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Calli R Freedman, Douglas S Fudge
Hagfishes are able to squeeze through small openings to gain entry to crevices, burrows, hagfish traps, and carcasses, but little is known about how they do this, or what the limits of this ability are. The purpose of this study was to describe this ability, and to investigate possible mechanisms by which it is accomplished. We investigated the hypothesis that the passive movement of blood within a hagfish's flaccid subcutaneous sinus allows it to squeeze through narrow apertures that it would not be able to if it were turgid...
January 13, 2017: Journal of Experimental Biology
Chris N Glover, Tamzin A Blewett, Chris M Wood
Among vertebrates, hagfish are the only known iono- and osmoconformers, and the only species thus far documented to absorb amino acids directly across the skin. In the current study, short-term (6h) manipulations of exposure salinities (75-125% seawater) were conducted to determine whether changes in osmotic demands influenced the uptake and tissue distribution of waterborne amino acids (alanine, glycine and phenylalanine), in the Pacific hagfish, Eptatretus stoutii. No changes in erythrocyte or muscle amino acid accumulation rates were noted, but the patterns of plasma amino acid accumulation were suggestive of regulation...
February 2017: Comparative Biochemistry and Physiology. Part A, Molecular & Integrative Physiology
Matthew J Endsin, Ola Michalec, Lori A Manzon, David A Lovejoy, Richard G Manzon
The corticotropin releasing hormone (CRH) system, which includes the CRH family of peptides, their receptors (CRHRs) and a binding protein (CRHBP), has been strongly conserved throughout vertebrate evolution. The identification of invertebrate homologues suggests this system evolved over 500 million years ago. However, the early vertebrate evolution of the CRH system is not understood. Current theory indicates that agnathans (hagfishes and lampreys) are monophyletic with a conservative evolution over the past 500million years and occupy a position at the root of vertebrate phylogeny...
January 1, 2017: General and Comparative Endocrinology
Akinori Suzuki, Hidero Komata, Shogo Iwashita, Shotaro Seto, Hironobu Ikeya, Mitsutoshi Tabata, Takashi Kitano
In vertebrates, there are four major genes in the RH (Rhesus) gene family, RH, RHAG, RHBG, and RHCG. These genes are thought to have been formed by the two rounds of whole-genome duplication (2R-WGD) in the common ancestor of all vertebrates. In our previous work, where we analyzed details of the gene duplications process of this gene family, three nucleotide sequences belonging to this family were identified in Far Eastern brook lamprey (Lethenteron reissneri), and the phylogenetic positions of the genes were determined...
October 13, 2016: Molecular Phylogenetics and Evolution
Damianos Chatzievangelou, Carolina Doya, Laurenz Thomsen, Autun Purser, Jacopo Aguzzi
Three benthic megafaunal species (i.e. sablefish Anoplopoma fimbria; pacific hagfish Eptatretus stoutii and a group of juvenile crabs) were tested for diel behavioral patterns at the methane hydrates site of Barkley Canyon (890 m depth), off Vancouver Island (BC, Canada). Fluctuations of animal counts in linear video-transects conducted with the Internet Operated Deep-Sea Crawler "Wally" in June, July and December of 2013, were used as proxy of population activity rhythms. Count time series and environmental parameters were analyzed under the hypothesis that the environmental conditioning of activity rhythms depends on the life habits of particular species (i...
2016: PloS One
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
Christopher M Wilson, Jinae N Roa, Georgina K Cox, Martin Tresguerres, Anthony P Farrell
While neural modulation of heart rate is well established among chordate animals, the Pacific hagfish (Eptatretus stoutii) lacks any cardiac innervation yet can increase its heart rate from the steady, depressed heart rate seen in prolonged anoxia to almost double its normal normoxic heart rate, an almost four-fold overall change during the 1-h recovery from anoxia. The present study sought mechanistic explanations for these regulatory changes in heart rate. We provide evidence for a bicarbonate-activated, soluble adenylyl cyclase (sAC)-dependent mechanism to control heart rate, a mechanism never previously implicated in chordate cardiac control...
