Abundance and population profile of Helicostyla daphnis (Stylommatophora: Bradybaenidae), an endemic snail of Cebu, Philippines.
Helicostyla daphnis is a tree snail endemic to Cebu, Philippines. The study aimed to survey and compare the abundance and population profile (by age category) of Helicostyla daphnis in North Cebu and South Cebu in relation to season and other physicochemical factors. Sampling was done twice between April and September 2013. For snail sampling, a standardized direct search equivalent to a two-hour sampling effort in a total of eighteen quadrats in six sites was used. Elevation, air temperature, relative humidity, surface soil pH, and soil exchangeable calcium were measured on each quadrat. Independent t-test and Pearson correlation were used to relate abundance to the physicochemical variables. Snail abundance was significantly higher (p<0.01) during the dry season (dry=783 snails; wet=436). South Cebu had higher total abundance (dry = 477; wet = 284) compared to North Cebu (dry = 306; wet = 152). Adult snails dominated at 87% of total abundance during the dry season and 74% during the wet season. Neonates were present only during the wet season, contributing 5% to total abundance. The presence of eggs in both seasons could mean year-round reproduction; but increased egg abundance and significant presence of neonates imply higher reproductive activity during the wet season. Relative humidity and air temperature were the identified major determinants of abundance as they affect the species’ ability to avoid desiccation stress. The rate of harvesting of H. daphnis cannot also be ruled out as a factor affecting abundance between location.
Effects of Physicochemical Factors and the Local Ecological Knowledge on the Population of Helicostyla daphins (Broderip, 1841) in Borbon and Sogod, Cebu, Philippines.
Helicostyla daphnis (Broderip, 1841), an arboreal edible snail endemic to Cebu, Philippines that was thought to be extinct, was discovered to be still thriving. To formulate strategies for conservation of H. daphnis, a survey of selected physicochemical parameters and local ecological knowledge (LEK) that could affect its population was conducted. On each the three sites, physicochemical parameters were measured and a standardized direct search method for snails was used. LEK was gathered among fifteen snail-hunting experts. Snail total abundance significantly varied across sites in the dry season (p=0.006), being highest at Site 1(private property), and least in at Site 2 (tree plantation). Snails were found to be more abundant in the dry season than the wet (dry=306; wet=152) but significant only at Site 1. Adult snails were the most dominant among the age categories in both the dry and wet seasons. Neonates, comprising 5% of the sampled population, were found only in the wet season. Relative humidity and air temperature were the major determinants of the total abundance. However LEK gathered pointed out that overharvesting and habitat destruction could be major contributors as well. Ficus leucantatoma, Buchananiaar borescens and Artocarpus heterophyllus are the vegetation most prefered by H. daphnis, according to LEK.
