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- Developmental responses of sterlet (Acipenser ruthenus) to temperature modulation with insights into intestinal and morphological traitsPublication . Jafari Pastaki, Naghmeh; Abdollahpour, Hamed; Falahatkar, BahramSturgeon fish are highly valued in aquaculture, relying on optimal water temperatures for health and productivity. In this study, three temperatures were considered including group A: (ambient temperature, 18 ºC), group B: 21 ºC and group C: 27 ºC to investigate the intestine morphology, growth performance, meristic and morphological traits of sterlet. For this purpose, the temperature was gradually increased, and the larvae were exposed at the desired temperature 32 days after fertilization (dpf) and then returned to ambient temperature until 64 dpf. The growth results indicated that temperature manipulation in the first two months of the life can improve growth. Examining the morphologic and meristic characteristics showed that the increase in temperature accelerates fin and skeletal development, in which the calcified structures such as lateral scutes, distal radials and spine of pectoral fin were detected in group C. The development of villi’s was higher in group C than the other groups at 32 dpf and 64 dpf. Therefore, the results of this study demonstrated that short-term thermal tolerance of sterlet has a positive effect on growth performance, morphological traits and intestine development. Proper temperature control enhances sturgeon aquaculture in the first two months.
- Evaluation of superworm (Zophobas morio) larvae meal as a fish meal substitute in juvenile stellate sturgeon (Acipenser stellatus) dietsPublication . Lebria, Arash; Langroudi, Hadi Ershad; Pajand, Zabih Ollah; Sajjadi, Mirmasoud; Abdollahpour, HamedThis study aimed to evaluate the effects of dietary inclusion of superworm (Zophobas morio) larvae meal (SWM) on growth performance, hematological parameters, blood biochemical parameters, proteolytic enzyme activity, and body composition in juvenile stellate sturgeon (Acipenser stellatus). A total of 120 juvenile fish (initial body weight: 28.08 ± 0.13 g) were randomly assigned to four dietary treatments in triplicate groups. Experimental diets were formulated to replace 0% (control), 10% (SWM10), 20% (SWM20), and 30% (SWM30) of fish meal with SWM, maintaining isonitrogenous (45.27% protein) and isoenergetic (19.50 MJ/kg) profiles. Fish were hand-fed to apparent satiation three times daily over an 8-week period. Growth performance data indicated that up to 10% SWM inclusion did not significantly affect final weight, weight gain, or condition factor compared to the control (p > 0.05). However, 20% and 30% inclusion levels resulted in significantly reduced growth performance (p < 0.05). Hematological analysis showed that WBC counts were significantly higher in all SWM-fed groups (16.2–19.3 ×10 ³/mm³) compared to the control (13.9 ×10 ³/mm³), with neutrophil percentages also elevated (16.3–17.2% vs. 13.7% in the control) (p < 0.05). No significant differences were observed in RBC count, hemoglobin, hematocrit, MCV, MCH, or MCHC (p > 0.05). Biochemical results showed that triglyceride levels were significantly elevated in the SWM30 group (p < 0.05), while cholesterol levels were significantly lower compared to the control (p < 0.05). Serum glucose level remained unaffected across treatments (p > 0.05). Proteolytic enzyme analysis indicated a significant reduction in trypsin activity in fish fed the SWM30 diet (p < 0.05). Whole-body composition analysis revealed that increasing SWM inclusion significantly decreased carcass protein, moisture, and ash contents, while lipid content increased, with the highest fat level observed in the SWM30 group (p < 0.05). Overall, the findings suggest that superworm larvae meals can be included in the diet of juvenile stellate sturgeon at levels up to 10% fishmeal replacement without adverse effects on growth, hematological parameters, blood biochemistry, or proteolytic enzyme activity.
