Protein differences among the Mediterranean species of the genus Spicara

Protein electrophoresis (PAGE) was used to study the three morphologically different species of Spicara (S. flexuosa, S. maena, S. smaris). Of the 28 enzymatic and additional myogenic loci, five monomorphic loci (LDH-1*, G6PD-1*, PGI-1* and two PMMs*) were species-specific markers of S. smaris with respect to S. flexuosa and S. maena. Four of the 28 enzymatic loci were polymorphic (EST-1*, GLDH*, PEPD*, PGI-2*). Discriminating genetic markers were not identified between S. flexuosa and S. maena. Genetic distance (D) as calculated by Nei's index (1978), between S. smaris v. S. maena and S. flexuosa showed a value, respectively of Z) = 0·137 and 0·141. Between S. flexuosa and S. maena the value was Z)=0-006. From the data it can be inferred that S. flexuosa and S. maena are conspecific, despite morphological differences.     

Glutathione redox system,GSH-Px activity and lipid peroxidation (LPO) levels in tadpoles of R.r.ridibunda and B.viridis

Total glutathione (t-GSH), reduced glutathione (GSH), glutathione disulphide (GSSG) levels, t-GSH/GSSG ratio, glutathione peroxidase (GSH-Px) activity and lipid peroxidation (LPO) levels were investigated during the development period of a predominantly aquatic amphibian R.r.ridibunda and a predominantly terrestrial amphibian B. viridis. While t-GSH and GSH showed a similar trend, GSSG concentration increased significantly (p<0.05) during the larval stages in R.r.ridibunda larvae. In contrast to R.r.ridibunda larvae, there was no significant (p>0.05) change between 1 and 5 weeks in the t-GSH and GSH concentrations of B. viridis. t-GSH and GSH concentrations of B. viridis larvae became sharply elevated after the fifth week, GSSG levels increased 3.25-fold during the metamorphosis. The t-GSH/GSSG ratio fluctuated and the lowest t-GSH/GSSG ratios were observed at the third week for both species. GSH-Px activities for both species increased significantly (p<0.05) during the growing period. The highest GSH-Px activities in R.r.ridibunda and B.viridis were observed at the eighth week and they were 3.45 +/- 0.17 and 4.1 +/- 0.21 IU mg(-1), respectively. The membrane LPO levels in the R.r.ridibunda and B. viridis tadpoles significantly (p<0.001) decreased from 206 +/- 10.3 to 146 +/- 7.3 and from 198 +/- 9.9 to 23 +/- 1.15 nmol MDA g(-1) w.w., respectively.     

Freezing tolerance of the European water frogs: the good, the bad, and the ugly

Survival and some physiological responses to freezing were investigated in three European water frogs (Rana lessonae, Rana ridibunda, and their hybridogen Rana esculenta). The three species exhibited different survival times during freezing (from 10 h for R. lessonae to 20 h for R. ridibunda). The time courses of percent water frozen were similar; however, because of the huge differences in body mass among species (from 10 g for Rana lessonae to nearly 100 g for Rana ridibunda), the ice mass accumulation rate varied markedly (from 0.75 +/- 0.12 to 1.43 +/- 0.11 g ice/h, respectively) and was lowest in the terrestrial hibernator Rana lessonae. The hybrid Rana esculenta exhibited an intermediate response between the two parental species; furthermore, within-species correlation existed between body mass and ice mass accumulation rates, suggesting the occurrence of subpopulations in this species (0.84 +/- 0.08 g ice/h for small R. esculenta and 1.78 +/- 0.09 g ice/h for large ones). Biochemical analyses showed accumulation of blood glucose and lactate, liver glucose (originating from glycogen), and liver alanine in Rana lessonae and Rana esculenta but not in Rana ridibunda in response to freezing. The variation of freeze tolerance between these three closely related species could bring understanding to the physiological processes involved in the evolution of freeze tolerance in vertebrates.     

