Assessment of toxic effects of imidacloprid on freshwater zooplankton: An experimental test for 27 species.

The neonicotinoid pesticide imidacloprid has been used worldwide since 1992. As one of the most important chemicals used in pest control, there have been concerns that its run-off into rivers and lakes could adversely affect aquatic ecosystems, where zooplankton play a central role in the energy flow from primary to higher trophic levels. However, studies assessing the effects of pesticides at the species level have relied on a Daphnia-centric approach, and no studies have been conducted using species-level assessments on a broad range of zooplankton taxa. In the present study, we therefore investigated the acute toxicity of imidacloprid on 27 freshwater crustacean zooplankton (18 cladocerans, 3 calanoid copepods and 6 cyclopoid copepods). The experiment showed that a majority of calanoid copepods and cladocerans were not affected at all by imidacloprid, with the exception of one species each of Ceriodaphnia and Diaphasoma, while all six cyclopoid copepods showed high mortality rates, even at concentrations of imidacloprid typically found in nature. In addition, we found a remarkable intra-taxonomic variation in susceptibility to this chemical. As many cyclopoid copepods are omnivorous, they act as predators as well as competitors with other zooplankton. Accordingly, their susceptibility to imidacloprid is likely to cause different responses at the community level through changes in predation pressure as well as changes in competitive interactions. The present results demonstrate the need for species-level assessments of various zooplankton taxa to understand the complex responses of aquatic communities to pesticide disturbance.

Therapeutic efficacy of selective intra-arterial chemoradiotherapy with docetaxel and nedaplatin for fixed bulky nodal disease in head and neck cancer of unknown primary.

PURPOSE: Fixed bulky nodal disease in patients with head and neck cancer of unknown primary (HNCUP) remains difficult to treat. This retrospective study evaluated the therapeutic efficacy of selective intra-arterial chemoradiotherapy with docetaxel and nedaplatin for fixed bulky nodal disease in HNCUP. METHODS: Data from seven consecutive patients with fixed bulky nodal disease in HNCUP who had undergone selective intra-arterial chemoradiotherapy were analyzed. Whole pharyngeal mucosa and all bilateral nodal areas were irradiated (total dose 50 Gy), and bulky nodal lesions were provided an additional 20 Gy. Intra-arterial chemotherapy used a combination of nedaplatin (80 mg/m2) and docetaxel (60 mg/m2). Outcome measures were local control, disease-free survival, overall survival, and adverse events. Statistical analyses were performed using the Kaplan-Meier method. RESULTS: Median follow-up period was 24 months (range 9-64). All patients had extracapsular extension (N3b) on imaging and clinical findings. Symptoms due to bulky disease were neck discomfort (100%), tumor bleeding (43%), tracheal obstruction (14%), and carotid sinus syndrome (28%). Median value for maximum diameter of cervical disease was 84 mm (range 70-107), and 3-year local control, disease-free survival, and overall survival rates were 100, 54, and 64%, respectively. Symptoms due to bulky disease disappeared in all patients after intra-arterial chemoradiotherapy. Grade 4 leukopenia occurred in two patients (28%) as an acute adverse event. No other serious acute adverse events were observed. CONCLUSION: Selective intra-arterial chemoradiotherapy with docetaxel and nedaplatin can potentially achieve both favorable local control and survival in in HNCUP with fixed bulky nodal disease.

Therapeutic efficacy of selective intraarterial chemoradiotherapy with docetaxel and nedaplatin for human papilloma virus-negative oropharyngeal cancer.

