Biochemical Characterization and Distribution of Glutathione S-Transferases in Leaping Mullet (Liza saliens)

In this study, feral leaping mullet (Liza saliens) liver cytosolic glutathione S-transferases (GSTs) were investigated and characterized using 1-chloro-2,4-dinitrobenzene (CDNB) and ethacrynic acid (EA) as substrates. The average GST activities towards CDNB and EA were found to be 1365 +/- 41 and 140 +/- 20 nmol/min per mg protein, respectively. The effects of cytosolic protein amount and temperature ranging from 4 to 70 degrees C on enzyme activities were examined. While both activities towards CDNB and EA showed similar dependence on protein amount, temperature optima were found as 37 and 42 degrees C, respectively. In addition, the effects of pH on GST-CDNB and -EA activities were studied and different pH activity profiles were observed. For both substrates, GST activities were found to obey Michaelis-Menten kinetics with apparent V(max) and K(m) values of 1661 nmol/min per mg protein and 0.24 mM and 157 nmol/min per mg protein and 0.056 mM for CDNB and EA, respectively. Distribution of GST in Liza saliens tissues was investigated and compared with other fish species. Very high GST activities were measured in tissues from Liza saliens such as liver, kidney, testis, proximal intestine, and gills. Moreover, our results suggested that GST activities from Liza saliens would be a valuable biomarker for aquatic pollution.     

Cascading effects of the flathead grey mullet Mugil cephalus in freshwater eutrophic microcosmos

Flathead grey mullet (Mugil cephalus L.) stocked in fish ponds were long considered to feed primarily on detritus. However, recent research has found that they obtain much of their food from plankton and that they have a detrimental effect on pond zooplankton and large phytoplankton, whilst enhancing small phytoplankton. It has been suggested that flathead grey mullet may also increase the internal phosphorus loading of the ecosystem, which would also increase phytoplankton density. To test whether zooplankton removal or nutrient release from the sediment is the better explanation for phytoplankton enhancement in the presence of flathead grey mullet, the ecosystems of fish-less tanks, tanks with a 60 m mesh filter and tanks stocked at a fish density of 243 g m^-3 were compared. In the presence of flathead grey mullets, cladocerans, ostracods and chironomid larvae became scarcer than in the control tanks, while there were more small phytoplankton and mud snails. The green algae Cladophora sp. did not occur at all. The presence of a mechanical filter also reduced cladoceran, ostracod and chironomid densities and increased phtyoplankton and mud snail density. However, the situation observed in filter tanks was intermediate between that observed in the fish tanks and the control tanks, due to the lower filtering efficiency of the mechanical filter. The organic matter content of the sediment decreased throughout the experiment in the control and filter tanks, but remained stable in fish tanks. Phosphorus and nitrogen concentrations were not affected by any treatment. These results showed that flathead grey mullet enhanced phytoplankton development due to the removal of large cladocerans and not as a consequence of nutrient release. Furthermore, the flathead grey mullet strongly modified the benthic community, probably due to direct predation.     

Motile aeromonas infection of striped (grey) mullet Mugil cephalus

Infection of striped mullet (Mugil cephalus) with Aeromonas hydrophila results in an acute septicemic disease. The disease can be experimentally induced by intramuscular injection, skin or gill scarification or by the oral route using pellets purposely seeded with bacteria. The organism was isolated from the blood 1–2 days after infection and from all organs 24 hr or longer after infection. The disease is characterized by early inflammatory and proliferative changes and later necrotic changes. Enteritis and hepatic necrosis are constant findings in aeromonad disease of M. cephalus but surface lesions are not pathognomic for these infections in mullet. Death of infected fish may be attributed to bacterial toxins which cause necrosis of parenchymal organs and soft tissue structure.     

