Heterotrimeric G proteins play crucial roles as mediators of signaling by many extracellular stimuli. The receptors that activate G proteins constitute the largest and most diverse family of cell surface molecules involved in signal transmission of metazoan cells. To investigate G protein signaling in the central nervous system (CNS) of chordates, we isolated cDNA fragments encoding five different G protein α subunits (CiGα_x, CiGα_q, CiGα_i1a, CiGα_i1b, and CiGα_i2) from larvae of the ascidian, a simple chordate, Ciona intestinalis. In situ hybridization analysis revealed that each isoform had distinct patterns of spatial distribution in embryos. Among them, CiGα_i1a and CiGα_i1b mRNAs were specifically expressed in the CNS of the larva, whereas CiGα_q transcripts were expressed in small parts of the trunk epidermis and the tip of the tail, but not in the CNS. The CiGα_x expression was widely observed throughout the trunk and tail of the embryos, and the signals were stronger in the epidermis, mesenchyme, and tail muscle cells. Comparison of cDNA sequences and the exon-intron organization indicate that CiGα_i1a and CiGα_i1b are produced by alternative splicing of transcripts from a single gene, CiGα_i1. In the cleavage and gastrula stages, transcripts of CiGα_i1 were widely distributed in embryos, and the expression then became restricted to the CNS of tailbud embryos and larvae. An exhaustive search has failed to find transducin-type α subunits in C. intestinalis. Since CiGα_i1 is expressed in the ocellus, CiGα_i1 may mediate signals from Ci-opsin1, a visual pigment of the ocellus photoreceptor cells.

Cell growth of anaerobic protozoan Tritrichomonas foetus was analyzed. This protozoan usually proliferates in extremely high density, but protozoan parasites were dispersed uniformly in F-bouillon medium and cell division stopped temporarily. However, nuclear fission continued and giant polynucleated cells formed. Later, cell division resumed and cells returned to normal form. In conditioned medium, cytokinesis of the dispersed parasites did not stop. Results indicated that T. foetus cells secreted an extra-cellular factor that influenced cytokinesis.

We developed a method for preparing starfish chromosomes from embryos. Blastulae were treated with colchicine (0.2–4.0 mg/ml), dissociated into single blastomeres by pippeting, swollen with 7% sodium citrate, and fixed with methanol: acetic acid (3:1). The fixed cells were dropped on a slide and air-dried. We examined the chromosome number in five species of asteroids belonging to 4 families (Luidiidae, Astropectinidae, Asterinidae, and Asteriidae), and all had a diploid number of 44. We analyzed the karyotype in 4 of the species, and all were different. We visualized the nucleolus organizer regions of an Asterina species and an Asterias species and found them to be quite different from each other.

We previously reported that characteristic deformities were induced by retinoic acid (RA) treatment of the Japanese flounder, Paralichthys olivaceus, at 6–9 days post-hatching (dph). To evaluate the toxic potency of nuclear retinoid receptors in induction of deformities by RA, we here investigated the effects of retinoic acid isomers on postembryonic development of this species. Larvae were exposed to either 25 nM of all-trans RA (atRA), 9-cis RA (9cRA) or 13-cis RA (13cRA) at 6–9 dph. All RA isomers induced deformities in the lower jaw, caudal fin and vertebrae. In the lower jaw, growth retardation of the dentary was evident. In the vertebrae, the major abnormalities were hypertrophy of the centrum, central fusion, and an increase in the number of abdominal vertebrae. Caudal fin deformities included deformity of caudal bone complex and absence of the entire caudal fin. The absence of the hypural primordium at 12 dph was the first sign of abnormality in caudal fin development, and resulted in complete blocking of the caudal fin development. Among the RA isomers, atRA induced the most severe deformity in all skeletons examined. Retinoic acid receptor (RAR) expression was activated by atRA and 9cRA, and pitx2 expression was inhibited in the lower jaw by atRA and 9cRA. Vitamin D receptor (VDR) expression was specifically inhibited by atRA treatment, suggesting that RA inhibits the lower jaw growth by suppressing the expression of these genes. These results suggest that RA exerted toxic effects on the skeletal systems, mainly through the RAR pathway.

