An attempt was made to determine the oxygen consumption rate of the pond-cultured eel in the resting state by means of a flowing water system. On the basis of the fact that the eel, being possibly thigmotactic, remains almost motionless when a tube of appropriate dimensions is provided for it, glass tubes, which were varied in diameter and length according to the size of fish used, were employed as respiration chambers in the present investigation. The fish used in experiments were pond-reared eels ranging in body weight from about 5 to 270 g. Immediately after being taken from eel-culture ponds at about 24 hours after feeding, fish were placed in respiration chambers separately. All experiments were carried out in July at about 25°C. Succesive measurements of the oxygen uptake over a period of about a day, revealed, in almost every case, that during the early part of the experiment the rate of oxygen uptake was considerably high, but later (about 5 hours after introduction of the fish) it settled down to a lower value which remained more or less constant until it again fluctuated widely and irregularly after the lapse of about 15 hours. In the present study such a steady rate of oxygen consumption in the middle of the experiment was taken as an estimate of the resting rate of oxygen consumption. The rate of oxygen consumption of the pond-cultured eel at 25°C. thus obtained are summarized as follows; Body weight (g) 5 10 20 50 100 150 200 300 Oxygen consumption (cc./hr.) 0.75 1.2 2.0 3.8 6.2 8.3 10.2 13.5 Oxygen consumption (cc. /kg. /hr.) 150 120 100 76 62 55 51 45 These values give a straight line when the logarithm of the rate of oxygen consumption (cc./hr.) is plotted against the logarithm of the body weight. The slope of the line has a value of approximately 0.7.
The family Paralepididae is one of the largest in the order Iniomi, consisting of seven genera and forty-eight known species (HARRY, 1953, p.230-231). Two genera and three species of this family are hitherto known from Japanese waters: Listidum japonicum TANAKA (Japanese name Hadakaeso), Listidum prolixum HARRY (Japanese name Namehadaka) and Notolepis coruscans (JORDAN and GILBERT) (new Japanese name Hikarieso). Recently I obtained two specimens belonging to this family. They differ markedly from three known species. I examined and made clear that they are M. barysoma of only one sepcies in the genus Magnisdis recorded from off California by HARRY (1953). Description of this rare species is given in the present paper. They were each almost of the same body length, but one specimen was in bad condition as follows. The head was damaged, its left side was taken off except the fourth and the fifth gill-arches. Data of the specimens are as follows. 1. 50 mm. in total length. collected off the east of Erimo, Hokkaido, in a bottom trawl without otter board at 800-930 meters depth, on board the our office's trust examination boat “No.8 Choun Maru, ” during 20-24 June 1957, by technical expert Tatsuo YASUI. 2. Body length is almost the same in the former, data unknown, but it has impressed me as obtained from the adjacent water of Hokkaido on the other our office's trust examination boat in those days collected the former. Examined specimens almost well agree with HARRY'S descripion. But their body proportions and the number of fin rays somewhat differed from his specimens as shown in table 1.
Following the same experiment conducted by the writer in 1947, the effect of varied date of initial feeding on fish fry was examined on the growth rate and the color change of “wakin” gold-fish, Carassius auratus in 1949 and 1950. The fish specimens, the same brood of fry hatched out on the same day, were kept in 4 (1950) and 5 (1949) lots under the probable equivalent condition in each year ;they were fed by Moina sp.and some prepared food in an excess amount daily (Table 1). In the experiment of 1950 the volume of water carrying each lot of fish was differed proportionally to the number of fish. The result of the checking of reared fish was shown in Tables 2 and 3. It was found clearly that the differential growth of fish among the lots of each year showed nearly corresponding rate to the varied date of the first feeding, whether in total weight of the lot, growth of individuals and the survival rate of the group.The best growth as far as the total weight concerned of fish, as expected, was found in the lot whose feeding started on the day of their hatching. The change of coloration from larval dark color to the colorless or reddish phase of gold-fish was not apparently reflected by the date of initial feeding.
In the present note, the authors presented the data on the geographical variation in the number of anal fin rays in the wild populations of the Medaka, Oryzias latipes, collected at 59 localities in Japan, Formosa and China.
1. The pressure change in the oral cavity by the normal respiration was about 2mm. H2O. 2. The so-called cleaning motion was divided into three types according to the feature in the pressure change and operculars movement (see text). 3. The once elevated or lowered pressure level by the so-called cleaning motion recovers gradually in the course of several cycles of the following normal respiretion. 4. By the spitreflex a sudden ascent and descent down to the normal level was recorded. 5. The removal of the oral valves resulted in almost 50 % decrease of the pressure change. That of the opercular valves did not produce any remarkable change. 6. From results above the following was concluded. a) The name “cleaning” is not suitable for this motion. b) The pressure within the oral cavity does not stationarily balance with that of the outermedium during the normal respiration. The author wishes to express his heartful thanks to Prof. SUYEHIRO for constant guidance in the course of this work. Thanks are also due to Assist. Prof. HIBIYA for valuable suggestions.
It was found that the material in the digestive tracts of the loach is pushed out of anus only while the so called intestinal respiration is possible, at least in acute cases. It seems probable that rhythmical contraction does not take place readily in straight intestine. And the following was concluded. The ingested food is possibly forced backwards through the movement of the wall of the stomach and coiled intestine. When it reached the anterior part of the straight intestine, it will probably pushed out of the anus by the swallowed air, i. e. through the intestinal respiration. The habit called intestinal respiration plays an important role not only for O2 up-take but for defecation. The author wishes to express his heartful thanks to Prof. SUYEHIRO for constant guidance in the course of the work. Thanks are also due to Assist. Prof. HIBIYA for valuable suggestions.
As far as known, abnormal development of the cranial bones in teleostei are described about three species, Thunnus thynnus, Chrysophrys major and Muraenoesox cineures. The author examined the morphological changes of the cranial bones of “Jack-mackerel” Trachurus japonicus, with the growth from 4 cm to 34 cm in body-length. The purpose of this article is to record with brief description the abnormal develop ment of the cranial bones in this fish. The remarkable expantion of supraoccipital bone in the cranium is noticed as shown in Fig. 1, and its gradual change is seen to be accomplished from 22 cm to 25 cm in body-length as in Table 1.