We studied the spawning seasonality and gonadal development of blue marlin Makaira nigricans using specimens captured around Yonaguni Island in southwestern Japan between February 2003 and February 2006. The mean (±SD) lower jaw-fork length of females (234 ± 24 cm) was greater than that of males (191 ± 12 cm). The smallest mature female and male were 183 and 160 cm, respectively. Most of the 717 females had immature ovaries. However, in March and from May to September, the ovaries of 26 females contained oocytes with yolk globules, hydrated oocytes, or postovulatory follicles. Most males had testes with a large amount of spermatozoa throughout the year. The occurrence of mature blue marlin at Yonaguni Island suggests that spawning occurs here. The mean condition factors (fatness of the fish) of both sexes decreased from March to June or July, presumably as they expended energy to reproduce. We discuss our results in the context of migration theory for blue marlin in the western North Pacific Ocean.

An investigation was conducted to determine whether differences in host size of different species affect the body size, fecundity, and longevity of Trissolcus mitsukurii, a solitary egg parasitoid of stink bugs. The eggs of the Pentatomid bugs of Halyomorpha halys (large size), Plautia crossota stali (middle size), and Nezara viridula (small size) were supplied to T. mitsukurii and incubated until progeny emerged at 25Ϯ2°C and a photoperiod of LD 16 : 8. Both male and female parasitoids emerged with larger body sizes when they developed in large host eggs such as H. halys. Larger size parasitoids had greater longevity and larger size females showed higher fecundity.

We aimed to investigate why the incidence of embryos derived from oocytes with no pronuclei (0PN) decreases using time-lapse monitoring (TLM) versus fixed-point assessment in conventional IVF cycles. We analyzed 514 embryos monitored with TLM 6–9 h after insemination and 144 embryos monitored using microscopic assessment 18–21 h after insemination. The primary endpoint of this study was the incidence of 0PN-derived embryos in short insemination followed by TLM. The secondary endpoint was the duration of insemination. As exploratory endpoints, we analyzed the blastulation rate and cryo-warmed blastocyst transfer outcome of embryos with early PN fading, whereby PN disappeared within < 20 h following the initiation of insemination. The incidence of 0PN-derived embryo reduced more significantly through TLM than through fixed-point observation. The microscopic assessment time was more significantly delayed in the 0PN-derived embryo than that in the 2PN-derived embryo. The embryo with early PN fading formed good-quality blastocysts, and their pregnancy outcomes were similar to those of other embryos. Most 0PN-derived embryos in the fixed-point assessment might have resulted from missed observation of PN appearance in the early-cleaved embryos. TLM or strict laboratory schedule management may reduce 0PN-derived embryos by reducing missed PN observations.

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Study question Can a scoring model based on morphokinetic data developed to predict pregnancy rates of day–5 blastocyst transfers (KIDSCORE™D5) predict pregnancy rates of day–6 blastocyst transfers? Summary answer KIDSCORE™D5 was able to predict the clinical pregnancy rates of embryo transfers done on day 6 with an area under the curve (AUC) of 0.72. What is known already KIDSCORE™D5 is a scoring model based on morphokinetic data developed to predict the pregnancy rates of day–5 blastocysts. In 2019, Regnier et al. reported that the AUC of KIDSCORE™D5 for predicting clinical pregnancy rates of day–5 blastocyst transfers was 0.6. However, as KIDSCORE™D5 is constructed based on morphological characteristics and developmental dynamics of day–5 blastocysts, it is unclear whether KIDSCORE™D5 can predict pregnancy rates of day–6 blastocyst transfers. Since there are many cases of day–6 blastocyst transfers, it is important to know if KIDSCORE™D5 can predict pregnancy rates of day–6 blastocyst transfers. Study design, size, duration This retrospective single-center study, which included 162 day–5 and 72 day–6 blastocyst transfers, respectively, was conducted at Takahashi Women’s clinic from January to December 2019. Blastocysts derived from 146 patients who underwent intracytoplasmic sperm injection. All blastocysts were cryopreserved and were transferred singly. Participants/materials, setting, methods We used EmbryoScope+™ (Vitrolife) for in-vitro culture and calculated KIDSCORE™D5 (ver.3) using Embryoviewer™ (Vitrolife). Blastocyst scoring was done from 1.0 to 9.9. Clinical pregnancy was defined as the presence of a gestational sac confirmed by transvaginal ultrasonography. Statistical analysis was performed with JMP Pro 15.00 (SAS). The relationship between KIDSCORE™D5 and clinical pregnancy was evaluated by the AUC using ROC curve analysis and multivariate analysis adjusted for patient age. Main results and the role of chance The mean KIDSCORE™D5 of day–5 and day–6 blastocysts was 7.1±1.7 and 3.7±1.5, respectively. KIDSCORE™D5 of day–6 blastocysts was significantly lower than that of day–5 blastocysts (p &lt; 0.0001, Wilcoxon test). ROC curve analysis showed that the KIDSCORE™D5 could predict clinical pregnancy rates with an AUC of 0.62 for day–5 blastocysts and 0.72 for day–6 blastocysts. The cut-off values for KIDSCORE™D5 were 5.7 and 4.9 for day–5 and day–6 blastocysts, respectively. Blastocysts above the cut off value on both day–5 and day–6 had a significantly higher pregnancy rate than those below the cut off value (day–5: 61.9% vs. 33.3%(p = 0.0023), day–6: 47.4% vs. 7.6%(p = 0.0003)). Multivariate analysis adjusted for patient age showed that KIDSCORE™D5 correlated with clinical pregnancy rates of days 5 and 6 of blastocyst transfer with AUCs of 0.66 and 0.73, respectively. Limitations, reasons for caution This study had a small sample size, and it was a retrospective single-center study. In addition, the relationship between KIDSCORE™D5 and clinical pregnancy rates may vary among facilities. Therefore, a prospective multicenter validation is necessary. Wider implications of the findings: Our study results indicated that KIDSCORE™D5 predicted clinical pregnancy and that morphokinetic parameters related to clinical pregnancy were similar between day–5 and day–6 blastocysts. Hence, morphokinetic evaluation can serve as a criterion for deciding which of multiple day–6 blastocysts can be transferred. Trial registration number Not applicable