Lungfish

Cross references:    Lungfish Dominance Hierarchies  

Sarcopterygii (Wiki) 
"The living sarcopterygians are the coelacanths, lungfishes and all tetrapods."  "The fin-limbs of sarcopterygians such as the coelacanths show a strong similarity to the expected ancestral form of tetrapod limbs."   


Lungfish (Wiki) 
http://en.wikipedia.org/wiki/Lungfish 
"Most lungfish have two lungs. The Australian lungfish has one. The lung(s) connect to the pharynx. The lungs of lungfish are homologous to the lungs of tetrapods.

Note:  The next three links, below, which are designated "
(Wiki)" are from the link above. 

Introduction to the Dipnoi 
(Wiki)
http://www.ucmp.berkeley.edu/vertebrates/sarco/dipnoi.html  
"Lungfish are believed to be the closest living relatives of the tetrapods, and share a number of important characteristics with them. Among these characters are tooth enamel, separation of
pulmonary blood flow from body blood flow, arrangement of the skull bones, and the presence of four similarly sized limbs with the same position and structure as the four tetrapod legs. However, there is still debate about the relationships among the Sarcopterygii. "

Ann Kemps Lungfish Site
(Wiki)
http://www.annekempslungfish.com/   
"
Some scientists get excited about lungfish, because they think the lungfish is the closest "relative" of the land animals, including humans.
  In fact, it has been suggested that amphibians, the first land animals, evolved their limbs from the muscular fins of lungfish."

Lungfish Info
(Wiki)
http://www.lungfish.info/    
"The two families of lungfishes are Lepidosirenidae (South American lungfish and African lungfish) and Ceratodidae (Australian lungfish). All species have long snakelike bodies. All species of lungfishes grows large and the African lungfish can become over 6 feet / 2 m long. "  "The species in the Lepidosirenidae family builds a nest for their eggs. The nest is protected by the male until the fry have hatched.


The Biology and Evolution of Lungfishes (Biosis) 
This is the Table of Contents to a 373 page supplement of the Journal of Morphology.  There are 19 papers, and each has an Abstract which is available online. 

The natural history of African lungfishes 
From above.  I got the PDF through the library. 
    See:  
Lungfish Dominance Hierarchies   




The Natural History of the Australian Lungfish (Goog) 
Full length PDF available online for free. 
This is not the same as the book reference, above. 
    See:   Lungfish Dominance Hierarchies       



Spawning Behaviour in the Queensland Lungfish, Neoceratodus forsteri (Trove)   
Full length PDF available online for free. 
    See:   Lungfish Dominance Hierarchies        



The Biology of Lungfishes (Goog) 
This is the Table of Contents of a 536 page book which I was able to obtain from the library.  There are 20 chapters, and each chapter has an Abstract which is available online.  Unfortunately, I couldn't figure out how to either copy-and-paste from the Abstracts or access the PDFs through the library, so I'll have to transcribe from the hard copy of the book.    
The chapters I'm currently interested in are (using the chapter numbers from the book): 
    Chapter 3. The Natural History of the Australian Lungfish Neoceratodus Forsteri (Krefft, 1870) - Peter K. Kind 

Abstract - Hi-Res PDF (817 KB) - PDF w/links (744 KB) 
    Chapter 4. The General Natural History of the African Lungfishes -
Chrisestom M. Mlewa, John M. Green, Robert L. Dunbrack 

Abstract - Hi-Res PDF (325 KB) - PDF w/links (343 KB) 
    See:  
  Lungfish Dominance Hierarchies     
    Chapter 5. Biology of the South American Lungfish, Lepidosiren paradoxa - Vera Maria Fonseca de Almeida-Val, Sérgio Ricardo Nozawa, Nívia Pires Lopes, Paulo Henrique Rocha Aride, Lenise Socorro Mesquita-Saad, Maria de Nazaré Paula da Silva, Rubens Tomio Honda, Mônica S. Ferreira-Nozawa, Adalberto Luis Val 

Abstract - Hi-Res PDF (288 KB) - PDF w/links (306 KB) 
    Chapter 12. Lungfish Metabolism - James S. Ballantyne, Natasha T. Frick
 
Abstract - Hi-Res PDF (289 KB) - PDF w/links (301 KB) 
    Chapter 15. The Lungfish Endocrine System 
Abstract - Hi-Res PDF (410 KB) - PDF w/links (367 KB) 
    Chapter 16. The Central Nervous System of Lungfishes - R. Glenn Northcutt 
Abstract - Hi-Res PDF (1253 KB) - PDF w/links (1275 KB) 











An Immunohistochemical Approach to Lungfish Telencephalic Organization (Goog) 
Only abstract available online.   I got the PDF from the library. 
     "Our analysis highlights the common traits shared by lungfishes and tetrapods. These include four pallial regions, distinct striatal and pallidal components of the basal ganglia, specific regionalization of the septum, and the presence of three amygdaloid regions. In general, the use of immunohistochemistry in the study of the telencephalon of lungfishes reveals that this structure is notably more complex than previously thought and that it possesses all major subregions recognized in amphibians and amniotes.