The relationship between total sialic acid levels and antioxidant status in the tadpoles of Bufo viridis and Rana ridibunda ridibunda

Total sialic acid levels (TSA), antioxidant enzymes activities such as superoxide dismutase (SOD), catalase (CAT) and lipid peroxidation (LPO) levels were investigated during the developmental period in tadpoles of the predominantly terrestrial amphibian B. viridis and the predominantly aquatic amphibian R. r. ridibunda. Maximum TSA levels were observed in B. viridis and R. r. ridibunda at the fifth and third week of their development, respectively. SOD and CAT activity variations during development in B. viridis were higher than in R. r. ridibunda. Although SOD activity in B. viridis was higher than R. r. ridibunda at the eighth week, SOD activity increased 19.2-fold in R. r. ridibunda and 10.4-fold in B. viridis between the first and eighth week. CAT activity in R. r. ridibunda did not significantly change (p>0.001) until the fifth week then increased, whereas in B. viridis CAT increased after the third week. In contrast to the rise in the antioxidant enzyme activities, LPO levels tended to decrease during the developmental period. Levels of LPO showed a similar trend until the third week for both species. The minimum LPO levels in B. viridis and R. r. ridibunda were 23+/-1.2 and 146+/-7.3 nmol MDA g(-1) tissue, at the eighth week, respectively. While decreasing LPO levels correlated with increasing antioxidant enzyme activities, TSA tended to decrease after reaching a maximum point.     

A study on cholesterol content in some tissues of the Saudi frog: Rana ridibunda.

1. Cholesterol content of selected tissues in the Saudi frog Rana ridibunda was determined. 2. Total cholesterol content was higher in tissues involved in water loss, ranging from 12.22 +/- 0.28 to 40.3 +/- 0.79 mg/g. 3. In tissues not involved in water loss, total cholesterol content ranged from 2.42 +/- 0.18 to 19.30 +/- 0.39 mg/g.     

Diet composition of the Lessepsian bluespotted cornetfish Fistularia commersonii in the eastern Mediterranean

Adaptability is an important factor in defining success or failure of an introduced species. The bluespotted cornetfish, Fistularia commersonii , invaded the Mediterranean from the Red Sea and spread quickly, displaying an explosive growth pattern in the eastern and central Mediterranean. Stomach contents of the Lessepsian piscivore were studied from off the Lebanese coast in order to describe aspects of its feeding ecology in the new environment. Cornetfish of different sizes (25–112 cm L_t) and from various habitats and depths (1–40 m) were sampled over an 18-month period (May 2003 to November 2004). Only 29% of the individuals contained identifiable prey items. The diet of the invasive cornetfish comprised a large variety of prey (41 taxa), Spicara smaris and Boops boops being the most important. Comparisons among prey habitats showed that the invasive cornetfish fed preferably on schooling species living in the water column. A large diversity of prey species characterized autumn and winter seasons while S. smaris and B. boops dominated in the spring and summer. Diet did not vary significantly with predator size except for S. smaris , which was a more important prey to middle size-classes cornetfish. The invasion of F. commersonii might have an important effect on structure and population dynamics of native communities, however it seems premature to predict the potential impact on eastern Mediterranean ecosystems or fisheries.     

Food partitioning among scorpaenid fishes in Mediterranean seagrass beds

Diets of three scorpaenid fishes, Scorpaena notata, S. porcus and S. scrofa , from a Posidonia seagrass bed off Marseilles were quantitatively analysed and categorized according to the size and sex of individuals, to elucidate diel and seasonal rhythms. All three preyed on the same crustacean and fish species, but in different proportions: S. notata mostly fed on Caridae, S. porcus on brachyurans and S. scrofa on fishes. Individual size and diel period were the main factors responsible for diet variation and food partitioning that evolved according to both cyclic (temporal) and continuous (ontogenic) trends. A strong interspecific food overlap was observed in juveniles (S.L. < 50 mm), whereas intraspecific potential competition was low between juveniles and adults. Among medium and large size classes, intra- and interspecific food overlaps were high and of equal intensity. Narrower food niches at night, due to a stronger specialization on type and size of prey, diminished the intra- and interspecific potential competition during this period of maximum feeding activity. This probably allowed the high number of coexisting scorpaenid populations in Mediterranean seagrass beds. Nevertheless, microhabitat and time partitioning seemed as important as food partitioning in the structuring of fish assemblages.     

Tissue Peculiarities of Energy Metabolism Enzyme Activity and ATP Content In Black Sea Ruff Scorpaena porcus (Scorpaenidae)

Journal of Ichthyology - The activities of cytosolic oxidoreductases (malate and lactate dehydrogenases) and the level of ATP production in the hypoxic resistive tissues of Scorpaena porcus...     

