Marine invertebrates are well known to accumulate trace metals from seawater, plankton, sea plants, and sediments. To test the usefulness of such organisms as a bio-indicator of environmental conditions, we have determined levels of trace elements in tissue of twelve species of marine invertebrates by photon and neutron activation analysis. Relatively higher concentration of elements were observed for Ni and Sn in mid-gut gland, for Cu and Zn in oyster tissues, for Se in swimming crabs, for Cu, Fe, and Se in gills of swimming crabs. Our results indicate that mid-gut gland of ear-shell will be useful as the indicator of environmental conditions.
Authors:Felipe Fonseca, Elisabete De Nadai Fernandes, Vanessa Rodrigues, Isabel de Oliveira Cavalca, Leandro Camilli, Claudiney Bardini, and Elvis De França
The quality of environmental studies depends on the utilization of adequate sampling protocol and analytical method for obtaining
reliable results and minimizing analytical uncertainties. In order to demonstrate the applicability of INAA for determining
chemical element composition of invertebrates, this work evaluated sample representativeness in terms of subsampling and sample
size. Br, Co, Fe, K, Na, Sc and Zn could be determined in very small samples despite increasing of analytical uncertainties.
Special attention should be directed to invertebrate species with small structures because of the high chemical variation
observed among different sample sizes tested.
Authors:R. de S. Rezende, A. O. Medeiros, J. A. dos Santos Dahora, A. M. Tonin, J. F. Gonçalves Junior, and Y. Moretto
The invertebrate biodiversity of subtropical streams depends on the seasonal input of organic matter, as much as the leaf decomposition process on stream system. However, one of the challenges in determining the importance of invertebrates for leaf breakdown in subtropical streams is the low taxonomic resolution applied in most studies. To overcome this limitation, here we used litter bags with senescent leaves to evaluate the impact of different taxonomic resolutions of trophic group classification to assess the seasonal importance of invertebrate community for leaf litter breakdown in a subtropical stream (Atlantic Forest in western of Paraná state, Brazil). Litterfall was quarterly measured over a year. The leaf litter accumulated in an interval of 30 days was retrieved, weighed, and used for the leaf breakdown experiments (by litter bags). We found a lower importance of invertebrate community richness and density (shredders and scrapers) in leaf breakdown process irrespective of the taxonomic resolution (family or genus level used). Hyphomycetes biomass and fungi sporulation also did not present changes among sample times, and consecutively, importance for leaf breakdown. However, the richness and density of Chironomidae taxa respond differently depending on the taxonomic resolution used. Low litter breakdown may be explained by the increase of consumption of microorganisms, due to high density of Chironomidae scrapers evaluated at the genus level. Moreover, temperature is the main factor responsible for breakdown over the year, in a positive way. Therefore, our results indicated the family level as the taxonomic resolution sufficient to assess the role of shredders and scrapers in the leaf litter breakdown process of this subtropical stream system.
We studied a benthic invertebrate assemblage of a stream that passes through pristine, rural, suburban and urban areas of a municipality located in southeastern Brazil to investigate a possible relationship between this assemblage structure and urbanization. The environmental variables and fauna structure were analyzed in a spatial and temporal scale, sampling the four sites in a dry and wet season. We found a clear spatial pattern, with higher similarity between sites from rural and suburban area that presented intermediate environmental characteristics. The pristine site showed in both seasons the lowest values of alkalinity and fecal coliform. On the other hand, the site located in the urban area showed the lowest concentration of dissolved oxygen and higher of suspended solids, ammonia and fecal coliform. The extreme values of these three variables occurred in the wet season, probably related to the high rainfall values. The benthic invertebrate fauna structure followed the same longitudinal and seasonal pattern found for the environmental variables. The site in urban area showed the lowest richness, diversity and evenness, with a dominance of two groups resistant to adverse environmental conditions (Oligochaeta and Orthocladiinae) and absence of more sensitive groups (Coleoptera, Ephemeroptera and Trichoptera). The increase drag of the substrate and associated invertebrates can be responsible for the lower abundance and richness observed in the wet season. The environmental variables that best defined the differentiation between sites (dissolved oxygen, organic suspended solids and fecal coliform) related directly to urbanization effects, like dump effluents and removal of riparian vegetation.
Authors:E. Ivashkin, Marina Khabarova, and Elena Voronezhskaya
Serotonin (5.HT) is known to be functionally active during early development in both vertebrates and invertebrates. However, the presence of 5-HT and its synthesis and transport system has not yet been demonstrated in bivalve early development. The presence of 5-HT was immunochemically demonstrated at the cleavage stage of bivalve Mytilus trossulus. 5-HT level dramatically increased within all embryonic cells after incubation with 5-HTP but not after incubation with tryptophan and 5-HT. The first 5-HT uptake by specific transporter was detected at 13 hpf blastula stage only and it was restricted to one distinct cell.
Authors:Elizabeth C. Cropper, C. G. Evans, J. Jing, A. Klein, A. Proekt, A. Romero, and S. C. Rosen
Although feeding in Aplysia is mediated by a central pattern generator (CPG), the activity of this CPG is modified by afferent input. To determine how afferent activity produces the widespread changes in motor programs that are necessary if behavior is to be modified, we have studied two classes of feeding sensory neurons. We have shown that afferent-induced changes in activity are widespread because sensory neurons make a number of synaptic connections. For example, sensory neurons make monosynaptic excitatory connections with feeding motor neurons. Sensori-motor transmission is, however, regulated so that changes in the periphery do not disrupt ongoing activity. This results from the fact that sensory neurons are also electrically coupled to feeding interneurons. During motor programs sensory neurons are, therefore, rhythmically depolarized via central input. These changes in membrane potential profoundly affect sensori-motor transmission. For example, changes in membrane potential alter spike propagation in sensory neurons so that spikes are only actively transmitted to particular output regions when it is behaviorally appropriate. To summarize, afferent activity alters motor output because sensory neurons make direct contact with motor neurons. Sensori-motor transmission is, however, centrally regulated so that changes in the periphery alter motor programs in a phase-dependent manner.
Dispersal allows species to immigrate and emigrate to and from habitat patches and is an important factor in determining community structure. The influence of species dispersal in a metacommunity is poorly understood, particularly its effect at the local community level. We aimed to address this deficiency by evaluating the potential influence of dispersal on local community structure in a rock pool metacommunity. Short term dispersal was quantified over an 11 day period by intercepting propagules dispersing via overflowing pool water and via wind. The composition of dispersing organisms was compared to natural local communities in the rock pools surveyed annually on 11 occasions. On average, the composition and abundance of dispersing species was approximately 54.1 ± 9.3% (mean ± SD) similar to the established pool community. Some species were more abundant among dispersers than they were in the pool community. This may be attributed to several factors including a variation in tolerance to environmental conditions, dispersal capacity, and local scale species interactions (predation and competition). In general, we found considerable similarity between short term dispersal and long term local community structure across a metacommunity. Differences in abundance patterns between the resident rock pool community and the dispersal assemblage emphasize that dispersal, a regional process, must interact with local factors in structuring communities.