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The Journal of Experimental Biology Apr 2018Many marine organisms and life stages lack specialized respiratory structures, like gills, and rely instead on cutaneous respiration, which they facilitate by having...
Many marine organisms and life stages lack specialized respiratory structures, like gills, and rely instead on cutaneous respiration, which they facilitate by having thin integuments. This respiratory mode may limit body size, especially if the integument also functions in support or locomotion. Pycnogonids, or sea spiders, are marine arthropods that lack gills and rely on cutaneous respiration but still grow to large sizes. Their cuticle contains pores, which may play a role in gas exchange. Here, we examined alternative paths of gas exchange in sea spiders: (1) oxygen diffuses across pores in the cuticle, a common mechanism in terrestrial eggshells, (2) oxygen diffuses directly across the cuticle, a common mechanism in small aquatic insects, or (3) oxygen diffuses across both pores and cuticle. We examined these possibilities by modeling diffusive oxygen fluxes across all pores in the body of sea spiders and asking whether those fluxes differed from measured metabolic rates. We estimated fluxes across pores using Fick's law parameterized with measurements of pore morphology and oxygen gradients. Modeled oxygen fluxes through pores closely matched oxygen consumption across a range of body sizes, which means the pores facilitate oxygen diffusion. Furthermore, pore volume scaled hypermetrically with body size, which helps larger species facilitate greater diffusive oxygen fluxes across their cuticle. This likely presents a functional trade-off between gas exchange and structural support, in which the cuticle must be thick enough to prevent buckling due to external forces but porous enough to allow sufficient gas exchange.
Topics: Animals; Arthropods; Body Size; Integumentary System Physiological Phenomena; Oxygen; Oxygen Consumption
PubMed: 29593081
DOI: 10.1242/jeb.177568 -
Biological Reviews of the Cambridge... Nov 2014Arguably the majority of species on Earth utilise tropical rainforest canopies, and much progress has been made in describing arboreal assemblages, especially for... (Review)
Review
Arguably the majority of species on Earth utilise tropical rainforest canopies, and much progress has been made in describing arboreal assemblages, especially for arthropods. The most commonly described patterns for tropical rainforest insect communities are host specificity, spatial specialisation (predominantly vertical stratification), and temporal changes in abundance (seasonality and circadian rhythms). Here I review the recurrent results with respect to each of these patterns and discuss the evolutionary selective forces that have generated them in an attempt to unite these patterns in a holistic evolutionary framework. I propose that species can be quantified along a generalist-specialist scale not only with respect to host specificity, but also other spatial and temporal distribution patterns, where specialisation is a function of the extent of activity across space and time for particular species. When all of these distribution patterns are viewed through the paradigm of specialisation, hypotheses that have been proposed to explain the evolution of host specificity can also be applied to explain the generation and maintenance of other spatial and temporal distribution patterns. The main driver for most spatial and temporal distribution patterns is resource availability. Generally, the distribution of insects follows that of the resources they exploit, which are spatially stratified and vary temporally in availability. Physiological adaptations are primarily important for host specificity, where nutritional and chemical variation among host plants in particular, but also certain prey species and fungi, influence host range. Physiological tolerances of abiotic conditions are also important for explaining the spatial and temporal distributions of some insect species, especially in drier forest environments where desiccation is an ever-present threat. However, it is likely that for most species in moist tropical rainforests, abiotic conditions are valuable indicators of resource availability, rather than physiologically limiting factors. Overall, each distribution pattern is influenced by the same evolutionary forces, but at differing intensities. Consequently, each pattern is linked and not mutually exclusive of the other distribution patterns. Most studies have examined each of these patterns in isolation. Future work should focus on examining the evolutionary drivers of these patterns in concert. Only then can the relative strength of resource availability and distribution, host defensive phenotypes, and biotic and abiotic interactions on insect distribution patterns be determined.
Topics: Adaptation, Physiological; Animal Distribution; Animals; Arthropods; Biological Evolution; Feeding Behavior; Forests
PubMed: 24581118
DOI: 10.1111/brv.12094 -
Arthropod Structure & Development May 2020Terrestrial arthropods often colonized and became important in freshwater ecosystems, but did so less often and with little consequence in marine habitats. This pattern...