OBJECTIVE: Human papilloma virus-negative oropharyngeal cancer has not achieved satisfactory outcomes compared with those of human papilloma virus-positive oropharyngeal cancer. This study evaluated the therapeutic efficacy of selective intraarterial chemoradiotherapy with the docetaxel and nedaplatin regimen for human papilloma virus-negative oropharyngeal cancer. METHODS: Twenty-two consecutive patients with human papilloma virus-negative oropharyngeal cancer who had undergone selective intraarterial chemoradiotherapy were retrospectively analyzed. The primary tumor and whole neck were irradiated (50 Gy). Subsequently, the primary site and metastatic lymph nodes were boosted by 20 Gy. The intraarterial chemotherapy regimen comprised a combination of nedaplatin (80 mg/m2) and docetaxel (60 mg/m2), which was initially administered at the start of radiotherapy and was given every 4 weeks for three sessions. Each intraarterial dose of an anticancer agent was determined according to the percentage of the tumor volume supplied by the target artery to the total tumor volume, which was intraoperatively measured via cone-beam computed tomography. The outcome measures were locoregional control, disease-free survival, and overall survival rates and adverse events. Statistical analyses were performed using the Kaplan-Meier method. RESULTS: The median follow-up period was 59 (range, 15-103) months. The T stage was T1/T2 in 5 patients (23%), T3 in 5 patients (23%), and T4 in 12 patients (54%). Cervical lymph node metastasis was staged as ≥N2c in 7 (32%) patients. Complete response was achieved in all patients at the first imaging examination after intraarterial chemoradiotherapy. The 5-year locoregional control, disease-free survival, and overall survival rates were 96% (95% confidence interval, 0.72-0.99), 91% (95% confidence interval, 0.68-0.98), and 100% (95% confidence interval, not available), respectively. Regarding serious acute adverse events, grade 4 laryngeal edema and leukopenia were observed in 1 (5%) and 11 patients (50%), respectively. No other serious acute adverse events were observed. CONCLUSION: Selective intraarterial chemoradiotherapy with docetaxel and nedaplatin has the potential to achieve favorable locoregional control, disease-free survival, and overall survival rates in human papilloma virus-negative oropharyngeal cancer.

Patterns of recurrence after low-dose postoperative radiotherapy for head and neck squamous cell carcinoma.

BACKGROUND: Postoperative chemoradiotherapy is recommended for patients with head and neck squamous cell carcinoma with positive margins or extracapsular extension at high risk of recurrence. However, high-dose radiotherapy in the head and neck region often causes severe acute and late radiation-related adversities. In our institution, the radiation dose has been relatively lower than that used in Western countries to reduce radiation-related toxicities. Therefore, in this study, we examined the treatment outcomes of low-dose postoperative chemoradiotherapy. METHODS: The outcomes of 90 consecutive head and neck squamous cell carcinoma patients who received postoperative radiotherapy between June 2009 and December 2016 were retrospectively analyzed. All patients received postoperative three-dimensional conformal radiotherapy with or without concurrent systemic chemotherapy. The median patient age was 65 years. Concurrent chemoradiotherapy was administered at a total dose of 50.4 Gy in 28 fractions (daily fraction, 1.8 Gy). High-risk patients received 10.8 Gy of boost irradiation in six fractions. For radiotherapy alone, the irradiation dose was up to 54 Gy in 30 fractions and 64.8 Gy in 36 fractions for high-risk patients to increase the treatment intensity. RESULTS: The median follow-up period was 40.5 months. The 3-year locoregional control and overall survival rates were 67.5% and 82.7%, respectively. A significantly higher proportion of patients with oral cavity carcinoma experienced locoregional failure (p = 0.004). The acute adverse events were mild, and the only late adverse event was grade 3 dysphagia (n = 3). CONCLUSION: This study suggests that de-escalation of the postoperative radiation dose can potentially reduce the severe adverse events of irradiation in patients while ensuring its effectiveness. In patients with oral cavity carcinoma, it might be necessary to increase the radiation dose.

Chemoembolization for Symptomatic Metastatic Epidural Spinal Cord Compression Refractory to Re-radiotherapy.

