Morphological Simplicity Research Articles

Resurgence of cloudinomorph fossils with possible cnidarian affinity at the peak of the Cambrian Explosion (Cambrian Series 2, Stage 3) in southern Shaanxi, China

AbstractDuring the Precambrian–Cambrian transition, tubicolous animals were prevalent among small shelly fossils. These include the oldest‐known skeletal fossil Cloudina from the terminal Ediacaran, and anabarites and hyoliths from the early Cambrian; considered to be possible annelids, cnidarians, and molluscs, respectively. Tubular fossils have important bio‐stratigraphic significance during this period, and their diversity and evolutionary radiation trend herald the Cambrian explosion. However, the relative morphological simplicity of these fossils and lack of preserved soft‐body information has resulted in poor taxonomic constraints. Here, numerous tubular fossils exhibiting multi‐stage cylindrical or conical cups were recovered from the middle–upper Guojiaba Formation of Cambrian Series 2, Stage 3, in Mianxian, South China. One new genus (Mianxiantubus) and three new species (M. cyathiformis, M. obconicus, and M. varius) were established to accommodate the morphological diversity of the fossils. However, their affinities remain contentious and undetermined and have been tentatively ascribed to Cnidaria. The possible morphology and growth patterns of Mianxiantubus suggest a close relationship with cloudinomorph fossils, although it is notably distinct from the quintessential cloudinids owing to the presence of transverse septa. Moreover, many other tubular fossils have been recovered from the same level, which may extend to the overlying Xiannvdong Formation (Stage 3), co‐occurring with archaeocyathids. This suggests that tubicolous organisms continued to diversify and occupied specific ecological niches even during the peak phase of the Cambrian explosion, dominated by bilateral epifaunal vagrants.

Embracing biodiversity: multispecies population genomics of leafless Bossiaea species shows novel taxa, population dynamics and conservation strategies

Leafless Bossiaea species are a unique group of plants endemic to Australia that present intriguing challenges in taxonomy and conservation because of their morphological simplicity and often small, disjunct populations. We employed whole genome reduced representation sequencing (DArTseq) to enhance our understanding of the population dynamics, diversity and taxonomy of leafless Bossiaea species. Our dataset comprised 52,539 single-nucleotide polymorphisms across 283 samples from 7 leafless Bossiaea species, including 6 listed threatened species. We examined population structure, phylogenetic relationships, kinship and gene flow within and among populations. On the basis of our population-genomic analyses, we propose recognition of the novel taxon Bossiaea vombata subsp. orientalis and a change in status from species (B. milesiae) to subspecies for B. fragrans subsp. milesiae. Additionally, we show extensive clonal reproduction across species and limited gene flow at distances of >1 km, shedding light on the challenges faced by these species. We advocate a coordinated approach to conservation, focusing on restoring self-sustaining populations and leveraging genetic rescue strategies. By addressing the population dynamics of multiple species simultaneously in taxonomically challenging lineages, we can make informed choices to safeguard biodiversity and evolutionary potential.

Multi-Technique Characterization of 3.45 Ga Microfossils on Earth: A Key Approach to Detect Possible Traces of Life in Returned Samples from Mars.

