Vertical migration of the crab Carcinus maenas first zoea in an estuary: implications for tidal stream transport

The first zoea of Carcinus maenas (L.) was intensively sampled in the Canal de Mira (Ria de Aveiro, Portugal) during the winter and spring of 1990. Each sampling period included a series of 25 h fixed-station plankton sampling cycles (12 in winter and 9 in spring), conducted at 1 station located in the lower part of the Canal. Plankton samples were collected every hour, at several depths along the water column, with the use of a pump. Hydrological measurements (salinity, temperature and current velocity and direction) were taken immediately before the collection of the plankton samples. The average depth of the zoeae changed in phase with the tide: larvae reached their highest position in the water column during ebb and their lowest during flood. The extent and phasing of the vertical displacements were such that the first zoea occupied a significantly higher position during the span of the ebb than during flood (p < 0.001). It was also demonstrated that the larvae were significantly closer to the surface during the night (p < 0.05). The pattern of vertical dispersion of the zoeae changed cyclically, with a period equivalent to the tidal half-cycle. Maximum aggregation usually occurred during periods of high current velocity and was independent from water stratification. These observations support the hypothesis that C. maenas first zoea performs an active vertical migration synchronised with tidal and daily cycles. Analysis of the zoeae instantaneous velocity showed that shifts of vertical position according to the phases of tide and day influenced their transport velocity, due to vertical differences of water velocity in the estuarine shear current system. During ebb the larvae were transported at a velocity that exceeded the vertically integrated water velocity; the reverse relationship was observed during flood (p < 0.001). The larvae were also transported faster during the night than during the day (p < 0.05). These results demonstrate that selective tidal stream transport can be generalised in the sense of a unidirectional transport mechanism in estuaries that can enhance exportation

Larval abundance patterns of Carcinus-Maenas (Decapoda, Brachyura) in Canal de Mira (Ria de Aveiro, Portugal)

Larval stages of Carcinus maenas (L.) were intensively sampled in the Canal de Mira (Ria de Aveiro, Portugal) during 2 lunar months: February 12 to March 11 and May 9 to June 7, 1990. Each sampling period included fifteen 25 h fixed-station sampling cycles beginning at intervals of 4 tide cycles. Within each 25 h sampling cycle, plankton samples were collected hourly at several depths using a pump. Analysis of the data from these sampling periods indicated tidal and diel cycles of abundance of first stage C. maenas larvae. A semilunar component was also identified. These patterns were expressed as peaks of abundance during ebb tides, with highest peaks during nocturnal neap ebb tides around the first and last quarters of the moon. Peaks of nocturnal abundance could occur at any time during the night but consistently followed high water. In contrast, megalopae were present in the samples primarily during nocturnal flood tides. Intermediate zoeal stages of C. maenas were not collected. As indicated by an analysis of variance, the main effects of phases of the tide and day on the abundance of first zoeae and megalopae were significant (p < 0.05). These results provide evidence that a component with semilunar periodicity is associated with the release of C. maenas larvae. That the release activity occurs well after sunset is also an additional interesting feature of these observations, inasmuch as larval release in decapods is usually concentrated within the first few hours after dusk. These observations support earlier observations that it is the time during the day-night cycle of high tide, as opposed to tidal amplitude, which is the important factor promoting synchrony with the lunar cycle

Chemical constituents of the volatile oil from leaves of Annona coriacea and in vitro antiprotozoal activity

The essential oil of the leaves from Annona coriacea Mart., Annonaceae, was extracted by hydrodistillation in a Clevenger apparatus and analyzed by GC/MS and GC/FID. The oil yield was 0.05% m/m. Sixty compounds were identified, in a complex mixture of sesquiterpenes (76.7%), monoterpenes (20.0%) and other constituents (3.3%). Bicyclogermacrene was its major compound (39.8%) followed by other sesquiterpenes. Most of the monoterpenes were in low concentration (<1%). Only &#946;-pinene and pseudolimonene presented the highest level of 1.6%. The volatile oil presented anti-leishmanial and trypanocidal activity against promastigotes of four species of Leishmania and trypomastigotes of Trypanosoma cruzi, showing to be more active against Leishmania (L.) chagasi (IC50 39.93 µ g/mL) (95% CI 28.00-56.95 µ g/mL)

Economic indexes of banana production (Musa Sp.) in the brazilian semiarid region

Applying several economic indexes commonly used in national scientific research, we assessed the productive efficiency of banana crops in commercial areas of the Brazilian semi-arid region. The analysis of income, through economic indexes, provided an overview of the effectiveness of administration and workforce. The result of the multivariate analysis revealed (i) three independent groups composed by the total net profit, and (ii) a subgroup joined by the opportunity cost, the interest rate for the period from planting to harvest, and the leveling point. The best options for net return on banana propagation in the Brazilian semiarid region were (i) the use of conventional management, (ii) the cultivation of Pacovan cultivar propagated by rhizome without "ceva" and, (iii) use of the Dwarf Prata cultivar propagated by rhizome with "ceva". The economic resources applied to the banana production provided the best output among those evaluated since it exceeded four folds the obtained with the capital remuneration in the financial application

Planktonic stages of Processa macrodactyla (Decapoda: Caridea: Processidae) reared in the laboratory

Two ovigerous females of the processid shrimp Processa macrodactyla were caught in April 1997 at 13 m depth in coastal waters of Rota, Cádiz Bay, south-western Spain (36°36′N 6°18′W). Rearing was terminated after nine zoeal stages, when larvae moulted to the first juvenile instar. Descriptions of the appendages of every instar have been made so as to: (1) compare the larval morphology with that of other previous described known species in the genus Processa (P. canaliculata, P. edulis, P. elegantula, P. modica, P. nouveli); and (2) with those larvae not ascribed to a certain species in order to facilitate the specific identification of unknown collected planktonic larvae. When describing P. macrodactyla some characters remained, with few exceptions, invariable in their setation form ZI to ZIV or ZV, to then change and maintain until the last zoeal stage. This can be due to intermediate moults, with the result that some larvae unite the characters of Stages ZIV and ZV and others those of ZV and ZVI