PURPOSE: To evaluate the efficacy of chemoembolization for inoperable metastatic epidural spinal cord compression (MESCC) refractory to re-radiotherapy. METHODS: Nineteen consecutive patients with recurrent MESCC after re-radiotherapy who had undergone chemoembolization were retrospectively analyzed. Outcome measures were pain relief rate, neurological improvement rate, objective response rate, and adverse events. MESCC degree classification was assessed using Bilsky grades. Pain assessment was performed using Numerical Rating Scale, and neurological function was evaluated using the Frankel classification. RESULTS: The median follow-up period was 7 (range 2-44) months. All participants had MESCC grade 2 or higher and had severe pain. Fifteen patients (79%) had neurological deficits, and ten had Frankel classification C and five had D. Symptoms were relieved in almost all patients the day following chemoembolization. Pain relief was achieved in 18 of 19 (95%) patients; the median decrease in Numerical Rating Scale score was 8 (range 0-10; p < 0.001). Neurological improvement was achieved in 11 of 15 patients (73%); the median increase in Frankel classification was 1 (range 0-2; p = 0.006). Ten of 19 (53%) patients showed a reduction in MESCC; the median decrease in Bilsky grade was 1 (range 0-2; p = 0.005). There was no correlation between the change in Bilsky grade and pain relief (p = 0.421). However, the decrease in Bilsky grade significantly improved neurological symptoms (p = 0.01). No serious adverse events occurred. CONCLUSION: Chemoembolization may be a useful palliative treatment modality for MESCC refractory to re-radiotherapy. LEVEL OF EVIDENCE: Level 3b, Follow up Study.

Transarterial Chemoembolization for the Palliation of Painful Bone Metastases Refractory to First-Line Radiotherapy.

PURPOSE: To compare the efficacy and safety of transarterial chemoembolization for the palliation of radiotherapy (RT)-failure bone metastases (BMs) with those of re-radiotherapy (Re-RT) in achieving pain relief. MATERIALS AND METHODS: Fifty consecutive patients with RT-failure BMs who had undergone Re-RT (23 patients) and transarterial chemoembolization (27 patients) were retrospectively analyzed. The primary endpoint was clinical response, and the secondary endpoints were objective response and adverse events. Pain assessment was performed using the numerical rating scale, and tumor response was evaluated using the modified Response Evaluation Criteria in Solid Tumors. Pain relief was defined as lack of pain with no analgesic usage (complete pain response) or a decrease in pain score by ≥3 points with analgesic usage (partial pain response). RESULTS: The pain relief rates in the Re-RT and transarterial chemoembolization groups were 57% and 92%, respectively (P = .006). The median pain relief duration was 2 and 3 months in the Re-RT and transarterial chemoembolization groups, respectively (P = .002). The 6-month pain-free survival rates were 30% and 51% in the Re-RT and transarterial chemoembolization groups, respectively (P = .08). The median tumor reduction rates were -4% and 9% in the Re-RT and transarterial chemoembolization groups, respectively (P < .001). The objective response rates were 0% and 11% in the Re-RT and transarterial chemoembolization groups, respectively (P = .29). No serious adverse events or complications were observed. CONCLUSIONS: Transarterial chemoembolization achieved a superior response rate and longer duration of palliation in symptomatic RT-failure BMs.

Predictive factors of posttreatment fracture by definitive radiotherapy for uterine cervical cancer.

PURPOSE: Fractures are known to shorten life expectancy and worsen the quality of life. The risk of fractures after radiation therapy in cervical cancer patients is known to be multifactorial. In this study, we examined risk factors for fractures in cervical cancer patients, especially by evaluating bone densities and DVH parameters for fractured bones. MATERIALS AND METHODS: For 42 patients, clinical characteristics, pretreatment CT bone densities, and radiation dose were compared between patients with and without fractures. RESULTS: Posttreatment fractures occurred in 25 bones among ten patients. Pretreatment CT bone densities were significantly lower in patients with fractures (P < 0.05-0.01 across sites, except for the ilium and the ischium). Although DVH parameters were also significantly associated with fractures in univariate analysis, only CT densities were significantly associated with fractures in multivariate analysis. CONCLUSION: Pretreatment CT densities of spinal and pelvic bones, which may reflect osteoporosis, have a significant impact on the risk for posttreatment fractures.

Indocyanine green fluorescence angiography for detection of cutaneous angiosarcoma of the scalp: A case report.

