Rxivist combines preprints from bioRxiv with data from Twitter to help you find the papers being discussed in your field. Currently indexing 73,470 bioRxiv papers from 319,827 authors.
Most downloaded bioRxiv papers, all time
in category zoology
373 results found. For more information, click each entry to expand.
2,489 downloads zoology
We challenge the oft-repeated claim that the beetles (Coleoptera) are the most species-rich order of animals. Instead, we assert that another order of insects, the Hymenoptera, are more speciose, due in large part to the massively diverse but relatively poorly known parasitoid wasps. The idea that the beetles have more species than other orders is primarily based on their respective collection histories and the relative availability of taxonomic resources, which both disfavor parasitoid wasps. Though it is unreasonable to directly compare numbers of described species in each order, the ecology of parasitic wasps - specifically, their intimate interactions with their hosts - allows for estimation of relative richness. We present a simple logical model that shows how the specialization of many parasitic wasps on their hosts suggests few scenarios in which there would be more beetle species than parasitic wasp species. We couple this model with an accounting of what we call the "genus-specific parasitoid-host ratio" from four well-studied genera of insect hosts, a metric by which to generate extremely conservative estimates of the average number of parasitic wasp species attacking a given beetle or other insect host species. Synthesis of our model with data from real host systems suggests that the Hymenoptera may have 2.5 - 3.2x more species than the Coleoptera. While there are more described species of beetles than all other animals, the Hymenoptera are almost certainly the larger order.
2,357 downloads zoology
Abstract: The ascidian tunicate Corella inflata is relatively transparent compared to other solitary tunicates and the circulatory system can be visualized by injecting high molecular weight fluorescein labeled dextran into the beating heart or the large vessels at the ends of the heart. In addition, after staining with neutral red the movement of blood cells can be followed to further define and characterize the circulatory system. The heart is a gently curved tube with a constriction in the middle and extends across the width of the animal. As in other tunicates, pumping is peristaltic and periodically reverses direction. During the abvisceral directional phase blood leaves the anterior end of the heart in two asymmetric vessels that connect to the two sides of the branchial basket (or pharynx), in contrast to the direct connection between the heart and the endostyle seen in the commonly studied tunicate Ciona intestinalis. In Corella inflata blood then flows in both transverse directions through a complex system of ducts in the branchial basket into large ventral and dorsal vessels and then to the visceral organs in the posterior of the animal. During the advisceral phase blood leaves the posterior end of the heart in vessels that repeatedly bifurcate to fan into the stomach and gonads. Blood speed, determined by following individual cells, is high and pulsatory near the heart, but decreases and becomes more constant in peripheral regions. Estimated blood flow volume during one directional phase is greater than the total volume of the animal. Circulating blood cells are confined to vessels or ducts in the visible parts of the animal and retention of high molecular weight dextran in the vessels is comparable to that seen in vertebrates. These flow patterns are consistent with a closed circulatory network. Additional key words: heart, pharynx, branchial basket, blood circulation, blood velocity
2,068 downloads zoology
The phylogenetic placement of the morphologically simple placozoans is crucial to understanding the evolution of complex animal traits. Here, we examine the influence of adding new genomes from placozoans to a large dataset designed to study the deepest splits in the animal phylogeny. Using site-heterogeneous substitution models, we show that it is possible to obtain strong support, in both amino acid and reduced-alphabet matrices, for either a sister-group relationship between Cnidaria and Placozoa, or for Cnidaria and Bilateria (=Planulozoa), also seen in most published work to date, depending on the orthologues selected to construct the matrix. We demonstrate that a majority of genes show evidence of compositional heterogeneity, and that the support for Planulozoa can be assigned to this source of systematic error. In interpreting this placozoan-cnidarian clade, we caution against a peremptory reading of placozoans as secondarily reduced forms of little relevance to broader discussions of early animal evolution.
