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The Australian lungfish is a primitive and endangered representative of the subclass Dipnoi. The distribution of this species is limited to south‐east Queensland, with some populations considered endemic and others possibly descending from translocations in the late nineteenth century shortly after European discovery. Attempts to resolve the historical distribution of this species have met with conflicting results based on descriptive genetic studies. Understanding if all populations are endemic or some are the result of, or influenced by, translocation events, has implications for conservation management. In this work, we analysed the genetic variation at three types of markers (mtDNA genomes, 11 STRs and 5196 nuclear SNPs) using the approximate Bayesian computation (ABC) algorithm to compare several demographic models. We postulated different contributions of Mary River and Burnett River gene pools into the Brisbane River and North Pine River populations, related to documented translocation events. We ran the analysis for each marker type separately, and we also estimated the posterior probabilities of the models combining the markers. Nuclear SNPs have the highest power to correctly identify the true model among the simulated datasets (where the model was known), but different marker types typically provided similar answers. The most supported demographic model able to explain the real dataset implies that an endemic gene pool is still present in the Brisbane and North Pine Rivers and coexists with the gene pools derived from past documented translocation events. These results support the view that ABC modelling can be useful to reconstruct complex historical translocation events with contemporary implications, and will inform ongoing conservation efforts for the endangered and iconic Australian lungfish. [ABSTRACT FROM AUTHOR]

This paper assembles evidence collected over several decades to conclude that populations of the Australian lungfish in south-east Queensland are not reproducing sufficiently to guarantee survival of the species in the region. The environment of the Australian lungfish (Neoceratodus forsteri) has been altered over the past 50 years. Biodiversity of plants and animals has been lost. Water impoundments without effective fish transfer devices have been built over rivers. Submerged aquatic plants used by lungfish as spawning sites and refuges for the young have been significantly reduced in numbers, and food animals are absent or much less common. Lungfish used to spawn in a number of habitats in rivers and lakes in natural and translocated environments in south-east Queensland, in response to increasing photoperiod in spring. Oviposition events were cyclical, rising from low levels to a peak in successive years and then falling again. High levels of recruitment have, in the past, followed high levels of spawning activity, but recruitment depends on other factors as well. It should be noted that, while the sole trigger for spawning is photoperiod, many factors influence recruitment, such as food availability, refuges for young fish and the effects of predation, as well as the amount and type of food gathered by adult lungfish prior to the spawning season, and whether adults have been able to supply the eggs with appropriate nutrients. Spawning, and the survival of young, are now affected by environmental degradation, with extensive loss of biodiversity in freshwater environments where lungfish live. More to the point, recent attempts to use 14C dating to assess the age structure of lungfish populations are flawed and do not support claims that recruitment in lungfish habitats is continuing. Data on spawning included in this paper, and recent reports of recruitment success in several habitats, indicate that this is not the case. [ABSTRACT FROM AUTHOR]

The Australian lungfish has been studied for more than a century without any knowledge of the longevity of the species. Traditional methods for ageing fish, such as analysis of otolith (ear stone) rings is complicated in that lungfish otoliths differ from teleost fish in composition. As otolith sampling is also lethal, this is not appropriate for a protected species listed under Australian legislation. Lungfish scales were removed from 500 fish from the Brisbane, Burnett and Mary rivers. A sub–sample of scales (85) were aged using bomb radiocarbon techniques and validated using scales marked previously with oxytetracycline. Lungfish ages ranged from 2.5–77 years of age. Estimated population age structures derived using an Age Length Key revealed different recruitment patterns between river systems. There were statistically significant von Bertalanffy growth model parameters estimated for each of the three rivers based on limited sample sizes. In addition, length frequency distributions between river systems were also significantly different. Further studies will be conducted to review drivers that may explain these inter-river differences. [ABSTRACT FROM AUTHOR]

Abstract: An important challenge for conservation science is to detect declines in intraspecific diversity so that management action can be guided towards populations or species at risk. The lifespan of Australian lungfish (Neoceratodus forsteri) exceeds 80 years, and human impacts on breeding habitat over the last half century may have impeded recruitment, leaving populations dominated by old postreproductive individuals, potentially resulting in a small and declining breeding population. Here, we conduct a “single‐sample” evaluation of genetic erosion within contemporary populations of the Australian lungfish. Genetic erosion is a temporal decline in intraspecific diversity due to factors such as reduced population size and inbreeding. We examined whether young individuals showed signs of reduced genetic diversity and/or inbreeding using a novel bomb radiocarbon dating method to age lungfish nonlethally, based on 14C ratios of scales. A total of 15,201 single nucleotide polymorphic (SNP) loci were genotyped in 92 individuals ranging in age from 2 to 77 years old. Standardized individual heterozygosity and individual inbreeding coefficients varied widely within and between riverine populations, but neither was associated with age, so perceived problems with recruitment have not translated into genetic erosion that could be considered a proximate threat to lungfish populations. Conservation concern has surrounded Australian lungfish for over a century. However, our results suggest that long‐lived threatened species can maintain stable levels of intraspecific variability when sufficient reproductive opportunities exist over the course of a long lifespan. [ABSTRACT FROM AUTHOR]

Neoceratodus forsteri: is a freshwater species of Dipnoan currently listed as ‘vulnerable to extinction’ under Australian legislation. The species is restricted to at least two indigenous riverine populations in southeastern Queensland, and several other putatively translocated populations. Current understanding of genetic relationships among populations is based on studies of allozymes, microsatellites and mitochondrial DNA (mtDNA) fragments. A notable feature of all these datasets was low genetic variability. Here we sequence the complete mitogenome of 71 N. forsteri individuals from five populations to improve resolution of mtDNA diversity, examine relationships among populations, and evaluate recent demographic history. We recorded 137 variable positions forming 41 haplotypes in the 16,573 bp mitogenome alignment. Strong genetic structure was observed among riverine samples (global ΦST = 0.342) in a pattern consistent with translocation history. Tinana Creek was confirmed as an isolated and genetically unique subpopulation that should be recognized as a distinct management unit. Two previously unreported mtDNA clades (0.46% mean divergence) were found and suggest that genetic exchange among coastal catchments may have been facilitated by riverine connections on the exposed continental shelf during the late Pleistocene. Extended Bayesian skyline analysis showed no evidence for recent historical change in female effective population size, and codon-based selection tests found no evidence for positive selection in coding genes. Overall, our results emphasise the utility of the full mtDNA molecule for capturing population structure in taxa with low genetic diversity. In such cases, informative variation may be scattered across disparate parts of the mitogenome. Surveying relatively short fragments of mtDNA may lead to significant underestimates of population structure when applied to threatened species with low genetic diversity. [ABSTRACT FROM AUTHOR]

