Placental ontogeny of the Tasmanian scincid lizard, Niveoscincus ocellatus (Reptilia: Squamata)

A prominent scenario for the evolution of reptilian placentation infers that placentotrophy arose by gradual modification of a simple vascular chorioallantoic placenta to a complex structure with a specialized region for nutrient transfer. The structure of the chorioallantoic placenta of Niveoscincus ocellatus, apparently described originally from a single embryonic stage, was interpreted as a transitional evolutionary type that provided support for the model. Recently, N. ocellatus has been found to be as placentotrophic as species with complex chorioallantoic placentae containing a specialized region called a placentome. We studied placental development in N. ocellatus and confirmed that the chorioallantoic placenta lacks specializations found in species with a placentome. We also found that this species has a specialized omphaloplacenta. The chorioallantoic placenta is confined to the region adjacent to the embryo by a membrane, similar to that found in some other viviparous skinks, that divides the egg into embryonic and abembryonic hemispheres. We term this structure the "inter-omphalopleuric" membrane. The position of this membrane in N. ocellatus is closer to the embryonic pole of the egg than to the abembryonic pole and thus the surface area of the omphaloplacenta is greater than that of the chorioallantoic placenta. In addition, the omphaloplacenta is regionally diversified and more complex histologically than the chorioallantoic placenta. An impressive and unusual feature of the omphaloplacenta of N. ocellatus is the development of extensive overlapping folds in the embryonic component of mid-gestation embryos. The histological complexity and extensive folding of the omphaloplacenta make this a likely site of placental transfer of nutrients in this species.     

Functional morphology of prey capture in the sturgeon,Scaphirhynchus albus

Acipenseriformes (sturgeon and paddlefish) are basal actinopterygians with a highly derived cranial morphology that is characterized by an anatomical independence of the jaws from the neurocranium. We examined the morphological and kinematic basis of prey capture in the Acipenseriform fish Scaphirhynchus albus, the pallid sturgeon. Feeding pallid sturgeon were filmed in lateral and ventral views and movement of cranial elements was measured from video sequences. Sturgeon feed by creating an anterior to posterior wave of cranial expansion resulting in prey movement through the mouth. The kinematics of S. albus resemble those of other aquatic vertebrates: maximum hyoid depression follows maximum gape by an average of 15 ms and maximum opercular abduction follows maximum hyoid depression by an average of 57 ms. Neurocranial rotation was not a part of prey capture kinematics in S. albus, but was observed in another sturgeon species, Acipenser medirostris. Acipenseriformes have a novel jaw protrusion mechanism, which converts rostral rotation of the hyomandibula into ventral protrusion of the jaw joint. The relationship between jaw protrusion and jaw opening in sturgeon typically resembles that of elasmobranchs, with peak upper jaw protrusion occurring after peak gape.     

An unusual lizard (Reptilia: Squamata) from the Early Cretaceous of Las Hoyas, Spain

The Early Cretaceous (Barremian) lepidosaurian assemblage of Las Hoyas (Cuenca Province, Castilla-La Mancha), Spain, resembles that of roughly contemporaneous localities at Montsec (Catalonia), Una (Castilla-La Mancha) and Galve (Aragon) in being dominated by the scincomorph lizard Meyasaums ( Ilerdaesaurus ). It differs in the presence of two previously unknown taxa, one of which, described here, shows a strikingly unusual morphology in its ribs and distal limb skeleton suggestive of climbing specialization. This form is sufficiently distinct from other known taxa to warrant the erection of a new genus and species, Scandensia ciervensis gen. et sp. nov. Cladistic analysis of Scandensia suggests that it forms a sister taxon to living squamates (Iguania + Scleroglossa and all descendants of their most recent common ancestor).     

