Showing papers by "University of the Algarve published in 1998"

Development of osteological structures in the sea bream: vertebral column and caudal fin complex

Abstract: The development of cartilaginous structures in cultured sea bream Sparus aurata larvae and the timing of their ossification was studied. In cultivated sea bream larvae the first cartilaginous structure to be identified was hypural 1 at 4.1 mm notochord length (LN). By 5.3 mm LN, prior to the onset of ossification, it was possible to distinguish the following cartilaginous structures: all 23 neural arches, all 13 haemal arches and two of the four pairs of parapophyses. The neural arches 1–4 and 15–23 were formed on the notochord and elongated dorsally, while neural arches 5–14 appeared on the dorsal side of the spinal cord and elongated ventrally. Initiation of ossification occurred at 5.7–6.0 mm standard length (LS) when the cartilaginous ontogeny of the vertebral column was completed. Ossification was coincident with dorsal flexion at the posterior end of the notochord and occurred in a sequential manner: (1) dorsoanteriorly, the cartilaginous neural arches and the centra were the first structures to ossify; (2) ventrad at the centre, at 7.0–7.5 mm LS; (3) posteriorly at 7.1 mm LS the hypural complex and urostyle (24th centrum) were ossified; and (4) dorsad at the centre (neural arches and spines).

The effect of ration level and social rank on the development of fin damage in juvenile rainbow trout

Abstract: The development and severity of fin damage was examined in groups of juvenile rainbow trout Oncorhynchus mykiss of different strength of feeding hierarchies The development of dorsal and caudal fin damage over time was compared between four groups fed different ration levels (0·25, 0·5, 1·0 and 1·5% body weight day−1) and between individuals of different feeding rank within each group Dominance hierarchies were assessed from repeated daily measurements of food consumption of individuals using radiography The feeding and growth data indicated that the strength of the social hierarchy weakened with increasing ration Caudal fin damage developed with time in all groups whereas dorsal fin damage developed only under limited rations The severity of both dorsal and caudal fin damage was significantly dependent on the ration size fed to the group, with lower ration groups sustaining more fin damage The severity of dorsal fin erosion was greater than for the caudal fin Within the two lower ration groups, subordinate fish suffered the most dorsal fin damage The results suggested that the severity of dorsal fin damage within groups of juvenile rainbow trout can be used as an indicator of hierarchy Strength

The effect of stocking density on growth in the gilthead sea‐bream, Sparus aurata (L.)

Abstract: The effect of stocking density on growth and size variability in gilthead sea-bream, Sparus aurata (L.), was tested by growing juveniles at densities of 0.35 kgm−3, 1.3 kg m−3 and 3.2 kg m−3. Fish in the highest density group grew 25% slower than fish in the lowest density group. The coefficient of variation of weight (standard deviation/mean) did not change during the experiment. The effect of size variability on growth rate was tested by creating groups with coefficients of variation of weights ranging from 0.11 to 0.32, and growing them at similar density (1.5 kg m−3). No differences in growth rates between groups were found. Only the more heterogeneous group showed a large decrease in the coefficient of variation over time. It was concluded that growth in gilthead sea-bream, although negatively correlated to stocking density, did not seem to be related to intraspecific competition as assessed by changes in size variability.

Spherical 2-categories and 4-manifold invariants

Abstract: In this paper I define the notion of a non-degenerate finitely semi-simple semi-strict spherical 2-category of non-zero dimension. Given such a 2-category I define a state-sum for any triangulated compact closed oriented 4-manifold and show that this state-sum does not depend on the chosen triangulation by proving invariance under the 4D Pachner moves. This invariant of piece-wise linear closed compact oriented 4-manifolds generalizes the Crane-Yetter invariant and probably it is also a generalization of the Crane-Frenkel invariant. As an example we show how to obtain a 2-category of the right kind from a finite group and a 4-cocycle on this group. The invariant we obtain from this example looks like a four dimensional version of the Dijkgraaf-Witten invariant.

