The epicaridium larvae of Paragigantione species (Isopoda: Epicaridea: Bopyridae) have external yolk sacs: transfer of the genus to Pleurocryptellinae, description of two new species in the genus and a new species of hyperparasite (Isopoda: Epicaridea: Cabiropidae)

Syst Parasitol (2024) 101:70 https://doi.org/10.1007/s11230-024-10190-z The epicaridium larvae of Paragigantione species (Isopoda: Epicaridea: Bopyridae) have external yolk sacs: transfer of the genus to Pleurocryptellinae, description of two new species in the genus and a new species of hyperparasite (Isopoda: Epicaridea: Cabiropidae) Christopher B. Boyko · Jason D. Williams · Gianna Sancetta Received: 25 July 2024 / Accepted: 17 September 2024 © The Author(s) 2024 Abstract The epicaridean isopods previously known to have epicaridium larvae with posterior yolk sacs were species of Pleurocryptella Bonnier, 1900 and a new subfamily, Pleurocryptellinae, was recently erected for this genus. Epicaridium larvae bearing posterior yolk sacs are newly reported from two species of the genus Paragigantione Barnard, 1920 which is transferred from Pseudioninae to Pleurocryptelline on the basis of this and other shared characters of adult males and females with species of Pleurocryptella. Two new species of Paragigantione are described, one from the northeast Atlantic based on type material that was misidentified as belonging to the type species of the genus, P. papillosa Barnard, 1920 and a second from off New Zealand. One specimen of the New Zealand species had a cryptoniscus larva of a new species of hyperparasite of the genus Bourdonia Rybakov, 1990 in the marsupium while another had a species of Duplorbis (Rhizocephala); the former is described based on this material as well as a specimen from a specimen of Pseudione cf. fibriata Richardson, 1910 from New Zealand. Keys to C. B. Boyko (*) · J. D. Williams · G. Sancetta Department of Biology, Hofstra University, Hempstead, NY 11549, USA e-mail: C. B. Boyko Division of Invertebrate Zoology, American Museum of Natural History, New York, NY 10024, USA species of Paragigantione for both males and females are provided. Introduction Parasitic isopods of the family Bopyridae (currently 648 species; Boyko et al., 2024) infest a range of crustaceans as definitive hosts including a diverse array of squat lobsters (Boyko et al., 2012). Recently, the aberrant genus Pleurocryptella Bonnier, 1900 was placed in its own subfamily, Pleurocryptellinae, due to females having oostegites on the sixth and seventh pereomeres, anterior and posterior lobes of the first oostegites rounded, males with segmented maxillipeds, well-developed pleopods and articulated uropods, and epicaridium larvae having posterior yolk sacs (Williams et al., 2024), many of which have historically been interpreted as primitive characters (e.g., Shiino, 1952, 1965; Markham, 1986). No single one of these characters was unique to Pleurocryptella except the presence of posterior yolk sacs on the larvae. Examination of New Zealand and Florida specimens of species belonging to the genus Paragigantione Barnard, 1920 revealed epicaridium larvae that all also possess posterior yolk sacs. All species of Paragigantione also share with those of Pleurocryptella having the anterior and posterior lobes of the first oostegites rounded and males with segmented Vol.: (0123456789) 70 Page 2 of 20 maxillipeds, well-developed pleopods and articulated uropods. However, females of species of Paragigantione do not have oostegites on the sixth and seventh pereomeres and the diagnosis of Pleurocryptellinae must be modified to accommodate this character state variability. Based on adult and larval characters, Paragigantione is therefore transferred from Pseudioninae to Pleurocryptellinae. In the present paper we report on the adult (female and male) and larval (epicaridium) morphology of a new species of Paragigantione found parasitizing the squat lobster Gonionida rubrimana (Ahyong) as well as an unidentified munidid. We also describe the epicaridium larvae of Paragigantione americana (Markham, 1974b) for the first time and identify specimens of Paragigantione papillosa Barnard, 1920 sensu Bourdon (1981) as a new species from the eastern Atlantic. Keys to species of Paragigantione for both males and females are provided. In addition, one female specimen of the new Paragigantione species from New Zealand contained a hyperparasitic isopod which is described herein as a new species of Bourdonia Rybakov, 1990 based on the cryptoniscus larval stage; a second specimen of this hyperparasite was found infesting a female Pseudione cf. fibriata Richardson, 1910. This is the first description of a hyperparasitic isopod from any species of Paragigantione. Material and methods Carapace lengths (CL) of hosts were measured using calipers. Parasite sizes are given as maximal total length (TL). All measurements were made with an ocular micrometer, from drawing tube sketches, or from scale bars in SEM images. Original line drawings were made by using drawing tubes attached to Olympus compound (Olympus CX41) and dissecting microscopes (Olympus SZX12). Adobe Illustrator and a Wacom Cintiq pen display was used to trace original sketches and produce final figures. Light micrographs were created with a Macropod Pro kit (MacroscopicSolutions) and resulting pictures were aligned and stacked with the focus stacking software Zerene Stacker (10–20 images from bottom to top of specimens). For Scanning Electron Microscopy (SEM) preparation of epicaridium and cryptoniscus larvae, specimens were dehydrated in an ascending ethanol Vol:. (1234567890) Syst Parasitol (2024) 101:70 (EtOH) series ending with 100% EtOH. Specimens were then dried in a Samdri 795 Critical Point Dryer (Tousimis, Rockville, MD, USA), mounted on aluminum stubs, coated with gold using an EMS-550 Sputter coater (Electron Microscopy Sciences, Hatfield, PA, USA), and viewed with a FEI Quanta 250 SEM (Thermo Fisher Scientific, Waltham, MA, USA). Specimens are deposited in the Muséum National d’Histoire Naturelle, Paris (MNHN), Voss Marine Invertebrate Collections, Rosenstiel School of Marine and Atmospheric Science, University of Miami (UMML), and the National Institute of Water & Atmospheric Research Ltd (NIWA), Wellington, New Zealand. References are provided for taxonomic authorities of parasite taxa but not for those of hosts. Systematics Order Isopoda Latreille, 1816 Suborder Epicaridea Latreille, 1825 Superfamily Bopyroidea Rafinesque, 1815 Family Bopyridae Rafinesque, 1815 Subfamily Pleurocryptellinae Williams & Boyko in Williams, Boyko & Stewart, 2024 Type genus.— Pleurocryptella Bonnier, 1900. Other included genus.— Paragigantione Barnard, 1920 Emended diagnosis.– Female ovate-elongate, body distorted; head bilobed or not bilobed; frontal lamina present. Eyes absent. Maxilliped without palp or with setose articulated and segmented palp. Barbula with two long smooth lobes or one long lobe and one small nub or one long smooth lobe on each side, median region smooth. Five or seven pairs of oostegites; oostegite 1 with ovate posterior lobe, smaller, subequal or larger than anterior lobe; internal ridge smooth. Coxal plates, dorsolateral bosses and (...truncated)