SEX-SPECIFIC VARIATION IN COMPLETE BLOOD COUNT PARAMETERS AND BIOMETRIC TRAITS IN WILD RODENTIA: IMPLICATIONS FOR HORMONAL REGULATION OF ERYTHROPOIESIS AND SOMATIC GROWTH

Abstract

Haematological and morphometric parameters may provide crucial information on the physiological state, immunological status and somatic diversity among wild rodents of different sexes. However, these features may also be affected by the environment and biology. The present study compared the complete blood count (CBC) parameters and morphometric characteristics of wild brown (Rattus norvegicus) and black (Rattus rattus) rats from Sargodha, Punjab, Pakistan with respect to sex. During April-July 2024, a total of 65 rodents were collected from different localities in Sargodha, of which 35 were brown rats and 30 were black rats. A dichotomous key was used for identification of the specimens, and morphometric characters were measured with a Vernier calliper and digital balance. Cardiac puncture samples were taken in EDTA tubes, and major hematological parameters were measured. A two-sample t test was used to make statistical comparisons in Minitab. The morphometric analysis revealed a significant sexual difference in body weight and various body dimensions, with higher values for some of the body dimensions in males than in females. A comparison of the hematological profile showed few differences between the sexes. There were no significant sex differences in most leukocytic and erythrocytic parameters in brown rats, except for mean corpuscular hemoglobin (MCH), which was significantly higher in males (21.60 ± 1.10 pg) than in females (18.62 ± 0.76 pg; p = 0.02). The mean RBC, hemoglobin and WBC values were higher in the male black rats, while the MCV and MCHC values were higher in the female black rats. The monocyte percentage was significantly different between brown and black rats (p = 0.001), and most of the other CBC parameters were comparable. The results suggest that the sex-associated variation was more pronounced in selected morphometric traits than in the hematological profile as a whole. However, the marked variation in MCH difference between brown rats indicates a possibility for sex-related differences in erythrocyte characteristics, but no hormonal, age, reproductive or nutritional factors were directly tested. The results provide background data regarding hematological and biometric data of wild Rattus populations in the study area and emphasize the need to account for sex and environmental factors when evaluating physiological variation in rodents.