1,985 downloads zoology
Background: Most species of owls (Strigidae) represent cryptic species and their taxonomic study is in flux. In recent years, two new species of owls of the genus Strix have been described from the Arabian peninsula by different research teams. It has been suggested that one of these species, S. omanensis, is not a valid species but taxonomic comparisons have been hampered by the lack of specimens of S. omanensis, and the poor state of the holotype of S. butleri. Methods: Here we use new DNA sequence data to clarify the taxonomy and nomenclature of the S. butleri complex. We also report the capture of a single S. butleri in Mashhad, Iran. Results: A cytochrome b sequence of S. omanensis was found to be identical to that of the holotype of S. butleri, indicating that the name S. omanensis is best regarded as a junior synonym of S. butleri. The identity of the S. butleri captured in Mashhad, Iran, was confirmed using DNA sequence data. This represents a major (1,400 km) range extension of this species. Conclusions: The population discovered in Oman in 2013 and originally named ‘S. omanensis’ actually represents the rediscovery of S. butleri, which was known from a single specimen and had not been recorded since 1878. The range of S. butleri extends into northeast Iran. Our study augments the body of evidence for the recognition of S. butleri and S. hadorami as separate species and highlights the importance of using multiple evidence to study cryptic owl species.
1,983 downloads zoology
The free-living marine flatworm Macrostomum lignano is a powerful model organism to study mechanisms of regeneration and stem cell regulation due to its convenient combination of biological and experimental properties, including the availability of transgenesis methods, which is unique among flatworm models. However, due to its relatively recent introduction in research, there are still many biological aspects of the animal that are not known. One of such questions is the influence of the culturing temperature on Macrostomum biology. Here we systematically investigated how different culturing temperatures affect the development time, reproduction rate, regeneration, heat shock response, and gene knockdown efficiency by RNA interference in M. lignano. We used marker transgenic lines of the flatworm to accurately measure the regeneration endpoint and to establish the stress response threshold for temperature shock. We found that compared to the culturing temperature of 20°C commonly used for M. lignano, elevated temperatures of 25°C-30°C substantially speed-up the development and regeneration time and increase reproduction rate without detectable negative consequences for the animal, while temperatures above 30°C elicit a heat shock response. We show that altering the temperature conditions can be used to shorten the time required to establish M. lignano cultures, store important lines and optimize the microinjection procedures for transgenesis. Our findings will help to optimize the design of experiments in M. lignano and thus facilitate future research in this model organism.
1,951 downloads zoology
Accurate species delimitation and description are necessary to guide effective conservation management of imperiled species. The Eastern Indigo Snake (Drymarchon couperi) is a large species in North America that is federally-protected as Threatened under the Endangered Species Act. Recently, two associated studies hypothesized that Drymarchon couperi is two species. Here, we use diverse approaches to test the two-species hypothesis for D. couperi. Our analyses reveal that (1) phylogenetic reconstruction in Krysko et al. (2016a) was based entirely on analysis of mitochondrial DNA sequence data, (2) microsatellite data demonstrate significant nuclear gene flow between mitochondrial lineages and a clear isolation-by-distance pattern across the species entire range, and (3) morphological analyses recover a single diagnosable species. Our results reject recent conclusions of Krysko et al. (2016a,b) regarding species delimitation and taxonomy of D. couperi, and we formally place Drymarchon kolpobasileus into synonymy with D. couperi. We suggest inconsistent patterns between mitochondrial and nuclear DNA may be driven by high dispersal of males relative to females. We caution against species delimitation exercises when one or few loci are used without evaluation of contemporary gene flow, particularly species with strong sex-biased dispersal (e.g., squamates) and/or when results have implications for ongoing conservation efforts.
