Kin discrimination in the social lizard Egernia saxatilis (Scincidae)

The ability to discriminate kin from nonkin is critical forthe evolution of kin-based sociality. Black rock skinks, Egerniasaxatilis, are viviparous lizards that typically live in "nuclearfamilies" consisting of an adult male, adult female, and oneor more cohorts of juveniles. Laboratory trials showed thatjuvenile lizards can discriminate between the scent of adultsfrom their own social group versus that of unfamiliar adults.Experiments in which we translocated individuals among familygroups revealed that this discriminatory ability was based onfamiliarity with other individuals rather than genetic relatedness.For example, neither "fostered" juveniles nor their mothersdisplayed any scent-based kin discrimination when brought togetherafter 2 months' separation. Thus, unlike the closely related(and also social) Egernia striolata, black rock skinks basekin discrimination on familiarity rather than genotypic similarity.     

The allantoplacenta of Mabuya mabouya (Sauria, Scincidae)

Analysis of placentation in the final stages of development in Mabuya mabouya shows that the placenta is formed by the apposition of the chorioallantois to the uterine mucosa implicating the entire embryonic chamber, because the allantoic vesicle invades all the exocoelom. The chorioallantoic placenta presents the features proper of a type IV allantoplacenta. However, in the mesometrial area peripheral to the placentome, we found that the paraplacentome is an additional zone specialized for histotrophic transfer, and is separated from the rest of the embryonic chamber by a chorionic invagination formed of polymorphic cells. The chorionic areolae are components of the embryonic hemisphere; they are in apposition to an endometrium with columnar epithelial cells and several glands that secrete toward the cavity of the areolae. They are observed only in the preparturition stage, probably operating in maternal-fetal transfer of nutrients during the last embryonic growth stage. The mesometrial hemisphere possesses specializations related to histotrophic nutrition (placentome, paraplacentome, and chorionic areolae), while in the abembryonic hemisphere there is an allantoplacenta of mixed function, with capacity for histotrophic nutrition and for gas exchange. The absorptive plaques are small rounded areas constituted by chorionic cells similar to the paraplacentomal chorionic cells, in intimate apposition with a secretory uterine epithelium. Separating the absorptive plaques are respiratory segments histologically similar to the type I allantoplacenta. The additional histotrophic areas found for this species demonstrate the great specialization of this allantoplacenta, and support the highest degree of matrotrophy among reptiles reached in the Neotropical Mabuya.     

Structure and histochemical organization of the spleen of Agama stellio (Sauria: Agamidae) and Chalcides ocellatus (Sauria: Scincidae)

The spleen of Agama stellio is composed mainly of red pulp; the white pulp is poorly developed, and its clusters are scattered throughout the organ and contain lymphocytes, reticular cells, and some plasma cells. The red pulp consists of clear reticular cells intermingled with blood cells, sinusoids, and pigment cells. The spleen of Chalcides ocellatus is encapsulated by connective tissue and is composed of white and red pulp. The white pulp consists of lymphoid tissue that surrounds the central arterioles, forming the periarteriolar lymphocyte sheath (PALS). The red pulp is composed of a system of venous sinuses and cords. The results of various histochemical procedures designed to demonstrate mucosubstances, proteins, and nucleic acids indicate that the spleen in these species resembles the mammalian spleen. © 1993 Wiley-Liss, Inc.     

Lizards in 'nuclear families': a novel reptilian social system in Egernia saxatilis (Scincidae)

