Original paper
Genitalmorphologie, System und Phylogenie der Weberknechte (Arachnida: Opiliones)
[Genital Morphology, System, and Phylogeny of Harvestmen (Arachnida: Opiliones)]
Martens, Jochen
Entomologica Germanica Band 3 Heft 1-2 (1976), p. 51 - 68
23 references
published: Oct 4, 1976
DOI: 10.1127/entom.germ/3/1976/51
ArtNo. ESP346000301004, Price: 29.00 €
Abstract
The ectodermal part of genitalia in Opiliones consists of the penis, respectively the ovipositor with receptacula seminis. Construction and function of the penes are determined by their equipment with muscles. Fundamentally four types of penes can be distinguished: penes with 3 muscles (Cyphophthalmi), 2 muscles (Troguloidea), 1 muscle (Palpatores with the exception of Troguloidea, Laniatores with the exception of Travunioidea and penes without muscles (Laniatores, except for Travunioidea). In members of the first three groups, the distal section of the penis (glans) is moved by muscles (muscle-tension-principle), in species from the last group, by haemolymph pressure (haemolymph-pressure-principle). Special cases within the groups are discussed: stabilizing extremely thin penes by alternating muscular tension (Nemastomatidae), bending the entire penis stalk (Ischyropsalis C. L. Koch 1939, Trogulus Latreille 1892), stretching of glans (Phalangiinae) and bending of glans by muscular tension (Ischyropsalis, Erebomastridae). It is assumed that the penis type without muscle has developed from one with muscle, and that penes with submerged sclerites and membranes of glans, expanded by haemolymph pressure, represent the highest evolutionary level. This is in accordance with the principle of economisation of function and enhanced efficiency. The different construction types of penes are important phylogenetic characteristics and substantiate the major subdivisions of Opiliones. Only a few changes are necessary: The »tribus« Eupnoi and Dyspnoi of Palpatores are replaced by four superfamilies and the monotypic family Nipponopsalididae is removed from Ischyropsalididae.