Showing papers in "Zoological Science in 1997"
TL;DR: The activity and stability on pH and temperature of the purified endo-β-1,4-glucanase are prominent among those from various organisms.
Abstract: beta-Glucosidase [EC 32121] and endo-beta-1,4-glucanase [EC 3214] activities were measured in the wood-eating higher termite Nasutitermes takasagoensis beta-Glucosidase activity was present mainly in the salivary glands (667%) and midgut (222%), whereas endo-beta-1,4-glucanase activity was detected mainly in the midgut (901%) Specific activity of endo-beta-1,4-glucanase was also the highest in the midgut, indicating that cellulose is digested in the midgut The major endo-beta-1,4-glucanase component of N takasagoensis was purified from whole termites by gel filtration on Sephaoryl S-200 HR, Superdex-75 and hydroxyapatite column chromatography Subsequently, the endo-beta-1,4-glucanase activity from a crude midgut extract was eluted in an identical volume (Kd = 068) to that from whole termites, suggesting the purified endo-beta-1,4-glucanase is identical to that in the midgut The molecular weight of the purified endo-beta-1,4-glucanase was 47 kDa, and its specific activity was 1,200 units/mg The optimal pH and temperature were 58 and 65 degrees C, respectively The Km and Vmax values on carboxymethyl cellulose were 87 mg/ml and 2,222 units/mg, respectively The purified endo-beta-1,4-glucanase hydrolyzed cellopentaose to cellotriose and cellobiose, and cellotetraose to cellobiose and a trace of cellotriose and glucose, but cellotriose and cellobiose were not hydrolyzed The activity and stability on pH and temperature of the purified endo-beta-glucanase are prominent among those from various organisms
144 citations
115 citations
TL;DR: It is demonstrated that the nanocomposite in the Cephopnodes wing decreases the light reflectance by the wing into 29-48% in the broad wavelength range, which shows by the color difference between the wings, coated by gold, with and without protuberances.
Abstract: A transparent wing of a hawkmoth, Cephonodes hylas, has a highly ordered array of nanosized protuberances in its surface. This protuberance array has almost the same morphology as that of the “corneal nipple array”, which is suggested to function as an antireflective device to light, using a scaled model experiment, a theoretical calculation, and a comparative way. For the direct study of the function of this protuberance array, we prepared an artificial wing without protuberances and compared it with an intact one with protuberances. Directly measuring the light reflectance spectra of the intact wing and the artificial one, we demonstrated that the nanocomposite in the Cephopnodes wing decreases the light reflectance by the wing into 29-48% in the broad wavelength range. This anti reflective effect is also showed by the color difference between the wings, coated by gold, with and without protuberances.
104 citations
TL;DR: Results suggest possible involvement of PRL and thyroid hormones in low-salinity adaptation of the flounder during metamorphosis and inshore migration.
Abstract: In Japanese flounder (Paralichthys olivaceus), metamorphic period involves not only transformation from larva to juvenile but also migration from offshore areas to estuaries. In the present study, the role of endocrine systems in low-salinity adaptation was examined during early development and metamorphosis of the flounder. Survival rate 48 hr after transfer to 1/8 SW was relatively high in yolk-sac larvae, decreased gradually to 0% at premetamorphosis, and increased to 100% at metamorphic climax. The ratio of prolactin (PRL)-immunoreactive part to whole pituitary increased gradually during larval stages and reached a constant level during metamorphosis. When the larvae at premetamorphosis and metamorphic climax and the benthic juveniles were transferred from SW to 1/4 SW, PRL-immunoreactive part increased significantly 48 hr after the transfer at all stages examined. Whole-body concentration of Cortisol was measured with a modified extraction method which is much robuster to lipid-rich sample t...
71 citations
TL;DR: Although common molecules are involved in development of insect appendages, the variety of the morphologies depends on pattern and timing of their expressions, according to the type of appendages.
