Search

Nonreproducibility in scientific investigations has been explained by inadequately reporting methodology, honest error, and even misconduct. We hypothesized that, within the field of animal physiology, the most parsimonious explanation for nonreproducibility is inadequate reporting of key methodological details. We further hypothesized that implementation of relatively recently released reporting guidelines has positively impacted journal article quality, as measured by completeness of the methodology descriptions. We analyzed 84 research articles published in five primarily organismal animal physiology journals in 2008–2010 (generally before current guidelines) and 2018–2020. Compliance for reporting 34 variables referring to biology, experiments, and data collection was assessed. Reporting compliance was just ∼61% in 2008–2010, rising only slightly to 67.5% for 2018–2020. Only 21% of the reported variables showed significant differences across the period from 2008–2020. We conclude that, despite attempts by societies and journals to promote greater reporting compliance, such efforts have so far been relatively unsuccessful in the field of animal physiology.

In this study, the hemolymph vascular system (HVS) in two cambarid crayfishes, i.e. the Marbled Crayfish, Procambarus virginalis Lyko, 2017 and the Spiny Cheek Crayfish, Faxonius limosus (Rafinesque, 1817), is investigated in regard of areas of non-genetic phenotypic variation. Despite their genetic identity, specimens of P. virginalis show variability in certain features of the HVS. Thus, we describe varying branching patterns, sporadic anastomoses, and different symmetry states in the vascular system of the marbled crayfish. We visualize our findings by application of classical and modern morphological methods, e.g. injection of casting resin, micro-computed tomography and scanning electron microscopy. By comparing our findings for P. virginalis to the vasculature in sexually reproducing crayfishes, i.e. F. limosus and Astacus astacus, we discuss phenotypic variation of the HVS in arthropods in general. We conclude that constant features of the HVS are hereditary, whereas varying states identified by study of the clonal P. virginalis must be caused by non-genetic factors and, that congruent variations in sexually reproducing F. limosus and A. astacus are likely also non-genetic phenotypic variations. Both common causal factors for non-genetic phenotypic variation, i.e., phenotypic plasticity and stochastic developmental variation are discussed along our findings regarding the vascular systems. Further aspects, such as the significance of non-genetic phenotypic variation for phylogenetic interpretations are discussed.

The morphology of hemolymph circulatory systems has been studied in many arthropod groups over the past decades. In most cases, however, the focus of these studies has been the vascular system, while its counterpart, the lacunar system, has often been neglected. To further understanding of the interrelationships between these two complementary subsystems, we investigated both, the hemolymph vascular system and the hemolymph lacunar system, of the decapod Penaeus vannamei using 3D-imaging techniques (micro-computed tomography and confocal laser scanning microscopy) in combination with 3D reconstruction. Major parts of the vascular and lacunar system are described. Our insights into their morphology are used to derive functional conclusions for a model illustrating the interrelationships between the two subsystems. The morphology of and the functional interaction between the vascular and lacunar systems are discussed in the context of the debate on "open vs. closed circulatory systems."

The need to protect neural tissue from toxins or other substances is as old as neural tissue itself. Early recognition of this need has led to more than a century of investigation of the blood-brain barrier (BBB). Many aspects of this important neuroprotective barrier have now been well established, including its cellular architecture and barrier and transport functions. Unsurprisingly, most research has had a human orientation, using mammalian and other animal models to develop translational research findings. However, cell layers forming a barrier between vascular spaces and neural tissues are found broadly throughout the invertebrates as well as in all vertebrates. Unfortunately, previous scenarios for the evolution of the BBB typically adopt a classic, now discredited ‘scala naturae’ approach, which inaccurately describes a putative evolutionary progression of the mammalian BBB from simple invertebrates to mammals. In fact, BBB-like structures have evolved independently numerous times, complicating simplistic views of the evolution of the BBB as a linear process. Here, we review BBBs in their various forms in both invertebrates and vertebrates, with an emphasis on the function, evolution, and conditional relevance of popular animal models such as the fruit fly and the zebrafish to mammalian BBB research.

Arthropods are the most species-rich taxon within Metazoa and have gone through major evolutionary changes with regard to body organization. Arthropod hearts and their associated vascular systems are thus morphologically highly disparate: while some arthropods exhibit very powerful hearts and complex vascular systems, other arthropods do not possess any kind of vascular system or heart at all. A comprehensive study investigating the structure of arthropods hearts has never been undertaken. In this study, we therefore investigate the hearts of 34 species from all major arthropod groups using various imaging techniques (confocal laser scanning microscopy, micro-computed tomography, histology) and describe them by addressing different aspects of heart morphology, e.g. the structure of the myocard or the composition of ostia. In a next step, we conceptualize 18 characters related to heart morphology and their respective character states and–using additional data from the literature–score a matrix for a total of 45 species from 38 supraspecific taxa. We map the characters onto prevailing phylogenetic hypotheses and perform parsimony-based ancestral state reconstruction to trace the evolutionary transformations undergone by arthropod hearts. An exploration of the character concepts (as explanatory hypotheses) reveals ontological peculiarities of character statements that clearly distinguish them in terms of ontological status from descriptive statements (i.e. descriptions of morphemes). The implications of these findings influence the interpretation of ground patterns as explanations. This first phylogenetic approach to heart morphology in the arthropod ground pattern reveals numerous new putative synapomorphies and leads to a reconsideration of the morphology of circulatory systems in early arthropods. Hypotheses on the evolution of hearts in (Pan-) Arthropoda are illustrated and discussed.

