Invertebrate Biology最新文献

Changes in well-delimited Collembola communities along a steep microclimatic gradient at the entrance of Silická ľadnica Ice Cave, Slovakia, were investigated after 10 years (2007, 2017). We focused on the occurrence of psychrophilic and endemic species occupying this unique karst collapse doline and their response to climatic singularities in the given years as well as the increasing trend in regional air temperature. The soil temperature means at sites across the doline slope corresponded with climatic trends in the periods 2006–2007 and 2016–2017. Significantly lower average soil temperatures but significantly higher mean abundances, species richness, and diversity indices of the collembolan communities were recorded at sites during the second study period, which was characterized by more favorable soil microclimatic conditions (temperature and moisture content) compared to the first period. The dominance structure and community composition of the studied assemblages appeared to be relatively constant after 10 years, indicating stable collembolan communities, especially at cold sites at the bottom of the doline. Redundancy ordination analysis documented a clear delimitation of the communities in relation to the soil temperature, pH, and C:N ratio in both periods. Long-term (30-year) regional climatic data showed an increasing trend of annual air temperature means and precipitation. However, an increase in the number and abundance of xerothermophilous species and a decline in psychrophilic species (mostly endemic) along the gradient as a potential response of the increasing regional temperature were not observed, suggesting the high resilience of these communities. Microclimate and habitat heterogeneity are probably major drivers of soil Collembola communities along the steep microclimatic gradient of a karst collapse doline, which was observed by the repeated sampling after 10 years. Karst dolines as potentially important local sources of ɑ-diversity will likely become increasingly indispensable refugia for local biodiversity under ongoing global warming, thus deserving reliable conservation.

The renewal and shedding of hard ectodermal structures are widespread in invertebrates. The most impressive example of these processes in Trochozoa is the cuticle shedding observed in Hirudo medicinalis, originally studied over a century ago. Here we investigate cuticle shedding across three leech species: Hirudo sp., Haemopis cf. sanguisuga, and Erpobdella cf. octoculata. According to the ultrastructural data, all three species have a typical leech cuticle, consisting of basi- and epicuticles. Using in vivo observations and morphological investigations, we confirm cuticle shedding in Hirudo sp., and for the first time, report this process in Haemopis cf. sanguisuga. The successive stages of shedding of the old cuticle and formation of the new cuticle are ultrastructurally described for both species. Interestingly, individuals of Erpobdella cf. octoculata did not shed their cuticle during the entire observation period, neither as adults nor as juveniles. The semi-terrestrial lifestyle and the consumption of large food volumes may possibly be a prerequisite driving the development of regular cuticle shedding in Hirudo sp. and Haemopis cf. sanguisuga.

Writing assignments offer valuable student learning experiences in both live and online courses. But concerns about the challenges and extra work of marking, and about plagiarism, often deter instructors from using them. I used a writing assignment successfully over 20 years in a one-term invertebrate biology course, despite enrolments exceeding 100. Structured to maximally engage students yet minimize marking load, the assignment often yielded gems of stories for use in subsequent lectures. The Annotated Bibliography assignment asks students: (a) to précis the justification, main results, and significance of three papers from the primary scientific literature in under 250 words each, and (b) to provide a short (150 word) summary of the broader story connecting the three papers. Students liked this assignment because they could choose any aspect of the biology of any invertebrate genus. This inspired them to explore the literature out of personal interest. It's appealing for instructors, because annotations are compact and therefore easy to read, mark, and inspect for plagiarism. It is appealing to host universities, because it generates extensive use of library resources and motivates students to learn how to use them, and online taxonomic databases, effectively. Here I provide: (a) instructions for this assignment, (b) a straightforward marking rubric, (c) two examples of excellent submissions, and (d) comments on the risk and extent of plagiarism. Appendices provide: detailed instructions, a sample annotation with comments to guide student writing, an online submission web page, an online administrator web page, and PHP scripts for both web pages. Finally, I summarize topics and taxa from nearly 2,000 submissions. The five most popular taxa were cephalopods, insects, malacostracan crustaceans, gastropods, and arachnids. Although aspects of sex or reproduction, and camouflage or mimicry were the most popular topics, one paper on extreme limb movements in stomatopods was cited the most.

