Phylogenetic relationships among North American Alosa species (Clupeidae)

A phylogeny of the six North American species in the genus Alosa , with representatives of three Eurasian species, was generated using mtDNA sequences. This was accomplished by obtaining sequences for three North American species and additional geographical sampling of the other three species. The subgenus Alosa , including the formerly recognized subgenus Caspialosa , formed a strongly supported monophyletic group. Alosa alabamae was part of a polytomy with Alosa sapidissima , which was interpreted to support the recognition of A. alabamae as an incipient, yet distinct, species. The subgenus Pomolobus was not recovered as a monophyletic group. Alosa chrysochloris was basal to all other Alosa , although this position was only weakly supported. Previous work had indicated that Alosa pseudoharengus and Alosa aestivalis are not reciprocally monophyletic, but additional sampling in this study did not detect any further cases of shared haplotypes between the two species. The phylogeny supports previous hypotheses that the evolution of North American Alosa species in the Gulf of Mexico ( A. chrysochloris and A. alabamae ) was the result of two independent events. First, the ancestor of A. chrysochloris was isolated in the Gulf of Mexico, likely by the close of the Suwannee Straits, and this was followed later by dispersal of the ancestor of A. alabamae around the Florida peninsula into the Gulf of Mexico sometime during or after the Pleistocene.     

Retina-specific LDH isozyme in blueback herring, Alosa aestivalis (Mitchell), and alewife, Aiosa pseudoharengus (Wilson)

The retina of 390 Alosa aestivalis and 410 Alosa pseudoharengus have been examined by means of starch-gel electrophoresis. The retina-specific E₄ isozyme has been found to occur in all the fish examined. This study demonstrates for the first time that the E₄ isozyme occurs in A. aestivalis. Because the E₄ isozyme is not polymorphic and has an identical mobility in A. pseudoharengus and in A. aestivalis it is neither suitable for use as a species identification characteristic nor a population marker. Alosa aestivalis and Alosa pseudoharengus are two commercially important ana-dromous species of fish in New Brunswick, Canada. These two species may occur together in the same spawning runs but w^rhile A. pseudoharengus has a wide distribution along the East coast of North America (Leim & Scott, 1966) A. aestivalis occurs in a very limited area in Canada where it is at the northern limit of its range and because of increasing threat of pollution has been listed by McAllister (1970) as one of 17 endangered species. These two species of fish are morphologically very similar and can only be separated by the colour of the abdominal peritoneum (Leim & Scott, 1966). McKenzie (1973) has compared these two species by means of protein electrophoresis and found that while the muscle myogen patterns were species specific, the LDH patterns were the same in both species. He described these two species as five isozyme fish showing the LDH isozymes A₄, A₃B, A₂B₂, AB₃ and B₄. Since Horowitz & Whitt (1972) have reported the presence of the E₄ isozyme in the retina of some teleosts including. A. pseudoharengus but not including A. aestivalis, I considered it worth-while to re-examine A. aestivalis and A. pseudoharengus to find out whether A. aestivalis possessed this isozyme and, if so, whether the mobility of the isozyme could be used as a species identification characteristic and as a population marker. The fish used in this study were collected from five different locations during the 1971 spring migration period and held deep frozen for eight months before they were examined. They were identical to the specimens used for the study reported by McKenzie (1973) where the collection dates, numbers of fish and geographic locations are given. One eyeball from each of 390 A. aestivalis and 410 A. pseudoharengus was removed. Each eyeball was homogenized in 10 drops of distilled water and allowed to stand for one hour at 4^oC. The samples were then centrifuged for 10 min at 12 000 g. The supernatants were used immediately for vertical starch-gel electrophoresis. The apparatus used was that described by Boyer & Hiner (1963). The conditions of electrophoresis were the same as used by Saunders & McKenzie (1971). The LDH bands were stained by the deposition of blue formazan dyes in the regions of LDH activity. The stain formula and details of methods are given in Whitt (1970). The LDH isozyme patterns of all the fish examined were identical. The location of the isozymes A₄, A₃B, A₂B₂, AB₃ and B₄ are indicated in Fig. 1. A₄ is abundant in muscle while B₄ is abundant in heart. Because the LDH subunits assemble preferentially into homodimeric pairs before forming tetramers (Markert & Ursprung, 1971). A₄. A₂B₂ and B₄ show up in electropherograms as strong bands while A₃B and AB₃ show up as weak bands. The retina-specific isozyme E₄ is shown between B₄ and AB₃. Whitt (1970) has already demonstrated that A. pseudoharengus is a five isozyme fish. This has been confirmed by McKenzie (1973) who also compared both A. pseudoharengus and A. aestivalis and found these five isozymes had identical mobilities in both species of fish. The present study demonstrates for the first time that the retina-specific E₄ occurs in A. aestivalis where it has the same electro-phoretic mobility as that of A. pseudoharengus. The patterns are the same and do not appear to vary with geographic origin of the fish. The reason why the presence of the E₄ isozyme was demonstrated in the present study and not in the previous one (McKenzie, 1973) is because of the method used. In that study the migration length was not long enough to sufficiently separate the enzymes. In the present study vertical starch-gel electrophoresis which allows for long migration distances was used. As has already been shown for the A-B isozymes (McKenzie, 1973), the E₄ isozyme is not polymorphic in these two species of fish. It therefore has no use as apopulation marker. Because the E₄ isozyme has an identical mobility in both species of fish, it cannot be used as a species identification characteristic.     