Anomalies in embryos and hatchlings of the Australian lungfish are now found in many of the environments inhabited by lungfish, such as reservoirs (Lakes) created over natural rivers and affect many tissues and organs in the body, most obviously the epidermis and related sense organs, but extending to blood vessels and skeletal structures as well. Development of muscular tissues is affected, but only by the lack of nutrition in the eggs as laid by the parents and by failure of the hatchlings to feed. They are found in embryos collected from the Lakes and reared in the laboratory by standard methods and are also present in embryos and hatchlings collected directly from the Lakes. They are not found in fish collected from unaltered parts of Rivers below the Lakes. Recently, in the Lakes, the anomalies are so widespread and so serious, that they affect all the young of one season. The most probable cause of abnormal development is a lack of volatile fatty acids in the diet of adults, resulting in the production of poor quality eggs, as has been found in other species of fish. The results of this study have serious implications for survival of the species, since almost every habitat where lungfish are found and are still spawning, has now been altered by the building of water impoundments. Restoration of freshwater environments in south-east Queensland should be a priority for the State and Federal Governments and for water authorities. [ABSTRACT FROM AUTHOR]

Disease due to non-tuberculous mycobacteria ( NTM) is common in fish. Current recommendations focus on outbreak management by depopulating entire fish stocks and disinfecting tanks. Treatment is not advocated. Treatment may be appropriate, however, where individual, valuable fish are concerned. ZSL London Zoo managed an outbreak of mycobacteriosis in a valuable group of imported F1 captive-bred Australian lungfish ( Neoceratodus fosteri) by depopulation, isolation, extensive testing and daily oral antibiotic treatment. Four species of Mycobacterium ( M. marinum, M. fortuitum, M. chelonae and M. peregrinum) were involved in this outbreak, each with unique antibiotic sensitivities. Triple therapy with rifampicin, doxycycline and enrofloxacin for 8 months was the most effective antibiotic combination, resulting in full disease resolution. No side effects were noted and, more than 18 months post-treatment, no recurrence had occurred. This is the first report of mycobacterial disease in lungfish and the first report of a polymycobacterial outbreak in fish involving these four species of Mycobacterium. This report demonstrates the value of extensive isolation and identification. Also, as therapies currently advised in standard texts did not reflect the antibiotic sensitivity of the NTM found in the fish reported here, we recommend that antibiotic treatment should always be based on sensitivity testing. [ABSTRACT FROM AUTHOR]

Argonaute (AGO) family proteins play many roles in epigenetic programming, genome rearrangement, mRNA breakdown, inhibition of translation, and transposon silencing. Despite being a hotspot in current scientific research, their evolutionary history is still poorly understood and consequently the identification of evolutionary conserved structural features should also generate useful information for better understanding their functions. We report here for the first time the transcript sets of the two subfamilies, Ago and Piwi, in the West African lungfish Protopterus annectens and in the Indonesian coelacanth Latimeria menadoensis, two key species in the evolutionary lineage leading to tetrapods. The phylogenetic analysis of 142 inferred protein sequences in 22 fully sequenced species and the analysis of microsynteny performed in the major vertebrate lineages indicate an intricate pattern for the evolution of both subfamilies that has been shaped by whole genome duplications and lineage specific gains and losses. The argonaute subfamily was additionally expanded by local gene duplications at the base of the jawed vertebrate lineage. The subfamily of Piwi proteins is involved in several processes such as spermatogenesis, piRNA biogenesis, and transposon repression. Expression assessment of AGO genes and genes coding for proteins involved in small RNA biogenesis suggests a limited activity of the Piwi pathway in lungfish in agreement with the lungfish genome containing mainly old and inactive transposons. [ABSTRACT FROM AUTHOR]

Three systems, two sensory and one protective, are present in the skin of the living Australian lungfish, Neoceratodus forsteri , and in fossil lungfish, and the arrangement and innervation of the sense organs is peculiar to lungfish. Peripheral branches of nerves that innervate the sense organs are slender and unprotected, and form before any skeletal structures appear. When the olfactory capsule develops, it traps some of the anterior branches of cranial nerve V, which emerged from the chondrocranium from the lateral sphenotic foramen. Cranial nerve I innervates the olfactory organ enclosed within the olfactory capsule and cranial nerve II innervates the eye. Cranial nerve V innervates the sense organs of the snout and upper lip, and, in conjunction with nerve IX and X, the sense organs of the posterior and lateral head. Cranial nerve VII is primarily a motor nerve, and a single branch innervates sense organs in the mandible. There are no connections between nerves V and VII, although both emerge from the brain close to each other. The third associated system consists of lymphatic vessels covered by an extracellular matrix of collagen, mineralised as tubules in fossils. Innervation of the sensory organs is separate from the lymphatic system and from the tubule system of fossil lungfish. [ABSTRACT FROM AUTHOR]

Although the brains of the three extant lungfish genera have been previously described, the spatial relationship between the brain and the neurocranium has never before been fully described nor quantified. Through the application of virtual microtomography (μCT) and 3D rendering software, we describe aspects of the gross anatomy of the brain and labyrinth region in the Australian lungfish, Neoceratodus forsteri and compare this to previous accounts. Unexpected characters in this specimen include short olfactory peduncles connecting the olfactory bulbs to the telencephalon, and an oblong telencephalon. Furthermore, we illustrate the endocast (the mould of the internal space of the neurocranial cavity) of Neoceratodus, also describing and quantifying the brain-endocast relationship in a lungfish for the first time. Overall, the brain of the Australian lungfish closely matches the size and shape of the endocast cavity housing it, filling more than four fifths of the total volume. The forebrain and labyrinth regions of the brain correspond very well to the endocast morphology, while the midbrain and hindbrain do not fit so closely. Our results cast light on the gross neural and endocast anatomy in lungfishes, and are likely to have particular significance for palaeoneurologists studying fossil taxa. [ABSTRACT FROM AUTHOR]

