Testing models of parental investment strategy and offspring size in ants

Parental investment strategies can be fixed or flexible. A fixed strategy predicts making all offspring a single ‘optimal’ size. Dynamic models predict flexible strategies with more than one optimal size of offspring. Patterns in the distribution of offspring sizes may thus reveal the investment strategy. Static strategies should produce normal distributions. Dynamic strategies should often result in non-normal distributions. Furthermore, variance in morphological traits should be positively correlated with the length of developmental time the traits are exposed to environmental influences. Finally, the type of deviation from normality (i.e., skewed left or right, or platykurtic) should be correlated with the average offspring size. To test the latter prediction, we used simulations to detect significant departures from normality and categorize distribution types. Data from three species of ants strongly support the predicted patterns for dynamic parental investment. Offspring size distributions are often significantly non-normal. Traits fixed earlier in development, such as head width, are less variable than final body weight. The type of distribution observed correlates with mean female dry weight. The overall support for a dynamic parental investment model has implications for life history theory. Predicted conflicts over parental effort, sex investment ratios, and reproductive skew in cooperative breeders follow from assumptions of static parental investment strategies and omnipresent resource limitations. By contrast, with flexible investment strategies such conflicts can be either absent or maladaptive. Electronic Supplementary Material Supplementary material is available for this article at     

Thyroid hormone and retinoic acid interact to regulate zebrafish craniofacial neural crest development

Craniofacial and ocular morphogenesis require proper regulation of cranial neural crest migration, proliferation, survival and differentiation. Although alterations in maternal thyroid hormone (TH) are associated with congenital craniofacial anomalies, the role of TH on the neural crest has not been previously described. Using zebrafish, we demonstrate that pharmacologic and genetic alterations in TH signaling disrupt cranial neural crest migration, proliferation, and survival, leading to craniofacial, extraocular muscle, and ocular developmental abnormalities. In the rostral cranial neural crest that gives rise to the periocular mesenchyme and the frontonasal process, retinoic acid (RA) rescued migratory defects induced by decreased TH signaling. In the caudal cranial neural crest, TH and RA had reciprocal effects on anterior and posterior pharyngeal arch development. The interactions between TH and RA signaling were partially mediated by the retinoid X receptor. We conclude that TH regulates both rostral and caudal cranial neural crest. Further, coordinated interactions of TH and RA are required for proper craniofacial and ocular development.     

ESR Detection of 1O2 Reveals Enhanced Redox Activity in Illuminated Cell Cultures

Low-energy visible light (LEVL) has previously been found to modulate various processes in different biological systems. One explanation for the stimulatory effect of LEVL is light-induced reactive oxygen species formation. In the present study, both sperm and skin cells were illuminated with LEVL and were found to generate singlet oxygen (¹O₂). The detection of ¹O₂ was performed using a trapping probe, 2,2,6,6-tetramethyl-4-piperidone, coupled with electron paramagnetic resonance spectroscopy. In addition, we have shown that, together with ¹O₂ generation, LEVL illumination increases the reductive capacity of the cells, which explains the difficulties encountered in ¹O₂ detection. The potential of visible light to change the cellular redox state may explain the recently observed biostimulative effects exerted by LEVL.     

Copy number variation of transposable elements in Triticum–Aegilops genus suggests evolutionary and revolutionary dynamics following allopolyploidization

Key message

Here, we report on copy number variation of transposable elements and on the genome-specific proliferation in wheat. In addition, we report on revolutionary and evolutionary dynamics of transposons.

Abstract

Wheat is a valuable model for understanding the involvement of transposable elements (TEs) in speciation as wheat species (Triticum–Aegilops group) have diverged from a common ancestor, have undergone two events of speciation through allopolyploidy, and contain a very high fraction of TEs. However, an unbiased genome-wide examination of TE variation among these species has not been conducted. Our research utilized quantitative real time PCR to assess the relative copy numbers of 16 TE families in various Triticum and Aegilops species. We found (1) high variation and genome-specificity of TEs in wheat species, suggesting they were active throughout the evolution of wheat, (2) neither Ae. searsii nor Ae. speltoides by themselves can be the only contributors of the B genome to wheat, and (3) nonadditive changes in TE quantities in polyploid wheat. This study indicates the apparent involvement of large TEs in creating genetic variation in revolutionary and evolutionary scales following allopolyploidization events, presumably assisting in the diploidization of homeologous chromosomes.     

