Feeding Strategies for Adapting Lake Sturgeon (Acipenser fulvescens) Larvae to Formulated Diets at Early Life Stages.

Cost-effective feeding management is required to support conservation hatcheries for lake sturgeon (Acipenser fulvescens), an ecologically important species in the Great Lakes region. This study investigated an approach to transition lake sturgeon larvae from live feed (Artemia) to formulated feed and its effect on growth performance, survival, and response to acute hypoxia stress. The first experiment showed that sturgeon had similar (p > 0.05) growth and survival when fed Artemia or the combined feeding of Artemia with the commercial diet (crude protein, 551 g/kg diet). Feeding solely on the commercial or lab-made (crude protein, 491 g/kg diet) diet significantly reduced growth and survival (p < 0.05). In the second experiment, the growth performance of sturgeon (14 days post-hatch, DPH) fed with either Artemia only or combined feeding different feeding durations of two, three, and four weeks followed by a complete transition to the commercial diet. At the end of six weeks, the 3- and 4-week combined feeding periods resulted in significantly higher body weight and survival compared to the 2-week combined and the Artemia only feeding treatments. In the last experiment, sturgeons (27 DPH) were fed only with Artemia or combined feeding of Artemia with the commercial diet for four weeks followed by the complete transition to the commercial diet for two weeks. Eighteen fish from each treatment were investigated the response to acute hypoxic conditions (gradual decrease in dissolved oxygen level from 8 to 2.3 mg/L at the rate of 1 mg/L per hour). When the dissolved oxygen was between 3 and 4 mg/L, the mortality rate of the combination-fed sturgeon (11.7%) was significantly lower than those fed only Artemia (83.3%). These results clearly demonstrate that a commercial diet can partially replace Artemia at early life stages to improve growth, survival, and hypoxia tolerance and thus its co-feeding with Artemia is recommended.

Characterization and evaluation of sex-specific expression of suppressors of cytokine signaling (SOCS)-1 and -3 in juvenile yellow perch (Perca flavescens) treated with lipopolysaccharide.

The suppressor of cytokine signaling (SOCS) proteins are a family of intracellular proteins that are centrally involved with vertebrate growth, development and immunity via their effects as negative feed-back regulators of cytokine (and hormone) signaling. The genes for SOCS-1 & -3 were cloned, sequences analyzed and expression patterns examined in the commercially-important teleost, yellow perch (Perca flavescens). The deduced (mature) proteins for yellow perch (yp)SOCS-1 and (yp)SOCS-3 consist of 211 and 205 amino acids, respectively. Functional domains such as the Src homology-2 (SH2) and SOCS-box were present in ypSOCS-1 and ypSOCS-3 and these domains were well conserved between teleost species. Sequence analysis showed that ypSOCS-1 & -3 share highest homology (among similar teleost sequences), to the stickleback (Gasterosteus aculatus) SOCS-1 & -3 protein homologs. To investigate sex-specific expression of the ypSOCS-1 and ypSOCS-3 mRNAs, juvenile male and female yellow perch were immunologically challenged with a single injection (10 µg/g bw) of lipopolysaccharide (LPS) and tissues (gill, head kidney, kidney, liver and spleen) were sampled over a 48-h time-course. Quantitative real-time PCR analysis showed that ypSOCS-1 & -3 were expressed in all tissues examined and at all sampling time-points. LPS injection significantly induced ypSOCS-1 & -3 mRNA levels in gill, head kidney, liver, kidney and spleen, with maximal induction occurring at 6 h post-injection in each tissue. By 48-h post-injection, expression levels for ypSOCS-1 & -3 mRNAs approached, or reached, control levels in all tissues examined. While there were statistical interactions among variables (treatment, time and sex) for ypSOCS-1, we only found a main effect of sex on SOCS-3 mRNA expression in head kidney with higher copy numbers occurring in males than in females treated with LPS. Sexually-dimorphic expression of SOCS-1 or -3 mRNA has not been examined, or described, in a teleost. Our findings suggest the involvement of the SOCS genes in the yellow perch immune response and that differences among the sexes are evident and should be explored further.

Karyotype characterization of the lake sturgeon, Acipenser fulvescens (Rafinesque 1817) by chromosome banding and fluorescent in situ hybridization.

A karyotype analysis using several staining techniques was carried out on the North American lake sturgeon, Acipenser fulvescens. The chromosome number was found to be 2n = 262 +/- 6. A representative karyotype of 264 chromosomes was composed of 134 meta- and submetacentrics, 70 telo- and acrocentrics, and 60 microchromosomes. The constitutive heterochromatin, revealed by C banding, was localized in various positions on several chromosomes, including microchromosomes. The signals of fluorescent in situ hybridization (FISH) with a HindIII satellite DNA probe were visible as centromeric heterochromatin blocks on 48 chromosomes. The telomeric repeat (TTAGGG)n detected by FISH was localized at both ends of all chromosomes and two chromosomes were entirely marked. Fluorescent staining with GC-specific chromomycin A3 showed recognizable fluorescent regions, whereas a more uniform base composition was revealed by the AT-specific 4',6-diamidino-2-phenylindole (DAPI). After silver staining, the active nucleolar organizer regions (NORs) were detected on 12 chromosomes. FISH with the 5S probe showed four signals on four small chromosomes. Our data suggest that A. fulvescens is a tetraploid species.