Age-dependent changes in plasma biochemistry of yellow-legged gulls (Larus cachinnans)

Alonso-Alvarez, C., 2005. Age-dependent changes in plasma biochemistry of yellow-legged gulls (Larus cachinnans). Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 140(4), pp.512-518.

The study of avian plasma chemistry is providing useful reference values for the management of endangered and game species, supporting veterinarians in their diagnostics, and also bringing to light relevant physiological adaptations during periods of food-shortage. Age is an important source of variability for plasma chemistry. Here I report plasma chemistry of yellow-legged gulls Larus cachinnans from different ages, between post-independence and adulthood, a 5-year interval. Increase in plasma cholesterol concentration and decreases in uric acid, inorganic phosphorus and alkaline phosphatase values were seen. Body mass corrected by body size (i.e. body condition) increased with age, plasma cholesterol being positively correlated in females, but not in males. Moreover, cholesterol was also positively correlated to gonad size in both sexes. Long-term developmental changes in this species, such as gonad development and the acquisition of an optimal body mass for reproduction, could explain these findings. Finally, inorganic phosphorus and alkaline phosphatase, both traditionally related to osteogenesis, were not associated to deferred skull ossification, as originally was suggested in other species.

Changes in plasma biochemistry and body mass during incubation in the yellow-legged gull

Alonso-Alvarez, C., Velando, A., Ferrer, M. & Veira, J. A. Changes in plasma biochemistry and body mass during incubation in the yellow-legged gull. Waterbirds 25, 253–258 (2002).

The “Incubatory Reserves Constancy” hypothesis asserts that incubation could be a departure from breeding stress that allows for the maintenance or recovery of body reserves after laying effort (females) or territory defense (males) in those species with bi-parental incubation such as gulls. The plasma composition and body mass of incubating Yellow-legged Gulls (Larus cachinnans) were analyzed and related to the number of days after egg-laying. Female gulls showed an increase in uric acid and cholesterol levels, whereas males showed only an increase in uric acid values throughout this period. Moreover, females increased while males maintained their body masses. These results could reflect a recovery process after the laying effort supporting the Incubatory Reserves Constancy hypothesis in females. Uric acid and urea levels are positively correlated to body condition in Yellow-legged Gulls, which could be the result of a change in diet composition. This disagrees with recent findings on body composition in incubating gulls and could be related to variations in food availability among populations or years, and could reflect flexibility in the investment devoted by each sex.