Water balance in eggs of striped bass (Morone saxatilis)

Measurements of embryonic volume revealed regulation capability before hatch. Water diffusion permeability, determined as tritiated water efflux, was found to be low, but within the range for fish eggs. The perivitelline fluid is readily interchangeable with the external medium due to a high chorion permeability to both water and salt.     

An in vitro assay to measure phagocytosis in striped bass hybrids (Morone saxatilis x Morone chrysops)

An in vitro phagocytosis assay was developed for hybrid striped bass (Morone saxatilis x Morone chrysops), using cells collected from the peritoneal cavity of this fish. The findings indicated that: (1) 10 days following a single intraperitoneal injection (1 ml) of Freund's incomplete adjuvant (FIA) was an appropriate time for collecting suitable working concentrations (5.3+/-4.0 x 10(7) cells ml(-1)) of peritoneal phagocytes (83.7+/-1.5% macrophages) from these hybrids held at 23 degrees C; (2) these cells phagocytosed latex beads (polystyrene microspheres 3.12 microm in diameter) after 30 min of in vitro incubation at room temperature (25+/-1 degrees C). The phagocytic ability and phagocytic capacity in a washed adherent layer exposure system were 67.2+/-2.76% and 4.14+/-0.35 beads phagocyte(-1), respectively. These results strongly suggest that a simple methodology, including baseline data serving as guidelines, is now available for conducting in vitro phagocytosis assays in this hybrid.     

Effect of light intensity and eye development on prey capture by larval striped bass Morone saxatilis

The efficacy of visual and non-visual feeding among pelagic striped bass Morone saxatilis larvae adapted to a turbid estuary was determined in the laboratory in clear water. Capture of Artemia salina (density 100 l⁻¹) was significantly affected by the interaction between age of larvae (range: 8–25 days post-hatch, dph) and light intensity (range: 0–10·6 μmol s⁻¹ m⁻² at the water surface). Visual feeding by larvae aged 9–11 dph was highest in dim light (0·086–0·79 μmol s⁻¹ m⁻²), with fish capturing up to 5 prey larva⁻¹ h⁻¹. As the larvae grew, prey capture in brighter light improved, associated with an increasing proportion of twin cone photoreceptors and improving ability of the retina to light- and dark-adapt. By age >22 dph, mean prey capture was greatest at highest light intensities (0·79 and 10·6 μmol s⁻¹ m⁻²) exceeding 100 prey larva⁻¹ h⁻¹. Incidence of feeding larvae generally improved as the larvae grew, reaching >80% in all light intensities from 16 dph onwards. The lower threshold for visual feeding, between 0·0084 and 0·03 μmol s⁻¹ m⁻², remained constant as the larvae grew, despite an increasing density of rod photoreceptors. Below this threshold, non-visual feeding was evident at a low rate (<6 prey larva⁻¹ h⁻¹) that was independent of larval age.     

Blood oxygen transport in stressed striped bass (Morone saxatilis): role of beta-adrenergic responses

Summary Strenuous 5-min exercise resulted in a 0.3 unit drop in the dorsal aortic pH of striped bass. The acidosis was metabolic: the blood lactate concentration increased during the exercise, whereas blood CO₂ tension decreased. Dorsal aortic oxygen content was maintained despite the acidosis. This was a result of increased blood O₂ tension, haemoglobin concentration and red cell volume, decreased cellular nucleoside triphosphate (NTP) concentration, and decreased proton gradient across the red cell membrane. When the fish were treated with the beta-antagonist, propranolol, before the exercise, the arterial oxygen content decreased significantly in the stress. The mean cellular haemoglobin concentration and cellular NTP concentration increased slightly, and the proton gradient across the red cell membrane decreased less than in control exercise. These results show that the beta-adrenergic responses of striped bass red cells play an important role in maintaining the arterial O₂ content in stress.Abbreviation NTP nucleoside triphosphates     