- The antithyroid drug methimazole as an emerging aquatic contaminant: physiological and reproductive disruption in female goldfish (Carassius auratus) and partial mitigation by thyroxinePublication . Abdollahpour, Hamed; Karimzadeh, Milad; Jafari Pastaki, Naghmeh; Zamani, HosseinaliThyroxine (T4), a key thyroid hormone, plays a crucial role in regulating growth, metabolism, and reproduction in fish, whereas methimazole (MMI), a thyroid peroxidase inhibitor, can disrupt these processes by inducing hypothyroidism. This study investigates thyroid-modulating compounds' physiological and reproductive effects on the growth and development of mature female goldfish (Carassius auratus). A total of 240 adult female goldfish were divided into four treatment groups: control (coconut oil), T4, MMI, and T4+MMI (combined). The fish were acclimatized for four weeks before receiving injections of the respective compounds. Growth performance, blood biochemistry, thyroid hormone (THs) levels, oocyte development, and liver histology were evaluated over a 28-day experimental period. Results indicated significant differences in growth indices, with the T4 group showing the highest weight gain, specific growth rates, and lowest feed conversion ratio (P < 0.05), while the MMI group exhibited the lowest growth parameters. Blood glucose, triglyceride, and total protein levels were significantly elevated in the T4-treated group, whereas cholesterol was reduced (P < 0.05). Plasma T3 and T4, were highest in the T4 group and lowest in the MMI group. Histological analysis revealed advanced oocyte maturation in the T4 group, with a higher proportion of oocytes at the O4 stage, while the MMI group showed delayed development, with most oocytes remaining at the O2 stage. The T4+MMI group exhibited intermediate effects, with some improvement in oocyte development relative to the MMI group. Hepatic histopathology demonstrated normal liver structure in the control and T4 groups, while severe hepatic alterations, including necrosis and vacuolation, were observed in the MMI group. The T4+MMI group displayed intermediate liver damage. These findings demonstrate that the pharmaceutical methimazole, an emerging aquatic contaminant, acts as a potent endocrine disruptor, inducing hypothyroidism that severely impairs growth, metabolic homeostasis, and reproductive maturation in fish. The partial mitigation by thyroxine suggests potential complex interactions in environments contaminated with multiple bioactive compounds. This study underscores the significant ecological risk of antithyroid drugs in aquatic ecosystems and contributes critical data for environ mental risk assessment.
- Size-dependent salinity tolerance in juvenile stellate sturgeon (Acipenser stellatus): physiological and histopathological responsesPublication . Pajand, Zabih Ollah; Hosseinnia, Esmaeil; Jafari Pastaki, Naghmeh; Hallajian, Ali; Yousefi, Ayoub; Lebria, Arash; Ashori, Alireza; Abdollahpour, HamedWe investigated the physiological, endocrine, and histological responses of juvenile stellate sturgeon (Acipenser stellatus) to salinity challenge across four weight classes (0.89 ± 0.21, 2.01 ± 0.32, 4.84 ± 0.39, and 9.07 ± 1.47 g; mean ± S.E.) and four salinity levels (0, 4, 8, and 12 ppt) over acute to chronic exposure (3–624 h). A total of 4800 juveniles were used across four sequential experiments, with 100 ± 5 fish per tank (12 tanks per experiment). A replicated factorial design (three tanks per treatment) enabled robust assessment of ionoregulation, stress response, and tissue integrity. Plasma osmolality increased from approximately 230 to 266 mOsm kg− 1 during early exposure, followed by progressive convergence toward a narrower physiological range (≈251–284 mOsm kg− 1 ) at 624 h, indicating partial osmotic compensation. This adjustment was driven primarily by sodium, which exhibited the strongest salinity- and size-dependent response, confirming its central role in extracellular osmotic regulation. In contrast, potassium displayed pronounced size-dependent dysregulation, with markedly elevated concentrations in fish 3 g maintained values within or near the physiological range. Cortisol dynamics revealed a clear ontogenetic shift in stress responsiveness. Smaller juveniles (3 g) demonstrated more efficient recovery, with the 5–10 g group achieving ~92% recovery by 96 h, compared to only ~45% in the smallest size class. These endocrine patterns were consistent with ionoregulatory performance and further support a size-dependent transition in physiological resilience. Histopathological analysis corroborated systemic findings. Histopathological analysis using a semi-quantitative scoring system (0–4) revealed significant size- and salinity-dependent tissue alterations. Gill tissues showed lamellar fusion, epithelial lifting, hyperplasia, necrosis, and hemorrhage, with more severe lesions in smaller juveniles at intermediate to high salinities. Kidney tissues exhibited glomerular expansion, tubular degeneration and obstruction, congestion, hemorrhage, and hemosiderin deposition, with lesion severity generally decreasing with increasing body size. These histological patterns were consistent with physiological and endocrine responses and reflected greater structural resilience in larger juveniles under salinity stress. Collectively, these integrated responses identify an empirical transition zone at approximately 3 g under the tested conditions, below which juveniles exhibit limited capacity to maintain physiological homeostasis under salinity challenge. Above this threshold, fish display more effective physiological regulation, resulting in better ion balance, lower stress, and improved tissue integrity. Together, these findings provide mechanistic evidence for size-based acclimation protocols, gradual salinity transitions, and optimized release strategies to enhance survival and performance in aquaculture and stock enhancement programs.