Redescription and systematic position of Diandongia pista from the Chengjiang Lagerstätte

Diandongia pista Rong is the thickest-shelled and strongly mineralized of all the brachiopods that have been recorded from the Chengjiang Fauna. It is also one of the most common species in the biota. Previous accounts have concentrated largely on the exceptionally preserved soft-bodied anatomy of this species. Here its detailed internal and external shell morphologies are described for the first time, based on BSEM and SEM observations. Its general shell morphology, pseudointerareas, and pustulose ornamentation are most similar to those of the Botsfordiidae, where many species have a Diandongia-like rhombic pattern of pustules in the juvenile apical region only. On the other hand, other aspects of the muscle pattern and the partly smooth adult ornamentation of D. pista is more suggestive of species within the Neobolidae, like Edreja. The mantle canal system in sub-adults of D. pista is comparable to that of the Eoobolidae and Obolidae, whereas the adult vascular system branches peripherally in dichotomy. D. pista may be the earliest representatives possessing some plesiomorphic characters of the Botsfordiidae.     

Epibionts on the lingulate brachiopod Diandongia from the Early Cambrian Chengjiang Lagerst?tte,South China

The classic Chengjiang Lagerstätte (Lower Cambrian, Atdabanian stage: Yu''anshan Formation) Yunnan, southwestern China, has yielded, besides the exceptional and often controversial soft-bodied fossils, a fauna of primitive/early lingulid brachiopods. Diandongia pista (Rong 1974) is one of the commonest and most strongly mineralized of the phosphatic brachiopods from the Lagerstätte. The shells of this species have been found to commonly serve as a basibiont host. Epibionts comprise the coeval brachiopod Longtancunella chengjiangensis and the cone-shaped cnidarian-related Archotuba conoidalis, as well as rounded smaller-sized epizoans (lesser than 2 mm). A principle morphological analysis demonstrates that the ovoid and rounded organisms that often occur along the commissure of D. pista resemble small juvenile or immature brachiopods. Epibiont-bearing shells of D. pista with soft-tissue preservation demonstrate that the host brachiopods were overgrown while alive, and provide an argument for D. pista having a semi-infaunal life style with only the slim pedicle embedded in sediment. The epibiotic association sheds direct light on the ecology of Cambrian brachiopods in soft-substrate marine environments. The Chengjiang fossils demonstrate that the Early Cambrian brachiopods, as compared with recent lingulids, occupied different and a wider spectrum of ecological niches and tiers of space.     

The evolution of flightlessness: Is history important?

Summary Though most birds and insects are capable of flight (volant) some species are flightless. In this paper I test the hypothesis that phylogenetic constraints have played a role in the evolution of flightlessness. If speciation occurred after the evolutionary transition to flightlessness, inferences concerning the importance of particular aspects of the environment on the probability of the evolution of flightlessness may be statistically spurious because of the inflation of the sample size. Among birds, ratites and penguins illustrate the phenomenon of considerable speciation subsequent to the transition to the evolution of flightlessness. In contrast, the rails represent a group in which each flightless species probably represents a separate evolutionary transition. There are many more flightless insect species than bird species and several orders are monomorphically flightless, the sometimes enormous speciation within the order following and possibly being a consequence of the evolution of flightlessness. While it can be shown in insects that flightlessness has evolved independently many times, there are at least as many cases in which the question cannot be resolved. Therefore, in both birds and insects phylogenetic effects should not be ignored, for the number of evolutionary transitions may be much less than the number of species. The effect of incorporating phylogenetic (or at least taxonomic) constraints into the analysis of habitat factors associated with flightlessness is considered.     