Genetic diversity in mitochondrial 12S rDNA of western Palearctic water frogs (Anura, Ranidae) and implications for their systematics

The nucleotide sequence of a part of the mitochondrial 12S rRNA gene of eight western Palearctic water frog species was analysed. The results are consistent with the species status of Rana bedriagae, Rana bergeri, Rana epeirotica, Rana lessonae, Rana perezi, Rana ridibunda, Rana saharica and Rana shqiperica . The obtained DNA data suggest that lake frogs from Greece and Yugoslavia on the one hand and lake frogs from Georgia, Uzbekistan and Turkmenistan on the other hand represent two distinct species. However, it is not yet clear whether lake frogs from Georgia, Uzbekistan and Turkmenistan belong to R. ridibunda or represent a new species. The very high similarity between the analysed 12S rDNA segments of German R. ridibunda and R. lessonae confirm the finding that mtDNA of R. lessonae was transmitted into the mitochondrial gene pool of R. ridibunda probably as a result of backcrosses with the hybridogenetic hybrid R. kl. esculenta . The results of parsimony analyses speak in favour of very close phylogenetic relations between R. perezi and R. saharica ; with a high probability these species represent an adelphotaxon. Furthermore, the clades ( R. lessonae + R. shqiperica + R. bergeri ) and ( R. ridibunda + R. bedriagae ) are considered to be sister groups. According to the mt 12S rDNA data R. epeirotica seems to be more closely related to the supraspecific taxon ( R. ridibunda + R. bedriagae ) than to ( R. lessonae + R. shqiperica + R. bergeri ). Thus, it can be excluded that R. shqiperica and R. epeirotica represent sister species.     

Age and Growth of the Black Scorpionfish Scorpaena porcus Linnaeus, 1758 (Scorpaeniformes: Scorpaenidae) under Anthropogenic Pressure in the Black Sea

Journal of Ichthyology - Age structure and growth dynamics are examined for the black scorpionfish Scorpaena porcus Linnaeus, 1758, from three sites characterized by different levels of pollution:...     

Widespread unidirectional transfer of mitochondrial DNA: a case in western Palaearctic water frogs

Interspecies transfer of mitochondrial (mt) DNA is a common phenomenon in plants, invertebrates and vertebrates, normally linked with hybridization of closely related species in zones of sympatry or parapatry. In central Europe, in an area north of 48 degrees N latitude and between 8 degrees and 22 degrees E longitude, western Palaearctic water frogs show massive unidirectional introgression of mtDNA: 33.7% of 407 Rana ridibunda possessed mtDNA specific for Rana lessonae. By contrast, no R. lessonae with R. ridibunda mtDNA was observed. That R. ridibunda with introgressed mitochondrial genomes were found exclusively within the range of the hybrid Rana esculenta and that most hybrids had lessonae mtDNA (90.4% of 335 individuals investigated) is evidence that R. esculenta serves as a vehicle for transfer of lessonae mtDNA into R. ridibunda. Such introgression has occurred several times independently. The abundance and wide distribution of individuals with introgressed mitochondrial genomes show that R. lessonae mt genomes work successfully in a R. ridibunda chromosomal background despite their high sequence divergence from R. ridibunda mtDNAs (14.2-15.2% in the ND2/ND3 genes). Greater effectiveness of enzymes encoded by R. lessonae mtDNA may be advantageous to individuals of R. ridibunda and probably R. esculenta in the northern parts of their ranges.     

Body Size,Age Structure,Growth, and Maturation of Black Scorpionfish Scorpaena porcus (Scorpaenidae) from Southwestern Crimea (Black Sea)

Journal of Ichthyology - The body size and age structure, as well as the features of growth and sexual maturation, of black scorpionfish Scorpaena porcus from the coastal waters of southwestern...     

A skeletochronological study of age, growth and longevity in a population of the frog Rana ridibunda from southern Europe

Age at sexual maturity and longevity in a population of Rana ridibunda from north-eastern Greece were studied by skeletochronology performed on the phalanges. Analysis of the age structure was based on counting the lines of arrested growth (LAGs). Sexual maturity for both sexes arises during the first year or after the first hibernation. Ages ranged from 1 to 5 years (mean=2.96) among 52 males and from 1 to 5 years (mean=3.73) among 56 females. The mean snout-vent length was 69.03+/-12.6mm in males and 82.38+/-13.27 mm in females. The difference between the sexes in age and size was significant. Growth of individuals was fitted on? The von Bertalanffy model. The growth coefficient (K) was 0.57 in males and 0.54 in females, mainly due to faster male growth between metamorphosis and maturation.     