An Immunohistochemical Study of the Telencephalon of the African Lungfish, Protopterus annectens
(Goog) 
Full length PDF available online for free. 


Dorsomedial telencephalon of lungfishes: A pallial or subpallial structure? criteria based on histology, connectivity, and histochemistry  (Goog) 
Only abstract available online.  I got the PDF through the library. 


Melanin-Concentrating Hormone System in the Brain of the Lungfish (Goog) 
Only abstract available online.  I got the PDF through the library. 


Neuropeptide Tyrosine in the Brain of the African Lungfish (Goog) 
Only abstract available online.  I got the PDF through the library. 


Reconciling the role of central serotonin neurones in human and animal behavior. Behav. Brain Sci. 9: 319–364, 1986. 
http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=6759740   
Only abstract available online.  I got the 46 page PDF through the library.
from the abstract    
    "
Decreases in serotonin transmission seem to be associated with the increased performance of behaviors that are usually suppressed, though not necessarily because of the alleviation of anxiety, which might contribute to the suppression.
"
my impression of the PDF from memory
    This is a very long review of more-or-less everything that was known about serotonin 25 years ago.   It hypothesizes that in the strong correlation between elevated circulating cortisol and elevated
Serotonin activity, it is the elevated Serotonin that is the cause and the elevated cortisol that is the effect.  However, it does not offer an explanation of how elevated Serotonin causes elevated cortisol.   
    An alternative hypothesis is that the elevated cortisol is the cause and the elevated serotonin is the effect.  Cortisol suppresses the sensitivity of lutenizing hormone receptors on the testes, thereby reducing the production of testosterone.  Since testosterone inhibits serotonergic receptors, the elevated circulating cortisol causes elevated serotonin activity by reducing the inhibitory effect of testosterone.   

   
    Full disclosure:  their position is supported by a reference that claims that "Treatment with 8-hydroxy-2(di-n- propylamino)tetralin, a specific 5-HT1A receptor agonist, elevates plasma cortisol concentrations in catheterized rainbow trout in a dosedependent manner (34)."   
    NOTE:  The 'full disclosure', above, doesn't seem to be from the paper.  The paper doesn't use reference numbers like '(34). 



Air-breathing adaptation in a marine Devonian lungfish (Goog) 
Full length HTML and PDF available online for free.  


Queensland lungfish (Wiki)   
The Wiki link, below, was from this page. 


Australian Lungfish (Wiki) 
Full length article available online for free. 
    "
Five spawning behaviours have been observed:
   
         5.  Should a third lungfish appraoach during the spawning a fifth behaviour has been observed - the interloper is driven off aggressively.


Neoceratodus forsteri - Australian Lungfish, Queensland Lungfish (Goog)
Long, very informative Australian government document available online for free.   
My comment:   
Searching the PDF yielded nothing about 'dominance hierarchies'.  


LUNGFISH-NEURAL-CHARACTERS-AND-THEIR-BEARING-ON-SARCOPTERYGIAN-PHYLOGENY (Goog) 
Only abstract (or perhaps just a very short article) available online.   The library was not able to provide access to anything longer with this title. 
My comment:   
Searching the HTML yielded nothing about 'dominance hierarchies'.  


Immunohistochemical localization of 3 beta-hydroxysteroid dehydrogenase and 5 alpha-reductase ... lungfish (Goog) 
Only abstract available online. 
I didn't understand it at all.     


Molecular evidence on the origin of tetrapods and the relationships of the coelacanth (Goog) 
Full length PDF available online for free.   
I wasn't able to copy-and-paste from the first download of this document, but the second download copied OK. 
    "Immunocytochemical techniques allowed mapping of the distribution of substance P, leu-enkephalin, serotonin, tyrosine hydrolase and pancreatic polypeptide-immunoreactive neurons, and seemed to suggest that the conditions in the brain of the African lungfish, Protoptems annectens, are similar to those in land vertebrates." 
My comments:   
`.  The reference for the above quote was: 
"Reiner,A . and Northcutt, G. (1987) J. Camp. Neural. 256,463-481"     
which I may already have. 
2.  Searching the PDF yielded nothing about 'dominance hierarchies'.    


