Zoological Letters最新文献

The osteohistology of Andrias spp. is a pivotal analogue for large fossil non-amniotes (e.g., Temnospondyli), and the endangered status of this taxon underlines the importance of gathering information on its growth. We here present the first osteohistological study by petrographic thin sections of an ontogenetic series of humeri and femora of eight individuals of varying sizes (28.5-104 cm) and ages (2.5-32 years) of Andrias japonicus from the Hiroshima City Asa Zoological Park, Japan. In addition, two individuals of A. cf. davidianus of unknown age but of different size (62 cm and 94 cm) were studied. All samples of Andrias spp. show a primary avascular periosteal cortex made of parallel-fibred tissue around the ossification center in the petrographic thin sections. Mainly in small individuals, the fibers forming this tissue are very coarse and loosely organized. With increasing size and age, the coarse tissue is irregularly intermixed and later replaced with finer and better organized fibers. This histologic change is accompanied by a change from diffuse annuli in the inner cortex to distinct lines of arrested growth (LAGs) in the outer cortex. We interpret these changes in tissue and the appearance of distinct growth marks as indicating the onset of active reproduction. The lack of primary vascularization around the ossification center in our Andrias spp. sample is striking and contradicts other observations. Vascularity may be prone to plasticity and further studies are necessary. We hypothesize that the large osteocyte lacunae and the dense networks of canaliculi observed in our sample may have nourished the tissue instead of primary vascular canals. We measured the size of osteocyte lacunae of Andrias spp. in comparison to other Lissamphibia, and found them to be significantly larger throughout ontogeny. The periosteal cortex contains a high amount of thick Sharpey's fibers all around the midshaft cross sections. The two samples of Andrias cf. davidianus show tissue and growth mark distribution similar to that observed in A. japonicus. However, the large individual of A. cf. davidianus differed in its extremely osteosclerotic condition and the retention of a small layer of calcified cartilage in the endosteal region of the femur. It remains unclear whether these differences are related to plasticity, taxonomy, sex, exogenous factors, or attributable to a regenerated but fully regrown leg. Although the present study is based on zoo-kept and not wild, animals, it yields important insights into osteohistological plasticity and growth patterns in giant salamanders.

Tadpoles serve as crucial evidence for testing systematic and taxonomic hypotheses. Suctorial tadpoles collected in Guyana were initially assigned to Rhaebo nasicus through molecular phylogeny. Subsequent analysis of larval and adult morphological traits revealed synapomorphies within the clade encompassing R. nasicus and R. ceratophrys, prompting the recognition of a new genus described herein as Adhaerobufo. The new genus is distinguished from other bufonids by specific phenotypic traits including an enlarged, suctorial oral disc with distinct papillae arrangements, and the presence of certain muscles and narial vacuities at the larval stage. However, only a few adult external characteristics (e.g., enlarged eyelids, infraocular cream spot), seem to be reliably discriminative from related genera. This study underscores the significance of larval morphology in anuran systematics and offers new insights into the evolution of suctorial and gastromyzophorous larvae within bufonids.

A review of the cuticular and sensory metatibial and metatarsal structures in cixiid planthoppers (Hemiptera: Fulgoromorpha) is proposed, depicting both their strong disparity and the great diversity of the patterns observed. Terminology and definitions for these structures are provided. The so-called lateral teeth of the metatibia in fact are particular styloconic sensory structures, called spiniform sensilla in Cixiidae. The apical metatibiotarsal teeth are non-sensory cuticular expansions, often bearing one or several chaetic sensilla ventrally, generally distributed in an internal and an external group of three teeth each, in some instances separated by a diastema; innermost and outermost teeth are generally larger. On the first tarsomere seven to eight teeth generally occur in one row, although two rows are observed in Brixidiini. A strong diversity of conformations and patterns is observed in the second metatarsomere. A specific subdorsal sensillum, of platellar type, may be present in the first metatarsomere teeth for a few taxa. It is generally present in the second metatarsomere, either as a narrow-based acutellar sensillum or as a broad-based platellar sensillum according to the taxon. Scanning electron microscope (SEM) analyses of 54 species of cixiids from all described tribes of the family, supplemented by data from the literature, are used to provide a metatibiotarsal diagnosis for each of the tribes of Cixiidae. In the state of our knowledge of the sufficiently precise observations of metatibiotarsal structures in the Cixiidae which are available, and of the phylogeny of the group as a frame of reference for their interpretations, we note that the observed patterns are probably the result of multiple and independent convergences and evolutionary regressions. These occurred at all levels of cixiid classification. Although these patterns can be useful in the identification of taxa at a low taxonomic level, they would be less useful for phylogenetic approaches.

