Biology subjects

Hatashima, R.

Publications and source records attributed to Hatashima, R..

2 recordsLinked to original sources

bioRxiv2024

Pronounced expression of extracellular matrix proteoglycans regulated by Wnt pathway underlies the parallel evolution of lip hypertrophy in East African cichlids

Cichlid fishes inhabiting the East African Great Lakes, Victoria, Malawi, and Tanganyika, are textbook examples of parallel evolution, as they have acquired similar traits independently in each of the three lakes during the process of adaptive radiation. In particular, "hypertrophied lip" has been highlighted as a prominent example of parallel evolution. However, the underlying molecular mechanisms remain poorly understood. In this study, we conducted an integrated comparative analysis between the hypertrophied and normal lips of cichlids across three lakes based on histology, proteomics, and transcriptomics. Histological and proteomic analyses revealed that the hypertrophied lips were characterized by enlargement of the proteoglycan-rich layer, in which versican and periostin proteins were abundant. Transcriptome analysis revealed that the expression of extracellular matrix-related genes, including collagens, glycoproteins and proteoglycans, was higher in hypertrophied lips, regardless of their phylogenetic relationships. In addition, the genes in Wnt signaling pathway, which is involved in promoting proteoglycan expression, was highly expressed in both the juvenile and adult stages of hypertrophied lips. Our comprehensive analyses showed that hypertrophied lips of the three different phylogenetic origins can be explained by similar proteomic and transcriptomic profiles, which may provide important clues into the molecular mechanisms underlying phenotypic parallelisms in East African cichlids.

evolutionary biology↗

bioRxiv2023

A severe bottleneck impacted the genomic structure of egg-eating cichlids

The explosive adaptive radiation of Haplochromine cichlids in Lake Victoria, East Africa, produced 500 endemic species within only 15,000 years. A paedophage or an egg-eater is considered a unique example of trophic adaptation. Many field studies reported that more than 200 cichlids have extinct due to the upsurge of Nile perch, a carnivorous species introduced to the lake in the 1950s. Especially, piscivorous cichlids like paedophages were critically damaged by Nile perch predation. Here, we performed a genome-wide evolutionary study of the paedophages in Lake Victoria to understand their past demographic events and phylogenetic relationships. We discovered evidence of a recent, short-period, and severe bottleneck in a paedophage "matumbi hunter". Interestingly, the signature of a strong bottleneck, as observed in matumbi hunter, was not detected in other species including paedophagus species. In addition, it was revealed that the population size of matumbi hunter started to decline 30 years ago and recover from 20 to 10 years ago, corresponding to the time of both disappearance and resurgence of Lake Victoria Haplochromines were reported. Although population structure analyses showed that matumbi hunter is composed of a unique genetic component, phylogenetic analyses supported its strong monophyly with other paedophagus species. These results suggest that the paedophages originated only once in Lake Victoria followed by the decline of genetic diversity in matumbi hunter. This study succeeded to demonstrate the demographic events triggered by invasive species and associated genomic consequences of the unique trophic group, promoting a holistic understanding of adaptive radiation.

evolutionary biology↗