Ronald Sluys’s research while affiliated with Naturalis Biodiversity Center and other places

Madagascar and the Comoros Archipelago are inhabited by freshwater planarians of the genus Dugesia characterized by a unique morphotype with long and pointed auricles, which were traditionally ascribed to only one species, Dugesia milloti. Collections of new specimens of these long-eared freshwater triclads enabled us to examine these worms in more detail than previously had been possible and, thus, we were able to study the animals from an integrative perspective, including morphological, karyological, and molecular data. In addition, we re-examined D. milloti specimens that were available from natural history collections. In contrast to previous notions, we found that at least seven species of long-eared planarians inhabit the Malagasy inland waters, two of which are here newly described, viz., Dugesia crassimentula Sluys & Stocchino, sp. nov., and Dugesia insolita Stocchino & Sluys, sp. nov. Molecularly, the long-eared planarians form a separate phylogenetic clade that is not closely related to the other distinct morphotypes of Malagasy congeners. Furthermore, our karyological analyses revealed a new haploid (n = 5) chromosome number for the genus Dugesia, being the lowest chromosome number presently known for this genus. In addition, a previously unknown autotomy-like behaviour in freshwater triclads is reported here for the first time.

A recent study on the freshwater planarian fauna of Corsica and Sardinia established that the formerly presumed single species Dugesia benazzii subsumed a complex of species. In that study, a thorough integrative taxonomic approach, combining molecular, morphological, and karyological data, uncovered the presence of two new endemic species. For the present study, additional samplings were conducted on Corsica, covering several new localities. The data obtained were added to our previous datasets, which included information on specimens collected from both islands. By taking a similar integrative approach to the prior study, we here describe another new endemic species from Corsica, Dugesia xeropotamica. Although our results support the separate status of this new species, it also turned out that the evolutionary relationships among species of the Corso-Sardinian clade remain unclear, because the relationships are not well resolved. Additionally, we corroborate the presence of Dugesia mariae on the Tyrrhenian islets of Montecristo and Molara, representing new records for this group of Dugesia species in the region of the Tyrrhenian Sea. In all, our findings indicate that the evolutionary and biogeographical history of Dugesia species in this region of the Western Mediterranean is more intricate than previously thought.

The order Fecampiida, a group of parasitic turbellarians, has been poorly studied in terms of its species diversity, morphology, and ecology. Fecampiida is positioned within the monophyletic clade Adiaphanida, along with Tricladida and Prolecithophora, but their phylogenetic relationships are not well understood. Although the nervous and muscular systems of only two species in Fecampiida have been studied, recent research inferred morphological similarities between Fecampiida and Prolecithophora. In this study, we collected fecampiid cocoons and juveniles at depths of 1861-4438 m in Japanese waters. We identified the species on the basis of swimming juvenile specimens and by using histological and molecular methods, while we also examined its musculature and nervous system. Our study revealed a more complex nervous system than previously reported, with dorsal, lateral, and ventral pairs of longitudinal nerve cords connected through an anterior neuropile and posterior transverse commissures. While the nervous and muscular morphology suggested similarities with Prolecithophora, our phylogenetic analysis did not support a close relationship between Fecampiida and Prolecithophora.

Two new species of the genus Dugesia from Southern China are described by applying an integrative approach, including morphological, karyological, histological, and molecular information. In the molecular phylogenetic tree, the two new species, Dugesia pendula Chen & Dong, sp. nov. and Dugesia musculosa Chen & Dong, sp. nov., fall into an Eastern Palearctic/Oriental clade and an Oriental/Australasian clade, respectively, while sharing only a rather distant relationship. The separate specific status of the two new species is supported also by their genetic distances. Dugesia pendula is characterized by the following features: symmetrical openings of the oviducts into the bursal canal, a duct between seminal vesicle and diaphragm, small diaphragm, dorsally located seminal vesicle, a penis papilla suspended from the dorsal wall of the male atrium, and mixoploid karyotype with diploid complements of 2 n = 2 x = 14 + 0 − 1 B-chromosome and triploid complements of 2 n = 3 x = 21 + 0 − 1 B-chromosome, with all chromosomes being metacentric. Dugesia musculosa is characterized by the following features: asymmetrical openings of the oviducts into the bursal canal; a ventrally displaced ejaculatory duct with a terminal opening; two diaphragms; a bursal canal provided with a strong, thick layer of circular muscle, which extends from the copulatory bursa to the common atrium and gonoduct; the left vas deferens opening at the midlateral wall of the seminal vesicle, while the right sperm duct opens at the dorsolateral wall of the seminal vesicle; and karyotype consisting of complicated diploid and aneuploid mosaicism, with diploid complements of 2 n = 2 x = 16 and 2 n = 2 x = 16 − 1 7th-18th, with all chromosomes being metacentric. The uncommon karyotypes, combined with the asexual reproduction of aneuploid animals, are evaluated in the context of the relationship between ploidy levels and reproductive modalities in the genus Dugesia.

