Proopiomelanocortin (POMC) and testing the phylogenetic position of turtles (Testudines)

Alpha-melanocyte-stimulating hormone (alpha-MSH) is a neuropeptide expressed in pituitary and brain that is known to regulate energy balance, appetite control, and neuroimmune functions. The biosynthesis of alpha-MSH requires proteolytic processing of the proopiomelanocortin (POMC) precursor. Therefore, this study investigated the in vivo role of the prohormone convertase 2 (PC2) processing enzyme for production of alpha-MSH in PC2-deficient mice. Specific detection of alpha-MSH utilized radioimmunoassay (RIA) that does not crossreact with the POMC precursor, and which does not crossreact with other adrenocorticotropin hormone (ACTH) and beta-endorphin peptide products derived from POMC. alpha-MSH in PC2-deficient mice was essentially obliterated in pituitary, hypothalamus, cortex, and other brain regions (collectively), compared to wild-type controls. These results demonstrate the critical requirement of PC2 for the production of alpha-MSH. The absence of alpha-MSH was accompanied by accumulation of ACTH, ACTH-containing imtermediates, and POMC precursor. ACTH was increased in pituitary and hypothalamus of PC2-deficient mice, evaluated by RIA and reversed-phase high pressure liquid chromatography (RP-HPLC). Accumulation of ACTH demonstrates its role as a PC2 substrate that can be converted for alpha-MSH production. Further analyses of POMC-derived intermediates in pituitary, conducted by denaturing western blot conditions, showed accumulation of ACTH-containing intermediates in pituitaries of PC2-deficient mice, which implicate participation of such intermediates as PC2 substrates. Moreover, accumulation of POMC was observed in PC2-deficient mice by western blots with anti-ACTH and anti-beta-endorphin. In addition, increased beta-endorphin1-31 was observed in pituitary and hypothalamus of PC2-deficient mice, suggesting beta-endorphin1-31 as a substrate for PC2 in these tissues. Overall, these studies demonstrated that the PC2 processing enzyme is critical for the in vivo production of alpha-MSH in pituitary and brain.

The role of lipotropins as hematopoietic factors and their potential therapeutic use

Addressing sources of data deficiency for sea turtles and fisheries in the Indian Ocean and Southeast Asia

Examination of genetic polymorphisms in outbred wild-living species provides insights into the evolution of complex systems. In higher vertebrates, the proopiomelanocortin (POMC) precursor gives rise to α-, β-, and γ-melanocyte-stimulating hormones (MSH), which are involved in numerous physiological aspects. Genetic defects in POMC are linked to metabolic disorders in humans and animals. In the present study, we undertook an evolutionary genetic approach complemented with biochemistry to investigate the functional consequences of genetic polymorphisms in the POMC system of free-living outbred barn owl species (family Tytonidae) at the molecular level. Our phylogenetic studies revealed a striking correlation between a loss-of-function H9P mutation in the β-MSH receptor-binding motif and an extension of a poly-serine stretch in γ3-MSH to ≥7 residues that arose in the barn owl group 6–8 MYA ago. We found that extension of the poly-serine stretches in the γ-MSH locus affects POMC precursor processing, increasing γ3-MSH production at the expense of γ2-MSH and resulting in an overall reduction of γ-MSH signaling, which may be part of a negative feedback mechanism. Extension of the γ3-MSH poly-serine stretches ≥7 further markedly increases peptide hormone stability in plasma, which is conserved in humans, and is likely relevant to its endocrine function. In sum, our phylogenetic analysis of POMC in wild living owls uncovered a H9P β-MSH mutation subsequent to serine extension in γ3-MSH to 7 residues, which was then followed by further serine extension. The linked MSH mutations highlight the genetic plasticity enabled by the modular design of the POMC gene.

