bluuebunny/crossref_metadata_2025_split huggingface dataset:
Origin and evolution of animal life cycles
Authors: NIELSEN CLAUS 
Published: August 2010

ABSTRACTThe ‘origin of larvae’ has been widely discussed over the years, almost invariably with the tacit understanding that larvae are secondary specializations of early stages in a holobenthic life cycle.Considerations of the origin and early radiation of the metazoan phyla have led to the conclusion that the ancestral animal (= metazoan) was a holopelagic organism, and that pelago‐benthic life cycles evolved when adult stages of holopelagic ancestors became benthic, thereby changing their life style, including their feeding biology.The literature on the larval development and phylogeny of animal phyla is reviewed in an attempt to infer the ancestral life cycles of the major animal groups. The quite detailed understanding of larval evolution in some echinoderms indicates that ciliary filter‐feeding was ancestral within the phylum, and that planktotrophy has been lost in many clades. Similarly, recent studies of the developmental biology of ascidians have demonstrated that a larval structure, such as the tail of the tadpole larva, can easily be lost, viz. through a change in only one gene. Conversely, the evolution of complex structures, such as the ciliary bands of trochophore larvae, must involve numerous genes and numerous adaptations.The following steps of early metazoan evolution have been inferred from the review.The holopelagic ancestor, blastaea, probably consisted mainly of choanocytes, which were the feeding organs of the organism. Sponges may have evolved when blastaea‐like organisms settled and became reorganized with the choanocytes in collar chambers.The eumetazoan ancestor was probably the gastraea, as suggested previously by Haeckel. It was holopelagic and digestion of captured particles took place in the archenteron. Cnidarians and ctenophores are living representatives of this type of organization. The cnidarians have become pelago‐benthic with the addition of a sessile, adult polyp stage; the pelagic gastraea‐like planula larva is retained in almost all major groups, but only anthozoans have feeding larvae.Within the Bilateria, two major lines of evolution can be recognized: Protostomia and Deuterostomia. In protostomes, trochophores or similar types are found in most spiralian phyla; trochophore‐like ciliary bands are found in some rotifers, whereas all other aschelminths lack ciliated larvae. It seems probable that the trochophore was the larval type of the ancestral, pelago‐benthic spiralian and possible that it was ancestral in all protostomes. Most of the non‐chordate deuterostome phyla have ciliary filter‐feeding larvae of the dipleurula type, and this strongly indicates that the ancestral deuterostome had this type of larva.
Can video images imitate real stimuli in animal behaviour experiments?
Authors: D'EATH RICHARD B. 
Published: August 2010

ABSTRACTThe use of video images in place of natural stimuli in animal behaviour experiments is reviewed. Unlike most other artificial means of stimulus presentation, video stimuli can depict complex moving objects such as other animals, preserving the temporal and spatial patterns of movement precisely as well as colour and sounds for repeated playback. Computer editing can give flexibility and control over all elements of the stimulus. A variety of limitations of video image presentation are also considered. Televisions and video monitors are designed with human vision in mind, and some non‐human animals that differ in aspects of visual processing such as their colour vision, critical flicker‐fusion threshold, perception of depth and visual acuity, may perceive video images differently to ourselves. The failure of video stimuli to interact with subjects can be a drawback for some studies. For video to be useful, it is important to confirm that the subject animal responds to the image in a comparable way to the real stimulus, and the criteria used to assess this are discussed. Finally, the contribution made by video studies to date in the understanding of animal visual responses is considered, and recommendations as to the future uses of video are made.
Frugivory and seed dispersal by vertebrates in the Oriental (Indomalayan) Region
Authors: CORLETT RICHARD T. 
Published: August 2010