Cutaneous angiosarcoma is a rare neoplasm. One important predictor of recurrence is the resection margin; however, identifying the tissue area containing malignant cells is difficult. Indocyanine green fluorescence angiography (ICG-FA) has been used to identify superficial malignancies, including malignant tumors in the liver and sentinel lymph node metastasis of breast cancer. ICG-FA is also used to identify and define the resection margin of cutaneous angiosarcomas. However, there are currently only a few reports on the application of ICG-FA for detecting cutaneous angiosarcomas. We report a case of cutaneous angiosarcoma in the scalp in which one lesion, located in the parietal scalp, showed high fluorescence intensity corresponding exactly with the lesion was defined by physical examination, whereas the malignant area of the second lesion, located in the occipital scalp, was revealed more accurately by ICG-FA than by physical examination. Further, the second lesion was the first case diagnosed as angiosarcoma by the limited-area biopsy for a high-intensity area of ICG-FA. By determining where ICG is located within cutaneous angiosarcomas and quantitating the ICG intensity level corresponding to the malignant area, ICG-FA could be a promising tool for identifying cutaneous angiosarcomas.

Definitive radiotherapy consisting of whole pelvic radiotherapy with no central shielding and CT-based intracavitary brachytherapy for cervical cancer: feasibility, toxicity, and oncologic outcomes in Japanese patients.

BACKGROUND: This prospective study investigated the feasibility, toxicity, and oncologic outcomes of definitive radiotherapy (RT) consisting of whole pelvic radiotherapy with no central shielding (noCS-WPRT) and CT-based intracavitary brachytherapy (ICBT) in Japanese patients with cervical cancer. METHODS: Patients with cervical cancer of FIGO stages IB1-IVA were eligible. The treatment protocol consisted of noCS-WPRT of 45 Gy in 25 fractions and CT-based high dose-rate ICBT of 15 or 20 Gy in 3 or 4 fractions prescribed at point A. The prescribed ICBT dose was decreased if the manual dwell time/position optimization failed to meet organs-at-risk constraints. Graphical optimization and additional interstitial needles were not applied. RESULTS: We enrolled 40 patients. FIGO stages were IB1: 11, IB2: 13, IIA2: 1, IIB: 11, IIIB: 3, and IVA: 1. Median (range) pretreatment tumor diameter was 47 (14-81) mm. Point A doses were decreased in 19 of 153 ICBT sessions (12%). The median follow-up duration was 33 months. The 2-year rates of pelvic control, local control (LC), and progression-free survival were 83%, 85%, and 75%, respectively. Pre-ICBT tumor diameter, high-risk clinical target volume (HR-CTV), total HR-CTV D90, and overall treatment time (OTT) significantly affected LC. Late adverse events (grade ≥ 3) were observed in 3 patients (2 in the bladder, 1 in the rectum). CONCLUSIONS: Definitive RT consisting of noCS-WPRT and CT-based ICBT was feasible for Japanese patients with cervical cancer. To further improve LC, additional interstitial needles for patients with a large HR-CTV and shorter OTT should be considered.

Uterine artery embolization for postpartum and postabortion hemorrhage: a retrospective analysis of complications, subsequent fertility and pregnancy outcomes.

PURPOSE: To evaluate the impact of UAE for postpartum and postabortion hemorrhage on future infertility, especially in patients undergoing infertility treatment, along with angiographic endpoints. MATERIALS AND METHODS: Sixty-two sessions performed emergent or prophylactic UAE for postpartum or postabortion hemorrhage between 2008 and 2017 were selected. Subsequent pregnancy outcomes and complications were investigated as primary outcomes. The cases were divided into two groups based on the presence of massive hemorrhage. The relationships between angiographic endpoints and complications were also evaluated as secondary outcomes. RESULTS: The mean patient age was 34.1 ± 6.5 years. Fourteen of the 23 patients (60.9%) with desired fertility achieved pregnancy and 10 patients achieved live births (43.5%). In the patients during infertility treatment, three of the four patients had complications of severe adhesion after caesarean section or placenta accreta. In the group of patients with massive hemorrhage, the occurrence of uterine infection was significantly high (p = 0.014), but the angiographic endpoints were not significant, regardless of the occurrence of uterine infection. CONCLUSION: It was unnecessary to modify embolic endpoint according to seriousness of the hemorrhage. The pregnancy and live birth rates were acceptable, although patients undergoing infertility treatment had a higher rate of delivery complications.

