Functional niche partitioning in Therizinosauria provides new insights into the evolution of theropod herbivory

Dietary specialization is generally considered to be a crucial factor in driving morphological evolution across extant and extinct vertebrates. The ability to adapt to a specific diet and to exploit ecological niches is thereby influenced by functional morphology and biomechanical properties. Differences in functional behaviour and efficiency can therefore allow dietary diversification and the coexistence of similarly adapted taxa. Therizinosauria, a group of secondarily herbivorous theropod dinosaurs, is characterized by a suite of morphological traits thought to be indicative of adaptations to an herbivorous diet. Digital reconstruction, theoretical modelling and computer simulations of the mandibles of therizinosaur dinosaurs provides evidence for functional niche partitioning in adaptation to herbivory. Different mandibular morphologies present in therizinosaurians were found to correspond to different dietary strategies permitting coexistence of taxa. Morphological traits indicative of an herbivorous diet, such as a downturned tip of the lower jaw and an expanded postdentary region, were identified as having stress mitigating effects. The more widely distributed occurrence of these purported herbivorous traits across different dinosaur clades suggests that these features also could have played an important role in the evolution and acquisition of herbivory in other groups.     

Mitochondrial DNA offers unique insights into invasion history of the common starling

Mitochondrial DNA (mtDNA) can be a powerful genetic marker for tracing origins and history of invasive populations. Here, we use mtDNA to address questions relevant to the understanding of invasion pathways of common starlings (Sturnus vulgaris) into Western Australia (WA) and discuss the utility of this marker to provide information useful to invasive species management. Mitochondrial sequence data indicate two geographically restricted genetic groups within Australia. Evidence of dispersal from genetically distinct sources outside the sampled range of starlings in Australia suggests increased vigilance by management agencies may be required to prevent further incursions from widely separated localities. Overall, genetic diversity in Australia was lower than in samples from the native range. Within Australia, genetic diversity was lowest in the most recently colonized area in the west, indicating that demographic bottlenecks have occurred in this area. Evidence of restricted dispersal between localities on the edge of the range expansion (ERE) in WA and other Australian sampling localities suggests that localized control within the ERE may be effective in preventing further range expansion. Signatures of spatial and demographic expansion are present in mismatch analyses from sampling localities located at the ERE, but neutrality indices did not support this finding, suggesting that the former may be more sensitive to recent expansion. Additionally, mismatch analyses support the presence of admixture, which is likely to have occurred pre-introduction. We compare our findings with those from a microsatellite study of the same samples and discuss how the mtDNA analyses used here offer valuable and unique insights into the invasion history of introduced species.     

Effects of body size, age and maturity stage on diet in a large shark: ecological and applied implications

Ontogenetic diet shifts are a widespread phenomenon among vertebrates, although their relationships with life history traits are poorly known. We analyzed the relative importance of body size, age and maturity stage as determinants of the diet of a marine top predator, the copper shark, Carcharhinus brachyurus, by examining stomach contents using a multiple-hypothesis modeling approach. Copper sharks shifted their diet as size and age increased and as they became sexually mature, incorporated larger prey as they grew, and had a discrete shift in diet with body size, with only individuals larger than ≈200 cm total length able to prey on chondrichthyans. Body size was the most important trait explaining the consumption of chondrichthyans, while age determined the consumption of pelagic teleosts. Pelagic teleosts were consumed mostly by medium-aged sharks, a result, probably, of a risk-reducing feeding strategy at young ages coupled with either a senescence-related decline in performance or a change in sensory capabilities as sharks age. Copper sharks of all sizes were able to cut prey in pieces, implying that gape limitation (i.e., the impossibility of eating prey larger than a predator’s mouth) did not play a role in producing the diet shift. Our results suggest that, contrary to the current practice of setting minimum but not maximum size limits in catches, any plan to conserve or restore the ecological function of sharks, through their predatory control of large prey, should aim to maintain the largest individuals.     

