Characterization of eight microsatellite markers in the white sea bream, Diplodus sargus (Teleostei, Sparidae)

The white sea bream, Diplodus sargus (Teleostei, Sparidae), is a species with a high commercial importance in Mediterranean aquaculture. There is currently little information available about the genetic characteristics of cultured populations. In this survey, we have developed eight polymorphic microsatellites for the white sea bream using an enriched genome library protocol. All of them were polymorphic in the 67 individuals tested, 32 of which were wild specimens, and 35 were individuals from a captive F(1) broodstock. These markers can potentially be useful tools for use in population genetic studies.     

Sperm motility of the marine teleosts Boops boops, Diplodus sargus, Mullus barbatus and Trachurus mediterraneus

The spermatozoa of Boops boops, Diplodus sargus, Mullus barbatus, and Trachurus mediterraneus were motile in sea water, and in electrolyte solutions (NaCl) and non-electrolyte solutions (glucose) with an osmolality of 600–1000 mosmol kg^?1. Their mean motility rate 10 s after initiation was about 80%, while about 10% of the motile spermatozoa moved non-linearly, 45% linearly, and 45% circularly. The average path swimming velocity was significantly higher in M. barbatus (about 90 μm s^?1) than in the other species (70 μm s^?1). The number of motile spermatozoa decreased to 0% within 50 s after initiation of motility in T. mediterraneus, within 90 s in M. barbatus . In B. boops and D. sargus about 90% of the spermatozoa stopped movement during the first 90 s of the motility period, while the rest remained motile for 2–3 h. Motility of B. boops and D. sargus spermatozoa was reversibly suppressed in the seminal plasma, and in electrolyte and non-electrolyte solutions of 100–200 mosmol kg^?1. The trigger for motility activation was hyperosmolality (700–1000 mosmol kg^?1). Motility of M. barbatus and T. mediterraneus sperm was only partly suppressed in the seminal plasma since freshly collected semen contained about 25–50% locally motile spermatozoa. When sperm was activated immediately after collection with electrolyte and non-electrolyte solutions of 700–1000 mosmol kg^?1 spermatozoa moved progressively. The motility of those spermatozoa which had not yet been motile after collection was completely and reversibly suppressed in M. barbatus at osmolalities of 1200 mosmol kg^?1, and at osmolalities of 100–200 mosmol kg^?1 in T. mediterraneus . Therefore two triggers were necessary for initiation of motility. The nature of the first trigger was uncertain, the second trigger was a switch to hypoosmolality in M. barbatus and to hyperosmolality in T. mediterraneus . The sperm organisation of B. boops, D. sargus, M. barbatus and T. mediterraneus revealed species-specific parameters which could not be related with the sperm motility behaviour.     

Isolation and characterization of nine polymorphic microsatellite markers in the two‐banded sea bream (Diplodus vulgaris) and cross‐species amplification in the white sea bream (Diplodus sargus) and the saddled bream (Oblada melanura)

We have developed nine new microsatellite markers for the two‐banded sea bream (Diplodus vulgaris) from an enriched genome library protocol. All these loci are polymorphic, with mean allelic diversity of 13 (range 5 –21), and expected and observed heterozygosities from 0.641 to 0.932 and 0.428 to 0.914, respectively. Cross‐species tests in two close‐related species of the genus Diplodus (D. sargus and O. melanura) revealed successful amplifications at 8 out of 9 loci, with mean allele number of 4.75 (range 2–8) and 5.50 (range 3 –10), respectively. These results are consistent with the close phylogenetic relationships between the three species, indicating this set of primers might prove useful for studying the levels of genetic diversity and population differentiation in these three species and in other phylogenetically close species of the genus Diplodus and Sparus.     

Characterization of mitotic chromosomes of four species of the genus Diplodus: karyotypes and chromosomal nucleolar organizer region phenotypes

Karyotypes have been described in four Mediterranean species of the genus Diplodus (Teleostei, Sparidae), D. vulgaris, D. puntazzo, D. sargus and D. annularis . Chromosomes were mainly acrocentric in all but D. vulgaris , where certain chromosome pairs were subtelocentric. A remarkable intraspecific heteromorphism in the number of NOR-bearing chromosomes along with a substantial interspecific variability in position of chromosomal Ag signals have been encountered. The presumed origin of multiple NOR-bearing chromosomes in Diplodus species and variation of the NOR location is discussed.     

