Field mortality estimates of anchovy larvae, Engraulis encrasicolus, in the western Mediterranean

Eggs and larvae of anchovy were obtained from plankton collections made along the Catalan coast (north-western Mediterranean) from 1983 to 1985 in order to determine spawning seasons and areas and other aspects of its life history. Previous studies have shown the existence of two main spawning areas, to the north and south of the Catalan coast, respectively. The northern one is characterized by a shorter spawning period related with the thermal cycle.
Mortality rates of larvae aged 4.9-15 days were calculated from the peak spawning month (June) of the three years, separately by spawning areas. Data on abundance by length classes were adjusted for escape and net avoidance and for duration of growth through a size class as derived from otolith readings. Mortality rates ranged from 0.17 to 0.58. Mortality was higher in 1983 than in 1984 and 1985, coinciding with a high production of anchovy eggs in that year. Mortality at the northern spawning area was lower than at the southern one.     

Mitochondrial DNA reveals a mosaic pattern of phylogeographical structure in Atlantic and Mediterranean populations of anchovy (Engraulis encrasicolus)

This study extends the geographic coverage of a previous study of mitochondrial DNA restriction fragment length polymorphism in European anchovy. Both studies together include 24 samples representing 17 localities extending from the Black Sea, through the Mediterranean Sea to the eastern Atlantic as far south as Dakar, Senegal. Eighty-eight haplotypes define two clades (A and B) separated by 3.2% sequence divergence. Clade A has a star-like genealogy indicative of a recent population expansion. Clade B has a more complex genealogy, consisting of several haplotypes at intermediate frequencies. The distributions of these clades consist of a mosaic with abrupt changes between some areas and gradients between other areas. Clade A predominates the Black and Aegean seas, but is present throughout the Mediterranean. Unexpectedly, new data show that clade A is also at a high frequency in the Atlantic, from Portugal to at least Senegal. Overall, the level of genetic differentiation among populations is high (F(ST)=0.148, p<0.0001), with the greatest differences between basins. AMOVA reveals four main geographical groups: Atlantic, central Mediterranean, Aegean Sea, and Black Sea. Mismatch distribution clearly indicates historical bottleneck and population expansion for clade A, while for clade B such evidence is equivocal. This difference may reflect a range expansion for both clades, but with higher gene flow (Nm values) between demes for clade A. Both contemporary and historical processes are important in shaping the complex genetic population structure of European anchovy.     

Diet composition and feeding of European anchovy Engraulis encrasicolus in Kiel Bight,western Baltic Sea

Diet composition of the expanding southern species European anchovy Engraulis encrasicolus in the western Baltic Sea was investigated. Results revealed an interesting case of bentho‐pelagic coupling with potential implications for local fish species through competition for food resources.     

Interannual variability and intraannual stability of the otolith shape in European anchovy Engraulis encrasicolus (L.) in the Bay of Biscay

In this study 1047 samples of European anchovy Engraulis encrasicolus caught in 2001, 2002 and 2003 in different areas of the Bay of Biscay were examined using otolith shape analysis. For the years 2001 and 2003, 1 year-old individuals were dominant, whereas for the year 2002 they were less common; in contrast 2 year-old individuals represented 74% of the total individuals, suggesting that the fisheries in 2002 were mainly supported by the strong recruitment of 2000. The classification success of the discriminant analysis indicated a strong separation between year groups ( P < 0·001), overall, 98% of individuals were correctly classified. Results from both jackknife and Cohen's kappa procedures confirmed the high rates of classification success obtained by the discriminant analysis (99 and 97%, respectively). Stability in the intraannual shape analysis leads to the idea that individuals were affected by the same intraannual environmental conditions in the Bay of Biscay. Variability in the interannual shape analysis could indicate that the spawning population is composed of European anchovy from different origins every year. In general differences observed suggested that the European anchovy in the Bay of Biscay were members of three or more different communities or entities.     

