Journal of Experimental Biology - Latest Issue

• An early-life perspective is needed to explain the impact of gut microbiota on wild vertebrate phenotypes

  ABSTRACT

  Vertebrates house dense and diverse communities of microorganisms in their gastrointestinal tracts. These communities shape host physiological and ecological phenotypes in diverse ways, with implications for animal fitness in nature. Exposure to microbes during the earliest stages of life is particularly important because, during critical developmental windows, the microbiome is exceptionally plastic and interactions with microbes can have long-lasting physiological impacts on the host. Despite our understanding that early-life microbial interactions are important to host function broadly, the majority of research in this area has been performed in human or model organisms that are not representative of animals in the wild. Specifically, most gut microbiome studies in wildlife are cross-sectional and compare microbial communities across life stages using different individuals, as opposed to tracking the microbial communities and phenotypes of the same individuals from early to later life. This knowledge gap may hinder wildlife microbiome research, as the current model lacks an early-life perspective that can contextualize host phenotypic and fitness differences observed between animals at later life stages. Further, considering early-life microbial dynamics may offer insights to applied research, such as determining the optimal age to manipulate microbiomes for desired conservation outcomes. In this Commentary, we consider current understanding of the importance of early-life host–microbe interactions to vertebrate physiology across the lifespan, discuss why this perspective is necessary in wildlife studies, and provide practical recommendations for experimental designs that can address these questions, including field and laboratory approaches.

• ECR Spotlight – Patrícia Ferreira

  ECR Spotlight is a series of interviews with early-career authors from a selection of papers published in Journal of Experimental Biology and aims to promote not only the diversity of early-career researchers (ECRs) working in experimental biology but also the huge variety of animals and physiological systems that are essential for the ‘comparative’ approach. Patrícia Ferreira is an author on ‘ A second look at the stomach – a fishy perspective’, published in JEB. Patrícia conducted the research described in this article while a PhD candidate in Dr Jonathan M. Wilson's lab at Department of Biology, Wilfrid Laurier University, Canada. Patrícia is now a post-doctoral researcher in the lab of Dr Kathleen Gilmour at Department of Biology, University of Ottawa, Canada, investigating comparative vertebrate physiology, ion regulation and gastrointestinal physiology.

• A second look at the stomach – a fishy perspective

  ABSTRACT

  Despite the established evolutionary importance of stomach acidification in vertebrates, the exact contribution of this process to overall protein digestion, nutrient absorption, growth, energy metabolism and development has not been fully elucidated and is oftentimes subject to extensive scientific debate. This Commentary sets out to frame the current state of our understanding, highlighting unresolved issues and proposing where experimental approaches can be applied to address these questions. Furthermore, we explore in depth the tantalizing evolutionary and physiological puzzle of repeated loss of gastric function in fishes. In this way, we hope to help clarify the role of the gastric proton pump and stomach acidification in digestion, metabolism and growth in vertebrates.

• Diet-dependent production of calcium- and phosphorus-rich ‘spheroids’ along the intestine of Burmese pythons: identification of a new cell type?

  ABSTRACT

  Burmese pythons, Python molurus bivittatus, digest the skeleton of their prey; this must result in a high amount of calcium and phosphorus passing through the intestinal lining. To determine how Burmese pythons can process this ion influx, the effects of different nutritional diets were examined in juveniles reared in captivity using three different diets: a normal diet with calcium and phosphorus provided from entire rodents; a low-calcium and phosphorus diet using rodents with no bones (‘boneless prey’); and a calcium-rich diet composed of boneless rodents supplemented with calcium carbonate (CaCO₃) through intraperitoneal injections inside the prey.The effect of these diets was analysed along the intestinal mucosa using light and electron microscopy techniques (Alizarin Red S and peroxidase staining, EDX analysis). Blood calcium and hormone levels [parathyroid hormone (PTH) and calcitonin] were also analysed from fasting pythons and snakes repeatedly fed with either a normal prey diet or a low-calcium and -phosphorus diet (boneless rats). The results revealed the presence of specialised cells in the intestinal epithelium that are involved in the production of calcium and phosphorus particles in fed snakes. These cells have an apical crypt possessing a multi-layered particle made of calcium, phosphorus and iron-rich nucleation elements in the centre. In fasting snakes, this cell type has empty crypts. When snakes are fed with boneless prey, particles are not produced by this cell type, although iron elements are located within the crypts. When calcium supplements are added to a boneless meal, large particles fill the crypts. When snakes are fed repeatedly with a low-calcium diet, blood calcium level drops while levels of calcitonin, and particularly of those of PTH, increase. Therefore, Burmese pythons possess a specialised intestinal cell type involved in excreting excess dissolved calcium and phosphorus that originate from the prey and are precipitated as particles that must accumulate in the faeces. This cell type is also found in other snake species that eat vertebrates (some Boidae and a colubrid) along with a lizard, the Gila monster, Heloderma suspectum. A broader analysis among vertebrates that ingest their prey whole and dissolve the prey skeleton would allow a thorough evolutionary analysis.

• Adding a marker of gut integrity: an example of experimental augmentation as applied in Eisenia fetida

  ABSTRACT

  Gut integrity is critical for organismal health and capacity to host intestinal microbes. Markers of compromised luminal epithelium can serve as quality controls or variables in a wide variety of experiments and species. We combined the Smurf assay with existing bioassays to identify organisms which were moderately affected by experimental treatments, but not so severely as to show physical or behavioral pathology. The Smurf assay is most commonly used to detect impacts of age and disease in model organisms, particularly Drosophila, by feeding water-soluble food dye. Individuals with a compromised luminal epithelium exhibit leakage of gut contents into the body cavity, resulting in discoloration. We added the Smurf assay to standardized ecotoxicological methods for evaluating acute toxicity in the earthworm Eisenia fetida. Adding this marker allowed us to observe variation in our research population quickly and without microscopic examination or dissection.