Abstract: A million of insect species have been identified so far, displaying a staggering variety of adult morphologies. To elucidate mechanism how such insect morphologies are developed at a molecular level, we investigated developmental process of the two-spotted cricket, Gryllus bimaculatus, as a typical hemimetabola, and compared with that of Drosophila as an extensively studied typical holometabola. We analyzed expression patterns of homeobox genes of engrailed (en) and Distal-less (Dll) during development. In early embryos, en is expressed in the posterior compartments of body segments and developing appendages, while Dll is expressed in the distal region corresponding to the telopodite of developing appendages. Interestingly, these expression patterns are very similar to those observed in Drosophila imaginal discs. In the case of Dll, we found that its expression pattern, which is similar to each other in various appendages at early stages, changes in progress with elongation and segmentation, depe...
71 citations
64 citations
TL;DR: This study provides, for the first time, a practical method for preserving medaka spermatozoa using the vapor phase of liquid nitrogen, the liquid phase of LN, and dry ice for freezing and dimethyl sulfoxide and N, N-dimethylformamide were used as cryoprotectants.
Abstract: In order to establish a reliable and reproducible method for cryopreservation of medaka spermatozoa, we tested several procedures. The vapor phase of liquid nitrogen (LN), the liquid phase of LN, and dry ice were used for freezing, and dimethyl sulfoxide and N, N-dimethylformamide (DMF) were used as cryoprotectants. The best results were obtained using the following method. Medaka spermatozoa were collected in a plastic tube containing 50 μl of fetal bovine serum supplemented with 10% DMF by squeezing an isolated testis. The sperm suspension was frozen by holding the tube for 10 or 20 min in the vapor phase of LN at a depth of 9 or 10 cm from the top of a container. The frozen sample was immersed and stored in LN. After more than one week of storage, the sample in the tube was rapidly thawed by being incubated in a waterbath for 0.5–1 min at 30°C, and then immediately diluted with 2 volumes of Iwamatsu's solution. Fertilization tests using fresh unfertilized eggs showed that the stored spermatozo...
63 citations
TL;DR: It turned out that in nitrogen deficiency the stored uric acid is consumed by the symbiont in order to sustain the growth of the host, and these results are reminiscent of the nitrogen recycling reported for cockroaches.
Abstract: Planthopper harbors eukaryotic endosymbionts that are essential for normal development and growth of the host. Our previous studies suggested the possibility that the symbionts play an important role in nitrogen metabolism of the host through utilization of uric acid, a nitrogenous waste product. To examine the precise role of the symbiont, we prepared synthetic diets with various concentrations of amino acids, and measured uric acid contents stored in the insects reared on these diets. The results showed that planthopper synthesizes uric acid not only as a waste product, but also as a storage product when it ingests an excess amount of amino acids. We also investigated effects of the uric acid storage on growth of the normal and symbiont-depleted host. It turned out that in nitrogen deficiency the stored uric acid is consumed by the symbiont in order to sustain the growth of the host. In addition, we noted that the uric acid content of the host egg is highest at oviposition, and decreases signif...
59 citations
TL;DR: A cDNA which encodes a MiH (Pej-SGP-IV) of the kuruma prawn Penaeus japonicus is isolated in order to study its expression and characterize the structure of its precursor.
Abstract: The crustacean molt-inhibiting hormone (MIH) is released from the X-organ sinus gland complex and suppresses ecdysteroid synthesis by the Y-organ. In the present study, we have isolated a cDNA which encodes a MiH (Pej-SGP-IV) of the kuruma prawn Penaeus japonicus in order to study its expression and characterize the structure of its precursor. A cDNA fragment was isolated using RT-PCR with two degenerate oligonucleotide primers that were designed based on the peptide sequence of Pej-SGP-IV, and this fragment was used as a probe to screen an eyestalk cDNA library. In a positive cDNA clone (814 base pairs (bp)), an open reading frame of 315 bp was found; the conceptually translated protein consists of a putative signal peptide (28 residues) and Pej-SGP-IV (77 residues). In Northern blot analysis using a cDNA probe, specific hybridization to a transcript of 0.95 kb was seen in RNA extracted from the eyestalk but not from hepatopancreas, abdominal muscle, brain, thoracic ganglia or abdominal ganglia....