August 10, 2016: Journal of Experimental Biology
Sarah E Gabbott, Philip C J Donoghue, Robert S Sansom, Jakob Vinther, Andrei Dolocan, Mark A Purnell
The success of vertebrates is linked to the evolution of a camera-style eye and sophisticated visual system. In the absence of useful data from fossils, scenarios for evolutionary assembly of the vertebrate eye have been based necessarily on evidence from development, molecular genetics and comparative anatomy in living vertebrates. Unfortunately, steps in the transition from a light-sensitive 'eye spot' in invertebrate chordates to an image-forming camera-style eye in jawed vertebrates are constrained only by hagfish and lampreys (cyclostomes), which are interpreted to reflect either an intermediate or degenerate condition...
August 17, 2016: Proceedings. Biological Sciences
Lukas Böni, Peter Fischer, Lukas Böcker, Simon Kuster, Patrick A Rühs
When hagfish (Myxinidae) are attacked by predators, they form a dilute, elastic, and cohesive defensive slime made of mucins and protein threads. In this study we propose a link between flow behavior and defense mechanism of hagfish slime. Oscillatory rheological measurements reveal that hagfish slime forms viscoelastic networks at low concentrations. Mucins alone did not contribute viscoelasticity, however in shear flow, viscosity was observed. The unidirectional flow, experienced by hagfish slime during suction feeding by predators, was mimicked with extensional rheology...
2016: Scientific Reports
Masafumi Amano, Noriko Amiya, Takehiko Yokoyama, Kengo Onikubo, Naoyuki Yamamoto, Akiyoshi Takahashi
The distribution of corticotropin-releasing hormone (CRH) in the brain and pituitary of the hagfish Eptatretus burgeri, representing the earliest branch of vertebrates, was examined by immunohistochemistry to better understand the neuroendocrine system of hagfish. CRH-immunoreactive (ir) cell bodies were detected in the preoptic nucleus, periventricular preoptic nucleus, infundibular nucleus of the hypothalamus, and in the nucleus "A" of Kusunoki et al. (1982) in the medulla oblongata. In the brain, CRH-ir fibers were detected in almost all areas except for the olfactory bulb and telencephalon...
September 15, 2016: General and Comparative Endocrinology
Alexander M Clifford, Alex M Zimmer, Chris M Wood, Greg G Goss
Hagfish skin has been reported as an important site for ammonia excretion and as the major site of systemic oxygen acquisition. However, debate remains whether cutaneous O2 uptake is the dominant route of uptake; all evidence supporting this hypothesis has been derived using indirect measurements. Here we use separating chambers and direct measurements of oxygen consumption and ammonia excretion to quantify cutaneous and branchial exchanges in Pacific hagfish (Eptatretus stoutii) at rest and following exhaustive exercise...
July 8, 2016: Journal of Experimental Biology
Jeanette L Lim, George V Lauder
Physical models enable researchers to systematically examine complex and dynamic mechanisms of underwater locomotion in ways that would be challenging with freely swimming animals. Previous research on undulatory locomotion, for example, has used rectangular flexible panels that are effectively two-dimensional as proxies for the propulsive surfaces of swimming fishes, but these bear little resemblance to the bodies of elongate eel-like swimming animals. In this paper we use a polyurethane rod (round cross-section) and bar (square cross-section) to represent the body of a swimming Pacific hagfish (Eptatretus stoutii)...
2016: Bioinspiration & Biomimetics
Andrew J Clark, Callie H Crawford, Brooke D King, Andrew M Demas, Theodore A Uyeno
Hagfishes (Myxinidae) often integrate whole-body knotting movements with jawless biting motions when reducing large marine carcasses to ingestible items. Adaptations for these behaviors include complex arrangements of axial muscles and flexible, elongate bodies without vertebrae. Between the axial muscles and the hagfish skin is a large, blood-filled subcutaneous sinus devoid of the intricate, myoseptal tendon networks characteristic of the taut skins of other fishes. We propose that the loose-fitting skin of the hagfish facilitates the formation and manipulation of body knots, even if it is of little functional significance to steady swimming...
June 2016: Biological Bulletin
Amber Dance
No abstract text is available yet for this article.
