The language of lizards: interpreting the function of visual displays of the Indian rock lizard, Psammophilus dorsalis (Agamidae)

The first step in understanding any communication system is to document signal diversity relative to the context of signalling (e.g. sex of the signaller and audience). Observation of 30 free-ranging rock lizards (Psammophilus dorsalis) on rock outcrops in southern India over a period of 18 months revealed that these lizards produce a complex array of ritualized signals involving push-ups (head-bobbing), dorsal flattening, extension of the legs or gular region, and tail-raising. Push-ups were performed by both sexes, usually after moving from one location to another. Push-ups were rarely accompanied by other postural modifications, and seem to function as non-directed signals. Dorsal flattening was elicited by birds flying overhead, and seems to make the lizard less conspicuous to predators. There was, nonetheless, a strong sex difference in the frequency of this behaviour, because the habitats used by males (open rocks) exposed them to more birds. Males displayed to females by extending their gular folds and arching their backs; other animals (e.g. squirrels, monkeys) also elicited the latter posture from both sexes. Leg extension was observed for both males and females, but in different contexts—males in response to conspecifics, females in response to other animals. Females raised their tails in response to encountering a male. Thus, these lizards have a complex repertoire of postures for predator evasion, for interaction with other species and with conspecifics, and for communicating sex-specific social information about gender (tail-raise) or dominance status (gular extension, leg extension).     

Influence of gaze and directness of approach on the escape responses of the Indian rock lizard, Psammophilus dorsalis (Gray, 1831)

Animals often evaluate the degree of risk posed by a predator and respond accordingly. Since many predators orient their eyes towards prey while attacking, predator gaze and directness of approach could serve as conspicuous indicators of risk to prey. The ability to perceive these cues and discriminate between high and low predation risk should benefit prey species through both higher survival and decreased energy expenditure. We experimentally examined whether Indian rock lizards (Psammophilus dorsalis) can perceive these two indicators of predation risk by measuring the variation in their fleeing behaviour in response to type of gaze and approach by a human predator. Overall, we found that the gaze and approach of the predator influenced flight initiation distance, which also varied with attributes of the prey (i.e. size/sex and tail-raise behaviour). Flight initiation distance (FID) was 43% longer during direct approaches with direct gaze compared with tangential approaches with averted gaze. In further, exploratory, analyses, we found that FID was 23% shorter for adult male lizards than for female or young male (FYM) lizards. In addition, FYM lizards that showed a tail-raise display during approach had a 71% longer FID than those that did not. Our results suggest that multiple factors influence the decision to flee in animals. Further studies are needed to test the generality of these factors and to investigate the proximate mechanisms underlying flight decisions.     

Sperm storage within the oviduct of turtles

Tubules containing sperm were identified by light microscopy in the oviducts from 11 species of turtles representing six different families. Sperm storage tubules were found in a small region of the posterior portion of the egg albumin-secreting section of the oviduct located between the infundibulum and the uterus. This location of storage tubules, midway between the ovary and vagina, is unique among vertebrates. Ducts, restricted to the posterior albumin region, connect the tubules to the oviduct lumen, allow entrance of sperm to the tubules. Sperm were identified in tubules of female turtles isolated from males for as long as 423 days.     

Sperm transfer and storage in the lizard,Anolis carolinensis

The relationship of the hemipenis to the cloaca in copula and sperm storage and transport in the female oviduct were studied in Anolis carolinensis using light and scanning electron microscopy. During copulation, the hemipenis does not penetrate beyond the cloaca, but the two apical openings of the bifurcate sulcus spermaticus appose the openings of the oviducts from the cloaca. Sperm enter the sperm storage tubules between 2 and 6 hr after insemination and small amounts of sperm reach the infundibulum 6 to 24 hr following mating. Sperm storage tubules are embedded in the wall of the utero-vaginal transition, and are formed by the folding and fusion of the oviducal epithelium. The importance of the hemipenile-cloacal relationship and the role of sperm storage in the life history of A. carolinensis are discussed.     