Concomitant radiotherapy and transarterial chemoembolization reduce skeletal-related events related to bone metastases from renal cell carcinoma.

OBJECTIVES: The purpose of this study was to compare the efficacy of radiotherapy (RT) combined with transcatheter arterial chemoembolization (TACE) with RT alone for the treatment of bone metastases from renal cell carcinoma (RCC). METHODS: We included in this retrospective study 25 RCC patients (28 bone metastases), who were treated with RT at our institution. Patients were divided into two groups: patients treated with RT alone (monotherapy group; n = 17) and those treated with RT combined with TACE (combined therapy group; n = 11). The administered median RT dose was 30 Gy in 10 fractions. Anti-cancer agents used in TACE were cisplatin (median dose, 50 mg) and carboplatin (median dose, 240 mg) for patients with reduced renal function. We evaluated the objective response, post-RT-skeletal-related event (PR-SRE)-free rate, and adverse events associated with treatment for each group. RESULTS: The objective response rates for bone metastases in the monotherapy and combined therapy groups were 33% and 82%, respectively (p = 0.009). The 2-year PR-SRE-free rate in the monotherapy and combined therapy groups was 41.8% and 100%, respectively (p = 0.009). The objective response and PR-SRE-free rates were significantly superior in the combined therapy than in the monotherapy group. There were no significant differences in adverse events or survival between the two groups. CONCLUSION: RT combined with TACE is a promising treatment for bone metastases from RCC, as it results in higher objective response, and PR-SRE-free rates compared with RT alone. KEY POINTS: • Skeletal-related events (SREs) are common in patients with bone metastases from renal cell carcinoma (RCC). • Radiotherapy (RT) provides pain relief in patients with bone metastases from RCC, but rarely achieves objective response. • Combination of RT with transcatheter arterial chemoembolization results in higher objective response and post-RT-SRE-free rates compared with RT alone and is a promising treatment for bone metastases from RCC, as it.

Transcatheter arterial embolization for relapsed spinal metastatic paraganglioma: A case report.

Spinal metastasis is a rare presentation of paraganglioma and an effective therapy for nonresectable spinal metastatic paraganglioma (MPG) has not yet been established. We report the case of a 42-year-old woman with metastatic spinal cord compression caused by a relapsed spinal MPG after decompressive surgery. We performed transcatheter arterial embolization (TAE) in addition to systemic chemotherapy. After TAE, the neurologic symptoms improved, and the back pain was reduced. After 3 sessions of TAE, MRI revealed that the tumor at the level of the seventh thoracic vertebra had shrunk and the pressure on spinal cord had decreased. TAE might be a feasible treatment option for spinal MPG, even after surgery or irradiation.

Appropriate radiation dose for symptomatic relief and local control in patients with adult T cell leukemia/lymphoma.

Adult T-cell leukemia/lymphoma (ATL) is an aggressive peripheral T-cell neoplasm that occurs only in patients with human T-cell leukemia virus type 1. No large study or randomized trial investigating radiotherapy (RT) for ATL has been performed. We retrospectively reviewed 55 courses of RT for 41 consecutive patients with ATL who underwent RT between 2000 and 2016 at our institutions. The results showed that RT for local ATL lesions can achieve symptomatic improvement in 92% of cases. Local remission, either complete remission (CR) or partial response (PR), was achieved in 100% of the patients (CR: 89%, PR: 11%) with ≥40 Gy irradiation. CR or PR was achieved in 71% (CR: 29%, PR: 43%) with 30-39 Gy and in 73% (CR: 6.7%, PR: 67%) with ≤29 Gy irradiation. The mean total radiation dose in the CR and PR groups differed significantly (38 vs 25 Gy, P = 0.0002). The maximum acute toxicity was Grade 0-2 in all patients, except for one patient experienced Grade 3 radiation dermatitis. In-field relapses occurred in 36% of patients, and the frequency of in-field relapses was 11%, 30% and 71% among those who achieved CR, PR and SD, respectively. All 9 patients who received total skin irradiation experienced cutaneous relapses, with a median of 63 days (range, 7-210 days). Almost all (39 of 41) patients with ATL experienced out-of-field progression after RT. In conclusion, RT was confirmed to be effective and safe for palliative treatment of local ATL lesions.