June 28, 2016: Proceedings of the National Academy of Sciences of the United States of America
Irena Zingerman-Koladko, Maayan Khayat, Jan Harapin, Oded Shoseyov, Yosef Gruenbaum, Ahmad Salman, Ohad Medalia, Kfir Ben-Harush
Intermediate filament (IF) proteins are known mainly by their propensity to form viscoelastic filamentous networks within cells. In addition, IF-proteins are essential parts of various biological materials, such as horn and hagfish slime threads, which exhibit a range of mechanical properties from hard to elastic. These properties and their self-assembly nature made IF-proteins attractive building blocks for biomimetic and biological materials in diverse applications. Here we show that a type V IF-protein, the Caenorhabditis elegans nuclear lamin (Ce-lamin), is a promising building block for protein-based fibers...
October 2016: Journal of the Mechanical Behavior of Biomedical Materials
Shigeru Kuratani, Yasuhiro Oisi, Kinya G Ota
Our knowledge of vertebrate cranium evolution has relied largely on the study of gnathostomes. Recent evolutionary and developmental studies of cyclostomes have shed new light on the history of the vertebrate skull. The recent ability to obtain embryos of the hagfish, Eptatretus burgeri, has enabled new studies which have suggested an embryonic morphological pattern (the "cyclostome pattern") of craniofacial development. This pattern is shared by cyclostomes, but not by modern jawed vertebrates. Because this pattern of embryonic head development is thought to be present in some stem gnathostomes (ostracoderms), it is possible that the cyclostome pattern represents the vertebrate ancestral pattern...
June 2016: Zoological Science
Douglas S Fudge, Sarah Schorno
Fibers are ubiquitous in biology, and include tensile materials produced by specialized glands (such as silks), extracellular fibrils that reinforce exoskeletons and connective tissues (such as chitin and collagen), as well as intracellular filaments that make up the metazoan cytoskeleton (such as F-actin, microtubules, and intermediate filaments). Hagfish gland thread cells are unique in that they produce a high aspect ratio fiber from cytoskeletal building blocks within the confines of their cytoplasm. These threads are elaborately coiled into structures that readily unravel when they are ejected into seawater from the slime glands...
2016: Cells
Harry J Grier, Mari Carmen Uribe, Fabiana L Lo Nostro, Steven D Mims, Lynne R Parenti
The germinal epithelium, i.e., the site of germ cell production in males and females, has maintained a constant form and function throughout 500 million years of vertebrate evolution. The distinguishing characteristic of germinal epithelia among all vertebrates, males, and females, is the presence of germ cells among somatic epithelial cells. The somatic epithelial cells, Sertoli cells in males or follicle (granulosa) cells in females, encompass and isolate germ cells. Morphology of all vertebrate germinal epithelia conforms to the standard definition of an epithelium: epithelial cells are interconnected, border a body surface or lumen, are avascular and are supported by a basement membrane...
August 2016: Journal of Morphology
Chris N Glover, Tamzin A Blewett, Chris M Wood
Hagfish are unique among aquatic "vertebrates" in their ability to absorb amino acids directly from the water via skin and gill epithelia, but it is unknown whether this phenomenon extends beyond a few studied substrates; what effect fed state has on absorption; and what functional role this may play in hagfish nutrition. Using in vivo and in vitro transport assays, uptake and tissue distribution of the waterborne amino acids L-alanine, L-lysine, and L-phenylalanine were examined as a function of fed state...
October 2016: Journal of Comparative Physiology. B, Biochemical, Systemic, and Environmental Physiology
Trevor D Lamb, Hardip Patel, Aaron Chuah, Riccardo C Natoli, Wayne I L Davies, Nathan S Hart, Shaun P Collin, David M Hunt
We applied high-throughput sequencing to eye tissue from several species of basal vertebrates (a hagfish, two species of lamprey, and five species of gnathostome fish), and we analyzed the mRNA sequences for the proteins underlying activation of the phototransduction cascade. The molecular phylogenies that we constructed from these sequences are consistent with the 2R WGD model of two rounds of whole genome duplication. Our analysis suggests that agnathans retain an additional representative (that has been lost in gnathostomes) in each of the gene families we studied; the evidence is strong for the G-protein α subunit (GNAT) and the cGMP phosphodiesterase (PDE6), and indicative for the cyclic nucleotide-gated channels (CNGA and CNGB)...
August 2016: Molecular Biology and Evolution
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