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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
Daichi G Suzuki, Yuma Fukumoto, Miho Yoshimura, Yuji Yamazaki, Jun Kosaka, Shigeru Kuratani, Hiroshi Wada
The ancestral configuration of the vertebrate head has long been an intriguing topic in comparative morphology and evolutionary biology. One peculiar component of the vertebrate head is the presence of extra-ocular muscles (EOMs), the developmental mechanism and evolution of which remain to be determined. The head mesoderm of elasmobranchs undergoes local epithelialization into three head cavities, precursors of the EOMs. In contrast, in avians, these muscles appear to develop mainly from the mesenchymal head mesoderm...
2016: Zoological Letters
Federico Fanti, Daniela Minelli, Gabriele Larocca Conte, Tetsuto Miyashita
BACKGROUND: Following extreme climatic warming events, Eocene Lagerstätten document aquatic and terrestrial vertebrate faunas surprisingly similar to modern counterparts. This transition in marine systems is best documented in the earliest teleost-dominated coral reef assemblage of Pesciara di Bolca, northern Italy, from near the end of the Eocene Climatic Optimum. Its rich fauna shows similarities with that of the modern Great Barrier Reef in niche exploitation by and morphological disparity among teleost primary consumers...
2016: Zoological Letters
Tanya J Shaw, Molly Osborne, Giovanna Ponte, Graziano Fiorito, Paul L R Andrews
BACKGROUND: Octopoda utilise their arms for a diverse range of functions, including locomotion, hunting, defence, exploration, reproduction, and grooming. However the natural environment contains numerous threats to the integrity of arms, including predators and prey during capture. Impressively, octopoda are able to close open wounds in an aquatic environment and can fully regenerate arms. The regrowth phase of cephalopod arm regeneration has been grossly described; however, there is little information about the acute local response that occurs following an amputation injury comparable to that which frequently occurs in the wild...
2016: Zoological Letters
Michael Griesser, Toshitaka N Suzuki
Cooperative breeding is a widespread and intense form of cooperation, in which individuals help raise offspring that are not their own. This behaviour is particularly well studied in birds, using both long-term and comparative studies that have provided insights into the evolution of reproductive altruism. In most cooperatively breeding species, helpers are offspring that remain with their parents beyond independency and help in the raising of younger siblings. However, many cooperatively breeding species are poorly studied, and in 152 species, this behaviour only has been observed infrequently (i...
2016: Zoological Letters
Victoria Shone, Silvan Oulion, Didier Casane, Patrick Laurenti, Anthony Graham
BACKGROUND: Pharyngeal segmentation is a defining feature of vertebrate embryos and is apparent as a series of bulges found on the lateral surface of the embryonic head, the pharyngeal arches. The ancestral condition for gnathostomes is to have seven pharyngeal segments: jaw, hyoid, and five posterior branchial arches. However, within the sarcopterygians, the pharyngeal region has undergone extensive remodelling that resulted in a reduction in the number of pharyngeal segments, such that amniotes have only five pharyngeal arches...
2016: Zoological Letters
Yoshimasa Hamada, Atsushi Tokuoka, Tetsuya Bando, Hideyo Ohuchi, Kenji Tomioka
INTRODUCTION: Insects show daily behavioral rhythms controlled by an endogenous oscillator, the circadian clock. The rhythm synchronizes to daily light-dark cycles (LD) and changes waveform in association with seasonal change in photoperiod. RESULTS: To explore the molecular basis of the photoperiod-dependent changes in circadian locomotor rhythm, we investigated the role of a chromatin modifier, Enhancer of zeste (Gb'E(z)), in the cricket, Gryllus bimaculatus. Under a 12 h:12 h LD (LD 12:12), Gb'E(z) was constitutively expressed in the optic lobe, the site of the biological clock; active phase (α) and rest phase (ρ) were approximately 12 h in duration, and α/ρ ratio was approximately 1...
2016: Zoological Letters
Bidur Dhungel, Yoshikazu Ohno, Rie Matayoshi, Mayo Iwasaki, Wataru Taira, Kiran Adhikari, Raj Gurung, Joji M Otaki
BACKGROUND: The border ocellus, or eyespot, is a conspicuous color pattern element in butterfly wings. For two decades, it has been hypothesized that transcription factors such as Distal-less (Dll) are responsible for eyespot pattern development in butterfly wings, based on their expression in the prospective eyespots. In particular, it has been suggested that Dll is a determinant for eyespot size. However, functional evidence for this hypothesis has remained incomplete, due to technical difficulties...
2016: Zoological Letters
Takeshi Takeuchi, Ryo Koyanagi, Fuki Gyoja, Miyuki Kanda, Kanako Hisata, Manabu Fujie, Hiroki Goto, Shinichi Yamasaki, Kiyohito Nagai, Yoshiaki Morino, Hiroshi Miyamoto, Kazuyoshi Endo, Hirotoshi Endo, Hiromichi Nagasawa, Shigeharu Kinoshita, Shuichi Asakawa, Shugo Watabe, Noriyuki Satoh, Takeshi Kawashima
INTRODUCTION: Bivalve molluscs have flourished in marine environments, and many species constitute important aquatic resources. Recently, whole genome sequences from two bivalves, the pearl oyster, Pinctada fucata, and the Pacific oyster, Crassostrea gigas, have been decoded, making it possible to compare genomic sequences among molluscs, and to explore general and lineage-specific genetic features and trends in bivalves. In order to improve the quality of sequence data for these purposes, we have updated the entire P...
2016: Zoological Letters
Takao Kaji, James D Reimer, Arseniy R Morov, Shigeru Kuratani, Kinya Yasui
INTRODUCTION: Deuterostomes (animals with 'secondary mouths') are generally accepted to develop the mouth independently of the blastopore. However, it remains largely unknown whether mouths are homologous among all deuterostome groups. Unlike other bilaterians, in amphioxus the mouth initially opens on the left lateral side. This peculiar morphology has not been fully explained in the evolutionary developmental context. We studied the developmental process of the amphioxus mouth to understand whether amphioxus acquired a new mouth, and if so, how it is related to or differs from mouths in other deuterostomes...
2016: Zoological Letters
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