Age structure of the Japanese treefrog – Dryophytes japonicus (Amphibia, Anura, Hylidae) in the south of the Primorsky krai (Russian Far East)

Abstract

   The article presents the results of age structure studying in a population of the Japanese treefrog (Dryophytes japonicus) by skeletochronology. Animals were caught in the vicinity of Fokino town and Dunay settlement (Primorsky Krai, Russian Federation) in the third decade of July, 2022–2023. Cross sections of a finger’s phalanges were used as a registering structure. To es- timate age, preparations from 59 individuals (12 females and 47 males) were used. The body length of females and males was in a range of 29.40–44.80 mm (on average 38.50 ± 5.69) and 34.16–44.16 mm (on average 38.30 ± 2.36), respectively. The age of females and males varied in a range of 1–4 years (on average 2.7 ± 1.3) and 1–5 years (on average 2.2 ± 1.1), respectively. The modal age in females and males was 4 years (41.6 % of all studied individuals) and 1–2 years (63.8 %), respectively. The average age of males and females did not differ statistically significant- ly. Body length depended on age, in both females (r = 0.82, p < 0.05) and males (r = 0.54, p < 0.05). The expectancy longevity in females and males was 4.41 years (S = 0.744) and 3.76 years (S = 0.693), respectively. The growth of males stops after reaching puberty. Females continue to grow after maturation; that is why the most adult individuals are the largest ones. The growth rate coefficient (k) was higher in males (2.22) than in females (0.89). The authors note that in the south of the Primorsky Krai, D. japonicus is characterized by the minimum age of puberty and life longevity among all studied populations.