No abstract

No abstract

No abstract

Background: There is an increasing pressure on tropical species of the freshwater eel genus Anguilla for use in aquaculture, so species identification methods are needed to monitor these activities and to facilitate conservation efforts. A method was developed to genetically distinguish two subspecies of the Indonesian short-finned eel, Anguilla bicolor, based on an allelic discrimination technique. Results: A single DNA nucleotide substitution in the mitochondrial DNA 16S rRNA gene was employed to identify the two subspecies where Anguilla bicolor bicolor and Anguilla bicolor pacifica possessed adenine and guanine, respectively. This substitution was highly conserved at 100% in A. bicolor bicolor (108/108) and 99.9% in A. bicolor pacifica (181/182), and the misidentification rate was estimated to be 0.34%. Subsequently, fluorescent-labeled oligo probes and PCR primers were designed and succeeded to clearly distinguish the two subspecies. Further, the other ten anguillid species that may be sympatrically distributed with A. bicolor showed negative results. Conclusions: The method developed in this study is useful to accurately identify the two subspecies of A. bicolor and can contribute to ecological studies, stock management, and conservation.

To examine species composition and population structures in sand lance (Ammodytidae) along the northern Pacific coast of Japan, genetic analysis were carried out for specimens collected in 2014 from Otsuchi Bay, Iwate, Ishinomaki Bay, Miyagi, off Soma, Fukushima and Ise-Mikawa Bays, Aichi. The samples consisted of Ammodytes japonicus and Ammodytes heian, of which the latter is a recently described species. Neither species exhibited significant genetic differences among localities. Only A. japonicus was found in the most southern locality at Aichi, but it decreased northward to <90% in Miyagi and Fukushima and the two species occurred almost evenly in Iwate suggesting a latitudinal cline in their species composition along the northern Pacific coast of Japan, off Tohoku. The vertebral counts differed between A. japonicus and A. heian with modes of 65 and 63, respectively, but this characteristic did not differ significantly within a locality (Iwate). This suggests that the vertebral counts of Ammodytes spp. in Japanese waters are probably strongly determined by the environment than by a species-specific genetic trait.

Pseudapocryptes elongatus is one of the oxudercine gobies, which show varying degrees of amphibious behaviour and capacities to breathe air. There is little information on the early life history of P. elongatus, particularly of their morphology and larval habitat and duration. This study focused on the life history of larval and juvenile stages of P. elongatus investigated by genetic species identification, morphological observation and otolith analyses using specimens collected in June and October 2012 from estuaries in Bac Liêu Province, southern Vietnam (09°14′N 105°43′E). Genetically identified juvenile P. elongatus were characterized by (1) a slender body form, (2) the anterior edges of both the anal and second dorsal fins located at the midpoint along the body axis, (3) scarce chromatophores over the body surface, (4) melanophores in the parietal region between the eyes, and (5) a single row of melanophores along the base of the anal fin. Mean age at recruitment to estuaries was 38.0 ± 4.1 days, and otolith Sr/Ca ratios ranged from 8.9 to 9.9 mmol mol−1, suggesting that larval migration from their spawning sites requires more than 1 month in saline environments.

To investigate the effect of oxidative stress on the survival of two Brachionus species of rotifer, we examined the effective dose of juglone, which generates reactive oxygen species, and compared survival times between the two species. First, we observed that juglone affected survival in the rotifers in a dose-dependent manner between 0.02 to 20 lM, and that treatment at above 2 lM showed acute toxicity causing the animals to die within a few hours. Next, we found the difference in survival time between the two species exposed to 20 lM juglone: B. rotundiformis was significantly more tolerant against the substance than the allied species B. plicatilis. The findings suggest that exploring the basis of species-specific abilities to persist under oxidative stress will be of great interest to uncover the underlying mechanisms governing the stress resistance of the rotifer, as well as contributing to their stable mass production for aquaculture.

Echinoderms have a large coelomic cavity containing coelomocytes. When the coelomic fluid is removed from the cavity, the cells aggregate immediately. We found that a fraction or an extract of the intestine of the sea cucumber, Apostichopus japonicus, markedly accelerated cellular movement and aggregation on a glass slide, and this effect was clearly inhibited by galactose. We successfully purified the aggregation-promoting factor, a 16 kDa protein, from the intestine. TOF-MS analysis followed by de novo sequencing revealed that the protein is a C-type lectin. RNA-seq data and cDNA cloning demonstrated the factor to be a novel lectin, named AjGBCL, consisting of 158 aa residues in the mature form. Microscopic observation revealed that most of the aggregating cells moved toward aggregates and not to an intestinal fragment, suggesting that AjGBCL is not a chemoattractant but a cellular aggregation-inducing factor that may induce aggregates to release chemoattractant. We report, for the first time, an endogenous molecule that promotes coelomocyte aggregation in echinoderms.