The NASA Mars 2020 Perseverance rover is actively exploring Jezero crater to conduct analyses on igneous and sedimentary rock targets from outcrops located on the crater floor (Máaz and Séítah formations) and from the delta deposits, respectively. The rock samples collected during this mission will be recovered during the Mars Sample Return mission, which plans to bring samples back to Earth in the 2030s to conduct in-depth studies using sophisticated laboratory instrumentation. Some of these samples may contain traces of ancient martian life that may be particularly difficult to detect and characterize because of their morphological simplicity and subtle biogeochemical expressions. Using the volcanic sediments of the 3.45 Ga Kitty's Gap Chert (Pilbara, Australia), containing putative early life forms (chemolithotrophs) and considered as astrobiological analogues for potential early Mars organisms, we document the steps required to demonstrate the syngenicity and biogenicity of such biosignatures using multiple complementary analytical techniques to provide information at different scales of observation. These include sedimentological, petrological, mineralogical, and geochemical analyses to demonstrate macro- to microscale habitability. New approaches, some unavailable at the time of the original description of these features, are used to verify the syngenicity and biogenicity of the purported fossil chemolithotrophs. The combination of elemental (proton-induced X-ray emission spectrometry) and molecular (deep-ultraviolet and Fourier transform infrared) analyses of rock slabs, thin sections, and focused ion beam sections reveals that the carbonaceous matter present in the samples is enriched in trace metals (e.g., V, Cr, Fe, Co) and is associated with aromatic and aliphatic molecules, which strongly support its biological origin. Transmission electron microscopy observations of the carbonaceous matter documented an amorphous nanostructure interpreted to correspond to the degraded remains of microorganisms and their by-products (extracellular polymeric substances, filaments…). Nevertheless, a small fraction of carbonaceous particles has signatures that are more metamorphosed. They probably represent either reworked detrital biological or abiotic fragments of mantle origin. This study serves as an example of the analytical protocol that would be needed to optimize the detection of fossil traces of life in martian rocks.

New genera and species with chloridium-like morphotype in the Chaetosphaeriales and Vermiculariopsiellales.

In this study, we investigated the morphological and genetic variability of selected species belonging to the genus Chloridium sensu lato, some also referred to as chloridium-like asexual morphs and other undescribed morphologically similar fungi. These species do not conform to the revised generic concept and thus necessitate a re-evaluation in terms of taxonomy and phylogeny. The family Chaetosphaeriaceae (Chaetosphaeriales) encompasses a wide range of asexual morphotypes, and among them, the simplest form is represented by Chloridium sect. Chloridium. The morphological simplicity of the Chloridium morphotype has historically led to the amalgamation of numerous unrelated species, thereby creating a heterogeneous genus. By conducting phylogenetic reconstruction of four DNA loci and examining a set of 71 strains, including all available ex-type and other non-type strains as well as holotypes and other herbarium material, we were able to gain new insights into the relationships between these taxa. Phylogenetic analyses revealed that the studied species are distantly related to Chloridium sensu stricto and can be grouped into two orders in the Sordariomycetes. Within the Chaetosphaeriales, they formed nine well-separated genera in four clades, such as Cacumisporium, Caliciastrum gen. nov., Caligospora gen. nov., Capillisphaeria gen. nov., Curvichaeta, Fusichloridium, Geniculoseta gen. nov., Papillospora gen. nov., and Spicatispora gen. nov. We also established Chloridiopsiella gen. nov. and Chloridiopsis gen. nov. in Vermiculariopsiellales. Four new species and eight new combinations are proposed in these genera. Our study provides a clearer understanding of the genus Chloridium, its relationship to other morphologically similar fungi, and a new taxonomic treatment and molecular phylogeny to facilitate their accurate identification and classification in future research. Taxonomic novelties: New genera: Caliciastrum Réblová, Caligospora Réblová, Capillisphaeria Réblová, Chloridiopsiella Réblová, Chloridiopsis Réblová, Geniculoseta Réblová, Papillospora Réblová, Spicatispora Réblová; New species: Caliciastrum bicolor Réblová, Caligospora pannosa Réblová, Chloridiopsis syzygii Réblová, Gongromerizella silvana Réblová; New combinations: Caligospora dilabens (Réblová & W. Gams) Réblová, Capillisphaeria crustacea (Sacc.) Réblová, Chloridiopsiella preussii (W. Gams & Hol.-Jech.) Réblová, Chloridiopsis constrictospora (Crous et al.) Réblová, Geniculoseta preussii (W. Gams & Hol.-Jech.) Réblová, Papillospora hebetiseta (Réblová & W. Gams) Réblová, Spicatispora carpatica (Hol.-Jech. & Révay) Réblová, Spicatispora fennica (P. Karst.) Réblová; Epitypifications (basionyms): Chaetosphaeria dilabens Réblová & W. Gams, Chloridium cylindrosporum W. Gams & Hol.-Jech. Citation: Réblová M, Nekvindová J (2023). New genera and species with chloridium-like morphotype in the Chaetosphaeriales and Vermiculariopsiellales. Studies in Mycology 106: 199-258. doi: 10.3114/sim.2023.106.04.

