Sex determination and optimal development in the Moorish gecko,Tarentola mauritanica

Under temperature sex determination (TSD), sex is determined by temperature during embryonic development. Depending on ecological and physiological traits and plasticity, TSD species may face demographic collapse due to climate change. In this context, asymmetry in bilateral organisms can be used as a proxy for developmental instability and, therefore, deviations from optimal incubation conditions. Using Tarentola mauritanica gecko as a model, this study aimed first to confirm TSD, its pattern and pivotal temperature, and second to assess the local adaptation of TSD and variation of asymmetry patterns across four populations under different thermal regimes. Eggs were incubated at different temperatures, and hatchlings were sexed and measured. The number of lamellae was counted in adults and hatchlings. Results were compatible with a TSD pattern with males generated at low and females at high incubation temperatures. Estimated pivotal temperature coincided with the temperature producing lower embryonic mortality, evidencing selection towards balanced sex ratios. The temperature of oviposition was conservatively selected by gravid females. Asymmetry patterns found were likely related to nest temperature fluctuations. Overall, the rigidity of TSD may compromise reproductive success, and demographic stability in this species in case thermal nest choice becomes constrained by climate change.     

Lateralization in Escape Behaviour at Different Hierarchical Levels in a Gecko: Tarentola angustimentalis from Eastern Canary Islands

At the individual level, to be behaviourally lateralized avoids costly duplication of neural circuitry and decreases possible contradictory order from the two brain hemispheres. However, being prey behaviour lateralized at higher hierarchical levels could generate different negative implications, especially if predators are able to make predictions after multiple encounters. These conflicting pressures, namely between the advantages for individuals and the disadvantages for populations could be concealed if higher-level lateralization would arise from the combination of lateralized behaviours of individuals which are mutually dependent. Here, we investigated the lateralization patterns in the escape behaviour of the gecko Tarentola angustimentalis undergoing a predatory attack simulation in a “T” maze experiment. Results showed that gecko populations displayed different degrees of lateralization, with an overall dominance of right-biased individuals. This trend is similar to that observed in the Podarcis wall lizards, which share predators with Tarentola. In addition, different morphological parameters plausible to affect refuge selection were explored in order to link directional asymmetries at morphological level with lateralization during refuge selection.     

Evolutionary patterns of the mitochondrial genome in the Moorish gecko, Tarentola mauritanica

A previous study on the evolutionary patterns of Tarentola mauritanica demonstrated that low levels of mitochondrial diversity observed in the European populations relative to nuclear markers were consistent with a selective sweep hypothesis. In order to unravel the mitochondrial evolutionary history in this European population and two other lineages of T. mauritanica (Iberian and North African clades), variation within 22 nearly complete mitogenomes was analyzed. Surprisingly, each clade seems to have a distinct evolutionary history; with both the European and Iberian clades presenting a decrease of polymorphism, which in the former is consistent with departure from neutrality of the mtDNA (positive or background selection), but in the latter seems to be the result of a bottleneck after a population expansion. The pattern exhibited by the North African clade seems to be a consequence of adaptation to certain mtDNA variants by positive selection.     

Phylogenetic relationships of the populations of Iranolacerta brandtii (de Filippi, 1863) (Squamata: Lacertidae) recently found in Eastern Anatolia,Turkey

The Persian Lizard, Iranolacerta brandtii, was until recently considered to be restricted to north-western Iran (Azerbaijan and Esfahan provinces). However, two recent studies have revealed the existence of populations in Eastern Anatolia, extending the range of this species for about 230?km westwards. The fragmented distribution of this species has been considered to be a consequence of the climatic oscillations during the Pleistocene and Holocene, which created events of alternating contact and isolation of populations in distinct glacial refugia. According to our obtained genealogy derived from three mitochondrial fragments (12S rRNA, 16S rRNA and cytb), the Turkish specimens cluster together but form an independent clade, sister to the individuals from Tabriz in Iran. The separation of these two clades is concurrent with the cladogenesis between the Esfahan and Ardabil clades, estimated to have taken place during the late Holocene.     

