Life table estimates of the invasive slug Deroceras laeve (O. F Müller, 1774) occurring in Darjeeling Himalayas, India

Abstract

The life history traits of the invasive slug, Deroceras laeve, occurring in the Darjeeling Himalayas, India, were estimated under laboratory conditions using the hatchlings from eggs of field-collected D. laeve. The growth pattern of D. laeve was found to be logarithmic, rapidly increased initially, and reached a stable condition till death. The maximum life span of D. laeve was 138 ± 3.48 days, with slightly higher mortality during the juvenile period, which decreased gradually at older ages. The pre-reproductive period of 37 ± 2.7 days, reproductive period of 100.8 ± 5.2 days, and 5.4 ± 1.72 days post-reproductive period of D. laeve were observed. D. laeve attained sexual maturity during 38 ± 2.7 days, and the age-specific fecundity increased with increasing age. The hatchability of the eggs was observed to be > 75% following the incubation period of 14.25 ± 0.49 days. The net reproductive value (R₀), generation time (T_c), and finite rate of increase (λ) were 40.01, 12.48 weeks, and 1.455, respectively. Apparently, the earlier sexual maturity, high net reproductive rate, and shorter generation time of D. laeve are indicative of its invasive nature as well as prospective range expansion in similar geographic locations.