ABSTRACTCurrent knowledge of frugivory and seed dispersal by vertebrates in the Oriental Region is summarized. Some degree of frugivory has been reported for many fish and reptile species, almost half the genera of non‐marine mammals and more than 40% of bird genera in the region. Highly frugivorous species, for which fruit dominates the diet for at least part of the year, occur in at least two families of reptiles, 12 families of mammals and 17 families of birds. Predation on seeds in fleshy fruits is much less widespread taxonomically: the major seed predators are colobine monkeys and rodents among the mammals, and parrots, some pigeons, and finches among the birds. Most seeds in the Oriental Region, except near its northern margins, are dispersed by vertebrate families which are endemic to the region or to the Old World. Small fruits and large, soft fruits with many small seeds are consumed by a wide range of potential seed dispersal agents, including species which thrive in small forest fragments and degraded landscapes. Larger, bigger‐seeded fruits are consumed by progressively fewer dispersers, and the largest depend on a few species of mammals and birds which are highly vulnerable to hunting, fragmentation and habitat loss.
The dynamics of predation onGammarusspp. (Crustacea: Amphipoda)
Authors: MACNEIL CALUM , DICK JAIMIE T. A. , ELWOOD ROBERT W. 
Published: August 2010

ABSTRACTGammarusspp. (Crustacea: Amphipoda) are widespread throughout a diverse range of marine, freshwater and estuarine/brackish habitats, often dominating benthic macroinvertebrate communities in terms of both numbers and/or biomass.Gammarusspp. are the dominant macroinvertebrate prey items of many fish, whether as a seasonal food source or a year‐round staple. Selective predation by fish onGammarusspp. is often linked to parasitism and the body size of the prey.Gammarusspp. populations are under increasing threat from both pollution and replacement/displacement by introduced species. Loss of populations and species invasions/replacements could have significant impacts on native predator species if the predator(s) cannot successfully adapt their feeding patterns to cope with non‐indigenousGammarusprey species. Despite this, many fish predation studies do not identifyGammarusprey to species level. This lack of precision could be important, asGammarusspp. exhibit wide variations in physiochemical tolerances, habitat requirements, abilities to invade and susceptibility to replacement. Although rarely acknowledged, the impacts of nonpiscean predators (particularly macroinvertebrates) onGammarusprey species may frequently be stronger than those exerted by fish. A major aim of this review is to ascertain the current importance ofGammarusas a prey species, such that the implications of changes inGammarusspp. populations can be more accurately assessed by interested groups such as ecologists and fisheries managers. We also review the dynamics ofGammarusspp. as prey to a diverse array of mammals, birds, amphibians, insects, flatworms, other crustaceans such as crabs and crayfish and, perhaps most importantly, otherGammarusspp.
Conodont affinity and chordate phylogeny
Authors: DONOGHUE PHILIP C. J. , FOREY PETER L. , ALDRIDGE RICHARD J. 
Published: August 2010

ABSTRACTCurrent information on the conodontsClydagnathus windsorensis(Globensky) andPromissum pulchrumKovács‐ Endrödy, together with the latest interpretations of conodont hard tissues, are reviewed and it is concluded that sufficient evidence exists to justify interpretation of the conodonts on a chordate model. A new phylogenetic analysis is undertaken, consisting of 17 chordate taxa and 103 morphological, physiological and biochemical characters; conodonts are included as a primary taxon. Various experiments with character coding, taxon deletion and the use of constraint trees are carried out. We conclude that conodonts are cladistically more derived than either hagfishes or lampreys because they possess a mineralised dermal skeleton and that they are the most plesiomorphic member of the total group Gnathostomata. We discuss the evolution of the nervous and sensory systems and the skeleton in the context of our optimal phylogenetic tree. There appears to be no simple evolution of free to canal‐enclosed neuromasts; organised neuromasts within canals appear to have arisen at least three times from free neuromasts or neuromasts arranged within grooves. The mineralised vertebrate skeleton first appeared as odontodes of dentine or dentine plus enamel in the paraconodont/euconodont feeding apparatus. Bone appeared later, co‐ordinate with the development of a dermal skeleton, and it appears to have been primitively acellular. Atubular dentine is more primitive than tubular dentine. However, the subsequent distribution of the different types of dentine (e.g. mesodentine, orthodentine), suggests that these tissue types are homoplastic. The topology of relationships and known stratigraphic ranges of taxa in our phylogeny predict the existence of myxinoids and petromyzontids in the Cambrian.
A critical reappraisal of the fossil record of the bilaterian phyla
Authors: BUDD GRAHAM E. , JENSEN SÖREN 
Published: August 2010

