A germline restricted, highly repetitive DNA sequence in Paramyxineatami : an interspecifically conserved, but somatically eliminated, element

In some species of hagfish, the phenomenon of chromosome elimination occurs during embryogenesis. However, only two repetitive DNA families are known to be represented in chromosomes that are eliminated from somatic cells of the Japanese hagfish Eptatretus okinoseanus. Using molecular analyses, another germ line-restricted, highly repetitive DNA family has been detected in another Japanese hagfish, Paramyxine atami. The repeat unit of this family, which is 83 bp long, has been designated “EEPa1”, for Eliminated Element of P. atami 1. DNA filter hybridization using EEPa1 as a probe revealed that this family is shared among several species and is conserved in the germline DNA. Although eliminated, repetitive DNA that is shared interspecifically has not been reported in hagfish species, cases of chromatin diminution and chromosome elimination processes have been described previously in other organisms.The patterns and intensities of hybridization signals suggest that members of the repetitive DNA family defined by EEPa1 have undergone concerted molecular evolution. Received: 7 January 1997 / Accepted: 13 May 1997     

A new species of hagfish (Myxinidae: Eptatretus) from Papua New Guinea

A new species of seven‐gilled hagfish Eptatretus astrolabium (Myxinidae) is described from a 400 mm total length female trapped 1 km east from Planet Rock, Astrolabe Bay, Papua New Guinea, at c. 500 m depth. This is the first hagfish species reported from the waters around New Guinea. It can be distinguished from other hagfishes by a combination of characters including seven pairs of gill apertures, three‐cusp multicusps on the anterior and posterior rows of cusps, 10 posterior unicusps, 52 total cusps, 18–19 prebranchial pores, five branchial pores, 48–49 trunk pores, 83–84 total pores and no nasal‐sinus papillae.     

Reproductive biology and ecology of Pacific hagfish (Eptatretus stoutii) and black hagfish (Eptatretus deani)

The reproductive biology of Pacific hagfish Eptatretus stoutii (Lockington, 1878) and black hagfish Eptatretus deani (Evermann & Goldsborough, 1907) was assessed using current and historical data. Our results found that the reproductive characteristics of both hagfish species reflect those of K-selected species, which tend to live long and exhibit slow growth rates, low fecundity (approximately 20 eggs per female) and late maturity. Additionally, females of both species commence maturation prior to males. This study provides a population profile for both species of hagfish, but further assessments are needed to effectively manage a sustainable hagfish fishery.     

A germline restricted, highly repetitive DNA sequence in Paramyxineatami: an interspecifically conserved, but somatically eliminated, element

In some species of hagfish, the phenomenon of chromosome elimination occurs during embryogenesis. However, only two repetitive DNA families are known to be represented in chromosomes that are eliminated from somatic cells of the Japanese hagfish Eptatretus okinoseanus. Using molecular analyses, another germ line-restricted, highly repetitive DNA family has been detected in another Japanese hagfish, Paramyxine atami. The repeat unit of this family, which is 83?bp long, has been designated “EEPa1”, for Eliminated Element of P. atami 1. DNA filter hybridization using EEPa1 as a probe revealed that this family is shared among several species and is conserved in the germline DNA. Although eliminated, repetitive DNA that is shared interspecifically has not been reported in hagfish species, cases of chromatin diminution and chromosome elimination processes have been described previously in other organisms.The patterns and intensities of hybridization signals suggest that members of the repetitive DNA family defined by EEPa1 have undergone concerted molecular evolution.     

Structure of portal vein heart wall in the brown hagfish (Paramyxine atami)

The portal vein heart (PVH) wall of the brown hagfish (Paramyxine atami) was observed by light and transmission electron microscopy. Cardiac musculature is well developed in the PVH wall. The myocytes possess arranged myofibrils in the cytoplasm. We suggest that the PVH may act as a pump in blood circulation from the intestines to the liver, as it does in other myxinoid species. Ultrastructural and immunohistochemical findings of the brown hagfish PVH myocytes also indicate that the PVH has an active contraction and atrial natriuretic polypeptide endocrine function. J Morphol 231:225–230, 1997. © 1997 Wiley-Liss, Inc.     

