Atividade diária e reprodução do gastrópode Pomacea amazonica (Reeve,1856)

Abstract

Gastropods of the genus Pomacea (Perry, 1810), as well as ecological importance are used for human consumption, are considered the largest freshwater gastropods group. This study investigated the daily activity and substrate selection of gastropod Pomacea amazonica (reeve, 1856), and reproduction and substrate selection for oviposition. The gastropods were collected from May to August of 2014 in the City of Itacoatiara, Amazonas, Brazil. Investigation of daily activity and substrate selection were performed under light and temperature conditions. The animals were observed for 48 hours to record their daily activities and substrate selection was analyzed by four different types of substrates sand, pebbles, water column and smooth surfaces. In reproduction experiment and substrate selection for oviposition graduates couples were kept in cages with different substrates, three types of sandpaper with different roughness, beyond the smooth wall of the bottle itself. P. amazonica activity was significantly different (P<0,05), Compared the time of day and night The highest activity was recorded overnight, about 70% of individuals explored the room during the day and 72% remained immobile. The substrate selection differed significantly compared between periods of day and night (X2 = 22,46; DF = 3; P <0,05). With greater use of the flat substrate during the day and during the night most of the animals went on to use the substrate pebble There was no significant difference (t=-1.1289; DF= 172; P=0.2605) as compared size between males and females of the collected population. As for the size of males and females of each couple, there was significant difference (Z=2.4326; P=0.0150), with fewer males than females. Altogether 29 females laid egg masses and of these, 6 left two bodies of consecutive eggs. The multiple spawns only the females that put two egg masses, no significant difference in the number of eggs (Z=0.8090; P=0.4185). Embryonic development averaged 10.38 ±1.73 mean hatch rate of 89.6% for the first spawn and 65% for the second spawning. Among masses of consecutive eggs of the same female diameter of the eggs did not differ (t=-0.1801; GL=5; P=0,8641). It was observed that the higher the female higher fertility, despite the low coefficient of determination (R2=0.22), regression was significant (F=7,6382; Gl=1; P=0,0099). The substrate selection for oviposition significantly different (X2=172,55; GL=3; P<0,05) with preference animals lay eggs in smooth surface. It can be concluded that P. amazonica nocturnal activities and substrate selection varies with the time of day. Although the size of the sexes is not different in P. amazonica mating females prefer the smaller males. The fecundity of this species is directly related to female size and egg laying mass occurs mostly at night in smooth substrate surface. Embryonic development was relatively short compared to other species of the same genus, and the diameter of the eggs did not differ between consecutive spawns.