Further studies on the sexuality of the hermaphroditic teleost Diplodus sargus, with particular reference to protandrous sex inversion

Histological events associated with the process of sex inversion are described in the protandrous teleost Diplodus sargus reared in captivity. This species possesses typical sparid ovotestes in which the testis and ovary occur in separate zones. After spawning, the testicular tissue within the bisexual gonad undergoes regressive changes such as spermatogonial degeneration, deposition of yellowish pigment and proliferation of connective cells and fibres. At the same time ovarian tissue begins to develop. Transitional individuals were 26–7% of examined fish, while the other 73–3% were functional males.     

Morphology of the tongue dorsal surface in white sea bream (Diplodus sargus sargus)

In the present study, the tongue dorsal surface of the white sea bream Diplodus sargus sargus (Linnaeus, 1758) (teleosts, Sparidae) was studied, to give a support to the knowledge of the anatomical characteristics of the oral cavity of a species with a future potential use in aquaculture. The feeding habits in captivity are one of the critical steps in the species of commercial interest, strictly related to the morphological characteristics of the oropharyngeal cavity. This study was undertaken, using light and scanning electron microscopy, to analyse the morphology of the dorsal tongue surface to show whether relationships are present between the anatomy and the nutritional habits and choices of this farmed species. Three zones, an apex, a body and a root, can be clearly distinguished, with a pouch partially covering the apex. In the pouch, cylindroid and mucosal ridges were observed. Along the whole tongue surface, from the apex to the root, on the medial and lateral parts, many papillae are present, with a fungiform, cylindroid and cone‐like aspect. Taste buds are showed on the dorsal surface of some papillae.     

Genetic differentiation and gene flow of two sparidae subspecies, Diplodus sargus sargus and Diplodus sargus cadenati in Atlantic and south-west Mediterranean populations

A total of nine enzymes coded by 14 loci were assayed for each of six populations (from the north-eastern Atlantic and the Mediterranean) of two sea bream subspecies ( Diplodus sargus sargus and Diplodus sargus cadenati ). Diagnostic alleles were observed for each subspecies, although there were several common alleles. Estimates of variance in allele frequencies among samples ( F _ST) revealed significant differences ( P  < 0.05) among both subspecies. Genetic divergence was found between Atlantic and Mediterranean samples: values for genetic distances were higher than 0.163. Furthermore, D. sargus cadenati populations displayed a higher mean weight and length than D. sargus sargus populations and significant differences in growth were found among subspecies and populations. These results are discussed in terms of levels of gene flow and its respective relationships with water circulation in the Strait of Gibraltar and geological events.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 89 , 705–717.     

Parasites in marine protected areas: success and specificity of monogeneans

The effect of a marine protected area on the Lamellodiscus spp. monogenean community was tested by comparing the communities of parasites of Diplodus sargus inside and outside of the area. A total of 104 D. sargus were dissected harbouring 1280 monogeneans from the genus Lamellodiscus and belonging to 11 species. No modification in the global parasite community linked with the protection of the host populations was revealed. The most abundant and less specific parasite species, Lamellodiscus elegans , however, increased its abundance in the protected area. A significant relationship was found between parasite host range and the percentage of infected hosts. A significant relationship also occurred between epidemiological and genetic distances for the parasite species found. The results are discussed in term of parasite success and specificity and the importance of taking into account parasitism in the biological conservation of hosts.     

Reproductive biology and recruitment of the white sea bream in the Azores

The life history of the white sea bream Diplodus sargus in the Azores showed a pattern consistent with digynic hermaphroditism achieving sexual maturity during the second year of life, at 16·7 cm L _T. Spawning occurred from March to June at temperatures between 15 and 17° C and the onset and duration of spawning season in the sea bream appeared to be influenced by sea water temperatures. As latitude decreased, both in the northern and southern hemispheres, the spawning season of D. sargus populations started earlier and extended longer, highlighting the potential importance of temperature to the onset and duration of reproduction in this species. Settlement took place from late May to July, and settlers remained in the nursery area for c . 2·5 months. Emigration from the nursery area to join shoals of juveniles occurred from late July to September.     