1,529 downloads zoology
Examples of phenotypic convergence in plumage coloration have been reported in a wide diversity of avian taxonomic groups, yet the underlying evolutionary mechanisms driving this phenomenon have received little scientific inquiry. Herein, we document a striking new case of plumage convergence in the Helmeted Woodpecker (Dryocopus galeatus) and explore the possibility of visual mimicry among Atlantic Forest woodpeckers. Our multi-locus phylogenetic analyses unequivocally place D. galeatus within Celeus, indicating the former has subsequently converged in appearance upon the distantly related and syntopic Dryocopus lineatus, to which it bears a remarkable resemblance in plumage coloration and pattern. Although details of the Helmeted Woodpecker’s ecology and natural history are only now beginning to emerge, its smaller size and submissive behavior are consistent with predictions derived from evolutionary game theory models and the interspecific social dominance mimicry hypothesis (ISDM). Moreover, estimates of avian visual acuity suggest that size-related mimetic deception is plausible at distances ecologically relevant to Celeus and Dryocopus foraging behavior. In light of our results, we recommend taxonomic transfer of D. galeatus to Celeus and emphasize the need for detailed behavioral studies that examine the social costs and benefits of plumage convergence to explicitly test for ISDM and other forms of mimicry in these Atlantic Forest woodpecker communities. Future field studies examining potential cases of competitive mimicry should also take into account the mimic’s acoustic behavior, particularly in the presence of putative model species and other heterospecific competitors, as any discontinuity between morphological and behavioral mimicry would likely preclude the possibility of deception.
1,505 downloads zoology
Feathers are one of the defining characteristics of birds and serve a critical role in thermal insulation and physical protection against the environment. Feather structure is known to vary among individuals, and it has been suggested that populations exposed to different environmental conditions may exhibit different patterns in feather structure. We examined both down and contour feathers from two populations of male Torrent Ducks (Merganetta armata) from Lima, Peru, including one high-altitude population from the Chancay-Huaral River at approximately 3500 meters (m) elevation and one low-altitude population from the Chillón River at approximately 1500 m. Down feather structure differed significantly between the two populations. Ducks from the high-altitude population had longer, denser down compared with low-altitude individuals. Contour feather structure varied greatly among individuals but showed no significant difference between populations. These results suggest that the innermost, insulative layer of plumage (the down), may have developed in response to lower ambient temperatures at high elevations. The lack of observable differences in the contour feathers may be due to the general constraints of the waterproofing capability of this outer plumage layer.
1,491 downloads zoology
A taxonomic revision of the cichlid fish genus Petrochromis endemic to Lake Tanganyika. All recognized taxa are herein described, one subspecies is given species status and five new species, viz. P. calliris, P. daidali, P. heffalumpus, P. lisachisme and P. paucispinis, are presented. P. calliris is described from 6 specimens from Cape Mpimbwe, and distinguished primarily by having a high number of both gill rakers on the lower limb of the first gill arch and vertebrae. P. daidali is described from 18 specimens from Cape Mpimbwe, Kansombo and Nkwazi point, and distinguished primarily by males having a labyrinth-like pattern on the head. P. heffalumpus is described from 7 specimens from Cape Mpimbwe, and distinguished primarily by its great size. P. lisachisme is described from 12 specimens from Cape Mpimbwe and Lyamembe, and distinguished primarily by having a high number of dorsal spines. P. paucispinis is described from 4 specimens from Halembe, and distinguished primarily by having a low number of dorsal spines. A revised key to Petrochromis is included. A phylogenetic tree hypothesis of the genus, based on molecular (mitochondrial cytochrome b and d-loop) and morphological results show that jaw position and number of vertebrae are important diagnostic characters. Analyses suggest that the "ancestral Petrochromis" might have looked something like P. orthognathus.
