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The suborder Notothenioidae is comprised of Antarctic fishes, several of which have lost their ability to rapidly upregulate heat shock proteins in response to thermal stress, instead adopting a pattern of expression resembling constitutive genes. Given the cold-denaturing effect that sub-zero waters have on proteins, evolution in the Southern Ocean has likely selected for increased expression of molecular chaperones. These selective pressures may have also enabled retention of gene duplicates, bolstering quantitative output of cytosolic heat shock proteins (HSPs). Given that newly duplicated genes are under more relaxed selection, it is plausible that gene duplication enabled altered regulation of such highly conserved genes. To test for evidence of gene duplication, copy number of various isoforms within major heat shock gene families were characterized via qPCR and compared between the Antarctic notothen, Trematomus bernacchii, which lost the inducible heat shock response, and the non-Antarctic notothen, Notothenia angustata, which maintains an inducible heat shock response. The results indicate duplication of isoforms within the hsp70 and hsp40 super families have occurred in the genome of T. bernacchii. The findings suggest gene duplications may have been critical in maintaining protein folding efficiency in the sub-zero waters and provided an evolutionary mechanism of alternative regulation of these conserved gene families.
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The Scaly Notothen Trematomus loennbergii a new host, and the Ross Sea, Antarctica, a new locality for dermal X‑cell parasites Notoxcellia spp.
Abstract Pathogens affecting Antarctic fishes remain mostly unknown and are largely limited to the description of macroparasites such as leeches and endoparasitic worms. Fish, however, occupy a crucial role in the functioning of the Antarctic ecosystem and deterioration of their health can alter the entire Antarctic food chain. In recent years, several studies have identified novel viruses and unicellular parasites affecting the health of notothenioid fishes. Among those, the unicellular parasitic family Xcellidae has received attention following the discovery of an unprecedented disease outbreak in a fjord on the Western Antarctic Peninsula. This pathological situation was caused by a novel X-cell genusNotoxcellia. Soon thereafter, an additional X-cell genus,Cryoxcellia, was described infecting the Bald NotothenTrematomus borchgrevinkiin the Ross Sea. These studies raised awareness and drew observers’ and researchers’ attention to pathologies in Antarctic fishes. Here, we report that during a 2023 Ross Sea shelf survey, a specimen of the Scaly NotothenTrematomus loennbergiidisplaying skin lesions reminiscent ofNotoxcelliainfection had been ingested by an Antarctic ToothfishDissostichus mawsoniand was recovered from its stomach. Molecular analyses confirmed the presence ofNotoxcelliasp. X-cell parasites in the fish’s lesions. This new case of X-cell disease suggests thatNotoxcelliaspp. may have a circumpolar distribution and stresses the need for monitoring Antarctic fish health similar to surveillance protocols for Antarctic birds and marine mammals.
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- Award ID(s):
- 2232891
- PAR ID:
- 10580970
- Publisher / Repository:
- Springer Science + Business Media
- Date Published:
- Journal Name:
- Polar Biology
- Volume:
- 48
- Issue:
- 2
- ISSN:
- 0722-4060
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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