ABSTRACTIt has long been assumed that the extant bilaterian phyla generally have their origin in the Cambrian explosion, when they appear in an essentially modern form. Both these assumptions are questionable. A strict application of stem‐ and crown‐group concepts to phyla shows that although the branching points of many clades may have occurred in the Early Cambrian or before, the appearance of the modern body plans was in most cases later: very few bilaterian phyla sensu stricto have demonstrable representatives in the earliest Cambrian. Given that the early branching points of major clades is an inevitable result of the geometry of clade diversification, the alleged phenomenon of phyla appearing early and remaining morphologically static is seen not to require particular explanation. Confusion in the definition of a phylum has thus led to attempts to explain (especially from a developmental perspective) a feature that is partly inevitable, partly illusory. We critically discuss models for Proterozoic diversification based on small body size, limited developmental capacity and poor preservation and cryptic habits, and show that the prospect of lineage diversification occurring early in the Proterozoic can be seen to be unlikely on grounds of both parsimony and functional morphology. Indeed, the combination of the body and trace fossil record demonstrates a progressive diversification through the end of the Proterozoic well into the Cambrian and beyond, a picture consistent with body plans being assembled during this time. Body‐plan characters are likely to have been acquired monophyletically in the history of the bilaterians, and a model explaining the diversity in just one of them, the coelom, is presented. This analysis points to the requirement for a careful application of systematic methodology before explanations are sought for alleged patterns of constraint and flexibility.
The grand game of metazoan phylogeny: rules and strategies
Authors: JENNER RONALD A. , SGHRAM FREDERICK R. 
Published: August 2010

ABSTRACTMany cladistic analyses of animal phylogeny have been published by authors arguing that their results are well supported. Comparison of these analyses indicates that there can be as yet no general consensus about the evolution of the animal phyla. We show that the various cladistic studies published to date differ significantly in methods of character selection, character coding, scoring and weighting, ground‐pattern reconstructions, and taxa selection. These methodological differences are seldom made explicit, which hinders comparison of different studies and makes it impossible to assess a particular phylogeny outside its own scope. The effects of these methodological differences must be considered before we can hope to reach a morphological reference framework needed for effective comparison and combination with the evidence obtained from molecular and developmental genetic studies.
Tunicate tails, stolons, and the origin of the vertebrate trunk
Authors: LACALLI THURSTON C. 
Published: August 2010

ABSTRACTTunicates are primitive chordates that develop a transient ‘tail’ in the larval stage that is generally interpreted as a rudimentary version of the vertebrate trunk. Not all tunicates have tails, however. The groups that lack them, salps and pyrosomes, instead have a trunk‐like reproductive stolon located approximately where the tail would otherwise be. In salps, files of blastozooids are formed along the sides of the stolon. The tail and caudal trunk in more advanced chordates could have evolved from a stolon of this type, an idea referred to here as the ‘stolon hypothesis’. This means the vertebrate body could be a composite structure, since there is the potential for each somite to incorporate elements originally derived from a complete functional zooid. If indeed this has occurred, it should be reflected in some fashion in gene expression patterns in the vertebrate trunk. Selected morphological and molecular data are reviewed to show that they provide some circumstantial support for the stolon hypothesis. The case would be stronger if it could be demonstrated that salps and/or pyrosomes are ancestral to other tunicates. The molecular phylogenies so far available generally support the idea of a pelagic ancestor, but offer only limited guidance as to which of the surviving pelagic groups most closely resembles it. The principal testable prediction of the stolon hypothesis is that head structures (or their homologues) should be duplicated in series in the trunk in advanced chordates, andvice versa, i.e. trunk structures should occur in the head. The distribution of both rhabdomeric photoreceptors and nephridia in amphioxus conform with this prediction. Equally striking is the involvement of thePax2gene in the development of both the inner ear and nephric ducts in vertebrates. The stolon hypothesis would explain this as a consequence of the common origin of otic capsules and excretory ducts from atrial rudiments: from the paired rudiments of the parent oozooid in the case of the otic capsule (these expressPax2according to recent ascidian data), and from tubular rudiments in the stolon in the case of the excretory ducts.
Ovoviviparity and viviparity in the Diptera
Authors: MEIER RUDOLF , KOTRBA MARION , FERRAR PAUL 
Published: August 2010

