SEGREGATIVE MIGRATION OF DALL'S PORPOISE (PHOCOENOIDES DALLI) IN THE SEA OF JAPAN AND SEA OF OKHOTSK

Dall's porpoises from the Sea of Japan population taken by a dolphin fishery vessel were examined. Estimated body lengths at sexual maturity were similar to those for the truei -type population off the Pacific coast of Japan but larger than those for the offshore dalli -type in the North Pacific. The Sea of Japan population is known to migrate to the Pacific coast of Japan through Tsugaru Strait and to the Sea of Okhotsk through Soya Strait in summer. From the difference of catch composition, individuals of different reproductive status in this population are considered to have different patterns of summer migration. Most of the individuals which migrate into the Pacific Ocean through Tsugaru Strait are sexually immature, while those migrating into the Sea of Okhotsk are mature. The Sea of Okhotsk is thought to be a breeding area for this population. The calving season is estimated to be May through June, which is earlier than that of the truei -type off the Pacific coast of northern Japan. This may be an adaptation to lower water temperatures in the Sea of Japan during winter.     

GEOGRAPHIC VARIATION AND SEXUAL DIMORPHISM IN THE SKULL OF DALL'S PORPOISE, PHOCOENOIDES DALLI

Abstract: Two hundred and eighty-nine skulls of Dall's porpoises from the North Pacific Ocean, Sea of Japan, Sea of Okhotsk, and Bering Sea were investigated morphometrically. A clear pattern of geographic variation was found in overall size of the skull. In the North Pacific, overall skull size became gradually smaller eastward from the coast of Japan to the offshore eastern Pacific, and it became larger again off the coast of California. Specimens from the Sea of Japan-Okhotsk and Bering Sea had larger skulls than those from the central North Pacific. The distribution of primary productivity corresponds well with this pattern of geographic variation, suggesting that quantity of food might affect the overall size of Dall's porpoise skulls. By canonical discriminant analyses, about 70% (male) and 90% (female) of specimens of the Sea of Japan-Okhotsk population were distinguished from those of other populations. This agrees with the results of genetic studies.     

SUMMER FEEDING HABITS OF DALL'S PORPOISE, PHOCOENOIDES DALLI, IN THE SOUTHERN SEA OF OKHOTSK

Stomach contents were analyzed from 85 Dall's porpoises, Phocoenoides dalli , taken in the southern Sea of Okhotsk during the summer of 1988. Thirteen species of fish and five species of cephalopods were identified. Fishes comprising 9 families were predominant and made up 79.9% of the total number of prey, with an overall occurrence in the stomachs of 100%. Three families of cephalopods made up 20.1% of the total number of prey ingested, with an overall occurrence of 74%. The Japanese pilchard, Sardinops sagax melanostictus , was the primary prey and represented 72.0% of the total prey in 97.3% of the stomachs examined. The gonatid squid, Berryteuthis magister , ranked second and made up 16.9% of the total prey in 61.6% of the stomachs. Walleye pollock, Theragra chalcogramma , was the third most abundant prey item consumed and represented 6.0% of the total, with an occurrence of 53.4%. Composition of the sample by the calculated total mass and caloric intake supports the numeric findings on the relative importance of the three major prey species to the DaIl's porpoise diet. The Japanese pilchard was clearly dominant using these indices and constituted 65.4% of the total mass and 80.7% of the caloric intake. Berryteuthis magister made up 26.8% of the mass and 15.5% of the caloric intake. Walleye pollock contributed the least to the diet with 7.9% of the total mass and 3.8% of the caloric intake. Volumetric data indicate that porpoises are feeding heavily on Japanese pilchard throughout the daylight hours. Berryteuthis magister was probably fed upon in the late night or early morning hours. Occurrence of both Dall's porpoise and Japanese pilchard in the coastal waters of the southern Sea of Okhotsk is seasonal. The summer movements of Dall's porpoise into this region may be related to the seasonal migration and abundance of the Japanese pilchard.     

损伤视神经后斑马鱼视网膜神经节细胞数量和分布的变化

中枢神经系统的再生是神经科学领域的一个重要课题。鱼类和两栖类的视神经作为中枢神经系统的一部分,具有再生的能力。已知在损伤视神经后,对与视神经纤维直接相连的视网膜神经节细胞的形态结构,数量和分布等产生一系列的影响。视神经再生过程中细胞学研究在很大程度上依赖于示踪方法和其它技术的发展,结合光镜和电镜,它们仅对神经细胞末梢的精细结构和神经细胞间突触连接构筑等研究较准确详实,但对视网膜神经节细     

CTx促进远端视神经切断后视网膜节细胞轴突再生与c-Jun表达的关系

目的探讨霍乱毒素(CTx)促进成年金黄地鼠视神经远端切断后视网膜节细胞(RGCs)轴突再生与c-Jun的表达关系。方法远端切断视神经并对接一段自体坐骨神经,玻璃体内注射CTx及/或植入小段坐骨神经分支(SN)。动物随机分为AG CTx组;AG SN组;AG SN CTx组,各组动物分别存活4W,用荧光金(FG)逆行标记和c-Jun免疫荧光组织化学双标法观察轴突再生的RGCs内c-Jun表达情况。结果再生RGCs内有c-Jun蛋白表达,玻璃体内给予CTx或植入SN组RGCs表达c-Jun的再生RGCs分别为35·8±9·57和32·2±7·25个,约占其再生总数的94%及90%,两组相比无显著性差异(P>0·05);CTx与SN联用组c-Jun阳性再生的RGCs为150·2±43·92个,占再生总数的97%,与前两组相比,均有显著性差异(P<0·05)。结论视神经远端切断后约90%以上的再生RGCs有c-Jun表达,提示c-Jun表达与视神经远端受损后节细胞轴突再生密切相关,CTx及外周神经对RGCs轴突再生及c-Jun表达有协同促进作用。