Morphology of Cambrian lobopodian eyes from the Chengjiang Lagerstätte and their evolutionary significance

Visual organs are widely distributed throughout the animal kingdom and exhibit a great diversity of morphologies. Compound eyes consisting of numerous visual units (ommatidia) are the oldest preserved visual systems of arthropods, but their origins are obscure and hypothetical models for their evolution have been difficult to test in the absence of unequivocal fossil evidence. Here we reveal the detailed eye structures of well-preserved Early Cambrian lobopodians Luolishania longicruris and Hallucigenia fortis from the Chengjiang Lagerstätte, China. These animals possess a pair of eyes composed of at least two visual units, interpreted as pigment cups. Contrary to previous suggestions that Cambrian lobopodians possessed ocellus-like eyes comparable to those of extant onychophorans, this multi-component structure is more similar to the lateral eyes of arthropods. Morphological comparison and phylogenetic analyses indicate that these lobopodian eyes may represent an early stage in the evolution of the ancestral visual system of euarthropods.     

Are the speeds of species invasions regulated? The importance of null models

Understanding the mechanisms and patterns that govern the invasion of species is essential for coping with global change of the biological world. A recent study highlights the possibility, based on data from a wide range of different taxa, that the invasion speed of species could be governed by a regulatory process. In principle, it is possible that mechanisms such as Allee effects could cause the invasion fronts to be regulated, such that the change in the rate of spread is negatively related to the current rate. This is very similar to how some populations are regulated around an equilibrium size, and finding the regulation structure if true, is of both pure and applied interest. However, here we will argue that the methods used so far are incomplete, thus even though there is a theoretical possibility that the speed of species invasions are regulated, more scrutiny is needed for its detection. Analysing changes of the ratio of current and past rate of spread against current ratios may give the impression of regulation in null models that are in fact unregulated. In addition we show that the apparent pattern is highly influenced by the spatial scale of investigation. Our results show that detecting regulatory patterns in species invasions is similarly non-trivial as is detecting density-dependence per se, but necessary, given the importance of this problem.     

A new xandarellid arthropod from the Chengjiang Lagerstätte,Lower Cambrian of Southwest China

A new arthropod, Luohuilinella rarus nov. gen., nov. sp., is described from the Lower Cambrian Chengjiang Lagerstätte (Series 2, Stage 3), Yunnan, Southwest China. Luohuilinella nov. gen. is extremely rare in this Lagerstätte, represented by a single specimen. It has a large cephalic shield and a tapering trunk with well-developed pleural field. The cephalic shield is crescentic in outline and its anterolateral margin has two notches. The trunk is weakly trilobate, composed of 27 distinct tergites with well-developed pleural spines and a terminal piece. Luohuilinella nov. gen. resembles xandarellids in overall body architecture and especially in the reduced first trunk tergite. Its ventral morphology is, however, presently unknown. Therefore, it is provisionally assigned to Xandarellida.     

Reflections on the use of interviews in the history of science: who will write the history of science?

Interviews are an excellent source of information for historians of science. They should be done by historians who understand science in detail and, if possible, better than the scientists they interview. In the case of applied industrial or governmental sciences, historians must have detailed knowledge of economic or historic sources. Again they should know more in these areas than those they interview. If, on the contrary, the interviewers are not scientists at heart who know science, the history they write will become at best literature but at worst pseudoscientific abracadabra.     

The importance of willow thickets for ptarmigan and hares in shrub tundra: the more the better?

In patchy habitats, the relationship between animal abundance and cover of a preferred habitat may change with the availability of that habitat, resulting in a functional response in habitat use. Here, we investigate the relationship of two specialized herbivores, willow ptarmigan (Lagopus lagopus) and mountain hare (Lepus timidus), to willows (Salix spp.) in three regions of the shrub tundra zone-northern Norway, northern European Russia and western Siberia. Shrub tundra is a naturally patchy habitat where willow thickets represent a major structural element and are important for herbivores both as food and shelter. Habitat use was quantified using feces counts in a hierarchical spatial design and related to several measures of willow thicket configuration. We document a functional response in the use of willow thickets by ptarmigan, but not by hares. For hares, whose range extends into forested regions, occurrence increased overall with willow cover. The occurrence of willow ptarmigan showed a strong positive relationship to willow cover and a negative relationship to thicket fragmentation in the region with lowest willow cover at landscape scale, where willow growth may be limited by reindeer browsing. In regions with higher cover, in contrast, such relationships were not observed. Differences in predator communities among the regions may contribute to the observed pattern, enhancing the need for cover where willow thickets are scarce. Such region-specific relationships reflecting regional characteristics of the ecosystem highlight the importance of large-scale investigations to understand the relationships of habitat availability and use, which is a critical issue considering that habitat availability changes quickly with climate change and human impact.     