Many plant-feeding stinkbugs belonging to the infraorder Pentatomomorpha possess a specialized symbiotic organ at the posterior end of the midgut, in which mutualistic bacterial symbionts are harbored extracellularly. In species of the superfamily Pentatomoidea, these symbionts typically are verticallytransmitted from host mothers to offspring, whereas in species of the superfamilies Coreoidea and Lygaeoidea they are acquired from the environment. In the pentatomoid family Cydnidae, vertical symbiont transmission has been reported in several species. Here, we report the first case of environmental symbiont acquisition in Cydnidae, observed in the burrower bug Macroscytus japonensis. A comprehensive survey of 72 insect samples from 23 sites across the Japanese archipelago revealed that (1) symbionts exhibit remarkably high diversity, forming six distinct phylogenetic groups within the Enterobacteriaceae of the γ-Proteobacteria, (2) most symbionts are cultivable and closely related to free-living Pantoea-allied bacteria, and (3) symbiont phylogenetic groups do not reflect the host phylogeny. Microbial inspection of eggs revealed the absence of bacteria on the egg surface. These results strongly suggest that symbionts are acquired from the environment, not vertical transmission. Rearing experiments confirmed environmental symbiont acquisition. When environmental symbiont sources were experimentally withheld, nymphs became aposymbiotic and died before molting to the second instar, indicating that nymphs environmentally acquire symbionts during the first-instar stage and that symbionts are essential for nymphal growth and survival. This study highlights Cydnidae as the only pentatomoid family that includes species that environmentally acquire symbionts and those that vertically transmit symbionts, providing an ideal platform for comparative studies of the ecological and environmental factors that influence the evolution of symbiont transmission modes.

In addition to the type locality (the summit of Aprada-tepui, Bolívar State of Venezuela), the distribution of the egg-brooding frog Stefania satelles was long thought to include several isolated tabletop mountain (tepui) summits surrounding the large Chimantá Massif in Bolívar State (hence the Latin name "satelles"). However, multilocus molecular phylogenetic analyses have revealed that this taxon includes several undescribed morphologically cryptic species, and that S. satelles should be restricted to its type locality. Two tepui-summit species confused under that name in the literature remain to be named, and the present paper aims at describing these populations previously referred to as Stefania sp. 3 and S. sp. 5. Stefania sp. 3 is only known from the small summit of Angasima-tepui, while S. sp. 5 is only reported from the small summit of Upuigma-tepui, both mountains being located south of the Chimantá Massif. These new, phylogenetically distinct species are described based on external morphology and osteology and in comparison to close relatives in the S. ginesi clade, which consists exclusively of tepui summit species. Both new species have highly restricted geographic ranges (less than 3 km²) and should be listed as Critically Endangered according to IUCN criteria.

Entomopathogenic nematodes of the genera Steinernema and Heterorhabditis, along with their bacterial symbionts from the genera Xenorhabdus and Photorhabdus, respectively, are important biological control agents against agricultural pests. Rapid progress in the development of genomic tools has catalyzed a transformation of the systematics of these organisms, reshaping our understanding of their phylogenetic and cophlylogenetic relationships. In this review, we discuss the major historical events in the taxonomy and systematics of this group of organisms, highlighting the latest advancements in these fields. Additionally, we synthesize information on nematode-bacteria associations and assess the existing evidence regarding their cophylogenetic relationships.

