Researchers using a modified microscope have captured the first high-resolution images inside living Antarctic spiny plunderfish cells at near-freezing temperatures. Scientists at the British Antarctic Survey and the University of Cambridge found the cells packed with dense, elongated mitochondria and enlarged acidic waste-processing bodies to combat cold-induced protein misfolding.
Antarctic fish spend their entire lives in water hovering around 0°C. This environment pushes cellular machinery to absolute limits. Chemical reactions slow down. Proteins struggle to fold into their proper working shapes.
To understand how these animals survive, researchers cultured cells from the Antarctic spiny plunderfish, scientifically known as Harpagifer antarcticus. They examined them using a specially modified microscope designed to operate close to freezing without warming the cells.
Culturing Plunderfish Skin, Fin, and Embryo Cells at 2°C
The imaging work was led by Francesca van Tartwijk, a cell biologist at the British Antarctic Survey and the University of Cambridge. Working alongside colleagues Anne-Pia Marty and Amir Rahmani, the team grew cells from small pieces of plunderfish skin and fin at 2°C. They also established cultures from embryos and ovarian tissue, creating a novel experimental system for studying Antarctic fish at the cellular level.
Unusual Hyperfused Mitochondrial Networks in Harpagifer antarcticus
When the researchers looked inside the plunderfish skin cells, they found significantly more mitochondrial material compared to cells from the shanny, a temperate fish species found around Britain called Lipophrys pholis. Many of these mitochondria were unusually stretched and interconnected, forming a network the researchers describe as “hyperfused.” According to the study authors, this structural adaptation may compensate for the heavy energetic demands of extreme cold or help protect mitochondrial function.
Autolysosomes and the Burden of Slower Cellular Digestion
The microscopic analysis also uncovered unusually large acidic bodies clustered around the cell nucleus. These structures are involved in cellular digestion, and the largest among them may be autolysosomes, which help dismantle damaged components. Researchers suggest that the enlargement of these waste-processing structures stems from slower cellular digestion in the cold, an increased burden of misfolded proteins, or a combination of both factors.
Protein Synthesis Struggles and Molecular Hurdles at 3°C
Earlier work by the research group highlighted the specific molecular hurdles posed by cold water. A 2024 comparison between the Antarctic spiny plunderfish and the temperate shanny revealed that tissue protein synthesis at 3°C was significantly lower in the Antarctic species. Cold temperatures disrupt both the molecular processes required to manufacture proteins and the delicate folding of amino acid chains.
A misfolded protein is useless at best, but can be really harmful, so these cold-adapted cells need ways of dealing with them.
Francesca van Tartwijk, cell biologist at the British Antarctic Survey and the University of Cambridge
Surprising Speed Similarities Between Antarctic and Temperate Fish Mitochondria
Despite extreme temperatures slowing down certain biochemical pathways, the cell interiors were not entirely sluggish. Mitochondria inside the Antarctic fish cells moved at roughly the same speeds as those observed in the temperate shanny cells. While statistical analysis showed the plunderfish mitochondria were slightly faster, the effect was so minimal that authors note it may carry little biological significance.
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