Serum chemistry, thyroxine concentration, and blood cell morphology of wild, young Blackchin Guitarfish Glaucostegus cemiculus sampled on the eastern Mediterranean coastline.

Objective: The Blackchin Guitarfish Glaucostegus cemiculus is endemic to the Mediterranean Sea and is critically endangered, but relevant routine laboratory data are unavailable. Our objectives were to determine the packed cell volume (PCV), comprehensive serum chemistry analytes, and serum total thyroxine (sTT4) concentration; compare serum albumin and serum globulin concentrations as measured by two different methods; and describe the blood cell morphology of healthy, free‐ranging Blackchin Guitarfish. Methods: Wild Blackchin Guitarfish were captured using a seine net. Blood samples for serum chemistry and hematological analyses were obtained and measured using routine laboratory methods. The fish were tagged and released. Result: This study included 43 Blackchin Guitarfish (17 males and 26 females) that were younger than 6 months as estimated based on total length and body weight. The median PCV (n = 23) was 22% (minimum–maximum [min–max] = 15–25%). Median sTT4 (n = 10) measured by chemiluminescence immunoassay was 7.86 nmol/L (min–max = 7.52–9.57 nmol/L). The study included a comprehensive, 25‐analyte serum chemistry analysis (e.g., serum iron and unbound and total iron‐binding capacity) and a morphological description of all blood cells. Serum electrophoresis (SEP; n = 13) yielded a consistent serum albumin‐migrating protein fraction and four globulin fractions. Serum electrophoretograms corroborating these results are presented. Conclusion: In Blackchin Guitarfish, the serum albumin‐migrating fraction measured by SEP combined with serum total protein concentration yields a much higher albumin concentration compared to that measured by bromocresol green spectrophotometry. The true identity of this albumin‐migrating fraction remains to be identified. The analytes' calculated 2.5–97.5% interpercentile intervals should be considered as reference intervals applying to Blackchin Guitarfish of similar age but should be applied cautiously to adult fish. Impact statementThis study incudes novel comprehensive basic laboratory data describing young, healthy Blackchin Guitarfish, a critically endangered species in the Mediterranean Sea. The findings significantly increase the scientific knowledge of this species, potentially contributing to its conservation. [ABSTRACT FROM AUTHOR]