1,484 downloads zoology
A small, juvenile rorqual live-stranded on Qeshm Island, Iran, in the northern Strait of Hormuz (Persian Gulf) in September 2007. Cause of stranding remains unknown but the whale (QE22.09.2007) showed no severe traumatic injuries nor was emaciated. Based on at least seven morphological features, considered diagnostic in combination, allowed a positive identification as Omura's whale Balaenoptera omurai. Features included diminutive body size (397 cm), a large number of ventral grooves (n=82) extending caudad of the umbilicus, a strongly falcate dorsal fin, asymmetric colouration of the head (especially lower jaws) reminiscent of fin whale, including three unilateral dark stripes, faint/incomplete lateral rostral ridges, record low number of short, broad baleen plates (204 in right jaw). The likelihood for the existence of a local B. omurai population in the eastern Persian Gulf or northern Arabian Sea seems higher than the wandering of a very young animal or mother/calf pair from any of the known distant distribution areas in the eastern Indian Ocean or SW Indian Ocean (Madagascar). This is the first record of B. omurai in the NW Indian Ocean.
1,409 downloads zoology
Dwarfism is a condition characterized by shorter stature, at times accompanied by differential skeletal growth proportions relative to the species-typical physical conformation. Causes vary and well-documented in humans as well as certain mammalian species in captive or laboratory conditions, but rarely observed in the wild. Here we report on a single case of apparent dwarfism in a free-ranging adult male Asian elephant (Elephas maximus) in Sri Lanka, comparing physical dimensions to those of other males in the same population, males in other populations, and records in previous literature. The subject was found to have a shoulder height of approximately 195cm, is shorter than the average height of typical mature males, with a body length of 218cm. This ratio of body length to height deviates from what is typically observed, which is approximately 1:1. In absolute height the subject was similar to the attributes of a captive elephant documented in 1955 in Sri Lanka, also said to be a dwarf, however the two specimens differed in the relative proportions of height vs. body length. The subject also exhibits a slight elongation of the skull. We discuss how this phenotype compares to cases of dwarfism in other non-human animals.
1,368 downloads zoology
A new endemic subspecies of gray wolf from the island of Sicily (Italy) is described. While usually considered extinct before 1940, there's some evidence it may have survived up to 1970. This wolf was widespread throughout the island and characterized by a smaller size and a paler coloration than the Apennine wolf (Canis lupus italicus) from Central-Southern Italy. This subspecies is described from a mounted specimen (the holotype) including also a separate skull stored at the Museo di Storia Naturale "La Specola", Universita di Firenze, Italy. The three paratypes are: a) a mounted specimen stored at the "Museo Regionale Interdisciplinare di Terrasini" in Terrasini (PA), Italy, b) a mounted specimen stored at the Museo di Zoologia "Pietro Doderlein", Universita di Palermo, Palermo, Italy, c) a mounted specimen stored at the "Museo Civico Baldassarre Romano" in Termini Imerese (PA), Italy. This new subspecies is described as Canis lupus cristaldii subsp. nov. We suggest "Sicilian wolf" as common name for this new taxon.
1,320 downloads zoology
Centuries of zoological studies amassed billions of specimens in collections worldwide. Genomics of these specimens promises to rejuvenate biodiversity research. The obstacles stem from DNA degradation with specimen age. Overcoming this challenge, we set out to resolve a series of long-standing controversies involving a group of butterflies. We deduced geographical origins of several ancient specimens of uncertain provenance that are at the heart of these debates. Here, genomics tackles one of the greatest problems in zoology: countless old, poorly documented specimens that serve as irreplaceable embodiments of species concepts. The ability to figure out where they were collected will resolve many on-going disputes. More broadly, we show the utility of genomics applied to ancient museum specimens to delineate the boundaries of species and populations, and to hypothesize about genotypic determinants of phenotypic traits.
1,305 downloads zoology
Crustaceans are a morphologically, physiologically and ecologically highly diverse animal group and correspondingly diverse are their reproductive characteristics. They have evolved structural specialities with respect to penis construction, sperm form, sperm storage, fertilization and brood care. Unique in the animal kingdom are safety lines that safeguard hatching and first molting. Further curiosities are dwarf males in parasitic and sessile taxa and bacteria-induced gigantism and infectious feminization in crustacean hosts. Record-breaking features in animals are relative penis length, clutch size, sperm size, chromosome number, viability of resting eggs, and fossil ages of penis, sperm and brooded embryos. These reproductive peculiarities are reviewed and their implication for basic and applied biology is discussed, including the early evolution and diversification of brood care in arthropods, sperm competition and assurance of paternity, posthumous paternity and sustainable male-based fishery, and ecotype changes by man-made pollution.
