Somewhere I Belong: Phylogenetic Comparative Methods and Machine Learning to Investigate the Evolution of a Species-Rich Lineage of Parasites

Metazoan parasites encompass a significant portion of the global biodiversity. Their relevance for environmental and human health calls for a better understanding as parasite macroevolution remains mostly understudied. Yet limited molecular, phenotypic, and ecological data have so far discouraged complex analyses of evolutionary mechanisms and encouraged the use of data discretisation and body-size correction. In this case study, we aim to highlight the limitations of these methods and propose new methods optimised for small datasets. We apply multivariate phylogenetic comparative methods (PCMs) and statistical classification using support vector machines (SVMs) to a data-deficient host-parasite system. We use continuous morphometric and host range data currently widely inferred from a species-rich lineage of parasites (Cichlidogyrus incl. Scutogyrus - Platyhelminthes: Monogenea, Dactylogyridae) infecting cichlid fishes. For PCMs, we modelled the attachment organ and host range evolution using the data of 135 species and an updated multi-marker (28S and 18S rDNA, ITS1, COI mtDNA) phylogenetic reconstruction of 58/137 described species. Through a cluster analysis, SVM-based classification, and taxonomic literature survey, we infered the systematic informativeness of discretised and continuous characters. We demonstrate that an update to character coding and size-correction techniques is required as some techniques mask phylogenetic signals but remain useful for characterising species groups of Cichlidogyrus. Regarding the attachment organ evolution, PCMs suggest a pattern associated with genetic drift. Yet host and environmental parameters might put this structure under stabilising selection as indicated by a limited morphological variation. This contradiction, the absence of a phylogenetic signal and multicollinearity in most measurements, a moderate 73% accordance rate of taxonomic approach and SVMs, and a low phylogenetic informativeness of reproductive organ data suggest an overall limited systematic value of the measurements included in most species characterisations. We conclude that PCMs and SVM-based approaches are suitable tools to investigate the character evolution of data-deficient taxa.

RHIPIDOCOTYLE CAMPANULA (DIGENEA, BUCEPHALIDAE): MUSCULAR SYSTEM, LOCALIZATION OF SEROTONIN AND NEUROPEPTIDE FMRFamide IN NERVOUS SYSTEM

Trematodes of the Bucephalidae family differ from all other trematodes by the number of morphological characteristics including the structure of their attachment organ as well as the digestive and reproductive systems. In this study, the muscular system and nerve components containing serotonin and neuropeptide FMRFamid were investigated in Rhipidocotyle campanula (Bucephalidae family) from the intestine of the pike. Using immunocytochemical methods and confocal scanning laser microscopy (CSLM), data on the presence and distribution of neurotransmitters serotonin as well as the neuropeptide FMRFamide in the central and peripheral nervous system of Rh. campanula were obtained. When studying the relationship of nerve structures containing the studied neurotransmitters, muscle fibers of the muscle elements of the parasite were stained using the phalloidin associated with the fluorophore. Information on the organization of the muscular system, attachment organ, digestive and reproductive systems is given. The data obtained suggest that serotonergic and FMRF-amidergic nerve structures are involved in the regulation of the function of the attachment organ, as well as the digestive and terminal departments of the eproductive system of Rh. campanula. A comparative analysis of the obtained results and related data available in the literature for other trematodes was carried out.

Variasi Morfologi Holdfast Lernaea Yang Menyerang Ikan Gurami Di Jawa Timur [Morphological Variation Of Lernaea Holdfast Infest Gouramy In East Java]

Lernaeosis is one of the parasitic diseases in freshwater fish caused by Lernaea cyprinacea. These parasites infest many freshwater fish. Identification of parasites carried by observing the morphology of holdfast as an attachment organ. This study aims to make observations on the variation of morphology of Lernaea holdfast's in East Java and the identification of Lernaea infest gouramy in East Java.

A new genus and species of the Dasybatotreminae Bychowsky, 1957 (Monogenea: Monocotylidae), parasitic on Hypanus dipterurus (Jordan & Gilbert) (Myliobatiformes: Dasyatidae) in the Southeastern Pacific Ocean off Peru