Measurement of larval striped bass (Morone saxatilis) net avoidance using evasion radius estimation to improve estimates of abundance and mortality

Net avoidance rate increases as a function of larval striped bass size. This causes under-estimation of abundance and overestimation of mortality rate. We modeled net avoidance by assuming that fish avoid the net by swimming a radial distance at a right angle to the net axis. This distance, the evasion radius, was estimated by comparing the calculated densities of striped bass larvae from a series of paired tows involving a large and a small net. Iteration and solution models were used to estimate the evasion radius for each millimeter size group of fish in order to estimate the actual density in the environment. Avoidance of the nets increased with fish length. The ratio of actual density in the environment to the measured density in the small net was used to adjust abundances measured in our ichthyoplankton surveys. After adjusting for net avoidance, mortality rates of striped bass larvae from the Sacramento-San Joaquin Estuary were reduced by 10% compared to the unadjusted rates.      

Tissue essential fatty acid composition and competitive response to dietary manipulations in white bass (Morone chrysops), striped bass (M. saxatilis) and hybrid striped bass (M. chrysopsxM. saxatilis)

The effects of wide changes in dietary levels of docosahexaenoic (DHA) or arachidonic (ArA) acids on growth, survival and fatty acid composition in body tissues of Morone larvae were examined. White bass (WB, Morone chrysops), striped bass (SB, Morone saxatilis) and sunshine hybrid bass (HSB, M. chrysopsxM. saxatilis) larvae (day 24-46) were fed Artemia nauplii enriched with algal sources of varying proportions of DHA and ArA (from 0 to over 20% of total fatty acids). WB larvae fed DHA-deficient Artemia diet retarded over 50% of their potential growth, however, increasing dietary DHA/ArA ratios were associated with a significant growth improvement. The highest proportion of polyunsaturated fatty acids was found in WB neural tissue (approx. 50% of total fatty acids), while HSB neural tissue contained the highest proportion of saturated fatty acids (approx. 35% of total fatty acids). Within the neural tissues of all Morone larvae, both DHA and ArA were generally the most dominant as well as the most responding fatty acids to dietary manipulations (except in WB fed DHA or ArA deficient diets). HSB neural tissue was particularly efficient in retaining a significant amount of DHA in the face of dietary deficiency. However, WB neural tissue was the most responsive to dietary increase in DHA, accumulating a significantly higher amount of DHA (P<0.05) than SB or HSB. Results demonstrate significant differences in fatty acid composition and growth responsiveness to dietary manipulations between Morone larvae species and within specific tissues. WB weight gain and neural tissue composition was affected most by dietary changes in both DHA and ArA whereas SB and HSB tissue compositions were generally less affected by dietary manipulations.     

Effect of salinity on expression of branchial ion transporters in striped bass (Morone saxatilis)

The time course of osmoregulatory adjustments and expressional changes of three key ion transporters in the gill were investigated in the striped bass during salinity acclimations. In three experiments, fish were transferred from fresh water (FW) to seawater (SW), from SW to FW, and from 15-ppt brackish water (BW) to either FW or SW, respectively. Each transfer induced minor deflections in serum [Na+] and muscle water content, both being corrected rapidly (24 hr). Transfer from FW to SW increased gill Na+,K+-ATPase activity and Na+,K+,2Cl- co-transporter expression after 3 days. Abundance of Na+,K+-ATPase alpha-subunit mRNA and protein was unchanged. Changes in Na+,K+,2Cl- co-transporter protein were preceded by increased mRNA expression after 24 hr. Expression of V-type H+-ATPase mRNA decreased after 3 days. Transfer from SW to FW induced no change in expression of gill Na+,K+-ATPase. However, Na+,K+,2Cl- co-transporter mRNA and protein levels decreased after 24 hr and 7 days, respectively. Expression of H+-ATPase mRNA increased in response to FW after 7 days. In BW fish transferred to FW and SW, gill Na+,K+-ATPase activity was stimulated by both challenges, suggesting both a hyper- and a hypo-osmoregulatory response of the enzyme. Acclimation of striped bass to SW occurs on a rapid time scale. This seems partly to rely on the relative high abundance of gill Na+,K+-ATPase and Na+,K+,2Cl- co-transporter in FW fish. In a separate study, we found a smaller response to SW in expression of these ion transport proteins in striped bass when compared with the less euryhaline brown trout. In both FW and SW, NEM-sensitive gill H+-ATPase activity was negligible in striped bass and approximately 10-fold higher in brown trout. This suggests that in striped bass Na+-uptake in FW may rely more on a relatively high abundance/activity of Na+,K+-ATPase compared to trout, where H+-ATPase is critical for establishing a thermodynamically favorable gradient for Na+-uptake.     