58 citations
TL;DR: Significant accumulation of Pjchi-2 mRNA was detected in the mixture of the tail fan and blade prior to molting, whereas the transcript level was much lower during the intermolt stage, suggesting that Pj Chi-2 plays a role in molting.
Abstract: To identify and characterize a chitinase related to molting in the Kurumia prawn Penasus japonicus, we searched for chitinase-encoding cDNAs expressed in cuticular tissues. Using two degenerate oligonucleotide primers derived from the two conserved regions of the chitinase protein family, a RT (reverse transcription)-PCR product was obtained. This product was used as a probe to screen a cDNA library from a mixture of the tall fan and blade-two tissues which consist mainly of chitinous exoskeleton and underlying epidermis. A positive cDNA clone was analyzed for the sequence. This clone contains an open reading frame for a protein (named Pjchi-2) of 527 amino acids which exhibits sequence similarity to known chitinases. A typical signal sequence could not be found in the Pjchi-2 sequence. Significant accumulation of Pjchi-2 mRNA was detected in the mixture of the tall fan and blade prior to molting, whereas the transcript level was much lower during the intermolt stage. This observation suggests that Pjchi-2 plays a role in molting. The mRNA was not detected in the hepatopancreas. This expression pattern of Pjchi-2 makes a contrast to that of Pjchi-1 which encodes another chitinase family protein in P. japonicus, and is expressed in the hepatopancreas but not in the tall fan or blade.
56 citations
TL;DR: Sexual differences in homing profiles as well as shortening of homing duration following GnRHa implantation in lacustrine sockeye salmon in Lake Shikotsu are indicated which may be reflective of changes in serum steroid hormone levels.
Abstract: Adult sockeye salmon (Oncorhynchus nerka) in Lake Shikotsu were captured in September, October and November adjacent to their natal hatchery prior to spawning. They were sampled for hormones, tagged and released in the center of lake. Fish were again sampled at recapture to characterize changes in steroid hormone levels in individual migrants as well as homing percentage and duration in each month. All males returned faster than females early in the breeding season, although a half of the tagged males did not return to the natal site late in the season (November). A high percentage of females always returned, and homing duration shortened late in the season. In males, the shortening of homing duration coincided with an increase in serum testosterone (T) and 11-ketotestosterone levels. In females, the shortening of homing duration corresponded to an elevation of serum T and 17α,20β-dihydroxy-4-pregnen-3-one (DHP) levels, and a drop in serum estradiol-17β levels. Sustained administration of gonadot...
TL;DR: The groE tree defined the relationship among A group Wolbachia strains that had not been successfully resolved by the ftsZ tree, and suggested unexpected horizontal transmission of these bacteria.
Abstract: Wolbachia, a member of rickettsia found in the cells of many arthropod species, are cytoplasmically inherited bacteria which interfere with host's sexuality and reproduction. Wolbachia strains have been phylogenetically divided into A and B groups based on the nucleotide sequences of their ftsZ genes. In an attempt to further define the phylogenetical relationship among these endosymbionts, we cloned and sequenced the entire length of the groE operon of a Wolbachia harbored by a cricket. The operon encoded two heat shock proteins, which represented the third and fourth proteins of any Wolbachia ever characterized. Also, 800 bp stretches of the groE operons of several other Wolbachia were sequenced, and a phylogenetic tree was constructed based on the results. The groE tree defined the relationship among A group Wolbachia strains that had not been successfully resolved by the ftsZ tree, and suggested unexpected horizontal transmission of these bacteria.
TL;DR: The results showed that the sequences from Japanese dormice were distinct from any sequences of the two continental species and the extent of the differences were somewhat similar to that between the rat (Rattus norvegicus) and the hamster (Mesocricetus auratus).