Mitochondrial genome of the American shad Alosa sapidissima

The complete mitochondrial genome of Alosa sapidissima has been determined. The total length of the mitogenome was 16,697 bp and had a gene content (13 protein-coding, 22 tRNAs and 2 rRNAs. Except for the seven tRNA and Nd6 genes, all other mitochondrial genes are encoded on the heavy strand. The overall base composition of the heavy strand is 28.3% A, 24.8% T, 28.9% C, 17.9% G, with an AT content of 53.1%. The DNA sequence of Alosa. sapidissima shared 97.1, 93.9, 88.8 and 82.3% sequence identity with that of Alosa alosa, Alosa pseudoharengus. Molecular data here presented provide a useful toll for evolutionary as well as population genetic studied.     

Genetic polymorphism of adenosine deaminase (ADA; E.C. 3.5.4.4.) in allis shad, Alosa alosa and twaite shad, Alosa fallax

A genetic polymorphism of adenosine deaminase (ADA), is described for the first time in European shad species, Alosa alosa and Alosa fallax . Significant heterogeneity in gene frequencies was found, both between species and within species.     

Genetic diversity and structure of two hybridizing anadromous fishes (Alosa pseudoharengus,Alosa aestivalis) across the northern portion of their ranges

Alewife (Alosa pseudoharengus) and blueback herring (Alosa aestivalis), also known collectively as either river herring or gaspereau, are anadromous clupeid fishes that display spatiotemporal overlap during riverine spawning migrations. Both species have experienced severe population declines within portions of their ranges. Evidence that they home to their natal rivers to spawn suggests the likelihood of ecologically significant population structure, yet this hypothesis has not been rigorously tested. We examined genetic diversity, differentiation and population structure in 34 alewife and four blueback herring populations spanning a 2,500 km portion of their northern range, using 14 microsatellite loci. Significant differentiation was detected among most rivers, and eight genetically defined alewife population clusters that largely corresponded to hydrographic regions were identified. Similar population structure was seen for blueback herring. Genetic isolation by distance was not significant among alewife populations in regions that have been historically influenced by dams, and/or stock transfers, but was highly significant in two regions that have not been subject to these influences. Genetic differentiation of alewife populations was strongest in the Bay of Fundy. Bottleneck tests revealed evidence of demographic bottlenecks in all of the alewife populations. Lastly, our results indicated that hybridization between alewife and blueback herring is common.     