Constraints on the structure of the Azores spreading center from gravity data

Abstract: The Azores Archipelago is believed to be the site of the third arm of a Triple Junction between the Eurasia/Africa/North America plates. However, to the present no study has been able to identify its segmentation pattern, the spreading mechanism and its relationship with the well-known topographic features of the Mid-Atlantic Ridge (MAR). Here we present a new gravity compilation obtained with the existing National Geophysical Data Center (NGDC) data, merged with new gravity profiles collected during the ESCAPE cruise in 1995. This compilation is used to calculate a Free Air Anomaly (FAA) map, which is used to test two different models, the Mantle Bouguer Anomaly model and the elastic plate model, for the study of the thermal regime of the Terceira Axis. The analysis of the results from both models demonstrates that the elastic plate model successfully models the gravity data from the Azores Plateau and that there is no gravity evidence for the existence of a spreading axis. The elastic plate thickness Te, with a value of 7–8 km, suggests a very young lithosphere (about 10 Ma) at the time of the load of the Azores Plateau.

A comparative study of the feeding ecology of Nephrops norvegicus L. (Decapoda: Nephropidae) in the bathyal Mediterranean and the adjacent Atlantic

Abstract: A comparative study of the feeding ecology of Nephrops norvegicus was carried out on a seasonal basis simultaneously in seven locations in the Eastern and Western Mediterranean and the adjacent Atlantic: the south coast of Portugal, Faro; the Alboran Sea, Malaga; the Catalan Sea, Barcelona; the Ligurian Sea, Genoa; theTyrrhenian Sea, Pisa; the Adriatic Sea, Ancona and the Aegean Sea, Gulf of Euboikos. The major groups observed (frequency of occurrence method) in the stomachs of Nephrops norvegicus were decapod crustaceans, other crustaceans (euphausids and peracarids) and fish. The results obtained showed no significant differences between sites or seasons, and can be considered very consistent. All major taxa were present in the diet at all sites and for all seasons, a fact that can be explained by the great similarity of the bathyal fauna in all sites, which provide a major trophic resource for N. norvegicus. The percentage of fullness was also estimated per site and season, and we registered a clear decrease of this value during the summer period for all sites, except the Tyrrheanian Sea, where the lowest value was found in autumn. PCA - analysis did not clearly separate the regions (sites). The Shannon-Weaver (H´), index of diversity, was also determined per site and season, and we found a significant difference between the values of the Atlantic coast and the Western Mediterranean when compared with those of the Eastern Mediterranean.

Histochemical study of skin and gills of Senegal sole, Solea senegalensis larvae and adults

Abstract: A battery of horseradish peroxidaseconjugated lectins (Con A, WGA and DBA), as well as conventional histochemical techniques (PAS, saponification, A1cian Blue pH 0.1, 1,2.5, chlorhydric hydrolisis, neuraminidase , Bromophenol blue, Tioglycollate reduction and Ferric-ferricyanide-FeIlI) were used to study the content and distribution of carbohydrates, proteins and glycoconjugate sugar residues on the skin and gills of Senegal sole, Solea senegalensis larvae and adults. During larval development of Solea senegalensis (from hatching until day 45 posthatching), epidermal sacciform, as well as branchial and epidermal chloride cells were unreactive with all cytochemical tests performed in this paper. Mucous or goblet cells of the corporal skin and gills containing strongly sulphated acid glycoproteins were evident on days 15-20 of larval development , as well as in epidermal and branchial mucous cells of adult specimens, which also contained GIcNAc and/or sialic acid. In adult specimen, the proteic content was higher in branchial mucous cells than in epidermal cells. In larvae, variable amounts of glycoproteins containing sialic acid, GlcNAc, GaINAc, Man and/or GIc residues were observed in epithelial cells and/or cuticle. GIcNAc and/or sialic acid sugar residues were only weakly detected in glycoproteins of some epidermal and branchial mucous cells of larvae by day 45, because from hatching until metamorphosis, lectin reactions (WGA, Con A and DBA) were negative in mucous cells.

