NEWS - A new species of dragonfish, Akarotaxis gouldae or banded dragonfish, off the western Antarctic Peninsula by researchers at the Virginia Institute of Marine Science at Gloucester Point, the University of Oregon at Eugene, and the University of Illinois at Urbana-Champaign, highlights the unknown biodiversity and fragile ecosystems of the Antarctic.
%20diverged%20from%20Akarotaxis%20nudiceps%20780,000%20years%20ago.webp "Banded dragonfish (Akarotaxis gouldae) diverged from Akarotaxis nudiceps 780,000 years ago")
A. gouldae was named in honor of the Antarctic Research and Supply Vessel (ARSV) Laurence M. Gould and crew. The larval specimen was collected while trawling for zooplankton and was initially thought to be the closely related Akarotaxis nudiceps hundreds of thousands of years ago.
DNA comparisons with A. nudiceps specimens held in collections at the Virginia Institute of Marine Science, Yale University, and the Muséum national d’Histoire naturelle in Paris showed significant variation in mitochondrial genes that suggested the larval sample was a distinct species.
Andrew Corso of the Virginia Institute of Marine Science and colleagues used the genetic evidence to request examination of adult A. gouldae samples from ichthyology collections around the world. Morphological differences became apparent between the two species when adult samples were compared.
“Two distinct bands on the side of the adult A. gouldae that A. nudiceps does not have. This species has been in collections but has been overlooked. Genetic testing is a valuable tool, but our findings highlight the importance of early life stage morphology and natural history collections,” Corso said.
Genetic testing also revealed clues to evolution using a process called time-calibrated phylogeny. A. gouldae diverged into separate species about 780,000 years ago, during which time much of the Southern Ocean was covered by glaciers.
"This process essentially looks at genetic mutation rates as a guide to the evolutionary history of the species. We hypothesize that the dragonfish population may have been isolated in a trench beneath the glacier. After the glacier retreated, this subpopulation became quite distinct and reproductively incompatible with A. nudiceps," Corso said.
Antarctic dragonfish are poorly understood because they live in the remote Southern Ocean and spend most of their adult lives in deep water. Previous studies have shown that these fish maintain nests in shallower coastal waters and their offspring stay closer to the surface during the larval stage.
Examination of female ovaries suggests a limited reproductive capacity. Analysis of larval sampling data suggests that A. gouldae is restricted to waters around the western Antarctic Peninsula, while A. nudiceps is distributed in waters around the southern continent.
"A. gouldae appears to have the smallest range of all the fish endemic to the Southern Ocean. Its limited range, low reproductive capacity and shallow early life stage make it vulnerable to krill fisheries," Corso said.
The western Antarctic Peninsula is the primary target of the international Antarctic krill fishery managed by the Conservation of Antarctic Marine Living Resources (CCAMLR). Commercial fishing vessels trawl for krill in waters between 0-250 meters (0-800 feet) deep.
“We know very little about the biodiversity in this area, so we are cautious about extracting the resource until we have a better understanding of the impacts on the wider ecosystem,” Corso said.
Akarotaxis was first described as a genus in 1980 by American ichthyologist Hugh Hamilton DeWitt (H. H. DeWitt) and French ichthyologist Jean-Claude Hureau (Hureau). A. nudiceps is the only species and was described by British-Australian zoologist Edgar Ravenswood Waite in 1916 as Bathydraco nudiceps. The type was caught off Queen Mary Land off the Shackleton Ice Shelf by the Australasian Antarctic Expedition.
Original research
Andrew D. Corso, Thomas Desvignes, Jan R. McDowell, Chi-hing Christina Cheng, Ellen E. Biesack, Deborah K. Steinberg & Eric J. Hilton (2024). Akarotaxis gouldae, a new species of Antarctic dragonfish (Notothenioidei: Bathydraconidae) from the western Antarctic Peninsula. Zootaxa 5501 (2): 265-290, DOI:10.11646/zootaxa.5501.2.3
%20diverged%20from%20Akarotaxis%20nudiceps%20780,000%20years%20ago.webp "Banded dragonfish (Akarotaxis gouldae) diverged from Akarotaxis nudiceps 780,000 years ago")
A. gouldae was named in honor of the Antarctic Research and Supply Vessel (ARSV) Laurence M. Gould and crew. The larval specimen was collected while trawling for zooplankton and was initially thought to be the closely related Akarotaxis nudiceps hundreds of thousands of years ago.
DNA comparisons with A. nudiceps specimens held in collections at the Virginia Institute of Marine Science, Yale University, and the Muséum national d’Histoire naturelle in Paris showed significant variation in mitochondrial genes that suggested the larval sample was a distinct species.
Andrew Corso of the Virginia Institute of Marine Science and colleagues used the genetic evidence to request examination of adult A. gouldae samples from ichthyology collections around the world. Morphological differences became apparent between the two species when adult samples were compared.
“Two distinct bands on the side of the adult A. gouldae that A. nudiceps does not have. This species has been in collections but has been overlooked. Genetic testing is a valuable tool, but our findings highlight the importance of early life stage morphology and natural history collections,” Corso said.
Genetic testing also revealed clues to evolution using a process called time-calibrated phylogeny. A. gouldae diverged into separate species about 780,000 years ago, during which time much of the Southern Ocean was covered by glaciers.
"This process essentially looks at genetic mutation rates as a guide to the evolutionary history of the species. We hypothesize that the dragonfish population may have been isolated in a trench beneath the glacier. After the glacier retreated, this subpopulation became quite distinct and reproductively incompatible with A. nudiceps," Corso said.
Antarctic dragonfish are poorly understood because they live in the remote Southern Ocean and spend most of their adult lives in deep water. Previous studies have shown that these fish maintain nests in shallower coastal waters and their offspring stay closer to the surface during the larval stage.
Examination of female ovaries suggests a limited reproductive capacity. Analysis of larval sampling data suggests that A. gouldae is restricted to waters around the western Antarctic Peninsula, while A. nudiceps is distributed in waters around the southern continent.
"A. gouldae appears to have the smallest range of all the fish endemic to the Southern Ocean. Its limited range, low reproductive capacity and shallow early life stage make it vulnerable to krill fisheries," Corso said.
The western Antarctic Peninsula is the primary target of the international Antarctic krill fishery managed by the Conservation of Antarctic Marine Living Resources (CCAMLR). Commercial fishing vessels trawl for krill in waters between 0-250 meters (0-800 feet) deep.
“We know very little about the biodiversity in this area, so we are cautious about extracting the resource until we have a better understanding of the impacts on the wider ecosystem,” Corso said.
Akarotaxis was first described as a genus in 1980 by American ichthyologist Hugh Hamilton DeWitt (H. H. DeWitt) and French ichthyologist Jean-Claude Hureau (Hureau). A. nudiceps is the only species and was described by British-Australian zoologist Edgar Ravenswood Waite in 1916 as Bathydraco nudiceps. The type was caught off Queen Mary Land off the Shackleton Ice Shelf by the Australasian Antarctic Expedition.
Original research
Andrew D. Corso, Thomas Desvignes, Jan R. McDowell, Chi-hing Christina Cheng, Ellen E. Biesack, Deborah K. Steinberg & Eric J. Hilton (2024). Akarotaxis gouldae, a new species of Antarctic dragonfish (Notothenioidei: Bathydraconidae) from the western Antarctic Peninsula. Zootaxa 5501 (2): 265-290, DOI:10.11646/zootaxa.5501.2.3