Mitochondrial DNA reveals formation of nonhybrid frogs by natural matings between hemiclonal hybrids.

The European water frog Rana esculenta (RL), a natural hybrid between R. ridibunda (RR) and R. lessonae (LL), reproduces by hybridogenesis: haploid gametes usually contain an intact chromosome set of R. ridibunda (R); the lessonae nuclear genome (L) is lost from the germ line. Hybridity is restored in the next generation, via fertilization by syntopic R. lessonae. Matings between two hybrids (RL x RL) usually give inviable R. ridibunda (RR) progeny. The adult R. ridibunda subpopulation of Trubeschloo, a gravel pit in northern Switzerland, consists only of females. Fragment patterns for mitochondrial DNA (mtDNA) of these R. ridibunda were identical with those of syntopic R. esculenta and of local populations of R. lessonae; they differed from the patterns in eastern European populations of R. lessonae and of R. ridibunda mtDNAs (3.7% and 9.3% estimated sequence divergence, respectively). In contrast, mtDNAs of two R. ridibunda from an introduced Swiss population with both sexes, although different (2.7% divergence) from each other, were typical R. ridibunda rather than R. lessonae mtDNAs. These data, together with unisexuality, demonstrate conclusively that the all-female R. ridibunda population at Trubeschloo originated from matings between two R. esculenta. The formation of independently reproducing R. ridibunda populations via such hybrid x hybrid matings is precluded because progeny of these matings are unisexual. Recombination in the regenerated fertile R. ridibunda females, followed by matings with R. lessonae, nevertheless provides a mechanism for meiotic reshuffling of genetic material in ridibunda haplotypes that is not typically available in hemiclonal lineages.     

Gametogenesis of intergroup hybrids of hemiclonal frogs

European water frog hybrids Rana esculenta (R. ridibundaxR. lessonae) reproduce hemiclonally, by hybridogenesis: in the germ line they exclude the genome of one parental species and produce haploid gametes with an unrecombined genome of the other parental species. In the widespread L-E population system, both sexes of hybrids (E) coexist with R. lessonae (L). They exclude the lessonae genome and produce ridibunda gametes. In the R-E system, hybrid males coexist with R. ridibunda (R); they exclude either their ridibunda or their lessonae genome and produce sperm with a lessonae or with a ridibunda genome or a mixture of both kinds of sperm. We examined 13 male offspring, 12 of which were from crosses between L-E system and R-E system frogs. All were somatically hybrid. With one exception, they excluded the lessonae genome in the germ line and subsequently endoreduplicated the ridibunda genome. Spermatogonial metaphases contained a haploid or a diploid number of ridibunda chromosomes, identified through in situ hybridization to a satellite DNA marker, and by spermatocyte I metaphases containing a haploid number of ridibunda bivalents. The exception, an F1 hybrid between L-E system R. lessonae and R-E system R. ridibunda, was not hybridogenetic, showed no genome exclusion, and evidenced a disturbed gametogenesis resulting from the combination of two heterospecific genomes. None of the hybridogenetic hybrids showed any cell lines excluding the ridibunda genome, the pattern most frequent in hybrids of the R-E system, unique to that system, and essential for its persistence. A particular combination of R-E system lessonae and R-E system ridibunda genomes seems necessary to induce the R-E system type of hemiclonal gametogenesis.     

Non-hybrid offspring from matings between hemiclonal hybrid waterfrogs suggest occasional recombination between clonal genomes

The hemiclonal waterfrog Rana esculenta , a hybrid between R. ridibunda and R. lessonae , eliminates the lessonae genome from the germline and clonally transmits the ridibunda genome (hybridogenesis). Such genomes are prone to accumulate deleterious mutations, which may explain why offspring from matings between hybrids are typically inviable. Here I present field data from a population for which experimental crossings showed that some R. esculenta pairs produce viable R. ridibunda offspring. I demonstrate: (1) that R. ridibunda metamorphs are also produced and survive under natural conditions; (2) that their genotypes are consistent with combinations of clonal ridibunda genomes found in hybrids; and (3) that all R. ridibunda are female. These females possibly recombine the clonal genomes they inherited and, upon mating with syntopic R. lessonae , produce new hemiclones with novel combinations of alleles. Hence, occasional recombination between otherwise clonal ridibunda genomes seems plausible and may provide an escape from the evolutionary dead end they were proposed to be trapped in.     