Abstract: The Japanese dormouse, Glirulus japonicus, is the only extant lineage that represents this genus and it has been classified as a single species distributed on the three main islands of Japan, namely Honshu, Shikoku and Kyushu. However, individuals collected from Fukui, Wakayama and Kochi Prefectures (southwestern part of Japan) yielded distinctly different profiles of restriction fragments of the nuclear ribosomal DNA (rDNA) spacer from those collected from Yamanashi and Nagano Prefectures (central Japan). The estimated sequence divergence between the two groups was 2.8% on average, which corresponds to a putative divergence some two million years ago. Representing mitochondrial DNA (mtDNA) sequences, 402 bases of cytochrome b gene were determined by direct sequencing and the estimated extent of the sequence divergence between the two groups was 6.5–7%. Differences between the two geographic groups were also substantial in the sequences of about 300 base-fragments from the Y-linked, sex-determini...
TL;DR: In this article, the androgenic gland hormone (AGH) was extracted from the male isopod Armadillidium vulgare by three steps of reverse phase high performance liquid chromatography (RP-HPLC) and its chemical properties were examined.
Abstract: The androgenic gland hormone (AGH) is known to control sex differentiation in crustaceans. AGH was purified from isolated androgenic glands (AGs) of the male isopod Armadillidium vulgare by three steps of reverse-phase high performance liquid chromatography (RP-HPLC) and its chemical properties were examined. The purified AGH-active fraction showed masculinizing activity when 38 pg of this preparation was injected into a young female of the same species. Only 160 ng of the material was obtainable from 2000 animals at about an 11% rate of recovery. The elution of AGH activity by molecular sieve HPLC indicated that molecular weight of AGH was 11,000 ∼ 13,000. AGH was inactivated by treatment with trypsin or by reductive carboxymethylation. The AGH activity was not affected by heat treatment at 100°C for 3 min. These results indicated that AGH was a heat-stable protein with disulfide bond(s).
TL;DR: Using a combined technique of anion exchange column and atomic absorption spectrometry, a vanadium-associated protein (VAP) is extracted from the blood cells of the ascidian Ascidia sydneiensis samea and it is revealed that VAP is composed of at least two types of peptides and is localized in the cytoplasm of the vanadocytes.
Abstract: Ascidians are known to accumulate vanadium in their blood cells (vanadocytes) at extremely high levels which correspond to about 106 to 107 times the levels of vanadium ions in seawater. The route for the accumulation of vanadium ions from the outside environment into the blood system in ascidians has not yet been discovered. In the present experiments, using a combined technique of anion exchange column and atomic absorption spectrometry, we first extracted a vanadium-associated protein (VAP) from the blood cells of the ascidian Ascidia sydneiensis samea. VAP was estimated to associate with vanadium at an approximate ratio of 1 mol: 16 mols. SDS-PAGE and a polyclonal antibody against VAP (anti-VAP) revealed that VAP is composed of at least two types of peptides estimated to be 12.5 kDa and 15 kDa with a minor peptide of 16 kDa and that VAP is localized in the cytoplasm of the vanadocytes.
TL;DR: Phylogenetic relationships among 31 operational taxonomic units of shrews (Soricidae, Mammalia), mainly from eastern Eurasia, were inferred from partial nucleotide sequences of the mitochondrial cytochrome b gene by maximum likelihood (ML) and neighbor joining (NJ) methods.
Abstract: Phylogenetic relationships among 31 operational taxonomic units of shrews (Soricidae, Mammalia), mainly from eastern Eurasia, were inferred from partial nucleotide sequences of the mitochondrial cytochrome b gene by maximum likelihood (ML) and neighbor joining (NJ) methods. Eleven monophyletic groups were recognized among the soricine shrews examined in the ML tree. However, branching orders of the groups were obscure judging from the local bootstrap values, and two out of the 11 groups were not monophyletic in the NJ tree. The phylogenetic relationships among Sorex caecutiens, S. shinto, and S. sadonis in the Japanese and Sakhalin islands, whose taxonomy was controversial, were clarified. S. shinto in the Honshu and Shikoku Islands is genetically differentiated enough to be considered a separate species from S. caecutiens, while S. sadonis could be treated as a subspecies of S. shinto. Some other taxonomic problems are also discussed.
