Modern Animals Research Articles

Sponges (Porifera) as living metazoan witnesses from the Neoproterozoic: biomineralization and the concept of their evolutionary success

Terra Nova, 22, 1–11, 2010 Abstract The emergence of the Metazoa can be dated back to the Neoproterozoic Era which comprises the Cryogenian Period during which two major glaciations occurred, the Sturtian and the Varanger-Marinoan. At that time, the phylum Porifera (sponges) evolved as the first animals and developed a hard skeleton. The two classes of siliceous sponges, the Hexactinellida and the Demospongiae, are already provided with the major genetic repertoire and gene regulatory networks that also exist in modern multicellular animals. Besides these metazoan innovations, the siliceous sponges display one autapomorphic character, silicatein, an enzyme which mediates bio-silica formation. Well preserved siliceous sponge fossils have been excavated from the Cambrian Burgess Shale- and Chengjiang deposits. It is concluded that it was the hard skeleton of the siliceous sponges that contributed to the successful evolution and survival of the Porifera during the last 500 Ma.

The granulin gene family: from cancer to dementia

The growth factor progranulin (PGRN) regulates cell division, survival, and migration. PGRN is an extracellular glycoprotein bearing multiple copies of the cysteine-rich granulin motif. With PGRN family members in plants and slime mold, it represents one of the most ancient of the extracellular regulatory proteins still extant in modern animals. PRGN has multiple biological roles. It contributes to the regulation of early embryogenesis, to adult tissue repair and inflammation. Elevated PGRN levels often occur in cancers, and PGRN immunotherapy inhibits the growth of hepatic cancer xenografts in mice. Recent studies have demonstrated roles for PGRN in neurobiology. An autosomal dominant mutation in GRN, the gene for PGRN, leads to neuronal atrophy in the frontal and temporal lobes, resulting in the disease frontotemporal lobar dementia. In this review we will discuss current knowledge of the multifaceted biology of PGRN.

Cockfighting as Cultural Allegory in Early Modern England

This essay examines the ways in which cockfighting in early modern England operates as an allegorical mode, as a trope for conscribing social relations and phenomena as distinct as male subject-formation and the realization of eschatological truth. Focusing on two distinct cockfighting texts (one that promotes the virtues of cockfighting as a sport and another that figures cockfighting as an extension of animal husbandry), the essay maps the range of cultural and behavioral practices that early modern cockfighting discourse makes possible. Located in allegories of the cockfight are conflicting systems of meaning that at once affirm and disrupt anthropological distinctions between human and animal activity and the anthropocentric ideologies that construct such demarcations. Reading the early modern cockfight challenges us to critique how we engage sport, early modern culture, animals, and allegory itself as signifying texts.

Establishing collagen quality criteria for sulphur isotope analysis of archaeological bone collagen

Sulphur isotope measurements of bone collagen from archaeological sites are beginning to be applied more often, yet there are no clear criteria to assess the quality of the collagen and therefore the validity of the sulphur isotope values. We provide elemental data from different methods (DNA sequences, amino acid sequences and mass spectrometric measurements) which are used to establish a reliable system of quality criteria for sulphur isotope analyses of bone collagen. The difference in the amount of sulphur from fish and mammalian collagen type I led to the suggestion to use different criteria to assess the in vivo character of the collagen between these two categories. For establishing quality ranges, the bone collagen of 140 modern animals were analysed. The amount of sulphur in fish and mammalian bone collagen is 0.63 ± 0.08% and 0.28 ± 0.07%, respectively. Based on these results we define for mammalian bone collagen an atomic C:S ratio of 600 ± 300 and an atomic N:S ratio of 200 ± 100, and for fish bone an atomic C:S ratio of 175 ± 50 and an atomic N:S ratio of 60 ± 20. These quality criteria were then applied to 305 specimens from different archaeological contexts.