Karyotypic evolution of hapalomys inferred from chromosome painting: a detailed characterization contributing new insights into the ancestral murinae karyotype

We report on the construction of a comparative chromosome map between the emblematic laboratory rat, Rattus norvegicus (RNO), and Delacour's Marmoset rat, Hapalomys delacouri (HDE), based on cross-species fluorescence in situ hybridization with R. norvegicus painting probes. Sixteen R. norvegicus chromosomes (RNO 3-6, 8, 10-15, 17-20, and X) were retained in their entirety (as a conserved block or as a single chromosome) in the H. delacouri genome. The remaining 5 R. norvegicus chromosomes (RNO 1, 2, 7, 9, and 16) produced 2 signals in the H. delacouri karyotype. Our analysis allowed the detection of an X-autosome translocation between RNO X and 11 that occurred convergently in an unrelated species, Bandicota savilei, and a single B chromosome that accounts for the 2n = 48 karyotype observed in this specimen. In total, the rat chromosome paints revealed 27 segments of conserved synteny in H. delacouri. The analysis showed 7 NOR bearing pairs in H. delacouri (HDE 1, 3, 6, 7, 8, 10, and 13) and the occurrence of an interstitial telomeric signal at the centromeric regions of 8 H. delacouri chromosomes (HDE 3, 10, 11, 12, 13, 16, 19, and 22). These data, together with published comparative maps, enabled a revision of the previously postulated murine ancestral condition suggesting that it probably comprised a wholly acrocentric karyotype with 2n = 46-50.     

Comparative studies on the life history of Angiostrongylus mackerrasae Bhaibulaya, 1968 and Angiostrongylus cantonensis (Chen, 1935)

The life history of A. mackerrasae was found to differ from that of A. cantonensis as follows: (1) the moulting times of A. cantonensis in the definitive host occurred a few days earlier than those of A. mackerrasae; (2) the growth rate of A. cantonensis was more rapid than that of A. mackerrasae. However, there were no differences in the migratory pattern of the third-stage larvae of both species in experimentally-infected definitive hosts. It is concluded that Mackerras & Sandars (1955) described the life history of A. mackerrasae and not A. cantonensis.     

Manipulation of Sod1 expression ubiquitously, but not in the nervous system or muscle, impacts age-related parameters in Drosophila

Superoxide dismutase 1 (SOD1) is an important antioxidant previously shown to impact life span in Drosophila. We examined the consequences of manipulating Sod1 expression throughout the body or in the nervous system or musculature on life span and age-related locomotor impairment (ARLI) in Drosophila. Ubiquitous overexpression of SOD1 extended life span but did not substantially forestall ARLI, whereas ubiquitous knock-down of Sod1 shortened life span and accelerated ARLI. Interestingly, neither overexpression of Sod1 nor expression of Sod1 RNAi in the nervous system or muscle altered life span or ARLI. Our studies suggest that the control of reactive oxygen species by SOD1 in tissues other than the nervous system and musculature support life span and ARLI in Drosophila.     

秦岭细鳞鲑群体遗传结构

秦岭细鳞鲑(Brachymystax lenok tsinlingensis)是秦岭地区特有鱼类,近年来由于环境恶化及人类活动的加剧,已对其造成严重影响,种群处于濒危状态,因此研究秦岭细鳞鲑的群体遗传结构、演化历史、分布动态等对其进行有效保护具有重要意义。本研究用线粒体D-loop区序列对秦岭地区6个群体(n=112)进行了遗传结构和群体演化分析。D-loop区扩增出的891bp序列在112个个体中,检测到42个变异位点,共26个单倍型;碱基序列总的单倍型多样度较高为0.883,核苷酸多样度为0.00799。AMOVA分析显示,60.05%的分子差异位于群体内,39.95%的分子差异位于群体间,Fst值统计检验表明,除那布大河群体与漳河群体和千河群体之间差异不显著之外,其余两两群体之间Fst值统计检验均为显著。系统树和单倍型网络图分析表明,6个地理群体的单倍型按照渭河上游和渭河中游两个河段形成两个大的类群,且5个群体共享一个单倍型H2,表明这些群体具有相同的演化历史,为同一个祖先群体演化而来。中性检验和歧点分布显示,秦岭细鳞鲑种群大小保持相对稳定,未经历明显的种群扩张。同时建议将渭河上游秦岭细鳞鲑群体作为一个整体进行重点保护。     

Structural insights into the histidine trimethylation activity of EgtD from Mycobacterium smegmatis

EgtD is an S-adenosyl-l-methionine (SAM)-dependent histidine N,N,N-methyltransferase that catalyzes the formation of hercynine from histidine in the ergothioneine biosynthetic process of Mycobacterium smegmatis. Ergothioneine is a secreted antioxidant that protects mycobacterium from oxidative stress. Here, we present three crystal structures of EgtD in the apo form, the histidine-bound form, and the S-adenosyl-l-homocysteine (SAH)/histidine-bound form. The study revealed that EgtD consists of two distinct domains: a typical methyltransferase domain and a unique substrate binding domain. The histidine binding pocket of the substrate binding domain primarily recognizes the imidazole ring and carboxylate group of histidine rather than the amino group, explaining the high selectivity for histidine and/or (mono-, di-) methylated histidine as substrates. In addition, SAM binding to the MTase domain induced a conformational change in EgtD to facilitate the methyl transfer reaction. The structural analysis provides insights into the putative catalytic mechanism of EgtD in a processive trimethylation reaction.     