Genetic differentiation of white sea bream within the Lion's Gulf and the Ligurian Sea (Mediterranean Sea)

An allozymic study was conducted on 190 individuals of white sea bream, Diplodus sargus sampled on five locations throughout the Lion's Gulf and the Ligurian Sea (Mediterranean Sea), in order to identify genetic structure. Electrophoretic surveys carried out on muscle and liver tissues identified 25 loci of which 12 were polymorphic ( P 0.95). G -test analysis shows significant differences on allelic frequencies between the five stations at six loci. Examination of the spatial structure was performed using Nei's distances and F statistics, and indicated significant genetic differences between three groups. A group which clustered Blanes (Spain), Marseille (France) and Livorno (Italy) where the absence of genetic difference can be explained by migration of larvae and adults along a coastal 'continuum'. The Elba sample (Italy) shows genetic divergence from other samples and this difference may result from isolation due to limited migration of larvae and adults. Banyuls (France), differs from all other stations. Several hypotheses are proposed to explain genetic patterns including local current systems, larval dispersal, geographic isolation and historical effects, and variation in the size classes of sampled individuals between sites.     

Structure of the lepidopteran proboscis in relation to feeding guild

Most butterflies and moths (Lepidoptera) use modified mouthparts, the proboscis, to acquire fluids. We quantified the proboscis architecture of five butterfly species in three families to test the hypothesis that proboscis structure relates to feeding guild. We used scanning electron microscopy to elucidate the fine structure of the proboscis of both sexes and to quantify dimensions, cuticular patterns, and the shapes and sizes of sensilla and dorsal legulae. Sexual dimorphism was not detected in the proboscis structure of any species. A hierarchical clustering analysis of overall proboscis architecture reflected lepidopteran phylogeny, but did not produce a distinct group of flower visitors or of puddle visitors within the flower visitors. Specific characters of the proboscis, nonetheless, can indicate flower and nonflower visitors, such as the configuration of sensilla styloconica, width of the lower branches of dorsal legulae, presence or absence of dorsal legulae at the extreme apex, and degree of proboscis tapering. We suggest that the overall proboscis architecture of Lepidoptera reflects a universal structural organization that promotes fluid uptake from droplets and films. On top of this fundamental structural organization, we suggest that the diversity of floral structure has selected for structural adaptations that facilitate entry of the proboscis into floral tubes. J. Morphol. 277:167–182, 2016. © 2015 Wiley Periodicals, Inc.     

Aerial and aquatic feeding in the silver arawana,Osteoglossum bicirrhosum

Synopsis The silver arawana, Osteoglossum bicirrhosum, hunts along shorelines and within flooded forests in the Amazon River basin and supplements its limited consumption of aquatic vertebrates by leaping from the water to obtain terrestrial and arboreal prey. We offered O. bicirrhosum prey both suspended above and submerged below the surface of the water. From high-speed digital recordings, we measured kinematic variables associated with the jaws, cranium, pectoral fins, and body during orientation and prey capture. Aquatic and aerial feeding events were kinematically distinct, with aerial events generally involving faster, larger movements and a distinct delay in the onset of lower jaw depression until the head had left the water. The comparatively large gape during leaping may facilitate prey capture by overcoming variability in the apparent position of the prey due to refraction, while the delayed onset of mouth opening may serve to reduce the effects of drag. This distinctive leaping behaviour allows exploitation of the terrestrial prey base, especially during seasonal inundation of the Amazon River basin when the aquatic food base is widely dispersed.     

The structure of the buccal cavity and pharynx in relation to the method of feeding of Reighardia sternae Diesing 1864 (Pentastomida)

The buccal complex of the haematophagous pentastomid Reighardia sternae has been described. It consists of a buccal capsule containing a prominent oral papilla communicating with a heavily chitinized pharynx which is crescentic in cross section. The chitinous skeleton of the buccal apparatus provides a framework for the attachment of various muscle systems, the contractions of which have been related to the mode of operation of the oral papilla and pharnyx during the feeding process. Particular emphasis was placed on the possible function of the oral papilla in the initial rupture of a blood capillary, and on the pumping action of the pharynx during the ingestion of the liberated blood.     

A quantitative and histochemical study on melano-macrophage centres in the spleen of the teleost fish Diplodus annularis L.

The incidence and histochemical features of melano-macrophage centres in the spleen of the teleost fish D. annularis were studied with respect to starved and fed fish. Tissue catabolism following complete starvation appears to induce formation of new centres containing melanin and lipofuscin pigments. However, a change in the amount of melano-macrophages was also recorded in fed fish, suggesting that some other factor(s), internal to fish, may affect the presence of such structures within the spleen of D. annularis .     