The Australian lungfish Neoceratodus forsteri is an endangered native fish species currently protected under federal and international agreements. The impoundment of riverine habitats by water storages has substantially decreased the availability of dense beds of macrophyte (e.g. Vallisneria nana) in shallow water, the preferred spawning habitat of Australian lungfish. Storage management, such as storage drawdown and maintaining storages at specific levels, may impede establishment and development of dense macrophyte beds, although the effects of storage operation on macrophytes are poorly understood. Storage bathymetry and modelled stream data were used to examine the impact of water level changes (frequency and magnitude) on V. nana habitat within storages and associated riverine areas. Three storages located within the natural range of the Australian lungfish in the Burnett River (Ben Anderson Barrage, Ned Churchward Weir and Paradise Dam) were found to provide limited potential for V. nana habitat when at the full supply level. Furthermore, water storages within the distribution of Australian lungfish fluctuate by ±1 m more frequently in comparison to associated riverine environments. These frequent water level fluctuations challenge the establishment of dense macrophyte beds required for lungfish spawning. Since aquatic macrophytes and streamflow play an integral role in lungfish spawning, management of water storages should focus on releases to the downstream reaches. These releases should mimic natural flow and water temperature regimes to allow establishment and growth of V. nana beds in synchrony with the timing of Australian lungfish spawning. Riverine reaches downstream of storages have the greatest potential for restoration of macrophyte beds. © 2014 Queensland Government, Department of Natural Resources and Mines. River Research and Applications © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The Australian lungfish is a unique living representative of an ancient dipnoan lineage, listed as ‘vulnerable’ to extinction under Australia’s Environment Protection and Biodiversity Conservation Act 1999. Historical accounts indicate this species occurred naturally in two adjacent river systems in Australia, the Burnett and Mary. Current day populations in other rivers are thought to have arisen by translocation from these source populations. Early genetic work detected very little variation and so had limited power to answer questions relevant for management including how genetic variation is partitioned within and among sub-populations. In this study, we use newly developed microsatellite markers to examine samples from the Burnett and Mary Rivers, as well as from two populations thought to be of translocated origin, Brisbane and North Pine. We test whether there is significant genetic structure among and within river drainages; assign putatively translocated populations to potential source populations; and estimate effective population sizes. Eleven polymorphic microsatellite loci genotyped in 218 individuals gave an average within-population heterozygosity of 0.39 which is low relative to other threatened taxa and for freshwater fishes in general. Based on FST values (average over loci = 0.11) and STRUCTURE analyses, we identify three distinct populations in the natural range, one in the Burnett and two distinct populations in the Mary. These analyses also support the hypothesis that the Mary River is the likely source of translocated populations in the Brisbane and North Pine rivers, which agrees with historical published records of a translocation event giving rise to these populations. We were unable to obtain bounded estimates of effective population size, as we have too few genotype combinations, although point estimates were low, ranging from 29 - 129. We recommend that, in order to preserve any local adaptation in the three distinct populations that they be managed separately. [ABSTRACT FROM AUTHOR]

Many fossil lungfish have a system of mineralised tubules in the dermis of the snout, branching extensively and radiating towards the epidermis. The tubules anastomose in the superficial layer of the dermis, forming a plexus consisting of two layers of vessels, with branches that expand into pore canals and flask organs, flanked by cosmine nodules where these are present. Traces of this system are found in the Australian lungfish, Neoceratodus forsteri , consisting of branching tubules in the dermis, a double plexus below the epidermis and dermal papillae entering the epidermis without reaching the surface. In N. forsteri , the tubules, the plexus and the dermal papillae consist of thick, unmineralised connective tissue, enclosing fine blood vessels packed with lymphocytes. Tissues in the epidermis and the dermis of N . forsteri are not associated with deposits of calcium, which is below detectable limits in the skin of the snout at all stages of the life cycle. Canals of the sensory line system, with mechanoreceptors, are separate from the tubules, the plexus and the dermal papillae, as are the electroreceptors in the epidermis. The system of tubules, plexus, dermal papillae and lymphatic capillaries may function to protect the tissues of the snout from infection. [ABSTRACT FROM AUTHOR]

Few of the localities currently inhabited by the Australian lungfish, Neoceratodus forsteri, are in pristine condition. Most populations of wild lungfish in south-east Queensland are now isolated in reservoirs. The barriers formed by the building of dams and weirs across natural rivers separate lungfish groups from each other, cut across possible pathways for normal movement in the environment, and have additional and more serious effects. Water levels in reservoirs fluctuate in spring when lungfish are spawning, and do not allow dense stands of submerged aquatic plants to become established. Lungfish need these plants as sites for oviposition, and newly hatched young need them as refuges and sources of food. Potential recruitment of young lungfish in reservoir populations faces another threat, that of anomalous development of the embryos, hatchlings and juveniles, severe enough to kill many embryos within days of oviposition, and destroy the young fish before they are more than a few months old. Similar anomalies are not present in young fish from a river environment raised under identical conditions. Reasons for poor development, which has now been found in two reservoirs, may be related to the diet of the adult lungfish, and possibly to genetic factors. Many wild lungfish are now trapped in reservoirs, where water levels vary, and there are no refuges for eggs and young, and no sources of food. Potential recruitment of young lungfish in reservoirs faces another threat. Eggs and hatchlings are abnormal, and all the young in one season may die. [ABSTRACT FROM AUTHOR]

This study assessed the spawning activity of the threatened Australian lungfish Neoceratodus forsteri by measuring egg densities within the artificial habitat of a large impoundment (Lake Wivenhoe, Australia). Eggs were sampled (August to November 2009) from multiple locations across the impoundment, but occurred at highest densities in water shallower than 40 cm along shorelines with a dense cover of submerged terrestrial vegetation. The numbers of eggs declined over the study period and all samples were dominated by early developmental stages and high proportions of unviable eggs. The quality of the littoral spawning habitats declined over the study as flooded terrestrial grasses decomposed and filamentous algae coverage increased. Water temperatures at the spawning site exhibited extreme variations, ranging over 20·4° C in water shallower than 5 cm. Dissolved oxygen concentrations regularly declined to <1 mg l−1 at 40 and 80 cm water depth. Spawning habitats utilised by N. forsteri within impoundments expose embryos to increased risk of desiccation or excessive submergence through water-level variations, and extremes in temperature and dissolved oxygen concentration that present numerous challenges for successful spawning and recruitment of N. forsteri in large impoundment environments. [ABSTRACT FROM AUTHOR]

ABSTRACT The Australian lungfish is an endangered native species currently protected under various state, federal and international agreements. Scarce information on their early life history is available due to the absence of juveniles collected in the wild. This has led to concerns about the sustainability of the species and become a driver for the conservation effort for Australian lungfish. This study aimed to consolidate knowledge on the critical hydraulic habitat requirements of this species within a water resource management context. In this study, spawning of Australian lungfish was found to be a seasonal strategy that is highly reliant on a variable low-flow regime within riverine habitat. Suitable conditions for spawning were characterized by small flow events in early-to-mid spring when water temperatures are between 18 and 28 °C, leading to oviposition on short dense macrophytes in shallow water. Importantly, many of the key environmental factors driving the ecological response are manageable through existing water resource infrastructure. Specifically, releases from water storages within the current distribution of Australian lungfish should mimic the natural inflow and temperature regime within the spawning period, and also provide suitable riverine habitat within projected full supply limits. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: Our current understanding of the lungfish immune system is limited. This study is characterizing the immune cells separated from primary and secondary immune organs of the Australian lungfish, Neoceratodus forsteri. Our functional studies utilized flow cytometry to study the immune cells extracted from the thymus, spiral valve intestine, spleen, and kidney. The different characteristics of lymphocytes and granulocytes were analyzed by utilization of viability, phagocytosis, oxidative burst, and apoptosis assays. Most of the nonviable intestinal cells were lymphocytes. Depending on the organ, 6–25% of the total population, predominantly granulocytes, underwent phagocytosis where the splenic cells were the most and intestinal cells the least phagocytic cells. Cells responded positively but differently to stimulation with phorbol myristate acetate (PMA) to produce radical oxygen species, an indication of their oxidative burst activity, which was mainly associated with granulocytes. Although cells were induced by dexamethasone to undergo apoptosis, such an induction did not follow a consistent pattern of dose of dexamethasone or incubation time between the different organs. In the absence of monoclonal antibodies against lungfish immune cells, these functional flow cytometric analyses aid our understanding on the functionality of immune cells. [Copyright &y& Elsevier]