Evolutionary relationships of the coelacanth, lungfishes, and tetrapods based on the 28S ribosomal RNA gene (Goog) 
Full length HTML and PDF available online for free. 


2011
Connections of the medial telencephalic wall in the spotted African Lungfish.   
http://www.ncbi.nlm.nih.gov/pubmed/21212641   
    "
The telencephalic organization in lungfishes thus appears remarkably similar to that in amphibians and reflects a pattern that almost certainly existed in the last common ancestor of lungfishes and tetrapods." 
   
Free full text   
   


NOTE: 

     Australian Research Online (ARO), below, and the seven references from it, have been moved to a new server and format called "Trove" as of the third week in February, 2011.  As a consequence, many of the formerly active links are no longer active.  Instead of spending a lot of time now reformatting the old, obsolete references, I'm going to leave them as they are, for now, and perhaps come back to them later.  The introduction to Trove implies that it contains more information than the old ARO, so it might also be worth my while to repeat the search in Trove.   



Australian Research Online (Goog) 
Australian Research Online 
Major index.  Come back to this. 

From the above Australian Research Online

In vitro biosynthesis of androgens in the Australian lungfish, Neoceratodus forsteri

Author/Creator: Joss, JMP, Edwards, A, Kime, DE
Resource type: journal article
Date: 1996
Subject: Comparative Physiology (270604), Animal Physiology - Systems (270603), Zoology not elsewhere classified (270599), Animal Systematics, Taxonomy and Phylogeny (270501)
Record contributed by: University of Tasmania

Full Record and related resources:
http://eprints.utas.edu.au/620/
http://eprints.utas.edu.au/620/1/Joss_et_al_1996.pdf
http://dx.doi.org/10.1006/gcen.1996.0028
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http://eprints.utas.edu.au/620/
http://eprints.utas.edu.au/620/1/Joss_et_al_1996.pdf
http://dx.doi.org/10.1006/gcen.1996.0028

Description
The serum concentration of testosterone was estimated from a population of wild lungfish over 6–7 years of sampling. Male lungfish were found to have high circulating levels of testosterone (50 ng/ml) which varied seasonally and could be correlated with spermatogenesis as judged by testis histology. Incubation of testis tissue slices with [3H]progesterone, [3H]17-hydroxyprogesterone, or [3H]testosterone confirmed that testosterone is the major androgen inNeoceratodus.Not even trace amounts of 11-keto- or 11β-hydroxytestosterone or 5α-dihydrotestosterone could be identified by TLC separations. There was little or no conjugation of steroids by the testes, except during the spawning season, when glucuronides of androstenedione and testosterone were produced.

Relation: Joss, JMP and Edwards, A and Kime, DE (1996) In vitro biosynthesis of androgens in the Australian lungfish, Neoceratodus forsteri. General and Comparative Endocrinology, 101 (3). pp. 235-343. ISSN 0016-6480

Format: application/pdf
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The serum concentration of testosterone was estimated from a population of wild lungfish over 6–7 years of sampling. Male lungfish were found to have high circulating levels of testosterone (50 ng/ml) which varied seasonally and could be correlated with ...
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Thyroid hormone deiodinases revisited : insights from lungfish : a review

Author/Creator: Sutija, M, Joss, J. M. P
Resource type: journal article
Date: 2006
Subject: deiodinase, selenoprotein
Record contributed by: Macquarie University

Full Record and related resources:
http://hdl.handle.net/1959.14/14535
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http://hdl.handle.net/1959.14/14535