Intestinal uptake of lipovitellin from brine shrimp (Artemia franciscana) by larval inland silversides (Menidia beryllina) and striped bass (Morone saxatilis)

Intestinal uptake of lipovitellin (LV) from brine shrimp (Artemia franciscana) in larval inland silversides (Menidia beryllina) and striped bass (Morone saxatilis) was described using immunocytochemistry. Polyclonal antisera were raised against two subunits of LV (LV68 and LV190). When tested by immunocytochemistry, anti-LV68 showed cross-reactivity with some of the pancreatic cells especially in inland silversides. Therefore anti-LV190 was used to localize immunoreactive LV. Inland silversides at 14 days after hatching were fed Artemia nauplii and then sampled 4, 8, 12 hr after feeding. Similar experiments were carried out by using striped bass at 5 days and 15 days of age. They were sampled at 2, 4, 8, and 12 hr after feeding. Anterior enterocytes showed no evidence of uptake; however, the brush border of the cells of inland silversides reacted with the antiserum. Posterior enterocytes took up the LV and/or, possibly, their immunoreactive breakdown products. The pattern of uptake included accumulation in supranuclear vacuoles and digestion in supranuclear vacuoles, as suggested by the decay of the immunoreactivity over time. Thus, the posterior intestine of these larval fishes is the site of uptake and digestion of LV, an important nutritive component in the food of many larval fishes; this supports earlier findings using non-nutritive marker proteins.     

Effects of glycine and alanine on short-term storage and cryopreservation of striped bass (Morone saxatilis) spermatozoa

Three experiments were designed to examine the effects of the amino acids glycine and alanine on short-term storage and cryopreservation of striped bass spermatozoa. In the first experiment, the effect of glycine on post-equilibration motility was evaluated. In the presence of 2.5 or 5.0% Me(2)SO, glycine treatments (25, 50, and 75 mM) yielded higher (P<0.05) post-equilibration motility at all equilibration times examined compared to the control. There was no difference (P>0.05) among these three glycine treatments. In the second experiment, glycine and alanine at concentrations of 25, 50, 75, or 100mM were evaluated for post-thaw motility in the presence of 2.5 or 5% Me(2)SO. When compared to the control, both the glycine and alanine treatments showed positive effects on post-thaw motility at all concentrations tested. The highest (P<0.05) post-thaw motility was achieved with 50mM glycine or 75 mM alanine using 5% Me(2)SO. No interaction (P>0.05) between Me(2)SO and glycine or alanine was observed, indicating that the effect of glycine or alanine was independent of the concentrations of Me(2)SO. In the third experiment, glycine was evaluated for sperm motility, after short-term refrigerated storage and after cryopreservation of the same refrigerated semen. Sperm motility decreased after 24h of refrigerated storage in 50mM glycine treatment and the control, when compared to fresh sperm motility. However, 50mM glycine treatment yielded higher (P<0.01) sperm motility after both 24 and 48 h of storage as well as higher (P<0.01) post-thaw motility when compared to the control. An average of 30+/-2.9% and 16+/-2.4% post-thaw motility was achieved with the 50mM glycine treatment after 24 and 48 h of refrigerated semen, respectively.     

