Elisabeth Cristina de Almeida Bessa

Influência do substrato sobre o crescimento de Subulina octona (Brugüière) (Mollusca, Subulinidae), sob condições de laboratório

The influence of substrate on growth of Subulina octona (Bruguiere, 1789), reared in sand, clay and humus, was investigated under laboratorial conditions. The individuals reared in humus, showed smaller shell lengths at the ages of 15 days and 30 days, and at the first, second and third reproductive events. There was a progressive decline in growth rate of shell length with time. This fact was observed for the individuals kept in the three kinds of substrate, demonstrating that the indeterminate growth, with a progressive decline in growth after maturity, is the strategy exhibited by S. octona. In this study was also observed that S. octona of different developmental stages fed on substrate and the molluscs reared in humus consumed less food. This is probably due to the fact that humus is more likely to be take as food resource. So that, the snails reared in humus tend to consume more substrate and less ration, obtaining less proteins, carbohydrates and calcium than those snails reared in sand and clay. This low intake of ration might have negative effects over the growth of the snails.The influence of substrate on growth of Subulina octona (Bruguiere, 1789), reared in sand, clay and humus, was investigated under laboratorial conditions. The individuals reared in humus, showed smaller shell lengths at the ages of 15 days and 30 days, and at the first, second and third reproductive events. There was a progressive decline in growth rate of shell length with time. This fact was observed for the individuals kept in the three kinds of substrate, demonstrating that the indeterminate growth, with a progressive decline in growth after maturity, is the strategy exhibited by S. octona. In this study was also observed that S. octona of different developmental stages fed on substrate and the molluscs reared in humus consumed less food. This is probably due to the fact that humus is more likely to be take as food resource. So that, the snails reared in humus tend to consume more substrate and less ration, obtaining less proteins, carbohydrates and calcium than those snails reared in sand and clay. This low intake of ration might have negative effects over the growth of the snails.

The influence of caffeine and thymol on the survival, growth and reproduction of Subulina octona (Brugüière, 1789) (Mollusca, Subulinidae)

Subulina octona is a terrestrial snail which serves as an intermediate host for the parasites. It is also an agricultural pest. The aim of this work was to assess, during 120 days, the effects of caffeine and thymol at 2.5 g/L and 5 g/L on the hatchability, survival after hatching, growth and reproduction of S. octona under the laboratory conditions. A total of 240 eggs, 240 juveniles aged 10-day-old, and 240 aged 30-day-old were tested. The results showed that thymol (at 2.5 g/L and 5 g/L) and caffeine (at 5 g/L) acted as ovicides. In the 10-day-old juveniles, caffeine at 5 g/L caused 25% mortality and at 2.5 g/L it caused 30% mortality. Thymol at 2.5 and 5 g/L caused 20 and 22.5% mortality, respectively. In the 30-day-old juveniles, caffeine at 5 g/L caused 47.5% mortality.

Estudo do crescimento e da reprodução de Bradybaena similaris (Férussac) (Mollusca, Xanthonychidae) em laboratório

Biological aspects of Bradybaena similaris (Ferussac, 1821) were studied, such as: onset of sexual maturity, occurrence of self-fertilization, oviposition, incubation period, eclosion rate and shell length measurement at different stages of development. It was noted that in isolated B. similaris the minimum and maximum time for reaching sexual maturity were 109 and 180 days, respectively. When kept in groups, the minimum time was 78 days. The occurrence of self-fertilization was observed in 18.4% of specimens. The total number of eggs per oviposition varied from one to 38 (average: 3,5 ± 7,15), the total number of eggs per mollusc varied from one to 39 (average: 7,0 ± 10,21) and the total number of oviposition per mollusc varied form one to six (averege: 2,0 ± 1,27). Thirty ovipositions (894 eggs) were followed and the minimum eclosion time of the young was 14 days, the maximum eclosion time was 35 days and the average 23,69 days. The eclosion average percent was 81,22. As to the shell length in different growth stages, it was observed that in B. similaris the length of the shell was similar until 30 days for age. After this period isolated specimens acquired a greater growth rhythm when compared to that of grouped specimens. The maximum shell length of isolated specimens was 17,4 mm whereas grouped specimens reached 14,5 mm. In this specie, individuals that were kept grouped became sexually mature earlier than isolated ones. Individuals kept isolated reach larger length of shell. In the moment of the sexual maturity, the length of the shell in the individuals tha were kept isolated was smaller than the grouped.