Long bone microstructure gives new insights into the life of pachypleurosaurids from the Middle Triassic of Monte San Giorgio,Switzerland/Italy

The long bone microstructure of four pachypleurosaurid taxa from Monte San Giorgio (Switzerland/Italy) was studied. Pachypleurosaurids are secondarily aquatic reptiles that lived during the Middle Triassic in varying marine environments of the Tethys. All four pachypleurosaurids show high compactness values in their long bones based on a thick cortex and a calcified cartilaginous core, which remains in the medullary region throughout the ontogeny. Parts or even the entire embryonic bone layer composed of a mixture of woven-fibered bone tissue and parallel-fibered bone tissue is preserved in both pachypleurosaurid genera. The rest of the cortex consists of lamellar-zonal bone tissue type. Differences in the microstructure of the bones between the pachypleurosaurids are reflected in the occurrence of remodelling processes, which, if present, affect the innermost growth marks of the cortex or the calcified cartilaginous core. Further variation is present in the spacing pattern of the growth cycles, as well as in the degree of vascularisation of the lamellar-zonal bone tissue type. Our data on the microstructure of the long bones support previous studies on morphology and facies distribution, which indicated different habitats and adaptation to a secondary aquatic lifestyle for each pachypleurosaurid taxon. Life history data furthermore reflect different longevities and ages at sexual maturity. The bone histological data of the stratigraphically youngest and oldest pachypleurosaurid species might indicate possible climate-dependant reproductive seasons similar to Recent lacertilian squamates.     

Induction of embryonic dormancy in the Calanoid copepod Acartia hudsonica: proximal cues and variation among individuals

In this study of Acartia hudsonica, the change in egg types from subitaneous eggs to dormant eggs was investigated. Temperature and photoperiod were hypothesized to act as the proximal environmental cues inducing this population to produce dormant eggs, and the variation in the dormant egg responses of individual females was quantified. Some field-collected females produced some dormant eggs early in the spring (March and April), but most of the switch to dormant eggs occurred in late June. Short-term experiments showed that increased temperatures increased the percentage of dormant eggs produced, whereas increased length of day did not. Long-term experiments showed a different pattern from short-term experiments, indicating that duration of exposure to particular temperatures or photoperiods may influence dormant egg production. Under certain conditions, it appeared that nearly all copepods were capable of producing dormant eggs, although identical experimental conditions did not affect all individuals similarly. In several experiments that revealed a significant treatment effect, between 42% and 85% of the variance detected could be attributed to variation among individuals. Also, the fraction of individuals producing dormant eggs generally increased with increasing water temperature. In Narragansett Bay, A. hudsonica appears to produce dormant eggs primarily in response to increased water temperatures although an effect of photoperiod could not be ruled out. Furthermore, individual responses vary greatly. Appreciation of such variation in an important life history trait, such as embryonic dormancy, is important in understanding how this population may be adapted to its environment.     

The life history of Sulcascaris sulcata (Nematoda: Ascaridoidea), a parasite of marine molluscs and turtles

Berry G. N. and Cannon L. R. G. 1981. The life history of Sulcascaris sulcata (Nematoda: Ascaridoidea), a parasite of marine molluscs and turtles. International Journal for Parasitoiogy11: 43–54. The morphology, development and hatching of Sulcascaris sulcata eggs are described. Two moults occurred in the egg. Third stage larvae spontaneously hatched and were found to develop in marine bivalves and gastropods. Larvae grew steadily and after three to four months, when about 5 mm long, they moulted to fourth stage larvae characteristic of natural infections in bivalves from commercial catches. Experimentally, when fed to laboratory-reared Caretta caretta, the fourth stage larvae first attached at the oesophago-gastric junction where they moulted to adults in 7–21 days. Subsequent growth to mature adults was obtained by at least 5 months after infection. It is suggested that under natural conditions the life history may take up to 2 years to complete. These findings are discussed in relation to the predatory mode of feeding and the breeding habits of C. caretta and the significance of a possible health hazard to man.     