ABSTRACTThe taxonomic distribution and evolution of viviparity in Diptera is critically reviewed. The phenomenon ranges from ovoviviparity (eggs deposited at an advanced stage of embryonic development; larva emerges immediately after deposition), through viviparity (larva hatches inside female before deposition) to pupiparity (offspring deposited as pupa). Some Diptera are known to be facultatively viviparous, which is hypothesized to be a step towards the evolution of obligate viviparity. Obligate viviparity is found to comprise unilarviparity (single large larva in maternal uterus) which evolved many times independently, the rare oligolarviparity (more than one but not more than 12 larvae) and multilarviparity (large numbers of developing eggs or larvae in uterus) which is typical for the two largest clades of viviparous Diptera. Unilarviparity is either lecithotrophic (developing larva nourished by yolk of egg) or pseudo‐placental (larva nourished by glandular secretions of mother). Viviparity has clearly evolved on many separate occasions in Diptera. It is recorded in 22 families, and this review identifies at least 61 independent origins of viviparity. Six families appear to have viviparity in their ground‐plan. Some families have a single evolution of viviparity, others multiple evolutions. Guimaraes' model for the evolution of viviparity in Diptera is tested against phylogenetic information and the adaptive significance of viviparity is reviewed in detail. Possible correlations with life‐history parameters (coprophily, parasitism, breeding in ephemeral plant parts, malacophagy and adult feeding habits – especially haematophagy) are analysed critically, as are potential advantages (shorter larval life, less investment in yolk by mother, protection of vulnerable stages, better access to breeding substrates, predation on competitors). Morphological constraints, adaptations and exaptations are reviewed, including the provision of an incubation space for the egg(s), the positioning of the egg(s) in the uterus, and maternal glands. The main morphological adaptations include greater egg size, reduction of egg respiratory filaments, thinning of chorion, modified larval respiratory system and mouthparts, and instar skipping. Female morphology and behaviour is particularly strongly modified for viviparity. The terminalia are shortened, the vagina is more muscular and tracheated, and the ovaries of unilarviparous species have a reduced number of ovarioles with alternate ovulation. Many of the final conclusions are tentative, and a plea is made for more detailed morphological and experimental study of many of the viviparous species. Viviparity in Diptera provides a fascinating example of multiple parallel evolution, and a fertile field for future research.
The ethological analysis of imitation
Authors: MIKLÓSI ÁDÁM 
Published: August 2010

ABSTRACTTheorists and experimental researchers have long debated whether animals are able to imitate. A variety of definitions of imitation have been proposed to describe this complex form of social learning. Experimental research on imitation has often been hampered by either a too loose ‘anthropomorphic’ approach or by too narrow ‘behaviourist’ definitions. At present neither associative nor cognitive theories are able to offer an exhaustive explanation of imitation in animals. An ethological approach to imitation offers a different perspective. By integrating questions on function, mechanism, development and evolution one can identify possible directions for future research. At present, however, we are still far from developing a comprehensive theory of imitation.A functional approach to imitation shows that, despite some evidence for imitative learning in food processing in apes, such learning has not been shown to be involved in the social transmission of either tool‐use skills or communicative signals. Recently developed procedures offer possible ways of clarifying the role of imitation in tool use and visual communication. The role of imitation in explorative play in apes is also investigated and the available data suggest that copying during play might represent a behavioural homologue of human imitation.It is proposed that the ability to copy the behaviour of a companion is under a strong genetic influence in many social species. Many important factors have not been examined experimentally, e.g. the effect of the demonstrator, the influence of attention and memory and the ability to generalize. The potential importance of reinforcement raises the possibility that copying abilities serving divergent functions might be partly under the control of different mechanisms.
The evolution of fitness in life‐history theory
Authors: BROMMER JON E. 
Published: August 2010

