Frank A. Chapman

Ionic and osmotic regulation capabilities of juvenile Gulf of Mexico sturgeon, Acipenser oxyrinchus de sotoi

Abstract The salinity tolerance, and hydromineral regulation capabilities of three size groups (small 110–170 g; medium 230–290 g, large 460–700 g; n =48 for each group) of 13-month-old juvenile Gulf of Mexico sturgeon were investigated. Fish ( n =6 for each salinity) were transferred directly from freshwater (FW) to a series of experimental salinity treatments (0, 5, 10, 15, 20, 25, 30, and 35 parts per thousand (ppt)). Fish were also acclimated in brackish water (20 ppt) for 2 weeks and transferred to a salinity of 34 ppt. In this condition juvenile Gulf of Mexico sturgeon adapted to saltwater (SW) and maintained their hydromineral balance. FW adapted sturgeon ( n =6) had an average blood hemotocrit of 28.2±0.8%, plasma osmolality of 260.7±1.6 mOsm kg −1 H 2 O, and plasma ion concentrations of 135.7±1.2 mM l −1 Na + , 106.9±1.9 mEq l −1 Cl − , and 2.9±0.1 mM l −1 K + . In SW adapted sturgeon ( n =8) blood parameters averaged 26.9±0.7% for hematocrit, 294.2±2.3 mOsm kg −1 H 2 O for osmolality, 152.0±1.7 mM l −1 Na + , 149.2±1.4 mEq l −1 for Cl − , and 3.1±0.1 mM l −1 K + . The method of transfer (abrupt or slow acclimation) directly affected fish survival and the time they took to achieve ionic and osmotic regulation. This SW adaptation appears to be related to body size, the larger the fish the easier the adaptation process. A threshold size of about 170 g was apparent for the fish to adapt to saltwater after 2 weeks of acclimation. Chloride cells were present in both FW and SW adapted sturgeon with SW and brackish water fish having chloride cells significantly ( P −2 ) and larger in size (41.0±3.85 and 34.2±4.49 μ m 2 ) than FW adapted sturgeon (10±1.0 cells mm −2 and 22±2.53 μ m 2 ). Few chloride cells were observed in the opercular membrane, however, none were found in the pseudobranch and spiracle.

Mannanoligosaccharides in Fish Nutrition: Effects of Dietary Supplementation on Growth and Gastrointestinal Villi Structure in Gulf of Mexico Sturgeon

Abstract Although low levels of dietary mannanoligosaccharide (MOS) supplementation have been shown to increase weight gain, decrease feed conversion, and stimulate intestinal villi growth in domestic mammals and birds, the responses of aquacultural species to MOS have not been studied. We examined the effects of MOS supplementation on the growth of and digestive tract morphology in Gulf sturgeon Acipenser oxyrinchus desotoi. There were no differences in growth performance (as measured by condition factors, specific growth rates for weight and fork length, and feed conversion ratios), gross gastrointestinal morphology (gut length and spiral valve length), or spiral valve villi structure (villus length, width, and density) between fish fed control and MOS-supplemented diets. However, in light of the promising results obtained by similar studies across a wide range of animals, dietary MOS supplementation in other aquacultural species merits further investigation.

Genetic distinction of pallid, shovelnose, and Alabama sturgeon: emerging species and the US Endangered Species Act