Summary “Protorosaurs” are a group of early archosauromorph reptiles (i.e. stem-archosaurs, the reptile clade containing modern birds and crocodylians). They are characterized by their long necks, which are comprised of elongate cervical vertebrae with low neural spines and long and thin cervical ribs. The group exhibits a high degree of morphological and ecological diversity, and is represented by terrestrial, fully marine, and possibly gliding taxa. As such they represent an important group for understanding the earliest evolution of the archosaur lineage as well as the composition of Triassic ecosystems in the aftermath of the Permo-Triassic mass extinction event. Well-known “protorosaurs” include the Permian Protorosaurus speneri, the Early Triassic Prolacerta broomi, and the Tanystropheidae. The most striking “protorosaurs” are the extremely long-necked Tanystropheus spp. and Dinocephalosaurus orientalis. Recent phylogenetic studies indicate that “Protorosauria” make up several lineages of non-archosauriform archosauromorphs, implying it is a polyphyletic group. This thesis is aimed at improving our understanding of this remarkable group of reptiles by investigating their morphology, taxonomy, biogeographic distribution patterns, palaeobiology, and phylogeny. A new specimen of Prolacerta broomi from the Antarctic Fremouw Formation provides new insights into its morphology and confirms that specimens of this taxon from Antarctica and South Africa belong to the same species, indicating the close faunal ties between these continents during the Early Triassic. The taxonomy of the genus Tanystropheus is reviewed and extensively revised. The number of Tanystropheus species is reduced from six to three. One species, Tanystropheus fossai, differs distinctly from other Tanystropheus species and is therefore reassigned to a separate genus, Sclerostropheus. Two other species, Tanystropheus longobardicus and the newly identified Tanystropheus hydroides are known from the famous Besano Formation of the UNESCO World Heritage Site of Monte San Giorgio. They were previously considered to represent juveniles and adults of the same species, respectively. However, distinct differences in their cranial morphology, supported by osteohistological evidence that the specimens of the smaller species T. longobardicus are skeletally mature, convincingly show that they represent separate species. The species have distinctly contrasting dentitions and thus exploited different food sources. Their co-occurrence in the Besano Formation therefore represents a convincing example of niche partitioning and reveals a surprisingly multifunctional role for the extremely long and stiff neck of Tanystropheus. The cranial morphology of both T. hydroides and Macrocnemus bassanii are studied in detail using high-resolution synchrotron radiation microtomography. This has allowed for the first comprehensive skull reconstructions of these taxa. They reveal much information on skull regions that were previously obscured such as the braincase and in the case of T. hydroides even the endocast and endosseous labyrinth. The skull of M. bassanii shows many plesiomorphic features, whereas the skull of T. hydroides is highly derived and clearly specialized for an aquatic lifestyle. The holotype of Macrocnemus fuyuanensis is redescribed and reveals additional characters that distinguish it from M. bassanii. This reveals that M. fuyuanensis occurred on both the eastern and western margins of the Tethys Ocean, since a specimen from the Besano Formation of Monte San Giorgio can be referred to this species, which is otherwise exclusively known from China. Finally, a new phylogenetic analysis comprising the most comprehensive sample of “protorosaur” taxa to date has been performed considering the new findings presented in this thesis. It confirms both the polyphyly of “Protorosauria” and the monophyly of Tanystropheidae. The position of the putative gliding reptile Ozimek volans within Tanystropheidae is corroborated. The analysis reveals that Prolacerta broomi is more distantly related to Archosauriformes (i.e. stem-archosaurs more closely related to the crown than non-archosauriform archosauromorphs) than previously considered. Additionally, a new clade of long-necked archosauromorphs, Dinocephalosauridae, is recognized, which is at least comprised of the Chinese taxa Dinocephalosaurus orientalis and Pectodens zhenyuensis.