The auricularia larva of sea cucumbers and tornaria larva of acorn worms share striking developmental and morphological similarities. They are regarded as not only an archetype of the nonchor-date deuterostome larva, but also an archetype of the origin of chordates. Here we report the characterization and spatial expression patterns of the BMP-2/4 genes of a hemichordate acorn worm (Pf-bmp2/4) and an echinoderm sea cucumber (Sj-bmp2/4). Both the Pf-bmp2/4 and Sj-bmp2/4 genes exhibited apparently conserved expression in the region of the coelomopore complex. This is in agreement with the homology between their basic larval body plans with respect to coelomogenesis and allows us to discuss the evolutionary counterparts of the coelomopore complex in chordates.

The planarian Dugesia japonica has two genes encoding myosin heavy chain, DjMHC-A and B (Kobayashi et al., 1998). We produced antibodies specifically recognizing each myosin heavy chain protein using their carboxyl terminal regions expressed in E. coli as antigens. Immunohistochemical analyses of sections and whole-mount specimens revealed the detailed structure and distribution of each type of muscle fiber in the planarian. In general, the MHC-A muscle fibers were distributed beneath the epithelial layers, namely, they were observable in the pharynx, the mouth, the intestine, the eyes and the body wall. In the pharynx, only MHC-A muscle fibers were present. In contrast, the MHC-B muscle fibers were distributed in the mesenchyme as dorso-ventral and transverse muscles, and in the body wall. The body-wall muscles were composed of an outer layer of circular MHC-A muscles and inner longitudinal and intermediate diagonal MHC-B muscle layers. Thus, two types of muscle fibers were distinguished by their distribution in the planarian.

Korean populations of the genus Cryptocercus occur in forested mountains throughout South Korea. They live in monogamous associations in which parents care for their young in complex woody galleries. Single paired adults (23.2%) and one or both parents with their offspring (28.1%) were found most frequently in the field. Among single-parent families adult females (6.7%) were observed more frequently than adult males (1.4%). In families with single or both parents, the mean brood size was 21.6±9.4. Oothecae were observed from mid-June to the late July. Oothecae were found in the galleries of only paired adults and never found in families with nymphs. The mean number of eggs per female was 73.7±29.8. Most of neonates grew to the third or fourth instar prior to the winter. During the winter, C. kyebangensis in the field remained almost frozen in their galleries, but ones kept in the laboratory continued to grow during winter. Some characteristics of proctodeal feeding behavior are also described based on laboratory observations. We propose that the cold temperate climate, especially of the winter season, is one of the most important causes for the evolution of unusual life history of Cryptocercus including delayed development of nymphs.

Dispersal ability and degree of inbreeding in a population can indirectly be assessed using genetic markers. In general, it was suggested that winged termites are not able to fly distances greater than several hundred meters. Here, amplified fragment length polymorphism (AFLP) was used to analyze genetic diversity, population substructure, and gene flow among insular populations of the termite Nasutitermes takasagoensis (Isoptera: Termitidae) in the Yaeyama Islands, Okinawa, Japan. Samples were collected from 77 nests on seven islands of the Yaeyama Group. Using three primer combinations a total of 155 bands were generated with 78 (50%) polymorphic bands. Genetic distance and G_st values among insular populations were calculated. Relatively high genetic diversity and low values of G_st, suggest there is moderate subpopulation structure. Based on these results, we discussed two possibilities; first, winged termites are able to fly over distances of several kilometers, and second, these results were obtained because insular populations share a recent common origin.

A new species of the groundwater amphipod Salentinella (Crustacea, Salentinellidae), S. anae, is described from Spain. This species is characterised by spines on the antennula peduncle, the absence of retinaculae on the pleopods, and the morphology of the coxal plate 1. Different morphological characters are evaluated before a phylogenetic study of the family. Salentinella prognatha is assigned as a synonym of S. petiti. The description of the genus Parasalentinella, as well as the diagnosis of the Salentinellidae are completed.