Molecular mechanisms beyond glucose transport in diabetes-related male infertility

Diabetes mellitus (DM) is one of the greatest public health threats in modern societies. Although during a few years it was suggested that DM had no significant effect in male reproductive function, this view has been challenged in recent years. The increasing incidence of DM worldwide will inevitably result in a higher prevalence of this pathology in men of reproductive age and subfertility or infertility associated with DM is expected to dramatically rise in upcoming years. From a clinical perspective, the evaluation of semen parameters, as well as spermatozoa deoxyribonucleic acid (DNA) integrity, are often studied due to their direct implications in natural and assisted conception. Nevertheless, recent studies based on the molecular mechanisms beyond glucose transport in testicular cells provide new insights in DM-induced alterations in male reproductive health. Testicular cells have their own glucose sensing machinery that react to hormonal fluctuations and have several mechanisms to counteract hyper- and hypoglycemic events. Moreover, the metabolic cooperation between testicular cells is crucial for normal spermatogenesis. Sertoli cells (SCs), which are the main components of blood–testis barrier, are not only responsible for the physical support of germ cells but also for lactate production that is then metabolized by the developing germ cells. Any alteration in this tied metabolic cooperation may have a dramatic consequence in male fertility potential. Therefore, we present an overview of the clinical significance of DM in the male reproductive health with emphasis on the molecular mechanisms beyond glucose fluctuation and transport in testicular cells.     

When selection deceives phylogeographic interpretation: the case of the Mediterranean house gecko, Hemidactylus turcicus (Linnaeus, 1758)

A previous study on Hemidactylus turcicus based on mtDNA makers indicated that this gecko has a Middle-East origin, and that the current phylogeographic pattern is the result of a very rapid spread from the east to the west of the species’ range. The same study identified two distinct mitochondrial lineages with low differentiation and genetic diversity. Since H. turcicus is known to be closely associated to humanized environments, its present distribution range and phylogeography is frequently interpreted to be the result of recurrent human-mediated introductions. These conclusions used to be the same as those used to interpret the results obtained for the European populations of another gecko, Tarentola mauritanica. However, a recent study has revealed that the phylogeographic pattern of T. mauritanica is not solely the result of a recent colonization, but also of a mitochondrial selective sweep. Could the same be occurring in H. turcicus? To answer this question, two mitochondrial (12S rRNA and cytochrome b) and two nuclear genes (ACM4 and Rag2) were used in this study. From the mtDNA data we confirmed the existence of two distinct phylogeographic lineages; one occurring exclusively in the northern Mediterranean (Clade A), and another one more widespread that is the only lineage present in North Africa (Clade B). In light of these results, we could hypothesize that H. turcicus had its origin in Turkey, and from there Clade A moved to Europe and Clade B to North Africa spreading latter into Europe. However, Clade A presents significantly higher nucleotide diversity for the nuclear DNA compared to the mtDNA, and neutrality tests gave significant results for the mitochondrial data. These results suggest that the lack of mtDNA genetic diversity and structure in the European population of H. turcicus could also be due to a selective sweep, and not only because of a recent colonization. Together with the situation reported in T. mauritanica, the identification of a hitch-hiking process occurring in H. turcicus, represents two unprecedented cases of a selective sweep taking place in the same geographic area shaping the phylogeographic patterns of two unrelated genera of geckos.     

Signalling pathways in pollen germination and tube growth

Summary. Signalling is an integral component in the establishment and maintenance of cellular identity. In plants, tip-growing cells represent an ideal system to investigate signal transduction mechanisms, and among these, pollen tubes (PTs) are one of the favourite models. Many signalling pathways have been identified during germination and tip growth, namely, Ca²⁺, calmodulin, phosphoinositides, protein kinases, cyclic AMP, and GTPases. These constitute a large and complex web of signalling networks that intersect at various levels such as the control of vesicle targeting and fusion and the physical state of the actin cytoskeleton. Here we discuss some of the most recent advances made in PT signal transduction cascades and their implications for our future research. For reasons of space, emphasis was given to signalling mechanisms that control PT reorientation, so naturally many other relevant works have not been cited. Correspondence and reprints: Departamento de Biologia Vegetal, Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal.     

