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A thermogenic secondary sexual character in male sea lamprey

July 15, 2013

Secondary sexual characters in animals are exaggerated ornaments or weapons for intrasexual competition. Unexpectedly, we found that a male secondary sexual character in sea lamprey (Petromyzon marinus ) is a thermogenic adipose tissue that instantly increases its heat production during sexual encounters. This secondary sexual character, developed in front of the anterior dorsal fin of mature males, is a swollen dorsal ridge known as the ‘rope’ tissue. It contains nerve bundles, multivacuolar adipocytes and interstitial cells packed with small lipid droplets and mitochondria with dense and highly organized cristae. The fatty acid composition of the rope tissue is rich in unsaturated fatty acids. The cytochrome c oxidase activity is high but the ATP concentration is very low in the mitochondria of the rope tissue compared with those of the gill and muscle tissues. The rope tissue temperature immediately rose up to 0.3°C when the male encountered a conspecific. Mature males generated more heat in the rope and muscle tissues when presented with a mature female than when presented with a male (paired t-test, P<0.05). On average, the rope generated 0.027±0.013 W cm-3 more heat than the muscle in 10 min. Transcriptome analyses revealed that genes involved in fat cell differentiation are upregulated whereas those involved in oxidative-phosphorylation-coupled ATP synthesis are downregulated in the rope tissue compared with the gill and muscle tissues. Sexually mature male sea lamprey possess the only known thermogenic secondary sexual character that shows differential heat generation toward individual conspecifics.

Publication Year 2013
Title A thermogenic secondary sexual character in male sea lamprey
DOI 10.1242/jeb.085746
Authors Yu-Wen Chung-Davidson, M. Cody Priess, Chu-Yin Yeh, Cory O. Brant, Nicholas S. Johnson, Ke Li, Kaben G. Nanlohy, Mara B. Bryan, C. Titus Brown, Jongeun Choi, Weiming Li
Publication Type Article
Publication Subtype Journal Article
Series Title Journal of Experimental Biology
Index ID 70047872
Record Source USGS Publications Warehouse
USGS Organization Great Lakes Science Center