Chromosomal DNA sequences of the Pacific saury genome: versatile resources for fishery science and comparative biology.

Pacific saury (Cololabis saira) is a commercially important small pelagic fish species in Asia. In this study, we conducted the first-ever whole genome sequencing of this species, with single molecule, real-time (SMRT) sequencing technology. The obtained high-fidelity (HiFi) long-read sequence data, which amount to ~30-folds of its haploid genome size that was measured with quantitative PCR (1.17 Gb), were assembled into contigs. Scaffolding with Hi-C reads yielded a whole genome assembly containing 24 chromosome-scale sequences, with a scaffold N50 length of 47.7 Mb. Screening of repetitive elements including telomeric repeats was performed to characterize possible factors that need to be resolved towards 'telomere-to-telomere' sequencing. The larger genome size than in medaka, a close relative in Beloniformes, is at least partly explained by larger repetitive element quantity, which is reflected in more abundant tRNAs, in the Pacific saury genome. Protein-coding regions were predicted using transcriptome data, which resulted in 22,274 components. Retrieval of Pacific saury homologs of aquaporin (AQP) genes known from other teleost fishes validated high completeness and continuity of the genome assembly. These resources are available at https://treethinkers.nig.ac.jp/saira/ and will assist various molecular-level studies in fishery science and comparative biology.

Basic Methods for the Study of Reproductive Ecology of Fish in Aquaria.

Captive-rearing observations are valuable for revealing aspects of fish behavior and ecology when continuous field investigations are impossible. Here, a series of basic techniques are described to enable observations of the reproductive behavior of a wild-caught gobiid fish, as a model, kept in an aquarium. The method focuses on three steps: collection, transport, and observations of reproductive ecology of a substrate spawner. Essential aspects of live fish collection and transport are (1) preventing injury to the fish, and (2) careful acclimation to the aquarium. Preventing harm through injuries such as scratches or a sudden change of water pressure is imperative when collecting live fish, as any physical damage is likely to negatively affect the survival and later behavior of the fish. Careful acclimation to aquaria decreases the incidence death and mitigates the shock of transport. Observations during captive rearing include (1) the identification of individual fish and (2) monitoring spawned eggs without negative effects to the fish or eggs, thereby enabling detailed investigation of the study species' reproductive ecology. The subcutaneous injection of a visible implant elastomer (VIE) tag is a precise method for the subsequent identification of individual fish, and it can be used with a wide size range of fish, with minimal influence on their survival and behavior. If the study species is a substrate spawner that deposits adhesive eggs, an artificial nest site constructed from polyvinyl chloride (PVC) pipe with the addition of a removable waterproof sheet will facilitate counting and monitoring the eggs, lessening the investigator's influence on the nest-holding and egg-guarding behavior of the fish. Although this basic method entails techniques that are seldom mentioned in detail in research articles, they are fundamental for undertaking experiments that require the captive rearing of a wild fish.

Evolution of bidirectional sex change and gonochorism in fishes of the gobiid genera Trimma, Priolepis, and Trimmatom.

Size-advantage and low-density models have been used to explain how mating systems favor hermaphroditism or gonochorism. However, these models do not indicate historical transitions in sexuality. Here, we investigate the evolution of bidirectional sex change and gonochorism by phylogenetic analysis using the mitochondrial gene of the gobiids Trimma (31 species), Priolepis (eight species), and Trimmatom (two species). Trimma and Priolepis formed a clade within the sister group Trimmatom. Gonadal histology and rearing experiments revealed that Trimma marinae, Trimma nasa, and Trimmatom spp. were gonochoric, whereas all other Trimma and Priolepis spp. were bidirectional sex changers or inferred ones. A maximum-likelihood reconstruction analysis demonstrated that the common ancestor of the three genera was gonochoristic. Bidirectional sex change probably evolved from gonochorism in a common ancestor of Trimma and Priolepis. As the gonads of bidirectional sex changers simultaneously contain mature ovarian and immature testicular components or vice versa, individuals are always potentially capable of functioning as females or males, respectively. Monogamy under low-density conditions may have been the ecological condition for the evolution of bidirectional sex change in a common ancestor. As T. marinae and T. nasa are a monophyletic group, gonochorism should have evolved from bidirectional sex change in a common ancestor.

Effects of restricted feeding on fetal and placental development in pregnant rabbits.

In our previous study on the effects of restricted feeding on pregnant rabbits (Matsuoka et al., 2009), animals given 20 g/day of diet on and after gestation day 6 (GD 6) showed significant changes in blood coagulation-related parameters suggesting a tendency to bleed and a decrease in serum concentration of progesterone, an important factor to maintain pregnancy, on GD 22, and a half of them showed serum progesterone concentrations less than 4.0 ng/ml which resulted in abortions on and after GD 23. In the present study, the effects of restricted feeding of 20 g/day from GD 6 to GD 22 on embryo-fetal and placental development on GD 23 as well as on blood coagulation-related parameters and serum progesterone concentrations on GD 22 were examined in pregnant rabbits. As compared with the non-restricted feeding (Not-treated, NT) group, the restricted feeding (RF) group showed lower values of platelets, fibrinogen, activated partial thromboplastin time (APTT) and antithrombin III (ATIII) and a longer prothrombin time (PT), reflecting an inhibition of blood coagulation, and a decrease in serum progesterone concentration on GD 22. Cesarean section performed on GD 23 revealed that the RF group showed a tendency towards an increase in the embryo-fetal death index and lower body weights and placental volumes compared with the NT group. Histological examination of the placenta in the RF group revealed that the labyrinth zone was thin and many glycogen-containing cells still remained in the basal zone, suggesting a delay in placental growth.