Background: The fish-tetrapod transition was one of the major events in vertebrate evolution and was enabled by many morphological changes. Although the transformation of paired fish fins into tetrapod limbs has been a major topic of study in recent years, both from paleontological and comparative developmental perspectives, the interest has focused almost exclusively on the distal part of the appendage and in particular the origin of digits. Relatively little attention has been paid to the transformation of the pelvic girdle from a small unipartite structure to a large tripartite weight-bearing structure, allowing tetrapods to rely mostly on their hindlimbs for locomotion. In order to understand how the ischium and the ilium evolved and how the acetabulum was reoriented during this transition, growth series of the Australian lungfish Neoceratodus forsteri and the Mexican axolotl Ambystoma mexicanum were cleared and stained for cartilage and bone and immunostained for skeletal muscles. In order to understand the myological developmental data, hypotheses about the homologies of pelvic muscles in adults of Latimeria, Neoceratodus and Necturus were formulated based on descriptions from the literature of the coelacanth (Latimeria), the Australian Lungfish (Neoceratodus) and a salamander (Necturus). Results: In the axolotl and the lungfish, the chondrification of the pelvic girdle starts at the acetabula and progresses anteriorly in the lungfish and anteriorly and posteriorly in the salamander. The ilium develops by extending dorsally to meet and connect to the sacral rib in the axolotl. Homologous muscles develop in the same order with the hypaxial musculature developing first, followed by the deep, then the superficial pelvic musculature. Conclusions: Development of the pelvic endoskeleton and musculature is very similar in Neoceratodus and Ambystoma. If the acetabulum is seen as being a fixed landmark, the evolution of the ischium only required pubic pre-chondrogenic cells to migrate posteriorly. It is hypothesized that the iliac process or ridge present in most tetrapodomorph fish is the precursor to the tetrapod ilium and that its evolution mimicked its development in modern salamanders. [ABSTRACT FROM AUTHOR]

Epithelial sodium channel (ENaC) is a Na[+]-selective, aldosterone-stimulated ion channel involved in sodium transport homeostasis. ENaC is rate-limiting for Na[+] absorption in the epithelia of osmoregulatory organs of tetrapods. Although the ENaC/degenerin gene family is proposed to be present in metazoans, no orthologues or paralogues for ENaC have been found in the genome databases of teleosts. We studied full-length cDNA cloning and tissue distributions of ENaCα, β and γ subunits in the Australian lungfish, Neoceratodus forsteri, which is the closest living relative of tetrapods. Neoceratodus ENaC (nENaC) comprised three subunits: nENaCα, β and γ proteins. The nENaCα, β and γ subunits are closely related to amphibian ENaCα, β and γ subunits, respectively. Three ENaC subunit mRNAs were highly expressed in the gills, kidney and rectum. Amiloride-sensitive sodium current was recorded from Xenopus oocytes injected with the nENaCαβγ subunit complementary RNAs under a two-electrode voltage clamp. nENaCα immunoreactivity was observed in the apical cell membrane of the gills, kidney and rectum. Thus, nENaC may play a role in regulating sodium transport of the lungfish, which has a renin-angiotensin-aldosterone system. This is interesting because there may have been an ENaC sodium absorption system controlled by aldosterone before the conquest of land by vertebrates. [ABSTRACT FROM AUTHOR]

Lungfishes (dipnoans) are currently considered the closest living relatives of tetrapods. The organization of the cholinergic systems in the brain has been carefully analyzed in most vertebrate groups, and major shared characteristics have been described, although traits particular to each vertebrate class have also been found. In the present study, we provide the first detailed information on the distribution of cholinergic cell bodies and fibers in the central nervous system in two representative species of lungfishes, the African lungfish ( Protopterus dolloi) and the Australian lungfish ( Neoceratodus forsteri), as revealed by immunohistochemistry against the enzyme choline acetyltransferase (ChAT). Distinct groups of ChAT immunoreactive (ChAT-ir) cells were observed in the basal telencephalon, habenula, isthmic nucleus, laterodorsal tegmental nucleus, cranial nerve motor nuclei, and the motor column of the spinal cord, and these groups seem to be highly conserved among vertebrates. In lungfishes, the presence of a cholinergic cell group in the thalamus and the absence of ChAT-ir cells in the tectum are variable traits, unique to this group and appearing several times during evolution. Other characters were observed exclusively in Neoceratodus, such as the presence of cholinergic cells in the suprachiasmatic nucleus, the pretectal region and the superior raphe nucleus. Cholinergic fibers were found in the medial pallium, basal telencephalon, thalamus and prethalamus, optic tectum and interpeduncular nucleus. Comparison of these results with those from other classes of vertebrates, including a segmental analysis to correlate cell populations, reveals that the cholinergic systems in lungfishes largely resemble those of amphibians and other tetrapods. [ABSTRACT FROM AUTHOR]

The effects of oxygen partial pressure ( $$ P_{{{\text{O}}_{2} }} $$) on development and respiration were investigated in the eggs of the Australian lungfish, Neoceratodus forsteri. At 20°C, embryonic survival and development was optimal at 15 and 20.9 kPa. Development was slowed at 5 and 10 kPa and embryos did not survive 2 kPa. At lower $$ P_{{{\text{O}}_{2} }} $$, the rate of oxygen consumption also decreased. Embryos responded to hypoxia by hatching at an earlier age and stage of development, and hatching wet and dry gut-free masses were reduced. The role of oxygen conductance ( $$ G_{{{\text{O}}_{2} }} $$) in gas exchange was also examined under selected environmental $$ P_{{{\text{O}}_{2} }} $$ and temperatures. The breakdown of the vitelline membrane changed capsule geometry, allowed water to be absorbed into the perivitelline space and increased capsule $$ G_{{{\text{O}}_{2} }} $$. This occurred at embryonic stage 32 under all treatments and was largely independent of both $$ P_{{{\text{O}}_{2} }} $$ and temperature (15, 20 and 25°C), demonstrating that capsule $$ G_{{{\text{O}}_{2} }} $$ cannot adaptively respond to altered environmental conditions. The membrane breakdown increased capsule diffusive $$ G_{{{\text{O}}_{2} }} $$ and stabilised perivitelline $$ P_{{{\text{O}}_{2} }} $$, but reduced the convective $$ G_{{{\text{O}}_{2} }} $$ of the perivitelline fluid, as the large perivitelline volume and inadequate convective current resulted in a $$ P_{{{\text{O}}_{2} }} $$ gradient within the egg prior to hatch. [ABSTRACT FROM AUTHOR]