Variability in the Presence of Elastic Fibre-like Structures in the Ventral Aorta of Agnathans (Hagfishes and Lampreys)

This paper investigates whether elastic fibre-like structures are present in the ventral aorta of hagfishes and lampreys. Fibres, which are morphologically similar to the elastic fibres of gnathostomatous (jawed) vertebrates, are shown to be present in the ventral aorta of the hagfish Paramyxine atami, and also, but to a lesser extent, the dorsal aorta of this species and the ventral aorta of another hagfish, Eptatretus stouti.The ‘elastic’ tissue formed irregular sheet-like aggregates, comprising well-defined amorphous material surrounded by tubular microfibrils, whose diameters ranged from 10 to 15 nm. While this tissue was most abundant in the same region of the aortae as that occupied by the elastica interna in the blood vessels of gnathostomes, it was also found deeper in the wall of these blood vessels. Although tubular microfibrils were found in the ventral aorta of the hagfish Myxine glutinosaand the lamprey Geotria australis, these were never associated with well–defined, amorphous material. This parallels the results of previous studies on Myxine glutinosaand another species of lamprey, Petromyzon marinus.Thus, the elastic fibre–like tissues found in the ventral aortae of P. atamiand E. stoutiprovide the first examples of such structures in this region in agnathan vertebrates.     

Myxine formosana, a new species of hagfish (Myxiniformes: Myxinidae) from the southwestern waters of Taiwan

Myxine formosana, a new hagfish species, is described on the basis of the specimens from the Pacific Ocean southwest of Taiwan at depths 588–1500 m. It is five-gilled and white-headed with a three-cusp multicusp on the anterior set of cusps and a two-cusp multicusp on the posterior set. Myxine formosana, M. circifrons, M. mccoskeri, and M. robinsi are superficially rather similar, but M. formosana has low to vestigal caudal finfolds. It is the first record of the genus Myxine from Taiwan. Received: October 25, 2000 / Revised: March 17, 2001 / Accepted: April 21, 2001     

Current knowledge of hagfish reproduction: implications for fisheries management

This review briefly summarizes the latest findings on reproductiveendocrinology of Atlantic hagfish (Myxine glutinosa) and implicationsfor fisheries management. In response to a major decline orcollapse of the fisheries (groundfish and anadromous species)industry in the Northeast, species that were once consideredalternative or underutilized have and are being identified thatmay be suitable for commercial harvest, one such example isthe hagfish. Hagfish in recent years have been sought afteras valuable fish not only for their flesh, but also their skin.Currently, there are no regulations governing the harvestingof hagfish along the East Coast. There has been little to noinformation of the life history of hagfish including growthrate, age determination, reproductive biology, life span, andlarval size at hatching. Thus, the level at which a sustainablefisheries for this species can be maintained is unknown. Insome parts of the world, hagfish stocks are being depleted dueto overfishing. In order for fisheries management to manageits hagfish stocks and develop a sustainable commercial hagfishfishery, critical information is needed to assist in determiningthe optimal use of this valuable resource. Key elements of the reproductive system have not been elucidatedin hagfish. However, there is new evidence from recent reproductivestudies that Atlantic hagfish may have a seasonal reproductivecycle. These data include seasonal changes in gonadotropin-releasinghormone (GnRH), gonadal steroids, estradiol and progesterone,corresponding to gonadal reproductive stages along with theputative identity of a functional corpus luteum. This newlyacquired data may provide important information to fisheriesmanagers of the East Coast.     

Gonadotropin-like and adrenocorticotropin-like cells in the pituitary gland of hagfish, Paramyxine atami; immunohistochemistry in combination with lectin histochemistry

