Methodology for assessing the individual role of fish, oyster, phytoplankton and macroalgae in the ecology of integrated production in earthen ponds.

Production costs in extensive and semi-intensive fish culture in earthen ponds are often too high to offer sustainable economic activity due to the low productivity of these systems. The right combination of commercial finfish species with inorganic (primary producers) and organic extractive (bivalves) species in Integrated MultiTrophic Aquaculture (IMTA) create a balanced system with higher profitability and risk reduction. To achieve this, it is crucial to understand the role of each functional groups within the system what we did by comparing three different IMTA production three different IMTA production treatments with distinct combinations of trophic levels: •fish, filter feeders, phytoplankton and macroalgae,•fish, filter feeders and phytoplankton•fish, phytoplankton and macroalgae Each treatment was carried out in two similar ponds under semi-intensive conditions and flow through system, in a total of 6 earthen ponds of 500 m2 surface and depth of 1.5 m. Results showed that the presence of oysters in the ponds enhanced water quality by decreasing turbidity and by controlling phytoplankton which led to regulation of dissolved oxygen levels. The enhanced water quality in these systems lead to improved fish performance and higher biomass production contributing to greater profitability. The combination of fish, oyster, phytoplankton and macroalgae was particularly good providing much more fish supply compared with the other two treatments. •Oysters enhanced water quality in the ponds by decreasing turbidity and controlling phytoplankton which regulated the dissolved oxygen levels.•The enhanced water quality in systems with oysters improve fish performance resulting in higher biomass production and greater profitability.•The combination of fish, oyster, phytoplankton and macroalgae was particularly good providing much more fish supply compared with the other two treatments.

Ostreid herpesvirus in wild oysters from the Huelva coast (SW Spain).

This is the first report of ostreid herpesvirus 1 microvariant (OsHV-1 µVar) infecting natural oyster beds located in Huelva (SW Spain). The virus was detected in 3 oyster species present in the intertidal zone: Crassostrea gigas (Thunberg, 1793), C. angulata (Lamarck, 1819) and, for the first time, in Ostrea stentina Payraudeau, 1826. Oysters were identified by a specific polymerase chain reaction (PCR) and posterior restriction fragment length polymorphism (RFLP) analysis based on cytochrome oxidase I (COI) mitochondrial DNA. Results confirmed that C. angulata still remains the dominant oyster population in SW Spain despite the introduction of C. gigas for cultivation in the late 1970s, and its subsequent naturalization. C. angulata shows a higher haplotype diversity than C. gigas. OsHV-1 virus was detected by PCR with C2/C6 pair primers. Posterior RFLP analyses with the restriction enzyme MfeI were done in order to reveal the OsHV-1 µVar. Detections were confirmed by DNA sequencing, and infections were evidenced by in situ hybridization in C. gigas, C. angulata and O. stentina samples. The prevalence was similar among the 3 oyster species but varied between sampling locations, being higher in areas with greater harvesting activities. OsHV-1 µVar accounted for 93% of all OsHV-1 detected.

Larval and juvenile development of dusky grouper Epinephelus marginatus reared in mesocosms.

The larval development of the dusky grouper Epinephelus marginatus up to the benthic juvenile stage is described in detail to establish a reference for their larval identification. Development is described in terms of ontogenetic changes in morphology, growth, pigmentation, fin structure and skeletal structure. Larvae were reared in mesocosms at a mean temperature of 24·3° C, salinity of 36·5, dissolved oxygen of 6·4 mg l(-1) and pH of 8·2. Newly hatched larvae had an estimated total length (LT ) of 2·3 mm. On the second day post hatching the yolk was almost fully absorbed with traces of the oil globule still present, the eyes were already pigmented and mouth and gut functional. At this stage the cranial skeletal elements for feeding and breathing (mouth and gills) and the pectoral-fin support were already present. About 50% of the observed larvae had food in their guts. Pigmentation was very characteristic, consisting of two large chromatophores visible on the edge of the primordial fin, close to the midpoint of the post-anal region of the body and over the midgut and hindgut and post-anal portion of the body. At 2·9 mm LT the emergence of the second dorsal-fin spine, characteristic of the Epinephilinae, was clearly visible. The pre-flexion stage started in larva of 3·2 mm LT . At 5·5 mm LT the larvae possessed posterior preopercular angle spines, and the dorsal and pelvic spines presented serrated edges and were pigmented. The water surface-tension-related death of the yolk sac and pre-flexion larvae described in the rearing of several other grouper species did not occur during E. marginatus culture. Notochord flexion, with initial ossification of the caudal-fin supporting elements, started at 6·6 mm LT . At this stage the major melanophores, preopercular, dorsal and pelvic spines and mandibular teeth were already present. Transformation of larvae into juveniles occurred when larvae averaged 13·8 mm LT . Juveniles with a mean LT of 20·1 mm started to settle and most of them were benthic with a mean LT of 26·8 mm.

Isotopic composition as a tool for assessment of origin and dynamic of organic matter in tropical freshwater.

The isotopic composition (13C and 15N) and C:N ratio of sediment and particulate were investigated to assess the origin and dynamic of the organic matter in two river basins located in the Parana State, Brazil. The main sources of organic matter, plants, litter and soil, were analyzed in the study. This study was carried out during the dry and wet seasons. Although organic matter contribution for the particulate material has been mixed, the main contribution in the two seasons for both rivers was autochthonous characterized by delta13C and C:N ratio values ranging from -31.0 to -21.8 per thousand and from 5.1 to 11.4, respectively. The soil with delta13C values ranging from -25.9 to -20.6 per thousand, and C:N ratio from 10.2 to 15.8, was the main carbon source for the river sediment for the two tributaries in the wet and dry seasons. The sediment delta15N values for both the rivers in the wet season showed an 15N enrichment trend in most of studied sites when compared to the dry season values, suggesting major input of nutrients as dissolved organic nitrogen and sewage nitrate. In the dry season, 14N enriched compounds, could have been used by phytoplankton, causing 15N enrichment. The isotope and C:N ratio data clearly showed that the agricultural activity has been influencing the origin and dynamic of organic matter in the two rivers, with potential biochemical consequences for the lower basin of the major Tibagi river.

Influence of sublingual captopril on plasma catecholamine levels during hypertensive emergencies and cold immersion.

Experimental evidence of captopril-induced inhibition of sympathetic activity, mediated by decrease in angiotensin II production, is presented. The blood pressure, plasma catecholamine, plasma renin activity, and plasma aldosterone responses to a single dose of sublingual captopril in 23 patients with hypertensive emergencies were evaluated. The major correlation found was between the captopril-induced decrease in blood pressure and the decrease in plasma norepinephrine levels (r = 0.57, p less than 0.01). In another 11 hypertensive patients with normal or high renin levels, captopril lowered by 65 percent the increase in plasma norepinephrine induced by cold immersion of the forearm. In both circumstances, plasma renin and aldosterone levels changed in accordance with the expected inhibition of angiotensin converting enzyme activity. These data suggest that, in selected circumstances in hypertensive patients, captopril exhibits a depressive influence on sympathetic activity along with the inhibition of the renin-angiotensin system.