The osteology of the golden grey mullet Liza aurata (Teleostei: Mugiliformes: Mugilidae) including interactive three-dimensional reconstructions

Grey mullets are remarkably characterized by their overall uniform external morphology. Identifying species as well as positioning the Mugiliformes in a phylogenetic context is rather difficult. Most recently they were placed in the newly erected Ovalentaria, but more detailed relationships to potential sister taxa were not resolved. Studying the internal morphology, especially the osteology, might provide new insights into the evolution of the Mugiliformes as well as help clarify their phylogenetic position within the Ovalentaria. A detailed osteology of the golden grey mullet Liza aurata is presented. The use of cleared and stained specimens allowed for a complete examination of bony and cartilaginous structures, and a 3D reconstruction from a μCT data set provided additional information on the positional relationships of the bones. Following this, the data obtained were compared with different mugilid species, particularly with the flathead grey mullet Mugil cephalus. Several differences between these species could be identified, such as the position of the basisphenoid, the shape of the hyomandibular and the composition of the branchial arches. These characters might help in understanding the evolutionary changes happening within the mugiliforms and will provide the basis to study this taxon in detail, finally allowing the reconstruction of the body plan of grey mullets.     

Cloning, sequencing, and characterization of CYP1A1 cDNA from leaping mullet (Liza Saliens) liver and implications for the potential functions of its conserved amino acids

A 2,037 bp CYP1A1 cDNA (GenBank AF072899) was cloned through screening of a lambdaZipLox cDNA library constructed from the liver of a leaping mullet (Liza saliens) fish captured from Izmir Bay on the Aegean coast of Turkey using rainbow trout CYP1A1 cDNA as a probe. This clone has a 130 bp 5'-flanking region, a 1,563 bp open reading frame (ORF) encoding a 521-amino acid protein (58,972 Da), and a 344 bp 3'-untranslated region without a poly (A) tail. Alignment of the deduced amino acids of CYP1A1 cDNAs showed 58% and 69-96% identities with human and 12 other fish species, respectively. Southern blot analysis suggested that this CYP1A1 cDNA was from a single-copy gene. Based on the comparison with CYP1A1 genes reported for fish and mammals, the leaping mullet CYP1A1 gene is probably split into 7 exons. The intron insertion sites were predicted. Alignment of the CYP1A1 cDNA encoded amino acids from 13 fish and 7 mammalian species disclosed differences in highly conserved amino acids between aquatic and land vertebrates. The possible associated secondary structure; conserved motifs and substrate-binding sites were discussed. The phylogenetic relationships of CYP1A1s among 13 fish species were analyzed by a distance method.     

Fine structure of hepatocytes in juvenile grey mullets: Liza saliens Risso, L. ramada Risso and L. aurata Risso (Teleostei, Mugilidae)

Livers of 45 fingerling grey mullets ( Liza sp. 5-15 cm long) were subjected to light microscopy, transmission electron microscopy and enzyme cytochemical examination. The hepatic structure was found to be comparable in all three Liza species. As in other fish species, Liza liver parenchyma is arranged in cords (or dual-plated laminae, in sections parallel to the sinusoidal axis). Hepatocytes showed numerous microvilli in their perisinusoidal and canalicular areas. They contained a centrally located nucleus, fairly large areas of rough endoplasmic reticulum, consisting mainly of parallel cisternae, and pools of glycogen. A few small lipid droplets were evenly distributed in the cytoplasm. The Golgi fields, between the canaliculus and the nucleus, consist mainly of dictyosomes, lysosomes and autophagic vacuoles. Acid phosphatase activity was cytochemically localized to reaction products in secondary lysosomes and lipofuscin granules. A comparison between grey mullet liver and that of other teleosts was made.     

Phylogenetic relationships of nine mullet species (Mugilidae) in the Mediterranean Sea

Phylogenetic relationships among four genera and nine species (Mugil cephalus, Mugil soiuy, Liza ramada, Liza aurata, Liza abu, Liza saliens, Liza carinata, Chelon labrosus, Oedalechilus labeo) of the Mediterranean mullets (Mugilidae) were investigated by means of allozyme electrophoresis using a seven-enzyme system (CK*, GAPDH*, G3PDH*, IDHP*, ME*, MDH*, PGM*) comprising eleven putative loci. The highest genetic divergence was 1.299, detected between M. cephalus and L. aurata and the lowest (0.280) was found between L. carinata and L. saliens. The amount of genetic divergence between the genera Chelon and Oedalechilus did not appear to be high (0.285). In a UPGMA tree, all nine species were grouped in two main branchings. In the first branch, C. labrosus and O. labeo clustered as closest taxa and were sister group to L. ramada. The other four Liza species produced two sub-branching in this group; L. carinata branched together with L. saliens, and L. aurata branched together with L. abu. In the second branch the two species of the genus Mugil, M. cephalus and M. soiuy, clustered together and were clearly isolated from the other three genera.     