A significant number of lungfish dentitions are now known from the Cretaceous (Cenomanian) Woodbine Formation, primarily from one new locality, the Arlington Archosaur Site of northeast Tarrant County, Texas. The Arlington Archosaur Site preserves a diverse coastal ecosystem within the interbedded coals, mudstones and sand lenses of a delta plain environment. The new lungfish specimens pertain to previously undescribed species from the Cenomanian. Previously recorded from but one specimen, this taxon is now represented by both prearticular and pterygopalatine dental plates of sectorial aspect. This species is similar to, and presumably descended from, one that has been previously recorded from various formations of Albian age. Measurements of the angles of the dental plate margins and crests confirm that it is distinct. Two small specimens appear to represent an earlier ontogenetic stage. Although dipnoan evolution generally appears to have proceeded slowly, the taxa from the Cretaceous (Albian -- Cenomanian) of Texas may possibly provide some stratigraphic indices, based on what is now known. The new Woodbine lungfish is herein referred to a new species; Ceratodus carteri. [ABSTRACT FROM AUTHOR]

Most Ceratodus specimens from the Aptian/Albian of north Texas belong to a small species that is characterized by distinctive sharp dental crests, denticulate in unworn tooth plates. These blade-like crests, indicative of a cutting and chopping dentition, distinguish this lineage from the crushing dentitions of most other North American Cretaceous dipnoans. This species is described and named herein as Ceratodus texanus. The functional adaptation of the dentition of this species (cutting/chopping) is indicative of predation on small invertebrates. The species is recorded from the Antlers Formation at Butler Farm (Wise County) and Greenwood Canyon (Montague County), and from the Twin Mountains Formation at the Jones Ranch Locality (Hood County). Although the natural history of dipnoans in the eastern North American subcontinent remains largely unknown, it is now certain that eastern lungfish populations, after formation of the central seaway, included lineages with crushing dentitions and lineages with sectorial dentitions. [ABSTRACT FROM AUTHOR]

The article presents a study which examined gene expression data for spatio-temporal order of tooth initiation for Scyliorhinus canicula, teleosts in both oral and pharyngeal dentitions and Neoceratodus forsteri. The patterning mechanism observed for the oral and pharyngeal dentition is found to be unique to the vertebrate oro-pharynx and independent of the skin system. It is concluded that co-option of a successful iterative pattern occurred in evolution from mechanism that exists in the oro-pharynx of extinct agnathans.

Abstract: There are no previous studies of the distribution of calbindin-D28k (CB) and calretinin (CR) in retinal neurons in lungfishes. The present study aimed to characterize the distribution of these neurons in a lepidosirenid lungfish (Protopterus dolloi) and a ceratodontid lungfish (Neoceratodus forsteri) using the same immunohistochemical protocol, with specific poly- and monoclonal antibodies, used in a previous comparative study of amphibians. The pattern for both proteins was similar in the two lungfishes studied, but some differences were also found. CB was found in photoreceptors, in subpopulations of bipolar and amacrine cells, and in horizontal and ganglion cells. Photoreceptors were negative for CR, whereas subpopulations of horizontal, bipolar, and amacrine cells contained CR, as did cells in the ganglion cell layer. Colocalization of CB/CR occurred in some cells of the inner nuclear layer. Tyrosine hydroxylase (TH) immunoreactivity colocalized with CB in some amacrine cells and, less frequently, with CR, but colocalization of TH with CB or CR in cholinergic cells was never found. Our data suggest a specific pattern for CB and CR distribution in the retinal neurons of lungfishes, a pattern that is highly comparable to that seen in amphibians, with unique features not observed in other vertebrates. [ABSTRACT FROM AUTHOR]

Werneburg, I. and Sánchez-Villagra, M.R. 2011. The early development of the echidna, Tachyglossus aculeatus (Mammalia: Monotremata), and patterns of mammalian development. - Acta Zoologica (Stockholm) : 75-88. The echidna is one of the last survivors of the most basal clade of living mammals and as such, it is an important species to understand character transformation in the dawn of mammalian evolution. Based on description of several embryological stages and consideration of characters taken from the classical drawings of Richard Semon (1859-1918), we study the early development of this species using the Standard Event System. We describe and analyse developmental timing with a phylogenetic approach (Parsimov). A mosaic of plesiomorphic and derived features - reportedly found in the echidna adult anatomy and genome, when compared to other living mammals - is also found when examining its embryonic development. In contrast to sauropsids, we found mammals to be characterized by late eye and ear development, possibly related to their contrasting early postnatal life history. The differentiation of the jaw bones may be reflected in the developmental timing of the mandibular process among mammals. Whereas in therians the mandibular process shows an accelerated development, in echidna a delayed timing of mandibular process characters is observable. We highlight the limitation of interpreting heterochronic data and expose the plasticity in the timing of developmental characters, examined under alternative phylogenetic frameworks and character definitions. [ABSTRACT FROM AUTHOR]

Much of Mesozoic diversity within the lungfishes (Osteichthyes: Dipnoi) has traditionally been relegated to the genus Ceratodus, primarily on the basis of the highly stereotypical dental plates characteristic of post-Devonian lungfishes. The new genus Potamoceratodus contains the single species P. guentheri (Marsh, 1878), comb. nov. Newly discovered material allows clarification of the features of this species, including description of a complete skull roof and partial palate. The new genus can be differentiated from the European Ceratodus on the basis of characters of the skull roof, palate, and dentition, including lack of tubercular ornamentation of the skull roof, modest convexity of the dorsal skull roof, absence of sensory sulci anteriorly in the EF bone, and an enlarged and elongate anterior odontode series on the pterygoid dental plate. The North American Ceratodus record is reexamined in light of more complete material from the Temple Canyon localities of the Morrison Formation of Colorado, USA. Ceratodus is found to be an assemblage of forms with disparate cranial morphology. The succession of North American lungfish communities in the late Paleozoic and Mesozoic is most characteristic of serial replacement rather than in situ evolution, and it is possible that the isolation of North America subsequent to the breakup of Laurentia contributed to the regional extinction of lungfishes in North America. [ABSTRACT FROM AUTHOR]