Sperm storage in the oviduct of the American alligator

Oviducts of the American alligator (Alligator mississippiensis) were examined histologically for the presence of stored sperm. Two regions containing sperm were identified, one at the junction of the posterior uterus and the vagina (UVJ) and the other at the junction of the tube and isthmus (TIJ). In these areas, sperm were found in the lumina of oviductal glands. The glands in these areas of the oviduct are diffuse and shallow and appear to allow better access to sperm than glands located elsewhere. Histochemically, the glands of the UVJ reacted weakly for carbohydrates and proteins, whereas those of the TIJ reacted strongly for these same two components, secretions of which are associated with sperm storage structures in other reptiles. Sperm were not in contact with the glandular epithelium, and glands at the UVJ contained more sperm than those at the TIJ. Oviductal sperm storage was observed not only in recently mated females but in all females possessing uterine eggs as well as all females known to be associated with a nest. We conclude that female alligators are capable of storing sperm in their oviductal glands, but not from one year to the next.     

Sperm capacitation in the porcine oviduct

In vitro studies suggests that sperm capacitation occurs in the sperm reservoir (SR) of the pig, with spermatozoa progressing towards the ampullary-isthmic junction (AIJ) around ovulation as a consequence of capacitation/hyperactivation. In contrast, in vivo studies are scarce. Consequently, we determined the degree of capacitation in boar spermatozoa that were retrieved from the SR of sows at well-defined periods of spontaneous standing oestrus, namely pre-, peri- and post-ovulation, using flow cytometry of Merocyanine-540/Yo-Pro-1-loaded spermatozoa. SR-spermatozoa retrieved and incubated in non-capacitating medium (bicarbonate-free mBO [mBO-]) were largely viable (70-85%) and uncapacitated (69-73%), irrespective of the stage of oestrus considered. Those undergoing capacitation were a minor proportion (1-5%) during pre- and peri-ovulation, but they significantly increased (14%) in post-ovulation oestrus. To clarify whether these SR-spermatozoa were able to undergo capacitation under stimuli, sperm aliquots were challenged in vitro either by incubation in a bicarbonate-rich medium (capacitation medium, mBO+), then further in mBO+ with 20% (v/v) of in vivo collected homologous pre-ovulatory isthmic oviductal fluid (IOF), or incubation with hyaluronan (HA, 500 microg/ml). Exposure to mBO+ significantly increased the sub-population of capacitated spermatozoa from the pre- and peri-ovulation SR, indicating that the uncapacitated SR-spermatozoa were responsive to the effector/inducer bicarbonate at levels recorded in peri-ovulatory AIJ/ampulla in vivo. While addition of IOF or HA to SR-spermatozoa incubated in capacitating medium (mBO+) maintained sperm viability without obviously inducing capacitation in pre- or peri-ovulatory SR-spermatozoa, they significantly increased these percentages during post-ovulation, when compared to baseline values of control incubations (mBO-). The results suggest that massive sperm capacitation does not occur in vivo in the porcine SR under spontaneous standing oestrus, particularly during pre- and peri-ovulation, unless spermatozoa are exposed to the effector bicarbonate. Exposure to IOF (and its component HA) under the present experimental conditions, reversed bicarbonate influence during pre- and peri-ovulation and further increased capacitation in post-ovulation, calling for an active role of the intratubal fluid. Furthermore, HA appears to have an active role in the functionality of the SR.     

Seasonal study of apoptotic markers in lizard oviduct

Lizard oviduct is a very dynamic organ that undergoes high tissue remodelling as a function of the cyclic reproductive activity. Until today there are no studies of molecular actors involved in cell death in the lizard oviduct. Therefore, this report is focused on some of apoptotic markers responsible of programmed cell death in this organ during the main significant phases of reproductive cycle. Apoptotic cell recognition was based on the estimation of known following markers: cleaved caspase-9 and-3; tissue transglutaminase (tTG) and DNA fragmentation. By Western blotting, expected band sizes of 29 and 17?kDa, recognizing the anti-caspase-9 and caspase-3, respectively, showed a stronger expression during the ovulation and postovulation. Enzymatic activity of caspase-9 shows the highest value at ovulation, whereas that of caspase-3 is recorded at postovulation. The expression and the activation of tTG protein are in line with the fragmentation of DNA. No tTG positive cells are detected at quiescence, when either no TdT-mediated dUTP-biotin nick end labeling (TUNEL)-positive nuclei or DNA fragmentation is observed. At this time tTG activity is at a minimum. Indeed, a consistent DNA smear is observed from the DNA extracted at postovulation, when tTG activity reached its maximum and several transglutaminase immunoreactivity cells and TUNEL positive nuclei are observed. The temporal and dynamic outlines of apoptotic parameters match with seasonal modifications of the oviduct. Taken together, our results demonstrate that the seasonal apoptotic activity of the oviduct represents a key process in the remodelling of this tissue during the reproductive cycle.     