Influence of environmental variability on anchovy early life stages (Engraulis encrasicolus) in two different areas of the Central Mediterranean Sea

The survival of early stages of small pelagic fish species (e.g. Engraulis encrasicolus) is highly dependent on environmental conditions in both spawning and nursery areas. Knowing the relationship between the mortality rates of the early stages and the environment may help to study and model recruitment fluctuations. During the summer of 2006, two consecutive oceanographic cruises were carried out in the Central Mediterranean sea (CMED) in two different areas: the western Libyan waters and the Sicilian?CMaltese waters. For the first time a nearly synoptic comparison between the two border areas of the CMED is performed. In spite of a higher overall egg density in the Sicilian?CMaltese waters, there was a higher density of anchovy larvae in Libyan waters. The comparison between the oceanographic datasets singled out different circulation patterns and different characteristics of water masses, which helped to explain the differences in density of the spawning products in the two areas. A Lagrangian transport model was used to evaluate the effects of major oceanographic features on offshore egg and larval transport. The results of the model simulations and the nutritional conditions, as indicated by lipid, carbohydrate and protein contents, support the hypothesis that the western Libyan waters may represent a more favourable nursery ground compared to the Sicilian?CMaltese waters in terms of environmental conditions and food availability.     

Intraretinal variability and specialization of cones in Japanese anchovy (Engraulis japonicus,Engraulidae)

The retina of anchovies is characterized by an unusual arrangement and ultrastructure of cones. In the retina of Japanese anchovies, Engraulis japonicus, three types of cones are distributed into rows. The nasal, central, temporal, and ventro‐temporal regions of the retina were occupied exclusively by the long and short cones. Triple cones, made up of two lateral components and one smaller central component, were found only in the dorsal and ventro‐nasal retinal regions. In the outer segments of all short and long cones from the ventro‐temporal region, the lamellae were oriented along the cell axis and were perpendicular to the lamellae in the long cones, providing a morphological basis for the detection of polarization. This lamellar orientation is unique to all vertebrates. The cones were examined with respect to regional differentiation in their size and spectral properties via light microscopy, transmission electron microscopy, and microspectrophotometry. Various dimensions of cones were measured in preparations of isolated cells. The cones from the ventro‐temporal region had different dimensions than cones of the same type located in other retinal regions. Triple cones from the dorsal region were significantly larger than triple cones from the ventro‐nasal region. The spectral absorbance of the lateral components of triple cones in the ventro‐nasal retina was identical to the absorbance of all long and short cones from the ventro‐temporal region. These are shifted to shorter wavelengths relative to the absorbance of the lateral components of the triple cones located in the dorsal retina. Thus, the retina of the Japanese anchovy shows some features of regional specialization common in other fishes that improves spatial resolution for the upwards and forwards visual axis and provides spectral tuning in downwelling light environment. That results from the differentiation of cone types by size and by different spectral sensitivity of various retinal areas. J. Morphol. 277:472–481, 2016. © 2016 Wiley Periodicals, Inc.     

Late Pleistocene divergence and subsequent population expansion of two closely related fish species, Japanese anchovy (Engraulis japonicus) and Australian anchovy (Engraulis australis)

Climatic oscillations during the Pleistocene ice ages produced great changes in species' geographical distribution and abundance, which could be expected to have genetic consequences. Living in the temperate upwelling zones of the northwestern Pacific, Japanese anchovy (Engraulis japonicus) might have been affected by these severe climatic oscillations. To investigate the effects of Pleistocene climatic changes on the evolution in Japanese anchovy, fragments of 522 bp at the 5' end of mitochondrial DNA control region were sequenced for 241 individuals from 13 localities and 37 individuals of Australian anchovy. Japanese anchovy and Australian anchovy are reciprocally monophyletic and a late Pleistocene transequatorial divergence between the two species was indicated. High levels of haplotype diversity (>0.99) were found for all samples, indicating a high level of genetic diversity. Analyses of molecular variance and the conventional population statistic F(ST) revealed no significant genetic structure throughout the range of Japanese anchovy. Both mismatch distribution analyses and neutrality tests suggested a late Pleistocene population expansion for both Japanese anchovy (79,000-317,000 years ago) and Australian anchovy (45,000-178,000 years ago).     

