fins (pectoral and pelvic fins) had been argued by some early researchers, but no subsequent researchers have provided a further discussion on this topic. In this talk, we present an overview of the early anatomical and embryological studies of twin-tail goldfish, and of recent progress in molecular developmental mechanisms in the twin-tail goldfish and zebrafish relating mutants. We will also discuss the relationship between the twin-tail phenotype and the paired fins in embryonic development, and postulate how the paired fin acquisition might have occurred.