Reconstructing faunal migrations using intra-tooth sampling and strontium and oxygen isotope analyses: a case study of modern caribou ( Rangifer tarandus granti)

Isotopic analyses of incrementally developed dental tissues can be used to reveal patterns of movement and diet in animals. However, the suitability of these methods for the reconstruction of herd movements has not yet been demonstrated. Inter-individual behavioural and isotopic variability at the herd scale, and the implications for archaeological and palaeocological applications, can only be demonstrated through the testing of modern animals. In this pilot study, dual-element isotopic profiles were created from incrementally developed dental tissues of five individuals selected from a modern herd of migratory Alaskan caribou ( Rangifer tarandus granti). Enamel from second and third molars from the individuals was sequentially sampled in order to reconstruct time-series isotopic profiles. Variation in the strontium ( 87Sr/ 86Sr) and oxygen ( δ 18O CARB) isotope ratios of sequentially sampled enamel were compared to documented herd movement patterns and local geological and environmental conditions. Four individuals displayed the same general trends, although absolute isotopic values varied. One individual displays a very different trend and may represent a behavioural outlier or an immigrant from a semi-domesticated reindeer herd. The implications of this study to herd movement reconstruction in the past are discussed.

Modelling the Transport of Nutrients in Early Animals

The single-celled ancestors of multi-cellular animals (metazoans) did not need to transport nutrients between cells, but this ability is vital for modern animals. How could intercellular nutrient transport have begun? And how did this influence the early evolution of animals? In this hypothesis, I suggest that nutrients could have passed directly between the cytoplasm of conjoined cells in early compacted cell-balls, along the plane of the closed epithelium. This would have limited early animals to the size and form of modern embryos. The mechanisms that indirectly transport nutrients between discrete cells, via the extracellular fluid within the body-space, are modelled to have evolved sequentially; so comparison of nutrient transport processes could provide evidence of any early divergences of phyla. When the last of the indirect intercellular transport processes for essential nutrients had been developed, the extracellular fluid within the body-space would have contained all necessary nutrients. Then the epithelium could have greatly expanded, and cells lived and divided within the body-space. This development of nutrient transport processes would have enabled animals to greatly increase in size and complexity.

Modern Animals: From Subjects to Agents in Literary Studies

AbstractAdvancing theories of literature and animality requires both recognizing the failures of traditional humanist models that separate and elevate people over all "things" animal as well as identifying and developing alternative forms. Along with providing fresh readings and important insights about representative texts in the literary canon, two new books—Carrie Rohman's Stalking the Subject: Modernism and the Animal (2009) and Philip Armstrong's What Animals Mean in the Fiction of Modernity (2008)—illustrate how this challenge is being addressed. Strategically, Rohman works within established textual forms of modern humanity to expand the parameters of who counts as a subject in literature. Armstrong takes a more tactical approach, extending ideas of nonhuman agency in order to frame this very discourse of representation itself as a problem that modern narrative forms bring to a crisis. What thus emerges is a range of textual actions and actors that exceed traditional humanist calculations of the subject. Together these studies frame questions with broader implications for humanistic scholarship: how do textual forms of subjectivity, even of discourse, become historical, and historically flexible, through animal involvements in literary representations?

An Integrated View of Precambrian Eumetazoan Evolution

The eumetazoan clade of modern animals includes cnidarians, acoels, deuterostomes, and protostomes. Stem group eumetazoans evolved in the late Neoproterozoic, possibly before the Marinoan glaciation, according to a variety of different kinds of evidence. Here, we combine this evidence, including paleontological observations, results from molecular and morphological phylogeny, and paleoecological considerations, with deductions from the organization of the gene regulatory networks that underlie development of the bilaterian body plan. Eumetazoan body parts are morphologically complex in detail, and modern knowledge of gene regulatory network structure shows that the control circuitry required for their development is hierarchical and multilayered. Among the consequences is that the kernels of the networks that control the early allocation of spatial developmental fate canalize the possibilities of downstream evolutionary change, a mechanism that can account for the appearance of distinct clades in early animal evolution. We reconstruct preeumetazoan network organization and consider the process by which the eumetazoan regulatory apparatus might have been assembled. A strong conclusion is that the evolutionary process generating the genomic programs responsible for developmental formulation of basic eumetazoan body plans was in many ways very different from the evolutionary changes that can be observed at the species level in modern animals.