Determination of Trace Element Level in Different Tissues of the Leaping Mullet (Liza saliens, Mugilidae) Collected from Caspian Sea

The concentrations of Cr, Cu, Fe, Mn, Ni, Pb, Cd, and Zn were determined in the brain, heart, liver, gill, gonad, spleen, kidney, and red and white muscles of Liza saliens (leaping mullet). Trace element levels in fish samples were analyzed by flame atomic absorption spectrometry. Among the non-essential metals, the levels of Ni and Pb in the tissues were higher than limits for fish proposed by FAO/WHO, EU, and TFC. Generally, the levels of the non-essential metals were much higher than those of manganese in the red and white muscles. Fe distribution pattern in tissues was in order of spleen?>?liver?>?heart?>?gill?>?brain?>?kidney?>?gonad?>?red muscle?>?white muscle. Red muscle was not within the safe limits for human consumption because non-essential metal (Ni, Pb) contents were higher than standard limits.     

Food items of the grey mullet Mugil cephalus in the Banc d'Arguin area (Mauritania)

The stomach and gut content of 22 Mugil cephalus from the Banc d'Arguin shallows (Mauritanian coast, West Africa) is examined. Quartz grains are the predominant material found in the stomach together with small portions of benthic diatoms and flakes, aggregates of fine-grained inorganic and organic particles. As the composition of this material is modified by a sorting procedure during feeding it is difficult to conclude, whether seagrass stands (muddy and mixed sediments with sand fraction) or sandy flats are preferred as feeding habitats. The animals studied did not or not relevantly utilize the non-diatom microphytes, though the environment of the Banc d'Arguin is rich in microbial mats (cyanobacteria), Vaucheria beds and epiphytic vegetation of seagrass leaves.     

Fatty acids as trophic markers of phytoplankton blooms in the Bahía Blanca estuary (Buenos Aires, Argentina) and in Trinity Bay (Newfoundland, Canada)

The fatty acid compositions of phytoplankton and major primary consumers were analyzed during the development of seasonal algal blooms in the Bahía Blanca estuary, situated on the southern coast of the province of Buenos Aires (Argentina), and Trinity Bay, at Sunnyside, on the eastern coast of Newfoundland (Canada). Primary consumers in the Bahía Blanca estuary were zooplankton dominated by the calanoid copepod Acartia tonsa. At Sunnyside, the primary consumers were the sea scallop Placopecten magellanicus, an ecological and economical important benthic bivalve. The study shows that in spite of obvious differences between the two environments and the analytical approaches employed in each case, the analyses of fatty acid biomarkers can provide relevant ecological information. The fatty acid composition of the lipids of Bahía Blanca phytoplankton (high concentrations of the fatty acids 14:0, 16:4ω1, and 20:5ω3) reflected the presence of diatoms as a major component throughout the bloom. Fatty acid markers of the post-bloom phytoplankton in Bahía Blanca indicated a decline of phytoplankton biomass, and a relatively high input of detritus and terrestrial plant materials to the particulate organic matter of the estuary. Linoleic acid (18:2ω6), a typical “terrestrial” fatty acid, was conspicuous in the lipids of the post-bloom particulate matter of the Bahía Blanca estuary; 18:2ω2 was subsequently incorporated into zooplankton lipids diatom markers were also prominent in the lipids of pre-bloom and bloom phytoplankton at Sunnyside; post-bloom phytoplankton showed higher proportions of 18:0, 18:1ω9, and 18:4ω3, characteristic and often major fatty acids of dinoflagellates. The fatty acids of the digestive gland of P. magellanicus reflected the fatty acid composition of the phytoplankton, whereas those of the adductor muscle were practically unaffected by the composition of the food. This organ-specific response of an animal to the fatty acid composition of the diet is examined in terms of different applications of the fatty acid marker concept.     

