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Zoological Letters

Atsushi Tokuoka, Taichi Q Itoh, Shinryo Hori, Outa Uryu, Yoshiki Danbara, Motoki Nose, Tetsuya Bando, Teiichi Tanimura, Kenji Tomioka
BACKGROUND: Animals exhibit circadian rhythms with a period of approximately 24 h in various physiological functions, including locomotor activity. This rhythm is controlled by an endogenous oscillatory mechanism, or circadian clock, which consists of cyclically expressed clock genes and their product proteins. cryptochrome (cry) genes are thought to be involved in the clock mechanism, and their functions have been examined extensively in holometabolous insects, but in hemimetabolous insects their role is less well understood...
2017: Zoological Letters
Jun Inoue, Yuuri Yasuoka, Hiroki Takahashi, Noriyuki Satoh
BACKGROUND: The T-box family transcription-factor gene, Brachyury, has two expression domains with discrete functions during animal embryogenesis. The primary domain, associated with the blastopore, is shared by most metazoans, while the secondary domain, involved in the notochord, is specific to chordates. In most animals, Brachyury is present in a single copy, but in cephalochordates, the most basal of the chordates, the gene is present in two copies, suggesting allotment of the two domains to each of the duplicates...
2017: Zoological Letters
Ko Katoh, Masazumi Iwasaki, Shouhei Hosono, Atsushi Yoritsune, Masanori Ochiai, Makoto Mizunami, Hiroshi Nishino
BACKGROUND: Facultative parthenogenesis, seen in many animal phyla, is a reproductive strategy in which females are able to generate offspring when mating partners are unavailable. In some subsocial and eusocial insects, parthenogenesis is often more prevalent than sexual reproduction. However, little is known about how social cooperation is linked to the promotion of parthenogenesis. The domiciliary cockroach Periplaneta americana is well-suited to addressing this issue as this species belongs to the superfamily Blattoidea, which diverged into eusocial termites and shows facultative parthenogenesis...
2017: Zoological Letters
Wanlada Klangnurak, Toshinobu Tokumoto
BACKGROUND: Two essential processes, oocyte maturation and ovulation, are independently induced, but proceed cooperatively as the final step in oogenesis before oocytes become fertilizable. Although these two processes are induced by the same maturation-inducing steroid, 17α, 20β-dihydroxy-4-pregnen-3-one (17, 20β-DHP), in zebrafish, it has been suggested that the receptor, and thus the signal transduction pathway is different for each process. Although much progress has been made in understanding the molecular mechanisms underlying the induction of oocyte maturation, the mechanisms for inducing ovulation remain under investigation...
2017: Zoological Letters
Marcelo R Sánchez-Villagra, Analía M Forasiepi
An overview of the literature on the chondrocranium of marsupial mammals reveals a relative conservatism in shape and structures. We document the histological cranial anatomy of individuals representing Monodelphis domestica, Dromiciops gliroides, Perameles sp. and Macropus eugenii. The marsupial chondrocranium is generally characterized by the great breadth of the lamina basalis, absence of pila metoptica and large otic capsules. Its most anterior portion (cupula nasi anterior) is robust, and anterior to it there are well-developed tactile sensory structures, functionally important in the neonate...
2017: Zoological Letters
Thomas Schwaha, Masato Hirose, Andreas Wanninger
BACKGROUND: Phylactolaemata is the earliest branch and the sister group to all extant bryozoans. It is considered a small relict group that, perhaps due to the invasion of freshwater, has retained ancestral features. Reconstruction of the ground pattern of Phylactolaemata is thus essential for reconstructing the ground pattern of all Bryozoa, and for inferring phylogenetic relationships to possible sister taxa. It is well known that Stephanella hina, the sole member of the family Stephanelllidae, is probably one of the earliest offshoots among the Phylactolaemata and shows some morphological peculiarities...
2016: Zoological Letters
Takahiro Hosokawa, Yu Matsuura, Yoshitomo Kikuchi, Takema Fukatsu
BACKGROUND: Diverse animals are intimately associated with microbial symbionts. How such host-symbiont associations have evolved is a fundamental biological issue. Recent studies have revealed a variety of evolutionary relationships, such as obligatory, facultative, and free-living, of gut bacterial symbiosis within the stinkbug family Pentatomidae, although the whole evolutionary picture remains elusive. RESULTS: Here we investigated a comprehensive assembly of Japanese pentatomid stinkbugs representing 28 genera, 35 species, and 143 populations...