Lipid biomarkers and trophic linkages between phytoplankton, zooplankton and anchovy (Engraulis encrasicolus) larvae in the NW Mediterranean

Identification and quantification of the main fatty acids inphytoplankton, zooplankton and Engraulis encrasicolus larvaewere used to study the relationship among the different trophiclevels. Three northwestern Mediterranean sea areas were studiedas representative of potentially heterogeneous environments.HPLC pigment analysis was performed to assess the contributionof different phytoplankton groups to total chlorophyll biomass.In spite of the physical variability, a homogeneous patternin phytoplankton composition among areas was found, with thePrymnesiophyceae representing more than half of the phytoplanktonchlorophyll biomass. This homogeneous spatial pattern was alsoreflected in the phytoplankton fatty acid proportions. Thus,significant amount of 14:0, 18:1(n-9) and 18:4(n-3) could berelated to the dominance of the prymnesiophytes; the low proportionof fatty acid markers of diatoms and dinoflagellates agreedwith the low abundances of those phytoplankton groups. Zooplanktonfatty acids also showed homogeneous proportions in the studiedareas, with a preferential accumulation of 16:1(n-7) and 20:5(n-3),and 22:6(n-3). This observation may indicate a preferentialgrazing on diatoms and dinoflagellates. Anchovy larvae displayeddiffering fatty acids contributions related to size. Large larvaecontained a higher proportion of polyunsaturated fatty acid(PUFA). Small larvae showed a high percentage of 18:1(n-9) and18:4(n-3) fatty acids, considered Prymnesiophyceae biomarkers.These results suggest an additional food resource for the anchovythat is complementary to a zooplankton diet, but probably ofprotozoan origin (i.e. microzooplankton). Significant logarithmicrelationships were found between dry mass and 20:5(n-3) and22:6(n-3) fatty acid proportions in E. encrasicolus larvae.These PUFA are considered essential for the fish-larvae development.     

Microsatellite DNA polymorphism confirms reproductive isolation and reveals differences in population genetic structure of cryptic pipistrelle bat species

Previous studies have indicated that the common European pipistrelle bat ( Pipistrellus pipistrellus ) comprises two cryptic species, P. pipistrellus and Pipistrellus pygmaeus , which differ in echolocation call frequency and mitochondrial DNA sequence. However, levels of divergence based on nuclear markers have not been examined, and hence the potential for male-mediated gene flow between the species cannot be discounted. Moreover, little is known about population structure and migration patterns in either species. Here, we describe the use of microsatellites to investigate nuclear DNA differentiation between, and the pattern of population genetic structure within, the two cryptic pipistrelle species. In total, 1300 individuals from 82 maternity colonies were sampled across the British Isles and Continental Europe. We show, using multivariate analyses, that colonies of the same species are generally genetically more similar to each other than to those from the other species regardless of geographical location. Our findings support the hypothesis that the species are reproductively isolated. Significant patterns of genetic isolation by distance were identified in both species, indicating that mating may occur before any long-distance autumnal migration. The presence of a sea channel does not confer higher levels of genetic differentiation among colonies over and above distance alone in either species. Differences in genetic population structure were identified between the species, with P. pipistrellus showing a wider range of levels of genetic differentiation among colonies and a stronger relationship between genetic and geographical distance than P. pygmaeus . Differences in dispersal, mating behaviour, colony size and/or postglacial colonization patterns could contribute to the differences observed.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 90 , 539–550.     