TL;DR: Analysis of mitochondrial DNA restriction fragment length polymorphism in Japanese wild populations of the medaka revealed a large number of mtDNA haplotypes that form three distinct clusters, which appear fully concordant with the previously described ranges of the Northern Population and the Southern Population defined by allozymes.
Abstract: Analysis of mitochondrial DNA (mtDNA) restriction fragment length polymorphism in Japanese wild populations of the medaka, Oryzias latipes revealed a large number of mtDNA haplotypes that form three distinct clusters (clusters A, B and C). The average nucleotide diversities among these three clusters are 8.9% (A versus B), 8.4% (A versus C), and 7.3% (B versus C). Cluster A consists of seven haplotypes and was subdivided into two subclusters. The nucleotide diversity in cluster A is low, ranging from 0.3% to 1.4% (mean 0.8%). Cluster B has 55 haplotypes and was subdivided into 11 subclusters. The nucleotide diversity in cluster B is high, ranging from 0.1 to 4.8% (mean 1.5%). Cluster C consists of only one haplotype, found in two sites of the Kanto district. The geographic distributions of mtDNA haplotypes in clusters A and B appear fully concordant with the previously described ranges of the Northern Population and the Southern Population defined by allozymes. Moreover, the distributions of mtDN...
TL;DR: In 6th-instar larvae, the hemolymph ecdysteroid titers as well as the activity and sensitivity of the prothoracic glands (PGs) were nearly the same in the diapause- and nondiAPause-programmed larvae, while in non-diapause pupae (ND-pupae), the Ecdysteroids titer peaked in the first half of the pupal stage and remained low after pupation.
Abstract: The cabbage armyworm, Mamestra brassicae, enters winter and aestival diapause in the pupal stage under 10L-14D and 16L-8D, respectively, at 23°C. It develops without pupal dormancy under 14L-10D at 23°C. In 6th-instar larvae, the hemolymph ecdysteroid titers as well as the activity and sensitivity of the prothoracic glands (PGs) were nearly the same in the diapause- and nondiapause-programmed larvae. In non-diapause pupae (ND-pupae), the ecdysteroid titer peaked in the first half of the pupal stage. By contrast, in winter and aestival diapause pupae (WD- and AD-pupae), the ecdysteroid titer remained low after pupation. The ecdysteroid titer in diapausing AD-pupae was 8- to 10-times higher than that in diapausing WD-pupae. PGs from 5th-instar and 6th-instar larvae, as well as those from pupae, secreted ecdysteroids and showed a far stronger response to big prothoracicotropic hormone (PTTH) than to small PTTH in vitro. PG activity and its sensitivity to big PTTH fluctuated in a stage-dependent mann...
TL;DR: Results demonstrate that the photoreceptor for entrain-ment is the compound eye and the optic lobe is indispensable for persistence of the rhythm, and there are neural and/or humoral mechanisms for the aberrant rhythms outside of the optic lobeless animals.
Abstract: Circadian locomotor rhythm and its underlying mechanism were investigated in the cricket, Gryllodes sigillatus. Adult male crickets showed a nocturnal locomotor rhythm peaking early in the dark phase of a light to dark cycle. This rhythm persisted under constant darkness (DD) with a free-running period averaging 23.1 +/- 0.3 hr. Although constant bright light made most animals arrhythmic, about 40% of the animals showed free-running rhythms with a period longer than 24 hr under constant dim light condition. On transfer to DD, all arrhythmic animals restored the locomotor rhythm. Bilateral optic nerve severance resulted in free-running of the rhythm even under light-dark cycles. The free-running period of the optic nerve severed animals was significantly longer than sham operated crickets in DD, suggesting that the compound eye plays some role in determining the free-running period. Removal of bilateral lamina-medulla portion of the optic lobe abolished the rhythm under DD. These results demonstrate that the photoreceptor for entrainment is the compound eye and the optic lobe is indispensable for persistence of the rhythm. However, 75% and 54% of the optic lobeless animals showed aberrant rhythms with a period very close to 24 hr under light and temperature cycles, respectively, suggesting that there are neural and/or humoral mechanisms for the aberrant rhythms outside of the optic lobe. Since ocelli removal did not affect the photoperiodically induced rhythm, it is likely that the photoreception for the rhythm is performed through an extraretinal photoreceptor.