Kinematics of prey capture in the tailed frog Ascaphus truei (Anura: Ascaphidae)

The kinematics of prey capture by Ascaphus truei was investigated. High-speed films (100 fps) of 13 successful and one unsuccessful prey capture sequences from six adult frogs were analysed. Ascaphus , the sister group of all living frogs, shares several aspects of feeding kinematics, including rotation of the tongue pad about the mandibular symphysis and mandibular bending during mouth opening and closing, with more derived frogs such as Bufo marinus. The times required for tongue retraction, mouth opening and closing are similar in Ascaphus and Bufo. However, because Bufo is much larger and protracts its tongue much farther than Ascaphus , the velocities of tongue retraction, mouth opening and mouth closing are relatively lower in Ascaphus than in Bufo. Differences in prey capture between Ascaphus and Bufo marinus are (1) the distance of tongue protraction is less in Ascaphus (±0.5 cm) than in Bufo (c. 2 cm); and (2) lunging of the whole body is more pronounced in Ascaphus. Prey capture is highly variable in Ascaphus. An intraoral transport sequence is sometimes (7 of 14 observations) inserted into the prey capture cycle before the completion of mouth closing. The gape cycles range from 80–150 ms for sequences with no oral transport and from 130–280 ms for sequences with oral transport. Also, the time required for tongue retraction is significantly longer in the unsuccessful capture attempt. This variability is generally greater than that observed during prey capture in salamanders, and suggests that frogs and salamanders may differ in the importance of sensory feedback in coordinating prey capture.     

Lack of spermatogenic variation in a polymorphic lizard,Sceloporus aeneus (Squamata: Phrynosomatidae)

Although different mechanisms exist to explain the presence of polymorphism in lizards, one model suggests that multiple morphotypes display the same level of fitness. Three male morphs (grey, yellow and orange) coexist in Sceloporus aeneus, a Mexican endemic oviparous lizard. Using a histological perspective, we test the hypothesis that spermatogenic output does not vary across morphotypes of S. aeneus during its maximum testicular activity. Males of S. aeneus (five grey, five yellow and five orange) were collected in Calimaya, Estado de México, Mexico. Snout-vent length (SVL), testis mass, diameter and epithelial heights for the seminiferous tubules and epididymis, and the number of layers of germ cells did not vary among morphs; moreover, according to principal component analysis, a high overlap among lateral colour morphs exists. Our results suggest strongly that the lateral colour morphs in S. aeneus have the same spermatogenic output, and natural selection may be a stronger driving force than sexual selection within this species. Further studies into other lizard species with multiple morphotypes are required to determine whether the lack of variation in spermatogenic output observed in this endemic lizard is consistent across polymorphic species which will provide a greater understanding of the selective mechanisms acting on an individual’s fitness.     

Functional morphology of tongue projection in Taricha torosa (Urodela: Salamandridae)

The kinematics of tongue projection by terrestrial adult California newts, Taricha torosa (Rathke, 1833), are described based upon high-speed cinematography. Tongue projection results from coupled anterior movements of the ceratohyals and branchial arches. Four distinct periods are defined during a projection sequence: preparation, tongue projection, tongue recovery and mouth closing. Key anatomical correlates of projection are described, with special emphasis on the mobility of the hyoid arch. Adult Taricha (Gray, 1850) have lost the mandibulo-hyoid ligament and reduced additional connective tissues present in larvae. These changes decouple the hyoid arch from mouth opening and release the ceratohyals to participate in a tongue projection system distinct from those of ambystomatids and plethodontids. These phylogenetic differences pose questions about the evolution of tongue projection systems in terrestrial urodeles. Currently available data are consistent with the interpretation that terrestrial urodeles have independently evolved specialized tongue projection systems at least twice: the ceratohyal-stable mode of plethodontids and the ceratohyal-mobile system of newts. In all cases, an essential underlying (= plesiomorphic) feature is the presence of the depressor mandibulae muscle. We regard this pathway for mouth opening as a prerequisite which liberated the hyobranchium for alternative function. Comprehensive studies of the mandibulo-hyoid ligament and depressor mandibulae will be vital to modelling the evolution of specialized tongue projection systems of urodeles.     