An enhancer trap system to track developmental dynamics in Marchantia polymorpha.

A combination of streamlined genetics, experimental tractability and relative morphological simplicity compared to vascular plants makes the liverwort Marchantia polymorpha an ideal model system for studying many aspects of plant biology. Here we describe a transformation vector combining a constitutive fluorescent membrane marker with a nuclear marker that is regulated by nearby enhancer elements and use this to produce a library of enhancer trap lines for Marchantia. Screening gemmae from these lines allowed the identification and characterization of novel marker lines, including markers for rhizoids and oil cells. The library allowed the identification of a margin tissue running around the thallus edge, highlighted during thallus development. The expression of this marker is correlated with auxin levels. We generated multiple markers for the meristematic apical notch region, which have different spatial expression patterns, reappear at different times during meristem regeneration following apical notch excision and have varying responses to auxin supplementation or inhibition. This reveals that there are proximodistal substructures within the apical notch that could not be observed otherwise. We employed our markers to study Marchantia sporeling development, observing meristem emergence as defining the protonema-to-prothallus stage transition, and subsequent production of margin tissue during the prothallus stage. Exogenous auxin treatment stalls meristem emergence at the protonema stage but does not inhibit cell division, resulting in callus-like sporelings with many rhizoids, whereas pharmacologically inhibiting auxin synthesis and transport does not prevent meristem emergence. This enhancer trap system presents a useful resource for the community and will contribute to future Marchantia research.

Morphological constraint obscures richness: a mitochondrial exploration of cryptic richness in Transversotrema (Trematoda: Transversotrematidae)

Species of Transversotrema Witenberg, 1944 (Transversotrematidae) occupy a unique ecological niche for the Trematoda, living externally under the scales of their teleost hosts. Previous studies of the genus have been impeded partly by limited variation in ribosomal DNA sequence data between closely related species and partly by a lack of morphometrically informative characters. Here, we assess richness of the tropical Indo-west Pacific species through parallel phylogenetic and morphometric analyses, generating cytochrome c oxidase subunit 1 mitochondrial sequence data and morphometric data for hologenophore specimens from Australia, French Polynesia, Japan and Palau. These analyses demonstrate that molecular data provide the only reliable basis for species identification; host distribution, and to a lesser extent morphology, are useful for identifying just a few species of Transversotrema. We infer that a combination of morphological simplicity and infection site constraint has led to the group displaying exceptionally low morphological diversification. Phylogenetic analyses of the mitochondrial data broadly support previous systematic interpretations based on ribosomal data, but also demonstrate the presence of several morphologically and ecologically cryptic species. Ten new species are described, eight from the Great Barrier Reef, Australia (Transversotrema chrysallis n. sp., Transversotrema daphnidis n. sp., Transversotrema enceladi n. sp., Transversotrema hyperionis n. sp., Transversotrema iapeti n. sp., Transversotrema rheae n. sp., Transversotrema tethyos n. sp., and Transversotrema titanis n. sp.) and two from off Japan (Transversotrema methones n. sp. and Transversotrema panos n. sp.). There are now 26 Transversotrema species known from Australian marine fishes, making it the richest trematode genus for the fauna.