TL;DR: Combined data from spermatogenic activity, plasma androgen levels, and changes in the weights of testes, fat bodies, and livers revealed that B. melanostictus is a continuous breeder.
Abstract: The male reproductive cycle of the toad, Bufo melanostictus, was studied with emphasis on spermatogenic activity, plasma androgen, and changes in the weights of testes, liver, and fat bodies. A total of 98 toads were collected between March 1990 and March 1991 in central Taiwan. Histological evidence indicated that the spermatogenic cycle of this toad is of a fluctuating continuous type. Although cell nests of all spermatogenic types were present every month of the year, the greatest intensity of spermatogenic activity, as expressed by the presence of sperm bundles, occurred in March. Both testicular weight and plasma androgen levels peaked in March. The weights of fat bodies peaked in July, which was not coincident with the beginning of breeding. Combined data from spermatogenic activity, plasma androgen levels, and changes in the weights of testes, fat bodies, and livers revealed that B. melanostictus is a continuous breeder. However, its annual reproductive cycle could be divided into 4 period...
TL;DR: It is concluded that exogenous oPRL inhibits the hypoosmoregulatory action of F, but does not antagonize the F-dependent stimulation of gill Na+,K+-ATPase activity.
Abstract: Two experiments are described in which the interaction of prolactin, cortisol and growth hormone on hypoosmoregulation in the anadromous brown trout was studied. In experiment 1, fish at the postsmolt stage in freshwater (FW) were given four injections on alternate days of 5 μg cortisol (F)/g in combination with 0, 0.2, 1 or 2 μg ovine prolactin (oPRL)/g. Additional groups received 2 μg oPRL/g or saline as control. In experiment 2, FW parr were given four injections on alternate days with 5 μg F/g and 2 μg ovine growth hormone (oGH)/g in combination with 0, 0.2, 1 or 2 μg oPRL/g. Additional groups received 2 μg oPRL/g, 2 μg oGH/g, 5 μg F/g or saline as control. In both experiments, the fish were subjected to a 48 hr seawater (SW) challenge test 24 hr after the last injection. Muscle water content, plasma osmolality and ion levels, kidney and gill Na+, K+-ATPase activity were measured. In experiment 1, F-treated fish had better hypoosmoregulatory capacity than control fish as judged by a higher le...
TL;DR: The E. vigintioctomaculata complex offers a rare opportunity to extend the understanding of the nature of animal species and their origin, covering the mode of speciation in host specific insects, role of postinsemination barriers to fertilization, reinforcement of reproductive isolation, and treatment of allopatric populations in speciation studies.
Abstract: The present paper reviews current studies on various aspects of reproductive isolation in a series of closely related phytophagous ladybird beetles called the Epilachna vigintioctomaculata complex, which is composed of two groups and four species: group A comprising E. vigintioctomaculata, and group B comprising one northerly distributed species, E. pustulosa, and two southerly distributed species, E. niponica and E. yasutomii.Being broadly sympatric from middle through northern Japan, the two groups are reproductively isolated by a combination of several factors, each of which functions as an incomplete barrier to gene flow: difference of host plants, weak sexual isolation, and low hatching rates of eggs produced by interspecific matings. Conspecific sperm precedence further lessens the probability of producing hybrids in mixed populations. By contrast, the two sympatric species of group B, E. niponica and E. yasutomii, are reproductively isolated from each other solely by fidelity to different host plants. However, there are no effective barriers to gene exchange between either of these two species and the northerly distributed E. pustulosa.These situations have relevance to various controversial issues in evolutionary biology, covering the mode of speciation in host specific insects, role of postinsemination barriers to fertilization, reinforcement of reproductive isolation, and treatment of allopatric populations in speciation studies. The E. vigintioctomaculata complex thus offers a rare opportunity to extend our understanding of the nature of animal species and their origin.