Cuticular hydrocarbons and morphological features were compared among 80 Formica japonica colonies collected in Japan. Although a few morphological differences were found in workers among the colonies, four different types of cuticular hydrocarbon composition were observed. This was supported by a principal component analysis. We further compared the cuticular hydrocarbons among a total of approximately 400 F. japonica colonies, and categorized the hydrocarbon components into four types based on the result of discriminant analyses for the first 80 colonies. Type 1 was observed in colonies mainly collected in southern Honshu, Shikoku, and Kyushu. Types 2, 3, and 4 were from colonies with primary collections in Southern Honshu, central and Pacific coast northern Honshu, and the Sea of Japan coasts of northern Honshu and Hokkaido, respectively. The occurrence of four distinct types of CHC composition suggests that the colonies that produce them are separate species.

Rimicaris kairei new species (Alvinocarididae: Caridea: Decapoda) is described based on materials, from the active hydrothermal vent field, “Kairei Field,” on the Central Indian Ridge, the Indian Ocean. The new species is clearly distinguishable from the unique congener, R. exoculata Williams & Rona, 1986, which is known from the Atlantic Ocean. The following morphological differences were identified: (1) all punctations on carapace strongly ornamented by tufts of short stiff setae in R. exoculata, whereas without any setae in R. kairei; (2) antennal flagella in R. exoculata shorter than in R. kairei; (3) walking legs in R. exoculata more robust than in R. kairei.

Examination of thin sections of trunk wall in an old specimen of Ikeda taneioides from Misaki, Sagami Bay revised previous false information about the wall musculature, actually consisting of outer circular, middle longitudinal, and inner-most oblique layers, like all other echiurans. This finding, together with the reexamination of relevant museum specimens, led to some taxonomic changes. These include that the definition of the genus Ikeda was amended to be a senior synonym of Prashadus; the family Ikedidae was regarded as a junior synonym of the family Echiuridae; and the order Heteromyota, erected virtually for I. taenioides, was abolished. Non-discovery of males and some other features in the amended genus Ikeda were noted with reference to its possible relationship with the family Bonelliidae.

Megalodicopia hians Oka is a solitary ascidian belonging to the family Octacnemidae inhabiting the bathyal /abyssal zone as well as other octacnemid ascidians. The phylogenetic relationship of octacnemids is open to argument because of its extraordinary morphological features due to habitat adaptation, e.g., a pharynx lacking ciliated stigmata. Aggregations of M. hians were discovered by the manned submersible Shinkai 2000 in the bathyal seafloor of Toyama Bay, Japan Sea, in 2000; this was the first in situ observation of M. hians in the Japanese coastal waters. In 2001, a total of 36 M. hians specimens were collected from the bay (592∼978 m deep). In situ observation indicated that M. hians usually opens its large oral apertures to engulf the drifting food particles in the water current. Microscopical observation of the gut contents also showed that M. hians is a non selective macrophagous feeding on small crustaceans, diatoms, detritus, and so on. Along with the position of the intestinal loop and gonad, the morphological characteristics of the tunic (integument of ascidians) suggest that M. hians is closely related to Cionidae and/or Corellidae. Some symbiotic/parasitic organisms were occasionally found in the tunic, including rod-shaped bacteria, fungi-like multicellular structure, and spawns of unknown animals.

In Drosophila elegans, two morphs are known, the brown-morph occurring from southern China to Indonesia and the black-morph occurring in the Ryukyu Islands, Japan, and Taiwan, and brown-morph populations at high altitudes in Indonesia at least sympatrically occur with a sibling species D. gunungcola. Sexual isolation has developed between the two morphs of D. elegans to some extent; females of the black-morph have a higher concentration of pentacosenes on cuticle than those of the brown-morph, and males of these morphs discriminate between the females based on this difference. In this study, it was examined whether sympatry and allopatry with D. gunungcola have resulted in the differentiation of mate recognition system in D. elegans. No significant difference was observed in the degree of mate discrimination between a sympatric pair of D. elegans and D. gunungcola and their allopatric pairs. Thus, no support was obtained for the above notion. Males of the brown- and black-morphs of D. elegans discriminate between females of own morphs and D. gunungcola. However, brown-morph males did not discriminate between females of the black-morph and D. gunungcola, and also black-morph males did not discriminate between females of the brown-morph and D. gunungcola. This may be attributed to that D. gunungcola females retained an intermediate level of pentacosenes between brown- and black-morph females.