Orientation of the human sacrum: anthropological perspectives and methodological approaches

Discovering the nature of sacral orientation is of considerable anthropological importance. Therefore, this study aims at presenting a new anthropologically based definition for sacral anatomical orientation (SAO) angle, establishing standards of SAO for human population; examining the relationship between pelvic incidence (PI) and SAO; and associating SAO with demographic parameters. The study population consisted of 424 adult and 14 sub-adult (13-18 years, for SAO only) pelvises. Sacral orientation was measured using two different definitions: a) SAO is the angle created between the intersection of a line running parallel to the superior surface of the sacrum and a line running between the anterior superior iliac spine (ASIS) and the anterior-superior edge of the symphysis pubis; b) PI is the angle created between the perpendicular to the sacral plate at its midpoint and the line connecting this point to the middle of the axis of the acetabulum. SAO was measured using a specially designed mechanical measurement tool and a 3D digitizer. PI was measured via the 3D digitizer. The methods developed by us for measuring SAO and PI in skeletal material are valid and reliable. SAO and PI measures were highly correlated (r = -0.824, P < 0.001). The average SAO was 49.01 degrees (SD = 10.16), and the average PI 54.08 degrees (SD = 12.64). SAO was independent of ethnicity and sex, yet age dependent. This study establishes a methodology for estimating SAO and PI in skeletal material and furnishes the anthropological milieu with base line data regarding these parameters. Future studies in human evolution can greatly benefit from this study.     

TMF/ARA160 Governs the Dynamic Spatial Orientation of the Golgi Apparatus during Sperm Development

TMF/ARA160 is known to be a TATA element Modulatory Factor (TMF). It was initially identified as a DNA-binding factor and a coactivator of the Androgen receptor. It was also characterized as a Golgi-associated protein, which is essential for acrosome formation during functional sperm development. However, the molecular roles of TMF in this intricate process have not been revealed. Here, we show that during spermiogenesis, TMF undergoes a dynamic change of localization throughout the Golgi apparatus. Specifically, TMF translocates from the cis-Golgi to the trans-Golgi network and to the emerging vesicles surface, as the round spermatids develop. Notably, lack of TMF led to an abnormal spatial orientation of the Golgi and to the deviation of the trans-Golgi surface away from the nucleus of the developing round spermatids. Concomitantly, pro-acrosomal vesicles derived from the TMF^-/- Golgi lacked targeting properties and did not tether to the spermatid nuclear membrane thereby failing to form the acrosome anchoring scaffold, the acroplaxome, around the cell-nucleus. Absence of TMF also perturbed the positioning of microtubules, which normally lie in proximity to the Golgi and are important for maintaining Golgi spatial orientation and dynamics and for chromatoid body formation, which is impaired in TMF^-/- spermatids. In-silico evaluation combined with molecular and electron microscopic analyses revealed the presence of a microtubule interacting domain (MIT) in TMF, and confirmed the association of TMF with microtubules in spermatogenic cells. Furthermore, the MIT domain in TMF, along with microtubules integrity, are required for stable association of TMF with the Golgi apparatus. Collectively, we show here for the first time that a Golgi and microtubules associated protein is crucial for maintaining proper Golgi orientation during a cell developmental process.     

EPR study of the hydrophobic interaction of spectrin with fatty acids.

The hydrophobic interaction between spin-labelled stearic acid and spectrin was studied by electron paramagnetic resonance (EPR) and fluorescence quenching. The results are quantitatively interpreted in terms of two types of binding site on spectrin. A comparison between the results of the EPR and fluorescence experiments show the drawback of the fluorescence method in binding studies.