Taxonomy of Cryptic Isoëtes Species from the Brazilian Semi-Arid Region, with a Note about the Putative Maternal Origin of Polyploids

Revealing the unrecognized diversity within cryptic species has profound implications in the taxonomy, systematics, evolutionary studies, and species protections throughout plant groups. Isoëtes is prone to a high rate of cryptic speciation because of its morphological simplicity, stasis, and convergence. Phylogenetic studies revealed cryptic species in the genus from the Brazilian semi-arid region (the Caatinga), which comprises the least studied and most endangered flora in Brazil. Here we conducted morphological analyses and chromosome counts, and took advantage of phylogenetic analyses already published for the genus to provide a taxonomic revision of Isoëtes from the Caatinga. Isoëtes anamariae and I. harleyi are two new species, which were revealed by molecular data and subtle morphological characters. This study provides descriptions, chromosome counts, illustrations of the most important morpho-taxonomic characters of species from the Caatinga, and a key to identify them. All species from this region are diploid and we show the importance of diploids in detangling the origin of polyploids in Brazil.

The Phylogenetic Placements of Psilophyton and the Psilotaceae

The monophyletic status of the taxa assigned to the iconic fossil genus Psilophyton remains problematic because of the possible extensive convergent evolution among organographically simple and ancient Paleozoic plants as well as their fragmentary nature. A similar issue arises when considering the morphological simplicity of lineages manifesting what appear to be highly reduced features, such as the Psilotaceae (Psilotum and Tmesipteris). A revised character matrix consisting of 53 characters and 146 character states for 41 fossil taxa (including four putative species of Psilophyton) and for the extant genera Equisetum, Psilotum, and Tmesipteris was used to assess the phylogenetic placement of the Psilotaceae and the fragmentary remains of Psilophyton. Analyses placed all four taxa assigned to Psilophyton within a well-defined trimerophyte-euphyllophyte clade but failed to find these taxa sharing a single common node. Analyses also could not displace the Psilotaceae from a poorly resolved zosterophyllophyte-lycophyte clade, regardless of how Psilotum and Tmesipteris character states were scored. The assignment of all four putative species of Psilophyton to a single genus was not supported. Analyses also indicate that the Psilotaceae would likely be classified as a fossil lycophyte lineage if known exclusively from their fossil remains.

Restricted Proliferation During Neurogenesis Contributes to Regionalisation of the Amphioxus Nervous System.

The central nervous system of the cephalochordate amphioxus consists of a dorsal neural tube with an anterior brain. Two decades of gene expression analyses in developing amphioxus embryos have shown that, despite apparent morphological simplicity, the amphioxus neural tube is highly regionalised at the molecular level. However, little is known about the morphogenetic mechanisms regulating the spatiotemporal emergence of cell types at distinct sites of the neural axis and how their arrangements contribute to the overall neural architecture. In vertebrates, proliferation is key to provide appropriate cell numbers of specific types to particular areas of the nervous system as development proceeds, but in amphioxus proliferation has never been studied at this level of detail, nor in the specific context of neurogenesis. Here, we describe the dynamics of cell division during the formation of the central nervous system in amphioxus embryos, and identify specific regions of the nervous system that depend on proliferation of neuronal precursors at precise time-points for their maturation. By labelling proliferating cells in vivo at specific time points in development, and inhibiting cell division during neurulation, we demonstrate that localised proliferation in the anterior cerebral vesicle is required to establish the full cell type repertoire of the frontal eye complex and the putative hypothalamic region of the amphioxus brain, while posterior proliferating progenitors, which were found here to derive from the dorsal lip of the blastopore, contribute to elongation of the caudal floor plate. Between these proliferative domains, we find that trunk nervous system differentiation is independent from cell division, in which proliferation decreases during neurulation and resumes at the early larval stage. Taken together, our results highlight the importance of proliferation as a tightly controlled mechanism for shaping and regionalising the amphioxus neural axis during development, by addition of new cells fated to particular types, or by influencing tissue geometry.

New species Micractinium kostikovii (Chlorellaceae, Trebouxiophyceae) from Russia

SUMMARYCorrectly identifying species of Chlorella‐like microalgae is difficult because of their morphological simplicity and high phenotypic plasticity. The use of molecular tools has revolutionized research on algal diversity, enabling such advances as the discovery of numerous new taxa. This article presents the results of a study of strains that are newly isolated from a freshwater Lake Prudovikov (Samara region, Russian Federation). These strains had the typical Chlorella morphology, exhibiting spherical cells and a cup‐shaped parietal chloroplast. The chloroplast contained a single pyrenoid enveloped by starch grains. However, 18S–ITS1–5.8S–ITS2 sequence analyses indicated that the studied strains are strongly allied with the well‐supported genus Micractinium. Based on the results of a comparative analysis of the morphological, molecular and environmental characteristics of the studied strains (employing a polyphasic approach), we propose that they are new species of Micractinium: Micractinium kostikovii sp. nov.