Day-night variations in blood and intracellular pH in a lizard,Dipsosaurus dorsalis

Blood pH, PCO2 and PO2 of Dipsosaurus dorsalis were measured during the day and at night. Lizards at constant body temperature (25, 37 degrees C) and lizards experiencing diurnal changes in body temperature similar to those in nature were studied. In lizards at constant body temperatures, blood pH was about 0.1 unit less and blood PCO2 was 4-7 Torr higher at night compared to day. Similar patterns were seen in lizards on natural thermal cycles. Intracellular pH (pHi) of skeletal muscle, esophagus and liver was about 0.2 units lower at night than day but myocardial pHi was unchanged. Reduction in breathing frequency, and thus a relative hypercapnia from hypoventilation was consistent with the nocturnal acidification of the blood and intracellular compartments. Nocturnal acidification (CO2 retention) corresponds to periods of minimum metabolism. The possible impacts of diurnal shifts in hydrogen ion concentration on energy metabolism and metabolic regulation are discussed.     

Histochemical determination of the fiber composition of locomotory muscles in a lizard, Dipsosaurus dorsalis

A histochemical survey was done on the fiber composition of 12 different locomotory muscles in the lizard Dipsosaurus dorsalis. Three types of fibers were found in all muscles: (1) fast-twitch-glycolytic (FG); (2) fast-twitch-oxidative-glycolytic (FOG); and (3) tonic fibers. Virtually all locomotory muscles contain some tonic fibers. Most muscles have bulk white regions (containing mostly FG fibers) and distinct red, oxidative regions (with FOG and tonic fibers). These red regions are predominantly located around the joints in the hind limb muscles, and probably serve a postural and joint-stabilizing function. The predominance of FG fibers in the bulk white regions is well-correlated with the rapid, anaerobically supported predator escape behavior of D. dosalis.     

Progesterone receptor in the liver and oviduct of the lizard Podarcis sicula

In this paper we report the presence of a (3)H-Progesterone ((3)H-P) binding moiety, which has the characteristics of a true receptor, in the liver of the female of the lizard Podarcis sicula. (3)H-P binding studies show the presence of one type of binding site with an average Kd value of 6.2 +/- 2.0 nM in the cytoplasm and 6.3 +/- 1.1 nM in the nucleus. Competition experiments showed that progesterone (P) was the best competitor, while testosterone, deoxycorticosterone (DOC), corticosterone, 17 alpha-hydroxyprogesterone; R5020; RU486 and RU26988-5 were poor competitors. We have also investigated the immunological characteristics of progesterone receptor (PR) in both the liver and the oviduct of Podarcis sicula, by Western blotting using the monoclonal antibody PR22 raised against the PR isoforms A and B of chicken. One imunoreactive band of about 70 kDa was detected in cytoplasmic and nuclear extracts of both the liver and the oviduct. PR immunoreactivity was present in the liver during the quiescent phase. In the oviduct PR immunoreactivity increased from the recovery to the full grown phase. P treatment of estrogen-primed females did not affect the presence of PR in the liver, while brought about a PR increase in the oviduct. This study suggests that PR is expressed differently in the liver and the oviduct of Podarcis sicula throughout the reproductive cycle. PR might fulfill different requirements in relation to the different physiological functions of the tissue during the reproductive cycle.     

Sperm storage in caecilian amphibians

Background

Female sperm storage has evolved independently multiple times among vertebrates to control reproduction in response to the environment. In internally fertilising amphibians, female salamanders store sperm in cloacal spermathecae, whereas among anurans sperm storage in oviducts is known only in tailed frogs. Facilitated through extensive field sampling following historical observations we tested for sperm storing structures in the female urogenital tract of fossorial, tropical caecilian amphibians.

Findings

In the oviparous Ichthyophis cf. kohtaoensis, aggregated sperm were present in a distinct region of the posterior oviduct but not in the cloaca in six out of seven vitellogenic females prior to oviposition. Spermatozoa were found most abundantly between the mucosal folds. In relation to the reproductive status decreased amounts of sperm were present in gravid females compared to pre-ovulatory females. Sperm were absent in females past oviposition.