Although most millipedes (Diplopoda) show a biting–chewing feeding mode, representatives of the so-called Colobognatha (Platydesmida, Polyzoniida, Siphonocryptida, Siphonophorida), with their more or less reduced mouthparts, are assumed to have evolved a suctorial feeding mode, which enables them to exploit food sources like algal film and fungi hyphae. The Platydesmida are viewed as the key taxon for the understanding of mouthpart adaptations in Colobognatha, as their mouthpart elements still closely resemble those of biting–chewing millipedes. Studies of the skeletomuscular system of the Platydesmida are rare, impeding further understanding of the mouthpart evolution in millipedes. To overcome this impediment in the understanding of millipede evolution, we study the internal morphology of the head in specimens from four genera of Platydesmida: Brachycybe lecontii, Dolistenus spp., Gosodesmus claremontus, and Pseudodesmus spp. Although all Platydesmida show similarly structured skeletal elements and accompanying musculature, they are distinct from all other Diplopoda. Their head lacks eyes and organs of Tömösváry, and is pyriform and posteriorly bulging, overlapping the collum. The narrow mandibles are hidden underneath the broad genae. A previously described gnathochilarial postmentum is absent. Muscle attachment sites, such as the transverse mandibular tendon and the median septum, are reduced. The strong modifications of the head capsule, mandibles, and musculature limit the movability of the mandible for biting–chewing motions based on simulations of possible gape angles. Platydesmida likely show a scraping and slurping feeding mode, which is facilitated by the comparably well-developed pharyngeal dilator muscles. We suggest that the Platydesmida show an intermediate state between the biting–chewing millipedes and the other suctorially feeding Colobognatha.

The morphological diversity of marine annelid larvae is stunning. Although many of the larval forms have been categorized as trochophores or modified trochophores, there are a few groups with distinctive larval features that make them easy to distinguish from other annelid larvae. We collected 252 annelid larvae from the plankton, with particular emphasis on oweniids, polygordiids, and thalassematids (i.e., echiurans) and sequenced fragments of their cytochrome c oxidase subunit 1 and 16S ribosomal RNA genes. We found six oweniid, five polygordiid, and eight thalassematid OTUs. Thalassematids were found only in samples from the Pacific, and oweniids were found only in Caribbean samples. Among the oweniids we found two distinct morphotypes, one with a narrow, cloche shape and another that had a wider and more rectangular shape with clearly developed lappets. Among the polygordiids, we identified one larva as Polygordius eschaturus and several larvae as Polygordius jenniferae. All larvae, except for the P. eschaturus, which was at a stage too early to make a determination, were endolarvae. Among the thalassematids, we identified larvae of Ochetostoma edax and found seven unidentified OTUs. Finally, 150 miscellaneous polychaete larvae were sequenced, representing ~76 OTUs. Four rostraria larvae from the Caribbean, whose sequences confirm the long-held assumption that they are amphinomids, could not be identified to species. In total only 5% of these OTUs could be identified to species with known sequences, and most could not be identified to genus or even family with reasonable certainty. It is clear that this poor coverage in the reference databases will limit metabarcoding efforts to document numbers of OTUs, and that DNA barcodes will be of limited use for identifying neotropical marine annelids until reference databases have improved their coverage of this group.

Flatworms generally are simultaneous hermaphrodites that exhibit various kinds of mating behavior. Here we report on the mating behavior and reproductive biology of the planarian Paucumara falcata. We recognized three phases in its mating behavior: a courtship, copulation, and postcopulatory phase. During the last-mentioned phase, the partners showed a unique and very characteristic behavior in which their bodies intertwined, forming a spiral. Histological study of partners in copula revealed that the sclerotic tip of the musculo-parenchymatic organ pierces the body wall of the partner and then becomes lodged in its parenchyma, suggesting that this organ may act as an anchor, thus stabilizing the worms during copulation. Similar organs in other species of marine triclad may also perform a stabilizing role during copulation. During copulation in individuals of P. falcata, sperm transfer was reciprocal or only unilateral. Copulation duration ranged 13–35 min (average 20 ± 5 min), irrespective of whether the mating was successful (i.e., resulted in the production of fertile cocoons). The spiraling phase lasted on average 10 min; some worms did not show the postcopulatory spiraling phase during their mating behavior. After successful copulation, an individual worm produced 1–12 fertile cocoons over a period of 1–17 days; from a cocoon hatched either one young (in 70% of the cases), or two young worms.

