Two new species of kidney fluke (Trematoda: Renicolidae) from New Zealand penguins (Spheniscidae), with a description of Renicola websterae n. sp.

Syst Parasitol (2025) 102:26 https://doi.org/10.1007/s11230-025-10219-x Two new species of kidney fluke (Trematoda: Renicolidae) from New Zealand penguins (Spheniscidae), with a description of Renicola websterae n. sp. B. Presswell · J. Bennett Received: 6 December 2024 / Accepted: 6 February 2025 / Published online: 1 March 2025 © The Author(s) 2025 Abstract This study describes Renicola websterae n. sp., a newly identified kidney fluke (Renicolidae: Trematoda) infecting two penguin species from New Zealand, the little blue penguin (Eudyptula novaehollandiae) and the Fiordland crested penguin (Eudyptes pachyrhynchus). Morphological and molecular analyses, including phylogenies based on cox1 and 28S genes, confirmed the distinctiveness of R. websterae. Key morphological features were discerned to be statistically comparable across five developmental stages, facilitating detailed characterization even in less mature specimens. A putative second, genetically distinct Renicola sp. was identified in Fiordland crested penguins and intermediate fish hosts, indicating a potential trophic link, and partly completing the known life cycle. We discuss the fact that kidney flukes have only been found in these two penguins and not in other New Zealand species, and the ecological and host-specificity factors likely influencing parasite distribution. This work represents the first record of a named Renicola species from New Zealand and only the second species found in penguins worldwide. B. Presswell (*) · J. Bennett Department of Zoology, University of Otago, P.O. Box 56, Dunedin, New Zealand e-mail: Introduction Trematodes of the family Renicolidae are found in the kidney tubules and ureters of aquatic birds that prey on molluscs and fishes (Gibson, 2008). Two genera are currently recognised within the family; Renicola Cohn, 1904 and Nephromonorcha Leonov, 1958 (Gibson, 2008). The higher classification of the family has been a matter of some debate (reviewed in Gibson, 2008), but phylogenetic analyses now firmly place the Renicolidae within the superfamily Microphalloidea (Olson et al., 2003). Notwithstanding a number of published identification keys (Dollfus, 1946; Wright, 1954, 1956, 1957; La Rue, 1957; Odening, 1962; Riley & Owen, 1972; Sudarikov & Stenko, 1984; Gibson, 2008), the status of many species remains uncertain. This uncertainty arises from the challenges in observing critical features, primarily due to the overwhelming number of eggs present in the uterus of mature specimens. New Zealand’s penguin species hold significant cultural and ecological importance. The country hosts the world’s largest diversity of penguins, being home to seven of the 19 extant species. Five of these species are endemic to New Zealand and its islands, and all but one are vulnerable or endangered, most with declining populations (Robertson et al., 2021). Our knowledge of the parasite fauna of New Zealand penguins remains little known except for the little blue penguin Eudyptula novaehollandiae (Stephens), whose parasite communities were documented by Bennett et al. (2021). Vol.: (0123456789) 26 Page 2 of 14 The endemic Fiordland crested penguin Eudyptes pachyrhynchus Gray, or tāwaki, primarily inhabits the southwestern coast of the South Island, particularly within Fiordland National Park, but vagrants occasionally appear on shores all around New Zealand. Little blue penguins, known as kororā in New Zealand, are the world’s smallest penguins, and are found on the coasts of southern Australia and New Zealand (HBW & BirdLife International, 2024). Recent morphometric and genetic studies have proposed the existence of two main species, Eudyptula novaehollandiae from the coasts of South Australia and coastal Otago (New Zealand), and Eudyptula minor (Forster) endemic to the rest of New Zealand (Grosser et al., 2015, 2017). All little blue penguins in this study were collected from around the Otago coast; therefore, we have assigned these specimens to E. novaehollandiae (Otago little blue penguin), as opposed to E. minor (New Zealand little blue penguin) (see Grosser et al., 2015, 2017). During an ongoing parasitic study of birds in New Zealand, a number of little blue and Fiordland crested penguins were discovered to harbour trematodes in their kidneys. DNA sequence and morphological comparisons with other species in the genus Renicola confirmed that these specimens were new to science. This study presents a description of the new species using both morphological and molecular techniques, along with phylogenetic analyses based on cox1 and 28S DNA genes, and aims to place the species within the context of the genus. Additionally, a potential second, genetically identified, species from a Fiordland crested penguin is briefly described and included in the phylogenies. We propose a method for artificially recognising five developmental stages of the adult worm, which allows for the morphological description of sub-mature specimens without compromising the accuracy of measurements compared to fully mature adults. This study represents the first report of a named Renicola species in New Zealand, and the second species to be recorded, worldwide, from a penguin host. Syst Parasitol (2025) 102:26 examined for helminths between 2020 and 2024. Birds were donated after death or euthanasia by the Dunedin Wildlife Hospital or Department of Conservation, and were frozen immediately post mortem. Birds were defrosted, the kidneys removed, dissected and examined under a dissecting microscope. Kidney parasites were preserved in 70% ethanol for wholemount, and 96% ethanol for genetic analyses, or formalin for SEM photography. Morphological data Materials and methods Trematodes were stained using iron acetocarmine, dehydrated through a graded ethanol series, cleared in clove oil and mounted in Canada balsam. Measurements were made using ImageJ software (Wayne Rasband, NIH, USA) from photographs taken on an Olympus BX51 compound microscope mounted with DP25 camera attachment. Drawings were made with the aid of a drawing tube mounted on an Olympus compound microscope. For scanning electron microscopy (SEM) specimens were transferred to 2.5 % glutaraldehyde in 0.1 M phosphate buffer, then post-fixed in 1% osmium tetroxide and dehydrated through a gradient series of ethanols, critical-point dried in a CPD030 BalTec critical-point dryer (BalTec AG, Balzers, Liechtenstein) using carbon dioxide, mounted on aluminium stubs, and sputter coated with gold/palladium (60:40) to a thickness of 10 nm in an Emitech K575X Peltiercooled high-resolution sputter coater (EM Technologies, Ashford, Kent, UK). The specimens were viewed with a JEOL 6700 F field emission scanning electron microscope (JEOL Ltd., Tokyo, Japan) at the Otago Centre for Electron Microscopy (OCEM, University of Otago, New Zealand). Voucher specimens were deposited in Te Papa Museum, Wellington, New Zealand. All measurements are in micrometres throughout (...truncated)