An Immunological Analysis of Spanish and French Water Frogs

Antisera to the slowly-migrating albumin of Rana ridibunda and to albumin of Rana perezi (a morphologically, electrophoretically and immunologically homogeneous sample from the Camargues region of southern France) were used in microcomplement fixation experiments to ex- amine serum albumins from 50 individual Rana collected in Spain and France in 1974. The immunological distance from the R. perezi albumin to three samples of R. ridibunda albumin averaged 35, while the distance of 33 individual R. perezi samples averaged 54 from the slowly- migrating R. ridibunda albumin. Serum albumin samples from 13 R. ridibunda x R. perezi hybrids averaged 11 ID units from the albumin of R. perezi, 7 from the albumin of R. ridibunda. Electrophoretically, the albumins of R. lessonae, R. perezi, and the two albumins of R. ridibunda appear to be separated by equally sized steps. Immunological data indicate that parallel but unequal shifts in mobilities have occurred among these four albumins; the immunological differences as- sociated with the different steps vary by a factor of 30. Rana ridibunda x R. perezi individuals examined extend the known range of such hybrids within France to the southeastern tip of the Bay of Biscay, and provide the first Spanish records from this area and from near Zaragoza in the Mediterranean-draining Ebro River Valley.