Mitochondrial DNA phylogeny and the reconstruction of the population history of a species: the case of the European anchovy (Engraulis encrasicolus)

Analysis of mitochondrial DNA restriction fragment length polymorphism in European anchovy (Engraulis encrasicolus) revealed a large number of mitotypes that form two distinct clusters (phylads). Phylad A consists of one common mitotype and many rare secondary mitotypes that are one mutational step removed from the main type. Nucleotide diversity and number of homoplasious changes are low. Phylad B has a complex pattern of mitotype connectedness, high nucleotide diversity, and a large number of homoplasious changes. It is suggested that the two phylads evolved in isolation from each other and that present coexistence is the result of a secondary contact. Moreover, phylad A has a "star" phylogeny, which suggests that it has evolved in a population that experienced a drastic bottleneck followed by an explosion of size. Phylad A is practically the only phylad present in the Black Sea, with its frequency dropping to 85% in the northern Aegean, and to 40% in the rest of Mediterranean and the Bay of Biscay. The Black Sea is, therefore, the most likely place of origin of phylad A. Molecular data are consistent with a population bottleneck in the Black Sea during the last glaciation event and a subsequent exit of phylad A with the outflow into the Aegean following the ice melting. Phylogenetic analysis of anchovy mtDNA provides a reconstruction of population history in the Mediterranean, which is consistent with the geological information.      

Genetic diversity, host-specificity and unusual phylogeography of a cryptic, host-associated species complex of gall-inducing scale insects

Abstract.  1. Australia has a unique and speciose gall-inducing scale insect fauna that is primarily associated with Myrtaceae. Much of the diversity is currently undescribed or uncharacterised.
2. This study concerns Apiomorpha munita (Hemiptera), a scale insect that induces characteristic four-horned galls on eucalypts of subgenus Symphyomyrtus and exhibits extraordinary karyotypic diversity (2n = 6 – 2n > 100). The three described subspecies of A. munita are each confined to hosts in different sections of Eucalyptus . Previous chromosomal data, however, cast doubt on the validity of the groupings, as two of the subspecies share multiple, different karyotypes (2n = 6, 20, 22, and 24).
3. Allozyme data were used to examine species delimitation, chromosome evolution, host associations and population structure in A. munita .
4. A cryptic-species radiation was revealed, with at least five taxa each restricted to a discrete set of host eucalypt species. This is consistent with host-associated speciation.
5. Karyotypic variation within A. munita partially fits the five distinct genetic groups, but there are additional chromosomal changes that are not accompanied by detected genetic differentiation.
6. The population structure of taxa within the A. munita species complex suggests that there are high levels of inbreeding, as would be expected for scale insects in which adult females are sessile. Some genotypes, however, are found over great distances (up to 1100 km). This is an unusual population structure because it combines low mobility and local differentiation with occasional long-distance dispersal, probably mediated by wind-dispersal of first-instar nymphs.     

Allozyme variation and genetic inter-relationships between seven flatfish species (Pleuronectiformes)

A total of 11 enzymes coded by 14 loci were assayed for each of 17 populations (from the north east Atlantic and Mediterranean) of seven flatfish species, including representatives of three of the four European families of the order Pleuronectiformes. Diagnostic alleles were observed for each species and there were fixed differences between the species at many loci. Thus all species were genetically distinct, although there were some common alleles. H_obs was higher than the average of a range of fish species and was also higher than that of vertebrate species as a whole. It seems that flatfish as a group may show higher levels of genetic variation than other fish. Values of genetic identity for all pairwise comparisons fell comfortably within the ranges expected. The data support the grouping of plaice and flounder into a single genus, Pleuronectes , but it is concluded that the retention of the dab in a separate genus, Limanda , is justified. A high level of genetic divergence was found between Dover and thickback soles. Genetic divergence data support the hypothesis that Pleuronectes flesus luscus in the Aegean Sea is a distinct subspecies of Pleuronectes flesus (flounder). The data show a clear separation of the Mediterranean Dover sole population from those in the Atlantic. Low genetic divergence was observed between the Aegean Sea and Atlantic brill populations. It is speculated that about 5 Mya the families Pleuronectidae and later Soleidae evolved from the ancestral Scophthalmidae.     

