مجله بین المللی زیست شناسی آبزیان
سال:1397 | دوره:6 | شماره:2 |تعداد مقالات:8

The Neotropical hermit crabs’ behaviour is rarely studied, although it is an important toolfor the conservation of these invertebrates. In this context, the present study aimed to describe thehermit crab ethogram on its behaviour in the choice and dispute by shells.60 specimens of hermitcrabs were collected that were occupying mollusc shells Cerithium atratum, in sandstone reefs. Inthe laboratory, 30 hermit crabs were removed from their host shells by heating, the rest remained intheir shells. The specimens were submitted to five experimental tests: (I) behaviour, (II) shell dispute, (III) shell preference, (IV) specimen behaviour with and without shell, and (V) shell contentionbetween individuals with and without shell. The ethogram was built and evaluated by the Ad Libitumtype of observational sampling methods and by the scanning type, for 30 uninterrupted minutes, records every two minutes, in total 15 observations per each observer. There were eight behaviouralacts divided into 4 categories: immobility, interaction between specimen, environment exploration, and shell occupation. The most frequent behaviour was "walking", for both hermit crabs (54.2%) andthose without shell (59.3%), followed by the rest of the individuals with and without shell, 16.9%and 12.4%, respectively. All hermits preferred mollusc shell Bulla striata, when offered inconjunction with the shell of Astrea tecta. However, all specimens returned to C. atratum shells whenit was experimentally offered with all shells. Studies with hermits have shown that the species haspreferences of gastropods shell C. atratum.

Piabanha, Brycon gouldingi, is an endemic species in the Tocantins-Araguaia basin. It hasaroused the interest of both fish farmers, who started its creation in confinement, and riverine peoplewho appreciate it as a food source. In order to provide information about organic systems ofB. gouldingi larvae, a histological description was performed after capturing adult specimens in theRio das Mortes (Mato Grosso, Brazil), adapted to captivity and induced to spawn at Buriti Fisheries(Nova Mutum, MT, Brazil). The collection of samples took place at pre-defined moments afterhatching, and the processes relating to morphological differentiation of digestive, excretory, cardiorespiratory, nervous/sensory systems and gas bladder were characterized. At the hatching werefound: undifferentiated digestive system; pronephros (primitive kidney), rudimentary heart, centralnervous system characterized by primary vesicles, optic vesicle forming the optic cup and crystallinelens. In the course of ontogeny, these organic systems were developed and at the time of the totalabsorption of the yolk at 55 hours post-hatching were found: the digestive system consisting of thehead gut, foregut, midgut and hindgut; two heart chambers and branching of gill arches; three regionsof the brain (forebrain, midbrain and hindbrain), neuromasts, olfactory cavity, taste buds; eyeconsisting of well-defined layers; presence of gas bladder. The results of this study may be useful inproviding support for the captive breeding of B. gouldingi during the larval stage.

The spectrum size has been used to assess environmental disturbances and tounderstanding the energy flow in ecosystems. The objective of this work was to investigate if theoperation regimes of reservoirs, including run-of-river and storage systems, interfere with thebiomass spectra of fish fauna. We tested the hypothesis that the run of river reservoirs present higherproportions of large individuals than storage system. Samplings of fish fauna were carried outbetween January 2005 and December 2007 at six Neotropical reservoirs belonging to the sub-basinIguaçu River and Coastal basin in São Jorge River, Brazil. The spectrum calculation was performedusing the Pareto type I continuous distribution model. Reservoirs operated under run-of-river regimehad significantly higher values than those operated under storage regimes. This study has elucidatedsome impacts of reservoir operating regime on biomass spectra and indicated differences in sizespectra of fish assemblages among the sampled reservoirs. Therefore, it is important to incorporatemanagement plans that take dam operating mode into account so that conservation of aquatic fauna, especially fish, is more effective.