Structural insights into substrate specificity of crotonase from the n-butanol producing bacterium Clostridium acetobutylicum

Crotonase from Clostridium acetobutylicum (CaCRT) is an enzyme that catalyzes the dehydration of 3-hydroxybutyryl-CoA to crotonyl-CoA in the n-butanol biosynthetic pathway. To investigate the molecular mechanism underlying n-butanol biosynthesis, we determined the crystal structures of the CaCRT protein in apo- and acetoacetyl-CoA bound forms. Similar to other canonical crotonase enzymes, CaCRT forms a hexamer by the dimerization of two trimers. A crystal structure of CaCRT in complex with acetoacetyl-CoA revealed that Ser69 and Ala24 to be signature residues of CaCRT, which results in a distinct ADP binding mode wherein the ADP moiety is bound at a different position compared with other crotonases. We also revealed that the substrate specificity of crotonase enzymes is determined by both the structural feature of the α3 helix region and the residues contributing the enoyl-CoA binding pocket. A tight formed α3 helix and two phenylalanine residues, Phe143 and Phe233, aid CaCRT to accommodate crotonyl-CoA as the substrate. The key residues involved in substrate binding, enzyme catalysis and substrate specificity were confirmed by site-directed mutagenesis.     

A new lineage of lichenized basidiomycetes inferred from a two-gene phylogeny: The Lepidostromataceae with three species from the tropics

The lichen habit has apparently evolved independently in at least five major clades of mushroom-forming basidiomycetes (Agaricomycetes). Tracing the origin of lichenization in these groups depends on a clearer understanding of the phylogenetic relationships of basidiolichens to other fungi. We describe here a new family of basidiolichens made up of tropical, soil-inhabiting fungi that form lichenized, scale-like squamules and erect, coral-like fruiting structures. These structures are common to two basidiolichen genera, Multiclavula and Lepidostroma. Molecular studies have confirmed the phylogenetic position of Multiclavula species in the Cantharellales, but Lepidostroma species have never been sequenced. We obtained nuclear small and large subunit ribosomal sequences from specimens of L. calocerum collected in Costa Rica and Mexico and also from specimens of two Multiclavula spp. recently described from Rwanda. The phylogenetic placement of these fungi within the Agaricomycetes was investigated using likelihood and Bayesian analyses. Our results indicate that L. calocerum and the Rwandan species form a natural group unrelated to Multiclavula and sister to the Atheliales, members of which are neither lichen-forming nor clavarioid. The independent evolution of morphologically similar forms in so many groups of basidiomycetes is a remarkable example of convergence, indicating similar pathways to lichenization in these fungi.     

The appropriate response of Spanish Gitanos: short-run orientation beyond current socio-economic status

Humans differ greatly in their tendency to discount future events, but the reasons underlying such inter-individual differences remain poorly understood. Based on the evolutionary framework of Life History Theory, influential models predict that the extent to which individuals discount the future should be influenced by socio-ecological factors such as mortality risk, environmental predictability and resource scarcity. However, little empirical work has been conducted to compare the discounting behavior of human groups facing different socio-ecological conditions. In a lab-in-the-field economic experiment, we compared the delay discounting of a sample of Romani people from Southern Spain (Gitanos) with that of their non-Romani neighbors (i.e., the majority Spanish population). The Romani-Gitano population constitutes the main ethnic minority in all of Europe today and is characterized by lower socio-economic status (SES), lower life expectancy and poorer health than the majority, along with a historical experience of discrimination and persecution. According to those Life History Theory models, Gitanos will tend to adopt “faster” life history strategies (e.g., earlier marriage and reproduction) as an adaptation to such ecological conditions and, therefore, should discount the future more heavily than the majority. Our results support this prediction, even after controlling for the individuals' current SES (income and education). Moreover, group-level differences explain a large share of the individual-level differences. Our data suggest that human inter-group discrimination might shape group members' time preferences through its impact on the environmental harshness and unpredictability conditions they face.     

