Isolation and characterization of microsatellites in Chinese sturgeon,Acipenser sinensis

From (GATA)_n and (AAAG)_n enriched genomic libraries for the Chinese sturgeon (Acipenser sinensis), 50 primer pairs were developed using the fast isolation by AFLP of sequences containing repeats (FIASCO) protocol. Forty‐six primer pairs exhibited highly polymorphic with two to 11 alleles per locus, while the rest four displayed monomorphic. These markers yielded 246 alleles in a survey of eight specimens of wild A. sinensis. Average observed heterozygosity ranged from 0.13 to 1.00. These loci should provide sufficient levels of genetic diversity to allow parentage analysis for artificial stocking management and delineation of fine‐scale population structure.     

Isolation of microsatellite loci from the endemic and endangered Adriatic sturgeon (<Emphasis Type="Italic">Acipenser naccarii</Emphasis>)

With the aim of elaborating a breeding plan on a captive stock of the highly endangered Adriatic sturgeon (Acipenser naccarii), a total of 10 polymorphic microsatellite loci were isolated from an enriched library. The results of cross amplification of additional 8 loci previously isolated from A. oxyrinchus, A. fulvescens and Scaphyrinchus platorhynchus are also reported. Given the tetraploid condition of the species the genetic variability was estimated basing on the number of alleles per individuals and the average band sharing.     

Swimming alters responses to hypoxia in the Adriatic sturgeon Acipenser naccarii

When the Adriatic sturgeon Acipenser naccarii was exposed to progressive hypoxia under static conditions, it exhibited a linear decline in O₂ uptake, behaving as an 'oxyconformer'. When, however, it was allowed to swim at a low sustained speed, it could regulate O₂ uptake down to a mean ± s . e . critical ( P _crit) of 4·9 ± 0·5 kPa ( n = 6). At moderate levels of hypoxia, static fish exhibited significant reductions in arterial blood O₂ content, and increases in plasma lactate, which were not observed in swimming animals.     

Embryonic development of adriatic sturgeon,Acipenser naccarii (Bonaparte 1836), in farming conditions: a guide

The sequence and timing of the embryonic development of Adriatic sturgeon (Acipenser naccarii) are described at a constant temperature (17 ± 1 °C), from fertilisation to hatch in a hatchery. Fertilised eggs, obtained from one female and two males, were held in a flow‐through system. On the first day, embryos were sampled every 20 min during the first 12 h, and every 40 min in the following 12 h. Embryos were sampled hourly on the second day. On the third and fourth days, embryos were sampled every 2 h, and every 3 h on the fifth and sixth days. The first cleavage furrow appeared at 1 h 40 min postfertilisation. Blastulation concluded at 12 HPF (hours postfertilisation), when the dorsal blastopore lip formed. The completion of gastrulation was at 18 HPF, closing of the neural tube at 23 HPF and formation of the s‐shape heart at 31 HPF. The mass hatch occurred at 120 HPF. A. naccarii is a relatively common sturgeon species in aquaculture and possesses similar developmental patterns to those of other sturgeons; hence, we can use this species as a model for further studies about sturgeon species which are more difficult to breed artificially. Information about the embryonic development of the Adriatic sturgeon could assist restocking programmes.     

Identification of microsatellite loci in lake sturgeon,Acipenser fulvescens,and their variability in green sturgeon,A. medirostris

From (CATC)_n, (GATA)_n, (AAAC)_n, and (CA)_n–enriched libraries for the lake sturgeon Acipenser fulvescens, 254 primer pairs were developed. These primer pairs resulted in the identification of 128 microsatellite loci in either A. fulvescens or A. medirostris. Polymorphic loci were identified in both sturgeon species for 48 of the primer pairs and 14 of the primer pairs amplified polymorphic loci only in A. medirostris. Most of the identified loci appear to be tetrasomic (79.1% in A. fulvescens and 64.5% in A. medirostris). These results offer estimates of the degree of diploidization in each of these species.     

Isolation and characterization of microsatellites in Zosterisessor ophiocephalus (Perciformes,Gobiidae)

We isolated and characterized 10 polymorphic microsatellite loci from two partial genomic libraries of Zosterisessor ophiocephalus (Perciformes, Gobiidae), enriched for AC and for multiple motifs. Variability was tested on specimens from the Venice lagoon revealing a high degree of genetic variation. The loci will be useful for monitoring the biodiversity of the species at the genetic level and for parentage assessment purposes.     