Permanent genetic resources added to Molecular Ecology Resources Database 1 August 2011-30 September 2011

This article documents the addition of 299 microsatellite marker loci and nine pairs of single-nucleotide polymorphism (SNP) EPIC primers to the Molecular Ecology Resources (MER) Database. Loci were developed for the following species: Alosa pseudoharengus, Alosa aestivalis, Aphis spiraecola, Argopecten purpuratus, Coreoleuciscus splendidus, Garra gotyla, Hippodamia convergens, Linnaea borealis, Menippe mercenaria, Menippe adina, Parus major, Pinus densiflora, Portunus trituberculatus, Procontarinia mangiferae, Rhynchophorus ferrugineus, Schizothorax richardsonii, Scophthalmus rhombus, Tetraponera aethiops, Thaumetopoea pityocampa, Tuta absoluta and Ugni molinae. These loci were cross-tested on the following species: Barilius bendelisis, Chiromantes haematocheir, Eriocheir sinensis, Eucalyptus camaldulensis, Eucalyptus cladocalix, Eucalyptus globulus, Garra litaninsis vishwanath, Garra para lissorhynchus, Guindilla trinervis, Hemigrapsus sanguineus, Luma chequen. Guayaba, Myrceugenia colchagüensis, Myrceugenia correifolia, Myrceugenia exsucca, Parasesarma plicatum, Parus major, Portunus pelagicus, Psidium guayaba, Schizothorax richardsonii, Scophthalmus maximus, Tetraponera latifrons, Thaumetopoea bonjeani, Thaumetopoea ispartensis, Thaumetopoea libanotica, Thaumetopoea pinivora, Thaumetopoea pityocampa ena clade, Thaumetopoea solitaria, Thaumetopoea wilkinsoni and Tor putitora. This article also documents the addition of nine EPIC primer pairs for Euphaea decorata, Euphaea formosa, Euphaea ornata and Euphaea yayeyamana.     

Genetic relationships among the shads (Alosa) revealed by mitochondrial DNA analysis

We surveyed restriction site differences in mitochondrial DNA. (mtDNA) among five species of shad ( Alosa ) from North America and Europe. Allis shad, Alosa alosa and twaite shad, Alosa fallax shared two divergent genotype groups, suggesting that the two forms are either a single species, or are distinct species that have hybridized. Phenetic and cladistic analyses of the relationships among the mitochondrial genotypes defined two groups of shad, corresponding to the subgenera, Alosa and Pomolobus . The mean estimated sequence divergence between the mtDNAs of these two groups of shad was 6.5%. Taken in conjunction with fossil data, this divergence estimate suggests that the rate of mtDNA divergence between the two subgenera has been almost 10-fold lower than the 'conventional' clock calibration for mtDNA.     

Genetic monitoring of two decades of hybridization between allis shad (Alosa alosa) and twaite shad (Alosa fallax)

Habitat alteration has been implicated in driving hybridization between the sympatric migratory shads Alosa alosa and Alosa fallax. Morphological and molecular evidence is consistent with hybridization across the overlapping range of these species, but the temporal extent of hybrid occurrence and genetic consequences for populations have not been explored. Using eight nuclear microsatellite loci and samples collected between 1989 and 2008 in the Solway Firth (UK), we genetically identified hybrids, studied temporal changes in their frequency, and explored changes in allele frequencies of parental populations. These molecular data confirmed the hybrid status of individuals identified using morphology (number of rakers on the outer gill arch), and enabled separation of hybrids from purebred individuals. Mitochondrial cytochrome-b sequencing revealed the presence of two haplogroups, each predominantly occurring in one species. Heterospecific haplotypes were found in 22.3 and 12.8% of A. alosa and A. fallax individuals, respectively, consistent with backcrossing and suggesting that hybrids are fertile. On average, microsatellite-identified hybrids comprised 12.7% of all samples, but when individuals with cytonuclear discordance were also considered introgressed on average 25.4% of individuals were of hybrid ancestry. Overall, allelic richness remained largely unchanged within species, but there were declines in the inbreeding coefficient (F _IS) of both species and episodes of significant temporal allelic frequency change. Hybrids sampled between 2004 and 2008 showed no evidence of lower fecundity relative to purebred individuals. Together, results suggest that hybridization between shad species in northern Europe is prevalent, and has been ongoing over at least two decades. The challenge is now to understand the extent to which observed patterns are linked to immigration from other populations, and the mechanisms that have prevented species collapse despite apparent hybrid fertility and longstanding introgression of neutral markers.     