We describe herein the only known fossil dipnoans from Uruguay, recovered from continental deposits of Kimmeridgian-?early Cretaceous age (Batovi Member of the Tacuarembo Formation). The material includes several tooth plates referred herein to “Ceratodus” tiguidiensis Tabaste, 1963 (the current generic assignment being either Arganodus or Asiatoceratodus), and one to Ceratodus africanus Haug, 1905. “C.” tiguidiensis was so far only recorded in the Upper Jurassic-Lower Cretaceous of Saharan Africa and the 'middle' Cretaceous of Brazil (and perhaps the Lower Triassic of Australia), and C. africanus in the Lower to Upper Cretaceous of Saharan Africa and the 'middle' Cretaceous of Brazil. Hence, these are the oldest and southernmost South American records of both taxa, and the oldest and southernmost record of C. africanus in the world. These findings reveal an unrecognized dipnoan diversity in South America prior to 'middle' Cretaceous times. In the Late Jurassic-Early Cretaceous of western Gondwana only the ceratodontiform genera Ceratodus, Arganodus/Asiatoceratodus, and Retodus were present, Neoceratodus being absent. The Tacuarembo Formation paleoichthyofauna comprises a low-diversity freshwater assemblage including, besides dipnoans, putative semionotids (the most abundant fossils) and hybodontid sharks. [ABSTRACT FROM AUTHOR]

Lungfishes are currently considered the closest living relatives of tetrapods and represent an interesting group for the study of evolutionary traits in the transition from fishes to tetrapods. The brains of lungfishes have received little attention in comparative studies probably due to the difficulty of obtaining these unique animals. In the present study the distribution of orexin (hypocretin)-like immunoreactivity was studied in the brain of the African lungfish Protopterus dolloi and the Australian lungfish Neoceratodus forsteri by using antibodies directed against the mammalian orexin-A and orexin-B peptides. Simultaneous detection of orexins and tyrosine hydroxylase or serotonin was used to assess the precise location of the orexins in the brain and to evaluate the possible influence of the orexin system on the monoaminergic cell groups. Although some differences were noted, a common pattern for the distribution of orexins in the two lungfishes studied was observed. In both species, most immunoreactive neurons were observed in the suprachiasmatic nucleus and dorsal hypothalamus. Only in Neoceratodus, however, were important cell populations found in the preoptic area and infundibular hypothalamus, whereas small numbers of faintly reactive neurons were present in the lateral septum and ventral striatum. Fiber labeling was widely distributed in all main brain subdivisions, but was more abundant in regions such as the septum, preoptic area, suprachiasmatic nucleus, lateral hypothalamic area, thalamus, pretectum and tegmentum. Less conspicuous was the innervation of the pallial regions, habenula, optic tectum, rhombencephalic reticular formation and spinal cord. Orexinergic innervation was found in close contact with dopaminergic, noradrenergic and serotoninergic cell groups, homologous to the substantia nigra in the midbrain tegmentum, the locus coeruleus, the nucleus of the solitary tract and the raphe nuclei. Although unique features have been found for lungfishes, the location of orexin immunoreactive elements is largely consistent with that recently reported following a similar approach in amphibians and amniotes, suggesting that the general organization of this peptidergic system occurred in the common ancestor of lungfishes and tetrapods. Copyright © 2010 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Side biases in behavior, reflecting lateral specializations of the brain, are widespread amongst vertebrates. We studied laterality in the Australian lungfish (Neoceratodus forsteri) to gain insight into the evolution of the complementary specializations of predator avoidance (right hemisphere) and foraging behavior (left hemisphere). Because N. forsteri is the closest extant ancestor of the first land-dwelling vertebrates, knowledge of laterality in this species should provide a missing link in the transition from fish to tetrapods. Predator escape responses were elicited by generating pressure waves and a significant bias for C-start responses to the left side was found. This bias was unaffected by activity levels that change according to a diurnal cycle: activity is higher in the dark phase than the light phase. A complementary bias to turn to the right side was found during feeding behavior. This pattern of opposite-side specializations matches that known for fish, anurans, reptiles, birds and, as some evidence indicates, also mammals. Hence, we conclude that it is a homologous pattern of lateralization that evolved in early aquatic vertebrates and was retained as they made the transition to land-dwelling tetrapods. Copyright © 2009 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

The apical ectodermal ridge (AER) in Neoceratodus develops after an initial period of mesenchymal proliferation and outgrowth of the fin bud and persists until chondrogenesis of the stylopod and zeugopod is initiated. At this time, the lateral margins of the AER convert to the fin fold leading to subsequent development of the dermal fin skeleton. Thorogood's (1991 ) fin fold model predicts that the AER should persist longer in Neoceratodus than it does in actinopterygians because of the comparatively extensive endochondral skeleton in lungfish. While the AER does persist into early chondrogenesis and is extended compared to actinopterygians (lost before fin radial chondrogenesis) it does not persist into further stages of chondrogenesis, providing partial support for Thorogood's model. Fgf8 appears in the lungfish fin epithelium during the initial period of fin outgrowth before a physical AER forms, when Fgf8 is restricted to the AER plus the preaxial and postaxial epithelium immediately adjacent to the AER. Fgf8 is no longer detected after the AER is replaced by a fin fold. Neoceratodus appears to provide a halfway point between ray fins and limbs during very early development as Thorogood proposed, but not precisely for the reasons his model suggests. [ABSTRACT FROM AUTHOR]

The article presents a study which examines the prosencephalic neural folds (PNF) which produce neural crest (NC) cells in the Australian lungfish, Neoceratodus forsteri. After conducting experimental procedures on lungfish embryos, researchers found that lateral PNF (LPNF) derived neuroepithelium produces the basal layer and contributes to the apical layer of the olfactory placode. They also found that PNF-derived NC cells seem to give rise to menigeal, periocular and frontonasal ectomesenchyme and could infiltrate the olfactory placode as developmental precursors of the terminal nerve.

We report a temporal order of tooth addition in the Australian lungfish where timing of tooth induction is sequential in the same pattern as osteichthyans along the lower jaw. The order of tooth initiation in Neoceratodus starts from the midline tooth, together with left and right ones at jaw position 2, followed by 3 and then 1. This is the pattern order for dentary teeth of several teleosts and what we propose represents a stereotypic initiation pattern shared with all osteichthyans, including the living sister group to all tetrapods, the Australian lungfish. This is contrary to previous opinions that the lungfish dentition is otherwise derived and uniquely different. Sonic hedgehog (shh) expression is intensely focused on tooth positions at different times corresponding with their initiation order. This deployment of shh is required for lungfish tooth induction, as cyclopamine treatment results in complete loss of these teeth when applied before they develop. The temporal sequence of tooth initiation is possibly regulated by shh and is know to be required for dentition pattern in other osteichthyans, including cichlid fish and snakes. This reflects a shared developmental process with jawed vertebrates at the level of the tooth module but differs with the lack of replacement teeth. [ABSTRACT FROM AUTHOR]