Rediscovery after Almost 120 Years: Morphological and Genetic Evidence Supporting the Validity of Daphnia mitsukuri (Crustacea: Cladocera).

We examined the morphology of Daphnia individuals maintained in our laboratory for several years, originally collected in Lake Inbanuma, Chiba, Japan. We determined partial sequences of the mitochondrial cytochrome c oxidase subunit I and 12S rRNA genes from specimens in the cultured material. These animals are morphologically similar to D. obtusa Kurz, 1874 , but genetically distinct from this species. Our detailed observation shows that the morphological characteristics in the female and male individuals of our material are highly congruent with those of D. mitsukuri Ishikawa, 1896 , which has not been identified positively for more than 120 years since its original description, with its taxonomic identity having been questioned for almost 90 years. Based on our morphological and genetic data, we conclude that D. mitsukuri should be regarded as a taxonomically valid species. A search among public DNA sequence databases suggests D. mitsukuri is also distributed in China, although these Chinese sequences have been labeled as 'Daphnia pulex', representing misidentification.

Ecological and genetic impact of the 2011 Tohoku Earthquake Tsunami on intertidal mud snails.

Natural disturbances often destroy local populations and can considerably affect the genetic properties of these populations. The 2011 Tohoku Earthquake Tsunami greatly damaged local populations of various coastal organisms, including the mud snail Batillaria attramentaria, which was an abundant macroinvertebrate on the tidal flats in the Tohoku region. To evaluate the impact of the tsunami on the ecology and population genetic properties of these snails, we monitored the density, shell size, and microsatellite DNA variation of B. attramentaria for more than ten years (2005-2015) throughout the disturbance event. We found that the density of snails declined immediately after the tsunami. Bayesian inference of the genetically effective population size (Ne) demonstrated that the Ne declined by 60-99% at the study sites exposed to the tsunami. However, we found that their genetic diversity was not significantly reduced after the tsunami. The maintenance of genetic diversity is essential for long-term survival of local populations, and thus, the observed genetic robustness could play a key role in the persistence of snail populations in this region which has been devastated by similar tsunamis every 500-800 years. Our findings have significant implications for understanding the sustainability of populations damaged by natural disturbances.

Historical changes in the ecosystem condition of a small mountain lake over the past 60 years as revealed by plankton remains and Daphnia ephippial carapaces stored in lake sediments.

To examine if changes in species composition of a plankton community in the past due to anthropogenic activities can be clarified in lakes without any monitoring data, we analyzed genetically ephippial carapaces of Daphnia with plankton remains stored in the bottom sediments of Lake Hataya Ohunma in Japan. In the lake, abundance of most plankton remains in the sediments was limited and TP flux was at low levels (2-4 mg/m2/y) before 1970. However TP flux increased two-fold during the period from 1980s to 1990 s. In parallel with this increase, abundance of most plankton remains increased although abundance of benthic testate amoebae's remains decreased, indicating that the lake trophic condition had changed from oligo- to mesotrophic for the past 60 years. According to cluster analysis, the stratigraphic sediments were divided into two periods with different features of the phytoplankton composition. Chronological comparison with events in the watershed suggested that eutrophication occurred because of an increase in visitors to the watershed and deposition of atmospheric dust. In this lake more than 50% of resting eggs produced by Daphnia over the past 60 years hatched. However, genetic analysis of the ephippial carapaces (remains) showed that the Daphnia population was originally composed of D. dentifera but that D. galeata, or its hybrid with D. dentifera, invaded and increased the population density when the lake was eutrophied. Subsequently, large D. pulex established populations in the 1980s when largemouth bass were anonymously introduced. These results indicated that the Lake Hataya Ohunma plankton community underwent significant changes despite the fact that there were no notable changes in land cover or land use in the watershed. Since increases in atmospheric deposition and release of fish have occurred in many Japanese lakes, the changes in the plankton community described here may be widespread in these lakes.