Genetic variability and structure of the water vole Arvicola amphibius across four metapopulations in northern Norway

Water vole Arvicola amphibius populations have recently experienced severe decline in several European countries as a consequence of both reduction in suitable habitat and the establishment of the alien predator American mink Neovison vison. We used DNA microsatellite markers to describe the genetic structure of 14 island populations of water vole off the coast of northern Norway. We looked at intra‐ and inter‐population levels of genetic variation and examined the effect of distance among pairs of populations on genetic differentiation (isolation by distance). We found a high level of genetic differentiation (measured by F_ST) among populations overall as well as between all pairs of populations. The genetic differentiation between populations was positively correlated with geographic distance between them. A clustering analysis grouped individuals into 7 distinct clusters and showed the presence of 3 immigrants among them. Our results suggest a small geographic scale for evolutionary and population dynamic processes in our water vole populations.     

氨基酸在黄东海食物网关键种——鯷鱼（Engraulis japonicus）食物链中的传递

采用活体饵料对黄东海生态系统食物网关键种食物链的中下营养层次"浮游植物-中华哲水蚤(Calanus sinicus)-鯷鱼(Engraulis japonicus)"进行了室内模拟实验研究,以了解氨基酸在该食物链中的传递过程.通过76 d的培养实验,对采集样品做了14种氨基酸含量的定量分析.结果表明,在3个营养层次中中华哲水蚤起着十分关键的承上启下作用,它不仅将小球藻的植物性蛋白转化为动物性蛋白,大幅度地提高了赖氨酸的含量,而且将氨基酸总含量从小球藻的6.10%提高到24.16%.作为该食物网主要经济鱼类重要饵料的鯷鱼则进一步将氨基酸含量提高到27.06%.中华哲水蚤的氨基酸相对组成与小球藻有明显的相关性(r=0.606,p＜0.05),其中7种必需氨基酸的相关性相对较弱,而非必需氨基酸的相关性明显较强.鯷鱼的食性由合成饵料转变为活体中华哲水蚤时,其氨基酸量也随饵料的改变而有所变化,从与合成饵料相关转为与中华哲水蚤有更紧密的相关.鯷鱼排泄粪便中的氨基酸含量主要由新陈代谢的生理过程所决定.     

Binding kinetics and sequencing of hepatic alpha1-adrenergic receptors in two marine teleosts, mackerel (Scomber scombrus) and anchovy (Engraulis encrasicolus)

Liver alpha(1)-adrenoceptors (ARs) are demonstrated, or at least hypothesized, in freshwater and brackish-water teleosts, whereas no data are available for marine teleosts. This study evaluates the presence of alpha(1)-ARs in the liver of two marine teleosts, the anchovy Engraulis encrasicolus and the mackerel Scomber scombrus, and examines on a broad scale the possibility that habitats posing different challenges also influence phenotypic trait selection. Binding assays were performed also on liver membranes from the carp Cyprinus carpio as a direct comparison with a freshwater species. Scatchard analysis of [(3)H]prazosin binding to purified liver membranes from anchovy, mackerel and carp resulted in K(d) values of 1.51+/-0.085, 1.26+/-0.098, and 2.61+/-0.22 nM, and B(max) values of 87.4+/-9.12, 77+/-8.29, and 115.22+/-3.31 fmol/mg protein, respectively. Thus, alpha(1)-ARs of the two marine teleosts showed higher [(3)H]prazosin affinity compared with those of the freshwater/brackish-water fish studied thus far, whereas the number of liver binding sites did not differ significantly from that of carp, eel or trout. A preliminary phylogeny based on amino acid sequence analysis indicated the presence of at least an alpha(1A)-AR in mackerel and an alpha(1D)-AR in both anchovy and mackerel. This is the first indication of alpha(1)-AR subtypes in any marine species, but further studies are needed to ascertain the physiological role of these alpha(1)-ARs in these two marine species.     