The sturgeon genus Scaphirhynchus consists of threerecognized species. Pallid and shovelnose sturgeon (S. albusand S. platorynchus, respectively) are sympatric in theMissouri and lower Mississippi Rivers of the central United States. TheAlabama sturgeon (S. suttkusi) is endemic to the nearby MobileRiver drainage and is isolated geographically from the other twospecies. Pallid sturgeon and the extremely rare Alabama sturgeon arelisted as endangered under the US Endangered Species Act (ESA).In contrast, shovelnose sturgeon are relatively common and are notlisted. Despite these taxonomies and morphological evidence, somebiologists have questioned the genetic and taxonomic distinctions of thethree species, thus raising doubts concerning the validity of protectingpallid and Alabama sturgeon under the ESA. To investigate thesequestions, we compared a 436 base-pair sequence of the mitochondrial DNA(mtDNA) control region among the three species. We observed 16 mtDNAhaplotypes defined by 27 single base-pair substitutions (transitions)and one single base-pair insertion/deletion (indel) among 78individuals examined. The maximum sequence divergence among thosehaplotypes (2.06%) was less than values usually observed betweenfish species. However, Alabama sturgeon (n = 3) weredistinguished from the other two taxa (n = 75) by aunique base-pair substitution and haplotype, and pallid and shovelnosesturgeon at their northern range of natural sympatry (upper MissouriRiver) did not share any haplotypes. On the other hand, only frequencydifferences among shared haplotypes distinguished (P < 0.01)pallid and shovelnose sturgeon at their southern range of naturalsympatry (Atchafalaya River), and genetic distances between northern andsouthern localities for each species were nearly as large as thedistances between species. These latter results are consistent withseveral hypotheses, including reports (based on morphology) of putativenatural hybrids in the Atchafalaya River but not in the upper MissouriRiver. Overall, these mtDNA results indicate significant reproductiveisolation between pallid and shovelnose sturgeon in areas of naturalsympatry, and recent evolutionary divergence of Alabama sturgeon. ThesemtDNA results provide the first molecular genetic evidence fordistinguishing the three Scaphirhynchus species and, coupledwith morphological and biogeographic data, indicate that pallid andAlabama sturgeon should be evaluated as distinct species under theESA.

Feeding Trials with Hatchery-Produced Gulf of Mexico Sturgeon Larvae

Abstract Survival and growth in larval Gulf of Mexico sturgeon Acipenser oxyrinchus desotoi fed live and formulated diets were evaluated. Live foods consisted of brine shrimp Artemia sp. and California blackworms Lumbriculus variegatus. Formulated diets consisted of commercially produced pellets and two experimentally formulated sturgeon starter diets (SS). Feeds were first offered at 5 d posthatch, 2 d before initiation of exogenous feeding. Significant differences (P 95%) and specific growth rate (12%; SGR, logarithmic growth per unit time). In contrast, commercially formulated feeds were poorly accepted at the onset of feeding, and their use resulted in nearly complete mortality (>99%) by 3 weeks. First-feeding larvae, however, displayed preference for an experimentally formulated sturgeon ...

Implications of early life stages in the natural history of the Gulf of Mexico sturgeon, Acipenser oxyrinchus de sotoi

SynopsisGulf of Mexico sturgeon were collected during their natural spring spawning migrations from the Gulf of Mexico into the Suwannee River in Florida. Peak numbers were observed during March and April. During the summer periods the fish remained in the river over very localized bottom areas. In late fall, the fish migrated from the river into the Gulf of Mexico. Laboratory experiments revealed that maximum survival of eggs, embryos and larvae of Gulf of Mexico sturgeon occurred between 15 and 20° C. Although Gulf of Mexico sturgeon appear to have a high tolerance to warm water temperatures, their embryos and larvae exhibit high mortalities at temperatures of 25° C. Based on observations of Gulf of Mexico sturgeon migratory patterns and laboratory experiments we suggest that the timing and unusual migratory behavior of Gulf of Mexico sturgeon are associated with temporal water temperature changes in the river and the Gulf of Mexico. The requirements of a thermal refuge are discussed.

An Extender Solution for the Short-Term Storage of Sturgeon Semen

Abstract An extender solution was developed to prolong the time that semen from sturgeons could be stored in the refrigerator, thus greatly improving the artificial propagation of these species for purposes of conservation and commercial aquaculture. Semen from Gulf of Mexico sturgeon Acipenser oxyrinchus desotoi and shortnose sturgeon A. brevirostrum was used to develop the extender media. Fresh semen from sturgeon is traditionally stored whole and undiluted in the refrigerator along with pure oxygen. The fertilizing capacity of semen stored in this manner is usually maintained for 12– 36 h. The mixing of fresh semen with an artificial extender solution significantly (P < 0.05) prolonged the refrigerated storage time of spermatozoa and maintained sperm motility for up to 21–28 d at 4°C. No significant differences in fertilization capacity were observed between fresh semen and semen diluted with the extender and stored from 3 to 18 d.