Recent research has revealed unsuspected complexity in social organization among squamate reptiles. In particular, large Australian scincid lizards of the genus Egernia have been reported to occur in large aggregations of closely related individuals. However, the 'nuclear family' structure found in many other 'social' organisms (especially birds) has not been reported from reptiles. Our field studies on black rock skinks (Egernia saxatilis) in southeastern Australia document exactly this pattern. We quantified group composition using behavioural observations at regular intervals over three field seasons, and took tissue samples for parentage analysis. On the focal rock outcrop 72% of lizards were typically found as part of a stable social grouping, with individuals physically associated with other group members in a third of observations. Eighty-five per cent of juveniles lived in social groups, 65% in family groups with at least one of their parents (including 39% with both parents as revealed by parentage analysis of five microsatellite loci). Broader sampling in surrounding areas revealed similar patterns of group size, composition and relatedness. Overall, of the groups that contained more than one adult, 83% contained a single adult pair. Long-term monogamy and group stability were evident from our genetic data, with up to three annual cohorts of full-sib offspring living with their biological parents. Our data expand the range of social systems known for reptiles, and reveal strong convergence towards 'nuclear family' systems in distantly related vertebrates.     

Molecular systematics of social skinks: phylogeny and taxonomy of the Egernia group (Reptilia: Scincidae)

The lizards of the Egernia group of Australia and Melanesia include some of the most distinctive members of the family Scincidae in morphology (including giant size, spinose scalation), ecology and behaviour. Social behaviour, including long‐term recognition of individuals and kin, mate fidelity and home site fidelity, is amongst the most complex known in squamate reptiles and is the subject of an expanding number of studies. Lack of a sound phylogeny for the Egernia group has limited our ability to understand the evolution and patterns of variation in social behaviour within this group, and evidence for the monophyly of the largest genus, Egernia (64% of the species), has been lacking. We present data derived from nucleotide sequences that establish a phylogenetic framework for the Egernia group. We used two mitochondrial sequences, the protein‐encoding ND4 gene and a ribosomal gene, 12s rRNA, and two nuclear sequences, the protein‐encoding c‐mos, and non‐encoding intron 7 of β‐fibrinogen. Our phylogenetic analyses show that Corucia of the Solomon Islands is the sister group of the rest of the Egernia group. The genus Egernia is paraphyletic, including four well‐supported monophyletic units, one of which is the sister lineage of the Tiliqua lineage (Tiliqua plus Cyclodomorphus). We suggest a revised taxonomic scheme that recognizes the major monophyletic lineages in Egernia (s.l.) as distinct genera. © 2008 The Linnean Society of London, Zoological Journal of the Linnean Society, 2008, 154 , 781–794.     

Chromosomes of Australian lygosomine skinks (Lacertilia: Scincidae)

The karyotypes of 25 species from the scincid genera Egernia, Corucia and Tiliqua have been investigated using C-banding, silver staining of nucleolar organiser regions (NORs) and Hoechst 33258 induced condensation inhibition. At least one member from each of the species groups of Egernia recognised by Storr et al. (1981) was studied. The three genera have very similar conventionally stained karyotypes of 32 chromosomes. Some species show departures from this basic karyotype but these are due to additions of C-band positive material. Silver stained. NOR patterns are variable but most species have a silver staining site on a pair of larger microchromosomes. All specimens studied except one have a proximal C-band on the acrocentric ninth pair, which shows failure to condense following treatment with the fluorochrome Hoechst 33258. Heterogamety was not observed in any species. Mabuya multifasciata, proposed as a relative of the Egernia group, while having 32 chromosomes does not share the C-band marker on pair nine, unique to the Egernia group. Tribolonotus gracilis, sometimes allied with the Egernia group, has 32 chromosomes and a similiar karyotype, but prominent procentric C-bands on all chromosome pairs obscure the detection of the proximal C-band marker on pair nine.     

Molecular evolution of satellite DNA repeats and speciation of lizards of the genus Darevskia (Sauria: Lacertidae).

Satellite DNA repeats were studied in Caucasian populations of 18 rock lizard species of the genus Darevskia. Four subfamilies (Caucasian Lacerta satellites (CLsat)I-IV) were identified, which shared 70%-75% sequence similarity. The distribution of CLsat subfamilies among the species was studied. All the species could be divided into at least 3 clades, depending on the content of CLsat subfamilies in each genome: "saxicola", "rudis", and "mixta" lizards. CLsatI was found in all studied species, but in very different quantities; the "saxicola" group contained this subfamily predominantly. The "rudis" group also contained CLsatIII, and the "mixta" group carried considerable amounts of CLsatII. The highest concentrations of CLsatI and CLsatII were detected in 2 ground lizards--D. derjugini and D. praticola, respectively. D. parvula predominantly carried CLsatIII. CLsatIV was found only in the Crimean species D. lindholmi. The distribution patterns of satellite subfamilies show possible postglacial speciation within the genus Darevskia. A hybrid origin of species that possess 2 or 3 CLsat subfamilies and important clarifications to the systematics of the genus are proposed.     