Feeding habits of grey gurnard,Eutrigla gurnardus (L., 1758), along the Catalan coast (northwestern Mediterranean)

The stomach content of 589 specimens of Eutrigla gurnardus (collected at quarterly intervals) have been analyzed to determine diet according to fish size and season. The results show that crustaceans (% No = 93%, %Weight = 81%) are the basic food and that teleostean fishes are quite important in the adult diet. The importance of nycthemeral migrators decreases significantly as size increases, whilst the importance of benthic prey increases inversely. In every size, the feeding intensity is greater at midday than in the morning. Larger prey are eaten in winter than in summer although feeding intensity is lower in winter.     

The microdistribution of mayflies (Ephemeroptera) in myriophyllum beds in Pennington Creek,Johnston County,Oklahoma

I studied the population densities and the microdistributions of the four most abundant mayfly (Ephemeroptera) nymphs in Myriophyllum heterophyllum beds in Pennington Creek, Johnston County, Oklahoma, from May to December, 1977. The section of the stream studied has relatively constant flow rates and temperatures throughout the year due to continuous inflow from groundwater. This uniform physical environment allows the plant beds to grow throughout the year and provide a permanent habitat. The four mayflies are Tricorythodes fictus (Tricorythidae), Caenis delicata (Caenidae), Baetis favistriga and B. quilleri (Baetidae). All four species are of similar size and feed by scraping periphyton from the surface of the Myriophyllum. T. fictus and the two species of Baetis have overlapping microdistributions in the leafy, upper one-half of the plant bed. T. fictus and C. delicata have overlapping microdistributions in the lower portion of the plant bed and roots. Each species has similar population densities where their distributions overlap. There is no significant selection for position with respect to current flow in the Myriophyllum for any of the species. Food and space are always abundant, especially in the top one-half of the Myriophyllum. There are no major changes in these trends over the year.     

Maturity and fecundity of golden grey mullet (Liza aurata Risso, 1810) in Iranian waters of the Caspian Sea

The objective of the study was to determine some reproductive parameters in the golden grey mullet (Liza aurata Risso, 1810) during two periods half a decade apart while also trying from limited data to identify changes in fecundity over the past half century. Maturity and fecundity of golden grey mullet caught in Iranian waters of the Caspian Sea is not well documented and were thus studied during several seasonal cycles during 2002–2004 to establish basic data on reproduction in the area. The fork length (FL) of 462 sampled fish was between 22.1 and 51.9 cm. The fork length–weight relationship derived from all fish was W = 0.0118FL^2.964. Overall male to female ratio was 1 : 1.42. The reproductive season extended from October to December. Fifty percent of sexual maturity was at FL 26.0 cm. Mature gonads were present in 20% of fish at age 3, 63% at age 4, 88% at age 5, and 97% at age 6. Individual absolute fecundity of the golden grey mullet ranged from 113 386 to 1.47 million eggs, with a mean (±SD) of 451 963 (±274,114.2). An overlap exists between the spawning and fishing seasons. Therefore, the start of the fishing season should be delayed for 1 month in order for stocks to complete their spawning.     

Diurnal time-activity budgets of redheads (Aythya americana) wintering in seagrass beds and coastal ponds in Louisiana and Texas

Diurnal time-activity budgets were determined for wintering redheads (Aythya americana) from estuarine seagrass beds in Louisiana (Chandeleur Sound) and Texas (Laguna Madre) and from ponds adjacent to the Laguna Madre. Activities differed (p<0.0001) by location, month, and diurnal time period. Resting and feeding were the most frequent activities of redheads at the two estuarine sites, whereas drinking was almost nonexistent. Birds on ponds in Texas engaged most frequently in resting and drinking, but feeding was very infrequent. Redheads from the Louisiana estuarine site rested less than birds in Texas at either the Laguna Madre or freshwater ponds. Redheads in Louisiana fed more than birds in Texas; this was partially because of weather differences (colder temperatures in Louisiana), but the location effect was still significant even when we adjusted the model for weather effects. Redheads in Louisiana showed increased resting and decreased feeding as winter progressed, but redheads in Texas did not exhibit a seasonal pattern in either resting or feeding. In Louisiana, birds maintained a high level of feeding activity during the early morning throughout the winter, whereas afternoon feeding tapered off in mid- to late-winter. Texas birds showed a shift from morning feeding in early winter to afternoon feeding in late winter. Males and females at both Chandeleur Sound and Laguna Madre showed differences in their activities, but because the absolute difference seldom exceeded 2%, biological significance is questionable. Diurnal time-activity budgets of redheads on the wintering grounds are influenced by water salinities and the use of dietary fresh water, as well as by weather conditions, tides, and perhaps vegetation differences between sites. The opportunity to osmoregulate via dietary freshwater, vs. via nasal salt glands, may have a significant effect on behavioral allocations.     