Influência de diferentes substratos e umidade sobre o crescimento e o número de ovos produzidos por Subulina octona (Brugüière) (Mollusca, Subulinidae), sob condições de laboratório

O objetivo deste estudo foi verificar a influencia da umidade do substrato sobre o crescimento e a reproducao de Subulina octona (Bruguiere, 1789), criada em areia, argila e terra vegetal. Sobre o grupo experimental, constituido por tres grupos tratados (substrato umedecido com 10ml de agua a intervalos de cinco dias) e tres grupos controle (substrato umedecido com 10ml de agua a intervalos de um dia), foram realizadas observacoes a cerca do crescimento, expresso pelo comprimento da concha; do numero de ovos produzidos e do comprimento da concha no primeiro evento reprodutivo. O grupo tratamento e o grupo controle constituiram-se de 210 individuos recem-eclodidos, distribuidos aleatoriamente em caixas diferenciais em funcao do substrato utilizado: caixa 1 e controle 1, com areia; caixa 2 e controle 2, com argila; caixa 3 e controle 3, com terra vegetal. Cada caixa continha 35 individuos. Os individuos do grupo controle (substrato umedecido a intervalos de um dia) apresentaram um ritmo de crescimento mais rapido. A umidade do substrato foi um fator de maior influencia sobre a reproducao dos individuos criados em caixas com areia e argila. Houve diferenca significativa entre as medias do comprimento da concha e do numero de ovos produzidos, no primeiro evento reprodutivo dos individuos da caixa 1 (areia) e do grupo controle 1. Os individuos da caixa 2 (argila) apresentaram menor comprimento de concha no primeiro evento reprodutivo do que os individuos do grupo controle 2. Os gastropodes terrestres perdem agua pelo tegumento e, do mesmo modo, se reidratam pelo tegumento, atraves da chamada reidratacao por contato. Neste contexto, a umidade do substrato influencia a manutencao da homeostase por estes organismos e consequentemente seu crescimento e reproducao.

Ciclo de vida de Dysopeas muibum (Mollusca, Subulinidae) em laboratório: efeito do isolamento sobre padrões biológicos e conquiliomorfométricos

The knowledge of biological and morphological characteristics of terrestrial molluscs is important for the development of pest control measures and strategies for the conservation of species. This study aimed to characterize the patterns of biology and conquiliomorphometrics of Dysopeas muibum Marcus & Marcus, 1968 and check the effect of isolation on its life cycle and morphometric of the shell, under laboratory conditions. We conducted monitoring growth of the shell, release of puppies and mortality of 80 molluscs, of which 40 were kept isolated and 40 grouped (10 molluscs per group) in natural conditions of temperature, relative humidity and photoperiod, from birth to 180 days of life, when the measures of the shell were taken. The molluscs were reared in plastic terrariums sealed with cotton fabric and elastic, containing plant soil sterile, and fed with food to broilers enriched with calcium carbonate. It was found that the species has small and elongated shell, and is able to reproduce by self-fertilization. It has indeterminate growth, iteroparity, low mortality before and after sexual maturity and fecundity increases with body size. The isolation acted on fertility, although it has not influenced the growth, reach sexual maturity, growth-reproduction relation, mortality and conquiliomorfometrics.

Comportamento agregativo em Subulina octona (Brugüière) (Mollusca, Subulinidae)

The current study aimed to verify the existence of aggregative behavior in Subulina octona (Bruguiere, 1789) and to obtain behavioral evidence of chemical mediation of this behavior. We used 150 adult animals allocated in 15 boxes with humus (10 animals per box). In each box we placed four identified plastic disks in an equidistant position. These disks worked as shelters for the animals. In experiment I, 10 animals were put in the middle of each box. After 24, 48, 96, 120, 144, and 168 hours we observed the number of formed aggregations, as well as the position of the aggregates (in each shelter), the number of individual per aggregation and the number of isolated individuals. In order to test the hypothesis of conditioning of disks by chemicals compounds, the experiment II was carried out. All the individuals were transferred to other boxes with humus, three new disks and the disk containing the larger aggregate after the 168 hours of the experiment I (denominated conditioned disk). We verified, after 24 and 48 hours, the number of individuals below the conditioned disk. In experiment I, aggregations were observed in every used box and in every time intervals. In all boxes, there was a significant increase in the number of individuals per aggregation and a reduction in the number of isolated individuals until the end of the experiment (ANOVA, p < 0.005). In experiment II, after 24 hours, six from 15 boxes presented aggregations under the conditioned disk, and after 48 hours, seven boxes presented aggregations under conditioned disk. These were the aggregations with a larger quantity of individuals, which suggests the conditioning of the used disks by some factor, possibly a chemical compound.

Phytochemical and molluscicidal activity of Mikania glomerata Sprengel (Asteraceae) in different lifestages of Subulina octona (Mollusca, Subulinidade)

The objective of this work was to study the molluscicidal activity of aqueous extract of Mikania glomerata on the land snail Subulina octona and to assess the changes caused on the snails fecundity, growth, hatchability and the offspring produced after exposure. Eggs, newly hatched and 30 day old snails were exposed to the sublethal concentration of M. glomerata extract for 24 and 48 h and the observations were made for 120 days. The presence of tannins, flavonoids and saponins were shown by phytochemical tests. The extract reduced significantly the hatchability and the survival of the offspring hatched from the exposed eggs. The eggs exposed for 48 h presented lower hatchability rates. There was a reduction on survival and growth of newly hatched and 30-days old snails exposed to the extract. These results indicated that the aqueous extract of M. glomerata could be applied as an alternative molluscicide for the control of this snail species efficiently.