Habitat‐specific population structure in native western flower thrips Frankliniella occidentalis (Insecta,Thysanoptera)

Invasions by pest organisms are among the main challenges for sustainable crop protection. They pose a serious threat to crop production by introducing a highly unpredictable element to existing crop protection strategies. The western flower thrips Frankliniella occidentalis (Insecta, Thysanoptera) managed to invade ornamental greenhouses worldwide within < 25 years. To shed light on possible genetic and/or ecological factors that may have been responsible for this invasion success, we studied the population genetic structure of western flower thrips in its native range in western North America. Analysis of nucleotide sequence variation and variation at microsatellite loci revealed the existence of two habitat‐specific phylogenetic lineages (ecotypes) with allopatric distribution. One lineage is associated with hot/dry climates, the second lineage is restricted to cool/moist climates. We speculate that the ecological niche segregation found in this study may be among the key factors determining the invasion potential of western flower thrips.     

A new species of the genus Lightiella: the first record of Cephalocarida (Crustacea) in Europe

A new species of Cephalocarida belonging to the genus Lightiella is described. Like all known species of Lightiella , the new species is characterized by reduction of trunk segment 8, which also lacks both pleura and thoracopods. The diagnostic characters of the species are: (1) one seta on the inner distal corner of the penultimate endopodal segment of second maxilla and thoracopods 1–5; (2) only one claw on the distal segment of the endopod of thoracopod 6. A cladistic analysis of 27 morphological characters was used to estimate the phylogeny of all species of Lightiella , with all other cephalocarid species used as outgroups. The discovery of this species in the Mediterranean fills a gap in the distribution of the genus and of the entire class.  © 2006 The Linnean Society of London, Zoological Journal of the Linnean Society , 2006, 148 , 209–220.     

Maintenance of genetic and morphological identity in two sibling Syrrhopodon species (Calymperaceae,Bryopsida) despite extensive introgression

Bryophytes are a group of land plants in which the role of hybridization has long been challenged. Using genotyping by sequencing to circumvent the lack of molecular variation at selected loci previously used for phylogeny and morphology, we determine the level of genetic and morphological divergence and reproductive isolation between the sibling Syrrhopodon annotinus and S. simmondsii (Calymperaceae, Bryopsida) that occur in sympatry but in different habitats in lowland Amazonian rainforests. A clear morphological differentiation and a low (0.06), but significant Fst derived from the analysis of 183 single nucleotide polymorphisms were observed between the two species. Conspecific pairs of individuals consistently exhibited higher average kinship coefficients along a gradient of geographic isolation than interspecific pairs. The weak, but significant genetic divergence observed is consistent with growing evidence that ecological specialization can lead to genetic differentiation among bryophyte species. Nevertheless, the spatial genetic structures of the two species were significantly correlated, as evidenced by the significant slope of the Mantel test based on kinship coefficients between pairs of interspecific individuals and the geographic distance separating them. Interspecific pairs of individuals are thus more closely related when they are geographically closer, suggesting that isolation‐by‐distance is stronger than the interspecific reproductive barrier and pointing to interspecific gene flow. We conclude that interspecific introgression, whose role has long been questioned in bryophytes, may take place even in species wherein sporophyte production is scarce due to dioicy, raising the question as to what mechanisms maintain differentiation despite weak reproductive isolation.     

Colonization and dispersal in a social species, the Bechstein's bat (Myotis bechsteinii)

Metapopulation genetic models consider that colonization and dispersal are distinct behaviours. However, whether colonization and dispersal indeed reflect different biological processes in nature is unclear. One possibility to test this assumption is to assess patterns of autosomal and mitochondrial genetic structure in species with strict female philopatry, such as the communally breeding Bechstein's bat. In this species, mitochondrial DNA can spread only when females establish new colonies, and autosomal DNA is transmitted among colonies only when females mate with solitary males born in foreign colonies. Investigating the genetic structure among 37 colonies, we found that autosomal genes followed an island model on a regional scale and a model of isolation by distance on a larger geographical scale. In contrast, mitochondrial genetic structure revealed no pattern of isolation by distance at a large scale but exhibited an effect of ecological barriers on a regional scale. Our results provide strong empirical evidence that colonization and dispersal do not follow the same behavioural rules in this bat, supporting the assumption of metapopulation genetic models.