Terrestrial arthropods often colonized and became important in freshwater ecosystems, but did so less often and with little consequence in marine habitats. This pattern cannot be explained by the physical properties of water alone or by limitations of the terrestrial arthropod body plan alone. One hypothesis is that transitions among terrestrial, aquatic and marine ecosystems are unlikely when well-adapted incumbent species in the recipient realm collectively resist entry by initially less well adapted newcomers. I evaluated and modified this hypothesis by examining the properties of donor and recipient ecosystems and the roles that insects play or do not play in each. I argue that the insularity and diminished competitiveness of most freshwater ecosystems makes them vulnerable to invasion from land and sea, and largely prevent transitions from freshwater to terrestrial and marine habitats by arthropods. Small terrestrial arthropods emphasize high locomotor performance and long-distance communication, traits that work less well in the denser, more viscous medium of water. These limitations pose particular challenges for insects colonizing highly escalated marine ecosystems, where small incumbent species rely more on passive than on active defences. Predatory insects are less constrained than herbivores, wood-borers, filter-feeders, sediment burrowers and social species.
Topics: Animals; Arthropods; Biological Evolution; Ecosystem; Oceans and Seas
PubMed: 32200289
DOI: 10.1016/j.asd.2020.100930 -
Communications Biology Apr 2023An antagonistic hemolymph-muscular system is essential for soft-bodied invertebrates. Many ecdysozoans (molting animals) possess neither a heart nor a vascular or...
An antagonistic hemolymph-muscular system is essential for soft-bodied invertebrates. Many ecdysozoans (molting animals) possess neither a heart nor a vascular or circulatory system, whereas most arthropods exhibit a well-developed circulatory system. How did this system evolve and how was it subsequently modified in panarthropod lineages? As the closest relatives of arthropods and tardigrades, onychophorans (velvet worms) represent a key group for addressing this question. We therefore analyzed the entire circulatory system of the peripatopsid Euperipatoides rowelli and discovered a surprisingly elaborate organization. Our findings suggest that the last common ancestor of Onychophora and Arthropoda most likely possessed an open vascular system, a posteriorly closed heart with segmental ostia, a pericardial sinus filled with nephrocytes and an impermeable pericardial septum, whereas the evolutionary origin of plical and pericardial channels is unclear. Our study further revealed an intermittent heartbeat-regular breaks of rhythmic, peristaltic contractions of the heart-in velvet worms, which might stimulate similar investigations in arthropods.
Topics: Animals; Phylogeny; Heart Rate; Invertebrates; Arthropods; Ascomycota; Cardiovascular System
PubMed: 37117786
DOI: 10.1038/s42003-023-04797-z -
Evolution; International Journal of... Jun 2023The relative sizes of body segments are a major determinant of the shape and functionality of an animal. Developmental biases affecting this trait can therefore have...
The relative sizes of body segments are a major determinant of the shape and functionality of an animal. Developmental biases affecting this trait can therefore have major evolutionary implications. In vertebrates, a molecular activator/inhibitor mechanism, known as the inhibitory cascade (IC), produces a simple and predictable pattern of linear relative size along successive segments. The IC model is considered the default mode of vertebrate segment development and has produced long-term biases in the evolution of serially homologous structures such as teeth, vertebrae, limbs, and digits. Here we investigate whether the IC model or an IC-like model also has controls on segment size development in an ancient and hyperdiverse group of extinct arthropods, the trilobites. We examined segment size patterning in 128 trilobite species, and during ontogenetic growth in three trilobite species. Linear relative segment size patterning is prominent throughout the trunk of trilobites in the adult form, and there is strict regulation of this patterning in newly developing segments in the pygidium. Extending the analysis to select stem and modern arthropods suggests that the IC is a common default mode of segment development capable of producing long-term biases in morphological evolution across arthropods as it does in vertebrates.
Topics: Animals; Biological Evolution; Fossils; Arthropods; Vertebrates; Phenotype
PubMed: 37074198
DOI: 10.1093/evolut/qpad057 -
International Journal of Biological... Jun 2023Water flux across cells predominantly occurs through the pore formed by the aquaporin channels. Since water balance is one of the most important challenges to...