Changes in blood parameters in pregnant Japanese White rabbits.

Changes in blood parameters, especially those related to blood coagulations, were examined on gestational days (GDs) 6, 18 and 28 in Japanese White rabbits. As compared with the non-pregnant group, the following changes were observed in the pregnant group. For blood coagulation-related parameters, fibrinogen, platelets and antithrombin time III (ATIII) was significantly increased on GD 18 and/or GD 28, and activated partial thromboplastin time (APTT) was significantly prolonged on GDs 18 and 28. For the other hematological and blood chemical parameters, hemoglobin and hematocrit values were significantly decreased on GDs 18 and 28. Reticulocyte counts significantly and prominently increased on GD 18 and then decreased to significantly lower levels than those in the non-pregnant group on GD 28. Eosinophils and basophil showed significant decreases on GD 18 and/or GD 28. The serum progesterone concentration reached its highest level on GD 18. Total protein (TP), albumin, alkaline phosphatase (ALP), alanine aminotransferase (ALT), cholesterol, calcium, glucose and blood urea nitrogen were significantly decreased on GD 18 and/or GD 28. These results were almost similar to those in the pregnant New Zealand White rabbits (Mizoguchi et al., 2010).

Changes in blood parameters in New Zealand White rabbits during pregnancy.

Changes in clinical pathology parameters, particularly those related to blood coagulation, were examined throughout the gestation period in New Zealand White rabbits. As compared with the non-pregnant group, the following major changes were observed in the pregnant group. For blood coagulation-related parameters, platelets increased progressively and fibrinogen increased slightly from organogenesis, prothrombin time was significantly prolonged during organogenesis and shortened in the late fetal growth stage, activated partial thromboplastin time was significantly prolonged during the fetal growth stage, and antithrombin III increased during and after late organogenesis. Such changes in blood coagulation-related parameters during the later stages of gestation seem to be physiological responses in preparation for protecting against excessive haemorrhage or haemostasis at parturition. For the other haematological and blood chemical parameters as well as progesterone, red blood cell counts, haemoglobin and haematocrit began to decrease during organogenesis and continued to decrease thereafter. Reticulocyte counts significantly increased during organogenesis and decreased thereafter. White blood cell parameters, except for neutrophils, showed significant decreases during the fetal growth stage. Serum progesterone concentration reached its highest level early in organogenesis and decreased thereafter. Total protein, albumin, glucose, cholesterol, calcium, blood urea nitrogen and creatinine decreased significantly during the middle and/or late periods of gestation. In conclusion, the data obtained from the present study can be used as background data for effective evaluation of reproductive toxicology in rabbits, and pregnant rabbits may serve as models of pregnant women in research pertaining to clinical pathology and gestation.

Effects of restricted feeding on blood parameters in pregnant rabbits.

The effects of restricted feeding (20 g/day from gestational day (GD) 6 to 28) on pregnancy outcome and blood parameters were examined in pregnant rabbits. As compared with the group which was allowed free access to diet throughout the gestational period (NT group), the group subjected to restricted feeding (R group) showed significantly lower values in many parameters such as total protein, albumin and triglyceride on GDs 22 and 28, reflecting low nutritive conditions. In addition, there were significant changes in blood coagulation-related parameters, suggesting an imbalance between coagulation and anti-coagulation factors. Moreover, abortions occurred in about half of the animals of the R group between GDs 23 and 27. When aborted rabbits were compared with those which could maintain pregnancy under restricted feeding, total protein, albumin, platelets and antithrombin III values and especially blood progesterone concentration were significantly lower in aborted rabbits on GD 22, prior to occurrence of abortion. These results suggested that abortions due to restricted feeding might be brought about by lower nutritive conditions, an imbalance of blood coagulation-related factors and lower blood progesterone concentrations.

[Evaluation of Intra-abdominal fat distribution using X-ray CT data for detection of rectal cancer].

To develop a novel method of detecting rectal cancer, we assessed relationships between intra-abdominal fat distribution and rectal cancer in Japanese patients. Subjects comprised 38 patients with rectal cancer apparent on CT-colonography and 110 other cases. The intra-abdominal fat area was determined by calculating pixel distribution with attenuation values from -140 HU to -40 HU. The area of intra-abdominal fat was measured on axial images using an interslice gap of 10 mm. Profile curves of intra-abdominal fat were in the plane direction from diaphragm to anus. Of note is the fact that Ogura's peak, a secondary small peak around the rectal cancer, was apparent on the profile of intra-abdominal fat, with 73.7% of rectal cancers displaying Ogura's peak. In comparison, only 19.1% of other cases displayed Ogura's peak on this profile. The relationship between fat and rectal cancer is difficult to explain. However, making good use of these results showing intra-abdominal fat distribution, a computer-aided diagnosis (CAD) system for detecting rectal cancer according to the presence of Ogura's peak has potential as a method of mass screening. As only 148 cases were investigated in the present study, the accumulation of additional data is needed. More detailed studies with larger patient populations are warranted.