Purification and characterization of the hemoglobin components of Adriatic sturgeon (Acipenser naccarii) blood

The oxygen binding properties of Acipenser naccarii hemoglobins have been investigated, and were found not to differ significantly from those shown by blood, intact erythrocytes and hemolysate in the presence of the physiological cofactors GTP and chloride ions. In particular, the oxygen equilibrium reveal a very low sensitivity of the hemolysate to the chloride ions and temperature while in the presence of organic phosphates their oxygen affinity decreased strongly. The electrophoretic analysis of the hemolysate of the sturgeon showed the presence of two hemoglobin components, each with a considerable globin multiplicity. The partial amino acid sequence of the a and P chain of the single hemoglobins was also established.     

Cardiovascular responses to hypoxia in the Adriatic sturgeon (Acipenser naccarii)

The in vivo cardiovascular responses to hypoxia, and the intrinsic functional characteristics of the heart in vitro , were determined, and compared, in the Adriatic sturgeon (Acipenser naccarii). During exposure to hypoxia in vivo , blood oxygen content (Cao₂) declined as water 0₂ partial pressure (Pwo₂) was reduced, despite an increase in haematocrit. The main cardiovascular response was a reduction in dorsal aortic blood pressure, with a slight bradycardia, while cardiac output remained constant. Reduced oxygen content of the perfusate had significant inhibitory effects on the intrinsic performance of the heart in vitro , causing a reduction in the heart rate; a reduction in the sensitivity of responses to increased preload (Frank-Starling response), and a more rapid decline in power output and stroke volume when afterload was increased. Overall, the in vitro results suggest that hypoxia depresses the contractility of the heart (i.e. its inotropic responses). The reduction in dorsal aortic pressure in vivo may, therefore, counteract the depressive effects of hypoxia on heart contractility, and thereby avoid a hypoxic depression of cardiac output.     

Isolation and characterization of microsatellites in Pachygrapsus marmoratus (Grapsidae; Decapoda; Brachyura)

Seven polymorphic microsatellite loci were isolated and characterized from the grapsid crab Pachygrapsus marmoratus using FIASCO (fast isolation by AFLP of sequences containing repeats) protocol. Twenty‐seven primer pairs were designed, 14 of which worked well in polymerase chain reaction (PCR), amplifying a fragment of the expected size. Variability was tested in 18 specimens collected along the coast of Tuscany (Italy). Five loci were discarded due to stutter products during their amplification, and two resulted to be monomorphic. The remaining seven loci, showed a number of alleles ranging from two to 14 and an observed heterozygosity ranging from 0.12 to 0.67.     

Aspects of early development in the Adriatic sturgeon Acipenser naccarii

This study investigates the development of the sensory-cutaneous apparatus and digestive tract of Adriatic sturgeon (Acipenser naccarii). Light and electron microscopy observations were carried out on various developmental stages, from hatching to 180 days old.
At hatching, sturgeon pre-larvae exhibit differentiation of olfactory sensory cells. By day 4 taste buds are differentiated on lips and barbels. At 12 days after hatching, the larvae are equipped with an extensive ventral cephalic sensory apparatus. Electrosensory organs are arranged in regular lines in the rostral ventral region, and taste receptors are organised in parallel rows on and inside the lips as well as on the external side of the barbel. Ventral free neuromasts are positioned in rostral grooves. The retina is completely differentiated in each stratum. At this stage, larvae show canine-like teeth on lips and pharynx, and the specific mucosae of the different digestive regions are differentiated. By day 36 the canine-like teeth are located exclusively on the tongue and roof of the buccal cavity, and the mouth is protrusible. At 180 days differentiation is still not completed, and although teeth have disappeared from the palate, they still persist along a central line on the tongue.     

Isolation and characterization of microsatellites in the sea hibiscus (Hibiscus tiliaceus L., Malvaceae) and related hibiscus species

Microsatellite loci were isolated from the sea hibiscus (Hibiscus tiliaceus L., Malvaceae), a pantropical plant with sea‐drifted seeds. This study describes six dinucleotide microsatellite loci for which the primers produced clear and polymorphic amplification patterns with different levels of variability (between three and nine alleles). Six markers were amplified in four other species of hibiscus, greatly increasing the utility of these markers.     