The importance of stable schooling: do familiar sticklebacks stick together?

Preferences for rejoining shoals composed of familiar individuals have recently been documented in a variety of small, shallow-water fish species. Such preferences are assumed to be adaptive, since familiar groups have improved anti-predator defences and more stable dominance hierarchies. However, the design of these studies may have created conditions that elevate preferences for familiar individuals. Furthermore, in natural habitats, where significant opportunities for inter-shoal transfer may exist, it is unclear whether shoals stay together long enough for such preferences to develop. Here we present the results of a laboratory study examining whether prior familiarity influences the subsequent shoal composition of sticklebacks (Gasterosteus aculeatus) allowed to re-assort freely in a large arena tank. We show that fish from different familiarity groups associate with familiar conspecifics significantly more than predicted by a model of random assortment, suggesting that even when there is ample opportunity for inter-group transfer, shoal composition can remain stable. We discuss the phenomena that may lead to the formation of familiar groups in natural habitats. In addition, we suggest that familiarity benefits may reduce the relative value of transferring to otherwise more attractive (e.g. larger or more phenotypically matched) groups, and thereby stabilize shoal structure.     

Is the hibiscus harlequin bug aposematic? The importance of testing multiple predators

Aposematism involves predators learning conspicuous signals of defended prey. However, prey species utilize a wide range of chemical (or physical) defenses, which are not likely to be equally aversive to all predators. Aposematism may therefore only be effective against a physiologically sensitive subset of potential predators, and this can only be identified through behavioral testing. We studied the emerging model organism Tectocoris diophthalmus (Heteroptera: Scutelleridae), an aposematically colored but weakly defended shieldback stinkbug, to test the efficacy of its defenses against a suite of predator types. We predicted the bugs' defenses would be ineffectual against both experienced and naïve birds but aversive to predaceous insects. Surprisingly, the opposite pattern was found. Both habituated wild passerines and naïve chickens avoided the bugs, the chickens after only one or two encounters. To avian predators, T. diophthalmus is aposematic. However, praying mantids showed no repellency, aversion, or toxicity associated with adult or juvenile bugs after multiple trials. Comparison with prior studies on mantids using bugs with chemically similar but more concentrated defenses underscores the importance of dose in addition to chemical identity in the efficacy of chemical defenses. Our results also emphasize the importance of behavioral testing with multiple ecologically relevant predators to understand selective pressures shaping aposematic signals and chemical defenses.     

The life history of the tropical shad Tenualosa toli from Sarawak: first evidence of protandry in the Clupeiformes?

Synopsis Sharp declines in catches prompted a detailed study of the commercially and culturally important terubok Tenualosa toli, which lives in the fast-flowing, turbid estuaries and adjacent shallow coastal waters of Sarawak. Its reproduction, diet, age and growth were investigated. An absence of small females and large males, together with histological data showing transitional gonads, suggest that T. toli is a protandrous hermaphrodite. Ageing based on otoliths indicates that individuals may not live more than about two years. Male fish spawn towards the end of their first year, change sex (transitional gonads were recorded in fish from 14 to 31 cm SL) and spawn as females in their second year. Spawning takes place in the middle reaches of estuaries and females deposit all their eggs at once. Fecundity is linearly related to fish length but shows significant seasonal and site variations. Hermaphroditism is discussed in relation to possible environmental and isolating mechanisms. T. toli is a zooplanktivore eating mainly calanoid copepods. Laser-ablation inductively-coupled plasma mass spectroscopy of trace elements across otoliths revealed that the species does not move into full seawater or freshwater, but completes its life cycle in estuarine and adjacent coastal waters. Therefore T. toli populations in each estuary and adjacent coastal waters may be relatively isolated from one another, and hence particularly susceptible to overfishing.     