Genetic structure of the spawning population of Danube shad, Alosa pontica, Eichwaldt 1838 (Clupeiformes, Alosiinae)

The genetic structure of the population of Danube shad, Alosa pontica, has been studied by means of analysis of 3 polymorphic biochemical gene loci. The results of the study provide evidence of its genetic heterogeneity which is expressed by: firstly, an unbalanced ratio of genotype loci manifested by an excess of rare homozygotes and deficite of the correspoding heterozygotes, and secondly, differences in the allele frequencies between shad populations arriving for spawning in March-April and May-June. It is suggested that there could be two causes of heterogeneity: one due to the introgressive hybridization between various forms of A. pontica and another to the differences between early and late spring races of shad which to a certain extent are reproductively autonomous.     

Interspecific differentiation and intraspecific substructure in two closely related clupeids with extensive hybridization, Alosa alosa and Alosa fallax

In this study, the evolutionary relationships within and among populations of European shads, Alosa alosa and Alosa fallax , was investigated. Screening of allelic variation across eight allozyme loci and sequencing 448 bp of the mtDNA cytochrome b gene in 14 rivers throughout the range of the species supported that the two taxa were independent lineages (1·3% net nucleotide divergence) despite extensive hybridization. Genetic diversity and structure was considerably higher in A. fallax than A. alosa and the former species revealed evidence of distinct lineages in the Mediterranean and Atlantic basins. A Bayesian clustering approach combined with gill raker counts verified that individuals of the two species could be assigned to their parent group with relatively high confidence. Evaluation of hybridization in the Lima and Mondego Rivers in Portugal provided evidence that introgression is extensive but is not currently obscuring (through hybrid swarming) the diagnosability of the two species.     

The occurrence of Eubothrium fragile (Cestoda: Pseudophyllidae) in twaite shad, Alosa fallax (Lacépède) in the River Severn

The occurrence, size and maturity changes of Eubothrium fragile have been studied in postlarvae, juveniles and adult twaìte shad, Alosa fallax , from several locations in the River Severn. Parasites were only found in adult shad and not in post-larvae or juveniles. No juvenile or recently acquired cestodes were identified as such, but adults were present in shad throughout the whole period of their spawning migration. A large proportion of the parasites were gravid upon arrival in the river and, although eggs were subsequently released into fresh water, there was no loss of cestodes from the fish. It was concluded that E. fragile is a marine species, that the parasites found in adult shad in fresh water were the residue of a marine life cycle and that the eggs released in fresh water were part of the parasite's natural reproductive wastage. The distribution and biology of E. fragile were discussed and it is considered that it is typical of the marine species of the genus.     

Electrophoretic identity between allis shad, Alosa alosa (L.), and twaite shad, A.fallax (Lacépède)

Morphological characteristics as well as electrophoretic polymorphism have been analysed in eight samples of allis shad, Alosa alosa (L.) and twaite shad, Alosa fallax (Lacepede), collected in the Loire basin and the Gironde-Dordogne system. The morphological characteristics showed that allis and twaite shad were present in these samples. Moreover, specimens with intermediate characteristics were found in the Loire and assumed to be hybrids between the two forms. By contrast, the two species were monomorphic and electrophoretically indistingishable at the 22 loci analysed. Therefore, it cannot be excluded that these two forms correspond to a single species.     

Feeding chronology and habits of Alosa spp. (Clupeidae) juveniles from the lower Hudson River estuary, New York

Synopsis Feeding habits of juvenile alewife, A. pseudoharengus, blueback herring, A. aestivalis, and American shad, Alosa sapidissima, were examined over a 24 h period at an inshore location on the lower Hudson River. Feeding periodicity differed by species: alewives showed no diel differences, whereas shad fed least intensively near dawn and herring least intensively at night. Alewives fed primarily on chironomids and the amphipod Corophium lacustre, shad on Formicidae and larval chironomids, and herring on chironomids and copepods. Diel variation in prey selection was evident. Dietary overlap was generally greatest between alewife and herring and least between shad and herring.     