Effects of sublethal concentrations of zinc and benzene on striped bass, Morone saxatilis (Walbaum), infected with larval Anisakis nematodes

Young of the year striped bass, Morone saxatilis , were exposed to sublethal concentrations of zinc and benzene and infected with larval Anisakis nematodes to determine the effects of these stressors on various physiological parameters. Results indicated that both pollutants and parasites significantly decreased haematocrit values. Parasites alone increased the liver somatic index, decreased haematocrits and, in the initial phase of the experiment, lowered antibody titres. Pollutants alone did not appear to significantly affect antibody titres, nor was there any difference in zinc and benzene uptake in the livers of infected and non-infected fish.     

Dietary oligonucleotides from yeast RNA influence immune responses and resistance of hybrid striped bass (Morone chrysops x Morone saxatilis) to Streptococcus iniae infection

Three feeding trials were conducted to evaluate potential immunomodulatory effects of nucleotides in the diet of hybrid striped bass. A basal diet was formulated from menhaden fish meal to contain 40% crude protein and 10% lipid. An oligonucleotide product (Ascogen P) from brewer's yeast was added to the basal formulation at the manufacturer's recommended rate of 0.5% to produce the experimental diet. Each diet was fed to four replicate groups of juvenile hybrid striped bass for seven or eight weeks in two separate trials. After Trials 1 and 2, a Streptococcus iniae bath challenge was executed to test the effects of diet on disease resistance. No significant difference in growth performance was observed between fish fed the basal and experimental diets. Body composition of whole fish, hematocrit and serum lysozyme levels were observed to be within normal ranges and not influenced by dietary nucleotides. Neutrophil oxidative radical production of fish fed the nucleotide-supplemented diet was significantly (P=0.011) higher than in fish fed the basal diet. Significantly (P<0.05) enhanced survival after exposure to S. iniae also was generally observed in fish fed the nucleotide-supplemented diet. In addition, fish fed the nucleotide-supplemented diet tended to have a higher antibody response based on microtitration agglutination; however, the difference was not statistically significant because of high variation between individual fish. Long-term (16 weeks) administration of oligonucleotides in Trial 3 failed to show enhancement of immune responses between treatments. It is concluded that dietary oligonucleotides positively influenced immune responses and resistance of juvenile hybrid striped bass to S. iniae infection.     

Allometric scaling of maximal enzyme activities in the axial musculature of striped bass, Morone saxatilis (Walbaum)

It had been suggested that the activity of anaerobic enzymes in the white muscle of fish increases exponentially with body size to meet the increasing hydrodynamic costs of burst swimming. We tested whether this relationship holds across a very large size range of striped bass, spanning a nearly 3,000-fold range in body mass. We examined the scaling of marker enzymes of anaerobic (lactate dehydrogenase and pyruvate kinase) and aerobic (citrate synthase and malate dehydrogenase) metabolism in the red and white locomotor muscles. In white muscle, we found positive scaling of anaerobic enzymes only in smaller fishes. Positive scaling of anaerobic enzymes was not found among the samples that included fishes >1,000 g despite having a sufficiently large sample size to detect such scaling. The absence of positive scaling in the white muscles of large bass suggests that they are unable to generate sufficient power to sustain relative burst swimming performance. Enzymes from aerobic pathways had activities that were mass independent in both red and white muscle. Red and white muscles were metabolically distinct except among the smallest fishes. Among young of the year, the anaerobic capacity of red muscle approached that of white muscle and also showed positive scaling. This unusual pattern suggests that red muscle might augment white muscle during burst swimming and add to the total power generated by these small fish. Maximizing burst swimming performance may be critical for small fishes vulnerable to predation but unimportant for large fishes.     

