Chitaru Oguro

REPRODUCTION AND DEVELOPMENT OF THE HERMAPHRODITIC SEA-STAR, ASTERINA MINOR HAYASHI

1. The breeding season of Asterina minor is estimated to be during the month of May in Kushimoto, Japan. A. minor shows a characteristic breeding assemblage and the eggs are laid on the substratum in a mass spawning. The eggs are not protected by the adults.2. A. minor is a spatial hermaphrodite, where ovaries and testes in an individual become mature simultaneously. Isolated individuals are capable of self-fertilizing and the self-fertilized eggs develop normally.3. The spawned eggs are spherical, yellow, and 437 µm in average diameter. They attach to the substratum with a sticky jelly layer. Cleavage is total and radial.4. Eggs through the wrinkled blastula stage develop into a pear-shaped brachiolaria bearing three brachiolar arms within the fertilization membrane.5. About four days after spawning, the brachiolariae hatch from the fertilization membrane and creep on the substratum with well-developed brachiolar arms. There is no evidence of pelagic life in the present species.6. One day after hatching,...

Cells showing immunoreactivity for calcitonin or calcitonin gene-related peptide (CGRP) in the central nervous system of some invertebrates.

In the central nervous system of some species of several invertebrate phyla, including land planarians (Platyhelminthes), ribbon worms (Nemertina), slugs (Mollusca), polychaetes, earthworms and leeches (Annelida), pill bugs (Arthropoda), and beard worms (Pogonophora), salmon calcitonin-immunoreactive cells and rat calcitonin gene-related peptide (CGRP)-immunoreactive cells were found by immunohistochemistry. These immunoreactive cells were located in the region surrounding the neuropile, although the sizes of the cells varied according to species. Some of them were round or polygonal and regarded as apolar nerve cells because of their lack of cytoplasmic processes, whereas others were spindle-shaped or elongated, being comparable with unipolar nerve cells because of extension of their cytoplasmic processes in the direction of the neuropile. In some cases, it was noted that the cytoplasmic processes had complicated branches or formed loop-like structures at their ends. These observations suggest that a calcitonin-like or CGRP-like substance is extensively present in invertebrates as well as vertebrates.

Development of a True Ovoviviparous Sea Star, Asterina pseudoexigua pacifica Hayashi

Asterina pseudoexigua pacifica is a true ovoviviparous asteroid in that its development and metamorphosis occur within the spatial hermaphroditic gonad. From the middle of June to the middle of July, the gonad contains numerous embryos and juveniles in various stages through metamorphosis. The opaque, greenish yellow mature ovum is 450 μm in diameter. Development is direct. Embryos develop through wrinkled blastula and gastrula stages into a pear-shaped brachiolaria with three arms. The general process is similar to that of asteroids having direct development. Newly metamorphosed juveniles are released from the gonopores. Peak release occurs in the middle of July. The maximum number of juveniles released from an adult is about 1300. The juvenile is 900 μm in diameter and has two pairs of tubefeet in each arm; the skeletal plates are well developed. The present results are compared with those of other true viviparous echinoderms.

Control of serum calcium concentration by parathyroid gland in two species of urodele amphibians

Abstract Control of serum calcium concentration was studied in two species of urodeles, Cynops pyrrhogaster and Hynobius nigrescens, by means of parathyroidectomy and hypophysectomy. Parathyroidectomy caused hypocalcemia in C. pyrrhogaster without significant changes in serum sodium and magnesium concentrations. On the other hand, no appreciable changes were found in serum calcium, sodium, and magnesium concentrations in H. nigrescens following parathyroidectomy. Implantation of the parathyroid glands of either C. pyrrhogaster or H. nigrescens elicited a significant increase of serum calcium concentration in parathyroidectomized C. pyrrhogaster. The results show the presence of a hypercalcemic principle in the parathyroid gland of H. nigrescens. Therefore, it is likely that the ineffectiveness of parathyroidectomy in H. nigrescens is primarily due to the lack of a response by the target organ system in this species. The present results show that the significance of the parathyroid gland in hypercalcemic effect is different in these two species of Urodela. Hypophysectomy in both species caused decreases of serum calcium, sodium, and magnesium concentrations 10 and 20 days after the operation, and the decrease of sodium was in general more pronounced than that of calcium.