Immediate ecological impacts of the 2011 Tohoku earthquake tsunami on intertidal flat communities.

Following the Great East Japan Earthquake in 2011, a large tsunami developed and struck the Pacific coast of eastern Japan. To assess the immediate impacts of the tsunami on coastal communities, changes in taxon composition and richness of macrobenthic animals before and after the tsunami were examined at nine intertidal flats in Sendai Bay and the Sanriku Ria coast. The results showed that 30-80% of taxa indigenously inhabiting intertidal flats disappeared after the tsunami. Among animal types, endobenthic and sessile epibenthic animals were more vulnerable to the tsunami than mobile epibenthic animals like shore crabs and snails. For all the intertidal flats examined, animals that were originally dwellers in lower tidal zones and not recorded before the tsunami were also found right after the tsunami, indicating that the tsunami not only took away many benthic taxa from the intertidal flats but also brought in some taxa from elsewhere. However, overall changes in taxon community composition were greater for intertidal flats that experienced larger inundation heights. These results showed that the ecological impacts of the tsunami were proportional to the physical impacts as gauged by wave height and that mobile epibenthic animals were less vulnerable to the tsunami.

Shifts in morphology and diet of non-native sticklebacks introduced into Japanese crater lakes.

An increasing number of exotic animals are causing ecological problems. Therefore, for better ecosystem management, it is important to understand how exotic species colonize and adapt to novel environments. The threespine sticklebacks (Gasterosteus aculeatus) can be a good vertebrate model system to explore the ecological and genetic mechanisms of adaptation not only in natural populations, but also in non-native populations. Although morphological changes have been documented in several introduced populations of stickleback, little is known about the dietary changes during colonization into novel environments. Here, we investigated the morphological and dietary changes of exotic threespine stickleback populations introduced into three Japanese crater lakes (Lake Towada, Lake Kussharo, and Lake Shikotsu). Sticklebacks were introduced into the crater lakes likely along with salmonids transplanted for aquaculture. The stickleback population in Lake Kussharo had multiple mitochondrial haplotypes and had larger phenotypic variances than other crater lake stickleback populations that had only one mitochondrial haplotype. Compilation of historical data on the morphology and stomach contents of the Lake Towada stickleback population showed that substantial shifts in body size and stomach contents occurred after colonization. Some of these changes may be related to an outbreak of the Schistocephalus parasite. These results suggest that sticklebacks can change their morphology and trophic ecology when they colonize novel environments. Therefore, extreme care should be taken when salmonids are transported between watersheds for aquaculture and that long-term monitoring of exotic species is essential for ecosystem management. In addition, further genetic studies on phenotypic changes in crater lake sticklebacks would help elucidate the genetic mechanisms underlying the adaptation of exotic fishes to novel environments.

The long-term consequences of hybridization between the two Daphnia species, D. galeata and D. dentifera, in mature habitats.

BACKGROUND: Ecological specializations such as antipredator defense can reinforce morphological and distributional divergence within hybridizing species. Two hybridizing species of Daphnia (D. galeata and D. dentifera) are distributed in both Japan and North America; however, these populations have a longer history in Japan than in North America due to the differing impact of the last glaciation on these two regions. We tested the hypothesis that this longer coexistence in Japan would lead to extensive genetic admixture in nuclear and mitochondrial DNA whilst the distinct morphological traits and distributional patterns would be maintained. RESULTS: The high level of correspondence among morphological traits, distribution, and mitochondrial and nuclear DNA types for the specimens with D. dentifera mtDNA indicated that the species distinction has been maintained. However, a discordance between mtDNA and nuclear ITS-1 types was observed for most specimens that had D. galeata mtDNA, consistent with the pattern seen between the two species in North America. This observation suggests nuclear introgression from D. dentifera into D. galeata without mitochondrial introgression. CONCLUSIONS: The separation of morphological traits and distribution ranges of the two hybridizing species in Japan, as well as in North America, has been maintained, despite large differences in climatic and geographical histories of these two regions. Variations in environmental factors, such as predation pressure, might affect maintenance of the distribution, although the further studies are needed to confirm this.