수온조절 (6, 9, 12, 15, 18, 21, 24, $27{circ}^C$)에 의해 유도된 멍게의 물렁증 진행에 따른 생리학적 특성을 연구하였다. 수온조절에 의한 물렁증 유도율은 수온 $15^{circ}C$에서 가장 높았으며, $24^{circ}C$에서 가장 낮았다. 물렁증은 피낭 색깔 및 탄성을 기준으로 S0, S1, S2, S3의 4단계로 구분하였다. 정상개체와 물렁증을 가진 개체들 사이에서 산소소비율과 여수율은 유의한 차이를 보였다. S0에 비해 S3단계에서 혈구 구성비의 가장 뚜렷한 변화는 multi-vacuole cell은 약 1/2 감소하였으며, morula cell은 약 10배 증가하였다. 기관계 구조의 변화는 피낭, 수관, 새낭, 육질부, 소화선에서 상피세포의 변성, 미세섬유의 변성, 혈구의 증가 및 근섬유의 변형이 확인 되었다. 이러한 모든 특징들은 멍게의 정상적인 생리학적 기능에 영향을 미칠 수 있다.
In this study, we investigated the changes in the physiological and histological traits of a sea squirt (Halocynthia roretzi) with the emergence of the soft tunic syndrome induced by the water temperature control (6, 9, 12, 15, 18, 21, 24 and $27^{circ}C$). It was observed that the induction rate of the soft tunic syndrome was highest at $15^{circ}C$, but lowest at $24^{circ}C$. Based on the tunic color condition and contraction strength, the whole process were classified into 4 stages as S0, S1, S2 and S3. Interestingly, there were significant differences in oxygen consumption and filtration rate were observed during S0-S3. The most distinctive aspects were change of blood cell composition at stage S3, whereas multi-vacuole cell ratio was decreased by 1/2 and morula cell ratio expanded about 10 times during S0-S3. Further, change of organ structure started following the syndrome such as degeneration of epithelial cells, microfilaments, increment in hemocytes and damage in muscle fiber have been detected in tunic, siphon, branchial sac, body wall musculature and pyloric gland. Briefly, our study results indicated that the normal physiological functions of the sea squirt can be affected due to the soft tunic syndrome induced by water temperature.