Tense/aspect marking in Arabic-based pidgins

The earliest stages of pidgin formation show a preference for analytic and morphologically reduced grammatical constructions relative to their lexifier or substrate languages, where the apparent morphological marking, if found, seems to be fossilized. Structural relations, therefore, are mostly expressed externally. Tense/aspect categories are marked through temporal adverbials or inferred from the context. Creole languages, however, are said to develop such categories through grammaticalization. This study examines tense/aspect marking in five Arabic-based pidgins: Juba Arabic, Turku Pidgin, Pidgin Madame, Romanian Pidgin Arabic, and Gulf Pidgin Arabic. Using Siegel's (2008) scale of morphological simplicity, from lexicality to grammaticality, this study concludes that tense/aspect marking is expressed lexically through temporal adverbials or inferred from the context in the earliest stages of Arabic-based pidgins, which only later—in stabilized pidgins—develops into grammaticalized markers when certain criteria are met. https://doi.org/10.2478/sm-2021-0002

Tense/Aspect Marking in Arabic-Based Pidgins

Summary The earliest stages of pidgin formation show a preference for analytic and morphologically reduced grammatical constructions relative to their lexifier or substrate languages, where the apparent morphological marking, if found, seems to be fossilized. Structural relations, therefore, are mostly expressed externally. Tense/aspect categories are marked through temporal adverbials or inferred from the context. Creole languages, however, are said to develop such categories through grammaticalization. This study examines tense/aspect marking in five Arabic-based pidgins: Juba Arabic, Turku Pidgin, Pidgin Madame, Romanian Pidgin Arabic, and Gulf Pidgin Arabic. Using Siegel’s (2008) scale of morphological simplicity, from lexicality to grammaticality, this study concludes that tense/aspect marking is expressed lexically through temporal adverbials or inferred from the context in the earliest stages of Arabic-based pidgins, which only later—in stabilized pidgins—develops into grammaticalized markers when certain criteria are met.

Major Tendencies of Lexical Borrowing from English to Oral Business Nepali: Implications for Translators and Language Teacher

In the present study, words and expressions from English used in Nepali while conducting business transactions orally were counted from a corpus comprising approximately 24,000 words using the "Navigation Pane" in the computer. A total of 875 English words including all repetitions were captured. Analyzing the contextual use-and-usage patterns of the English words from the data text, nine tendencies were identified: varying frequencies of the borrowed words; structural patterns of the loanwords; speaker-influence on hearer responses; brevity of the borrowed words/expressions; morphological simplicity; phonological deviation; borrowing as a need; borrowing as an option; and borrowing as a strategy of avoiding L1 vulgarism or indecency. The implication drawn from the study is important for translators and language teachers: there is no point in artificially translating commonly used loanwords borrowed from English to Nepali in the name of preserving the purity of the Nepali language. Moreover, an area for the English teacher's focus of teaching is the phonologically deviated loanblends.

Cnidarian Immunity and the Repertoire of Defense Mechanisms in Anthozoans.