Peruanocotyle n. gen. is proposed to accommodate Peruanocotyle chisholmae n. sp. (Monogenea: Monocotylidae). The new species is a gill parasite of the diamond stingray, Hypanus dipterurus (Jordan & Gilbert) (Myliobatiformes: Dasyatidae), a demersal chondrichthyan collected off the coast of Callao, Peru. Peruanocotyle n. gen. is placed in the Dasybatotreminae Bychowsky, 1957 because its anterior attachment organ has multiple glandular openings. Peruanocotyle chisholmae n. gen., n. sp. is unique among the Dasybatotreminae, by having: a well-developed, broadly ovoid anterior attachment organ with numerous grooves and an anteromedial notch; three prominent anterior glands that are connected to numerous peripheral glands; an unusual whip-shaped male copulatory organ composed of four connate tubes; an ejaculatory duct with slightly sclerotized walls where the proximal end has criss-crossed creases and the distal portion is highly convoluted; an ejaculatory bulb with one bipartite internal seminal vesicle; a wheel-shaped haptor with one central loculus and eight peripheral loculi; anchors that are much shorter than the width of marginal membrane and have an accessory sclerotized piece present; four oval testes, arranged in two groups; an ovary that has six clavate, proximal lobules and a distal portion that is strongly coiled; intestinal ceca with large lateral and medial diverticula; an oral opening surrounded by numerous small dome-like papillae; and a single vagina with sclerotized walls. Dasybatotreminae is amended to accommodate the new genus, and the new species is fully described and illustrated herein. The present finding adds to the other three marine monocotylids previously reported from Peru, namely Anoplocotyloides chorrillensis Luque & Iannacone, 1991; Anoplocotyloides papillatus (Doran, 1953) Young, 1967 and Monocotyle luquei Chero, Cruces, Iannacone, Sanchez, Minaya, Sáez & Alvariño, 2016.

A GEOMETRIC MORPHOMETRIC APPROACH TO THE ANALYSIS OF THE SHAPE VARIABILITY OF THE HAPTORAL ATTACHMENT STRUCTURES OF LIGOPHORUS SPECIES (PLATYHELMINTHES: MONOGENEA)

The taxonomy of Ligophorus Euzet & Suriano, 1977, like the most of monopisthocotylean monogeneans, relies heavily on the morphology of sclerites of the posterior attachment organ (haptor). Geometric morphometric approach is used to analyse variability and compare the shapes of haptoral structures of these monogeneans. We outline the shapes of the sclerities by cubic Bezier curves and store results in SVG files. Every SVG outline is reduced to a set of harmonics of Elliptic Fourier transform using ElFourier program. Harmonics are the sequence of unique numbers that describe the shape of structures and are invariant to their sizes, rotation, and orientation. They allow reconstructing source outline images, finding their average form, analyzing variability and comparing shapes in combination with other numerical data like dimensions. We use that approach to investigate intra- and interspecific variability of 400 haptoral structures of seven representatives of Ligophorus, parasitising four mullet species from the Black Sea, and to discriminate these monogeneans. This method is perspective for the creation of semiautomatic key for identification of helminthes, which are mainly distinguished by the shape and dimensions of the attachment organs. The obtained results and method prospects are discussed.

Ancyrocephalidae (Monogenea) of Lake Tanganyika: Does the Cichlidogyrus parasite fauna of Interochromis loocki (Teleostei, Cichlidae) reflect its host’s phylogenetic affinities?

The faunal diversity of Lake Tanganyika, with its fish species flocks and its importance as a cradle and reservoir of ancient fish lineages seeding other radiations, has generated a considerable scientific interest in the fields of evolution and biodiversity. The Tropheini, an endemic Tanganyikan cichlid tribe, fills a peculiar phylogenetic position, being closely related to the haplochromine radiations of Lakes Malawi and Victoria. Several problems remain regarding their genus-level classification. For example, the monotypic genus Interochromis is phylogenetically nested within Petrochromis; its only representative, I. loocki, has often been reclassified. As monogenean flatworms are useful markers for fish phylogeny and taxonomy, the monogenean fauna of Interochromis loocki was examined and compared to that of other tropheine cichlids. Three new monogenean species belonging to Cichlidogyrus are described from Interochromis loocki: Cichlidogyrus buescheri Pariselle and Vanhove, sp. nov., Cichlidogyrus schreyenbrichardorum Pariselle and Vanhove, sp. nov. and Cichlidogyrus vealli Pariselle and Vanhove, sp. nov. Their haptoral anchors remind more of congeners infecting species of Petrochromis than of all Cichlidogyrus spp. hitherto described from other tropheine cichlids. Attachment organ morphology has been proven to mirror the phylogenetic affinities of Cichlidogyrus lineages. Therefore the monogenean parasite fauna of I. loocki reflects this host’s position within Petrochromis. Moreover, I. loocki differs in habitat choice from Petrochromis spp. This study hence confirms that host range and host-specificity in Cichlidogyrus spp. parasitizing tropheines is determined by the host’s phylogenetic position, rather than by a shared ecological niche.