THE SHIBANTAN LAGERSTÄTTE AND TERMINAL EDIACARAN ANIMAL EVOLUTION

AbstractOpsins, combined with a chromophore, are the primary light-sensing molecules in animals and are crucial for color vision. Throughout animal evolution, duplications and losses of opsin proteins are common, but it is unclear what is driving these gains and losses. Light availability is implicated, and dim environments are often associated with low opsin diversity and loss. Correlations between high opsin diversity and bright environments, however, are tenuous. To test if increased light availability is associated with opsin diversification, we examined diel niche and identified opsins using transcriptomes and genomes of 175 butterflies and moths (Lepidoptera). We found 14 independent opsin duplications associated with bright environments. Estimating their rates of evolution revealed that opsins from diurnal taxa evolve faster—at least 13 amino acids were identified with higher dN/dS rates, with a subset close enough to the chromophore to tune the opsin. These results demonstrate that high light availability increases opsin diversity and evolution rate in Lepidoptera.

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Sea urchin larvae utilize light for regulating the pyloric opening

BMC Biology ◽

10.1186/s12915-021-00999-1 ◽

2021 ◽

Vol 19 (1) ◽

Author(s):

Junko Yaguchi ◽

Shunsuke Yaguchi

Keyword(s):

Signaling Pathway ◽

Digestive Tract ◽

Sea Urchin ◽

Visual Information ◽

Biological Activities ◽

Regulatory System ◽

Sister Group ◽

Animal Evolution ◽

Deuterostome Evolution ◽

Visual Systems

Abstract Background Light is essential for various biological activities. In particular, visual information through eyes or eyespots is very important for most of animals, and thus, the functions and developmental mechanisms of visual systems have been well studied to date. In addition, light-dependent non-visual systems expressing photoreceptor Opsins have been used to study the effects of light on diverse animal behaviors. However, it remains unclear how light-dependent systems were acquired and diversified during deuterostome evolution due to an almost complete lack of knowledge on the light-response signaling pathway in Ambulacraria, one of the major groups of deuterostomes and a sister group of chordates. Results Here, we show that sea urchin larvae utilize light for digestive tract activity. We found that photoirradiation of larvae induces pyloric opening even without addition of food stimuli. Micro-surgical and knockdown experiments revealed that this stimulating light is received and mediated by Go(/RGR)-Opsin (Opsin3.2 in sea urchin genomes) cells around the anterior neuroectoderm. Furthermore, we found that the anterior neuroectodermal serotoninergic neurons near Go-Opsin-expressing cells are essential for mediating light stimuli-induced nitric oxide (NO) release at the pylorus. Our results demonstrate that the light>Go-Opsin>serotonin>NO pathway functions in pyloric opening during larval stages. Conclusions The results shown here will lead us to understand how light-dependent systems of pyloric opening functioning via neurotransmitters were acquired and established during animal evolution. Based on the similarity of nervous system patterns and the gut proportions among Ambulacraria, we suggest the light>pyloric opening pathway may be conserved in the clade, although the light signaling pathway has so far not been reported in other members of the group. In light of brain-gut interactions previously found in vertebrates, we speculate that one primitive function of anterior neuroectodermal neurons (brain neurons) may have been to regulate the function of the digestive tract in the common ancestor of deuterostomes. Given that food consumption and nutrient absorption are essential for animals, the acquirement and development of brain-based sophisticated gut regulatory system might have been important for deuterostome evolution.

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Diet Diversity in Carnivorous Terebrid Snails Is Tied to the Presence and Absence of a Venom Gland

Toxins ◽

10.3390/toxins13020108 ◽

2021 ◽

Vol 13 (2) ◽

pp. 108

Author(s):

Juliette Gorson ◽

Giulia Fassio ◽

Emily S. Lau ◽

Mandë Holford

Keyword(s):