The pituitary system of the hagfish remains an enigma. The present study has aimed to detect possible adenohypophysial hormones in the pituitary gland of the brown hagfish, Paramyxine atami, by means of immunohistochemistry in combination with lectin histochemistry. Rabbit antisera raised against ovine luteinizing hormone (LH)β, proopiomelanocortin (POMC)-related peptides, and the growth hormone/prolactin family of tetrapod and fish species were used, and 25 kinds of lectins were tested. Three different types of adenohypophysial cells were revealed in the pituitary of brown hagfish. The first was stained with both anti-ovine LHβ and several D-mannose-binding lectins, such as Lens culinaris agglutinin and Pisum sativum agglutinin. This cell type predominated in the adenohypophysis in adults with developing gonads and thus appeared to be involved in the regulation of gonadal functions. The second was negative for anti-ovine LHβ but was stained with several N-acetylglucosamine-binding lectins, such as wheat germ agglutinin and Lycopersicon esculentum lectin. This cell type exhibited a weak positive reaction with anti-lamprey adrenocorticotropin (ACTH) and thus appeared to be related to POMC-like cells. The second cell type was found in the adenohypophysis regardless of the developmental state of the gonads. The third cell type was negative for both antisera and lectins. Since this cell type was numerous in juveniles and adults without developing gonads, most cells of this type were probably undifferentiated. These findings suggest that GTH and ACTH are major adenohypophysial hormones in the hagfish. This work was supported by Grants-in-Aid from the Ministry of Education, Science and Culture (to M.N.).     

The Complete Mitochondrial Genome of the Hagfish Myxine glutinosa: Unique Features of the Control Region

The complete sequence of the mitochondrial DNA of the hagfish Myxine glutinosa has been determined. The hagfish mtDNA (18,909 bp) is the longest vertebrate mtDNA determined so far. The gene arrangement conforms to the consensus vertebrate type and differs from that of lampreys. The exceptionally long (3628-bp) control region of the hagfish contains the typical conserved elements found in other vertebrate mtDNAs but is characterized by a large number of putative hairpins, which can potentially fold into a highly compact secondary structure that appears to be unique to hagfish. The comparison of the mtDNAs of two M. glutinosa specimens, excluding the control region, shows a 0.6% divergence at the nucleotide level as a sample of intraspecies polymorphism. Received: 21 August 2000 / Accepted: 2 March 2001     

Myomuscular junctions in the gill-sac muscle of the Atlantic hagfish,Myxine glutinosa: analogy with myotendinous junctions

Summary Myomuscular junctions between muscle fibers in the gill sacs of the Atlantic hagfish, Myxine glutinosa, were examined by electron microscopy. According to the presence of sarcolemmal differentiations typical of myotendinous junctions, the myomuscular junctions can be described as a symmetric myotendinous junction     

Highly repetitive DNA sequences that are restricted to the germ line in the hagfish Eptatretus cirrhatus: a mosaic of eliminated elements

The New Zealand hagfish, Eptatretus cirrhatus, is known to eliminate parts of its chromosomes during embryogenesis from presumptive somatic cells. Electrophoresis of germ line and somatic DNAs of this species, after treatment with the restriction endonucleases DraI and EcoRI, revealed three fragments of DNA that were restricted to the germ line. DNA filter hybridization experiments demonstrated that these fragments were present almost exclusively in the germ line DNA of E. cirrhatus and that they were highly and tandemly repeated. Thus, these DNA fragments appeared to be eliminated during embryogenesis. Moreover, one fragment (a DraI fragment) cross-hybridized with the germ line DNA from other species of hagfish, namely, Eptatretus okinoseanus and Paramyxine atami. Molecular cloning and sequence analysis revealed that the DraI fragment was composed mainly of closely related sequences of 85 bp in length and that this sequence was about 75% homologous to the sequence of EEEo2 (eliminated element of E. okinoseanus 2) which is a germ line-restricted and highly repetitive sequence that was isolated previously from E. okinoseanus. The other two fragments were composed of three families of closely related sequences that were 172 bp long (designated EEEc1), 61 bp long (EEEc2) and 54 bp long (EEEc3). Fluorescence in situ hybridization experiments revealed that each eliminated element was distributed on several chromosomes that are limited to germ cells. EEEo2 was dispersed on 12 C-band-positive chromosomes. EEEc1 and EEEc3 were dispersed on all C-band-positive and several C-band-negative chromosomes. By contrast, EEEc2 was located to terminal regions of several C-band-negative chromosomes. These results suggest that the eliminated chromosomes in hagfish are mosaics of highly repeated, germ line-restricted families of DNA sequences. Received: ██; in revised form: 25 October 1997 / Accepted: ██     