Chromosomal variation in the scincid genus Mabuya and its arboreal relatives (Reptilia: Squamata)

Karyotypes of four East and Southeast Asian species of the genus Mabuya and representatives of three arboreal genera considered to be closely related to the genus (Apterygodon, Dasia and Lamprolepis) are examined. Mabuya rugifera and M. rudis possess 2n=32 karyotypes, whereas M. longicaudata lacks one small chromosome pair, which makes its diploid number 30. The karyotype of M. macularia quadrifasciata from southern Thailand differs from any known scincid karyotypes, including a previously reported karyotype of the conspecific Indian population, in exhibiting a high diploid number (38) and a gradual change in size from large to small chromosomes. This suggests that M. macularia may consist of more than one biological species. Karyotypes of Apterygodon vittatus, Dasia olivacea and Lamprolepis smaragdinus, while exhibiting a close similarity to most Mabuya karyotypes, suggest the occurrence of slight rearrangements involving either the deletion of two small chromosome pairs (A. vittatus), or the change of centromeric positions in medium and small chromosomes (D. olivacea and L. smaragdinus).     

Linking cranial morphology to prey capture kinematics in three cleaner wrasses: Labroides dimidiatus,Larabicus quadrilineatus,and Thalassoma lutescens

Cleaner fishes are well known for removing and consuming ectoparasites off other taxa. Observers have noted that cleaners continuously “pick” ectoparasites from the bodies of their respective client organisms, but little is known about the kinematics of cleaning. While a recent study described the jaw morphology of cleaners as having small jaw‐closing muscles and weak bite forces, it is unknown how these traits translate into jaw movements during feeding to capture and remove ectoparasites embedded in their clients. Here, we describe cranial morphology and kinematic patterns of feeding for three species of cleaner wrasses. Through high‐speed videography of cleaner fishes feeding in two experimental treatments, we document prey capture kinematic profiles for Labroides dimidiatus, Larabicus quadrilineatus, and Thalassoma lutescens. Our results indicate that cleaning in labrids may be associated with the ability to perform low‐displacement, fast jaw movements that allow for rapid and multiple gape cycles on individually targeted items. Finally, while the feeding kinematics of cleaners show notable similarities to those of “picker” cyprinodontiforms, we find key differences in the timing of events. In fact, cleaners generally seem to be able to capture prey twice as fast as cyprinodontiforms. We thus suggest that the kinematic patterns exhibited by cleaners are indicative of picking behavior, but that “pickers” may be more kinematically diverse than previously thought. J. Morphol. 276:1377–1391, 2015. © 2015 Wiley Periodicals, Inc.     

Energetic costs of prey ingestion in a scincid lizard,Scincella lateralis

Summary The relative importance of aerobic and anaerobic metabolism during feeding was investigated in the ground skink, Scincella lateralis. Animals were fed crickets of three different sizes relative to body mass (5, 10, and 15% of body mass). Oxygen consumption and lactic acid production of animals during feeding were compared with those of animals at rest and when exercising intensely. Oxygen consumption was higher in feeding and exercising animals than in those at rest. Rates of oxygen consumption of animals consuming prey of 5 and 10% of body mass were not significantly different from each other, but were lower than rates of animals consuming prey of 15% of body mass. Lactic acid concentrations in feeding animals increased with increasing prey size. Concentrations in resting and feeding animals were not different, but those of exercising animals were significantly higher. These data suggest that, despite a positive correlation between prey size and lactic acid concentration, anaerobiosis is relatively unimportant in the support of prey handling for Scincella lateralis. The energetic requirements of feeding in this species are met largely by increased aerobic metabolism.     

Spermiogenesis in the imbricate alligator lizard,Barisia imbricata (Reptilia,Squamata, Anguidae)

Although the events of spermiogenesis are commonly studied in amniotes, the amount of research available for Squamata is lacking. Many studies have described the morphological characteristics of mature spermatozoa in squamates, but few detail the ultrastructural changes that occur during spermiogenesis. This study's purpose is to gain a better understanding of the subcellular events of spermatid development within the Imbricate Alligator Lizard, Barisia imbricata. The morphological data presented here represent the first complete ultrastructural study of spermiogenesis within the family Anguidae. Samples of testes from four specimens collected on the northwest side of the Nevado de Toluca, México, were prepared using standard techniques for transmission electron microscopy. Many of the ultrastructural changes occurring during spermiogenesis within B. imbricata are similar to that of other squamates (i.e., early acrosome formation, chromatin condensation, flagella formation, annulus present, and a prominent manchette). However, there are a few unique characteristics within B. imbricata spermatids that to date have not been described during spermiogenesis in other squamates. For example, penetration of the acrosomal granule into the subacrosomal space to form the basal plate of the perforatorium during round spermatid development, the clover‐shaped morphology of the developing nuclear fossa of the flagellum, and the bulbous shape to the perforatorium are all unique to the Imbricate Alligator Lizard. These anatomical character differences may be valuable nontraditional data that along with more traditional matrices (such as DNA sequences and gross morphological data) may help elucidate phylogenetic relationships, which are historically considered controversial within Squamata. J. Morphol., 2013. © 2013 Wiley Periodicals, Inc.     

