Age Determination by Skeletochronology of the Japanese Salamander Hynobius kimurae (Amphibia, Urodela)

Abstract

We investigated lines of arrested growth (LAG) of long bone tissues in a total of 157 salamanders of Hynobius kimurae from Tokyo and Kyoto, Japan. The number of LAGs did not differ between femurs, humeri, and toe phalanges. We found that the first LAG is formed after the first overwintering. The number of LAGs varied from 5-14 (x=8.8) in reproductive males and 7-12 (x=9.4) in mature females in the Tokyo population, while in the Kyoto population, males and females had 6-20 (x=9.1) and 7-17 (x=9.9) LAGs, respectively. This suggests that the minimum maturation age in males is five yr in Tokyo and six yr in Kyoto, while females of both populations need at least seven yr. The female-larger sexual size dimorphism, recognized in each population of this species seems to be attributable to a greater growth rate in females after the age of male maturity. Body size growth was better in Kyoto than in Tokyo, with average adult SVL being 3.2-3.6 times and 2.2-2.3 times of SVL of metamorphs, respectively. Adults of the Kyoto population, like metamorphs, are smaller than those of the Tokyo population, and such a difference is considered to be derived not from the differential age at maturity or growth rate but from the size difference at metamorphosis. In both populations, clutch size does not correlate to female age, but older and hence larger females tended to lay larger eggs. This suggests that the female fitness increases with age, not through an increase in the number of offspring per clutch, but through an elevation of survivorship per offspring.

Age Determination by Skeletochronology of Rana nigrovittata, a Frog from Tropical Forest of Thailand

“…For body size difference between sexes, Student's t-test was applied. Logistic Model L=a/(1+e c-bt ), where L is the SVL (mm) at time t (yr), a is the asymptotic size; c is the constant determined by putting 0 to t; and b is the instantaneous growth rate, was used to estimate the growth pattern (Misawa and Matsui, 1999). The significance level was set at 0.05.…”

Age and growth of the Patagonian lizard Phymaturus patagonicus

“…Therefore, body size cannot be used as an accurate and reliable indicator of age in species with indeterminate growth (Wapstra et al, 2001). Skeletochronology, based on the count of growth marks deposited in bone, has become a standard method for individual age estimation in many vertebrates (Leclair and Castanet, 1987;Wake and Castanet, 1995;Castanet et al, 1996;Misawa and Matsui, 1999). When age cannot be determined, body size is sometimes substituted, because they correlate during the main growth phase.…”

Age structure and growth rates of two Korean salamander species (Hynobius yangiandHynobius quelpaertensis) from field populations

“…In H. tokyoensis, both males and females start to breed at 4 years of age, and longevity ranges from 13 to 21 years (Kusano et al 2006). Male and female H. kimurae mature sexually at 5Á6 and 7 years respectively and attain a maximum age of 12 to 20 years (Misawa and Matsui 1999). Unlike Korean Hynobius, in which the females invariably have larger SVLs, sexual dimorphism as measured by SVL is not consistent in the Japanese speciese.…”

“…Life history traits such as the age structure and growth rates of amphibian populations can assist us in understanding basic population dynamics (Stearns 1989;Misawa and Matsui 1999). In Urodela, age at maturity and growth rate are determined by the combined effects of environmental factors including food resources, competition, temperature, latitude and altitude and genetic factors such as developmental constraints (Olgun et al 2001;Cogȃlniceanu and Miaud 2003).…”