Karyotype of North American shortnose sturgeon Acipenser brevirostrum with the highest chromosome number in the Acipenseriformes

The shortnose sturgeon Acipenser brevirostrum was revealed to have a larger number of chromosomes than previously reported for other sturgeon species. Its chromosome number ranged from 362 to 372 (of ten specimens examined), showing intraindividual variation. The karyotype of metaphase with the highest chromosome number (372) consisted of 89 pairs of macrochromosomes and 97 pairs of microchromosomes (fundamental number; NF = 550). Although the microchromosomes were relatively shorter than the macrochromosomes, most of them had discernible arms and centromeres. Silver-stained nucleolar organizer regions (Ag-NORs) were localized on the telomeric regions of 5 pairs of chromosomes (Ag-NORs = 10): 4 were made up of small meta/submetacentrics and 1 of acrocentrics. Polyploidy of A. brevirostrum should be hexaploid based on the karyotype, numerous chromosomes, Ag-NORs, and previously reported large genome size (ca. 13 pg DNA/cell).

Acquisition of germ plasm accelerates vertebrate evolution.

Tangling Evolutionary Trees Evolutionary rates tend to vary among taxa and may result in phylogenetic trees that do not reflect the true relationships among taxa, depending on the sequences input into the analysis. Examining vertebrate trees, Evans et al. (p. 200) demonstrate that differences in evolutionary rates, leading to phylogenetic distortions, are correlated with the mechanisms underlying germ cell formation. Evolutionary rate is faster in cases where germ cells are established by maternal molecules (“preformed”) relative to those that are induced during embryogenesis (“epigenesis”) in slowly evolving and, presumably, ancestral lineages. For example, frogs evolve more rapidly than salamanders, and teleosts more rapidly than ascipenseriform fishes. Thus, epigenesis constrains the ability of gene regulatory networks to change, with the repeated and convergent evolution of preformation eliminating this constraint. Evolutionary rates are phylogenetically correlated with how germ cells are specified. Primordial germ cell (PGC) specification occurs either by induction from pluripotent cells (epigenesis) or by a cell-autonomous mechanism mediated by germ plasm (preformation). Among vertebrates, epigenesis is basal, whereas germ plasm has evolved convergently across lineages and is associated with greater speciation. We compared protein-coding sequences of vertebrate species that employ preformation with their sister taxa that use epigenesis and demonstrate that genes evolve more rapidly in species containing germ plasm. Furthermore, differences in rates of evolution appear to cause phylogenetic incongruence in protein-coding sequence comparisons between vertebrate taxa. Our results support the hypothesis that germ plasm liberates constraints on somatic development and that enhanced evolvability drives the evolution of germ plasm.

Analysis of Skin Color Development in Live Goldfish Using a Color Machine Vision System

Abstract A color machine vision system (CMVS) was used to measure and quantify color development in the skin of live goldfish Carassius auratus raised in pond or well water and fed rations of different commercial feeds. Goldfish were of the ornamental Red Oranda variety, 3 months of age, 0.15 ± 0.01 g (mean ± SD) in body weight and 1.38 ± 0.22 cm in total length. Data on color development were acquired through a charge-coupled display color video camera and an image capture card attached to a personal laptop computer. We used a color analysis program developed at the University of Florida, Department of Food Science and Human Nutrition, to interpret the skin color patterns. Pixels from the computerized image were compared and matched to one of 64 color blocks (standards) representing the entire color spectrum. Pixel groupings were represented and recorded as a frequency (percentage) of occurrence for each color standard. The CMVS provided an objective method for measuring the skin color of goldfish and al...

Carbon monoxide treatments to impart and retain muscle color in tilapia fillets.

Carbon monoxide (CO) has been used for improving the color of muscle foods. In the current study, we compared the postmortem treatment of tilapia fillets with 100% CO and euthanasia of live tilapia with CO for their ability to stabilize the color of white and red muscle of tilapia fillets. Both postmortem CO treatment and CO euthanasia were effective in increasing the redness (a* value) and lightness (L* value) of tilapia white and red muscle. Fillets obtained from CO-euthanized tilapia showed significantly higher a* and L* values during 1 mo of frozen storage at -20 degrees C and subsequent thawing and storage at 4 degrees C for 18 d. The amount of CO present in the red and white muscles decreased during the 18 d of storage at 4 degrees C. There was no significant difference in the pH, drip, or thaw loss of CO-treated tilapia fillets compared to the untreated fillets.