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The larval period in anurans is highly plastic. Even though larval period length and larval size have been the most studied characteristics showing intraspecific variability, other features such as morphology, behavior, food preferences and physiology have also been described as plastic. Metamorphic changes are triggered by thyroid and interrenal hormones, and environmental signals modulate the onset of metamorphosis via the hypothalamic–pituitary–interrenal axis. The South American bufonid toad Rhinella arenarum from nearby Buenos Aires City has a larval period of 30–120 days under the same environmental conditions. The goal of this study was to evaluate life‐history traits in tadpoles from different localities and potential morphological differences among tadpoles with different larval period length. For this purpose, we reared under natural conditions tadpoles from two different localities nearby Buenos Aires City and in three different years measured their size at the end of metamorphosis and recorded their larval period length. The external appearance, histo‐morphology and morphometry of the skin and kidney/interrenal complex were studied in metamorphs with short and long larval periods (SLP and LLP, respectively). We observed a larval period lasting 30–120 days in tadpoles from different localities or years. SLP metamorphs were smaller, darker, had less protruding eyes without eyelids, a thinner epidermis and fewer skin glands than LLP metamorphs. The secretion of skin glands from SLP tadpoles had acidic glycoconjugates. Kidney size was similar between LLP and SLP metamorphs, but the former had an adult‐like histomorphology. Interrenal gland in LLP early and late climax tadpoles had cells with a high nucleus/cell diameter ratio, a sign of highly active steroidogenic cells. Overall, these results show that intraspecific variability in size, skin and interrenal gland development is associated with differences in larval period length. Distinct skin gland number and secretion, along with distinct interrenal histology at late climax, could have physiological consequences in the post‐metamorphic life. [ABSTRACT FROM AUTHOR]

The sperm cell ultrastructure provides important insights into fertilization mechanism and phylogenetic relationships. However, it has rarely been included in phylogenetic analysis of anurans. This work aims to characterize the ultrastructure of the mature spermatozoa in the genus Leptodactylus, to relate the observed variations with the different reproductive strategies and define characters to optimize in a previously published cladogram of this genus. We studied 24 species distributed into four groups: L. fuscus, L. latrans, L. melanonotus and L. pentadactylus where morphological characters were coded and optimized using the parsimony method. The analyzed spermatozoa have three conspicuous regions: head, middle zone and tail. Regarding the head, a short and thin acrosomal vesicle is observed in species of the groups L. fuscus and L. pentadactylus , but it is long and thick in most of the studied species of the groups L. latrans and L. melanonotus. Furthermore, nuclear lacunae are observed in most species. In relation to the middle zone, an organelle-free cytoplasmic region was observed in species of the groups L. fuscus, L. latrans and L. melanonotus , but it was absent in species of the L. pentadactylus group. Most of the studied species showed a mitochondrial collar and cytoplasmic canal. Finally, in the tail all of the species have an axoneme, an undulating membrane, and an axial fiber, but only some have a juxtaxonemal fiber. Results show the thick acrosomal vesicle as a synapomorphy of the clade L. latrans + L. melanonotus. The presence of nuclear lacunae and the absence of a sub-acrosomal cone optimizes as a putative synapomorphy of Leptodactylidae. In conclusion, we observed a relationship between reproductive strategies and spermatozoa morphology, which also supports the phylogenetic relationships in this genus. Schematic reconstruction of the morphology of two types of spermatozoa (A and B) in the genus Leptodactylus and optimization of reproductive modes on a pruned phylogenetic hypothesis for Leptodactylidae. [Display omitted] [ABSTRACT FROM AUTHOR]

The endocannabinoid system (eCS), is a complex system, comprising the main endogenous ligands anandamide and 2-arachidonoyl glycerol, the cannabinoid receptors CB1 and CB2 and the biosynthetic and degrading enzymes. Cumulative evidence shows that the eCS plays an important role in reproduction, from egg fertilization to parturition. Therefore, alterations in this system, either by recreation/therapeutic use of cannabis or deregulation of the endogenous cannabinoids, might lead to adverse pregnancy outcomes, including retardation in embryo development, poor blastocyst implantation, inhibition of decidualization, miscarriage and compromised placentation. Nevertheless, the molecular mechanisms by which the eCS participates in different stages of pregnancy remain poorly understood. In this review, we will examine the evidence from animal and human studies to support the role of the eCS in implantation, early-to-late pregnancy and placentation as well as the difficulties of targeting this system for treatment of female infertility., (© 2016 Society for Reproduction and Fertility.)