A primitive social circuit: vasotocin–substance P interactions modulate social behavior through a peripheral feedback mechanism in goldfish

At its core, the polyvagal theory proposes that peptides affect simple social behaviors through influences on hindbrain autonomic processes. To test this mechanism, we compared the effects of fore- and hindbrain infusions of vasotocin (VT) on social approach behavior in goldfish. VT infusions into the 4th ventricle, which ink infusions verified did not move rostrally to the forebrain, inhibited social approach at a lower dose than did infusions into the 3rd ventricle, which did diffuse to the hindbrain. Thus, VT actions in the hindbrain appear to modulate this simple social behavior. We then identified a population of substance P (SP)-immunoreactive cells in the hindbrain that are encapsulated by putative VT terminals, and determined that those cells project to the periphery. Injecting SP peripherally, as with infusing VT centrally, inhibited social approach, and peripheral injections of an SP antagonist, but not central infusions, abolished the behavioral effects of central VT infusions. We therefore propose that VT inhibits social approach by activating SP cells in the hindbrain, which then induce changes in body state that feed back to the brain. Central VT infusions did not inhibit feeding, suggesting that this VT mechanism selectively affects appetitive social responses. Because VT projections to the hindbrain are highly conserved in vertebrates, influences on peripheral feedback processes like the one we have described in goldfish may reflect how VT affected simple social behaviors in ancestral vertebrates and thus preadapted members of this peptide family to play increasingly complex roles in social and emotional regulation in modern animals.

Models on Snowball Earth and Cambrian explosion: A synopsis

During the late Proterozoic from 1000 to 542 Ma, the Earth is thought to have been frozen at least during two times: in the Sturtian (715–680 Ma) and in the Marinoan (680–635 Ma) global glaciations. Following the Marinoan Snowball Earth, large multi-cellular animals of the Ediacara fauna flourished as a prelude to the Phanerozoic world. Here we summarize the most popular models on the cause and cessation of Snowball Earth. Episodic decrease of greenhouse gas occurs through the effect of erosion and weathering promoted by either mountain building or by an increase in the coastlines during the break-up of supercontinents. Effects on the globe caused by true polar wander, eruption of voluminous flood basalts, or dramatic reduction in planetary obliquity can also lead to ice ages and mass extinction. A radically revised concept based on Earth's magnetic intensity has also been proposed, which explains the true polar wander through a quasi-polar dynamo model. The ‘switch-on’ and ‘switch-off’ of the Earth's strong dynamo can lead to the onset and disappearance of the Snowball Earth. The galactic model infers that gamma ray burst associated with starburst creates huge amounts of clouds which would cut off sun rays and freeze the Earth. The Snowball Earth event is considered to have exerted a significant control on the subsequent revolutionary changes in the evolution of life forms. Although according to the biological clock, extensive re-organisation of genome is thought to have been completed by around 900 Ma, the evolution of modern life in Cambrian occurred only after the geochemical bridge was in place with elevated oxygen and nutrient levels in lakes that developed within continental rifts where the hydrothermal system in the granitic basement created the chemical environment enriched in Ca 2+, Fe 2+, V, Mo, HCO 3, phosphate and other elements required for building the skeleton and bone of the first modern animals. With cosmic radiation exerting a significant control on the mutation, the Neoproterozoic Earth history illustrates the possible link from Galaxy to the genome level.

