The voluntary movement of antennae of blinded cockroaches was examined in the tethered-walking condition. An object of metal plate was presented to a tip of a single antenna in order to induce tactile orientation behavior. Horizontal movements of the antenna before and during the object presentation were analyzed both before and after ablation of a mechanosensory organ, the scapal hair plate (S-HP), at the base of antenna. The resting antennal position shifted outwardly by about 20° after the S-HP ablation. Spontaneous antennal movements in ablated animals became stiff and wider ranged. The tactile object was set at two different horizontal positions, 45° and 90° clockwise to the head, for the right side antenna. The number of contacts in a constant test period was significantly decreased in the tests at 45° after ablation. Trajectories of antennal movements before and after contacts were categorized into four patterns. In the case that an antenna made contact with the object during its abduction (outward) movement, it then passed the object outwardly or withdrew inwardly. These were termed “outward-pass (O-P)” and “outward-withdrawal (O-W)” patterns, respectively. Similarly, contacts during the adduction (inward) movement were divided into “inward-pass (I-P)” or “inward-withdrawal (I-W)” pattern. Significant effects of the S-HP ablation appeared in the tests at 90°: the I-P pattern mostly disappeared and was replaced by the I-W pattern. The results strongly suggest that the S-HP has crucial roles for controlling both spontaneous and stimulated movements of the cockroach antenna.

Neurogenesis in the dentate gyrus of adult rodents is elicited by transient global ischemia. Cyclooxygenase (COX) -2, a rate-limiting enzyme for prostanoid synthesis, is also induced by ischemia. We recently found that the administration of a non-selective COX inhibitor to ischemic animals suppressed cell proliferation in the subgranular zone (SGZ) at the dentate gyrus of the hippocampus. To clarify whether prostaglandin E2 (PGE2) synthesis by COX's is involved in neurogenesis, sulprostone, an analogue of PGE2, was injected into the rat hippocampus. Sulprostone injection increased the number of 5-bromo-2′-deoxyuridine (BrdU)-positive cells in the SGZ. BrdU-positive cells also expressed polysialylated isoforms of neural cell adhesion molecule and neuronal nuclear antigen. These results suggest that PGE2 plays an important role in the proliferation of cells in the SGZ.

We investigated innervation to body wall muscles as well as distribution of 5-HT (serotonin) and its effects on longitudinal muscles of body wall (LMBW) of the sea cucumber Apostichopus japonicus. With serial sections we found neural branches and fibers extending from hyponeural part of radial nerve towards LMBW and circular muscles of body wall. With the aqueous aldehyde (Faglu) method yellow fluorescence indicating indolamines was observed in LMBW and in the mesentery connecting LMBW to the body wall. With indirect immunohistochemistry 5-HT-like immunoreactivity was observed in LMBW and in mesentery. These results strongly suggested that both LMBW and mesentery contained 5-HT. The effects of monoamine neurotransmitters were studied in LMBW. Putative neurotransmitters tested were 5-HT, adrenaline, noradrenaline, dopamine, and DOPA at the concentration of 10⁻⁶ M. The application of 5-HT caused no contraction or relaxation, but it inhibited the contraction induced by 10⁻⁶–10⁻⁵ M acetylcholine (ACh). Catecholamines were ineffective by themselves and had no effects on the contraction induced by ACh. The present histological, histochemical, and pharmacological studies strongly suggested that holothurian LMBW was innervated by inhibitory serotonergic neurons of the hyponeural nervous system.

Accessory corner cones (ACC) have recently been suggested to be UV-sensitive photoreceptor cells. With a view toward explaining prey detection, we examined the topography of retinal ganglion cells and ACCs in two Antarctic nototheniids occupying different ecological niches: the cryopelagic Pagothenia borchgrevinki and the benthic Trematomus bernacchii. Isodensity maps of retinal ganglion cells showed that the main visual axis, coincident with the feeding vector, was in a forward direction in both species. Visual acuity was determined as 3.64 and 4.77 cycles/degree for the respective species. In P. borchgrevinki the highest density of ACCs was associated with the eye's main visual axis. This suggested that this species uses UV-vision during forward-swims and probably in encounters with prey. On the other hand, T. bernacchii possessed two horizontal band-shaped high-density areas of ACCs, which stretched from temporal to nasal and ventral to peripheral retinal regions. Therefore, this species appears to use UV-vision to watch prey across the entire circumference of the lateral area and in the water column above its head.