A new species of freshwater flatworm of the genus Dugesia from Guangdong Province in China is described through an integrative approach, including molecular and morphological data, as well as mitochondrial genome analysis. The new species, Dugesia ancoraria Zhu & Wang, sp. nov. , is characterised by: (a) a highly asymmetrical penis papilla, provided with a hunchback-like dorsal bump; (b) a short duct between seminal vesicle and ejaculatory duct; and (c) a postero-ventral course of the ejaculatory duct, which opens to the exterior at the subterminal, ventral part of the penis papilla. The molecular phylogenetic tree obtained from the concatenated dataset of four DNA markers (18S rDNA, ITS-1, 28S rDNA, COI) facilitated determination of the phylogenetic position of the new species, which shares a sister-group relationship with a small clade, comprising D. notogaea Sluys & Kawakatsu, 1998 from Australia and D. bengalensis Kawakatsu, 1983 from India. The circular mitogenome of the new species is 17,705 bp in length, including 12 protein coding genes, two ribosomal genes, and 22 transfer RNAs. Via analysis of gene order of mitochondrial genomes, the presently available pattern of mitochondrial gene rearrangement in the suborder Continenticola is discussed.

A new species of the genus Dugesia (Platyhelminthes, Tricladida, Dugesiidae) from Xiangxi River, Shennongjia Forestry District, Hubei Province, China, is described on the basis of an integrative approach, involving morphology, and molecular systematics. The new species Dugesia saccaria A-T. Wang & Sluys, sp. nov. is characterized by the following features: a dumb-bell-shaped, muscularized hump located just anterior to the knee-shaped bend in the bursal canal; a ventrally displaced ejaculatory duct, which, however, opens terminally through the dorsal portion of the blunt tip of the penis papilla; a ventrally located seminal vesicle, giving rise to a vertically running duct that eventually curves downwards to communicate with the ejaculatory duct via a small diaphragm; oviducts opening asymmetrically into the dorsal portion of the common atrium and at the knee-shaped part of the bursal canal. The phylogenetic position of the new species was determined using four molecular markers (18S rDNA; ITS-1; 28S rDNA; COI), which suggested that it groups with other species of Dugesia from the Australasian and Oriental biogeographical regions.

Dugesia hepta and D. benazzii are two species found in Sardinia and Corsica. Previous studies have been unable to resolve their evolutionary relationships and there was doubt about the monophyly of D. benazzii. This study used molecular and morphological data to develop a rigorous species-delimitation procedure within an integrative framework. Three different species discovery methods (ABGD, GMYC, and mPTP) were applied on single-locus data to formulate primary species hypotheses. Secondary species hypotheses were proposed based on two Bayesian species-validation methods (BPP and BFD), morphological, and karyological traits. This study presents evidence supporting the recognition of two new species: Dugesia mariae from Corsica and Dugesia hoidi from Sardinia. A redescription of D. benazzii is also reported. The phylogenetic relationships between these four species were resolved with high support, except for D. hoidi. The performance of the different molecular-delimitation methodologies is discussed, as well as the presence of ciliate parasites in D. benazzii and D. mariae.

The hammerhead worms constitute a land planarian subfamily (Platyhelminthes: Tricladida: Bipaliinae) that is popular among natural historians as well as citizen scientists due to their characteristic semi-lunar-shaped head, the striking colours of many species, and the worldwide presence of introduced species, which has raised much concern about their putative impact on the receiving ecosystems. Despite such current awareness, the majority of Bipaliinae species was described before the second half of the 20th century. Over the past few decades, description of new species has been rather scarce. In the present paper, we describe twelve new species and two new genera from Madagascar, Borneo, and Japan, mainly using specimens that form part of the collections of Naturalis Biodiversity Center, Leiden. Species identification has been based on morphology, inner anatomy, and, when available, molecular information. Our molecular phylogenetic tree suggests that either Malagasy or Bornean representatives form the sister-group to the rest of Bipaliinae. The phylogeny suggests also that the Bipaliinae comprises several new and, as yet, undescribed genera. Although the geographical origin of the subfamily is uncertain and may involve either Madagascar or the Bornean region, a molecular time-calibration of the phylogenetic tree indicated that the origin of the Bipaliinae may date back to about 253 Mya, placing its origin near the Permian-Triassic transition and, thus, on Pangea.

In this contribution, feeding behaviour assays with the three species Paucumara falcata , Dugesia sp. and Girardia sp. were used to investigate the function of the pharynx during feeding and whether absence of feeding behaviour until full regeneration is a widespread phenomenon among planarians from different taxonomic groups. Our results showed that feeding behaviour of decapitated flatworms was inhibited. Intact worms responded only to pork liver pieces, but isolated pharynges were highly responsive to both pork liver pieces and pork liver extracts. After transverse cutting, the oral part of the isolated pharynx was responsive, while the aboral part showed no response to food items, suggesting that the oral portion of pharynx plays a crucial role during feeding.