Reconstructing ancestral genome content based on symmetrical best alignments and Dollo parsimony

Gene duplications and losses (GDLs) are important events in genome evolution. They result in expansion or contraction of gene families, with a likely role in phenotypic evolution. As more genomes become available and their annotations are improved, software programs capable of rapidly and accurately identifying the content of ancestral genomes and the timings of GDLs become necessary to understand the unique evolution of each lineage. We report EvolMAP, a new algorithm and software that utilizes a species tree-based gene clustering method to join all-to-all symmetrical similarity comparisons of multiple gene sets in order to infer the gene composition of multiple ancestral genomes. The algorithm further uses Dollo parsimony-based comparison of the inferred ancestral genes to pinpoint the timings of GDLs onto evolutionary intervals marked by speciation events. Using EvolMAP, first we analyzed the expansion of four families of G-protein coupled receptors (GPCRs) within animal lineages. Additional to demonstrating the unique expansion tree for each family, results also show that the ancestral eumetazoan genome contained many fewer GPCRs than modern animals, and these families expanded through concurrent lineage-specific duplications. Second, we analyzed the history of GDLs in mammalian genomes by comparing seven proteomes. In agreement with previous studies, we report that the mammalian gene family sizes have changed drastically through their evolution. Interestingly, although we identified a potential source of duplication for 75% of the gained genes, remaining 25% did not have clear-cut sources, revealing thousands of genes that have likely gained their distinct sequence identities within the descent of mammals. Query server, source code and executable are available at http://kosik-web.mcdb.ucsb.edu/evolmap/index.htm .

Stable Isotope Ratios in Hair and Teeth Reflect Biologic Rhythms

Biologic rhythms give insight into normal physiology and disease. They can be used as biomarkers for neuronal degenerations. We present a diverse data set to show that hair and teeth contain an extended record of biologic rhythms, and that analysis of these tissues could yield signals of neurodegenerations. We examined hair from mummified humans from South America, extinct mammals and modern animals and people, both healthy and diseased, and teeth of hominins. We also monitored heart-rate variability, a measure of a biologic rhythm, in some living subjects and analyzed it using power spectra. The samples were examined to determine variations in stable isotope ratios along the length of the hair and across growth-lines of the enamel in teeth. We found recurring circa-annual periods of slow and fast rhythms in hydrogen isotope ratios in hair and carbon and oxygen isotope ratios in teeth. The power spectra contained slow and fast frequency power, matching, in terms of normalized frequency, the spectra of heart rate variability found in our living subjects. Analysis of the power spectra of hydrogen isotope ratios in hair from a patient with neurodegeneration revealed the same spectral features seen in the patient's heart-rate variability. Our study shows that spectral analysis of stable isotope ratios in readily available tissues such as hair could become a powerful diagnostic tool when effective treatments and neuroprotective drugs for neurodegenerative diseases become available. It also suggests that similar analyses of archaeological specimens could give insight into the physiology of ancient people and animals.

Palaeoenvironmental and palaeogeographical implications of modern Macaronichnus segregatis-like traces in foreshore sediments on the Pacific coast of central Japan

Traces produced by modern animals provide useful information for our understanding of comparable trace fossils. This paper reports on a polychaete worm Euzonus producing traces which fall within the definition of the ichnotaxon Macaronichnus segregatis. Observation on the wave-dominated Pacific sandy coast of central Japan revealed that this animal and its trace occur exclusively in sediments of the mid-foreshore portion of the beach. Owing to such a limited occurrence of the modern trace, the ichnofossil M. segregatis might be useful as an indicator of mid-foreshore environment. The longer axes of modern M. segregatis-like traces on a bedding plane are arranged perpendicular to the shoreline and accordingly, its fossil counterpart can be utilized for reconstructions of the ancient shoreline orientation. In support of this assumption, a similar mode of M. segregatis occurrence is reported from Pleistocene shallow marine deposits in Japan.

Predicting woodrat (Neotoma) responses to anthropogenic warming from studies of the palaeomidden record