The nematode Anisakis simplex in American shad (Alosa sapidissima) in two Oregon rivers

This paper represents the first report of the nematode Anisakis simplex in the American shad (Alosa sapidissima) in its introduced range in the American Pacific Northwest. All the adult shad sampled from spawning populations in the Willamette (n = 9) and Umpqua (n = 12) rivers were infected with A. simplex with intensities ranging from 6 to 89 worms per fish. This preliminary investigation contrasts sharply with previous studies in the native range of American shad and confirms that this fish may be an important intermediate host for A. simplex in the Pacific Northwest. It is suggested that this new parasite-host relationship has led to an ecological expansion into rivers and Anisakis may present an emerging health risk for wildlife and some human consumers.     

Will alewives (Alosa pseudoharengus) feed in the dark?

Synopsis Results of a laboratory experiment indicate that alewives (Alosa pseudoharengus) can feed in the dark onDaphnia and that this feeding is not size selective. It is presumed that the fish filter feed. Observations on small alewives (ca 50 to 70 mm) confirm that they will filter feed in Lake Michigan and filtering activity increases as it gets dark.     

Tolerance of young allis shad Alosa alosa (Clupeidae) to oxy-thermic stress

The ecology of the young stages of allis shad Alosa alosa is poorly documented, although they can be exposed to many pressures during their freshwater phase and their downstream migration. When passing through systems such as the Gironde-Garonne-Dordogne watershed (GGD, SW France), they can be subjected to high temperatures and low levels of oxygen (hypoxia). The aim of this work is to assess the tolerance of young Alosa alosa at four ages (c. 10, 30, 60 and 85 days old) by challenging them to different temperatures (18, 22, 26 and 28°C) together with decreasing oxygen saturation levels (from 100% to 30%). Survival of the 10-day-old individuals was not influenced by oxy-thermic conditions, but high stress levels were detected and perhaps this age class was too fragile regarding the constraint of the experimental design. Survival at 30 and at 60 days old was negatively influenced by the highest temperatures tested alone (from 26°C and from 28°C, respectively) but no effect was detected at 85 days old up to 28°C. A combined effect of temperature and oxygen level was highlighted, with heat accelerating survival decrease when associated with oxygen level depletion: essentially, survival was critical (<50%) at 30 days old at temperature ≥22°C together with 30% O₂; at 60 days old, at temperature = 28°C with 30% O₂; at 85 days old, at temperature ≥26°C with ≤40% O₂. Tolerance to oxy-thermic pressures appeared to be greater among the migratory ages (60 and 85 days old) than among the 30-day-old group. Based on environmental data recorded in the GGD system and on our experimental results, an exploratory analysis allowed a discussion of the possible impact of past oxy-thermic conditions on the local population dynamics between 2005 and 2018. The oxy-thermic conditions that may affect Alosa alosa at ages when they migrate downstream (60 and 85 days old) were not frequently recorded in this period, except in cases of extreme episodes of heat together with hypoxia that occurred in some years, in summertime in the turbidity maximum zone of the Gironde estuary (particularly in the year 2006). Interestingly, oxy-thermic conditions that are likely to threaten the 30-day-old individuals occurred more frequently in the lower freshwater parts of the GGD system between the years 2005 and 2018. In the context of climate change, a general increase in temperature is predicted, as well as more frequent and severe hypoxic events, therefore we suggest that local Alosa alosa population recruitment could encounter critical oxy-thermic conditions more frequently in the future if no adaptive management of water resources occurs.     

Length‐weight and length‐length relationships of four Alosa species along the southern Caspian Sea coast

This study investigates length‐weight and length‐length relationships of four shad species (Alosa braschnikowi, Alosa caspia, Alosa kessleri, and Alosa saposchnikowii) captured on the southern Caspian Sea coast of Iran. The relationship of total length (TL), fork length (FL) and standard length (SL) and the relationship between total length and body weight are presented.     

Lactate dehydrogenase isozymes in the genus Channa: Species-specific patterns

The lactate dehydrogenase isozyme system for five Channa species (snakehead fish) have been examined by means of polyacrylamide gel electrophoresis. The pattern and distribution of the LDH isozymes in all these species are found to be species-specific with a reversed relative mobility of the A and B subunits as compared to most of the other vertebrates. In addition to these two subunits, an eye-specific LDH E isozyme has also been detected in these species.