Preference for different prey allows the coexistence of several land planarians in areas of the Atlantic Forest

iNaturalist as a tool in the study of tropical molluscs

Although terrestrial gastropods are remarkably diverse, our knowledge of them is still lacking, especially for species from the Global South. As such, new tools to help researchers collect data on these organisms are very welcome. With this in mind, we investigated Brazilian observations on iNaturalist to assess the feasibility of the data available on the platform as a basis for studies on the tropical terrestrial gastropod fauna. The observations on iNaturalist were filtered by country, Brazil, and higher taxa, namely Eupulmonata, Cyclophoroidea and Helicinoidea, yielding a sample of 4,983 observations. These observations were then reviewed in search of records of rare or little-known species, species found outside their previously known range, and interesting ecological interactions. Exotic species made up 35% to 39% of the sampled iNaturalist records. The most commonly observed species were Lissachatina fulica (Bowdich, 1822), Bradybaena similaris (Férussac, 1822), Drymaeus papyraceus (Mawe, 1823), Drymaeus interpunctus (E. von Martens, 1887), Limacus flavus (Linnaeus, 1758), Meghimatium pictum (Stoliczka, 1873), Cornu aspersum (O. F. Müller, 1774), Vaginulus taunaisii (Férussac, 1821), Ovachlamys fulgens (Gude, 1900), and Bulimulus tenuissimus (Férussac, 1832). In total, 166 observations were deemed of interest to our purposes (e.g., rare species, range extensions, ecological interactions), totalling 46 identified species and 16 observations identified at genus level. Among the selected observations, we found pictures of live specimens of species that were previously known only from their shells, such as Megalobulimus pergranulatus (Pilsbry, 1901), bringing to light their appearances in life. Two potentially new species belonging to the genera Plekocheilus Guilding, 1827 and Megalobulimus K. Miller, 1878 were revealed. Additionally, we found records of living individuals of two species that were previously presumed to be possibly extinct, Leiostracus carnavalescus Simone & Salvador, 2016, and Gonyostomus egregius (Pfeiffer, 1845). We take the opportunity to discuss individual records of interest, evaluate the quality of the data and possible improvements, as well the potential and implications of the use of the iNaturalist platform for research in Brazil and other tropical countries. While iNaturalist has its limitations, it holds great potential to help document biodiversity in the tropics.

The sources of variation for individual prey-to-predator size ratios

The relative body size at which predators are willing to attack prey, a key trait for predator-prey interactions, is usually considered invariant. However, this ratio can vary widely among individuals or populations. Identifying the range and origin of such variation is key to understanding the strength and constraints on selection in both predators and prey. Still, these sources of variation remain largely unknown. We filled this gap by measuring the genetic, maternal and environmental variation of the maximum prey-to-predator size ratio (PPSR_max) in juveniles of the wolf spider Lycosa fasciiventris using a paternal half-sib split-brood design, in which each male was paired with two females and the offspring reared in two food environments: poor and rich. Each juvenile spider was then sequentially offered crickets of decreasing size and the maximum prey size killed was determined. We also measured body size and body condition of spiders upon emergence and just before the trial. We found low, but significant heritability (h² = 0.069) and dominance and common environmental variance (d² + 4c² = 0.056). PPSR_max was also partially explained by body condition (during trial) but there was no effect of the rearing food environment. Finally, a maternal correlation between body size early in life and PPSR_max indicated that offspring born larger were less predisposed to feed on larger prey later in life. Therefore, PPSR_max, a central trait in ecosystems, can vary widely and this variation is due to different sources, with important consequences for changes in this trait in the short and long terms.

Behavioral responses of three freshwater planaria species to light, visual and olfactory stimuli: Setting the stage for further ecotoxicological studies

Planarians are freshwater flatworms commonly used as environmental bioindicator due to their sensitivity of response and their ease of culturing in lab. Nevertheless, to date, very few studies describing their behavior have been led. This work aims to fill the literature gap by providing preliminary results through six behavioral challenges (locomotion, exploration, light stress, planarian light/dark test, shoaling and foraging) conducted with three different species Dugesia tigrina, Schmidtea mediterranea and Schmidtea polychroa. The behavioral responses of every species in each of these six assays were recorded and differences between species were highlighted, depending on the assays and conditions. Schmidtea polychroa is less active than the two others and had the highest light aversion. Reactions observed in response to diverse and realistic stimuli helped us to select the most suitable tests and choose the species that seem the most appropriate for future ecotoxicological and neurophysiological tests. Four tests - out of the six tested- seem reliable in order to standardize planarian behavioral tests.