1,207 downloads zoology
The recognition of cryptic species represents one of the major challenges in current taxonomy and affects our understanding of global diversity. In practice, the process from discovery to acceptance in the scientific community can take an extensive length of time. A prime example is the traditionally difficult taxonomy of the cryptic bumblebee species belonging to the Bombus lucorum-complex. The status of the three European species in the group - Bombus lucorum and the closely related Bombus cryptarum and Bombus magnus - has recently become widely accepted, primarily due to investigations of nucleotide sequences and marking pheromones. In contrast, doubts prevail concerning the validity of species identification based on morphology. As a consequence, our knowledge of the species is muddled in a mire of unreliable and confusing literature data from a large number of authors over the centuries. To clarify this issue, this paper provides a recapitulation of the historical literature and highlights the milestones in the process of species recognition. Further, the possibility of a morphologically based species identification is discussed in the context of new molecular data. Finally, this review outlines the current challenges and provides directions for future issues.
1,189 downloads zoology
Odonata survey was conducted throughout the south-western region of Bangladesh, concentrated on eight districts and the Sundarban (the largest mangrove forest of the world) from August 2014 to August 2016. A total of 50 species under 30 genera belonging to six families were recorded during the study period. Among the 50 species, 31 species belong to Anisoptera whereas 19 species were recorded from the Zygoptera suborder. Libellulidae and Coenagrionidae were most dominant Anisoptetran and Zygopteran families with 28 and 17 species respectively. One Zygoptera species Mortonagrion varalli was newly added to the Odonata fauna of Bangladesh. Among surveyed habitats, species richness was highest in marshland with 38 species followed by 34 species in the lakeside. On the other hand, odonata diversity was lowest in the mangrove area. Our study shows a positive correlation between environmental variables (such as average rainfall, relative humidity, and average temperature) and species richness in the study area. Species richness is highest during monsoon and lowest in winter.
1,162 downloads zoology
The Portuguese man of war, Physalia physalis , is a siphonophore that uses a gas-filled float as a sail to catch the wind. It is one of the most conspicuous, but poorly understood members of the pleuston, a community of organisms that occupy a habitat at the sea-air interface. The development, morphology, and colony organization of P. physalis is very different from all other siphonophores. Here, we propose a framework for homologizing the axes with other siphonophores, and also suggest that the tentacle bearing zooids should be called tentacular palpons. We also look at live and fixed larval and non-reproductively mature juvenile specimens, and use optical projection tomography to build on existing knowledge about the morphology and development of this species. Previous descriptions of P. physalis larvae, especially descriptions of budding order, were often framed with the mature colony in mind. However, we use the simpler organization of larvae and the juvenile specimens to inform our understanding of the morphology, budding order, and colony organization in the mature specimen. Finally, we review what is known about the ecology and lifecyle of P. physalis .
1,158 downloads zoology
Feathers perceived by humans to be vividly colorful are often presumed to be equally conspicuous to other mammals, and thus to present an enhanced predation risk. However, many mammals that prey on adult birds have dichromatic visual systems with only two types of color-sensitive visual receptors (one sensitive to ultraviolet light), rather than the three characteristic of humans and four of most birds. Thus, understanding how these predators perceive color requires quantitative visual modeling. Here, we use a combination of reflectance spectroscopy, multispectral imaging, color vision modelling and visual texture analysis to compare the visual signals available to conspecifics and to mammalian predators for multicolored feathers from the Indian peacock (Pavo cristatus) as well as red and yellow parrot feathers; we also take into account the effects of distance-dependent blurring due to visual acuity. When viewed by tetrachromatic birds against a background of green vegetation, most of the feathers studied had color and brightness contrasts similar to values previously found for ripe fruit. By contrast, when viewed by dichromat mammalian predators, the color and brightness contrasts of these feathers were only weakly detectable and often did not reach detection thresholds for typical viewing distances. We furthermore show that the peacock’s erect train has undetectable color and brightness contrasts and visual textures when photographed against various foliage backgrounds. Given the similarity of photoreceptor sensitivities and feather reflectance properties across relevant species, these findings are consistent with many feathers of similar hue being inconspicuous, and in some cases potentially cryptic, in the eyes of their mammalian predators. These results suggest that many types of colorful feathers are likely to be cryptic to mammals while providing a communication channel perceptible to birds, while emphasizing the importance of understanding diverse sensory receivers in the evolution of animal coloration.