Venom Gland ◽

Molecular Study ◽

Strongly Correlated ◽

Animal Evolution ◽

Diet Diversity ◽

Dietary Breadth ◽

Venom Composition ◽

Marine Snails ◽

Predatory Strategy ◽

Definition Of

Predator-prey interactions are thought to play a driving role in animal evolution, especially for groups that have developed venom as their predatory strategy. However, how the diet of venomous animals influences the composition of venom arsenals remains uncertain. Two prevailing hypotheses to explain the relationship between diet and venom composition focus on prey preference and the types of compounds in venom, and a positive correlation between dietary breadth and the number of compounds in venom. Here, we examined venom complexity, phylogenetic relationship, collection depth, and biogeography of the Terebridae (auger snails) to determine if repeated innovations in terebrid foregut anatomy and venom composition correspond to diet variation. We performed the first molecular study of the diet of terebrid marine snails by metabarcoding the gut content of 71 terebrid specimens from 17 species. Our results suggest that the presence or absence of a venom gland is strongly correlated with dietary breadth. Specifically, terebrid species without a venom gland displayed greater diversity in their diet. Additionally, we propose a revision of the definition of venom complexity in conoidean snails to more accurately capture the breadth of ecological influences. These findings suggest that prey diet is an important factor in terebrid venom evolution and diversification and further investigations of other understudied organisms, like terebrids, are needed to develop robust hypotheses in this area.

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Molecular clocks and the early evolution of metazoan nervous systems

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2015.0046 ◽

2015 ◽

Vol 370 (1684) ◽

pp. 20150046 ◽

Cited By ~ 23

Author(s):

Gregory A. Wray

Keyword(s):

Sensory Processing ◽

Fossil Record ◽

Sequence Data ◽

Divergence Times ◽

Molecular Clocks ◽

Sense Organs ◽

Animal Evolution ◽

Nervous Systems ◽

Nervous System Evolution ◽

Fossil Records

The timing of early animal evolution remains poorly resolved, yet remains critical for understanding nervous system evolution. Methods for estimating divergence times from sequence data have improved considerably, providing a more refined understanding of key divergences. The best molecular estimates point to the origin of metazoans and bilaterians tens to hundreds of millions of years earlier than their first appearances in the fossil record. Both the molecular and fossil records are compatible, however, with the possibility of tiny, unskeletonized, low energy budget animals during the Proterozoic that had planktonic, benthic, or meiofaunal lifestyles. Such animals would likely have had relatively simple nervous systems equipped primarily to detect food, avoid inhospitable environments and locate mates. The appearance of the first macropredators during the Cambrian would have changed the selective landscape dramatically, likely driving the evolution of complex sense organs, sophisticated sensory processing systems, and diverse effector systems involved in capturing prey and avoiding predation.

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Lack of support for Deuterostomia prompts reinterpretation of the first Bilateria

Science Advances ◽

10.1126/sciadv.abe2741 ◽

2021 ◽

Vol 7 (12) ◽

pp. eabe2741

Author(s):

Paschalia Kapli ◽

Paschalis Natsidis ◽

Daniel J. Leite ◽

Maximilian Fursman ◽

Nadia Jeffrie ◽

...

Keyword(s):

Systematic Error ◽

Tree Reconstruction ◽

Simulation Experiments ◽

Animal Evolution ◽

Phylogenetic Studies ◽

Branch Lengths ◽

Molecular Phylogenetic ◽

Common Ancestors

The bilaterally symmetric animals (Bilateria) are considered to comprise two monophyletic groups, Protostomia (Ecdysozoa and the Lophotrochozoa) and Deuterostomia (Chordata and the Xenambulacraria). Recent molecular phylogenetic studies have not consistently supported deuterostome monophyly. Here, we compare support for Protostomia and Deuterostomia using multiple, independent phylogenomic datasets. As expected, Protostomia is always strongly supported, especially by longer and higher-quality genes. Support for Deuterostomia, however, is always equivocal and barely higher than support for paraphyletic alternatives. Conditions that cause tree reconstruction errors—inadequate models, short internal branches, faster evolving genes, and unequal branch lengths—coincide with support for monophyletic deuterostomes. Simulation experiments show that support for Deuterostomia could be explained by systematic error. The branch between bilaterian and deuterostome common ancestors is, at best, very short, supporting the idea that the bilaterian ancestor may have been deuterostome-like. Our findings have important implications for the understanding of early animal evolution.

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