Comparative stable isotope analyses of green sturgeon (Acipenser medirostris) and white sturgeon (A. transmontanus) in the San Francisco estuary

Green sturgeon (Acipenser medirostris) and white sturgeon (A. transmontanus) are closely related, sympatric species that inhabit the San Francisco estuary. Green sturgeon have a more marine life history but both species spawn in the Sacramento River and reside for some duration in San Francisco Bay. These sturgeons are of conservation concern, yet little is known about their dietary competition when they overlap in space and time. To examine evidence of dietary differentiation, we collected whole blood and blood plasma from 26 green sturgeon and 35 white sturgeon in San Francisco Bay. Using carbon and nitrogen stable isotope analyses, we compared their relative trophic levels and foraging locations along the freshwater to marine gradient. Sampling blood plasma and whole blood allowed comparison of dietary integration over shorter and longer time scales, respectively. Plasma and whole blood δ¹³C values confirmed green sturgeon had more marine dietary sources than white sturgeon. Plasma δ¹⁵N values revealed white sturgeon fed at lower trophic levels than green sturgeon recently, however, whole blood δ¹⁵N values demonstrated the two species fed at the same trophic level over longer time scales. Larger individuals of both species had higher δ¹³C values than smaller individuals, reflecting more marine food sources in adulthood. Length did not affect δ¹⁵N values of either species. Isotope analyses supported the more marine life history of green than white sturgeon and potentially highlight a temporary trophic differentiation of diet between species during and preceding the overlapping life stage in San Francisco Bay.     

Repeat UCrit and endurance swimming in juvenile shortnose sturgeon (Acipenser brevirostrum)

Previous results show that juvenile shortnose sturgeon are steady swimmers and, compared with salmonids, generally have low critical swimming (UCrit) and endurance swimming capacities. Most studies on swimming capacities of sturgeon, and other fishes, include those where fish have only been swum once and the metrics of swimming performance are assessed (e.g., time swum, speed achieved). Under natural conditions, there are ample instances where fish undergo multiple swimming cycles when traversing fish ways, culverts and other sources of fast water flow. While some evidence exists for salmonids, the effects of repeat swimming are not well known for sturgeon. The current study consisted of two experiments. The first examined the UCrit of juvenile shortnose sturgeon following three consecutive swimming trials with a 30 min recovery period between subsequent tests. The second examined the endurance swimming capacities of juvenile shortnose sturgeon following three consecutive swimming trials with a 60 min recovery period between subsequent tests. Our findings indicate that (i) UCrit was consistent (~2 body lengths/s) among swimming trials; (ii) significant individual variation exists between individuals in the endurance swimming trials; and (iii) consistent results exist for individuals across swimming trials in both the UCrit and the endurance swimming tests. These results suggest that juvenile shortnose sturgeon have a high recovery capacity, and their behaviour and morphology likely reflect aspects of their swimming capacities.     

Chloride cells and pavement cells in gill epithelia of Acipenser naccarii: ultrastructural modifications in seawater‐acclimated specimens

Modifications in the chloride (mitochondria‐rich) and pavement cells of the gill epithelia of the Adriatic sturgeon Acipenser naccarii after their transfer under hypertonic environmental conditions (salinity 35) were examined by light and electron microscopy. In contrast to freshwater specimens, seawater‐acclimated fish showed a marked increase in the number and size of chloride cells. Ultrastructural modifications included: presence of a slightly invaginated apical crypt, a darker cytoplasm, a more compact tubular system, a major increase in cisternae from Golgi apparatus stacks and flattened‐out sacs with dilated ends that produced an increase in lateral and basal cell surfaces. All these changes indicated enhanced cellular activity. Pavement cells, which largely covered the chloride cells on the gill filament and lamella, exhibited a complex system of microridges on their apical surface. Typical features included numerous desmosomes that characterized the intercellular junction, and the presence in the apical cytoplasm of bundles of filaments and of electro‐dense vesicles in freshwater fish or clear vesicles in seawater‐acclimated animals.     

Nonconcordant evolutionary history of maternal and paternal lineages in Adriatic sturgeon

Although analyses of intraspecific variability are an important prerequisite for species identification assays, only a few studies have focused on population genetics and historical biogeography of sturgeon species. Here we present the first study on genetic variability of the last remaining Adriatic sturgeon, Acipenser naccarii, derived from mitochondrial and nuclear DNA. Our mitochondrial DNA analyses arranged individuals into three distinguished mitochondrial DNA haplogroups (Po1, Po2 and Buna). Two haplogroups (Po1 and Buna) were correlated to geographical distribution, whereas the third (Po2) was not. It was, however, very closely related to one lineage of its Ponto-Caspian sister species, A. gueldenstaedtii. The distribution of nuclear markers (microsatellites and amplified fragment length polymorphism) was strongly correlated to geographical distribution. An assignment test based on nuclear data placed no specimen of A. naccarii to A. gueldenstaedtii and vice versa. Therefore, the presence of gueldenstaedtii-like haplotypes within the Po population is either the result of a postglacial introgression or an ancestral polymorphism and does not indicate a hybrid population. The most valuable tool for forensic species identification purposes is one diagnostic deletion separating all A. naccarii from A. gueldenstaedtii. As both A. naccarii populations are genetically differentiated, stocking of sturgeon from the Po River in Italy into waters of the Buna River would jeopardize the genetic differences between both populations and should thus be avoided.     