Metal concentrations in Sargassum algae from coastal waters of Nha Trang Bay (South China Sea)

The concentrations of metals, viz., Fe, Mn, Cu, Zn, Cd, Pb, and Ni, were investigated in brown algae of the genus Sargassum collected in the coastal waters of Nha Trang Bay (South China Sea). Metal concentrations in algae growing in the zone of influence of the city of Nha Trang were higher than those in macrophytes collected to the south and north of the city. Similar levels of Cu and Fe concentrations were observed in macrophytes from the urbanized coastal areas of Nha Trang Bay and in algae from the Peter the Great Bay (Sea of Japan). This is suggestive of comparable metal inputs from the anthropogenic sources of the cities of Nha Trang and Vladivostok (Peter the Great Bay). However, the concentrations of Pb, Ni, and Cd in algae from the coastal waters of Nha Trang Bay were lower than in macrophytes from the inshore zone of Vladivostok. The high level of pollution of sea water with Zn compounds near Nha Trang was local. The metal levels in macrophytes from background areas reflect the geochemical features of the environment. Sargassum algae from Nha Trang Bay had lower concentrations of Zn, Cd, and Ni and higher concentrations of Mn than algae from Peter the Great Bay. The background concentrations of Cu, Pb, and Fe in macrophytes from both bays were virtually the same.     

Stock assessment and management implications of golden grey mullet (Liza aurata Risso, 1810) in Iranian waters of the Caspian Sea

Recent changes in the Caspian ecosystem have caused changes in the absolute and relative abundance of the commercially important golden grey mullet (Liza aurata) in Iranian waters. In order to adjust for these changes a more rigorous management of this fishery resource is required. The present study examines the biomass of golden grey mullet during 1991–2010. Estimates of f_MSY, yield‐per‐recruit and spawning biomass‐per‐recruit are presented for various harvesting strategies of F_max, F_0.1, F_35%, and a method is proposed for estimating acceptable biological catch (ABC) that accounts for large differences in the quality and quantity of information and available data. Biomass estimates of golden grey mullet, derived from a biomass‐based cohort analysis, increased from 13 527 tonnes in 1991–1992 to 20 100 t in 2000–2001, and declined to the lowest level (11 000 t) in 2007–2008. In 2009–2010, the total biomass was estimated to be 14 400 t. The ABC was estimated at 2200 t in 2010. Golden grey mullet is vulnerable to environmental factors, which should be considered in the stock assessment and management of the fish.     

The genus Synchaeta (rotifers) in a north-western Mediterranean coastal lagoon (Etang de Thau, France): taxonomical and ecological remarks

During a survey of a north-western Mediterranean coastal lagoon, (the Etang de Thau, and at a nearby marine station, 1994–1998), six species of the genus Synchaetawere identified. The systematics of this illoricate genus is difficult and identification is virtually impossible in preserved material, although some indication may be obtained from an examination of the trophi after treatment with sodium hypochlorite. In this study, taxonomic characters (mastax, body morphology and egg size) were obtained from living material prior to preservation. We add some ecological observations: distribution of species (neither temperature nor salinity were found to be determining factors), co-existence (up to five species can co-occur) and consideration of trophic links (competition with tintinnids, copepod nauplii and cirripedes).     

Concentrations of Trace Metals in Dominant Aquatic Plants of the Lake Provala (Vojvodina, Yugoslavia)

The trace metal (Fe, Mn, Zn, Cu, Ni, Pb, Cd, Sr, and Cr) contents in the most common submerged and floating aquatic plants Ceratophyllum demersum L., Myriophyllum spicatum L., and Nymphoides flava Hill. of Provala Lake were evaluated. Considerable higher contents of iron, manganese, zinc, nickel, lead and strontium were found in submerged species than in the floating ones. The presence of cadmium and lead in plant tissues points to a certain degree of lake water pollution.