Tentacle patterning during Exaiptasia diaphana pedal lacerate development differs between symbiotic and aposymbiotic animals

Exaiptasia diaphana, a tropical sea anemone known as Aiptasia, is a tractable model system for studying the cellular, physiological, and ecological characteristics of cnidarian-dinoflagellate symbiosis. Aiptasia is widely used as a proxy for coral-algal symbiosis, since both Aiptasia and corals form a symbiosis with members of the family Symbiodiniaceae. Laboratory strains of Aiptasia can be maintained in both the symbiotic (Sym) and aposymbiotic (Apo, without algae) states. Apo Aiptasia allow for the study of the influence of symbiosis on different biological processes and how different environmental conditions impact symbiosis. A key feature of Aiptasia is the ease of propagating both Sym and Apo individuals in the laboratory through a process called pedal laceration. In this form of asexual reproduction, small pieces of tissue rip away from the pedal disc of a polyp, then these lacerates eventually develop tentacles and grow into new polyps. While pedal laceration has been described in the past, details of how tentacles are formed or how symbiotic and nutritional state influence this process are lacking. Here we describe the stages of development in both Sym and Apo pedal lacerates. Our results show that Apo lacerates develop tentacles earlier than Sym lacerates, while over the course of 20 days, Sym lacerates end up with a greater number of tentacles. We describe both tentacle and mesentery patterning during lacerate development and show that they form through a single pattern in early stages regardless of symbiotic state. In later stages of development, Apo lacerate tentacles and mesenteries progress through a single pattern, while variable patterns were observed in Sym lacerates. We discuss how Aiptasia lacerate mesentery and tentacle patterning differs from oral disc regeneration and how these patterning events compare to postembryonic development in Nematostella vectensis, another widely-used sea anemone model. In addition, we demonstrate that Apo lacerates supplemented with a putative nutrient source developed an intermediate number of tentacles between un-fed Apo and Sym lacerates. Based on these observations, we hypothesize that pedal lacerates progress through two different, putatively nutrient-dependent phases of development. In the early phase, the lacerate, regardless of symbiotic state, preferentially uses or relies on nutrients carried over from the adult polyp. These resources are sufficient for lacerates to develop into a functional polyp. In the late phase of development, continued growth and tentacle formation is supported by nutrients obtained from either symbionts and/or the environment through heterotrophic feeding. Finally, we advocate for the implementation of pedal lacerates as an additional resource in the Aiptasia model system toolkit for studies of cnidarian-dinoflagellate symbiosis.

Sagittal expansion of the maxilla in an adult. A clinical case

Relevance. Skeletal Class III malocclusion is one of the most difficult to correct. Genetics, environmental factors, and postembryonic development influence its etiology. Sagittal expansion of the upper jaw will ensure the correct position of the lower jaw, which in turn will improve the patient's aesthetic parameters and health. The study examines a treatment method using the Fixed anterior growth guidance appliance (FAGGA).Materials and methods. This clinical case presents a 21-year-old male with skeletal class III due to maxillary bone deficiency. The patient refused surgery to increase the size of the upper jaw and opted for orthodontic treatment. The latter was performed using a Fixed anterior growth guidance appliance (FAGGA), followed by a rapid palatal (maxillary) expansion (RME) and brackets. We removed the FAGGA after eight months. The profile and occlusion improved.Results. The change in the inclination and protrusion of the maxillary incisors improved the profile. We received 2mm of space behind the upper right canine and 1.5mm of space behind the left one and the SNA angle increased by 2 degrees. The treatment continues with RME and brackets.Conclusions. An increase in inclination and protrusion of the maxillary incisors and a slight skeletal change improved the aesthetic parameters of the facial area.

Caenorhabditis elegans LET-413 Scribble is essential in the epidermis for growth, viability, and directional outgrowth of epithelial seam cells