Description
In vertebrates, hormones released from the thyroid gland travel in the circulation to target tissues where they may be processed by deiodinating enzymes into more active or inactive iodothyronines. In mammals, there are three deiodinating enzymes described. Type1 (D1), which primarily occurs in the liver, converts reverse T3 into T2 for clearance. It also converts T4 into T3. This production of T3 is believed to contribute to the bulk of circulating T3 in mammals. The type2 (D2) enzyme may be found in many other tissues where it converts T4 to T3, which is then transferred to the receptors in the nucleus of the same cell, i.e. does not contribute to the circulating T3. The type3 (D3) enzyme converts T3 into T2. The expression of the genes for these three enzymes and/or the activity of the enzymes have been studied in several non-mammalian groups of vertebrates. From agnathans to birds, D2 and D3 appear to occur universally, with the possible exception of squamate reptiles (lack D2?). D1 has not been found in amphibians, lungfish or agnathans. All three enzymes are selenoproteins, in which a selenocysteine is found in the active centre. The nucleotide code for translation of a selenocysteine is UGA, which under normal circumstances is a stop codon. In order for UGA to code for selenocysteine, there must be a SECIS element in the 3'UTR of the mRNA. Any disruption of the SECIS will result in a truncated protein in the region of its active centre. It is suggested that such alternative splicing may be a mode of altering the expression of deiodinases in particular tissues to change the response of such tissues to thyroid hormones under differing circumstances such as stages of development.

6 page(s)

Publisher: Springer Verlag
Contributor: Macquarie University. Dept. of Biological Sciences
Relation: Journal of comparative physiology B : biochemical, systemic, and environmental physiology , Vol. 176, Issue 2, p.87-92; 10.1007/s00360-005-0018-y

Other identifier: ISSN:1432-136X; mq-rm-2006006082
Language: eng
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In vertebrates, hormones released from the thyroid gland travel in the circulation to target tissues where they may be processed by deiodinating enzymes into more active or inactive iodothyronines. In mammals, there are three deiodinating enzymes described. ...
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conservation genetics and the Australian lungfish Neoceratodus forsteri; a spatio-temporal study of population structure

Author/Creator: Lissone, I
Resource type: thesis
Date: 2003
Subject: Neoceratodus forsteri, population genetics, endemic species
Record contributed by: University of the Sunshine Coast

Full Record and related resources:
http://research.usc.edu.au/vital/access/manager/Repository/usc:910
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http://research.usc.edu.au/vital/access/manager/Repository/usc:910

Description
Neoceratodus forsteri is a phylogenetically distinct ancient lineage with a natural distribution restricted to 3 catchments in the southeast Queensland region. Modifications to the river systems they are restricted to has prompted concern for the persistence of this species in the face of such changes. Accordingly, ecological and molecular surveys have been undertaken to identify the management units in order to design and implement a sound management strategy. Ecological surveys of the Burnett catchment have highlighted that compounding factors of longevity, low reproductive output and loss of suitable spawning sites through seasonal fluctuations as well as habitat degradation have greatly reduced juvenile recruitment rates. Genetic surveys investigating allozyme , mtDNA and microsatellite markers show that despite substantial barriers to gene flow, lungfish populations comprise of one homogenous population. This lack of diversity was attributed to historic and present bottleneck events, as well as to historic fluvial connectivity. To obtain a broader snapshot of the genome, this survey developed and screened RAF and AFLP multi-locus markers, as well as a microsatellite library. Moreover, in a study complementing previous ATPase survey of contemporary populations, sequence data from this region was evaluated from formalin preserved adult specimens (collection dates range between 1912 and 1976). This study has shown that the common ATPase haplotype found in contemporary populations was also present among specimens collected from 1912. Further, the high prevalence of rare alleles recorded from modern Mary populations was also recorded from formalin preserved specimens. AFLP banding profiles were monomorphic; by contrast, variation detected by RAF markers identified significant patterns of substructure between catchments. Significant structure was also recorded between impounded populations and non-impounded populations. Lungfish populations have a relatively narrow range and occur within regulated fluvial systems. Habitat degradation is implicated in reduction of spawning sites. Combined with low juvenile recruitment these effects greatly reduce the effective population size. The phyletic age of this species, in conjunction with low genetic diversity greatly increases its vulnerability to environmental change or novel diseases. In accordance with the World Conservation Union (IUCN), genetic diversity is one of three recognised levels requiring conservation.

Submitted in fulfillment of the requirements of the degree of Masters of Science, University of the Sunshine Coast, 2003.