Onchidium possesses stalk eye (SE) and dorsal eye (DE) which comprise part of a unique multiple photoreceptive system. The retina of SE consists of rhabdomeric-type visual cells, whereas the DE contains two types of photoreceptor cells; ciliary-type cells in the retina and rhabdomeric-type cells in the lens. High-performance liquid chromatography (HPLC) analyses revealed the presence of 11-cis-retinal as well as all-trans-retinal in both eyes. The amount of retinal of one DE (0.17 pmol) is far less than that in one SE (0.41 pmol) in the dark-adapted Onchidium. In the dark-adapted SE, the amount of all-trans-retinal was higher than that of 11-cis-retinal. This finding is consistent with the presence of photic vesicles, including retinochrome, in rhabdomeric-type visual cells. In contrast, a higher amount of 11-cis-retinal than all-trans-retinal was present in dark-adapted DE, although this was decreased in light-adapted DE. Upon UV irradiation following treatment with sodium borohydride (NaBH₄), the fluorescence (derived from retino-chrome) was observed in the somatic layer of SE. Additional fluorescence (due to rhodopsin) was observed in the villous layer upon treatment with NaBH₄ after denaturation. However, only weak, obscure fluorescence of retinyl proteins was observed in the DE, not in a specific but an indefinite area on treatment with NaBH₄ with or without denaturation. With fluorescence histochemistry, the localization of rhodopsin and retinochrome was confirmed at specific regions in the retina of the SE, whereas no distinct localization of these photopigments in DE was demonstrated. The amount of retinal to detect the fluorescence may be too low in the DE, or photopigments of DE may differ in chemical nature from those of SE.

Females of the stream goby Rhinogobius sp. DA with paternal care favor males courting in fast water currents, whereby they mate males of high parental ability. Here we examined female choice of male nest size of this goby in laboratory. The dichotomous choice experiment clearly indicated that females prefer large nests. Spawning at large nests seems to improve egg survival rates in natural habitats in this goby. We discuss the possibility of multiple criteria in mate choice of this goby.

Autogamy in Paramecium tetraurelia is a form of sexual reproduction in a single cell that results in homozygosity in every genetic locus. Autogamy becomes inducible by natural starvation several fissions after the previous autogamy, and percent autogamy increases gradually with clonal age to reach 100%. We here report the degree of variability of the autogamy-maturation pattern, and how it is inherited through autogamous generations. We assessed the autogamy-maturation pattern by monitoring percent autogamy at the ages of 9, 18 and 27 fissions in the wild-type stock 51. To determine how the autogamy-maturation pattern is inherited, clones that showed the lowest and the highest percent autogamy at age 18 in a given autogamous generation (Gn) were examined for their percent autogamy in the next autogamous generation (Gn 1). This procedure was repeated through successive autogamous generations. We found that percent autogamy at ages 9 and 27 was rather stable (low and high, respectively), while it was extremely variable at age 18 ranging from 3% to 100%. We also found that percent autogamy at age 18 in the progeny clones was variable irrespective of percent autogamy at age 18 in the parental clones; there was no regular rule such as producing progeny with higher (or lower) percent autogamy from parents with lower (or higher) percent autogamy.