What are the benefits of parental care? The importance of parental effects on developmental rate

The evolution of parental care is beneficial if it facilitates offspring performance traits that are ultimately tied to offspring fitness. While this may seem self‐evident, the benefits of parental care have received relatively little theoretical exploration. Here, we develop a theoretical model that elucidates how parental care can affect offspring performance and which aspects of offspring performance (e.g., survival, development) are likely to be influenced by care. We begin by summarizing four general types of parental care benefits. Care can be beneficial if parents (1) increase offspring survival during the stage in which parents and offspring are associated, (2) improve offspring quality in a way that leads to increased offspring survival and/or reproduction in the future when parents are no longer associated with offspring, and/or (3) directly increase offspring reproductive success when parents and offspring remain associated into adulthood. We additionally suggest that parental control over offspring developmental rate might represent a substantial, yet underappreciated, benefit of care. We hypothesize that parents adjust the amount of time offspring spend in life‐history stages in response to expected offspring mortality, which in turn might increase overall offspring survival, and ultimately, fitness of parents and offspring. Using a theoretical evolutionary framework, we show that parental control over offspring developmental rate can represent a significant, or even the sole, benefit of care. Considering this benefit influences our general understanding of the evolution of care, as parental control over offspring developmental rate can increase the range of life‐history conditions (e.g., egg and juvenile mortalities) under which care can evolve.     

Where and when the earliest coccolithophores?

Gardin, S., Krystyn, L., Richoz, S., Bartolini, A. & Galbrun, B. 2012: Where and when the earliest coccolithophores? Lethaia, Vol. 45, pp. 507–523. New calcareous nannofossil analyses from the Northern Calcareous Alps of Austria are herein used to update and improve the state of knowledge about the oldest occurrence of coccolithophores reported in the literature. Previously reported Norian occurrences of coccoliths were based on an obsolete Triassic chronostratigraphy, in which the Rhaetian stage was subsumed into the Norian (‘Sevatian 2’). The oldest stratigraphical record of coccoliths spp. lies just below the Norian‐Rhaetian boundary and the first coccolith species, Crucirhabdus minutus, is recorded from the base of Rhaetian stage. The latter bio‐event is located just above the First Occurrence of the conodont Misikella posthersteni and the first occurrence of the ammonoid Paracochloceras suessi in the Steinbergkogel section (Austria), Global Stratotype Section and Point (GSSP) candidate for the Norian–Rhaetian boundary. The appearance of the coccolith Crucirhabdus minutus is seen as a robust biochronological datum that will provide useful constraints for Triassic biostratigraphy, palaeoclimatic modelling and phylogenetic reconstructions. The new calcareous nannofossil biochronology of Steinbergkogel that we present herein completes the existing biostratigraphic characterization of the Norian‐Rhaetian transition based on conodonts and ammonoids and strengthens the position of Steinbergkogel as the best GSSP proposed section for the base of the Rhaetian. The record of coccolithophores across the Norian–Rhaetian boundary at Steinbergkogel takes place along with a discernible increase in abundance of Prinsiosphaera triassica, as well as the appearance of Euconusphaera zlambachensis, which are the two most important Rhaetian pelagic carbonate producers. This succession of bio‐events is interpreted as the initiation of the pelagic carbonate production driven by the successful spreading of calcareous nannofossils in the Western Tethys during the Rhaetian. □Austria, Calcareous Alps, coccolithophores, Triassic.