Regional variation in morphology of vertebral centra and intervertebral joints in striped bass,Morone saxatilis

The vertebral column of fishes has traditionally been divided into just two distinct regions, abdominal and caudal. Recently, however, developmental, morphological, and mechanical investigations have brought this traditional regionalization scheme into question. Alternative regionalization schema advocate the division of the abdominal vertebrae into cervical, abdominal, and in some cases, transitional regions. Here, we investigate regional variation at the level of the vertebrae and intervertebral joint (IVJ) tissues in the striped bass, Morone saxatilis. We use gross dissection, histology, and polarized light imaging to quantify vertebral height, width, length, IVJ length, IVJ tissue volume and cross‐sectional area, and vertical septum fiber populations, and angles of insertion. Our results reveal regional differences between the first four (most rostral) abdominal vertebrae and IVJs and the next six abdominal vertebrae and IVJs, supporting the recognition of a distinct cervical region. We found significant variation in vertebral length, width, and height from cranial to caudal. In addition, we see a significant decline in the volume of notochordal cells and the cross‐sectional area of the fibrous sheath from cranial to caudal. Further, polarized light imaging revealed four distinct fiber populations within the vertical septum in the cervical and abdominal regions in contrast with just one fiber population found in the caudal region. Measurement of the insertion angles of these fiber populations revealed significant differences between the cervical and abdominal regions. Differences in vertebral, IVJ, and vertical septum morphology all predict greater range of motion and decreased stiffness in the caudal region of the fish compared with the cervical and abdominal regions. J. Morphol., 2012. © 2011 Wiley Periodicals, Inc.     

Lesion induction by the plerocercoid Lacistorhynchus tenuis (Cestoda) and wound healing in the striped bass Morone saxatilis (Walbaum)

San Francisco Bay-Delta striped bass, Morone saxatilis (Walbaum), form open lesions in response to a plerocercoid infection of Lacistorhynchus tenuis (Van Beneden, 1858) (Cestoda: Trypanorhyncha). Laboratory infection experiments showed that striped bass can be infected with the plerocercoids by ingesting infected copepods. Histological sections indicated that a cellular host response was mounted early in the infection period, and that despite the leucocytic infiltration the parasites continued to develop. However, at 3 months post-infection some of the plerocercoids began to degenerate, and lesions formed at this time and 14 months post-infection. Open lesions in adult striped bass collected from the field took 2 months to heal and were detectable for at least 22 months. Regeneration of the muscle tissue did not occur although the wound completely healed externally.     

Effects of dimethyl sulfoxide and glycine on cryopreservation induced damage of plasma membranes and mitochondria to striped bass (Morone saxatilis) sperm

Intact plasma membrane and functional mitochondria are important attributes for the fertilization capacity of fish sperm. In the present study, dimethyl sulfoxide (Me(2)SO) and glycine were investigated in an effort to improve plasma membrane integrity and mitochondrial function in cryopreserved striped bass (Morone saxatilis) sperm. Prior to freezing, no concentration of Me(2)SO (2.5, 5 or 10%) was found to affect (P>0.05) the integrity of plasma membranes after sperm were exposed for 10 min. However, mitochondrial function decreased (P>0.05) with increasing Me(2)SO concentration. Both fluorescent staining and microscopic examination of the ultrastructure of post-thaw plasma membranes indicated that with increasing Me(2)SO concentration, plasma membranes were better protected, and 10% Me(2)SO had the highest percentage of sperm with plasma membranes intact. However, sperm mitochondrial function decreased (P>0.05) with increasing Me(2)SO concentration. The inverse relationship between plasma membrane integrity and mitochondrial function, given the Me(2)SO concentration, suggests that care must be taken to select Me(2)SO concentration that will maximize the protection of both plasma membranes and mitochondrial function. The addition of glycine to the cryomedia increased (P<0.05) the percentage of sperm with post-thaw functional mitochondria and ATP content. However glycine did not provide (P<0.05) protection to post-thaw plasma membrane integrity. The highest percentage of sperm with both intact plasma membranes and functional mitochondria was obtained with 7.5% Me(2)SO and 75 mM glycine.