Anthozoa is the most specious class of the phylum Cnidaria that is phylogenetically basal within the Metazoa. It is an interesting group for studying the evolution of mutualisms and immunity, for despite their morphological simplicity, Anthozoans are unexpectedly immunologically complex, with large genomes and gene families similar to those of the Bilateria. Evidence indicates that the Anthozoan innate immune system is not only involved in the disruption of harmful microorganisms, but is also crucial in structuring tissue-associated microbial communities that are essential components of the cnidarian holobiont and useful to the animal’s health for several functions including metabolism, immune defense, development, and behavior. Here, we report on the current state of the art of Anthozoan immunity. Like other invertebrates, Anthozoans possess immune mechanisms based on self/non-self-recognition. Although lacking adaptive immunity, they use a diverse repertoire of immune receptor signaling pathways (PRRs) to recognize a broad array of conserved microorganism-associated molecular patterns (MAMP). The intracellular signaling cascades lead to gene transcription up to endpoints of release of molecules that kill the pathogens, defend the self by maintaining homeostasis, and modulate the wound repair process. The cells play a fundamental role in immunity, as they display phagocytic activities and secrete mucus, which acts as a physicochemical barrier preventing or slowing down the proliferation of potential invaders. Finally, we describe the current state of knowledge of some immune effectors in Anthozoan species, including the potential role of toxins and the inflammatory response in the Mediterranean Anthozoan Anemonia viridis following injection of various foreign particles differing in type and dimensions, including pathogenetic bacteria.

Beyond the Two-Clause Sentence: Acquisition of Clause Chaining in Six Languages.

Clause chains are a special type of complex sentence, found in hundreds of languages outside Western Europe, in which clauses are dependent but not embedded, and dozens of clauses can be combined into a single sentential unit. Unlike English complex sentences, clause chains’ distribution is partially predictable in that they can, most fundamentally, be linked to a particular semantic context: description of temporally sequential events or actions. This and the morphological simplicity of verb forms in clause chains may combine to accelerate their acquisition by children, relative to complex sentences in other languages. No previous cross-linguistic studies of the acquisition of complex sentences have investigated clause chaining. In this paper, we report insights from a survey of the acquisition of clause chaining in six languages of diverse stocks with child speech databases spanning 1;1 to 10 years. Overall, children acquiring clause chaining languages begin to produce 2-clause chains between around 1;11 and 2;6. An initial stage in which chains are limited to just two clauses in length is followed by a stage in which longer chains of 3–5 clauses are also produced. Children acquiring languages in which adults produce both same-subject and different-subject clause chains produce a similar mix from early on; for some languages, this involves morphological “switch-reference” marking that anticipates the identity of the subject of an upcoming clause. This survey broadens our understanding of the acquisition of complex sentences by adding new data on the acquisition timing, semantics, and reference continuity of early clause chains.

Segregation of Maghemite Nanoparticles within Symmetric Diblock Copolymer and Triblock Terpolymer Patterns under Solvent Vapor Annealing.

Block copolymers (BCPs), through their self-assembly, provide an excellent guiding platform for precise controlled localization of maghemite nanoparticles (MNPs). Diblock copolymers (di/BCP) represent the most applied matrix to host filler components due to their morphological simplicity. A series of nanocomposites based on diblock copolymer or triblock terpolymer matrices and magnetic nanoparticles were prepared to study and compare the influence of an additional block into the BCP matrix. MNPs were grafted with low molecular weight polystyrene (PS) chains in order to be segregated in a specific phase of the matrix to induce selective localization. After the mixing of the BCPs with 10% w/v PS-g-MNPs, nanocomposite thin films were formed by spin coating. Solvent vapor annealing (SVA) enabled the PS-g-MNPs selective placement within the PS domains of the BCPs, as revealed by atomic force microscopy (AFM). The recorded images have proven that high amounts of functionalized MNPs can be controllably localized within the same block (PS), despite the architecture of the BCPs (AB vs. ABC). The adopted lamellar structure of the “neat” BCP thin films was maintained for MNPs loading approximately up to 10% w/v, while, for higher content, the BCP adopted lamellar morphology is partially disrupted, or even disappears for both AB and ABC architectures.

Tunicate gastrulation.

