Abstract:Genetics can help us understand why identical circumstances can elicit different behavioral responses among individuals. It is widely accepted that Kappa Opioid Receptor 1(OPRK1) gene is involved in modulating behavioral performance in response to environmental conditions. The OPRK1 gene has been intensively studied; however, no studies have addressed the effect of OPRK1 gene polymorphisms on behavioral traits in sika deer (Cervus nippon). This study investigated the association between single nucleotide polymorphisms (SNPs) in the OPRK1 gene and behavior traits of sika deer in the Ping-Shan-Tang farm (25 deer) and Zhu-Yu-Wan Park (23 deer), Yangzhou city, Jiangsu province, China. The deer on Ping-Shan-Tang farm were housed in four 20 × 10 m paddocks with shelters of mantle. In Zhu-Yu-Wan Park, the deer were roamed in a fenced paddock of grasses, shrubs and trees (100 m × 50 m). All deer were marked by ear-notches and collar-tags for easy identification and were aged between 3 and 7 years. The study was conducted in two phases: from July to December, 2006, and again from Feb to June, 2007, during all weather conditions. Focal-animal sampling and all-occurrence recording was used to determine the period of time spent on each behavior. Eight hours were spent collecting data for per day, including weekdays and weekends. Four days were used to observe every week. The observations were conducted at the same times each day from 8:30 a.m. to 4:30 p.m. and subjects were sampled in a different order each day (using random numbers). After all observations, blood samples ( 10 mL) were collected from the jugular vein using vacuum tubes with acid citrate dextrose anticoagulant and then stored at -20℃. Genomic DNA was extracted from whole blood using a standard phenol /chloroform protocol, dissolved in sterile water at a concentration of 100 ng /μL and then kept at -20℃ until use. PCR amplification and SSCP analysis of the OPRK1 gene were performed using nine pairs of primers. Two pairs of primers (P-5 and P-9) amplified polymorphic fragments. Three genotypes were identified by SSCP for each of the fragments amplified by the primer pairs. The least-square analysis and post-hoc multiple comparison were employed to detect the relationship between the primer of P-5 and P-9 genotypes and the behavior traits using SPSS 14.0 software. The results showed that the EE, EF and FF genotype of the P-5 primer had significantly difference on grooming behavior, and significant difference was found between EE and FF genotype with other behavior (P<0.05). But for the other five behaviors, no significant difference was detected. Highly significant differences in relaxing behavior were produced between the GG and GH genotypes of the primer P-9 fragment (P<0.01). There was a significant difference among the GG, GH and HH genotypes with respect to observing behavior (P<0.05). The significant difference results were also found on the grooming behavior between HH and the other two genotypes (P<0.05). We conclude that polymorphisms in the OPRK1 gene may be involved in some aspects of behavioral traits in sika deer.