Presence of a hypocalcemic factor in the ultimobranchial gland of the snake

Abstract The hypocalcemic activity of the ultimobranchial gland (UBG) in the snake, Rhabdophis tigrinus tigrinus , was examined in a bioassay using young Sprague-Dawley rats. Crude extracts of the UBG showed a hypocalcemic potency. In general, the response showed a dose-response relationship. The activity of one UBG nearly corresponds to that of 10 mU (MRC) of salmon calcitonin. Crude extracts of the snake thyroid gland did not cause any detectable hypocalcemic response even with a high dose.

Parathyroid gland of the snake Elaphe quadrivirgata with special reference to parathyroidectomy

Abstract The snake Elaphe quadrivirgata possesses two pairs of parathyroid glands, one near the carotid fork and the other attached to or embedded in the posterior thymus. The parenchyma consists of cell cords composed of a single type of cell and supplied with rich blood vessels. The gland is encapsulated by a membrane of connective tissue. These histological features are similar to those of other species of reptiles. Serum calcium concentration in normal adults was 13.0 ± 0.36 mg/100 ml (mean ± SE), while that of hatchlings was 12.6 ± 0.42 mg/100 ml, not significantly different. Parathyrothymectomy resulted in a decrease of the serum calcium concentration to 7.6 ± 1.06, 8.7 ± 0.53, and 8.0 ± 1.54 mg/100 ml for 7, 10, and 20 days after the operation, respectively. Three individuals out of 19 totally parathyrothymectomized animals showed tetanic convulsions, although no animal died from this cause. A few specimens showed extraordinarily high concentrations of serum calcium irrespective of the treatment.

Parathyroid gland and serum calcium concentration in the giant salamander, Megalobatrachus davidianus

Normal serum calcium concentration in the giant salamander, Megalobatrachus davidianus is 8.88 ± 0.26 mg/100 ml. Surgical parathyroidectomy exerted no effect on the serum calcium concentration. The values were 8.67, 8.88, 8.61, and 8.27 mg/100 ml for 5, 10, 20, and 60 days after the operation. The results may show that the parathyroid gland of M. davidianus is not important in the regulation of serum calcium concentration. Administration of parathyroid gland homogenate of M. davidianus to parathyroidectomized newt, Cynops pyrrhogaster, increased serum calcium concentration within 2 hr. It is therefore concluded that the parathyroid gland of M. davidianus contains a hypercalcemic principle and the ineffectiveness of parathyroidectomy is due to the lack of a response by the target-organ system. However, parathyroid glands may have a minor role in regulation of serum calcium concentration in this species.

Calcitonin of the stingray: Comparison of the hypocalcemic activity with other calcitonins

Hypocalcemic potency of calcitonin isolated from the stingray (cartilaginous fish), Dasyatis akajei, was examined using the rat bioassay and compared with the activities of other calcitonins (human, pig, salmon, eel, and fowl). The potency of Dasyatis calcitonin (dCT) was estimated to be 1500-3800 IU/mg. However, when the duration of the hypocalcemic effect of dCT was taken into consideration, it was judged that dCT was approximately 2.4-6.2 times more potent than mammalian calcitonins, but about 2.3-3.5 times less active than other nonmammalian calcitonins.

Renal responses of the Chilean toad, Calyptocephalella caudiverbera, and the mud puppy, Necturus maculosus, to mesotocin

Abstract Intravenous injections of mesotocin resulted in increased urine production in the Chilean toad, Calyptocephalella caudiverbera , and the mud puppy, Necturus maculosus . At low doses, the diuretic responses increase with the doses of hormone administered, but at high doses the diuretic response is considerably reduced. These findings confirm those reported previously for the bullfrog ( P.K.T. Pang and W.H. Sawyer, 1978 , Amer. J. Physiol. 235 (2), F151–F155). However, this is the first time that such data are reported for an aquatic toad and an aquatic urodele.

Effects of ultimobranchialectomy on calcium and sodium concentrations of serum and coelomic fluid in bullfrog tadpoles under high calcium and high sodium environment

Abstract 1. 1. The role of the ultimobranchial gland of bullfrog tadpoles on the regulation of calcium and sodium levels in serum and coelomic fluid was studied by means of ultimobranchialectomy. 2. 2. Calcium levels in serum and coelomic fluid in the ultimobranchialectomized tadpoles increased markedly after 48 hr treatment with high calcium and sodium media, although no changes were found in these levels in tap water. 3. 3. The tendency to hyponatremia was more pronounced in the ultimobranchialectomized tadpoles than in the sham-operated. 4. 4. It is concluded that one of the functions of the ultimobranchial gland of the anuran larva is to suppress the acute rise of calcium levels in body fluid.