Catalase enzymatic activity and electrophoretic patterns in adult amphibians--a comparative study

Catalase electrophoretic patterns and enzymatic activities were measured in four organs of two anuran species, Rana ridibunda perezii and Discoglossus pictus. The D. pictus enzyme appeared as two distinguishable bands, whereas R. ridibunda catalase was monomorphic. Electrophoretic mobility of the major D. pictus catalase band was greater than that of R. ridibunda. Enzymes from both species showed slower mobility than that from bovine liver. Catalase activities did not show significant differences according to sex in any of the organs tested in R. ridibunda. Enzyme activities were similar in liver, kidney and brain when both species were compared. Only the heart showed much higher activity in D. pictus than in R. ridibunda. The catalase activity levels followed the order: liver greater than kidney greater than heart in both species. The heart showed higher activity than the brain in D. pictus but not in R. ridibunda.     

Survival and metabolic responses to freezing by the water frog (Rana ridibunda)

We studied the ability of the marsh frog Rana ridibunda to survive freezing exposure and the associated subsequent metabolic variations. This species that typically overwinters under water tolerates the conversion of 55% of its body water into ice. This ice content is attained after a few hours (between 8 and 36 hours depending on the mass of the individual and the environmental temperature) but death occurs at greater than 58% ice. Freezing stimulated a significant increase in blood carnitine and trimethylamine levels (respectively 4.5+/-2.5 and 0.5+/-0.2 micromol.l(-1) for controls versus 27.0+/-18.9 and 3.6+/-4.1 micromol.l(-1) after thawing) but these increases had no significant effect on plasma osmolality which was unchanged between control and freeze exposed frogs (252.6+/-20.3 versus 240.2+/-25.0 mOsmol.l(-1), respectively). Freezing also induced a significant dehydration of heart, liver and muscles (respectively 4.2, 3.2 and 2.8%) but the observed levels are low compared to values found in highly freeze tolerant species. This species could be classified as "partially freeze tolerant" enduring the transformation of a significant part of its body water into ice but not the completion of the exotherm. The existence of freeze tolerance in an aquatic hibernator that does not accumulate cryoprotectant, exhibiting low organ dehydration after freezing and low hypoxia tolerance, raises the possibility that a tolerance of nearly 60% ice within the body is common among anurans.     

Oxygen consumption of a terrestrial toad (Bufo viridis) and semi-aquatic frog (Rana ridibunda)

1. Oxygen consumption was measured before and after dehydration at different ambient temperatures (Ta) in the terrestrial toad Bufo viridis and the semi-aquatic frog Rana ridibunda. 2. The metabolic rates at Tas between 14 and 27 degrees C were almost the same for R. ridibunda and B. viridis. 3. The metabolic rate at higher Tas (between 27 and 36 degrees C) was higher in R. ridibunda than in B. viridis. This situation was found before and after dehydration. 4. A similar situation was found with CO2 production, which was higher at high Tas in R. ridibunda compared with B. viridis.     

Localization and characterization of atrial natriuretic factor (ANF)-like peptide in the frog atrium

The distribution of ANF was studied in the heart of the frog (Rana ridibunda) using indirect immunofluorescence. ANF-like immunoreactivity was localized mainly in the right and left atrium, most of cardiocytes being intensively labelled. At the electron microscopic level, all secretory granules present in atrial cardiocytes contained ANF immunoreactive material. Using a specific radioimmunoassay, we found higher concentrations of ANF in the left atrium (208 +/- 25 ng/mg protein) than in the right atrium (120 +/- 16 ng/mg protein) whilst in the rat, the right atrium contains the highest ANF concentration. The concentration of ANF in the ventricle was 10 times lower than in the whole atrium (32 +/- 4 ng/mg protein). Sephadex G-50 gel filtration of atrial extracts showed that ANF-like immunoreactivity eluted in three peaks. Most of the immunoreactivity corresponded to high molecular weight material eluting at the void volume while 20% of the material co-eluted with synthetic (Arg 101-Tyr 126) ANF. These results indicate that frog cardiocytes synthetize a peptide which is immunologically and biochemically related to mammalian ANF.