TL;DR: The statistical analysis revealed that the probabilities of these wind-evoked behaviors were affected by the intensity of the wind stimulus, and the escape and “no action” were dominant, together constituting more than 60% of the total responses.
Abstract: The behavioral responses to a wind stimulus were studied in the freely moving cricket, Gryllus bimaculatus. The observed responses included walking, running, jumping, turning, withdrawing, abdominal lifting, hind-leg lifting, kicking, cercal cleaning, antennal swinging, and “no action” and were classified into five behaviors as functional categories: escape, evasion, offense, surveillance and “no action”. The elicitation of each type of behavior by an identical stimulus was variable and unpredictable. However, the stochastic approach showed that the probabilities of the behaviors converged in a series of responses obtained from one cricket and in mass response data collected from 48 crickets. These probabilities, the values calculated from the different populations, were the same. The statistical analysis, using the probabilities, revealed that the probabilities of these wind-evoked behaviors were affected by the intensity of the wind stimulus. The escape and “no action” were dominant, together c...
TL;DR: Embryonic temperature sensitivity of the solitary ascidian, Ciona savignyi, was examined with special reference to acclimatization to seasonal change in seawater temperature to find the optimal temperature range for development from early cleavage stage to metamorphosis in embryos produced by individuals raised in warmer seasons.
Abstract: Embryonic temperature sensitivity of the solitary ascidian, Ciona savignyi, was examined with special reference to acclimatization to seasonal change in seawater temperature. This ascidian spawns throughout the year; its life span is completed within six months and depends on the cumulative environmental temperature. The optimal temperature range for development from early cleavage stage to metamorphosis in embryos produced by individuals raised in warmer seasons differed significantly from that of individuals raised in colder seasons. Within the common optimal temperature range, developmental times at any given temperature were the same for both groups of embryos. The thermal acclimation of ascidian embryos is discussed and compared with that of echinoid embryos.
TL;DR: It was found that the distribution of cones in the retina could be easily detected by autofluorescence-emission from the photoreceptor cells without any staining, and the regular arrangement of cones was confirmed in the whole retina.
Abstract: In the retina of the medaka four kinds of retinal cone photoreceptor cells are arranged in a simple, repeating organizational pattern known as a square mosaic. We found that the distribution of cones in the retina could be easily detected by autofluorescence-emission from the photoreceptor cells without any staining. In tangential sections of the retina, cones were located at a specific position in a crystalline lattice as follows: Double cone pairs display a zigzagging appearance, oriented roughly 90-120 degrees to one another, and single cones were in the center of the square consisting of four double cone pairs. In order to determine the continuity of this regular arrangement on the spherical surface, the distribution of this cone mosaic pattern was examined in central, dorsal, ventral, nasal and caudal areas of the retina. The regular arrangement of cones was confirmed in the whole retina. Double cones and single cones are in their respective lines and these lines form a lattice-work. As a re...
TL;DR: The present results, combined with previously published data, describe the fine structure of the tunic cuticle in 116 species of ascidians covering all the families and subfamilies of the class Ascidiacea except for the phlebobranch families Octacnemidae and Plurellidae.
Abstract: Fine structure of the ascidian tunic cuticle was surveyed for minute protrusions in 30 species of the suborder Aplousobranchia, 10 species of Phlebobranchia and 23 species of Stolidobranchia (Ascidiacea, Chordata). The present results, combined with previously published data, describe the fine structure of the tunic cuticle in 116 species of ascidians covering all the families and subfamilies of the class Ascidiacea except for the phlebobranch families Octacnemidae and Plurellidae. These data confirm the general stability of the character-state distribution (presence or absence) of the tunic cuticular protrusions within families or subfamilies. Cuticular protrusions occur only in Polyclininae and Clavelininae of the order Enterogona (Aplousobranchia and Phlebobranchia) and in all families of the order Pleurogona (Stolidobranchia and Aspiraculata). A few exceptions were the occurrence of cuticular protrusions in Polycitor proliferus (Polycitorinae), Distaplia dubia (Holozoinae), Pterygascidia long...