The chromosomes of some lower chordates

The chromosomes of three species of lower chordates were examined using a squash technique on small pieces of testis. Ciona intestinalis, a tunicate of the order Enterogona, has fourteen pairs of minute chromosomes. Styela plicata, a tunicate of the order Pleurogona, has sixteen pairs of chromosomes whose total size is approximately twice that of the Ciona chromosomes and about 10% of that of a typical mammalian complement. The hagfish, Eptatretus stoutii, of the suborder Myxinoidea, order Cyclostomata, has twenty-four pairs of chromosomes and what appear to be one to four small supernumeraries in some animals. The hagfish chromosomes are large, approaching the size of a typical mammalian complement. These size relationships agree in general with a concept of a small ancestral vertebrate genome which evolved into the larger present day genomes through a series of duplications of genetic material.This work was supported in part by Grant No. 247-701 from the San Diego State College Foundation.     

Some observations on cardiac automatism in certain animals

Certain aspects of the acetylcholine hypothesis of cardiac automaticity have been tested in vitro with spontaneously beating cardiac tissue from rabbits, rats, dams, and hagfish. The beat of atria from rabbits and rats may be depressed or excited by acetylcholine, depending upon the state of the tissue. Proguanil and cocaine inhibition of the beat in the rat may be antagonized by acetylcholine so that reversal of the depression occurs. The action of acetylcholine on the hearts of clams was found to be strictly inhibitory. Proguanil and cocaine, in contrast to their action on mammalian atria, exert a stimulatory effect on the heart of the molluscs studied. In fact, cocaine stimulated these hearts when they were inhibited by acetylcholine. Studies on the non-innervated hagfish heart revealed that this tissue is completely insensitive to the action of acetylcholine. Extracts prepared from beating hearts of this species will accelerate hypodynamic hearts of the hagfish as well as of the mussel. An extract of the neurogenic lobster heart was without effect on the hagfish heart. Proguanil was likewise ineffective in concentrations which produced inhibition and excitation in rat and clam hearts respectively. It was concluded that acetylcholine does not play a role in the myogenic automatism of all species, and that another mechanism is responsible is suggested on the basis of results obtained in the hagfish hearts.     

FMRF -amide-like immunoreactivity in brain and pituitary of the hagfish Eptatretus burgeri (Cyclostomata)

Summary Paraffin sections of brain and pituitary of the hagfish Eptatretus burgeri were immunostained with an antiserum to FMRF-amide. Immunoreactivity was visible in a large number of neurons in the posterior part of the ventromedial hypothalamus and in long neuronal processes extending cranially from the hypothalamus to the olfactory system and caudally to the medulla oblongata. FMRF-amide-like immunoreactivity was also found in cells of the adenohypophysis. These observations suggest that the hagfish possesses a brain FMRF-amide-like transmitter system and pituitary cells containing FMRF-amide-like material.Antisera to ACTH, -MSH and pancreatic polypeptide gave no immunoreaction in hagfish brain or pituitary. D aspartic acid - F phenylalanine - L leucine - M methionine - R arginine; - W tryptophan - Y tyrosine     

Angiotensin I-converting enzyme-like activity in tissues from the Atlantic hagfish (Myxine glutinosa) and detection of immunoreactive plasma angiotensins

Using a highly sensitive fluorimetric assay, significant levels of angiotensin I -converting enzyme-like activity (ACELA) were detected in a range of tissues (branchial heart, gill, kidney with associated vasculature and archinephric duct, liver, whole brain and gut) from the Atlantic hagfish (Myxine glutinosa). The highest ACELA occurred in heart and gill (1.8 and 1.5 nmol His–Leu min⁻¹ mg protein⁻¹, respectively). The mammalian angiotensin I-converting enzyme (ACE) inhibitor, captopril, at 10⁻⁵ M was a potent inhibitor of the ACELA found in all hagfish tissues. Radioimmunoassay showed that immunoreactive angiotensins (251.8±11.8 pM) were detectable in hagfish plasma. The validity of the assay for measurement of hagfish angiotensins was indicated by the parallelism of the angiotensin II standard curve against serially diluted hagfish plasma. Measurement of immunoreactive plasma angiotensins and detection of significant levels of ACELA in a wide range of tissues gives indirect evidence for the presence of a renin–angiotensin system in hagfishes, the earliest evolved group of craniates.     