2016: Zoological Letters
Jonas O Wolff, Thomas Schwaha, Michael Seiter, Stanislav N Gorb
BACKGROUND: Among both plants and arthropods, super-hydrophobic surfaces have evolved that enable self-cleaning, locomotion on water surfaces, or plastron respiration. Super-hydrophobicity is achieved by a combination of non-polar substances and complex micro- and nano-structures, usually acquired by growing processes or the deposition of powder-like materials. RESULTS: Here we report on a multi-phasic secretion in whip spiders (Arachnida, Amblypygi), which externally forms durable, hierarchical microstructures on the basically smooth cuticle...
2016: Zoological Letters
Daichi G Suzuki
BACKGROUND: This is the first report of two-headed (bicephaly) lamprey twins. Although lampreys sit at a crucial phylogenetic position, there are only a few reports on their teratology and developmental abnormalities. RESULTS: Two-headed mutants were obtained by artificial fertilization in the laboratory as spontaneous occurrences. All mutants were derived from single fertilizations using single male and female gametes, suggestive of a genetic background. The anterio-posterior position of the axonal bifurcation and symmetricity varied in each mutant...
2016: Zoological Letters
Nicolas Bekkouche, Katrine Worsaae
BACKGROUND: Diuronotus is one of the most recently described genera of Paucitubulatina, one of the three major clades in Gastrotricha. Its morphology suggests that Diuronotus is an early branch of Paucitubulatina, making it a key taxon for understanding the evolution of this morphologically understudied group. Here we test its phylogenetic position employing molecular data, and provide detailed descriptions of the muscular, nervous, and ciliary systems of Diuronotus aspetos, using immunohistochemistry and confocal laser scanning microscopy...
2016: Zoological Letters
Tatsuya Hirasawa, Yasuhiro Oisi, Shigeru Kuratani
BACKGROUND: The taxonomic position of the Middle Devonian fish-like animal Palaeospondylus has remained enigmatic, due mainly to the inability to identify homologous cranial elements. This animal has been classified into nearly all of the major vertebrate taxa over a century of heuristic taxonomic research, despite the lack of conclusive morphological evidence. RESULTS: Here we report the first comparative morphological analysis of hagfish embryos and Palaeospondylus, and a hitherto overlooked resemblance in the chondrocranial elements of these animals; i...
2016: Zoological Letters
Kazumi Matsubara, Chizuko Nishida, Yoichi Matsuda, Yoshinori Kumazawa
BACKGROUND: The discovery of differentially organized sex chromosome systems suggests that heteromorphic sex chromosomes evolved from a pair of homologous chromosomes. Whereas karyotypes are highly conserved in alethinophidian snakes, the degeneration status of the W chromosomes varies among species. The Z and W chromosomes are morphologically homomorphic in henophidian species, whereas in snakes belonging to caenophidian families the W chromosomes are highly degenerated. Snakes therefore are excellent animal models in which to study sex chromosome evolution...
2016: Zoological Letters
Takuma Takanashi, Midori Fukaya, Kiyoshi Nakamuta, Niels Skals, Hiroshi Nishino
BACKGROUND: Vibrational senses are vital for plant-dwelling animals because vibrations transmitted through plants allow them to detect approaching predators or conspecifics. Little is known, however, about how coleopteran insects detect vibrations. RESULTS: We investigated vibrational responses of the Japanese pine sawyer beetle, Monochamus alternatus, and its putative sense organs. This beetle showed startle responses, stridulation, freezing, and walking in response to vibrations below 1 kHz, indicating that they are able to detect low-frequency vibrations...
2016: Zoological Letters
Nicole R Rudolf, Carolin Haug, Joachim T Haug
BACKGROUND: Mole crabs (Hippidae) are morphologically distinct animals within Meiura, the "short-tailed" crustaceans. More precisely, Hippidae is an ingroup of Anomala, the group which includes squat lobsters, hermit crabs, and numerous "false" crabs. Within Meiura, Anomala is the sister group to Brachyura, which includes all true crabs. Most meiuran crustaceans develop through two specific larval phases. The first, pelagic one is the zoea phase, which is followed by the transitory megalopa phase (only one stage)...