TL;DR: It is demonstrated that HNK-1 recognizes a subpopulation of naural crest cells and crest derivatives in the lamprey as well as in the swordtail, and dorsal pathways, which extended to the embryonic dorsal fin, of neural crest cells in both swordtail and lamprey embryos are found.
Abstract: Migration and colonization patterns of neural crest cells were analyzed histochemically in embryos of the brook lamprey, Lampetra reissneri, and the swordtail, Xiphophorus helleri, using HNK-1 monoclonal antibody, which recognizes migratory neural crest cells and crest derivatives in many groups of vertebrates including teleosts. We demonstrated that HNK-1 recognizes a subpopulation of naural crest cells and crest derivatives in the lamprey as well as in the swordtail. In the trunk of lamprey and swordtail embryos, HNK-1-positive cells were observed in the major migratory pathways of neural crest cells, that is ventral and dorso-lateral pathways. In the swordtail embryos, neural crest cells in the ventral pathway were ubiquitously observed along the rostro-caudal axis at the neural tube level, but at the notochord level their migration was restricted to the middle region of the somite. In the lamprey, by contrast, no HNK-1-immunoreactive neural crest cells migrated ventrally beyond the notochord ...
TL;DR: Differences seen in larval life histories between the two populations may represent adaptations for differential stability of water level and water temperature, and resultant differences in the size of metamorphs possibly induce differential adult body size, and hence fecundity.
Abstract: Larval life histories of Kyoto and Tokyo populations of the stream breeding salamander Hynobius kimurae are compared in the field. The Kyoto population has smaller adults and ovarian egg numbers, but larger egg sizes. Minimum water temperature is lower, and the stream partly dries up between late October and late November in Kyoto, while the amount of water is always stable in Tokyo. In Kyoto, metamorphosis occurs between late July and late September and no larva is found in the water in and after October. In Tokyo, only 21% of larvae metamorphose in the first year and most overwinter and metamorphose between late May and mid June of the second year. Size of hatched larvae does not differ between Kyoto and Tokyo, but metamorphs from Kyoto are smaller than first year metamorphs from Tokyo, which in turn are smaller than the second year metamorphs. Differences seen in larval life histories between the two populations may represent adaptations for differential stability of water level and water temp...
TL;DR: Results indicate ocular melatonin rhythms in oikawa are driven not by a circadian clock but by LD cycles, which indicates melatonin levels in the oikawa eye exhibited daily rhythms with higher levels during the dark phase than those during the light phase.
Abstract: Ocular melatonin contents in a cyprinid teleost, oikawa Zacco platypus were determined by newly-developed radioimmunoassay. Under light-dark (LD) cycles of 12:12 hr, melatonin levels in the oikawa eye exhibited daily rhythms with higher levels during the dark phase than those during the light phase. However, the rhythms disappeared under either constant light (LL) or constant darkness (DD). Ocular melatonin contents under LL remained at low levels while those under DD kept high titers. These results indicate ocular melatonin rhythms in oikawa are driven not by a circadian clock but by LD cycles.
TL;DR: The results suggest that the regression of muscle cell differentiation is mediated by changes in the structure of muscle actin genes rather than in the trans-acting regulatory factors required for their expression.
Abstract: Actin is a ubiquitous protein in eukaryotic cells and plays an important role in cell structure, cell motility, and the generation of contractile force in both muscle and nonmuscle cells. Multiple genes encoding muscle or nonmuscle actins have been isolated from several species of ascidians and their expression patterns have been investigated. Sequence and expression analyses of muscle actin genes have shown that ascidians have at least two distinct isoforms of muscle actin, the larval muscle and body-wall isoforms. In the ascidian Halocynthia roretzi, two clusters of actin genes are expressed in the larval muscle cells. The HrMA2/4 cluster contains at least five actin genes and the HrMA1 cluster contains a pair of actin genes whose expression is regulated by a single bidirectional promoter. cis-Regulatory elements essential for muscle-specific expression of a larval muscle actin gene HrMA4a have been identified. The adult body-wall muscle actin is clearly distinguished from the larval muscle act...