Seasonal concentrations of reproductive steroids in the gonads of the Atlantic hagfish, Myxine glutinosa

Changes in gonadal morphology, gonadal estradiol, and progesterone were examined in Atlantic hagfish, Myxine glutinosa, during a period of 17 months, beginning in April, 2001. Atlantic hagfish were captured from the ocean on a monthly basis. A total of 60 hagfish were divided into three different size classes of twenty hagfish each (small 20-35 cm, medium 35-45 cm, large 45-55+cm) and transported to the University of New Hampshire for sampling. Overall, in the medium and large size hagfish, estradiol and progesterone had significantly elevated peaks in January, 2001. There were significant increases in estradiol concentrations in January, with relatively low fluctuations in levels for the rest of the sampling period. Progesterone concentrations increased significantly in January, 2002, in medium and large hagfish, and remained elevated until June and April, 2002, for the two size classes respectively. The majority of hagfish sampled were females or hermaphrodites; few true males were identified in any of the samples. The number of females with large eggs increased following the estradiol peak in January and hermaphrodites with mature sperm were identified in the July, 2002, sample. These data represent the first evidence for a seasonal reproductive cycle in M. glutinosa and only the second seasonal reproductive cycle identified in any hagfish species.     

The partial sequence of the first 30 residues from the amino-terminus of hemoglobin B in the hagfish,Eptatretus stoutii: Homology with lamprey hemoglobin

Summary The partial sequence of the first 30 residues from the amino-terminus of hemoglobin B in the hagfish,Eptatretus stoutii, has been determined. Considerable homology was found between this sequence and the corresponding sequence of lamprey hemoglobin. Both hagfish and lamprey hemoglobins have an additional segment of 9 residues at the amino-terminus as compared with mammalian hemoglobins.This work was initiated at the University of Texas at Austin, and continued in Dr. Charles Yanofskey's laboratory at Stanford University.     

Variability in behaviour of four fish species attracted to baited underwater cameras in the North Sea

Baited underwater camera (BUC) systems to estimate demersal fish abundance are becoming increasingly considered as an alternative to traditional survey methods, particularly in environments that contain sensitive habitats or protected species. Based on 27 replicate deployments of BUCs at 100 m depth in the northern North Sea, in rank order of abundance, hagfish (Myxine glutinosa), flatfish mainly dabs (Limanda limanda), whiting (Merlangius merlangus) and haddock (Melanogramus aeglefinus) were observed consistently at baits. Higher maximum numbers (N _max) occurred during daytime in all species with the most significant effect in flatfish, 18 in daytime and 5 at night-time. Bottom current had no significant effect on numbers of whiting, flatfish or haddock. The N _max of hagfish was strongly related to current speed in a non-linear way with an increase in numbers up to 10 cm s⁻¹ and then decrease in N _max at higher water speeds. Understanding and accounting for such species-specific influences is important in the design of long term monitoring surveys using baited cameras.     

Volume and pH regulation in agnathan erythrocytes: comparisons between the hagfish,Myxine glutinosa,and the lampreys,Petromyzon marinus and Lampetra fluviatilis

The responses of hagfish (Myxine glutinosa) and lamprey (Lampetra fluviatilis and Petromyzon marinus) erythrocytes to osmotic swelling in hypoosmotic medium and to acid-base disturbances induced by ammonium chloride prepulse were studied. The erythrocytes of hagfish regulated neither cell volume after osmotic swelling nor intracellular pH after acidification. In contrast, the erythrocytes of lamprey lost potassium and chloride after osmotic swelling, whereby their volume recovered. Furthermore, the red cell pH of lamprey recovered from experimental acidification in a nominally bicarbonate-free medium in the presence of sodium, confirming that the pathway involved is sodium/proton exchange.Abbreviation DMO 5,5-dimethyloxazolidine-2,4-dione