Light response curves for Gelidium sesquipedale from different depths, determined by two methods: O2 evolution and chlorophyll fluorescence

Abstract: Photosynthesis-light response curves of Gelidium sesquipedale from the west coast of Portugal (Cape Espichel) were determined at four different depths, 3, 10, 15 and 22 m. Data acquisition using chlorophyll a fluorescence methodology and oxygen electrode measurements were compared. Response curves were determined over an increasing range of irradiance values (I), from darkness to 900 μmol photon m-2 s-1 PAR. In general, light response curves obtained for G. sesquipedale showed a similar pattern whether determined by the chlorophyll fluorescence method or by oxygen evolution. The photosynthetic capacity of G. sesquipedale decreased with depth, as expected, revealing a ‘sun’ and ‘shade’ acclimation pattern, between shallow and deeper waters.

Deactivation and conformational changes of cutinase in reverse micelles

Abstract: Deactivation data and fluorescence intensity changes were used to probe functional and structural stability of cutinase in reverse micelles. A fast deactivation of cutinase in anionic (AOT) reverse micelles occurs due to a reversible denaturation process. The deactivation and denaturation of cutinase is slower in small cationic (CTAB/1-hexanol) reverse micelles and does not occur when the size of the cationic reverse micellar water-pool is larger than cutinase. In both systems, activity loss and denaturation are coupled processes showing the same trend with time. Denaturation is probably caused by the interaction between the enzyme and the surfactant interface of the reversed micelle. When the size of the empty reversed micelle water-pool is smaller than cutinase (at W0 5, with W0 being the water:surfactant concentration ratio) a three-state model describes denaturation and deactivation with an intermediate conformational state existing on the path from native to denaturated cutinase. This intermediate was clearly detected by an increase in activity and shows only minor conformational changes relative to the native state. At W0 20, the size of the empty water-pool was larger than cutinase and the data was well described by a two-state model for both anionic and cationic reverse micelles. For AOT reverse micelles at W0 20, the intermediate state became a transient state and the deactivation and denaturation were described by a two-state model in which only native and denaturated cutinase were present. For CTAB/1-hexanol reverse micelles at W0 20, the native cutinase was in equilibrium with an intermediate state, which did not suffer denaturation. 1-Hexanol showed a stabilizing effect on cutinase in reverse micelles, contributing to the higher stabilities observed in the cationic CTAB/1-hexanol reverse micelles. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58:380–386, 1998.

Fluorescent sands for measurements of longshore transport rates: a case study from Praia de Faro in southern Portugal

Abstract: A field experiment was carried out on a mesotidal reflective beach to relate longshore sand transport rates to wave measurements in medium-energy conditions (H rms =0.6 m; T m =6.5 sec; α=20°). Dispersion of fluorescent sand tracers was analyzed using the spatial integration method (SIM). The measured sand transport rate was three times larger than the prediction computed using the longshore wave power approach, while the K factor was determined empirically as 2.32. The study concluded that there is a need to calibrate bulk longshore transport predictors before applying them to steep gradient slopes under plunging waves.

The composition of phosphate granules in the digestive glands of marine prosobranch gastropods: variation in relation to taxonomy

Abstract: The composition of some 1150 phosphate granules in the digestive glands of over 40 species of marine prosobranch gastropods has been surveyed using a simple preparation technique and semi-quantitative SEM x-ray microanalysis. Spectral peaks for Mg, K, Ca, Mn, Fe and Zn were compared to that of P. Four major types of phosphate granule can be recognised, each generally characteristic of a taxonomic grouping: high Mg in archaeogastropods and littorinids, multiple metal in higher mesogastropods, and, in neogastropods, Mg-Ca in muricoideans and high Zn in buccinoideans. At least one Conus species (C. ventricosus) has high-Mg granules. Some causes of variation in granule composition are discussed: speculatively, it is suggested a palaeoenvironm ental influence seems possible.

