The terminology of larval cestodes or metacestodes

5Table 1. Names of larval cestodes utilised by Braun (1894) in one of the earliestsynopses of terminology together and their origins.Group I Cysticerci Original use of term:1. Cysticercus Zeder (1800)2. Coenurus Rudolphi (1819)3. Echinococcus Rudolphi (1819)Group II Cysticercoids Original use of term: Leuckart (1867)Sub-group (a) - with endogenous development1. Polycercus based on the description of a larval cestode in anannelid, Lumbricus, by Metchnikoff (1869) (=Paricterotaenia) (Dilepididae).2. Monocercus based on a cysticercoid from a mollusc, Arionempiricorum, by von Siebold (1850), nowMolluscotaenia (Dilepididae).Sub-group (b) - with exogenous development1. Cercocystis based on cysticercoids developing in a beetle,Tenebrio molitor, described by Stein (1975),probably the larva of Rodentolepis microstoma.2. Staphylocystis based on cysticercoids found in a myriapod,Glomeris limbatus, by Villot (1877), adultStaphylocystis pistillum, in shrews.3. Urocystis based on cysticercoids found in myriapods G.conspers and G. marginata by Villot (1882).4. Cryptocystis based on the larvae of Dipylidium caninum(= Taenia cucumerina) in a louse, Trichodectescanis, described by Melnikov (1869).cercoid. Dollfus (1946) also excluded the athecatetrypanorhynchs (Homeacanthoidea) from the types ofcestodes characterised by a plerocercoid, referring tothem instead as postlarvae. The most comprehensivesummary of cestode life-cycles published in the subsequentdecades, that of Joyeux & Baer (1961), furtherestablished the use of the terms procercoid, plerocercoid,cysticercus and cysticercoid in the westernEuropean literature (Figures 1,2).Skrjabin and colleaguesA significant elaboration of the traditional terms wasmade by Russian workers under the leadership of K.I.Skrjabin. Skrjabin & Mathevossian (1942) divided thedevelopment of the metacestode of hymenolepididsinto six stages: (1) the oncosphere; (2) the megalosphere(with a central cavity termed the primarylacuna); (3) the metamere, subdivided into caput, collum,soma and cerca or cercomer of other authors;(4) scolexogeny, during which the rostellum and suckersbegin development in the caput; (5) the stage of‘invagination’ in which the caput and collum are retractedwithin the soma; and (6) the fully-developedcysticercoid, termed a larvicyst. The term larvicysthad been coined by Skrjabin (1937) to denote anymetacestode of the order Cyclophyllidea, irrespectiveof its final structure. Skrjabin & Mathevossian (1945)also used the spelling ‘larvocyst’.Larvicysts of hymenolepidids were subdivided bySkrjabin & Mathevossian (1942) into various morphologicalcharacters based in part on the work of Villot(1883) (Table 2), the key characters being: (1) presenceor absence of a cercomer; (2) ratio of length ofcercomer to the rest of the cysticercoid; (3) structureof the membranes investing the scolex; and (4) modeof scolex formation (e.g. by budding). The termsthey adopted to describe cysticercoids, taken in partfrom earlier authors, were staphylocyst, urocyst, cer-