Validation of daily increment formation in otoliths for three Diplodus species in the Mediterranean sea

The efficacy of two fluorochromes, chlorhydrate of tetracycline (CHTC) and alizarin complexone (ALC), to induce a label on the otoliths of juvenile sparid fishes by immersion techniques was tested in different experimental conditions. CHTC did not mark otoliths in natural sea water and was toxic in divalent cation-free sea water. Immersing fish in a 50-mg 1⁻¹ ALC natural seawater solution for 24 h induced a well-defined mark on the otoliths and had no effect on survival. A daily periodicity of increment formation on otoliths was observed in captivity for Diplodus vulgaris and D. puntazzo , and was conserved in natural environment for D. sargus . The frequency of increment deposition did not vary with the age of juvenile fishes. Thus, otolith microstructure analysis will be a reliable method to give age estimates in these three sparid species during their juvenile life.     

Kinematics of the pharyngeal jaws during feeding in Oreochromis niloticus (Pisces,Perciformes)

Cichlids possess a complex pharyngeal jaw apparatus, the osteological components of which are two upper pharyngeal jaws, articulating with the neurocranial base, and a single lower pharyngeal jaw. Quantitative cinera-diography revealed that pharyngeal food processing in Oreochromis niloticus involves transport, mastication, and swallowing, effected by cyclical pharyngeal jaw movements. Transport and swallowing occur by simultaneous retractions of both upper pharyngeal jaws. Food reduction (mastication) is effected by lower jaw elevation (compression) and protraction (shear) during upper jaw retraction. Each movement cycle contains a transport, reduction, and swallowing component, although their relative importance may vary within a feeding sequence. The upper and lower pharyngeal jaws show opposite anteroposterior movements during most of the cycle. Variations in the amplitudes and the durations of the different movement components reflect the consistency and the size of the food.     

Implication of the feeding limb morphology for herbivorous feeding in some freshwater cyclopoid copepods

1. The mouthparts of five species of adult planktonic cyclopoid copepods (Cyclops vicinus, C. abyssorum, Acanthocyclops robustus, Mesocyclops leuckarti and Thermocyclopscrassus), in particular the distance between setae and setules of the maxilliped (which can indicate the ability to retain small particles), were compared using electron and light microscopy. 2. The mesh‐sizes of the food‐collection grid formed by these setae and setules ranged between 4.6 and 13.2 μm; the area covered by the grid ranged between 6000 and 32 000 μm². 3. Mesh‐size was not simply correlated with body size. Cyclops abyssorum and M. leuckarti have the coarsest meshes and T. crassus the finest, while C. vicinus and A. robustus were intermediate. 4. The results suggest that cyclopoid copepods are able to retain particles in the size range of nanoplankton and that differences in mesh‐sizes between species may explain differences in the ability to subsist and reproduce on a diet of small algae.     

Shallow and deep lunge feeding of humpback whales in fjords of the West Antarctic Peninsula

Humpback whales (Megaptera novaeangliae) belong to the class of marine mammals known as rorquals that feed through extraordinarily energetic lunges during which they engulf large volumes of water equal to as much as 70% of their body mass. To understand the kinematics of humpback lunge feeding, we attached high‐resolution digital recording tags incorporating accelerometers, magnetometers, pressure and sound recording to whales feeding on euphausiids in fjords of the West Antarctic Peninsula. Instances of near vertical lunges gave us the unique opportunity to use the signal from the accelerometer to obtain a fine scale record of the body accelerations involved in lunging. We found that lunges contain extreme accelerations reaching 2.5 m/s² in certain instances, which are then followed by decelerations. When animals are intensively feeding the inter‐lunge interval is similar for both deep and shallow lunges suggesting a biomechanical constraint on lunges. However, the number of lunges per dive varies from one for shallow feeding (<25 m) to a median of six for deeper dives. Different feeding patterns were evident in the kinematic record, for deep and shallow feeding bouts with the much greater mean turn rates occurring in shallow feeding.     

Genetic differentiation of Diplodus sargus (Pisces: Sparidae) populations in the south-west Mediterranean

Allozyme analysis of tissue samples of 1249 white sea bream Diplodus sargus from five localities of the south-west Mediterranean revealed a high degree of genetic polymorphism. The observed heterozygosity ranged from 0.4182 (Cape of Palos) to 0.3138 (Tabarca). Several populations were characterized by unique alleles. Examination of the spatial structure was performed using Nei's distances and F- statistics, and indicated genetic differences between groups. One group, which clustered Tabarca and Guardamar, could be explained by the small geographical distance between them. Mazarrón and Cape of Palos samples showed genetic divergence from other samples (Guardamar, Tabarca and Águilas) and this difference may be as a result of local current systems and larval dispersal.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 82 , 249–261.