At least two different protease pathways have been implicated in the degradation that is required to control the eukaryotic cell cycle; these two pathways center on the activities of ubiquitin/proteasome and cysteine protease. The proteasome inhibitors, lactacystin and AcLLnL and the cysteine pro-tease inhibitor E-64-d were tested for their ability to inhibit the cell cycles of Xenopus embryos. Lactacystin, AcLLnL and E-64-d all caused the complete arrest of the cell cycle. To define the specific cell cycle processes that were affected by the two inhibitors, we performed a cytological analysis. Inhibition of the cell cycle by lactacystin and E-64-d occurred during prophase and metaphase. The number of cells that arrested in prophase was 1.4-times higher in the E-64-d-treated group than in the control group and the number of arrested cells in the lactacystin-treated group was 1.4-times higher than in the E-64-d-treated group. The number of cells that arrested in metaphase was 3-to-4-times higher in the E-64-d and lactacystin groups than in the control group. These results indicate that both cysteine protease(s) and proteasomes are involved in the prophase and metaphase stages of cell division.

Studies using molecular markers have revealed that planarians possess a highly organized brain. Here we separated brain neurons from dissociated planarian head cells by fluorescence activated cell sorting (FACS), and characterized them by single cell PCR analysis and cell culture. Dissociated cells were labeled with three different fluorescent dyes, Hoechst 33258, Merocyanine 540, and Propidium Iodide (PI), and fractioned by FACS. Interestingly, we have succeeded in identifying a cell fraction specific to the head, which we have named the head-abundant cell fraction (HAC). Most of the HAC expressed neuron-specific genes and proteins. When they were cultured in vitro, they showed an ability to extend neurites on several types of extracellular matrices (ECMs), and, depending on the ECM type used, presented a high level of plasticity in morphology and gene expression.

Asexual individuals in a fissiparous clone of the planarian Dugesia ryukyuensis develop hermaphroditic sexual organs and eventually undergo sexual reproduction instead of asexual reproduction if they are fed with the adults of Bdellocephala brunnea, an oviparous planaria. The experimental sexualization means that the adults of B. brunnea contain a putative sexualizing substance(s), which is the first candidate for the chemical(s) responsible for switching from asexual to sexual reproduction in metazoans. In the present study, the feeding experiment over two consecutive years revealed that the experimental sexualization has seasonal changes. In summer, the asexual individuals were not fully sexualized, though they developed a pair of ovaries. The developing ovaries degenerate if the feeding is stopped. On the contrary, in winter, they developed all the sexual organs. The sexual organs keep developing even if the feeding is stopped after a certain critical point named the point-of-no-return. It was demonstrated that the extreme difference of the sexualization was attributed to the seasonal change of the quality and/or quantity of the sexualizing substance contained in B. brunnea, as well as the minor change of the susceptibility to the sexualizing substance in the asexual individuals. On the other hand, the histological research of B. brunnea revealed that the degree of the maturation of the sexual organs varied extremely through a year. Taking these results into account, we suggest that the production of the sexualizing substance has no direct relation to any particular mature sexual organs.

Gontarella gigantea gen. et sp. nov. is described from two stations, one in the Sea of Okhotsk and the second on the Pacific side of the Small Kuril Arc. This membraniporiform anascan cheilostome bryozoan has very large zooids, the largest known among extant sheet-like encrusting anascans. Comparative data on similar sheet-like cheilostomes gathered from the literature shows that the new species represents a conspicuous outlier in size, with the surface area of the zooid being approximately twice that of the next largest species. Skeletal evidence, including the lack of ovicells, indicates that G. gigantea belongs within the malacostegan family Electridae. The gigantic ancestrula suggests that the species has a cyphonautes larva about 1 mm in maximum dimension.