Abstract: Cophylogenetic studies investigate the evolutionary trends within host-parasite associations. Examination of the different levels of fidelity between host and parasite phylogenies provides a powerful tool to inspect patterns and processes of parasite diversification over host evolution and geological times. Within the phylum Platyhelminthes, the monogeneans are mainly fish parasites. The Polystomatidae, however, are known from the sarcopterygian Australian lungfish and tetrapods such as amphibians, freshwater turtles, and the African hippopotamus. Cophylogenetic and biogeographic vicariance analyses, supplemented by molecular calibrations, showed that the Polystomatidae may track the evolutionary history of the first aquatic tetrapods in the Palaeozoic age. Evolutionary lines of the major polystome lineages would also be intimately related to the evolution of their hosts over hundreds of millions years. Since the Mesozoic, evolution of polystomes would have been shaped mainly by plate tectonics during the break-up of Gondwanaland and subsequent dispersal of ancestral neobatrachian host lineages. Therefore the Polystomatidae could serve as a novel model to improve cophylogenetic tools and to inspect a suite of questions about the evolution of vertebrate hosts. To cite this article: O. Verneau et al., C. R. Biologies 332 (2009). [Copyright &y& Elsevier]

The Australian lungfish, Neoceratodus forsteri, exists as remnant natural populations in two rivers of south-east Queensland, Australia, and several translocated populations. Lungfish habitats have been impacted by agriculture and forestry, alien plants and fish and by river impoundment and regulation of flows. The species has been listed as vulnerable under Australian Commonwealth legislation. A proposal to construct Traveston Crossing Dam on the free-flowing main channel of the upper Mary River could seriously threaten the lungfish. The dam can be stopped by Commonwealth legislation if important populations of lungfish in the Mary River are likely to be significantly impacted by the new dam. This paper assembles evidence that impoundment of the Mary River and regulation of river flows are likely to decrease and fragment important lungfish populations, disrupt the breeding cycle, reduce juvenile recruitment, and isolate and decrease habitat availability/quality to such an extent that the species is likely to decline. Proposed mitigation strategies include fish transfer facilities, provision of flow releases from the dam (environmental flows) to sustain lungfish habitat and breeding downstream, and translocation of hatchery-reared juvenile lungfish into suitable natural habitats. These mitigation efforts may not be sufficient to secure the genetic diversity and long-term viability of lungfish populations in the Mary River. [ABSTRACT FROM AUTHOR]

Abstract: The presence of nitric oxide synthase (NOS) and role of nitric oxide (NO) in vascular regulation was investigated in the Australian lungfish, Neoceratodus forsteri. No evidence was found for NOS in the endothelium of large and small blood vessels following processing for NADPH-diaphorase histochemistry. However, both NADPH-diaphorase histochemistry and neural NOS immunohistochemistry demonstrated a sparse network of nitrergic nerves in the dorsal aorta, hepatic artery, and branchial arteries, but there were no nitrergic nerves in small blood vessels in tissues. In contrast, nitrergic nerves were found in non-vascular tissues of the lung, gut and kidney. Dual-wire myography was used to determine if NO signalling occurred in the branchial artery of N. forsteri. Both SNP and SIN-1 had no effect on the pre-constricted branchial artery, but the particulate guanylyl cyclase (GC) activator, C-type natriuretic peptide, always caused vasodilation. Nicotine mediated a dilation that was not inhibited by the soluble GC inhibitor, ODQ, or the NOS inhibitor, L-NNA, but was blocked by the cyclooxygenase inhibitor, indomethacin. These data suggest that NO control of the branchial artery is lacking, but that prostaglandins could be endothelial relaxing factors in the vasculature of lungfish. [Copyright &y& Elsevier]

Experimental evidence that the neural crest participates in tooth development in any osteichthyan fish has so far been lacking. Using vital dye cell-lineage tracking, we demonstrate that trigeminal stream neural crest cells contribute to the dental papilla of developing teeth in the Australian lungfish. Trigeminal neural crest cells labeled before migration have been traced during the earliest stages of tooth development. Neural crest cells from a single midbrain locus were relocated as ectomesenchyme in all developing teeth of the lungfish regardless of their topographical position in the dentition. These cells remain at the dental papilla interface and become cells committed to dentine production. Our findings provide the first cell-lineage evidence that cranial neural crest is fated to ectomesenchyme for tooth development and dentine production in the living sister-group to tetrapods. This shows that cranial neural crest contribution to teeth is conserved from this node on the tetrapod phylogeny. [ABSTRACT FROM AUTHOR]

The Australian lungfish Neoceratodus forsteri (Dipnoi-Sarcoterygians) is a likely candidate for the extant sister group of Tetrapoda. Transmission electron and light microscopy analysis revealed that the arrangement of somite cells of the lungfish resembles the structure of the urodelan somite. On the other hand, the pattern of early muscle formation in N. forsteri is similar to that found in the Siberian sturgeon (Acipenser baeri). During the early stages of myogenesis of N. forsteri, somite-derived cells fuse to form multinucleated muscle lamellae. During later stages, mononucleated undifferentiated cells are first observed in the intermyotomal fissures and subsequently in the myotomes, among white muscle lamellae. The cells from the intermyotomal fissure differentiate into fibroblasts. The cells which have migrated into the myotomes, differentiate into mesenchyme-derived myoblasts. After hatching, white muscle lamellae are successively converted into polygonal muscle fibres. Conversion of lamellae into fibres may occur through splitting of muscle lamellae, or cylindrical muscle fibres may arise de novo as a result of fusion of mesenchyme-derived myoblasts. No increase in the number of muscle fibre nuclei is observed either in embryonic or juvenile musculature of N. forsteri. We suggest that until the 53 stage of embryonic development, the increase in muscle mass is accomplished mainly through hyperplasy. Thus, lungfish muscle represents the organizational intermediate between fishes and amphibians. This makes it a useful model to study the evolutionary implications of the mechanisms of muscle development. [ABSTRACT FROM AUTHOR]

The anatomy, histology and ultrastructure of the thymus of a dipnoan, the Australian lungfish, Neoceratodus forsteri, was studied by light and transmission electron microscopy. The thymic tissue showed clear demarcation into a cortex and medulla with ample vascularization. Large cells including foamy and giant multinucleated cells with periodic acid Schiff/Alcian blue positive staining properties were localized mainly in the medulla. The major cellular components were epithelial cells and lymphoid cells. The epithelial cells were classified by location and ultrastructure into six sub-populations: capsular cells, cortical and medullary reticular cells, perivascular endothelial cells, intermediate cells, nurse-like cells and Hassall-like corpuscles. Myoid cells were found mainly in the cortico-medullary boundary and medulla. Macrophages and secretory-like cells were also present. These findings will provide a base of knowledge about the cellular immune system of lungfish. [ABSTRACT FROM AUTHOR]

