A taste for exotic food: Neotropical land planarians feeding on an invasive flatworm

An annotated checklist of terrestrial flatworms (Platyhelminthes: Tricladida: Geoplanidae) from Mexico, with new records of invasive species from a citizen science platform and a new nomen dubium

A checklist of species of terrestrial flatworms (Platyhelminthes: Tricladida: Geoplanidae) recorded for Mexico is compiled, listing 11 species. Five are directly referenced in the literature: Bipalium kewense Moseley, 1878, Bipalium vagum Jones & Sterrer, 2005, Diporodemus yucatani Hyman, 1938, Geoplana multipunctata Fuhrmann, 1914, and Pseudogeoplana nigrofusca (Darwin, 1844); and one species had been indirectly mentioned for the country: Parakontikia ventrolineata (Dendy, 1892), which was described from material intercepted in the USA in a shipment of ornamental plants from Mexico. Mexican records from the citizen science platform iNaturalist were reviewed, revealing the presence of five widely distributed invasive species: Caenoplana coerulea Moseley, 1877, recorded in Ciudad de Mexico; Endeavouria septemlineata (Hyman, 1939), recorded in Ciudad de Mexico, Estado de Mexico, Hidalgo, Jalisco, Morelos, and Oaxaca; Dolichoplana carvalhoi Corrêa, 1947, recorded in Jalisco; Dolichoplana striata Moseley, 1877, recorded in Morelos, Nuevo Leon, Quintana Roo, Tamaulipas, and Veracruz; and Rhynchodemus sylvaticus (Leidy, 1851), recorded in Jalisco. The presence of Parakontikia ventrolineata is confirmed for the country, being recorded in Ciudad de Mexico, Estado de Mexico, Hidalgo, Jalisco, Michoacan, Puebla, Queretaro, and Veracruz. The original description of Pseudogeoplana nigrofusca was revisited and compared to subsequent descriptions and keys, noting that the specimens are not conspecific and that the original description is too vague to accurately identify the species, therefore, this taxon is hereby relegated as a nomen dubium. A key for the higher taxa (subfamilies and tribes) of the North American terrestrial flatworms is proposed.

Negative impacts of invasive predators used as biological control agents against the pest snail Lissachatina fulica: the snail Euglandina ‘rosea’ and the flatworm Platydemus manokwari

Since 1955 snails of the Euglandina rosea species complex and Platydemus manokwari flatworms were widely introduced in attempted biological control of giant African snails (Lissachatina fulica) but have been implicated in the mass extinction of Pacific island snails. We review the histories of the 60 introductions and their impacts on L. fulica and native snails. Since 1993 there have been unofficial releases of Euglandina within island groups. Only three official P. manokwari releases took place, but new populations are being recorded at an increasing rate, probably because of accidental introduction. Claims that these predators controlled L. fulica cannot be substantiated; in some cases pest snail declines coincided with predator arrival but concomitant declines occurred elsewhere in the absence of the predator and the declines in some cases were only temporary. In the Hawaiian Islands, although there had been some earlier declines of native snails, the Euglandina impacts on native snails are clear with rapid decline of many endemic Hawaiian Achatinellinae following predator arrival. In the Society Islands, Partulidae tree snail populations remained stable until Euglandina introduction, when declines were extremely rapid with an exact correspondence between predator arrival and tree snail decline. Platydemus manokwari invasion coincides with native snail declines on some islands, notably the Ogasawara Islands of Japan, and its invasion of Florida has led to mass mortality of Liguus spp. tree snails. We conclude that Euglandina and P. manokwari are not effective biocontrol agents, but do have major negative effects on native snail faunas. These predatory snails and flatworms are generalist predators and as such are not suitable for biological control.

The ecology and evolution of autotomy

Autotomy, the self-induced loss of a body part, occurs throughout Animalia. A lizard dropping its tail to escape predation is an iconic example, however, autotomy occurs in a diversity of other organisms. Octopuses can release their arms, crabs can drop their claws, and bugs can amputate their legs. The diversity of organisms that can autotomize body parts has led to a wealth of research and several taxonomically focused reviews. These reviews have played a crucial role in advancing our understanding of autotomy within their respective groups. However, because of their taxonomic focus, these reviews are constrained in their ability to enhance our understanding of autotomy. Here, we aim to synthesize research on the ecology and evolution of autotomy throughout Animalia, building a unified framework on which future studies can expand. We found that the ability to drop an appendage has evolved multiple times throughout Animalia and that once autotomy has evolved, selection appears to act on the removable appendage to increase the efficacy and/or efficiency of autotomy. This could explain why some autotomizable body parts are so elaborate (e.g. brightly coloured). We also show that there are multiple benefits, and variable costs, associated with autotomy. Given this variation, we generate an economic theory of autotomy (modified from the economic theory of escape) which makes predictions about when an individual should resort to autotomy. Finally, we show that the loss of an autotomizable appendage can have numerous consequences on population and community dynamics. By taking this broad taxonomic approach, we identified patterns of autotomy that transcend specific lineages and highlight clear directions for future research.

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.