Lamium is a taxonomically convoluted genus of about 34 species. Within Lamium, the L. garganicum species complex is particularly challenging. Here, based on morphological and molecular studies, Lamium cappadocicum Celep & Karaer sp. nova (Lamiaceae) is separated from L. garganicum and L. bilgilii and described as a new species, and L. garganicum subsp. rectum (= L. garganicum subsp. pulchrum) is resurrected. The new species is only known from the Hasan Mountain (Aksaray) in Central Anatolia, Turkey. Lamium cappadocicum is closely related to L. garganicum subsp. rectum but differs from it by its mat-forming caespitose habit, reniform (rarely ovate in upper part) and deeply cordate leaves with dense white villous hairs, deeply crenate and undulate leaf margins, subglabrous to sparsely pilose stems, and densely white villous calyces. Lamium cappadocicum also differs from L. bilgilii by its matforming caespitose habit, smaller corollas (25-33 mm versus 40-52 mm in L. bilgilii), subglabrous to sparsely pilose stems and smaller leaves (3-20 (-30) mm long × 3-20 (-30) mm wide, versus 5-45 mm long × 5-45 mm wide in L. bilgilii). Molecular phylogenetic analyses from nuclear ribosomal (nrITS) and chloroplast (matK, rpoA and psbA-trnH) gene regions support the morphological results. The IUCN conservation status, ecology, phenology, etymology, and notes on biogeography of the new species are also given and diagnostic features are discussed.

Is self-fertilization possible in nudibranchs?

Morphological studies in marine turtles might be used to obtain information about changes in developmental habitats. Information regarding mortality and growth rates can be obtained by collecting data on the size of nesting females on the nesting beach. Morphometric and meristic traits of female green turtles (Chelonia mydas) were recorded on Samandağ Beach, Turkey, during the 2006-2016 nesting seasons. The study aimed to determine the mean and minimum curved carapace length (CCL) of the nesting green turtle and the differences in body size and scute pattern over the years. The relationship between the body size of nesting green turtles and latitude was also analysed. CCL and curved carapace width (CCW) were recorded for 365 individuals and meristic measures were recorded for 292 individuals. The mean CCL and CCW were recorded as 86.9 (± 6.14) and 77.9 (± 5.95) cm, respectively. The minimum CCL of nesting green turtles was also recorded as 72 cm. The CCL and CCW showed differences over the years and they tended to become smaller from 2006 to 2016. However, this trend was not significant according to the Mann-Kendall trend test. The CCL value was negatively correlated with the latitude and rejected Bergmann's rule. There was no relationship between year and carapace scute deviation. The Samandağ green turtle population had the smallest nesting green turtle based on CCL. In addition to environmental factors, recruitment of females, and growth and mortality rates, and the nesting shift between nesting beaches may be some of the reasons behind a smaller value over the years.

The molecular genetics of the melanocortin pathway and energy homeostasis

Characterisation of ranaviral infection and its management in Australian lizards

Understanding stakeholder involvement in the policy and management of migratory taxa in the Australian marine environment: a case study approach

Hybridization is particularly important for evolutionary and speciation processes. It promotes evolutionary divergence between lineages by reinforcing reproductive isolation mechanisms to avoid the erosion of the spatial genetic structure and the production of unfit hybrids. Additionally, hybridization creates novel taxa by the fusion of interacting lineages. However, introgressive hybridization leads to conservation problems when introgression happens between threatened lineages and non-native or domesticated lineages. In such cases, introgressive hybridization may lead to the genetic swamping of one lineage and to the loss of the entire taxon. Hybrids often harbour novel genetic combinations and novel adaptations that provide them a higher potential to adapt to environmental changes and colonize new ecological niches. In the future, conservation of hybrids might provide additional genetic diversity for species to cope with alterations in their environment. In my thesis, I investigated hybridization and introgression between European pond turtle subspecies (Emys orbicularis) by combining nuclear microsatellites and mitochondrial cytochrome b gene: I reported that introgressive hybridization between pond turtle subspecies occured in natural and human-mediated contact zones. Outcomes of introgressive hybridization between European pond turtle (Emys orbicularis) subspecies indicated that E. o. orbicularis and E. o. hellenica subspecies and hybrids may have better fitness than E. o. galloitalica subspecies and hybrids under Swiss environmental conditions. Furthermore, I developed an eDNA-based methodology to detect the presence of pond turtles and investigated the efficiency of two water sampling methods. Finally, results of this thesis provided scientific knowledge to the Swiss national conservation programme of the European pond turtle.