Water flux across cells predominantly occurs through the pore formed by the aquaporin channels. Since water balance is one of the most important challenges to terrestrial animals, aquaporin evolution and diversity is known to play roles in animal terrestrialisation. Arachnids (Arthropoda: Chelicerata: Arachnida) are the second most diverse group and represent the pioneer land colonists in animals; however, there remains no thorough investigation on aquaporin evolution and diversity in this evolutionarily important lineage. Here we reported a phylogenetic study of aquaporin evolution and diversity using genomic data from 116 arachnid species covering almost all (15/16) extant orders. A previously unrecognised subfamily related to aquaporin-4 (i.e. Aqp4-like subfamily) via phylogenetic analysis was identified, suggesting certain underestimate of the arachnid aquaporin diversity in earlier studies probably due to limited taxonomic sampling. Further analysis indicates that this subfamily emerged deep within the life tree of arthropods. Gene tree of another Aqp4-like subfamily (PripL) shows an unexpected basal split between acariform mites (Acariformes) and other arachnids. A closer inspection demonstrated that the PripL evolved quickly and has been under differential selection pressure in acariform mites. Evidence is provided that the evolutionarily ancient Glp subfamily (i.e. aquaglyceroporin) is significantly expanded in terrestrial arachnids compared with their marine relatives. Finally, in spite of the phylogenetic diversity, there exists conservation of some exons in size, functional domain, and intron-insertion phase: an 81-bp and a 218-bp exon, respectively, in apq4-like and glp genes across Eumetazoa lineages including arachnids and human beings. Both exons encode the carboxyl-terminal NPA motif, implying the coding and splicing pressure during hundreds of million years of animal evolution. Hypotheses were tested to explore the possible link between these findings and arachnid terrestrialisation.
Topics: Animals; Humans; Arachnida; Phylogeny; Mites; Genome; Aquaporins
PubMed: 37068537
DOI: 10.1016/j.ijbiomac.2023.124480 -
Zootaxa Jun 2021Two new species of Homidia are described from Eastern China: H. hangzhouensis sp. nov. and H. wanensis sp. nov. The former is characterised by smooth chaetae e and l1 on...
Two new species of Homidia are described from Eastern China: H. hangzhouensis sp. nov. and H. wanensis sp. nov. The former is characterised by smooth chaetae e and l1 on labial base, two irregular transverse stripes on Abd. IV, absence of blue pigment on Ant. I-II and Abd. I-II and presence on Ant. III-IV, 7-9 macrochaetae on Abd. IV posteriorly and 24-34 smooth inner spines on dens. The latter can be identified by reduced blue body pigment, smooth chaeta e on labial base and having some posterior labial chaetae modified, appearing leaflike, 8-9 macrochaetae on Abd. IV posteriorly and 83 smooth inner spines on dens.
Topics: Animals; Arthropods; China
PubMed: 34186809
DOI: 10.11646/zootaxa.4995.1.11 -
PloS One 2024Haiku are short poems, each composed of about 10 words, that typically describe moments in nature. People have written haiku since at least the 17th century, and the...
Haiku are short poems, each composed of about 10 words, that typically describe moments in nature. People have written haiku since at least the 17th century, and the medium continues to be popular with poets, amateurs, educators, and students. Collectively, these poems represent an opportunity to understand which aspects of nature-e.g., which taxa and biological traits-resonate with humans and whether there are temporal trends in their representation or the emotions associated with these moments. We tested this potential using a mix of linguistic and biological methods, in analyses of nearly 4,000 haiku that reference arthropods. We documented the taxa and the life history traits represented in these poems and how they changed over time. We also analyzed the poems for emotion and tone. Our results reveal a mix of predictable trends and compelling surprises, each of which stand to potentially inform engagement strategies. At least 99 families of arthropods, in 28 orders, are represented in these haiku. The eight most commonly referenced taxa, from highest to lowest number of references, include: Lepidoptera, Hymenoptera, Diptera, Coleoptera, Araneae, Orthoptera, Hemiptera, and Odonata. Several common, conspicuous orders were never referenced, including Trichoptera, Plecoptera, and Megaloptera. The most commonly referenced traits relate to ecology (especially habitat, phenology, time of day), behavior (especially sound production), phenotype (especially color), and locomotion (especially flight). The least common traits in haiku relate to arthropod reproduction and physiology. Our analyses revealed few obvious temporal trends in the representations of taxa, biological traits, or emotion and tone. The broader implications of these results and possible future directions are discussed.