The conserved adapter protein Scribble (Scrib) plays essential roles in a variety of cellular processes, including polarity establishment, proliferation, and directed cell migration. While the mechanisms through which Scrib promotes epithelial polarity are beginning to be unraveled, its roles in other cellular processes including cell migration remain enigmatic. In C. elegans, the Scrib ortholog LET-413 is essential for apical–basal polarization and junction formation in embryonic epithelia. However, whether LET-413 is required for postembryonic development or plays a role in migratory events is not known. Here, we use inducible protein degradation to investigate the functioning of LET-413 in larval epithelia. We find that LET-413 is essential in the epidermal epithelium for growth, viability, and junction maintenance. In addition, we identify a novel role for LET-413 in the polarized outgrowth of the epidermal seam cells. These stem cell-like epithelial cells extend anterior and posterior directed apical protrusions in each larval stage to reconnect to their neighbors. We show that the role of LET-413 in seam cell outgrowth is likely mediated largely by the junctional component DLG-1 discs large, which we demonstrate is also essential for directed outgrowth of the seam cells. Our data uncover multiple essential functions for LET-413 in larval development and show that the polarized outgrowth of the epithelial seam cells is controlled by LET-413 Scribble and DLG-1 Discs large.

Constraints and Opportunities for the Evolution of Metamorphic Organisms in a Changing Climate

We argue that developmental hormones facilitate the evolution of novel phenotypic innovations and timing of life history events by genetic accommodation. Within an individual’s life cycle, metamorphic hormones respond readily to environmental conditions and alter adult phenotypes. Across generations, the many effects of hormones can bias and at times constrain the evolution of traits during metamorphosis; yet, hormonal systems can overcome constraints through shifts in timing of, and acquisition of tissue specific responses to, endocrine regulation. Because of these actions of hormones, metamorphic hormones can shape the evolution of metamorphic organisms. We present a model called a developmental goblet, which provides a visual representation of how metamorphic organisms might evolve. In addition, because developmental hormones often respond to environmental changes, we discuss how endocrine regulation of postembryonic development may impact how organisms evolve in response to climate change. Thus, we propose that developmental hormones may provide a mechanistic link between climate change and organismal adaptation.

Prenatal effects of red and blue light on physiological and behavioural parameters of broiler chickens

Light during incubation can influence embryonic and postembryonic development of chickens, but the underlying mechanisms are poorly understood. Previous studies have demonstrated that red and blue lights during incubation had opposite effects on the development of embryonic melatonin biosynthesis; red light results in the highest and blue light in the lowest amplitude of the daily rhythm. Therefore, in this study, we investigated if exposure to monochromatic red (632 nm) and blue (463 nm) light during incubation can differently influence growth, selected biochemical (glucose, cholesterol, triacylglycerols) and endocrine (corticosterone and thyroid hormones) traits and behavioural parameters during postembryonic development in broiler chickens. For analysis, we used 10 and 11 hatchlings incubated in red and blue light, respectively and 10 birds per each group (six males and four females) in 3-weeks-old broilers. During the rapid growth phase (days 18, 20 and 21 of age), higher body weight was recorded in broilers incubated under red compared to blue light, whereas endocrine and metabolic traits did not differ between the treatments. The improved growth rate was related to behavioural traits, mainly because chickens incubated in red light exhibited more passive (resting, standing, preening, dust bathing) and less active behaviours (walking, foraging, fighting, wing-flapping) than the blue-light incubated birds. The time spent for eating and drinking and the results of the tonic immobility test did not differ between both groups. Our results suggest that red and blue monochromatic light during incubation can differently program the postembryonic development of broilers, with possible consequences for their growth and welfare.

Function and Evolution of Nuclear Receptors in Environmental-Dependent Postembryonic Development

Nuclear receptors (NRs) fulfill key roles in the coordination of postembryonal developmental transitions in animal species. They control the metamorphosis and sexual maturation in virtually all animals and by that the two main environmental-dependent developmental decision points. Sexual maturation and metamorphosis are controlled by steroid receptors and thyroid receptors, respectively in vertebrates, while both processes are orchestrated by the ecdysone receptor (EcR) in insects. The regulation of these processes depends on environmental factors like nutrition, temperature, or photoperiods and by that NRs form evolutionary conserved mediators of phenotypic plasticity. While the mechanism of action for metamorphosis and sexual maturation are well studied in model organisms, the evolution of these systems is not entirely understood and requires further investigation. We here review the current knowledge of NR involvement in metamorphosis and sexual maturation across the animal tree of life with special attention to environmental integration and evolution of the signaling mechanism. Furthermore, we compare commonalities and differences of the different signaling systems. Finally, we identify key gaps in our knowledge of NR evolution, which, if sufficiently investigated, would lead to an importantly improved understanding of the evolution of complex signaling systems, the evolution of life history decision points, and, ultimately, speciation events in the metazoan kingdom.