Masaaki Yanase

Vitamin B12 as a Factor in the Environment of Bivalves-I

It has been reported that the vitamin B12 content of bivalves, and of starfish which devour bivalves, is higher than that of fish or other aquatic animals. Recent studies have shown that vitamin B12 will affect the growth of Porphyra tenera and relate to the development of “red tide”. In view of these facts, we made a study of vitamin B12 as one of some means to analyze the environment of the shallow water clam bed. In this experiment we measured the vitamin B12 content of Tapes japonica and Meretrix meretrix lusoria, the bottom substances in which they lived, the fine deposits in the hollow of ripple marks and the plankton which are the food of clams. Vitamin B12 content was determind by Euglena method added 1mg/cc acid hydrolysed casein to HUTNERs basal medium, and each sample were digested by trypsin before hot water extraction. Results obtained were as follows: 1. Vitamin B12 content in the soft body of Tapes japonica and Meretrix meretrix Zusoria is high before and during spawning, and low after spawning. In Tapes japonica, there is a tendency for individuals that live off the coast to be higher in vitamin B12 content than those that live near the coast; moreover individuals cultured by the hanging method are higher in vitamin B12 content than those raised in the above-mentioned benthic environment. In Mere-trix meretrix Zusoria, however, the above described tendency is not clear. Further, vitamin B12 content of Tapes japonica is higher than that of Meretrix meretrix lusoria during every month of the year (see Tables 1, 2, & Fig. 1). 2. Vitamin B12 content of the sandy bottom in the offshore areas is higher than in the shallow coastal beds, and vitamin B12 content of same substances divided into three vertical layers is higher in the upper and middle layers and poorer in lower layer. Fine deposits on the hollow of ripple mark are higher in Vitamin B12 than in the sandy bottom areas mentioned above. Vitamin B12 content in zooplankton (Copepoda) is higher than that of phytoplankton (Coscinodiscus sp. or Thalassiothrix sp.) (see Table 3).

Studies on Vitamin B12 of Aquatic Animals-IV

Predatory activity of the yellow starfish, Asterias amurensis versicolor Sladen, has teen so rampant in clam culture grounds in the Tokyo Bay that commercial harvest of clams for the present season and in the future has been seriously threatened. In the course of investigating the situation, attention has been attracted to the vitamin B12 contents of the asteriod which was expected to be as high as its food, shell-fish, in view of knowledge obtair. d p eviously1). Of numbers of individuals collected from the invaded area in February and March, 1954 the samples which were apparently in a medium size presented the weight by anatomical parts as shown in Table 1. The vitamin B12 contents have been determined by microbiological assay using Euglena as the test organism. As the result it has been revealed that the viscera, and especially the pyloric caecum, contain vitamin B12 by far more than those of other marine animals, except ?? few cases, reporte1 in the preceding papers1) (Table 2). Since vitamin B12 can be easily extracted from the starfish by enzymic digestion, as has been demonstrated (Table 3), it is suggested that this echinoderm may be utilized as a potential source of vitamin B12 for human consumption as well as for feeding of livestock, providing an adequate mcthcd for industrial prccessing is established. And such utilization, if avilable on industrial scales, will have an effect, at the same time, to alleviate depredation of the starfish upon commercially important shell-fish in the area.