Evolution of two novel feeding strategies among caenogastropod molluscs, suspension feeding in calyptraeids such as Crepidula fornicata and predatory feeding with a pleurembolic proboscis among neogastropods, may have both involved elongation of the anterior esophagus. Emergence of predatory feeding with a proboscis is particularly significant because it correlates with the rapid adaptive radiation of buccinoidean and muricoidean neogastropods during the Cretaceous. However, the notion that this important evolutionary transition involved elongation of the anterior esophagus to extend down a long proboscis has been disputed by evidence that it may have been the wall of the buccal cavity that elongated. We undertook a comparative study on foregut morphogenesis during larval and metamorphic development in C. fornicata and in three species of neogastropods with a pleurembolic proboscis to examine the hypothesis that the same region of foregut has elongated in all. We approached this by identifying a conserved marker for the boundary between buccal cavity and anterior esophagus, which was recognizable before the developing foregut showed regional differences in length. A survey of four species of littorinimorph caenogastropods suggested that the site of neurogenic placodes for the buccal ganglia could serve as this marker. Results showed that foregut lengthening in C. fornicata involved elongation posterior to neurogenic placodes for buccal ganglia, an area that corresponded to the anterior esophagus in the other littorinimorphs. However, foregut elongation occurred anterior to neurogenic placodes for buccal ganglia in two buccinoidean and one muricoidean neogastropod. The elongated foregut within the pleurembolic proboscis of these neogastropods qualifies as anterior esophagus only if the definition of the anterior esophagus is expanded to include the dorsal folds that run down the roof of the buccal cavity. Regardless of how the anterior esophagus is defined, comparative developmental data do not support the hypothesis of homology between the elongated adult foregut regions in C. fornicata and in neogastropods with a pleurembolic proboscis.

The hermaphroditic marine snail species Haminella solitaria was formerly included in the genus Haminoea, but it was recently assigned to the genus Haminella. The copulatory apparatus in H. solitaria was investigated by light and transmission electron microscopy to obtain additional information about this apparatus in cephalaspidean gastropods and to evaluate the taxonomic relevance of its morphofunctional features in the framework of a new phylogenetic tree of the family Haminoeidae. The copulatory apparatus in H. solitaria consisted of the atrium with a muscular wall and papilla, a seminal duct, and a single-lobed prostate. Epithelial and subepithelial secretory cells were detected in the proximal and middle region of the atrium wall, and a third type of secretory cell occurred in the distal region of the muscular papilla. The seminal duct was lined by ciliated cells and its muscular wall included some vacuolar cells. The prostate in H. solitaria consisted of lateral pouches surrounding a large central lumen that was filled with spermatozoa. A single type of secretory cell intermingled with ciliated cells formed the epithelium of the prostate. A histological comparison between the copulatory apparatus in H. solitaria and Haminoea navicula revealed substantial differences that support the placement of these two species in different genera, as established by recent molecular studies.

Species in the scorpion genus Centruroides (Scorpiones: Buthidae) are good candidates for the study of ecological niche partitioning because of their habitat plasticity, widespread geographic distribution, and presence of cryptic species. Currently, three species belonging to three subgroups of Centruroides are distributed along the Isthmus of Tehuantepec in southern Mexico, presenting a rare opportunity to study niche partitioning within a single genus. We examined the environmental, substrate, and habitat conditions of Centruroides flavopictus, Centruroides gracilis, and Centruroides rileyi within Estación de Biología Los Tuxtlas, west of the Isthmus of Tehuantepec. Our results demonstrate habitat partitioning occurs along humidity, temperature, and elevational gradients: individuals of C. gracilis were found in habitats of low humidity and high temperature, and were predominantly found on the substrate in human-mediated habitats; individuals of C. flavopictus were found in a larger range of humidity and temperature conditions within secondary and primary forest; and individuals of C. rileyi had the greatest habitat specificity, and were found in conditions of low temperature and high humidity on trees within primary forest. Furthermore, individuals of C. rileyi were found significantly higher in trees than those of C. flavopictus. This study represents the first example of niche partitioning within a genus of scorpion, and the first description of the ecological niche in an arboreal-specialist scorpion.

Some decapod species have intraspecific morphological variations that result in distinct adult morphotypes that influence the population structure, social dominance, and reproduction of the population. Here we investigated whether this differentiation into morphotypes occurs in adult males of Macrobrachium brasiliense, through the analysis of relative growth and morphology. Specimens were collected in the region of Uberlândia, Minas Gerais state, southeastern Brazil. Seven dimensions of each male were measured: carapace length (CL), ischium length, merus length, carpus length, propodus length, dactylus length, and major cheliped length. Principal component analysis, clustering, and discriminant analyses were used to identify possible morphotypes. The analysis of relative growth was employed to estimate the growth patterns of body structures (dependent variables) in relation to the CL (independent variable). Two morphotypes were identified: Mirim, which has less developed chelipeds (23.31 ± 3.08 mm) with fewer spines, and Açu, which has larger chelipeds (41.39 ± 8.14 mm) with many well-developed spines, especially in the merus. Most morphometric relationships differed significantly (p < .01) between the two morphotypes. The chelipeds were useful characters for the identification of the morphotypes of M. brasiliense, corroborating previous descriptions of the genus. We provide a detailed description of the main macroscopic characteristics that differed between morphotypes, which will enable their identification in future studies. Our results contribute to the knowledge of the population biology of M. brasiliense and should be considered in future investigations, since the presence of these male morphotypes probably influences the reproductive biology and population ecology of the species.