Sthefane D'ávila

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.

SPATIAL DISTRIBUTION OF LYMNAEIDAE (MOLLUSCA, BASOMMATOPHORA), INTERMEDIATE HOST OF Fasciola hepatica LINNAEUS, 1758 (TREMATODA, DIGENEA) IN BRAZIL

Snails of the family Lymnaeidae act as intermediate hosts in the biological cycle of Fasciola hepatica, which is a biological agent of fasciolosis, a parasitic disease of medical importance for humans and animals. The present work aimed to update and map the spatial distribution of the intermediate host snails of F. hepatica in Brazil. Data on the distribution of lymnaeids species were compiled from the Collection of Medical Malacology (Fiocruz-CMM, CPqRR), Collection of Malacology (MZUSP), “SpeciesLink” (CRIA) network and through systematic surveys in the literature. Our maps of the distribution of lymnaeids show that Pseudosuccinea columella is the most common species and it is widespread in the South and Southeast with few records in the Midwest, North and Northeast regions. The distribution of the Galba viatrix, G. cubensis and G. truncatula showed a few records in the South and Southeast regions, they were not reported for the Midwest, North and Northeast. In addition, in the South region there are a few records for G. viatrix and one occurrence of Lymnaea rupestris. Our findings resulted in the first map of the spatial distribution of Lymnaeidae species in Brazil which might be useful to better understand the fasciolosis distribution and delineate priority areas for control interventions.

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.

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.

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.

New insights on the morphology of a digenean parasite (Digenea: Brachylaimidae, Brachylaima mazzantii (Travassos, 1927)) using confocal laser scanning microscopy

ABSTRACT Brachylaima mazzantii (Travassos, 1927) is known only from its original description. Until now, no attempt has been made to address the morphology of this species by means of modern microscopy techniques. In the present study, the information generated on the anatomy of B. mazzantii allowed the re-examination of the morphology of this species. The most significant new data is related to the terminal genitalia. The detailed analysis of the reproductive system of this species evidenced the presence of a seminal vesicle external to the cirrus pouch which contains a short unarmed cirrus, and also the presence of a well developed metraterm and gland cells in the genital atrium. The results also revealed some traits concerning other systems, previously unnoticed, including the shape and relative position of the excretory vesicle and the tegument ornamentation. The main advantage of using confocal microscopy to study the morphology of digeneans is the fact that with only one technique it is possible to examine the gross anatomy, cell morphology and surface topography. Confocal tomographies show much more detail than light microscopy images, and allow getting information on cell morphology, usually achieved only by histological techniques, along with some information on tegument ornamentation, usually obtained through scanning electron microscopy. The accumulation of information on the morphology of different digenean species through confocal microscopy will allow future comparative studies, which may ultimately contribute to the better resolution of the systematics of this group.

Influence of substrate humidity on desiccation resistance capacity in Subulina octona (Mollusca, Subulinidae)

The aim of this study was to verify the influence of substrate humidity on desiccation resistance of Subulina octona, continuously exposed, for 48 h, to the temperature of 35 °C. Forty individuals conditioned in 2 plastic boxes, one box containing black earth humidified with 40 ml water and the other one containing dry black earth were used. The retraction of cephalopodal mass inside the shell and the number of dead individuals was evaluated. Snails from dry and humid substrate boxes showed cephalopodal mass retraction of 9.9 cm±2.88 and 2.78 cm±3.17, respectively, after 12 h of exposure; 8.55 cm±1.3 and 6.33 cm±2.91, after 24 h; 11.07 cm±4.19 and 7.27 cm±2.7, after 36 h, 9.12 cm±2.15 and 6.47 cm±2.11, after 48 h. Every individual of dry substrate box died whereas every individual of humid substrate box survived. These results showed that substrate humidity was an influent factor regarding desiccation resistance in S. octona.