The mesopneumonia and the post-hepatic septum of the Teiioidea (Reptilia: Squamata)

Klein, W., Böhme, W. and Perry, S. F. 2000. The mesopneumonia and the post‐hepatic septum of the Teiioidea (Reptilia: Squamata). —Acta Zoologica (Stockholm) 81 : 109–119 This study investigates the structure of the pleuroperitoneal cavity of Teiioidea. Seven of nine genera of Teiidae and eight of 35 genera of Gymnophthalmidae were dissected and the results are presented in a highly schematic two‐dimensional representation. The main anatomical differences between the two families are (1) the presence of a hepatic ligament which fuses with the pericardiaco‐peritoneal septum in the Gymnophthalmidae but not in the Teiidae; (2) the presence of a ventral mesopneumonium on the right side in the Gymnophthalmidae, while this structure is secondarily lacking in the Teiidae; (3) that the post‐hepatic septum of Teiidae consists of a bipartite hepatic ligament and the ventral mesentery, while in gymnophthalmids the hepatic ligament remains undivided. Neusticurus and Echinosaura completely lack a post‐hepatic septum. The results are consistent with the hypothesis that the Gymnophthalmidae are primitive within the Teiioidea and that the Tupinambinae are the most highly derived teiids. We propose that the post‐hepatic septum may restrict passive visceral movement during breathing, thereby increasing the efficiency of respiratory effort; a modification that could benefit the fitness of active, predatory teiids.     

Determinants of breeding dispersal in the sand lizard, Lacerta agilis, (Reptilia, Squamata)

We studied determinants of breeding dispersal (the distance that an animal shifts its mean home range co-ordinate between reproductive events) in an individually marked population of sand lizards (Lacerta agilis) in south west Sweden during 1987–1991. Female breeding dispersal was not determined by age, size, body condition, or number of partners, and females and males that dispersed further did not experience a higher mortality. However, females with a low reproductive output dispersed further than females that reproduced more successfully, and males that lost in bodily condition dispersed further than males that better maintained body condition. We also looked for relationships between age-differences and band-sharing similarity (DNA fingerprinting = DFP) in three categories of lizards — all females, all males, and males and females — to establish whether males would be likely to mate with close kin. Age-difference was strongly correlated with band-sharing in only one category, males and females. When males were older than females this relationship was not significant. However, when females were older than males, age-difference was strongly correlated with band-sharing. Furthermore, females that were old enough to be the mothers of the courting males shared significantly more bands with these males than did the younger females, including the females of the same age as the males. Although parental-specific DFP bands necessary for establishing paternity among our adult lizards were inaccessible to us, we suggest that our circumstantial evidence strongly suggests that some males mate with their mothers. Males that were more closely related with their neighbours also moved further when we controlled statistically for age and mating success. We suggest that by mating with many partners males not only increase their mating success, but also increase the probability of mating with females with ‘good genes’: mean heterozygosity of parents (as revealed by micro-satellites) were strongly correlated with offspring survival.     

Structure of shells of eggs of Callisaurus draconoides (Reptilia, Squamata, Iguanidae)

Female zebra-tailed lizards (Iguanidae: Callisaurus draconoides ) lay roughly ovoid eggs with thin, highly extensible shells. The outer surface of the eggshell is a thin, calcareous crust of calcium carbonate in the calcite morph. Immediately beneath the crystalline matrix is a shell membrane composed of multiple layers of fibres organized into an undulating series of troughs and crests, apparent in both cross-section and surface view. The outer surface of the shell membrane is differentiated into a tightly woven fibrous mat that may serve to anchor the calcareous layer to the membrane. Organization of the eggshell into a series of troughs and crests serves to increase the surface area available for contact with the substrate and, presumably, to increase the capacity of the eggshell to stretch as the egg absorbs water.     