Phylogenetic relationships and evolutionary history of snake-eyed skink Ablepharus kitaibelii (Sauria: Scincidae)

Sequence data derived from two mitochondrial markers, 16S rRNA and cytochrome b genes, were used to infer the phylogenetic relationships of 38 populations of the snake-eyed skinks of the genus Ablepharus with emphasis on A. kitaibelii from Greece and Turkey. The partition-homogeneity tests indicated that the combined data set was homogeneous, and maximum-parsimony, maximum-likelihood, and Bayesian analyses produced topologically identical trees that revealed a well-resolved phylogeny. All species except A. kitaibelii form monophyletic units. The latter species appears paraphyletic with respect to A. budaki and A. chernovi with populations clustering into two distinct clades. A. chernovi and A. budaki, which have recently been raised to species status, were confirmed as genetically distinct forms. We used sequence divergence and paleogeographic history of the Aegean region to reconstruct a biogeographic evolutionary scenario for A. kitaibelii.     

Molecular phylogeography and systematics of the arid-zone members of the Egernia whitii (Lacertilia: Scincidae) species group

We assembled a molecular phylogeny for the arid-zone members of the Egernia whitii species group to test Pianka's [Zoogeography and speciation of Australian desert lizards: an ecological perspective, Copeia (1972) 127-145] hypothesis that habitat specificity to the three major arid-zone vegetation communities is the primary cause of lizard speciation within the arid interior of Australia. This hypothesis predicts that species should exhibit phylogeographic structuring concordant with the major arid-zone vegetation types. Sequence data were obtained from four of the five arid-zone members of the E. whitii species group, and from across the ranges of the ecologically generalized E. inornata and E. multiscutata and the more specialized E. striata. We targeted a fragment (696 base pair (bp)) of the mitochondrial genome comprising the 3' half of the ND4 gene. We analysed the data using parsimony, maximum likelihood and Bayesian methods. Our phylogeny confirms the monophyly of the arid-zone members of the species group, although the phylogenetic relationships among species were not fully resolved. Although our topology does not support the recognition of the existing subspecies within E. multiscutata, there is a substantial phylogeographic break between South Australian/Victorian (Clade 1) and Western Australian (Clade 2) populations. We found considerable phylogeographic structure within E. inornata, with six major clades identified. However, these clades were not concordant with the distribution of habitat types in the arid-zone. Phylogeographic structure was also observed in the more specialized E. striata, although our analysis revealed close phylogenetic affinities between the sympatric species E. striata and E. kintorei. Shimodaira-Hasegawa topology tests were equivocal in regard to whether the phylogeographic structure within E. striata was in accordance with Pianka's predictions. Although our data failed to provide strong support for the suggestion that ecological and habitat factors are responsible for the diversification of arid-zone lizards, most E. inornata and E. striata populations had similar habitats, indicating that adaptation to particular habitats may have some role in the speciation of lizards in the Australian arid-zone.     

Polymorphism in the sperm ultrastructure among four species of lizards in the genus Tupinambis (Squamata: Teiidae)

We describe, for the first time, the ultrastructure of the spermatozoa of four species of the genus Tupinambis (Squamata, Teiidae). We identified seven polymorphic characters within this genus: the presence and shape of the perforatorial base plate, the presence of the epinuclear lucent zone, the presence of a unilateral ridge in the acrosome, the presence of a central density within the proximal centriole, the number of mitochondria and dense-bodies sets, and the shape of mitochondria. We analysed the evolution of the seven polymorphic characters by mapping them onto a current phylogeny of the species of Tupinambis , using the teiids Ameiva ameiva and Cnemidophorus sexlineatus as outgroups. Our results indicate that sperm ultrastucture characters, although of great value for phylogeny at higher taxonomic levels in reptiles and other groups, are poor predictors of phylogeny when considering the species of Tupinambis studied here. We failed to identify evidences that homoplasy in sperm ultrastructure among the species of Tupinambis is due to convergent adaptation, suggesting that the polymorphism may be selectively neutral in this group.     