Trying to take over the world: Potential distribution of Obama nungara (Platyhelminthes: Geoplanidae), the Neotropical land planarian that has reached Europe

Obama nungara Carbayo, Álvarez-Presas, Jones, & Riutort, 2016 is a land planarian (Platyhelminthes: Geoplanidae) native to southern South America, which has recently dispersed towards several countries of the European continent, thus becoming a threat to the native soil fauna. Its dispersion would be favoured by its wide food habit and its tendency to live linked to humans, being the plant trade its most plausible vector of dispersion. Here, we explored the potential distribution of O. nungara on a global scale by using the MaxEnt software. We used 144 records (encompassing 10 countries) from sampling campaigns, citizen science, recent literature, and material deposited in scientific collections. Our results showed that southern South America has favourable climatic conditions for O. nungara. MaxEnt also allowed predicting expansions to countries of Europe where this planarian is already established and to others not yet colonized, as well as to Asia (southern coast of the Caspian Sea, Taiwan, and south-east of mainland China) and Oceania (south-east of Australia and New Zealand). The potential distribution of O. nungara was mainly outlined by climatic factors related to temperature (annual mean temperature, mean temperature of the coldest quarter, and annual temperature range). Thus, under a global warming scenario, a significant expansion of O. nungara relative to the current prediction is expected. This information may be useful to design strategies to prevent new introductions, since the dissemination of this planarian seems to be strongly man-linked.

Obama chez moi! The invasion of metropolitan France by the land planarian Obama nungara (Platyhelminthes, Geoplanidae)

Background

Obama nungara is a species of land flatworm originating from South America; the species was recently described and distinguished from a similar species, Obama marmorata. Obama nungara has invaded several countries of Europe, but the extent of the invasion has not been thoroughly mapped.

Methods

In this article, based on a five and a half-year survey undertaken by citizen science, which yielded 530 records from 2013 to 2018, we analysed information about the invasion of Metropolitan France by O. nungara. We also investigated the variability of newly obtained cytochrome c oxidase 1 (COI) sequences of specimens from France, Italy and Switzerland.

Results

Obama nungara was recorded from 72 of the 96 Departments of Metropolitan France. The species is especially abundant along the Atlantic coast, from the Spanish border to Brittany, and along the Mediterranean coast, from the Spanish border to the Italian border. More than half of the records were from an altitude below 50 m, and no record was from above 500 m; mountainous regions such as the Alps, Pyrenees and Massif Central are not invaded. Local abundance can be impressive, with 100 of specimens found in a small garden. An analysis of our new COI sequences, combined with published sequences of specimens from several countries, confirmed that three clades comprise the species. The first clade, ‘Brazil’, is currently confined to this country in South America; the second clade, ‘Argentina 2’, was found in Argentina and in Europe, only in Spain; and the third, ‘Argentina 1’, was found in Argentina and in Europe, in Spain, Portugal, France, UK, Italy, Belgium, and Switzerland. This suggests that two clades of O. nungara from Argentina have invaded Europe, with one widely spread.

Discussion

The present findings strongly suggest that O. nungara is a highly invasive species and that the population which has invaded several countries in Europe comes from Argentina. The wide dispersion of the species and its reported local abundance, combined with the predatory character of the species, make O. nungara a potential threat to the biodiversity and ecology of the native soil fauna in Europe, and probably the most threatening species of all invasive land planarians present in Europe.

Mind the food: Survival, growth and fecundity of a Neotropical land planarian (Platyhelminthes, Geoplanidae) under different diets

Although most land planarians are sensitive to environmental changes, some species are well adapted to human-disturbed areas and are easily transported to new places, having the potential to threaten native ecosystems. We investigated growth and survival in a land planarian common in human-disturbed areas in southern Brazil. Specimens of Obama anthropophila were divided into three groups that received different diets: (1) only the land planarian Luteostriata abundans (N=13), (2) only the slug Deroceras leave (N=12), and (3) alternating both prey types (N=13). We monitored the weight of the specimens for a month and counted and weighed egg capsules. Planarians receiving a mixed diet tended to survive less than the groups receiving a single prey type; there were significant differences between those feeding on D. laeve and the other groups. Planarians with the mixed diet ate L. abundans more often than D. laeve, and those feeding only on L. abundans tended to eat more than the other groups. Most egg capsules were laid by specimens with a diet based on D. laeve but the mixed-diet group laid heavier capsules. Both prey species are suitable as food for O. anthropophila, although it prefers planarians when both food items are available. The constant alternation between food items seems to have adverse effects, perhaps related to physiological changes to digest different food items. The heavier egg capsules of the mixed-diet group, considering its lower survival, suggest terminal investment, i.e., an increased reproductive effort when approaching death. The ability to feed on both snails and planarians, combined with its proximity to humans, make O. anthropophila a potentially invasive species.

Far away, so close! Integrative taxonomy reveals a new genus and species of land flatworm (Platyhelminthes: Geoplanidae) from southern South America

Land flatworms usually show low ability to disperse and high endemicity, displaying many singletons in studies on land planarian assemblages. Thus, many species have been described based on specimens sampled in a single locality and/or on a few specimens. Based on phylogenetic analyses of concatenated COI and 18S rRNA genes and morphological analyses, a new genus and species of geoplaninid land planarian is described from central–east Argentina and southern Brazil. Winsoria gen. nov. shows, among its most outstanding features, a ventral cephalic retractor muscle and a subneural muscle layer that extends throughout the anterior region of the body. In addition, characters of the reproductive system and the phylogenetic analyses support the erection of this new genus. According to molecular phylogenies,Winsoria bipatria sp. nov. is closely related to species of Luteostriata, Supramontana and Issoca, taxa that also possess a cephalic retractor muscle. Despite its disjunct distribution, phylogenetic analyses, genetic divergence and morphological features show that the allopatric populations studied herein belong to a single species. We argue that the occurrence of W. bipatria in localities separated by hundreds of kilometres and a geographical barrier should be explained by passive dispersal.