Venom production has evolved independently many times in the animal kingdom, although it is rare among mammals. Venomous shrews produce venom in their submandibular salivary glands and use it for food acquisition. Only a few toxins have been identified in shrew venoms thus far, and their modes of action require investigation. The biological and molecular processes relating to venom production and gland functioning also remain unknown. To address this gap, we investigated protein content in extracts from venom glands of two shrew species, Neomys fodiens and Sorex araneus, and interpreted their biological functions. Applying a proteomic approach coupled with Gene Ontology enrichment analysis, we identified 313 and 187 putative proteins in venom glands of N. fodiens and S. araneus, respectively. A search of the UniProt database revealed that most of the proteins found in both shrew species were involved in metabolic processes and stress response, while GO enrichment analysis revealed more stress-related proteins in the glands of S. araneus. Molecules that regulate molecule synthesis, cell cycles, and cell divisions are necessary to enable venom regeneration and ensure its effectiveness in predation and food hoarding. The presence of proteins involved in stress response may be the result of shrews' high metabolic rate and the costs of venom replenishment. Some proteins are likely to promote toxin spreading during envenomation and, due to their proteolytic action, reinforce venom toxicity. Finally, finding numerous proteins involved in immune response suggests a potential role of shrew venom gland secretions in protection against pathogens. These findings open up new perspectives for studying biological functions of molecules from shrew venom glands and extend our knowledge on the functioning of eulipotyphlan venom systems. Because the majority of existing and putative venomous mammals use oral venom systems to inject venom into target species, the methods presented here provide a promising avenue for confirming or discovering new taxa of venomous mammals.

Background: In gonochoristic animals, the sex determination pathway induces different morphological and behavioral features that can be observed between sexes, a condition known as sexual dimorphism. While many components of this sex differentiation cascade show high levels of diversity, factors such as the Doublesex-Mab-3-Related Transcription factor (DMRT) are widely conserved across animal taxa. Species of the phylum Tardigrada exhibit remarkable diversity in morphology and behavior between sexes, suggesting a pathway regulating this dimorphism. Despite the wealth of genomic and zoological knowledge accumulated in recent studies, the sexual differences in tardigrades genomes have not been identified. In the present study, we focused on the gonochoristic species Paramacrobiotus metropolitanus and employed omics analyses to unravel the molecular basis of sexual dimorphism.

Results: Transcriptome analysis between sex-identified specimens revealed numerous differentially expressed genes, of which approximately 2,000 male-biased genes were focused on 29 non-male-specific genomic loci. From these regions, we identified two Macrobiotidae family specific DMRT paralogs, which were significantly upregulated in males and lacked sex specific splicing variants. Furthermore, phylogenetic analysis indicated all tardigrade genomes lack the doublesex ortholog, suggesting doublesex emerged after the divergence of Tardigrada. In contrast to sex-specific expression, no evidence of genomic differences between the sexes was found. We also identified several anhydrobiosis genes that exhibit sex-biased expression, suggesting a possible mechanism for protection of sex-specific tissues against extreme stress.

Conclusions: This study provides a comprehensive analysis for analyzing the genetic differences between sexes in tardigrades. The existence of male-biased, but not male-specific, genomic loci and identification of the family specific male-biased DMRT subfamily provides the foundation for understanding the sex determination cascade. In addition, sex-biased expression of several tardigrade-specific genes which are involved their stress tolerance suggests a potential role in protecting sex-specific tissue and gametes.

As in most colonial and sessile marine invertebrates, bryozoan life history is characterized by asexual propagation of zooids for colonial growth and by sexual production of larvae for dispersal. However, comprehensive life histories, particularly in cryptic species such as endolithic (boring) bryozoans, remain poorly understood. The ctenostome family Penetrantiidae is widespread from temperate to tropical waters and often found in molluscan shells, offering an opportunity to study the boring lifestyle and its potential impact on bioerosion through growth and settlement experiments. Our research focused on Penetrantia clionoides from Guam in the Pacific Ocean, Penetrantia japonica from Japan, and a Penetrantia species from France in the Atlantic Ocean. We found distinct life histories and reproductive patterns potentially influenced by environmental factors such as temperature and food availability. The tropical P. clionoides displayed higher rates of larval production and growth compared to its temperate counterpart. For instance, the mean stolon extension was 335.2 μm/week in P. clionoides versus 232.1 μm/week in Penetrantia sp. Autozooid development took 13 days in P. clionoides and 31 days in Penetrantia sp. Anatomical features like apertural rims aided in species identification and in understanding larval settlement preferences, suggesting a tendency for philopatric settlement behavior. The bioerosional impact of penetrantiids remains little understood, but we generated first projections of bioerosion rates and a protocol for keeping Penetrantia under laboratory conditions, laying a foundation for further research in this field.