1,153 downloads zoology
The mineral content of complete pet food is regulated to ensure health of the companion animal population. A comprehensive analysis of adherence to these regulatory guidelines has not been conducted. We measured mineral composition of a range of complete wet (n=97) and dry (n=80) canine and feline pet food sold in the UK to assess compliance with EU guidelines. While a majority of foods complied with ≥8 of 11 guidelines (99% and 83% for dry and wet food, respectively), many failed to provide nutritional minimum (e.g. Cu, 20 % of wet food) or exceeded nutritional maximum (e.g. Se, 76% of wet food). Only 6% (6/97) of wet and 39% (34/80) of dry food were fully compliant. Some foods (20-30% of all analysed) had mineral imbalances such as not having the recommended balance of Ca:P (between 1:1 to 2:1). Foods with high fish content had high levels of undesirable metal elements such as arsenic. The study highlights broad non-compliance of a range of popular pet foods sold in the UK with EU guidelines (95% and 61% of wet and dry foods, respectively). If fed exclusively and over an extended period, a number of these pet foods could impact the general health of companion animals.
1,141 downloads zoology
The Euthecosomata Meisenheimer, 1905, holoplanktonic Mollusca with coiled or straight shell were respectively classified in Limacinoidea Gray, 1847 and Cavolinioidea Gray, 1850. In a biometrical analysis (Rampal 1973) a first change had occurd in this last superfamily: the conica shell genera Creseis Rang, 1828, Boasia Dall, 1889, Styliola Gray, 1850 and Hyalocylis Fol, 1875 were gathered into the Creseidae Rampal, 1973. Therefore it was necessary to carry on this study using molecular data. Our recent cladistic and molecular analyses as well as palaeontologic data led to a systematic and phylogenetic revision of the Euthecosomata: the Limacinoidea and of the Creseidae are not monophyletic, the other straight shells Euthecosomata are monophyletic (Corse et al. 2013). The Limacinoidea are invalidated; they are split into three families: Limacinidae Gray, 1847, Heliconoididae n. fam. and Thieleidae n. fam. The Creseidae Rampal, 1973 are validated but at least there are two genera Creseis Rang, 1828 and Boasia Dall, 1889; Styliola and Hyalocylis are considered incertae sedis. In the Cavoliniidae Gray, 1850 there are four subfamily: Cuvierininae Gray, 1850 , Cliinae Jeffreys, 1869 , Diacriinae n. subfam., Cavoliniinae Gray, 1850. The Creseidae Rampal, 1973 and the Cavoliniidae Gray, 1850 belong to the Cavolinioidea Gray, 1850. The species rank of most taxa is confirmed. New genera are proposed or reinstated: Telodiacria n. gen., Hyalaea de Blainville, 1821, Boasia Dall, 1889. The fossil Vaginella Daudin, 1800 is included within the Cuvierininae Gray, 1847. The spiral fossil Altaspiratella Korobkov, 1966 is no longer considered part of the Limacinidae Gray, 1847. Two phylogenetic hypotheses are analysed. According to molecular analyses in COI there is the double emergency of straight shell from two coiled shell lineages; in 28S there is monophyly; this last hypothesis we have kapt is the most parsimonious but requires some reserve and new investigations (Corse et al. 2013).
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