Plasma concentrations of ovarian steroids in relation to oocyte final maturation and ovulation in female plaice sampled at sea

Abstract: Blood plasma concentrations of free 17β-oestradiol, free testosterone and glucuronidated testosterone were strongly positively related to the percentage of vitellogenic oocytes remaining in the ovaries of plaice Pleuronectes platessa caught at sea–being at their highest in pre-spawning (stage IV) females (i.e. those in which the oocytes were close to fully grown, but had not yet entered the stage of final maturation). In contrast, the concentrations of free and sulphated 17,20β-P, 3αaL,17, 20β-P-5β, and 3α,17,21-P-5β were at their lowest in stage IV females. Free 17,20β-P (the putative maturation-inducing steroid) became only slightly elevated (less than twofold) during spawning (i.e. in stage V and VI females with hydrated and/or ovulated eggs). Sulphated 17,20β-P and 3α,17,21-P-5β became slightly more elevated (three- to fourfold). However, sulphated 3α, 17,20β-P-5β concentrations increased 30-fold and were at their highest in fish in which only 40% of vitellogenic oocytes remained in the ovaries. Sulphated 17,20β-P, 3α, 17, 20β-P-5β and 3α,17,21-P-5β concentrations were significantly positively related to hyaline oocyte batch size; and sulphated 17,20β-P and sulphated 3α, 17,20β-P-5β were significantly negatively related to the degree of hydration of the hyaline oocytes. None of the steroid concentrations, however, was related to the time of capture. More ovulated females were found in the afternoon than at any other time of the day.

Feeding ecology of Nephrops norvegicus (Decapoda: Nephropidae)

Abstract: The stomach contents of 248 Norway lobsters were analysed. Prey specimens were identified to the lowest taxonomical level possible. The frequency of occurrence method was used to analyse the data and the results are presented considering only major groups. The results obtained indicate great diversity in terms of prey in the stomachs of Nephrops norvegicus, with a clear preference for decapods, followed by other crustaceans and fish. Seasonal changes in the diet were not significant; particularly for the major groups.

Pilot-scale production of mysid shrimp in a static water system

Abstract: Studies were conducted to determine the potential for large scale culture of the mysid shrimp Mysidopsis almyra. Reproduction was consistent, as newly hatched mysids were always present in the culture trays. At the end of 45 day preliminary trials, the populations in the culture trays had increased 323.3% and 256.6%. A larger pilot-scale system connected to a biological filtration tank was constructed and operated for 17 weeks. Two rectangular trays (125 cm × 50 cm × 8 cm deep) were placed one above the other; water volume in each tray was 20 l. The room was kept dark. Temperatures were maintained at 26(2) °C and salinities at 20(2)‰. A total of 1,000 adult mysids were placed in the culture tray and the hatchlings were collected and moved into a hatchling tray. Water circulation was static except for twice-daily water exchanges; newly hatched Artemia nauplii (24 h incubation) were fed to the mysids immediately after each water exchange. Feeding presented no technical problem to the pilot-scale culture of mysids in static water systems but the cost of Artemia did represent the largest expense. Mean (SD) mysid production throughout the 17 weeks of the trial was 133(69) hatchlings d–1 with highest production [244(30) hatchlings d–1] occurring between weeks 11 and 13. Mean survival in the hatchling tray after the 14 day growth periods was 41.4%. Reproduction occurred at ammonia-nitrogen and nitrite-nitrogen concentrations as high as 1.5 mg l–1 and 0.250 mg l–1 respectively, and at pH values as low as 7.6. When pH decreased to 7.38, reproduction halted abruptly and mortality increased sharply. © Rapid Science Ltd. 1998