Seasonal changes of energy reserves in Bulimulus tenuissimus (d'Orbigny, 1835) (Mollusca, Bulimulidae)

The objective of this study was to evaluate the variation of energy substrates in different seasons in Bulimulus tenuissimus. For this evaluation, substrates were collected from the digestive and albumen glands and foot tissues, which were processed to obtain the concentrations of glucose and galactose. There was seasonal variation in energy reserves in both the digestive gland and the foot of Bulimulus tenuissimus, with a tendency to accumulation from spring to winter. There was greater use of energetic reserves in the spring and summer, being the glycogen stored in the digestive gland the first source consumed. In addition, mobilization of reserves of glycogen in the muscle in summer was observed. The reduction of glycogen coincides with the reproductive cycle of the species, and the expenses generated for the processes of mating and gametogenesis was the cause of this reduction. The concentration of galactogen also varied according to the reproductive period. It was suggested that variations in temperature and photoperiod that occur during the year would act as regulatory mechanisms of energy metabolism of B. tenuissimus.

The influence of thymol+DMSO on survival, growth and reproduction of Bradybaena similaris (Mollusca: Bradybaenidae)

Bradybaena similaris (Ferussac, 1821), commonly known as the Asian trampsnail, is a terrestrial snail native to Asia, introduced in other regions of the world. In Brazil, populations of this land snail are distributed from the state of Amapa in the North to Rio Grande do Sul in the South. This species acts as an intermediate host for parasites and is a difficult-to-control agricultural pest as well, causing great losses to crops and ornamental plant cultivation. This land snail is easily reared in the laboratory and has been successfully used as a biological model in studies that aim at verifying molluscicidal effects of plant extracts. Several studies have demonstrated that B. similaris, like many other species of land and freshwater snails, is physiologically adapted to survival over transitory unfavorable environmental conditions. Moreover, this species seems to have a life history strategy characterized by a short life span and a maximal opportunistic reproductive effort during transient favorable periods. Such biological features may potentially lead to the inefficacy of control attempts and, simultaneously, make this species able to repopulate sites previously treated with biocides. For this reason, studies that aim at verifying the effect of molluscicides on the reproduction, growth and survival of molluscs are greatly required. Molluscicides of plant origin may represent a safe and effective way of controlling these animals. Thymol is a substance of plant origin which has bactericidal, fungicidal and anti-inflammatory properties and has been presented as a promissory biocide of mollusc species. The aim of this work was to assess the molluscicidal property of thymol in combination with DMSO against eggs and adults of B. similaris. During 120 days, we evaluated the effect of thymol+DMSO at different concentrations (2.5 g/L and 5 g/L) on the hatching success, hatchling survival, growth and reproduction of B. similaris under laboratory conditions. We tested thymol+DMSO on 160 eggs, 160 10-day-old and 160 30-day-old juveniles. The results showed that thymol+DMSO (5 g/L and 2.5 g/L) affected hatching success, acting as an ovicide. The tests with 10-day-old juveniles showed that thymol+DMSO at 2.5 g/L and 5 g/L caused 90 and 100% of mortality, respectively. For the 30-day-old juveniles, thymol+DMSO caused 87.5% of mortality at 5 g/L, and 75% at 2.5 g/L. With regard to growth, the results were not significant. The 10-day-old individuals treated with thymol+DMSO showed only one reproductive event during the 120 days of the experiment. Thymol+DMSO showed molluscicidal and residual activity, which makes evident its potential for controlling snails, and consequently, snail-borne diseases.

Efeito do fotoperíodo sobre o ciclo de vida e a morfometria da concha de Dysopeas muibum (Mollusca, Subulinidae) em condições de laboratório

This study aimed to evaluate the effect of photoperiod on the life cycle and shell morphology of Dysopeas muibum Marcus & Marcus, 1968 under laboratory conditions. To this end, we conducted monitoring growth of the shell, the release of puppies and mortality of 40 specimens undergo natural conditions of temperature, relative humidity and photoperiod, and 80 undergo controlled conditions (40 with long days, and 40 with short days), from birth to 180 days, when the measures of the shell were taken. It was found that the photoperiod had no effect on the indeterminate growth, the relationship between reproduction and growth, iteroparidade and low mortality before and after sexual maturity. The controlled conditions of temperature, relative humidity and photoperiod favored growth, conchiliomorphometrics values higher and fast reach sexual maturity, while the decrease in day length favored fecundity.