Abstract
Comparisons across bird species have indicated that those more exposed to parasites and pathogens invest more in immunological defence, as measured by spleen size. We investigated how spleen volume varied with colony size, parasite load and an individual's colony-size history in the cliff swallow, Petrochelidon pyrrhonota, a colonial passerine bird of North America. We used a sample of over 1700 birds that had all died during a period of inclement weather in 1996. We experimentally manipulated ectoparasitism by fumigating nests in some colonies prior to the bad weather. Birds from parasite-free colonies had significantly smaller spleens than those from naturally infested sites; spleen volume did not differ between the sexes and did not vary with age. Mean spleen volume increased significantly with the colony size at a site prior to the bad weather in 1996 and at the site in 1995, both measures of colony size being indices of ectoparasitism at a site. An individual's history of breeding-colony size (defined as the average colony size it had occupied in years prior to 1996) had no association with its spleen size. The results are consistent with parasite-induced splenomegaly whenever birds are exposed to large numbers of ectoparasites. The results do not support spleen size as being a signal of differential life-history investment in immunological defence among individuals and thus run counter to interpretations from recent cross-species comparisons.
Full Text
The Full Text of this article is available as a PDF (156.6 KB).
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Ali N. M., Behnke J. M. Observations on the gross changes in the secondary lymphoid organs of mice infected with Nematospiroides dubius. J Helminthol. 1985 Jun;59(2):167–174. doi: 10.1017/s0022149x00025761. [DOI] [PubMed] [Google Scholar]
- Brown C. R., Komar N., Quick S. B., Sethi R. A., Panella N. A., Brown M. B., Pfeffer M. Arbovirus infection increases with group size. Proc Biol Sci. 2001 Sep 7;268(1478):1833–1840. doi: 10.1098/rspb.2001.1749. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Garside P., Behnke J. M., Rose R. A. The immune response of male DSN hamsters to a primary infection with Ancylostoma ceylanicum. J Helminthol. 1989 Sep;63(3):251–260. doi: 10.1017/s0022149x00009068. [DOI] [PubMed] [Google Scholar]
- John J. L. The avian spleen: a neglected organ. Q Rev Biol. 1994 Sep;69(3):327–351. doi: 10.1086/418649. [DOI] [PubMed] [Google Scholar]
- Molyneux D. H., Cooper J. E., Smith W. J. Studies on the pathology of an avian trypanosome (T. bouffardi) infection in experimentally infected canaries. Parasitology. 1983 Aug;87(Pt 1):49–54. doi: 10.1017/s0031182000052409. [DOI] [PubMed] [Google Scholar]
- Monath T. P., Lazuick J. S., Cropp C. B., Rush W. A., Calisher C. H., Kinney R. M., Trent D. W., Kemp G. E., Bowen G. S., Francy D. B. Recovery of Tonate virus ("Bijou Bridge" strain), a member of the Venezuelan equine encephalomyelitis virus complex, from Cliff Swallow nest bugs (Oeciacus vicarius) and nestling birds in North America. Am J Trop Med Hyg. 1980 Sep;29(5):969–983. doi: 10.4269/ajtmh.1980.29.969. [DOI] [PubMed] [Google Scholar]
- Scott T. W., Bowen G. S., Monath T. P. A field study on the effects of Fort Morgan virus, an arbovirus transmitted by swallow bugs, on the reproductive success of cliff swallows and symbiotic house sparrows in Morgan County, Colorado, 1976. Am J Trop Med Hyg. 1984 Sep;33(5):981–991. doi: 10.4269/ajtmh.1984.33.981. [DOI] [PubMed] [Google Scholar]
- Vincent A. L., Ash L. R. Splenomegaly in jirds (Meriones unguiculatus) infected with Brugia malavi (Nematoda: Filarioidea) and related species. Am J Trop Med Hyg. 1978 May;27(3):514–520. doi: 10.4269/ajtmh.1978.27.514. [DOI] [PubMed] [Google Scholar]
- Watkins R. A., Moshier S. E., O'Dell W. D., Pinter A. J. Splenomegaly and reticulocytosis caused by Babesia microti infections in natural populations of the montane vole, Microtus montanus. J Protozool. 1991 Nov-Dec;38(6):573–576. doi: 10.1111/j.1550-7408.1991.tb06082.x. [DOI] [PubMed] [Google Scholar]
- Willadsen P. Immunity to ticks. Adv Parasitol. 1980;18:293–311. doi: 10.1016/s0065-308x(08)60402-9. [DOI] [PubMed] [Google Scholar]