Renal sexual segment of the ground skink, Scincella laterale (Reptilia, Squamata, Scincidae)

Mature squamates possess hypertrophied regions of the distal urinary ducts, the renal sexual segment (RSS). The RSS is believed to provide seminal fluid that mixes with sperm and is released into the female cloaca during coitus. This study is the first to describe ultrastructure of the RSS in a lizard collected throughout the active season. The species examined, Scincella laterale, represents the largest family (Scincidae: 1,200 species) of lizards. Although sperm are present in the posterior ductus deferens of male S. laterale throughout the year, an annual spermatogenic cycle occurs that results in spermiation in spring, coinciding with maximum development of the RSS. Female S. laterale may possess stored sperm in vaginal crypts from March-May and large oviductal eggs April-June. Thus, the correlation between mating and RSS activity observed in other squamates is also found in S. laterale. Cytologically, the active RSS consists of columnar cells with numerous apical, electron-dense secretory vacuoles which are released by an apocrine process. The granules stain positively for proteins with bromphenol blue and react with PAS for neutral carbohydrates. After the mating season the RSS undergoes recrudescence and the electron-dense granules are replaced by a mucoid secretion that characterizes more proximal portions of the nephric tubules throughout the year. Little variation in ultrastructure of the RSS occurs between S. laterale and Cnemidophorus lemniscatus (Teiidae), the only other lizard in which seasonal variation of the RSS has been studied using similar methods. Females exhibit differentiation similar to that of males in the distal urinary tubules, but to a lesser degree. This is only the second such report for female squamates, and the differentiation of the region in females is proposed to result from adrenal androgens.     

Structure of the posthepatic septum and its influence on visceral topology in the tegu lizard, Tupinambis merianae (Teiidae: Reptilia)

The posthepatic septum (PHS) divides the body cavity of Tupinambis merianae into two parts: the cranial one containing the lungs and liver and the caudal one containing the remaining viscera. The PHS is composed of layers of collagenous fibers and bundles of smooth muscle, neither of which show systematic orientation, as well as isolated blood vessels, lymphatic vessels, and nerves. Striated muscle of the abdominal wall does not invade the PHS. The contractions of the smooth muscles may stabilize the pleurohepatic cavity under conditions of elevated aerobic needs rather than supporting breathing on a breath-by-breath basis. Surgical removal of the PHS changes the anatomical arrangement of the viscera significantly, with stomach and intestine invading the former pleurohepatic cavity and reducing the space for the lungs. Thus, the PHS is essential to maintain the visceral topography in Tupinambis.     

Coloration affects heating and cooling in three color morphs of the Australian bluetongue lizard,Tiliqua scincoides

The color-mediated thermoregulation hypothesis predicts that dark body color (low reflectance) allows organisms to gain heat more efficiently than does pale coloration (high reflectance). This prediction is intuitive and widely assumed to be true, but has poor empirical support. We used rare, captive-bred, mutant melanistic, albino and wild-type Australian bluetongue lizards, Tiliqua scincoides to measure the effects of skin reflectance on the heating and cooling rates. We measured heating under an artificial radiant heat source and cooling rates in an ice-cooled box using live lizards in a room with still air. The effect of skin reflectance on heat transfer was clear, despite the substantial influence of body size. Melanistic T. scincoides showed low reflectance and gained heat faster than highly reflective albinos. Melanistic lizards also lost heat faster than albinos. Wild-type lizards were intermediate in reflectance, gained heat at rates indistinguishable from melanistic lizards, and lost heat at rates indistinguishable from albino lizards. This study system allowed us to control for variables that were confounded in other studies and may explain the inconsistent support for the color-mediated thermoregulation hypothesis. Our results provide clear evidence that skin reflectance influences the rate of heating and cooling in ectotherms.