Diet assessment of two land planarian species using high-throughput sequencing data

Geoplanidae (Platyhelminthes: Tricladida) feed on soil invertebrates. Observations of their predatory behavior in nature are scarce, and most of the information has been obtained from food preference experiments. Although these experiments are based on a wide variety of prey, this catalog is often far from being representative of the fauna present in the natural habitat of planarians. As some geoplanid species have recently become invasive, obtaining accurate knowledge about their feeding habits is crucial for the development of plans to control and prevent their expansion. Using high throughput sequencing data, we perform a metagenomic analysis to identify the in situ diet of two endemic and codistributed species of geoplanids from the Brazilian Atlantic Forest: Imbira marcusi and Cephaloflexa bergi. We have tested four different methods of taxonomic assignment and find that phylogenetic-based assignment methods outperform those based on similarity. The results show that the diet of I. marcusi is restricted to earthworms, whereas C. bergi preys on spiders, harvestmen, woodlice, grasshoppers, Hymenoptera, Lepidoptera and possibly other geoplanids. Furthermore, both species change their feeding habits among the different sample locations. In conclusion, the integration of metagenomics with phylogenetics should be considered when establishing studies on the feeding habits of invertebrates.

Coming out in a harsh environment: a new genus and species for a land flatworm (Platyhelminthes: Tricladida) occurring in a ferruginous cave from the Brazilian savanna

Faunal inventories in ferruginous caves from an area belonging to the Brazilian savanna (Cerrado phytophysiognomy), on the eastern margin of the Serra do Espinhaço Plateau, in southeastern Brazil, have revealed the occurrence of land flatworms. Herein, a flatworm sampled in such subterranean environment is described as a new genus and species of the Neotropical subfamily Geoplaninae, Difroehlichia elenae gen. nov., sp. nov. The new genus shows rare features within Geoplaninae, namely sub-cylindrical body, poorly developed sub-epidermal musculature and a narrow creeping sole. Some features, such as a small body and a broad sensory margin in the anterior region of the body, as well as the fact that the holotype showed signs of recent copula, may indicate an adaptation to the subterranean environment, probably representing a troglophile. Difroehlichia elenae is characterized by an almost homogeneous dark brown pigmentation over dorsal surface and body margins, a short cylindrical pharynx, and a tubular and unforked intrabulbar prostatic vesicle, among other features. The holotype shows a secondary male copulatory organ located immediately behind the primary one, both communicating with the female atrium and gonopore canal. Since the species seems to have low abundance and restricted distribution and its type-locality is affected by mining activities, major concern arises regarding its conservation.

First report of the invasive alien species Caenoplana coerulea Moseley, 1877 (Platyhelminthes, Tricladida, Geoplanidae) in the subterranean environment of the Canary Islands

The blue land planarianCaenoplanacoeruleaMoseley, 1877 is reported for the first time in the hypogean environment. Seven individuals ofC.coeruleawere collected in the most humid branch of an abandoned water mine in Gran Canaria (Canary Islands). Due to its character of generalist predator, it should be considered a threat for the endemic subterranean fauna.

Diversity out of simplicity: interaction behavior of land planarians with co-occurring invertebrates

Land planarians have a simple anatomy and simple behavioral repertoire in relation to most bilaterian animals, which makes them adequate for the study of biological processes. In this study, we investigate the behavior of land planarians during interaction events with other invertebrates found in the same environment. We observed 16 different behavioral units, including seven different capture behaviors and three different prey ingestion behaviors. The capture behavior varied from very simple, such as simply covering the prey with the body, to more complex ones, including two forms of tube formation that are described for the first time. In general, the capture behaviors were similar among different predators but different for different prey. Similarly, prey ingestion type was more related to prey type than to predator species, with small soft prey being swallowed without fragmentation, large prey being crushed, and prey with a hard skeleton being perforated. Considering that land planarians face limitations due to their lack of efficient ways to retain water, thus being highly dependent on a moist environment, the set of behaviors shown by them in this study was considerably rich, especially concerning strategies to capture prey.

Observations on food preference of Neotropical land planarians (Platyhelminthes), with emphasis on Obama anthropophila, and their phylogenetic diversification

The food preference of Obama anthropophila Amaral, Leal-Zanchet & Carbayo, 2015, a species that seems to be spreading across Brazil’s human-modified environments, was investigated. Extensive experiments led to the conclusion that the generalized diet of this species may have facilitated its dispersal. The analysis of 132 feeding records of 44 geoplaninid species revealed a tendency for closely related species to feed on individuals from similar taxonomic groups, suggesting that in this group behavioral evolution is more conserved than phylogenetic diversification.