Biomedical subjects

L S Corley

Publications and source records attributed to L S Corley.

6 recordsLinked to original sources

PubMed2006

Insulin signaling and limb-patterning: candidate pathways for the origin and evolutionary diversification of beetle 'horns'.

Beetle 'horns' are rigid outgrowths of the insect cuticle used as weapons in contests for access to mates. Relative to their body size, beetle horns can be enormous. They protrude from any of five different regions of the head or thorax; they are curved, straight, branched or bladed; and their development is often coupled with the nutrient environment (male dimorphism) or with sex (sexual dimorphism). Here, we show that this extraordinary diversity of horns can be distilled down to four trajectories of morphological change--horn location, shape, allometry and dimorphism--and we illustrate how the developmental mechanisms regulating horn growth could generate each of these types of horn evolution. Specifically, we review two developmental pathways known to regulate growth of morphological structures in Drosophila and other insects: a limb-patterning pathway that specifies the location and shape of a structure, and the insulin pathway, which modulates trait growth in response to larval nutrition. We summarize preliminary evidence indicating that these pathways are associated with the development of beetle horns, and we show how subtle changes in the relative activities of these two pathways would be sufficient to generate most of the extant diversity of horn forms. Our objective is to intuitively connect genotype with phenotype, and to advocate an informed 'candidate gene' approach to studies of the developmental basis of evolution. We end by using this insight from development to offer a solution to the long-standing mystery of the scarabs: the observation by Darwin, Lameere, Arrow and others that this one family of beetles appeared to have a 'special tendency' towards the evolution of horns.

Animals↗

PubMed2000

Competition induces adaptive shifts in caste ratios of a polyembryonic wasp.

An important transition in insect life-history evolution was the shift from a solitary existence to living in groups comprising specialized castes. Caste-forming species produce some individuals that reproduce and others with worker functions that have few or no offspring. Morphologically specialized castes are well known in eusocial species like ants and termites, but castes have also evolved in less-studied groups like thrips, aphids and polyembryonic wasps. Because selection acts at both the individual and the colony level, ratios of investment in different castes are predicted to vary with environmental factors like competition and resources. However, experimental evidence for adaptive shifts in caste ratios is limited owing to the experimental difficulty of manipulating factors thought to influence caste ratios, and because some species produce behaviourally flexible castes that switch tasks in response to colony needs. Unlike other caste-forming species, the broods of polyembryonic wasps develop clonally, so that increased production of one caste probably results in decreased production of the other. Here we show that the polyembryonic wasp Copidosoma floridanum alters caste ratios in response to interspecific competition. Our results reveal a distinct trade-off by C. floridanum between reproduction and defence, and show experimentally that caste ratios shift in an adaptive manner.

Adaptation, Physiological↗

PubMed2000

Urochordates are monophyletic within the deuterostomes.

Understanding the phylogenetic relationships of the three major urochordate groups within the deuterostomes is central to understanding the evolution of the chordates. We have prepared a detailed phylogenetic analysis of urochordates based on comparisons of 10 new urochordate 18S ribosomal DNA sequences with other urochordate sequences in GenBank. Maximum parsimony, neighbor-joining, minimum evolution, and maximum likelihood analyses of this large urochordate data set are consistent with a topology in which the urochordates are monophyletic within the deuterostomes and there are four separate clades of urochordates. These four distinct clades--styelid + pyurid ascidians, molgulid ascidians, phlebobranch ascidians + thaliaceans, and larvaceans--are mostly consistent with traditional morphological hypotheses and classifications. However, we find that the ascidians may not be a monophyletic group (as they have been considered traditionally) but instead appear paraphyletic. Another disparity with traditional classification is that the thaliaceans do not form a separate urochordate clade but rather cluster with the phlebobranch ascidians. Larvaceans have long branch lengths, which can be problematic for molecular phylogenetic methods, and their position within the urochordates cannot be unequivocally determined with 18S rDNA. This is important because the tadpole morphology of larvacean and ascidian larvae is the key trait of interest that distinguishes urochordates as chordates. Nevertheless, the present data set resolves at least three clades of urochordates and suggests strongly that urochordates form a monophyletic clade within the deuterostomes.