Conclusions

Our findings indicate short-term oviductal sperm storage in the oviparous Ichthyophis cf. kohtaoensis. We assume that in female caecilians exhibiting high levels of parental investment sperm storage has evolved in order to optimally coordinate reproductive events and to increase fitness.     

Immunolocalization of Glucagon and Insulin Cells in Endocrine Pancreas and Cyclic Disparity of Plasma Glucose in the Lizard Psammophilus dorsalis

Reptiles are an interesting group to study the physiology of reproduction. As information on mobilisation of glucose and associated endocrine alterations in the pancreas are not known, a study on the lizard Psammophilus dorsalis was undertaken using immunohistochemistry. Glucagon-immunoreactive (IR) and insulin-IR cells never formed islets instead spread throughout the pancreas in P. dorsalis. Glucagon-IR cells appeared to release the secretory granules from all over the surface, insulin-IR cells are unidirectional in their secretion. Both cell types often have no direct contact with capillaries. The morphometric analysis showed that the glucagon-IR cells were the most abundant amounting approximately 63 % as against insulin-IR cells, amounting approximately to 37 % of the endocrine pancreatic mass in the present study. On an average P. dorsalis exhibited 288.3 ± 25.28 mg% of plasma glucose, the abdominal fat underwent clearance as there was energy demand during reproductive and recrudescent periods. Glycogen granules were evident in liver and this was inversely related with plasma glucose.     

蜂王体内的精子贮存

蜜蜂最重要的生殖特征是一雌多雄交配,蜂王交配后将精子贮存于受精囊中长达数年之久,并仍能保持活力。这些特征使蜜蜂成为研究精子长期贮存的模式动物。文章介绍蜂王的交配和精子贮存过程,精子贮存器官,贮存过程中的精子竞争和隐秘雌性选择,以及蜂王精子的长期贮存机制,并对将来的研究方向进行了展望。     

Behavioural flexibility and problem-solving in a tropical lizard

The role of behavioural flexibility in responding to new or changing environmental challenges is a central theme in cognitive ecology. Studies of behavioural flexibility have focused mostly on mammals and birds because theory predicts that behavioural flexibility is favoured in species or clades that exploit a diversity of habitats or food sources and/or have complex social structure, attributes not associated with ectothermic vertebrates. Here, we present the results of a series of experiments designed to test cognitive abilities across multiple cognitive modules in a tropical arboreal lizard: Anolis evermanni. This lizard shows behavioural flexibility across multiple cognitive tasks, including solving a novel motor task using multiple strategies and reversal learning, as well as rapid associative learning. This flexibility was unexpected because lizards are commonly believed to have limited cognitive abilities and highly stereotyped behaviour. Our findings indicate that the cognitive abilities of A. evermanni are comparable with those of some endothermic species that are recognized to be highly flexible, and strongly suggest a re-thinking of our understanding of the cognitive abilities of ectothermic tetrapods and of the factors favouring the evolution of behavioural flexibility.     

Regulation of sperm storage and movement in the mammalian oviduct

The oviduct plays a vital role in ensuring successful fertilization and normal early embryonic development. The male inseminates many thousands or even millions of sperm, but this alone does not ensure that fertilization will be successful. The female tract, particularly the oviduct, provides filters that select for normal vigorously motile sperm. In conjunction with molecules in the seminal plasma and on sperm, the female tract regulates how and when sperm pass though the tract to reach the site of fertilization. Various regulatory processes control sperm passage into and through the oviduct. In some species, the uterotubal junction opens and closes to regulate when sperm may enter; furthermore, passage through the junction requires certain proteins on the sperm surface. Most of the sperm that manage to enter the oviduct soon become trapped and held in a reservoir. In marsupials and insectivores, this involves trapping sperm in mucosal crypts; while in most other mammalian species, this involves binding sperm to the oviductal epithelium. As the time of ovulation approaches, the sperm in the reservoir undergo capacitation, including motility hyperactivation. Capacitating sperm shed proteins that bind them to the mucosal epithelium, while hyperactivation assists the sperm in pulling off of the epithelium and escaping out of mucosal pockets. The process of sperm release is gradual, reducing chances of polyspermic fertilization. Released sperm may be guided towards the oocyte by secretions of the oviduct, cumulus cells, or oocyte. Hyperactivation likely assists sperm in penetrating the cumulus matrix and is absolutely required for penetrating the oocyte zona pellucida and achieving fertilization.