Language: eng
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Neoceratodus forsteri is a phylogenetically distinct ancient lineage with a natural distribution restricted to 3 catchments in the southeast Queensland region. Modifications to the river systems they are restricted to has prompted concern for the persistence ...
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Movement patterns and Habitat use in the Queensland lungfish Neoceratodus forsteri (Krefft 1870)

Author/Creator: Kind, P. K.
Resource type: thesis
Subject: 300701 Physiology and Genetics, 630300 Fish
Record contributed by: Australasian Digital Theses Program, The University of Queensland

Full Record and related resources:
http://espace.library.uq.edu.au/view/UQ:106238
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http://espace.library.uq.edu.au/view/UQ:106238

Description
None Available


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None Available
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Early development of neural tissues and mesenchyme in the Australian lungfish Neoceratodus forsteri (Osteichthyes: Dipnoi)

Author/Creator: Kemp, A. R.
Resource type:
Date: 2000
Subject: Zoology (270500)
Record contributed by: The University of Queensland

Full Record and related resources:
http://espace.library.uq.edu.au/view/UQ:139315
isMemberOf Centre for Microscopy and Microanalysis Publications http://espace.library.uq.edu.au/list/UQ:3919
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http://espace.library.uq.edu.au/view/UQ:139315
isMemberOf Centre for Microscopy and Microanalysis Publications http://espace.library.uq.edu.au/list/UQ:3919

Description
None Available

Publisher: Cambridge University Press

Coverage: 2000-01-01T00:00:00Z
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None Available
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Early evolution of vertebrate photoreception: lessons from lampreys and lungfishes

Author/Creator: Collin, Shaun P.
Resource type:
Date: 2009
Subject: Coastal and Estuarine Flora, Fauna and Biodiversity (960802), Vertebrate Biology (060809), Color vision, Evolution, Fishes, Photoreceptors, Retina
Record contributed by: The University of Queensland

Full Record and related resources:
http://espace.library.uq.edu.au/view/UQ:186060
isMemberOf School of Biomedical Sciences Publications http://espace.library.uq.edu.au/list/UQ:3823
isMemberOf 2010 Higher Education Research Data Collection http://espace.library.uq.edu.au/list/UQ:174061
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http://espace.library.uq.edu.au/view/UQ:186060
isMemberOf School of Biomedical Sciences Publications http://espace.library.uq.edu.au/list/UQ:3823
isMemberOf 2010 Higher Education Research Data Collection http://espace.library.uq.edu.au/list/UQ:174061

Description
Lampreys (Agnatha) and lungfish (Dipnoi) are representatives of the earliest and the intermediate stages in vertebrate evolution, respectively, and survived in the Cambrian (approximately 540 mA, lampreys) and Devonian (approximately 400 mA, lungfishes) Periods. The unique phylogenetic position of these two groups presents us with an exciting opportunity to understand life in ancient times and to begin to trace the evolution of vision and photoreception in vertebrates. Using a multidisciplinary approach employing anatomical and molecular techniques, the evolution of photoreception is explored in these extant, living fossils to predict the environmental lighting conditions to which our vertebrate ancestors were exposed. Contrary to expectations, the retinae of the southern hemisphere lamprey (Geotria australis Gray, 1851) and the Australian lungfish (Neoceratodus forsteri Krefft, 1870) are far from "primitive," each possessing five types of photoreceptors, many with spectral filters for tuning the light. Detailed ultrastructural analysis reveals that all five receptor types in G. australis are cone-like, whereas N. forsteri possesses four cone types and a single type of rod. Each receptor type also contains a different visual pigment (opsin gene); that is, LWS, SWS1, SWS2, RhA and RhB in G. australis and LWS, SWS1, SWS2, Rh1 and Rh2 in N. forsteri, all of which are expressed within the retina and are sensitive to different parts of the electromagnetic spectrum, providing the potential for pentachromatic and tetrachromatic color vision, respectively.

Publisher: Wiley-Blackwell Publishing Ltd.
Contributor: Zhibin Zhang

Coverage: 2009-03-01T00:00:00Z
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Lampreys (Agnatha) and lungfish (Dipnoi) are representatives of the earliest and the intermediate stages in vertebrate evolution, respectively, and survived in the Cambrian (approximately 540 mA, lampreys) and Devonian (approximately 400 mA, lungfishes) Periods. ...
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A view of early vertebrate evolution inferred from the phylogeny of polystome parasites (Monogenea: Polystomatidae)

Author/Creator: Verneau, Olivier, Bentz, Sophie, Sinnappah, Neeta Devi, du Preez, Louis, Whittington, Ian David, Combes, Claude
Resource type: journal article
Date: 2002, 2006
Subject: No Subjects
Record contributed by: The University of Adelaide

