Hiroomi Miyamoto

Complete mitochondrial genome sequences of the three pelagic chaetognaths Sagitta nagae, Sagitta decipiens and Sagitta enflata

The complete nucleotide sequences of the mitochondrial genomes were determined for the three pelagic chaetognaths, Sagitta nagae, Sagitta decipiens, and Sagitta enflata. The mitochondrial genomes of these species which were 11,459, 11,121, and 12,631bp in length, respectively, contained 14 genes (11 protein-coding genes, one transfer RNA gene, and two ribosomal RNA genes), and were found to have lost 23 genes that are present in the typical metazoan mitochondrial genome. The same mitochondrial genome contents have been reported from the benthic chaetognaths belonging to the family Spadellidae, Paraspadella gotoi and Spadella cephaloptera. Within the phylum Chaetognatha, Sagitta and Spadellidae are distantly related, suggesting that the gene loss occurred in the ancestral species of the phylum. The gene orders of the three Sagitta species are markedly different from those of the other non-Chaetognatha metazoans. In contrast to the region with frequent gene rearrangements, no gene rearrangements were observed in the gene cluster encoding COII-III, ND1-3, srRNA, and tRNA(met). Within this conserved gene cluster, gene rearrangements were not observed in the three Sagitta species or between the Sagitta and Spadellidae species. The gene order of this cluster was also assumed to be the ancestral state of the phylum.

A new deep-sea benthopelagic chaetognath of the genus Bathyspadella (Chaetognatha) with ecological and molecular phylogenetic remarks

A new chaetognath, Bathyspadella oxydentata, collected from Sagami Bay, central Japan, is described. The new species was collected from deep-sea benthopelagic habitat and is distinguished from the closely related species Bathyspadella edentata Tokioka, 1939 by the presence of teeth. The phylogenetic position of the new species was examined by molecular genetic analysis using partial sequences of 18S rRNA and 16S rRNA. Although B. oxydentata shares several morphological features with both Spadellidae and Eukrohnidae, the molecular phylogeny indicates that the new species is closely related to Heterokrohnidae species.

Detection of seagrass beds in Khunk Graben Bay, Thailand, using ALOS AVNI2 image

Coastal habitats having high productivity provide numerous ecological services such as foods, protection from strong waves through buffering effect, fixation of CO2 through photosynthesis, fostering biodiversity etc. However, increasing human impacts and climate change decrease or degrade coastal habitats. ASEAN region is developing most rapidly in the world. In the developing region, it is necessary to grasp present spatial distributions of habitats as a baseline data with standardized mapping methods. Remote sensing is one of the most effective methods for mapping. Japan Aerospace Exploration Agency (JAXA) provides non-commercial satellite images with ultra-high spatial resolution optical sensors (10 m), AVNIR2, similar to LANDSAT TM. Using ALOS AVNIR2 images it may be possible to make habitat map in the region. In Thailand, shrimp ponds cause degradation of coastal ecosystem through cutting mangroves and eutrophicated discharge from ponds. We examined capability of remote sesing with ALOS AVNIR2 to map seagrass beds in Khung Kraben Bay, Chanthaburi Province, Thailand, surrounded by shrimp ponds. We analyzed ALOS AVNIR2 taken on 25 January 2008. Ground truth survey was conducted in October 2010 using side scan sonar and scuba diving. The survey revealed that there were broad seagrass beds consisting of Enhalus acroides. We used a decision tree to detect seagrass beds in the bay with quite turbid seawater coupled with Depth-Invariant Index proposed by Lyzenga (1985) and bottom reflectances. We could succeed to detect seagrass beds. Thus it is concluded that ALOS AVNIR2 is practical to map seagrass beds in this region.

Phylogeography of the planktonic shrimp Lucifer hanseni Nobili 1905 in the Indo-Malayan Archipelago

Using partial sequences of two mitochondrial genes, cytochrome c oxidase subunit I (COI) and 12S ribosomal RNA (12S rRNA), and one nuclear gene, 28S ribosomal RNA (28S rRNA), we investigated population genetics of the holoplanktonic shrimp Lucifer hanseni Nobili, 1905 in the Indo-Malayan Archipelago (IMA), encompassing Andaman Sea, Malacca Strait, Gulf of Thailand, Borneo Island, Philippines (hereafter collectively referred to as the Thailand-Malaysia-Philippine area: TMP), Celebes Sea (CS), and the waters near islands in the Western Pacific (WP) including Palau, Papua New Guinea and Solomon Islands. The samples from the TMP showed the highest number of haplotypes. Significant phylogeographic structure was found in the L. hanseni populations (Φ ST = 0.832 for COI, 0.159 for 12S rRNA, 0.783 for 28S rRNA). The total number of haplotypes was 46 in COI, 28 in 12S rRNA and 23 in 28S rRNA. The haplotype network analyses revealed two major clades for COI (subgroups: TMP + CS, WP) and for 12S rRNA and 28S rRNA (TMP, CS + WP). The CS and WP populations appeared isolated from the TMP populations. The samples from the CS showed low genetic diversity compared with the other samples at both haplotype and nucleotide levels, suggesting that the population CS experienced bottleneck events. This is the first demonstration of significant genetic structure of a holoplanktonic metazoan in IMA, which is suggested to be synergistically influenced by historical events (vicariance) and contemporary oceanographic circulations and corroborates the results of previous studies on other benthic/demersal animals with mero-planktonic phases.