Abstract: The permanent tooth plates of the Australian lungfish, Neoceratodus forsteri, are covered by enamel that develops initially in a similar manner to that of other vertebrates. As the enamel layer matures, it acquires several unusual characteristics. It has radially oriented protoprismatic structures with the long axes of the protoprisms perpendicular to the enamel surface. Protoprisms can be defined as aggregations of hydroxyapatite crystals that lack the highly ordered arrangement of the rods of mammalian enamel but are not without a specific structure of their own. The protoprisms are arranged in layers of variable thickness that are deposited sequentially as the tooth plate grows. They may be confined to the separate layers, or may cross the boundary between each layer. Crystals within the protoprisms are long and thin with hydroxyapatite c-axis dimensions of between 30 and 350nm, and with typical a–b axis dimensions of 5–10nm. The hydroxyapatite crystals of lungfish enamel have no centre dark lines of octacalcium phosphate, an unusual character among vertebrates. As each crystal develops, arrays of atoms may change direction, and regions exist where dislocations and extra lattice planes are inserted into the long crystal. The resulting hydroxyapatite crystal is not straight, and has a rough surface. The crystals are arranged in tangled structures with their crystallographic c-axes closely aligned with the long axis of the protoprism. Lungfish enamel differs from the enamel of higher vertebrates in that the hydroxyapatite crystals are of different shape, and, in mature enamel, the protoprisms remain as protoprisms and do not develop into the conventional prismatic structures characteristic of mammalian enamel. [Copyright &y& Elsevier]

Abstract: Lobe-finned fish, particularly lungfish, are thought of as the closest extant relatives to tetrapods. Albumin, the major vertebrate plasma protein, has been well studied in tetrapods, but there exists no comparative study of the presence and characteristics of albumin in lobe-finned fish versus other vertebrates. There is a controversy over the presence of albumin in fish, although it is present in salmonids and lamprey. The presence of albumin in lungfish has also recently been documented. We identified albumin in plasma of the Australian lungfish, Neoceratodus forsteri, using a combination of agarose gel electrophoresis, [14C]palmitic acid binding and SDS-PAGE. Lungfish albumin was purified using DEAE-ion exchange chromatography, and has a mass of 67 kDa, is present at approximately 8 g/L in plasma and like other fish albumins, does not bind nickel. However, like tetrapod albumins, it is not glycosylated. N-terminal and internal peptide sequencing generated 101 amino acids of sequence, which showed a high degree of identity with tetrapod albumins. Despite the similarity in sequence but congruent with the evolutionary distances separating them, lungfish albumin did not cross-react with anti-chicken or anti-tuatara A albumin antisera. Lungfish albumin has characteristics more akin with tetrapod albumin and less like those of other fish. [Copyright &y& Elsevier]

Abstract: The Australian lungfish, Neoceratodus forsteri, has a dentition consisting of enamel, mantle dentine and bone, enclosing circumdenteonal, core and interdenteonal dentines. Branching processes from cells that produce interdenteonal dentine leave the cell surface at different angles, with collagen fibrils aligned parallel to the long axis of each process. In the interdenteonal dentine, crystals of calcium hydroxyapatite form within fibrils of collagen, and grow within a matrix of non-collagenous protein. Crystals are aligned parallel to the cell process, as are the original collagen fibrils. Because the processes are angled to the cell surface, the crystals within the core or interdenteonal dentine are arranged in bundles set at angles to each other. Apatite crystals in circumdenteonal dentine are finer and denser than those of the interdenteonal dentine, and form outside the fibrils of collagen. In mature circumdenteonal dentine the crystals of circumdenteonal dentine form a dense tangled mass, linked to interdenteonal dentine by isolated crystals. The functional lungfish tooth plate contains prisms of large apatite crystals in the interdenteonal dentine and masses of fine tangled crystals around each denteon. This confers mechanical strength on a structure with little enamel that is subjected to heavy wear. [Copyright &y& Elsevier]

This work presents characterisation of deiodinase type III (D3) mRNA as cDNA and the tissue distribution of D3 mRNA in the Australian lungfish, Neoceratodus forsteri. We have identified the full length of a ∼1.4 kb D3 mRNA in the liver, which has a single in-frame UGA codon and a selenocysteine insertion sequence (SECIS) form 2 in the 3′-UTR. Lungfish D3 mRNA was expressed in all tested tissues (liver, lung, kidney, brain, heart, and gills) as demonstrated by Northern blot analyses. PCR conducted on genomic DNA indicated that the lungfish D3 is a single exon gene. Also, we present enzymatic characteristics of this exclusively IRD enzyme, have determined its substrate preference, DTT cofactor requirements, PTU inhibition, and kinetic properties. These results indicate that lungfish D3 has the typical enzymatic characteristics of vertebrate D3 enzymes. [Copyright &y& Elsevier]

Deiodinase type II metabolises the prohormone T4 (thyroxine) into the biologically active hormone T3 (3,5,3′-triiodothyronine), at the cellular level in extrathyroidal target tissues. In juvenile lungfish, Neoceratodus forsteri, a typical deiodinase type II is present in most tissues. We have identified the full length of a 1.8 kb deiodinase type II mRNA in liver, and a truncated (1.3 kb) version in brain. Both mRNAs have two in frame UGA codons, but only the liver form has a predicted SECIS structure (form 1) in its 3′-UTR. We also report the presence of additional different length transcripts of deiodinase II mRNA, i.e., 3, 4, and 8 kb, in liver, and 8 kb in kidney, heart, and gill tissues. Expression of the longer (∼8 kb) transcript is very low. Real-time PCR confirmed the low expression of transcripts in all tissues, suggested by the Northern blot analysis. [Copyright &y& Elsevier]

Summary: Several anomalies occur in the developing neural and visceral head skeleton of young specimens of Neoceratodus forsteri that have been reared under laboratory conditions. These include anomalies of the basicranium and its derivatives, aberrations of the anterior mandible and hyoid apparatus, and abnormalities in the articulation of the jaws and the elements that produce them. Apart from the occasional absence of the basihyal, and failure of the quadrate processes to form, the anomalies are not deficiencies. Most involve malformations of parts of the neurocranium and visceral skeleton, inappropriate articulations or fusions between elements, disunity in structures that are normally fused and the appearance of supernumerary elements. The incidence of chondral anomalies, generally higher than aberrations that occur in the dermal skeleton in juvenile lungfish, range from 1–10% in laboratory reared individuals that have not been subjected to experimental interference. The anomalies differ from those found in many amphibian populations, in the field and in the laboratory, because they involve the cranium, and not the limbs, and the lungfish have not been exposed to the factors that cause anomalies in the amphibians. It is unlikely that the existence of those anomalies, if it is reflected in the wild population, places a selective pressure on the lungfish, because, in a normal season, less than 1% of the total number of eggs produced survive to be recruited into the adult population. [Copyright &y& Elsevier]