Full Record and related resources:
http://hdl.handle.net/2440/12294
http://link.library.adelaide.edu.au/?atitle=A%20view%20of%20early%20vertebrate%20evolution%20inferred%20from%20the%20phylogeny%20of%20polystome%20parasites%20(Monogenea:%20Polystomatidae)&aulast=Verneau&issn=0962-8452&title=Proceedings%20of%20the%20Royal%20Society%20of%20London%20Series%20B-Biological%20Sciences&volume=269&date=2002&pages=535-543&spage=535&epage=543
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http://hdl.handle.net/2440/12294
http://link.library.adelaide.edu.au/?atitle=A%20view%20of%20early%20vertebrate%20evolution%20inferred%20from%20the%20phylogeny%20of%20polystome%20parasites%20(Monogenea:%20Polystomatidae)&aulast=Verneau&issn=0962-8452&title=Proceedings%20of%20the%20Royal%20Society%20of%20London%20Series%20B-Biological%20Sciences&volume=269&date=2002&pages=535-543&spage=535&epage=543

Description
Copyright © 2002 The Royal Society

The Polystomatidae is the only family within the Monogenea to parasitize sarcopterygians such as the Australian lungfish Neoceratodus poisteri and freshwater tetrapods (lissamphibians and chelonians). We present a phylogeny based on partial 18S rDNA sequences of 26 species of Polystomatidae and three taxon from the infrasubclass Oligonchoinea (= Polyopisthocotylea) obtained from the gills of teleost fishes. The basal position of the polystome from lungfish within the Polystomatidae suggests that the family arose during the evolutionary transition between actinopterygians and sarcopterygians, ca. 425 million years (Myr) ago. The monophyly of the polystomatid lineages from chelonian and lissamphibian hosts, in addition to estimates of the divergence times, indicate that polystomatids from turtles radiated ca. 191 Myr ago, following a switch from an aquatic amniote presumed to be extinct to turtles, which diversified in the Upper Triassic. Within polystomatids from lissamphibians, we observe a polytomy of four lineages, namely caudatan, neobatrachian, pelobatid and pipid polystomatid lineages, which occurred ca. 246 Myr ago according to molecular divergence-time estimates. This suggests that the first polystomatids of amphibians originated during the evolution and diversification of lissamphibian orders and suborders ca. 250 Myr ago. Finally, we report a vicariance event between two major groups of neobatrachian polystomes, which is probably linked to the separation of South America from Africa ca. 100 Myr ago.

Olivier Verneau, Sophie Bentz, Neeta Devi Sinnappah, Louis du Preez, Ian Whittington and Claude Combes

Publisher: The Royal Society
Contributor: School of Earth and Environmental Sciences : Ecology and Evolutionary Biology

Other identifier: Proceedings of the Royal Society of London Series B - Biological Sciences, 2002; 269 (1490):535-543; 0962-8452; 0020021454; 10.1098/rspb.2001.1899; 000174543200015
Language: en_US
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The Polystomatidae is the only family within the Monogenea to parasitize sarcopterygians such as the Australian lungfish Neoceratodus poisteri and freshwater tetrapods (lissamphibians and chelonians). We present a phylogeny based on partial 18S rDNA sequences ...
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From Trove
 
Lungfish evolution and development (Trove)  
Only abstract available online for free.   For sale online. 
    "The first vertebrates recognizable as tetrapods appeared in the mid-Devonian. It is generally agreed that their ancestors were lobe-finned fish. What is not agreed is how close either of the extant groups of lobe-finned fish, lungfish or coelacanths, is to the actual ancestor of the tetrapods.
    The soft anatomy of living lungfish shares many similarities with that of living amphibians. Many of these similarities are not present in either coelacanths or any members of the other extant bony fish group, the ray-finned fishes.
    Many very well preserved lungfish from the Devonian possess specialized features that would appear to exclude them from being ancestral to tetrapods. I am hypothesizing that lungfish in the Devonian may have included metamorphosis in their life cycle and that neoteny in some species may have been an early corollary. These reproductively mature neotenous lungfish would not have had the specialised features of metamorphosed adults. Fossils of these neotenous forms may have more closely resembled the tetrapod ancestral lobe-finned fish, currently believed to be a panderichthiad fish. Living lungfish have a number of larval features, which suggest paedomorphosis.
    Also of significance is the very large genome of living lungfish, which, in urodele amphibians, is a feature correlated with neoteny. Our current knowledge of the thyroid axis in the lungfish, Neoceratodus forsteri, is consistent with neoteny in amphibians, but the only Devonian fossil considered to be a larval lungfish bears no resemblance to living lungfish or to panderichthiads. The enigmatic phylogenetic relationship of lungfish with the first tetrapods remains, but the hunt for other forms of larval Devonian lungfish is on! 5 page(s)
"    






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