The reptiles in compartment 15, 16 and 17 of Gunung Inas Forest Reserve, Kedah were investigated from January 2008 until December 2009. A total number of 19 species of lizards from 12 genera and four families, 20 species of snakes from 18 genera and seven families and six species of freshwater turtles from six genera and three families were recorded during the survey period. This study represented 10, 15 and 5 new records of lizards, snakes and freshwater turtles. Subsequently this data increased the number of lizards, snakes and freshwater turtles that inhabit Banjaran Bintang from 31 to 41, 30 to 45 and three to eight respectively.

Pro-opiomelanocortin (POMC) neurons in the arcuate nucleus (ARC) regulate energy homeostasis by secreting α-melanocyte-stimulating hormone (α-MSH), derived from POMC precursor, in response to leptin signalling. Expression of Pomc is subject to multiple modes of regulation, including epigenetic regulation. Methyl-CpG-binding protein 2 (MeCP2), a nuclear protein essential for neuronal function, interacts with promoters to influence gene expression. We aim to address whether MeCP2 regulates hypothalamic Pomc expression and to investigate the role of epigenetics, particularly DNA methylation, in this process. We generated a mouse line with MeCP2 specifically deleted in POMC neurons (Mecp2 flox/y /Pomc-Cre [PKO]) and characterised its metabolic phenotypes. We examined the DNA methylation pattern of the Pomc promoter and its impact on hypothalamic gene expression. We also studied the requirement of MeCP2 for, and the effects of, DNA methylation on Pomc promoter activity using luciferase assays. PKO mice are overweight, with increased fat mass resulting from increased food intake and respiratory exchange ratio. PKO mice also exhibit elevated plasma leptin. Deletion of MeCP2 in POMC neurons leads to increased DNA methylation of the hypothalamic Pomc promoter and reduced Pomc expression. Furthermore, in vitro studies show that hypermethylation of the Pomc promoter reduces its transcriptional activity and reveal a functional synergy between MeCP2 and cAMP responsive element binding protein 1 (CREB1) in positively regulating the Pomc promoter. Our results demonstrate that MeCP2 positively regulates Pomc expression in the hypothalamus. Absence of MeCP2 in POMC neurons leads to increased DNA methylation of the Pomc promoter, which, in turn, downregulates Pomc expression, leading to obesity in mice with an accentuating degree of leptin resistance.

Once semen has been collected for artificial insemination, it is diluted into extenders designed to prevent its deterioration over the period prior to insemination. If the semen is not frozen, the extenders provide protection for a period of a few hours to a few days, depending on species. Despite the efforts of biotechnologists to increase the duration of storage without compromising fertility, there has been relatively little progress for many years. However, comparative studies in diverse species have revealed that long-term sperm storage (up to months and years) within the female reproductive tract is relatively commonplace in reptiles, fishes, birds and amphibians. Even among mammals, some species of bat have evolved mechanisms for storing spermatozoa for several months in the uterus or oviduct so that they can mate in the autumn but postpone fertilization until the spring. We currently know little about the mechanisms that support such long-term sperm storage, mainly because evidence from such species is either absent or fragmentary. Nevertheless, parallels between mammalian and other systems, where spermatozoa are sequestered in sperm storage tubules, suggest that the enclosure of spermatozoa within pockets of epithelial cells may be sufficient to achieve long-term sperm storage. In addition, recent evidence from sperm-storing bats has suggested an alternative, or additional, hypothesis that the modulation of apoptosis within epithelial cells is important in controlling sperm survival. Despite a lack of direct experimental evidence from a wide variety of species, I propose that there is now enough evidence to warrant investigation of these hypotheses.