Two malaria parasites (Apicomplexa: Plasmodiidae) of the Australian skink Egernia stokesii

The Australian skink Egernia stokesii is parasitized uncommonly by Plasmodium circularis n. sp. and by Plasmodium mackerrasae. Plasmodium circularis is distinguished from all other plasmodiids by immature schizonts that encircle host cell nuclei, forming an unbroken ring from apparent fusion of the attenuated ends. Mature schizonts contract into halteridial or dumbbell-shaped forms 15.6 x 4.3 microm, LW 66.2 microm2, with 19-52 nuclei. Rounded or oval gametocytes are 9.0 x 7.3 microm, LW 66.9 microm2, and L/W 1.24. Gametocyte LW is 2.63 x host erythrocyte nucleus size and 1.79X uninfected erythrocyte nuclei. Plasmodium mackerrasae occurs in high prevalence and often massive parasitemia in E. stokesii. Schizonts, often oblong, elongate, or oval, are 5.1 x 3.7 microm, LW 19.8 microm2, with 7.2 merozoites. Immature gametocytes, elongate with terminal nucleus, may produce multiple infections of 6 or more parasites. Mature gametocytes, usually rounded, are 5.8 x 4.6 microm, LW 26.7 microm2, and L/W 1.29. Gametocyte size is 0.98 x host erythrocyte nucleus size and 1.03 x uninfected erythrocyte nuclei. Phanerozoites, in endothelium or connective tissue of most organs, may appear in large numbers in circulating blood as seemingly intact bodies of regular form, similar to or larger than phanerozoites seen in sections. Previously unreported phenomena for hemosporidian parasites include extremely large, highly irregular exoerythrocytic schizonts, in circulating blood, perhaps torn from endothelial lining of blood vessels and sinuses, and a visible flooding of free merozoites into the blood stream.     

Convergent body flattening in a clade of tropical rock-using lizards (Scincidae: Lygosominae)

The repeated occurrence of similar morphologies in organisms from similar habitats provides good evidence of convergent selection, and convergent patterns of evolutionary change. In lizards, a flattened morphology has often been noted; however, whether this trait is convergent in specific habitats has never been tested using phylogenetic methods. The present study examined patterns of morphological convergence in 18 species of tropical Lygosomine skinks from three broad habitat categories (generalist, leaf litter-dwelling, and rock-using species). In general, although there where relatively few morphological differences of species from different habitats, phylogenetic analyses revealed that rock-using species have consistently and repeatedly evolved a dorsoventrally flattened head and body. The adaptive basis of this flattened morphology is consistent with both biomechanical predictions of performance (e.g. climbing locomotion) and ecology (e.g. use of rock crevices, camouflage) of species that occupy rocky habitats.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 94 , 399–411.     

The karyotypes of two scincid lizards,and their bearing on relationships in genus Leiolopisma and its relatives (Scincidae: Lygosominae)

Abstract

The karyotypes of the skinks Leiolopisma telfairi (Desjardin) and Cyclodina oliveri (McCann) are presented for the first time, from male spceimens. Metaphase cells from intestinal epithelium (C. oliveri) and testicular material (C. oliveri and L. telfairi) gave the diploid number, 2n = 30, for both species. Heteromorphism of the pair 6 chromosomes was observed in C. oliveri; this is the first published report of male heterogamety in the Scincidae. A common origin is proposed for L. spenceri and L. telfairi, on the basis of chromosome pair 8 morphology. These species may be more closely allied to Cyclodina than previously believed.     