AbstractAim The influence of anthropogenic climate change on organisms is an area of great scientific concern. Increasingly there is recognition that abrupt climate transitions have occurred over the late Quaternary; studies of these shifts may yield insights into likely biotic responses to contemporary warming. Here, we review research undertaken over the past decade investigating the response of Neotoma (woodrats) body size and distribution to climate change over the late Quaternary (the last 40,000 years). By integrating information from woodrat palaeomiddens, historical museum specimens and field studies of modern populations, we identify potential evolutionary responses to climate change occurring over a variety of temporal and spatial scales. Specifically, we characterize climatic thresholds in the past that led to local species extirpation and/or range alterations rather than in situ adaptation, and apply them to anticipate potential biotic responses to anthropogenic climate change.Location Middens were collected at about 55 sites scattered across the western United States, ranging from about 34 to 46° N and about 104 to 116° W, respectively. Data for modern populations were drawn from studies conducted in Death Valley, California, Missoula, Montana and the Sevilleta LTER site in central New Mexico.Methods We analysed faecal pellets from midden series collected at numerous cave sites across the western United States. From these we estimated body mass using techniques validated in earlier studies. We compared body size fluctuations at different elevations in different regions and integrated these results with studies investigating temperature–body size tradeoffs in modern animals. We also quantify the rapidity of the size changes over the late Quaternary to estimate the evolutionary capacity of woodrats to deal with predicted rates of anthropogenic climate change over the next century.Results We find remarkable similarities across the geographical range to late Quaternary climate change. In the middle of the geographical range woodrats respond in accordance to Bergmann's rule: colder climatic conditions select for larger body size and warmer conditions select for smaller body size. Patterns are more complicated at range boundaries, and local environmental conditions influence the observed response. In general, woodrat body size fluctuates with approximately the same amplitude and frequency as climate; there is a significant and positive correlation between woodrat body size and generalized climate proxies (such as ice core records). Woodrats have achieved evolutionary rates of change equal to or greater than those needed to adapt in situ to anthropogenic climate change.Main conclusions In situ body size evolution is a likely outcome of climate change, and such shifts are part of a normal spectrum of adaptation. Woodrats appear to be subject to ongoing body size selection in response to fluctuating environmental conditions. Allometric considerations suggest that these shifts in body size lead to substantial changes in the physiology, life history and ecology of woodrats, and on their direct and indirect interactions with other organisms in the ecosystem. Our work highlights the importance of a finely resolved and long‐term record in understanding biotic responses to climatic shifts.

Bushmen Cave Paintings of Ornithopod Dinosaurs: Paleolithic Trackers Interpret Early Jurassic Footprints

Remnants of Bushmen cave paintings showing representations of dinosaurs evidently reconstructed from footprints, trackways and skeletal remains have been found in Lesotho. This is a region of prolific dinosaur trackways preserved in Lower Jurassic sedimentary rocks, and the Bushman culture is renowned for extraordinary skill in the tracking of modern animals. It is probable that the track and trackmaker representations depict ornithopod dinosaurs. The track drawings are accurate, and the trackmaker representations show that Bushman artists anticipated modern reconstructions of bipedal dinosaurs and produced depictions that are more realistic than many paleontological reconstructions that endured until quite recently.

Changes in mercury and cadmium concentrations and the feeding behaviour of beluga ( Delphinapterus leucas) near Somerset Island, Canada, during the 20th century

Beluga ( Delphinapterus leucas) continues to be an important food species for Arctic communities, despite concerns about its high mercury (Hg) content. We investigated whether Hg and cadmium (Cd) concentrations had changed during the 20th century in beluga near Somerset Island in the central Canadian Arctic, using well-preserved teeth collected from historical sites (dating to the late 19th century and 1926–1947) and during subsistence hunts in the late 1990s. Mercury concentrations in both historical and modern teeth were correlated with animal age, but 1990s beluga exhibited a significantly more rapid accumulation with age than late 19th century animals, indicating that Hg concentrations or bioavailability in their food chain had increased during the last century. The geometric mean tooth Hg concentration in modern 30 year old animals was 7.7 times higher than in the late 19th century, which corresponds to threefold higher concentrations in muktuk and muscle. Teeth from 1926 to 1947 were similar in Hg content to the late 19th century, suggesting that the increase had occurred sometime after the 1940s. In contrast, tooth Cd was not correlated with animal age and decreased during the last 100 years, indicating that anthropogenic Cd was negligible in this population. Late 19th century beluga displayed a greater range of prey selection (tooth δ 15N values: 15.6–20.5‰) than modern animals ( δ 15N: 17.2–21.1‰). To prevent this difference from confounding the temporal Hg comparison, the Hg–age relationships discussed above were based on historical animals, which overlapped isotopically with the modern group. Tooth δ 13C also changed to isotopically more depleted values in modern animals, with the most likely explanation being a significant shift to more pelagic-based feeding. Industrial Hg pollution is a plausible explanation for the recent Hg increase. However, without further investigation of the relationship between the range exploitation of modern beluga and their possible exposure to regional marine food chains with (naturally) higher Hg contents than their historical counterparts, we cannot unequivocally conclude that the increase was anthropogenically driven.