Gene products of 22 protein coding loci from 29 populations of a uniquely sea-going cyprinid genus Tribolodon, T. hakonensis (anadromous and/or river-resident), T. brandtii (anadromous), T. ezoe (freshwater) and T. nakamurai (freshwater), were analyzed in order to infer the genetic divergence and dispersal of Tribolodon species around the Sea of Japan. According to the genetic distance, T. brandtii is located near the center between T. hakonensis and T. ezoe-T. nakamurai cluster. The outgroup root (Pseudaspius leptocephalus, Rhynchocypris lagowskii and Leuciscus waleckii) is attached between T. hakonensis-T. brandtii and the T. ezoe-T. nakamurai clusters. The origin of the genus Tribolodon and its salinity tolerance may date back to the Miocene Sea-of-Japan Lake and the Pliocene Paleo-Sea-of-Japan, respectively, as judged from the divergence time between Tribolodon and the outgroups. The genetic relationships and distribution pattern of Tribolodon species suggest they speciated on the Sakhalin-Japan side, and the continental populations of T. hakonensis and T. brandtii originated from anadromous colonizers. A new faunal element of Japanese freshwater fishes, the Sakhalin-Japan sub-element, is proposed for Tribolodon and some other fishes.

Phylogenetic relationships of the genus Cuora sensu lato (Cuora sensu stricto and Cistoclemmys) and other testudinoid genera were inferred from variations in 882 base positions of mitochondrial 12S and 16S rRNA genes. Results yielded a robust support to the monophyly of a group (Cuora group) consisting of Cuora sensu lato and the monotypic Pyxidea. Within the Cuora group, the continental Cuora (sensu stricto) and the two subspecies of Ci. flavomarginata constituted two well-supported monophyletic groups. Distinctly small interspecific genetic distances in the former groups suggested that in the continent speciations in Cuora took place much later than the primary divergences in the Cuora group, or speciations in other related genera, such as Mauremys. Our analyses failed to provide a substantial support to the monophyly of any other combinations of taxa within the Cuora group, including Cuora in broad and strict senses, and Cistoclemmys as consisting of Ci. galbinifrons and Ci. flavomarginata. Besides these, our results also suggested the non-monophyly for the Batagurinae and the Geoemydinae, and sister relationships of the Bataguridae with Testudinidae rather than with the Emydidae.

To distinguish pig-wild boar crossbred Inobuta from Japanese wild boar populations, a genetic method by using mitochondrial DNA (mtDNA) haplotypes and the nuclear glucosephosphate isomerase-processed pseudogene (GPIP) was developed. Sixteen mtDNA haplotypes from 152 wild boars from Kyushu, Shikoku and Honshu islands of Japan were distinct from those from Asian and European domestic pigs. Five alleles of GPIP were classified into two groups: 1) alleles GPIP*1, GPIP*3 and GPIP*3a from Japanese wild boars, Asian wild boars and domestic pigs; 2) alleles GPIP*4 and GPIP*4a from European wild boars and domestic pigs. An extensive genetic survey was done to distinguish the crossbred Inobuta from 60 wild boars hunted on Tsushima Island, Goto Islands, and Nagasaki and Ooita Prefectures. The mtDNA haplotypes from the 60 samples showed Japanese wild boars, but four wild boar samples from Nagasaki Prefecture had the European GPIP allele, GPIP*4. These results showed that nuclear DNA polymorphism analysis is useful, in addition to mtDNA haplotype assay, to detect “Inobuta” having the European genotype from Japanese wild boar populations.

The molecular phylogeny of 24 Oecophylla smaragdina populations and two O. longinoda populations was studied using 647 bp of the mitochondrial cyt b gene. The phylogenetic analysis suggested that O. smaragdina and O. longinoda were separated from each other first, and after that the first within-species divergence of O. smaragdina occurred in early stage of their history, in which the Asian, Australian, and Sulawesian groups rose. This grouping was almost coincident with the distribution of land-mass in glacial periods in Pleistocene. Thereafter, each group seemed to have independently diverged into present populations on each landmass.

Mitochondrial DNA (mtDNA) sequences (574 bp) of 30 Vietnamese pigs (large and small) were examined and compared with those of 61 haplotypes from wild boars and domestic pigs from various locations in Asia. The large Vietnamese pigs had genetic links to Ryukyu wild boars in southern Japan. The small Vietnamese pigs were closely related to other East Asian domestic pigs. These results indicate that Vietnamese pigs are genetically diverse and may be descendents of wild and domestic pigs from other regions of Asia.