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Yokosuka, Japan

Jintsu Y.,University of Tsukuba | Uchifune T.,Yokosuka City Museum | Machida R.,University of Tsukuba
Arthropod Systematics and Phylogeny | Year: 2010

Structural features of the eggs of a basal phasmatodean, Timema monikensis Vickery & Sandoval, 1998 (Timematidae) were examined. The eggs of this species are soft and deposited coated with soil and/or other extraneous particles. The chorion, which is transparent and weakly sclerotized, is composed of an endochorion and an exochorion. The non-inclined operculum is located at the anterior pole of the egg. The chorion in the marginal region of the operculum is thinned to form an opercular collar together with the chorion of the egg body. An inverted triangular micropylar plate is on the ventral side of the egg attached to the opercular collar. The micropylar plate is without external differentiations but is specialized inside the chorion. A single micropyle, with a simple funnel-shaped chorionic opening, occurs on either side of the micropylar plate. The posterior mound, located at the posterior pole, is a thickened chorion rich in fi ne vertical striations, and the serosal cuticle beneath is thickened and highly specialized. The eggs of Timematidae were characterized and compared with those of Euphasmatodea and Embioptera. A phylogenetic discussion is presented, strongly supporting the assemblage of Timematodea, Euphasmatodea and Embioptera as monophyletic. © Museum für Tierkunde Dresden. Source

Manabe H.,Kagoshima University | Toyoda K.,Kagoshima University | Nagamoto K.,Kagoshima University | Dewa S.-I.,Diving Service Umi Annai | And 4 more authors.
Bulletin of Marine Science | Year: 2013

Bidirectional sex change in the gobies, Priolepis akihitoi Hoese and Larson, 2010, Priolepis cincta (Regan, 1908), Priolepis latifascima Winterbottom and Burridge, 1993, and Priolepis semidoliata (Valenciennes, 1837), was confirmed by rearing experiments. In female-female pairs, the larger individual changed sex to male, and in male-male pairs, the smaller changed to female. The gonads of these species simultaneously formed ovarian and testicular portions with an accessory gonadal structure. As the gonad structure in Priolepis borea (Snyder, 1909), Priolepis fallacincta Winterbottom and Burridge, 1992, and Priolepis inhaca (Smith, 1949) has the same form as in the above species, the latter are also likely to undergo bidirectional sex change. The natural occurrence of P. akihitoi, P. cincta, and P. semidoliata as solitary or paired (male and female) individuals inhabiting cave or rocky crevices suggests that the mating system of these species is monogamous. © 2013 Rosenstiel School of Marine & Atmospheric Science of the University of Miami. Source

Sunobe T.,Tokyo University of Marine Science and Technology | Hagiwara K.,Yokosuka City Museum
Journal of Applied Ichthyology | Year: 2013

Summary: Intersexual gonads were detected in three clupeiform species, Sardinops melanostictus, Sardinella zunasi and Englaulis japonicus, collected in Tokyo Bay off Yokohama City, Japan, of which appearance rates were 18.2, 34.6 and 33.9 %, respectively. While spermatogenesis proceeded normally in these individuals, previtellogenic stage oocytes were detected outside of the testes in the hermaphrodites, appearing as a single cell or small clusters. The results suggest that these species are non-functional hermaphrodites. As intersexual gonads have been reported in other clupeiform species collected before significant pollution and/or at sites far from urban influences, such non-functional hermaphrodites may be common occurrence in the order. However, high rates of hermaphrodite appearance also suggest the possibility that the development of these oocytes were induced by environmental estrogens. © 2012 Blackwell Verlag GmbH. Source

Shibata K.,Yokosuka City Museum | Ito M.,Chiba University | Nemoto N.,Kumamachi Elementary School | O'Hara S.,Teikyo Heisei University
Island Arc | Year: 2010

This paper examined sequence-stratigraphic features of a gravelly fluvial system of the Iwaki Formation, which developed in a forearc-basin setting in Northeast Japan during the Eocene through Oligocene. On the basis of three-dimensional architectural element analysis, we discriminated three major cycles of channel complexes, which contain ten component channel deposits in total in the fluvial succession. Component channel deposits in the uppermost part of each cycle are sandier and associated with overbank muddy deposits and coal beds as compared with those in the lower part of the cycle. Mean clast-size also decreases upsection in the entire gravelly fluvial deposits. The fluvial succession is interpreted to have been deposited in response to an overall rise in relative sea level that was superimposed by three short-term relative sea-level rises on the basis of vertical stacking patterns and component lithofacies features of channel deposits, and of correlation of the fluvial succession with an age-equivalent marine succession in an area about 50 km offshore. However, geometry and stacking patterns of the channel complexes do not exhibit any distinct temporal variation and amalgamated channel and bar deposits are dominant throughout the transgressive fluvial succession. On the other hand, an overall fining-upward pattern of the entire Iwaki Formation fluvial deposits in association with three component fining-upward patterns is distinct, and is interpreted to be consistent with the tenet of the standard fluvial sequence-stratigraphic models. This indicates that the present example represents one type of variation in the standard fluvial sequence-stratigraphic models, possibly reflecting the forearc-basin setting, which is generally represented by higher valley slope, higher shedding of coarse-grained sediments, and shorter longitudinal profiles to the coastal area as compared with a passive-continental-margin setting. © 2010 Blackwell Publishing Asia Pty Ltd. Source

Kato S.,University of Tokyo | Kato S.,University of Tsukuba | Sakayama H.,Kobe University | Morishima H.,Funabashi Kowagama High School | And 7 more authors.
Cytologia | Year: 2010

Chara altaica A. Braun (Charales, Charophyceae), a monoecious species of the section Desvauxia, was newly found in Japan and studied by light and scanning electron microscopy (SEM) as well as gene sequence analysis of the large subunit of Rubisco (rbcL). Our first SEM observations of C. altaica oospores revealed that small papillae were scattered on the fossa wall, an SEM oospore wall ornamentation that is essentially different from that of the monoecious species C. (sect. Desvauxia) evoluta T. F. Allen. Phylogenetic analysis demonstrated that C. altaica and 10 European samples of the dioecious species C. (sect. Desvauxia) canescens Desvaux & LoiseleurDeslongchamps formed a robust monophyletic group, in which the rbcL gene sequence from C. altaica is identical to those from 4 parthenogenetic samples, but different from 6 other bisexual and parthenogenetic samples of C. canescens. © 2010 The Japan Mendel Society. Source

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