Complex phylogeography in the Southern Smooth Snake (Coronella girondica) supported by mtDNA sequences

Palearctic reptiles with wide distribution through the Western Mediterranean are expected to display genetic substructuring because of the combining effects of current or past geographic barriers and climate fluctuations. We have examined this issue by sequencing cytochrome b and 16S rRNA mitochondrial fragments of 80 individuals of the snake Coronella girondica from 71 localities, covering the range of the species across Tunisia, Algeria, Morocco, Spain, Portugal, southern France and north‐western Italy. According to the obtained genealogy, C. girondica is structured into three divergent and well‐supported clades (north‐western Africa, Betic range and Iberia–France–Italy), which greatly match other phylogeographies already published for this region. Our estimations suggest that the divergence among the three clades took place approximately 1.4‐2.0 Ma, which roughly coincides with the Plio‐Pleistocene transition, characterized by an increase in climate variability. The existence of a clade in a narrow belt of south‐eastern Iberia represents another example of the high endemism rate of the region, with a key geographical situation and an important role in vicariant processes. Since the split among the three major lineages would be take place after the opening of the Strait of Gibraltar, overwater dispersal is here suggested. The subsequent genetic substructuring of these clades during the Pleistocene fits within the refugia‐within‐refugia model, highlighting the importance of the region as a scenario for multiple vicariant events.     

Morphology matches mtDNA lineages in the southern smooth snake (Coronella girondica) from Iberia

The rise of molecular techniques in the study of evolutionary histories has resulted in a gradual abandonment of morphological characters as the only sources of phylogenetic inference. However, morphological characters may be valuable for phylogenetic reconstruction, especially for tracking adaptive changes across phylogeographic groups defined by genetic markers. We examined the discriminative power of morphological characters between four mitochondrial clades covering almost the entire distribution area of the smooth snake Coronella girondica in the Western Mediterranean. We detected three characters showing sexual dimorphism (relative tail length, number of ventral and of subcaudal scale counts) and, more interestingly, two characters (number of subcaudal and of dorsal rows) displaying interclade differences. Almost all C. girondica examined had 21 dorsal rows except those from a narrow coastal belt in the south-eastern Iberian Peninsula, which had 19 dorsal rows. The distribution of these specimens matches a mitochondrial clade that originated approximately 1.4–2.0 million years ago. Both of these morphological characters support a Betic lineage with a rather well-defined contact zone with the other Iberian lineage, which has been maintained even without the existence of current geographic barriers. The long-term survival of the Betic lineage throughout the Pleistocene climatic oscillations suggests a systematic revision within C. girondica.     

Assessment of digenean parasitism in Nassarius reticulatus (L.) along the Portuguese coast: evaluation of possible impacts on reproduction and imposex expression

A survey was performed between June and September 2006 along the Portuguese coast to assess the prevalence of digenean parasitism in the netted whelk Nassarius reticulatus, a bioindicator of tributyltin (TBT) pollution. It was also intended to evaluate the effect of parasites on the reproduction of this gastropod species and their interference on the development of imposex (the superimposition of male characters onto prosobranch females) and male penis, based on field data. Five digenean species (Lepocreadium album, Gynaecotyla longiintestinata, Himasthla quissetensis, Diphtherostomum brusinae, and Cardiocephalus longicollis), plus 1 unidentified species, were found to infect N. reticulatus. Parasitism was spread along the Portuguese coast, but the higher values of prevalence were found in sheltered inshore areas where up to 67.4% of the animals were affected per sampling station. Parasitism has a castrating impact on the whelks and a reducing effect on male penis size, which causes serious disorders in the reproduction of N. reticulatus and may have an important impact in its population dynamics. However, no relationship between imposex severity and parasite infestation was found.