Octopus insularis: descrição de desova e paralarvas recém-eclodidas, cultivo de sub-adultos em diferentes sistemas e aspectos da fisiologia digestória de animais selvagens e cultivados

Abstract

From cephalops, octopuses are considered economically interesting species for aquaculture. Their fishery has been steadily decreasing since 1990’s, which has led to increase in the demand for octopuses. In 2006 researchers have found in the Brazilian northeast coast a kind of octopus initially identified as Octopus vulgaris, and later, in 2008, identified as Octopus insularis. In chapter 01 of this thesis was describe newly-hatched paralarvae of Octopus insularis and defined its first life habit as planktonic with a positive phototaxis and no lecitotrófica phase. It has been determined that the time between the onset of spawning and hatching is approximately 25 days. It was found that the O. insularis lay their eggs in clusters with an average density of 390eggs/cm and no egg size variance was observed due to variation in female’s size. For chapter 02 was developed a laboratory system with closed recirculating water for food preference and grow out experiments with O. insularis sub-adults. For the first test, the double choice food, acrylics “Y” were used. The foods tested were crab (Callinectes bocourti) gastropod (Stramonita brasiliensis) and sardines (Sardinella spp), all tested paired. We observed the capture of all foods, however there was a clear preference of crab and fish across the gastropod. Even observing a higher crab frequency capture, no significant difference was observed between the frequency of catching crab and fish. Later we tested the grow out of O. insularis sub-adults at 23 and 28°C using crab as food. For all ongrowing indices used, grow out at 28°C show higher values than at 23°C. A total weight gain (ΔW) of 309.8g, a relative weight gain (GR) of 100.9%, an absolute growth rate (AGR) of 9.4g/day and a specific growth rate (SGR) of 2.1%BW/day were registered for 28°C test. Even with a higher food intake by the 28°C cultured group, there was no difference between the feed conversion rate (FCA) between groups cultured at 23 and 28°C. It was also accomplished the O. insularis sub-adults grow out in floating cages being offered different proportions of crabs and fish as food. It was observed a higher growth by the animals feed exclusively by crabs, and this test shown an AGR of 13.6g/day, and a SGR of 1.4%BW/day. There were no significant difference in the growth rates of the groups fed only fish and fed 50% fish and 50% crab. In chapter 03 were analyzed some of the digestive enzymes of the digestive tract of wild and cultured O. insularis species. For the total alkaline protease activity was observed greater activity in the posterior salivary gland (GSP) in wild individuals. For total acidic proteolytic activity no significant difference between the wild and cultured group was observed. Significant activity was only observed in the digestive gland (GD). Trypsin activity was observed in GD and GSP for both groups, wild and cultured, although cultured xi group have shown much lower activity them wild group. For chymotrypsin activity, activities were observed in the intestine (INTEST) and GSP for both analyzed groups, however wild group presented higher values of enzyme activity. Analyzing the aminopeptidases activity for 9 different amino acids, it was found a greater activity, for most of analyzed amino acids, in wild group than cultured group. There is also a strong relationship between these aminopeptidases that occur in the wild group GSP and muscle composition of animals from this same group. For amylase activity, was observed a high activity in various organ of the digestive tract, specifically the anterior salivary gland (GSA), GSP, cecum (CEC), GD and INTEST, and again wild group shown a higher activity than culture group.