Tunicates are a diverse group of invertebrate marine chordates that includes the larvaceans, thaliaceans, and ascidians. Because of their unique evolutionary position as the sister group of the vertebrates, tunicates are invaluable as a comparative model and hold the promise of revealing both conserved and derived features of chordate gastrulation. Descriptive studies in a broad range of tunicates have revealed several important unifying traits that make them unique among the chordates, including invariant cell lineages through gastrula stages and an overall morphological simplicity. Gastrulation has only been studied in detail in ascidians such as Ciona and Phallusia, where it involves a simple cup-shaped gastrula driven primarily by endoderm invagination. This appears to differ significantly from vertebrate models, such as Xenopus, in which mesoderm convergent extension and epidermal epiboly are major contributors to involution. These differences may reflect the cellular simplicity of the ascidian embryo.

Multigene phylogeny reveals a new Iranian earthworm genus (Lumbricidae: Philomontanus) with three new species.

Lumbricidae taxonomy is vastly restricted by the morphological simplicity of earthworms and their lack of complex appendices. This has led to confusing results in the Lumbricidae classifications, which in turn, has hindered our ability to identify and assign new and cryptic species to the family. Here we propose the addition of a new Lumbricidae genus from the Zagros and Elburz Mountains of Iran, i.e. Philomontanus gen. nov, including three new species. Our taxonomic inferences were based on the phylogenetic analysis of two nuclear gene regions (28S rDNA and 18S rDNA) and 11 mitochondrial gene regions (16S rDNA, 12S rDNA, NADH dehydrogenase I, cytochrome oxidase subunits I and II and tRNAs Asn, Asp, Val, Leu, Ala and Ser). Philomontanus gen. nov comprises the earthworm species Philomontanus sarii sp. nov., Philomontanus mahmoudi sp. nov. and Philomontanus baloutchi sp. nov. These three species are morphologically similar to each other with only a few characters separating them (e.g. size, pigmentation and position of clitellum). Our findings support the adoption of an integrative approach including molecular information (e.g., DNA sequences) to aid earthworm classification and develop a robust taxonomy.

Analysis of immune response in the sea urchin larva.

Sea urchin larvae deploy a complex immune system in the context of relatively simple morphology. Several types of phagocytic or granular immune cells respond rapidly to microbes and microbial components within the body cavity. Many of these cells also respond to microbial disturbances in the gut lumen. In the course of immune response, hundreds of genes are up- and downregulated, many of which have homologs involved in immunity in other species. Thus, the larval sea urchin provides an experimentally advantageous model for investigating the response to immune challenge at the level of cell behavior and gene regulatory networks. Importantly, the morphological simplicity and optical clarity of these larvae allow studies to be carried out within the intact animal. Here, we outline techniques to probe and visualize the immune system of the feeding sea urchin larva, particularly for quantifying gene expression and cell migration as the animal responds to both pathogens and symbionts. Techniques addressed in this chapter include (1) exposure of larvae to microbes and microbial products in sea water and by blastocoelar microinjection, (2) time-lapse imaging of immune response, (3) isolation of culturable bacteria associated with feeding larvae, (4) quantification of larval associations with isolated bacterial strains and (5) preparation of secreted products from isolated bacteria for testing in larval culture.

A new approach to concept basicness and stability as a window to the robustness of concept list rankings

Abstract Based on a recently published large-scale lexicostatistical database, we rank 1,016 concepts by their suitability for inclusion in Swadesh-style lists of basic stable concepts. For this, we define separate measures of basicness and stability. Basicness in the sense of morphological simplicity is measured based on information content, a generalization of word length which corrects for distorting effects of phoneme inventory sizes, phonotactics and non-stem morphemes in dictionary forms. Stability against replacement by semantic shift or borrowing is measured by sampling independent language pairs, and correlating the distances between the forms for the concept with the overall language distances. In order to determine the relative importance of basicness and stability, we optimize our combination of the two partial measures towards similarity with existing lists. A comparison with and among existing rankings suggests that concept rankings are highly data-dependent and therefore less well-grounded than previously assumed. To explore this issue, we evaluate the robustness of our ranking against language pair resampling, allowing us to assess how much volatility can be expected, and showing that only about half of the concepts on a list based on our ranking can safely be assumed to belong on the list independently of the data.