A review of global diversity in avian haemosporidians (Plasmodium and Haemoproteus: Haemosporida): new insights from molecular data

Biogeographic patterns of parasite diversity are useful for determining how host–parasite interactions can influence speciation. However, variation in methodologies and sampling effort can skew diversity estimates. Avian haemosporidians are vector-transmitted blood parasites represented by over 1300 unique genetic lineages spread across over 40 countries. We used a global database of lineage distributions for two avian haemosporidian genera, Plasmodium and Haemoproteus, to test for congruence of diversity among haemosporidians and their avian hosts across 13 geographic regions. We demonstrated that avian haemosporidians exhibit similar diversity patterns to their avian hosts; however, specific patterns differ between genera. Haemoproteus spp. diversity estimates were significantly higher than those of Plasmodium spp. in all areas where the genera co-occurred, apart from the Plasmodium spp.-rich region of South America. The geographic distributions of parasite genera also differed, with Haemoproteus spp. absent from the majority of oceanic regions while Plasmodium spp. were cosmopolitan. These findings suggest fundamental differences in the way avian haemosporidians diverge and colonise new communities. Nevertheless, a review of the literature suggests that accurate estimates of avian haemosporidian diversity patterns are limited by (i) a concentration of sampling towards passerines from Europe and North America, (ii) a frequent failure to include microscopic techniques together with molecular screening and (iii) a paucity of studies investigating distributions across vector hosts.     

New insights into skeletal morphology of the oldest known silicoflagellates: Variramus, Cornua and Gleserocha gen. nov.

Two of the oldest known silicoflagellate-bearing sediments, lower Albian at Ocean Drilling Program Site 693 in the Weddell Sea of Antarctica and Santonian in the Devon Island sequence of the Canadian Archipelago, are re-examined with a focus on silicoflagellate genera Variramus, Cornua, and Gleserocha that lack basal rings, a feature appearing during late Santonian/early Campanian time within the genus Corbisema. The extraordinary variability of Variramus aculeifera is studied, and a new genus Gleserocha is proposed for taxa with apical structures made of three struts, but without pikes. This new genus includes previously described Variramus wisei and Cornua tapiae and new species G. harrisonii, and is here proposed as a genus transitional between Variramus and Cornua. Two unusual new species of Cornua, C. deflandrei and C. witkowskiana, are also described and a revised terminology is proposed for the skeletal components of Cornua and closely related genera.     

Survival and development of maize stem borer Chilo Partellus (Swinhoe) Lepidoptera: Crambidae on artificial diet

The Life cycle of maize stem borer, Chilo partellus (Swinhoe) was studied in in vitro conditions. Development of stem borer undergoes following stages like egg, larvae, pupa and moth. The egg incubation period ranged from 3 to 6 days, larval stage was observed in five instars. The mean value of I, II, III, IV and V instars showed 3.8 ± 0.16, 5.2 ± 0.02, 6.1 ± 0.06, 7.35 ± 1.5, and 10.12 ± 0.29 days, respectively and complete larvae period ranged from 42 to 49 days. Pupae stage was observed in 8–9 days. The pre-mating and mating period was found at 9.10 ± 1.20 and 5.14 ± 1.08 h while egg laying period in 4.1 ± 1.32 days respectively. Fecundity rate of stem borer is from 262 to 657 eggs. The life span of adult male (3-7) and female (3-8) days was observed with a mean of 6.30 ± 0.85 and 5.10 ± 0.69 days respectively. Life cycle of stem borer gets completed in 47 to 51 days. Development of quality insects in required quantities at different developmental stages and their timely supply plays an inevitable role particularly for insect-breeding resistant programs. Hence to meet these challenges we had tried to standardize an artificial diet with cost effective to rear Chilo partellus under in vitro conditions.     

Using stable isotope analysis to study the diet of Gilchristella aestuaria larvae: preliminary insights into the foodwebs of six South African estuaries

South African estuarine systems are becoming increasingly altered by anthropogenic and environmental factors, but the consequences of such changes for these systems are still not fully understood. The most common approach for evaluating the ecological status of aquatic systems is studying their associated foodwebs. Due to their high abundance and important ecological role, the larvae of estuarine round herring Gilchristella aestuaria (Gilchrist, 1913) are key candidates for examining the foodweb structure and function of southern African estuaries. The foodwebs and trophic interactions of G. aestuaria larvae in six estuaries in South Africa were compared using larvae sampled in November 2013 and analysed using δ¹³C and δ¹⁵N and Bayesian isotopic mixing models. The main prey type for G. aestuaria larvae in all estuaries was zooplankton. We found a high similarity among the Kariega, Gamtoos, Great Fish and Sundays estuaries in terms of consumers and potential sources for both δ¹³C and δ¹⁵N signatures. Significant differences were found in δ¹³C values among marine-dominated estuaries, such as the Kromme Estuary, and the more freshwater-dominated systems. In addition, in the Kromme Estuary particulate organic matter was very important in the diet of G. aestuaria larvae. Our results suggest that both food availability and physical environmental parameters strongly affect the diet and condition of G. aestuaria and, consequently, the entire foodweb in the system.