[Show abstract][Hide abstract] ABSTRACT: 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
[Show abstract][Hide abstract] ABSTRACT: The physical barriers in the meso- and bathypelagic layers of the open ocean are obscure compared with those in terrestrial, coastal, and ocean epipelagic habitats, which has led to the assumption that little genetic structure exists within deep-sea zooplankton species. Here, we show that the deep-sea chaetognath Eukrohnia hamata has differentiated genetically in habitats without obvious physical barriers. A partial nucleotide sequence of the mitochondrial COI gene was determined for E. hamata collected from the Pacific, Atlantic, and Antarctic oceans, with additional sequences from the congeneric species E. bathypelagica, E. bathyantarctica, and E. fowleri. In the resultant tree, E. hamata and E. bathypelagica, as defined by morphological taxonomy, formed a single lineage in which the two are intermixed. Within this lineage (E. hamata + E. bathypelagica) four major clades (Ham-A–D) were recognized, which showed genetic distances comparable to those between E. bathyantarctica and E. fowleri. Ham-A and D were distributed in the Antarctic and the North Pacific Oceans, respectively. Ham-B and C were cosmopolitan groups, with dominant areas in temperate and equatorial regions, respectively. Additionally, the grasping spines were furnished with distally oriented serration only in the Ham-D individuals. Our results provide evidence of genetic structure in the mtDNA of the assemblage of E. hamata and E. bathypelagica and indicate the necessity for further ecological and genetic studies using nuclear markers.
Progress In Oceanography 10/2012; 104:99–109. · 3.71 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: 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.
Journal of Natural History - J NATUR HIST. 01/2011; 45:2785-2794.
[Show abstract][Hide abstract] ABSTRACT: 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.
Comparative Biochemistry and Physiology Part D Genomics and Proteomics 03/2010; 5(1):65-72. · 2.88 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We investigated genetic diversity and structure of the deep sea chaetognath Caecosagitta macrocephala collected in the western North Pacific (Sagami Bay) and eastern Central to South Atlantic. All of the 52 specimens analyzed had unique haplotypes in their mitochondrial cytochrome c oxidase subunit I (mtCOI) gene sequences. Four distinct lineages of the mtCOI gene sequences (mtA, mtB, mtC, and mtD) were revealed by phylogenetic analysis with robust statistical support. The specimens collected from the Atlantic Ocean comprised three of the lineages (mtA, mtB, and mtD). All specimens of the remaining lineage (mtC) were obtained from Sagami Bay. The outgroup node was placed between the mtA lineage and lineages mtB, mtC, and mtD. Two specimens from each of the four lineages were randomly selected and the nuclear ribosomal internal transcribed spacer 1 (nITS1) region sequenced, resulting in ten forms, two of which were shared by all eight individuals. Phylogenetic relationships estimated from these sequences further supported the independence and reproductive isolation of the mtA individuals from the other lineages, while no phylogenetic structure was found in the mtB, mtC, and mtD lineages. These results indicate the presence of at least two cryptic species in C. macrocephala. Interestingly, these cryptic species were collected primarily from different depth layers (meso- and bathypelagic), suggesting speciation of the bathypelagic species from a mesopelagic precursor.
Deep Sea Research Part II Topical Studies in Oceanography 01/2010; · 2.24 Impact Factor