The Emergence of Conservation Behavior

The Emergence of Conservation Behavior

Origins of Bilateral Symmetry: Hox and Dpp Expression in a Sea Anemone

Over 99% of modern animals are members of the evolutionary lineage Bilateria. The evolutionary success of Bilateria is credited partly to the origin of bilateral symmetry. Although animals of the phylum Cnidaria are not within the Bilateria, some representatives, such as the sea anemone Nematostella vectensis, exhibit bilateral symmetry. We show that Nematostella uses homologous genes to achieve bilateral symmetry: Multiple Hox genes are expressed in a staggered fashion along its primary body axis, and the transforming growth factor-beta gene decapentaplegic (dpp) is expressed in an asymmetric fashion about its secondary body axis. These data suggest that bilateral symmetry arose before the evolutionary split of Cnidaria and Bilateria.

EARLY JURASSIC HYDROTHERMAL VENT COMMUNITY FROM THE FRANCISCAN COMPLEX, CALIFORNIA

The Figueroa sulfide deposit located in Franciscan Complex rocks in the San Rafael Mountains, California, contains the only known Jurassic hydrothermal vent community. Based on radiolarian biostratigraphy it is Pliensbachian (early Jurassic) in age. The Figueroa fossil organisms lived at a deepwater, high temperature vent site located on a mid-ocean ridge or seamount at an equatorial latitude. The vent site was then translated northeastward by the motion of the Farallon Plate and was subsequently accreted to its present location. The vent fossils are preserved as molds of pyrite and there is no remaining shell or tube material. The fossil assemblage is specimen rich, but of low diversity, and comprises, in order of decreasing abundance, vestimentiferan worm tubes, rhynchonellide brachiopods (Anarhynchia cf. gabbi), and trochoidean gastropods (Francisciconcha maslennikovi new genus and species). These fossils represent only primary consuming organisms, some of which may have had chemosynthetic microbial endosymbionts, like many modern dominant vent animals. The Figueroa vent assemblage shares vestimentiferan tube worms and gastropods with other fossil and modern vent communities, but is unique in having rhynchonellide brachiopods. It shares this feature with contemporary Mesozoic cold seep communities. Many other taxonomic groups found at modern vent sites are missing from the Figueroa assemblage. The presence of vestimentiferan tube worm fossils in the Figueroa deposit is at odds with the supposed time of origin of the modern vestimentiferans (∼100 Ma), based on molecular data.

Digital photodensitometry: a reliable and accessible method for measuring bone density

Taphonomic analyses are frequently reliant on bone structural density data, which are used as a proxy measure of bone strength. Methods used to obtain these data are often either destructive, or expensive. Consequently the data available tend to be based on only a small number of animals. A method that can measure the bone density of a large number of animals at a comparatively low cost is therefore desirable. This paper sets out such a method, based on photodensitometry. Bones are radiographed, the images are converted into digital files, standardised, and their optical density measured. These data are combined with metrical information to produce a measurement that relates to a specimen's bone density. The method is shown to be repeatable and comparable to (or perhaps better than) Dual Energy X-ray Absorptiometry (DEXA) in terms of accuracy. It also does not suffer from the methodological problems regarding the cross-sectional area of the specimen that are associated with DEXA. Density data produced by the method described here have successfully been used in a taphonomic analysis of the faunal assemblage from the site of Çatalhöyük, Turkey, shedding light on the use of different types of space by the ancient inhabitants of the site. The same data have cast doubt on the common assumption that the bone density of modern animals can act as an analogue for that of archaeological animals.