Farmed in Okinawa for their nutritional value, these large meso-predators have had their entire genome sequenced, yielding unexpected findings. Because Unexpected hormone-related gene activity is found in the early larval stage of the Malabar grouper, these genes are activated twice during larval development—once in the early larval stage and again during metamorphosis. This early activation has not been observed in other fish species, making the grouper’s case exceptional.
| Date | September 10, 2024 |
| Source | Okinawa Institute of Science and Technology (OIST) Graduate University |
| Summary | Researchers have uncovered distinct gene activation patterns during Malabar grouper larval development, identifying a surprising early peak in thyroid and corticoid gene activation. |
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Why unexpected hormone-related gene activity is found in the early larval stage of the Malabar grouper
Researchers from the Marine Climate Change Unit and Marine Eco-Evo-Devo Unit at the Okinawa Institute of Science and Technology (OIST) have uncovered unique gene activation patterns during Malabar grouper larval development. Their study, published in eLife, is the first to demonstrate that thyroid and corticoid genes are activated twice during larval development—once in the early larval stage and again during metamorphosis. This early activation is unprecedented in any fish species, making the Malabar grouper case exceptional.
As meso-predators, groupers play a vital role in maintaining the health and balance of marine ecosystems. The Malabar grouper (Epinephelus malabaricus), known as Yaito-hata in Japan, can grow up to two meters long. However, overexploitation due to their popularity and high market value has endangered many grouper species. To address this threat and meet demand, grouper aquaculture farms have been established in Okinawa and other regions.
RNA Analysis Unveils Unusual Hormone Activation
The genome is the complete set of genetic material in an organism, and scientists can study how it functions through transcriptomic analysis, which reveals which genes are activated at specific times. The researchers examined the gene expression of thyroid and corticoid hormones during the grouper’s larval development, including the critical phase of metamorphosis.
Malabar grouper larvae drift in the open ocean for around 60 days before returning to coastal areas. During this period, they undergo a dramatic, hormone-driven metamorphosis, marked by spine regression and the appearance of adult-like pigmentation.
Genomic analysis clearly shows heightened thyroid and corticoid gene activation during metamorphosis, coinciding with the emergence of adult pigmentation and the loss of spines on the larvae’s dorsal and pectoral fins. What’s particularly interesting is the surge in these genes early in the larval stage, which we haven’t observed in other fish species.
Dr. Natacha Roux, a researcher also measured thyroid hormone and corticoid levels in the larvae and saw a spike at the beginning of development, confirming the genomic results. While the cause of this early activation is unclear, they suspect it may be linked to the development of larval spines, aiding buoyancy and deterring predators.
FAQ on unexpected hormone-related gene activity is found in the early larval stage of the Malabar grouper
1. What is a Malabar grouper?
The Malabar grouper (Epinephelus malabaricus), also known as Yaito-hata in Japan, is a large meso-predatory fish found in the Indo-Pacific region. It can grow up to 2 meters in length and plays a crucial role in maintaining marine ecosystem balance by controlling prey populations.
2. Where are Malabar groupers found?
They inhabit tropical and subtropical waters, primarily in coral reefs and coastal areas. They are widely distributed across the Indo-Pacific, including regions like Okinawa, Southeast Asia, and northern Australia.