Novel microsatellite markers for Atlantic sturgeon (Acipenser oxyrinchus) population delineation and broodstock management

Twenty‐one new disomic, polymorphic microsatellite DNA markers were isolated in Atlantic sturgeon, Acipenser oxyrinchus oxyrinchus. These markers yielded a total of 220 alleles in a survey of 16 fish; two to 21 alleles/locus were observed. Each locus segregated in a Mendelian fashion when tested in a family, and a set of 14 of the loci distinguished between siblings and half‐siblings. Average observed heterozygosity ranged from 18.8 to 100.0%, and no linkage disequilibrium was detected. These loci should detect sufficient genetic diversity to allow kinship analysis for broodstock management, gene marking for stocking assessment and life history studies, and delineation of fine‐scale population structure.     

Comparison of mitochondrial DNA sequences between the European and the Adriatic sturgeon

Intra- and interspecific diVerences in mitochondrial 12S ribosomal DNA sequences of Acipenser sturio and Acipenser naccarii were investigated. No variable sites were found in the sequences of nine A. sturio or in six A. naccarii . Seven substitutions were detected between A. sturio and A. naccarii .     

Effects of hypercapnia on blood-gas and acid-base status in the white sturgeon, Acipenser transmontanus

The effect of environmental hypercapnia on respiratory and acid-base variables was studied in white sturgeon, Acipenser transmontanus. Blood PCO₂, PO₂, pH, hemoglobin concentration, and plasma lactate, glucose, catecholamines and cortisol were measured first under normocapnia (water PCO₂ < 0.5 Torr, 1 Torr = 133.32 Pa), then under hypercapnia (25–35 Torr) and a final return to normocapnia at 19 ± 0.5 °C. Acute (≤ 2h) hypercapnia significantly increased arterial PCO₂ (8-fold increase), ventilation frequency (2-fold increase), plasma HCO₃ ⁻ (2.3-fold) and decreased arterial pH (to 7.15 ± 0.02). After 24 h, norepinephrine, epinephrine and cortisol, were significantly increased, and arterial pH reached its nadir (7.10 ± 0.03). During the 72- and 96-h-periods, arterial PCO₂ (24 ± 4.4 Torr) and ventilatory frequency (105 ± 5 breaths min⁻¹) stabilized, HCO₃ ⁻ reached its apparent maximum (23.6 ± 0.0 mmol⁻¹), glucose decreased by 32%, and pH increased significantly to 7.31 + 0.03. The return to normocapnia completely restored arterial PCO₂ (2.5 ± 0.14 Torr), HCO₃ ⁻ (7.4 ± 0.59 mmol · l⁻¹), ventilation frequency (71 ± 7 breaths · min⁻¹), and pH (7.75 ± 0.04). Overall, hypercapnia produced a respiratory acidosis, hyperventilation, a transient norepinephrine “spike”, and increased plasma catecholamines, cortisol, and arterial PO₂. The respiratory acidosis was only partially compensated (35% pH restoration) 96 h after the onset of hypercapnia and resulted in a significantly decreased blood-O₂ affinity (Bohr effect), as determined by construction of in vitro blood O₂ equilibrium curves at 15 °C and 20 °C. Prolonged exposure to hypercapnia may lead to acid-base disturbances and negatively affect growth of white sturgeon. Accepted: 17 August 1997     

Isolation and characterization of microsatellite loci in the icefish Chionodraco rastrospinosus (Perciformes,Notothenioidea, Channichthyidae)

We characterized eight polymorphic microsatellites in the icefish Chionodraco rastrospinosus (Perciformes, Notothenioidea, Channichthyidae). Microsatellites were isolated from a partial genomic library enriched for an AC motif. Chionodraco rastrospinosus is an endemic species inhabiting southern ocean waters surrounding the Antarctic Peninsula, the South Shetland Islands, and the South Orkney Islands. An excess of homozygotes was observed in seven out of the eight investigated loci; however, presence of null alleles was detected only for three of them suggesting that other factors may act in reducing heterozygosity. These molecular markers will be useful to investigate icefish genetic structure, possibly providing insights on its effective population size and demographic history.