Animals↗

PubMed1997

The origin and evolution of animal appendages.

Animals have evolved diverse appendages adapted for locomotion, feeding and other functions. The genetics underlying appendage formation are best understood in insects and vertebrates. The expression of the Distal-less (Dll) homeoprotein during arthropod limb outgrowth and of Dll orthologs (Dlx) in fish fin and tetrapod limb buds led us to examine whether expression of this regulatory gene may be a general feature of appendage formation in protostomes and deuterostomes. We find that Dll is expressed along the proximodistal axis of developing polychaete annelid parapodia, onychophoran lobopodia, ascidian ampullae, and even echinoderm tube feet. Dll/Dlx expression in such diverse appendages in these six coelomate phyla could be convergent, but this would have required the independent co-option of Dll/Dlx several times in evolution. It appears more likely that ectodermal Dll/Dlx expression along proximodistal axes originated once in a common ancestor and has been used subsequently to pattern body wall outgrowths in a variety of organisms. We suggest that this pre-Cambrian ancestor of most protostomes and the deuterostomes possessed elements of the genetic machinery for and may have even borne appendages.

Amino Acid Sequence↗

PubMed1986

Bronchiolitis obliterans and usual interstitial pneumonia. A comparative clinicopathologic study.

The clinical, radiographic, and pathologic features were studied in 24 cases of bronchiolitis obliterans and 16 cases of usual interstitial pneumonia, to define better their distinguishing characteristics. Bronchiolitis obliterans had a more acute onset often associated with fever, while the presentation of usual interstitial pneumonia was insidious with dyspnea and cough. The radiographs in usual interstitial pneumonia uniformly showed bilateral interstitial opacities, while they were more variable in bronchiolitis obliterans, with air space densities in 15 and interstitial opacities in nine. Prognosis was considerably better for bronchiolitis obliterans patients. Resolution of disease occurred in nearly half, while no patient with usual interstitial pneumonia recovered. Three individuals with bronchiolitis obliterans (12.5%) died of progressive disease, compared to 10 with usual interstitial pneumonia (62.5%). Pathologically, the lesion in bronchiolitis obliterans affected mainly air spaces in a peribronchiolar distribution, while the changes in usual interstitial pneumonia were mainly interstitial and randomly distributed. The fibrosis in bronchiolitis obliterans was composed of proliferating fibroblasts, compared to collagen deposition in usual interstitial pneumonia. These findings emphasize that bronchiolitis obliterans and usual interstitial pneumonia represent separate and distinct clinicopathologic entities.

Adult↗

PubMedDate not supplied

Developmental constraints on the mode of reproduction in the facultatively parthenogenetic cockroach Nauphoeta cinerea.

Considerable work in evolutionary biology has focused on the question of why sex persists. Both advantages to sex and constraints limiting a return to asexual reproduction are hypothesized to maintain sex once it evolves. Developmental constraints would limit asexual reproduction from a sexual species if it were difficult for females to switch from making eggs that do not develop without fertilization to making zygotes that are capable of developing in the absence of fertilization. Nauphoeta cinerea is an ovoviviparous cockroach in which some females are capable of switching from a sexual mode of reproduction to an asexual mode when isolated from males. Yet, while facultative parthenogenesis can occur in individuals, few females make the switch. Thus, this cockroach provides an ideal system for examining the potential role of developmental constraints in maintaining sex. Here we compare the cytogenetics and embryonic development of sexual and parthenogenetic offspring in N. cinerea. We find that deviations from normal ploidy levels are associated with abnormal development. All viable N. cinerea embryos exhibit typically hemimetabolous insect embryogenesis. Although there is no variation among embryos in development within a sexually produced clutch, we see extreme variation in asexually derived clutches. These results suggest that developmental constraints limit the success of asexual reproduction in this facultatively parthenogenetic cockroach. Our data further suggest that the specific constraint occurs in the switch from a meiotic mode of reproduction requiring fertilization to diploid zygotes that develop in the absence of fertilization.

Animals↗