Inter-Research > MEPS > v438 > p195-206  
MEPS
Marine Ecology Progress Series

via Mailchimp

MEPS 438:195-206 (2011)  -  DOI: https://doi.org/10.3354/meps09287

Adaptive radiation at a low taxonomic level: ­divergence in buoyancy of the ecologically similar Antarctic fish Notothenia coriiceps and N. rossii 

Joseph T. Eastman1,*, Esteban Barrera-Oro2,3, Eugenia Moreira

1Department of Biomedical Sciences, Ohio University, Athens, Ohio 45701-2979, USA
2Instituto Antártico Argentino and CONICET, Cerrito 1248, A1010AAZ Buenos Aires, Argentina
3Museo Argentino de Ciencias Naturales ‘Bernardino Rivadavia’, A. Gallardo 470, CI405DJR, Buenos Aires, Argentina

ABSTRACT: We studied the buoyancy of 263 specimens of the sympatric sister species Notothenia coriiceps and N. rossii captured at King George Island. In these species without a swim bladder, we expressed measurements of buoyancy as percentage buoyancy (%B = weight in water/weight in air × 100), with smaller numbers reflecting more buoyant (i.e. less dense) species. Mean %B of N. coriiceps (4.34%) was significantly greater than that of N. rossii (3.82%), reflecting the lower density and more active swimming, migratory, and feeding behavior of N. rossii compared to N. coriiceps. Skeletal weight as a percentage of body weight was also significantly greater in N. coriiceps (2.46%) than N. rossii (1.65%). Paradoxically, the weight of the vertebral column as a percentage of skeletal weight was significantly greater in N. rossii (28.01%) than in N. coriiceps (24.29%); however, this is intelligible in light of the bone anatomy and histology. Our sample encompassed a wide size and age range, and trend lines for scatter plots of %B against standard length were curvilinear for both species, peaking at 140 to 160 mm, a phenomenon not previously seen in studies of notothenioid buoyancy. We conclude that the ontogenetic increase in %B (reduced buoyancy) in fingerlings/young juveniles and the ontogenetic decrease in %B (increased buoyancy) in older juveniles/immature adults reflects disproportionate growth of skeletal and visceral tissues, respectively, and is not causally related to concurrent pelagic–demersal habitat shifts.


KEY WORDS: Notothenioid · Ontogenetic variation · Skeletal anatomy and histology · ­South Shetland Islands


Full text in pdf format 
Cite this article as: Eastman JT, Barrera-Oro E, Moreira E (2011) Adaptive radiation at a low taxonomic level: ­divergence in buoyancy of the ecologically similar Antarctic fish Notothenia coriiceps and N. rossii . Mar Ecol Prog Ser 438:195-206. https://doi.org/10.3354/meps09287

Export citation
Mail this link - Contents Mailing Lists - RSS
Facebook - - linkedIn