Seasonal Changes in Body Shape and Mass in the Salamander, Hynobius nigrescens

Abstract

Male and female Hynobius nigrescens show pronounced changes in body shape associated with aquatic reproduction. Soon after entering the breeding pond there is a large increase in body mass, head width, and tail height in males, caused by changes in connective tissue under the skin and by storage of seminal fluid in the vasa deferentia. These features decline gradually in postbreeding males prior to leaving the pond. Females show little seasonal variation in head width or tail height, but exhibit a large increase in body mass after ovulation. This is the result of absorption of water during the formation of egg sacs. Mazzi and Vellano (1987) stated that some salamanders were characterized by an increase in body mass and tail height during the aquatic phase. This phenomenon is well known in sal- amandrids. For example, in Taricha granulosa breeding males have the greatest body mass and tail height (Specker and Moore, 1980). In Tri- turus spp. the male develops a tall, crenulated crest and pronounced tail fin during the breed- ing season (Halliday, 1977). In Notophthalmus