2016: Zoological Letters
Madeleine Geiger, Karine Gendron, Florian Willmitzer, Marcelo R Sánchez-Villagra
BACKGROUND: It has been hypothesised that domestication altered the sequence of dental, skeletal, and sexual maturity of dogs when compared to their wolf ancestor. To test this we investigated a comprehensive sample of domestic dogs. METHODS: We documented the timing of completed eruption of permanent dentition into occlusion (dental maturity) and the timing of growth plate closure at the proximal humerus (skeletal maturity) in ontogenetic series of wolves and 15 domestic dog breeds...
2016: Zoological Letters
Marty Kwok-Shing Wong, Supriya Pipil, Haruka Ozaki, Yutaka Suzuki, Wataru Iwasaki, Yoshio Takei
BACKGROUND AND METHODS: Multiple Na+/K+-ATPase (NKA) α-subunit isoforms express differentially in response to salinity transfer in teleosts but we observed that the isoform nomenclature is inconsistent with the phylogenetic relationship of NKA α-genes. We cloned the catalytic NKA α-subunit isoforms in eels and medaka, analyzed the time course of their expressions in osmoregulatory tissues after transfer from freshwater (FW) to seawater (SW), and performed phylogenetic analyses to deduce an evolutionary scenario that illustrates how various duplication events have led to the current genomic arrangement of NKA α-genes in teleosts...
2016: Zoological Letters
Kumi Kaneko, Shota Suenami, Takeo Kubo
In the honeybee (Apis mellifera L.), it has long been thought that the mushroom bodies, a higher-order center in the insect brain, comprise three distinct subtypes of intrinsic neurons called Kenyon cells. In class-I large-type Kenyon cells and class-I small-type Kenyon cells, the somata are localized at the edges and in the inner core of the mushroom body calyces, respectively. In class-II Kenyon cells, the somata are localized at the outer surface of the mushroom body calyces. The gene expression profiles of the large- and small-type Kenyon cells are distinct, suggesting that each exhibits distinct cellular characteristics...
2016: Zoological Letters
Denis Audo, Joachim T Haug, Carolin Haug, Sylvain Charbonnier, Günter Schweigert, Carsten H G Müller, Steffen Harzsch
BACKGROUND: Modern representatives of Polychelida (Polychelidae) are considered to be entirely blind and have largely reduced eyes, possibly as an adaptation to deep-sea environments. Fossil species of Polychelida, however, appear to have well-developed compound eyes preserved as anterior bulges with distinct sculpturation. METHODS: We documented the shapes and sizes of eyes and ommatidia based upon exceptionally preserved fossil polychelidans from Binton (Hettangian, United-Kingdom), Osteno (Sinemurian, Italy), Posidonia Shale (Toarcian, Germany), La Voulte-sur-Rhône (Callovian, France), and Solnhofen-type plattenkalks (Kimmeridgian-Tithonian, Germany)...
2016: Zoological Letters
Hiroshi Miyanishi, Mayu Inokuchi, Shigenori Nobata, Toyoji Kaneko
BACKGROUND: During the course of evolution, fishes have acquired adaptability to various salinity environments, and acquirement of seawater (SW) adaptability has played important roles in fish evolution and diversity. However, little is known about how saline environments influence the acquirement of SW adaptability. The Japanese medaka Oryzias latipes is a euryhaline species that usually inhabits freshwater (FW), but is also adaptable to full-strength SW when transferred through diluted SW...
2016: Zoological Letters
Arun Rajendra Chavan, Günter P Wagner
BACKGROUND: The evolution of invasive placentation in the stem lineage of eutherian mammals entailed resolution of the incompatibility between a semi-allogenic fetus and the maternal immune system. The haemochorial placenta of nine-banded armadillo (Dasypus novemcinctus) is thought to conceal itself from the maternal immune system to some degree by developing inside a preformed blood sinus, with minimal contact with the uterine connective tissue. In the present study, we elucidate the micro-anatomical relationship between fetal and maternal tissue of the nine-banded armadillo using histochemical and immunohistochemical tools...
2016: Zoological Letters
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