Biological Journal of the Linnean Society, 2002, 75, 187-217. With 16 figures Brooding in cocculiniform limpets (Gastropoda) and familial distinctiveness of the Nucellicolidae (Copepoda): misconceptions reviewed from a chitonophilid perspective RONY HUYS FLS1*, PABLO J. LÓPEZ-GONZÁLEZ2, ELISA ROLDÁN3 a n d ÁNGEL A. LUQUE3 1Department of Zoology, The Natural History Museum, Cromwell Road, London SW7 5BD, UK 2Departamento de Fisiología y Zoología, Facultad de Biología, Universidad de Sevilla, Reina Mercedes, 6,41012 Sevilla, Spain 3Laboratorio de Biología Marina, Departamento de Biología, Universidad Autónoma, 28049 Madrid, Spain Received 21 January 2001; accepted for publication 16 August 2001 Nauplii, copepodids and adults of a new mesoparasitic genus and species of Chitonophilidae,Lepetellicola brescia nii, are described from the palliai cavity of a deepwater cocculiniform limpet,Lepetella sierrai, collected in the Bay of Biscay and Gulf of Cádiz. Re-examination of the type material of the recently established Nucellicolidae revealed several important observational errors in the original description, such as the oversight of the rootlet system in the adult female and misinterpretations of the tagmosis and antennulary segmentation in the late copepodid. Lamb et al.’s (1996) criteria used to justify the familial distinctiveness of the Nucellicolidae are all invalid. The family is relegated to a junior synonym of the Chitonophilidae on the basis of overwhelming support provided by copepodid and adult morphology. The impact of heterochrony on the body plan of adults and developmental stages is discussed. Phylogenetic analysis supports a basal dichotomy dividing the Chitonophilidae into a mesoparasitic clade, utilizing exclusively polyplacophoran hosts, and a sisterclade grouping genera associated with chitons, prosobranch gas­ tropods and cocculiniform limpets. The presence of maxillipeds and postmaxillipedal apodemes in the adult males of the latter clade is considered as apomorphic rather than plesiomorphic, being the result of incomplete moulting and correlated with the ventral position of the genital apertures.Nucellicola is identified as the sistergroup of the only other endoparasitic genus,Tesonesma, found in the body cavity of chitons. The inferred relationships indicate that host switching has occurred twice in the evolution of the Chitonophilidae. Examination of the antennulary segmentation and setation patterns of copepodidsLepetellicola in andNucellicola unequivocally refutes both the current placement of the Chitonophilidae in the Poecilostomatoida and its alterna­ tive assignment to the Siphonostomatoida. Exclusion from the Poecilostomatoida is reinforced by the absence of a coxo-basis in the antenna. The family is placed with the cyclopoids, providing further evidence for the crown-group status of the Poecilostomatoida within the currently paraphyletic Cyclopoida. A critical review of the published reports of brooding in cocculiniform limpets demonstrated that there is, as yet, no tangible evidence for this phe­ nomenon in either the Lepetelloidea or Cocculinoidea. © 2002 The Linnean Society of London,Biological Journal of the Linnean Society, 2002, 75, 187—217. ADDITIONAL KEYWORDS: Chitonophilidae - heterochrony -Lepetella - Lepetellicola gen. nov. - mollus- can hosts - phylogeny. ““Corresponding author. E-mail:[email protected] © 2002 The Linnean Society of London,Biological Journal of the Linnean Society, 2002, 75, 187-217 187 188 R. HUYS ETAL. INTRODUCTION Vaigamidae and Amazonicopeidae (Thatcher& Robertson, 1984; Thatcher, 1986). These families were Copepods, together with nematodes and insects, are proposed for highly modified fish parasitic copepods the most abundant multicellular organisms on Earth. but in reality are merely specialized lineages of the Current evidence suggests that copepods originated Ergasilidae (Abdelhalimet al., 1993; Amado et al., from the marine hyperbenthic habitat (Huys & 1995). The uncritical acceptance of such familial iden­ Boxshall, 1991) and subsequently spread out in tity, without considering the possibility of the taxon sediments across the entire salinity spectrum. Their being at a terminal node in a larger encompassing current position of world predominance, however, can clade, is potentially naive and unscientific, particu­ be attributed to two principal, recurrent, radiation larly when no attempt has been made to identify the events, i.e. their major habitat shift into the marine hypothetical outgroup. plankton, and the evolution of parasitism. Given their We have used mollusc-infesting copepods as an moderately high host specificity in conjunction with example to demonstrate these misconceptions. The the dazzling spectrum of potential marine hosts, it discovery