ABSTRACTTheory concerning the evolution of life history (the schedule of reproduction and survival) focuses on describing the life history which maximises fitness. Although there is an intuitive link between life history and fitness, there are in fact several measures of the ‘black box’ concept of fitness. There has been a debate in the bio‐mathematical literature on the predictive difference between the two most commonly used measures; intrinsic rate of increase r and net reproductive ratio R0. Although both measures aim to describe fitness, models using one of the measures may predict the opposite of similar models using the other measure, which is clearly undesirable. Here, I review the evolution of these fitness measures over the last four decades, the predictive differences between these measures and the resulting shift of the fitness concept. I focus in particular on some recent developments, which have solved the dilemma of predictive differences between these fitness measures by explicitly acknowledging the game‐theoretical nature of life‐history evolution.
Individual feeding specialisation in shorebirds: population consequences and conservation implications
Authors: DURELL SARAH E. A. LE V. DIT 
Published: August 2010

ABSTRACTIndividual feeding specialisation in shorebirds is reviewed, and the possible mechanisms involved in such specialisations. Any specialisation can be seen as an individual strategy, and the optimum strategy for any given individual will be conditional upon its specific priorities and constraints. Some specialisations are related to social status and some to individual skills. Some are also probably frequency‐dependent. However, most shorebird specialisations are constrained to a large extent by individual morphology, particularly bill morphology. For example, larger birds are able to handle larger prey, and birds with longer bills are able to feed on more deeply buried prey. Sex differences in bill length are uncommon in the Charardriidae, which are surface peckers, but are common in the Scolopacidae, which feed by probing in soft substrates. Sex differences in bill morphology are frequently associated with sex differences in feeding specialisation. There is evidence that different feeding specialisations are associated with different payoffs, in which case the probability of failing to reproduce or of dying will not be distributed equally throughout the population. I consider the population consequences of such feeding specialisations, particularly the different risks and benefits associated with different habitats or diets. I also consider the way in which individuals may differ in their response to habitat loss or change. I suggest that population models designed to predict the effect of habitat loss or change on shorebirds should have the ability to investigate the differential response of certain sections of the population, particularly different ages or sexes, that specialise in different diets or feeding methods.
The functional significance of silk decorations of orb‐web spiders: a critical review of the empirical evidence
Authors: HERBERSTEIN M. E. , CRAIG C. L. , CODDINGTON J. A. , ELGAR M. A. 
Published: August 2010

ABSTRACTA number of taxonomically diverse species of araneoid spiders adorn their orb‐webs with conspicuous silk structures, called decorations or stabilimenta. The function of these decorations remains controversial and several explanations have been suggested. These include:(1)stabilising and strengthening the web;(2) hiding and concealing the spider from predators;(3) preventing web damage by larger animals, such as birds;(4) increasing foraging success; or (5) providing a sunshield. Additionally, they may have no specific function and are a consequence of stress or silk regulation. This review evaluates the strength of these explanations based on the evidence. The foraging function has received most supporting evidence, derived from both correlative field studies and experimental manipulations. This contrasts with the evidence provided for other functional explanations, which have not been tested as extensively. A phylogenetic analysis of the different decoration patterns suggests that the different types of decorations are as evolutionary labile as the decorations themselves: the analysis shows little homology and numerous convergences and independent gains. Therefore, it is possible that different types of decorations have different functions, and this can only be resolved by improved species phylogenies, and a combination of experimental and ultimately comparative analyses.