Metabolic and water loss rates of two cryptic species in the African velvet worm genus Opisthopatus (Onychophora).
Velvet worms (Onychophora) are characterised by a dearth of mechanisms to retain water, yet recently identified cryptic species are located in areas with seemingly different climates. Using flow-through respirometry, this study determined the metabolic, water loss and cuticular water loss rates of two cryptic species of Opisthopatus cinctipes s.l. from locations that differ in their current climate. When controlling for trial temperature and body mass, velvet worms from the drier and warmer site had significantly lower water loss rates than the wetter and cooler site. Mass-corrected metabolic rate and cuticular water loss did not differ significantly between the two sites. The scaling exponent for the relationship between log metabolic rate and log body mass for O. cinctipes s.l. declined with an increase in temperature from 5 to 15 °C. Females in the two cryptic Opisthopatus species had higher metabolic, water loss and cuticular water loss rates than males, which may represent the increased energetic demands of embryonic growth and development in these viviparous taxa.
Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa. cwweldon@zoology.up.ac.za
Christopher W
CW
Weldon
Savel R
SR
Daniels
Susana
S
Clusella-Trullas
Steven L
SL
Chown
D000818:Animals; D001835:Body Weight; D002980:Climate; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D007448:Invertebrates / Q000502:physiology*; D016013:Likelihood Functions; D016014:Linear Models; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology; D012737:Sex Factors; D013019:South Africa; D013045:Species Specificity; D013696:Temperature; D014870:Water Loss, Insensible / Q000502:physiology*