of a new genus of Chitonophilidae prompted is highly conceivable that parasitic copepods sig­ us to challenge the widely assumed phenomenon of nificantly outnumber their free-living counterparts brooding in cocculiniform limpets, an anatomically in species diversity. It would not be extravagant to and biologically very diverse group currently classified assume that every other kind of marine macro­ as an order or suborder of the streptoneurous Gas­ invertebrate on earth has at least one copepod species tropoda (Haszprunar, 1998). It has also provided new acting as its own personalized parasite. This suc­ morphological information of high phylogenetic signif­ cessful colonization or utilization of virtually every icance, causing serious implications for the taxonomic metazoan phylum has generated a great diversity in status of the Nucellicolidae, a recently proposed family copepod body morphology, which is arguably unparal­ of highly transformed endoparasitic copepods based leled among the Crustacea. Regrettably, this variety solely on autapomorphies. in body plan has also given rise to unfortunate conse­ quences for phylogenetic analysis. More specifically, MATERIAL AND METHODS the highly transformed forms frequently lie at the root of two important misconceptions. Museum collections of Lepetella sierrai D antart & Failure to recognize the extreme modification of Luque (1994) (Mollusca, Cocculiniformia, Lepetel­ certain copepods has repeatedly resulted in them loidea), deposited in the Naturhistoriska Riksmuseet being misinterpreted as part of the host. Garstang in Stockholm (NRS) and the Museo Nacional de (1890) recorded ‘pieces of spawn’ attached to the den- Ciencias Naturales in Madrid (MNCN), were exam­ dronotid nudibranchLomanotus genei (Verany, 1846) ined for parasitic copepods. This material was col­ but these were later identified by Scott & Scott (1895) lected in the Iberian-Moroccan Gulf (BALGIM as egg-sacs of the splanchnotrophid copepodLoman­ expedition, 1984, coordinated by the Muséum oticola insolens Scott & Scott (1895), the urosome of National d’Histoire Naturelle, Paris) and in the Bay which is typically protruding through the host integu­ of Biscay (Fauna Ibérica II expedition, coordinated ment. Another example of such observational error is by MNCN). Host material was obtained from empty shown by Muñozet al. (1996) who figured an unusual or occasionally inhabited, corneous tubes of the penis with ‘... a row of hooks on each side’ in their sedentary polychaete Hyalinoecia tubicola (O.F. redescription of the goniodoridid nudibranchOkenia Müller, 1776), on which Lepetella sierrai lives and luna (Millen et al., 1994). The offset lobate anterior feeds. Copepods were cleared and dissected in lactic end, the traces of segmentation in the posterior part, acid; the dissected parts were mounted on slides the number of lateral processes and the presence of an in lactophenol mounting medium. Preparations were unpaired median outgrowth leave no doubt that the sealed with Glyceel (BDH Laboratory Supplies, supposed penis is an adult female ofIsmaila Bergh, Poole, UK) or transparent nail varnish. All drawings 1867, a genus of endoparasitic copepods (Splanch­ have been prepared using a camera lucida on an notrophidae) typically associated with the kidney, Olympus BH (Hamburg, Germany) or a Leica DMR pericardium or the digestive gland of nudibranch and (Wetzlar, Germany) differential interference contrast sacoglossan opisthobranchs (Huys, 2001). microscope. Both host and parasite specimens were Secondly, failure to place strange copepods in examined with a Philips XL 30 scanning electron existing classifications, often compounded by imper­ microscope (Eindhoven, The Netherlands). Specimens fect dissection and observation, has recently led to the were prepared by dehydration through graded proposal of a number of monogeneric or monotypic acetone, critical point dried, mounted on stubs and families. An example of such undesirable inflation sputter-coated with gold or palladium. of higher categories is illustrated by the families The descriptive terminology is adopted from Huys& © 2002 The Linnean Society of London,Biological Journal of the Linnean Society, 2002, 75, 187-217 F igure 1. Lepetellicola brescianii gen. et sp. nov. A, paratype ? attached to host, dorsal view showing attached dwarf male ($), eggs and spermatophores [e.s., remaining egg string of hatched egg; sp., spermatophore; ov., ovary]; B, same, ventral view showing two dwarf males (<?<?), another two being removed and not illustrated [p.l., posterior lobe]; C, paratype ? attached to host with offspring at different stages of development, dorsal view [co., copepodid; e., egg; ho., host’s integu­ ment; nb young nauplius enclosed in egg membrane; n2,