The field of morphology has recently seen the arrival of computer-aided ontologies, tools which permit the semantic organization of defined concepts and which therefore promise to be extremely useful in computer-mediated approaches involving morphological data, for example in cladistics. The theoretical relationship between ontologies and cladistics, however, has hardly been explored. Here we examine the ontological status of the main terms in morphological cladistics, i.e. morpheme, character, character state and ontological concept. Morphemes are units of the descriptional perspective, whereas character states are units of the evolutionary perspective and refer to identical stages of transformation. Both morphemes and character states represent things, i.e. real entities. However, character state and morpheme denote different perspectives on these entities (description vs. evolution). Characters (transformation series; Hennig's ideographic character concept) and ontological concepts are both classes, but not of the same nature. Ontological concepts which are used to classify morphemes are constructs, i.e. totally man-made classes that serve only as a way of classifying real entities for human recognition. Characters, however, are classes that encompass all character states of common descent and which therefore have objective, human-independent properties. Characters, then, are natural kinds, classes which exhibit a natural identity in the same way as monophyla do, for example, which also have common descent as an objective property. Against this background, ontology-based morphology can be a valuable addition to phylogenetic systematics. Formalized, machine-parsable descriptions permit the generalization of morphemes in large datasets and can facilitate the recognition of identical character states. However, the expertise of the researcher is indispensable, and full automation of the transfer from the descriptive level to the evolutionary level thus appears impossible.

Species of the megadiverse ground beetle tribe Platynini occur on all continents except Antarctica. It has been long recognized that platynine beetles were preserved in the Eocene Baltic amber. However, thus far only a single Eocene fossil has been described to the species level. In the present paper, a new species of Platynini known only as an amber inclusion fossil is described and imaged using light microscopy and micro X-ray computed tomography. Since this species cannot be assigned to any of the recently described genera, the monotypic genus Praeanchodemus gen. n., with the type species P. punctaticeps sp. n., is erected. There is some evidence from external morphology that Praeanchodemus gen. n. is part of a lineage comprising the recent genera Paranchodemus, Rhadine, and Tanystoma. However, since some synapomorphies were not found, the true relationships of the fossil taxon remain moot.

Horseshoe crabs (Xiphosura) have been an object of zoological research for almost 200 years. Although some morphological work on the circulatory system has been done, the three-dimensional structure of this complex organ system has never been shown satisfactorily and some crucial questions remain unanswered. Here, the circulatory systems of juveniles of the horseshoe crab taxa Limulus polyphemus and Carcinoscorpius rotundicauda were investigated using a combination of an injection method and micro-computed tomography. Data were processed and 3D-visualized using reconstruction software. Furthermore, the heart was examined using scanning electron microscopy. Additionally, the histology of some structures was investigated via light microscopy and transmission electron microscopy. The results show the high degree of complexity of the arterial and lacunar systems of Xiphosura and provide insights into their three-dimensional structure and relationship to other organ systems such as the central nervous system. We show that the major lacunae, previously described as vessel-like – though indeed highly ramified – can clearly be distinguished from arteries in histological sections because they have no distinct walls. Similarities and differences between the xiphosuran species and arachnids are highlighted and possible phylogenetic implications and evolutionary scenarios discussed.

Morphology, the oldest discipline in the biosciences, is currently experiencing a renaissance in the field of comparative phenomics. However, morphological/phenotypic research still suffers on various levels from a lack of standards. This shortcoming, first highlighted as the "linguistic problem of morphology", concerns the usage of terminology and also the need for formalization of morphological descriptions themselves, something of paramount importance not only to the field of morphology but also when it comes to the use of phenotypic data in systematics and evolutionary biology. We therefore argue, that for morphological descriptions, the basis of all systematic and evolutionary interpretations, ontologies need to be utilized which are based exclusively on structural qualities/properties and which in no case include statements about homology and/or function. Statements about homology and function constitute interpretations on a different or higher level. Based on these "anatomy ontologies", further ontological dimensions (e.g., referring to functional properties or homology) may be exerted for a broad use in evolutionary phenomics. To this end we present the first organ-based ontology for the most species-rich animal group, the Arthropoda. Our Ontology of Arthropod Circulatory Systems (OArCS) contains a comprehensive collection of 383 terms (i.e., labels) tied to 296 concepts (i.e., definitions) collected from the literature on phenotypic aspects of circulatory organ features in arthropods. All of the concepts used in OArCS are based exclusively on structural features, and in the context of the ontology are independent of homology and functional assumptions. We cannot rule out that in some cases, terms are used which in traditional usage and previous accounts might have implied homology and/or function (e.g. heart, sternal artery). Concepts are composed of descriptive elements that are used to classify observed instances into the organizational framework of the ontology. That is, descriptions in ontologies are only descriptions of individuals if they are necessary/and or sufficient representations of attributes (independently) observed and recorded for an individual. In addition, we here present for the first time an entirely new approach to formalizing phenotypic research, a semantic model for the description of a complex organ system in a highly disparate taxon, the arthropods. We demonstrate this with a formalized morphological description of the hemolymph vascular system in one specimen of the European garden spider Araneus diadematus. Our description targets five categories of descriptive statement: "position", "spatial relationships", "shape", "constituents", and "connections", as the corresponding formalizations constitute exemplary patterns useful not only when talking about the circulatory system, but also in descriptions in general. The downstream applications of computer-parsable morphological descriptions are widespread, with their core utility being the fact that they make it possible to compare collective description sets in computational time, that is, very quickly. Among other things, this facilitates the identification of phenotypic plasticity and variation when single individuals are compared, the identification of those traits which correlate between and within taxa, and the identification of links between morphological traits and genetic (using GO, Gene Ontology) or environmental (using ENVO, Environmental Ontology) factors. [Arthropoda; concept; function; hemolymph vascular system; homology; terminology.].