The genus Paragehyra (Reptilia: Sauria: Gekkonidae) in southern Madagascar

Paragehyra Angel is a gekkonine genus endemic to Madagascar. From 1929 until the present, the genus was represented only by the holotype of the single known species. Paragehyra petiti. The type locality of P. petiti is in the driest part of Madagascar (south-west) where rainless periods may exceed 11 months and the original vegetation consists of thorn scrub or dry deciduous forest. No new individuals of P. petiti were observed. However, a second, undescribed species of the genus was discovered in October 1990 on the opposite side of the island (south-east) in primary-low montane rainforest. The new form was observed at four localities at the southernmost extremity of rainforest in Madagascar.     

Phylogenetic relationships and limb loss in sub-Saharan African scincine lizards (Squamata: Scincidae)

Skinks are the largest family of lizards and are found worldwide in a diversity of habitats. One of the larger and more poorly studied groups of skinks includes members of the subfamily Scincinae distributed in sub-Saharan Africa. Sub-Saharan African scincines are one of the many groups of lizards that show limb reduction and loss, and the genus Scelotes offers an excellent opportunity to look at limb loss in a phylogenetic context. Phylogenetic relationships were reconstructed for a total of 52 taxa representing all subfamilies of skinks as well as other Autarchoglossan families using sequence from six gene regions including; 12S, 16S, and cytochrome b (mitochondrial), as well as alpha-Enolase, 18S, and C-mos (nuclear). The family Scincidae is recovered as monophyletic and is the sister taxon to a (Cordylidae+Xantusiidae) clade. Within skinks the subfamily Acontinae is monophyletic and sister group to all remaining skinks. There is no support for the monophyly of the subfamilies Lygosominae and Scincinae, but sub-Saharan African scincines+Feylinia form a well supported monophyletic group. The monophyly of Scelotes is confirmed, and support is found for two geographic groups within the genus. Reconstructions of ancestral states for limb and digital characters show limited support for the reversal or gain of both digits and limbs, but conservative interpretation of the results suggest that limb loss is common, occurring multiple times throughout evolutionary history, and is most likely not reversible.     

Yolk sac development in lizards (Lacertilia: Scincidae): New perspectives on the egg of amniotes

Embryos of oviparous reptiles develop on the surface of a large mass of yolk, which they metabolize to become relatively large hatchlings. Access to the yolk is provided by tissues growing outward from the embryo to cover the surface of the yolk. A key feature of yolk sac development is a dedicated blood vascular system to communicate with the embryo. The best known model for yolk sac development and function of oviparous amniotes is based on numerous studies of birds, primarily domestic chickens. In this model, the vascular yolk sac forms the perimeter of the large yolk mass and is lined by a specialized epithelium, which takes up, processes and transports yolk nutrients to the yolk sac blood vessels. Studies of lizard yolk sac development, dating to more than 100 years ago, report characteristics inconsistent with this model. We compared development of the yolk sac from oviposition to near hatching in embryonic series of three species of oviparous scincid lizards to consider congruence with the pattern described for birds. Our findings reinforce results of prior studies indicating that squamate reptiles mobilize and metabolize the large yolk reserves in their eggs through a process unknown in other amniotes. Development of the yolk sac of lizards differs from birds in four primary characteristics, migration of mesoderm, proliferation of endoderm, vascular development and cellular diversity within the yolk sac cavity. Notably, all of the yolk is incorporated into cells relatively early in development and endodermal cells within the yolk sac cavity align along blood vessels which course throughout the yolk sac cavity. The pattern of uptake of yolk by endodermal cells indicates that the mechanism of yolk metabolism differs between lizards and birds and that the evolution of a fundamental characteristic of embryonic nutrition diverged in these two lineages. Attributes of the yolk sac of squamates reveal the existence of phylogenetic diversity among amniote lineages and raise new questions concerning the evolution of the amniotic egg. J. Morphol. 278:574–591, 2017. © 2017 Wiley Periodicals, Inc.