Topics: Animals; Humans; Arthropods; Insecta; Orthoptera; Coleoptera; Spiders
PubMed: 38568873
DOI: 10.1371/journal.pone.0298865 -
BMC Evolutionary Biology Jun 2017Classical cadherins are a metazoan-specific family of homophilic cell-cell adhesion molecules that regulate morphogenesis. Type I and type IV cadherins in this family...
BACKGROUND
Classical cadherins are a metazoan-specific family of homophilic cell-cell adhesion molecules that regulate morphogenesis. Type I and type IV cadherins in this family function at adherens junctions in the major epithelial tissues of vertebrates and insects, respectively, but they have distinct, relatively simple domain organizations that are thought to have evolved by independent reductive changes from an ancestral type III cadherin, which is larger than derived paralogs and has a complicated domain organization. Although both type III and type IV cadherins have been identified in hexapods and branchiopods, the process by which the type IV cadherin evolved is still largely unclear.
RESULTS
Through an analysis of arthropod genome sequences, we found that the only classical cadherin encoded in chelicerate genomes was the type III cadherin and that the two type III cadherin genes found in the spider Parasteatoda tepidariorum genome exhibited a complex yet ancestral exon-intron organization in arthropods. Genomic and transcriptomic data from branchiopod, copepod, isopod, amphipod, and decapod crustaceans led us to redefine the type IV cadherin category, which we separated into type IVa and type IVb, which displayed a similar domain organization, except type IVb cadherins have a larger number of extracellular cadherin (EC) domains than do type IVa cadherins (nine versus seven). We also showed that type IVa cadherin genes occurred in the hexapod, branchiopod, and copepod genomes whereas only type IVb cadherin genes were present in malacostracans. Furthermore, comparative characterization of the type IVb cadherins suggested that the presence of two extra EC domains in their N-terminal regions represented primitive characteristics. In addition, we identified an evolutionary loss of two highly conserved cysteine residues among the type IVa cadherins of insects.
CONCLUSIONS
We provide a genomic perspective of the evolution of classical cadherins among bilaterians, with a focus on the Arthropoda, and suggest that following the divergence of early arthropods, the precursor of the insect type IV cadherin evolved through stepwise reductive changes from the ancestral type III state. In addition, the complementary distributions of polarized genomic characters related to type IVa/IVb cadherins may have implications for our interpretations of pancrustacean phylogeny.
Topics: Amino Acid Sequence; Animals; Arthropod Proteins; Arthropods; Cadherins; Evolution, Molecular; Genomics; Phylogeny; Sequence Alignment
PubMed: 28623893
DOI: 10.1186/s12862-017-0991-2 -
PloS One 2024The diversification of macroscopic pelagic arthropods such as caryocaridid archaeostracans was a crucial aspect of the Great Ordovician Biodiversification Event, and the...
The diversification of macroscopic pelagic arthropods such as caryocaridid archaeostracans was a crucial aspect of the Great Ordovician Biodiversification Event, and the plankton revolution. A pelagic mode of life has been inferred for caryocaridids from their common presence in black graptolitic shales alongside carapace morphologies that appear streamlined. However, the hydrodynamic performance within the group and comparisons with other archaeostracans were lacking. Here we use a computational fluid dynamics approach to quantify the hydrodynamic performance of caryocaridids, and other early Palaeozoic archaeostracans including Arenosicaris inflata and Ordovician ceratiocaridids. We show that streamlining of the carapace was an important factor facilitating a pelagic mode of life in caryocaridids, in reducing the drag coefficient and facilitating a broader range of lift coefficients at different angles of attack. However, comparable hydrodynamic performance is also recovered for some ceratiocaridids. This suggests that alongside carapace streamlining, adaptations to appendages and thinning of the carapace were also important for a pelagic mode of life in Ordovician caryocaridids.
Topics: Hydrodynamics; Animals; Arthropods; Fossils; Animal Shells
PubMed: 38820465
DOI: 10.1371/journal.pone.0304559