The caudal bursa in the Heligmonellidae (Nematoda: Trichostrongylina). Characterization and hypothesis on its evolution

Abstract

The different patterns of the caudal bursa of the Heligmonellidae (Nematoda) are redefined, taking into account the grouping of rays 2-6 and the sequence of origin of these rays from their common trunk. The type of symmetry of the caudal bursa is also redefined. The following patterns were observed and characterized: the basic patterns: types 2-3, 2-2-1, 1-3-1 and 1-4 and the intermediary patterns: type 2-3 tending to type 2-2-1, type 2-2-1 tending to type 1-3-1, type 1-3-1 tending to type 1-4 and type 2-2-1 tending to type 1-4. An evolutionary interpretation of the patterns is attempted and seems to follow the direction: 2-3 to 2-2-1 to 1-3-1 to 1-4. Seven atypical patterns are described. The caudal bursae were classified based on their symmetry: subsymmetrical, dissymmetrical and asymmetrical. Independently of the type of symmetry, the two latero-ventral lobes may have the same or different patterns. The type of symmetry, the ratio between the two latero-ventral lobes and a characteristic pattern were utilized to characterize the caudal bursae at the level of the genus and the subfamily. The combination of the right/left ratio and the type of symmetry gives heterogeneous results, with no real association between these characters. The most conspicuous asymmetries and dissymmetries were found among the Nippostrongylinae. The most frequent pattern in the Heligmonellidae is the basic type 2-2-1; types 1-3-1 and 1-4 are less frequent but are characteristic of several genera; type 1-4 is absent from the Heligmonellinae. Whatever the pattern, in the Heligmonellidae rays 4 and 5 are the last to diverge from the common trunk of rays 2-6.

Taxonomic revision of the Nippostrongylinae (Nematoda, Heligmonellidae) parasites of Muridae from the Australasian region. The genusOdiliaDurette-Desset, 1973

“…The description of the bursa follows Durette-Desset & Digiani [ 10 ]. Other characters, especially of the bursa and spicules are included in the generic definitions.…”

Boehmiella wilsoni (Nematoda, Heligmosomoidea, Boehmiellidae fam. nov.), found in Amazonian rodents

“…The diagnostic morphological traits of the haemonchids are the ungrouped rays of the lateral trident, the presence of externolateral ray (4) and/or externodorsal ray (8) reaching the edge of the caudal bursa, and hook-shaped deirids. The characteristics of the Haemonchinae are the type 2-1-2 caudal bursa, the mediolateral (5) and posterolateral (6) rays that are either joined or parallel, the ventro-ventral (2) and lateroventral (3) rays with a long common trunk, and the hexagonal buccal opening connected laterally to a hexagonal ring ( Durette-Desset et al, 1999 ; Durette-Desset and Digiani, 2012 ).…”

Guerrerostrongylus marginalisn. sp. (Trichostrongyloidea: Heligmonellidae) from the Guianan arboreal mouse (Oecomys auyantepui) from French Guiana

“…The perception of the overall shape of the caudal bursa of G. marginalis seems to differ from the caudal bursa of other members of Guerrerostrongylus , which was described as ellipsoidal, rectangular, or heart-shaped [ 3 , 18 ]. Irrespective of the interpretation of the shape of the bursa, the overall symmetry in all five species is sub-symmetrical as described in Durette-Desset and Digiani [ 7 ]. Additionally, the number of ridges in the synlophe, the size variation of these ridges, and the posterior end of the females are typical of Guerrerostrongylus .…”

“…Among them, Guerrerostrongylus Sutton and Durette-Desset, 1991 was proposed to include species with a minimum of 40 longitudinal ridges (slender and slightly salient, less numerous toward anterior end); long dorsal ray and ray 6 (postero-lateral); and females with not bent tails, partially covered with an invaginated cuticle [ 20 ]. Species included in Guerrerostrongylus share several traits with species in Hassalstrongylus Durette-Desset, 1971: however, the larger number of ridges in the synlophe and the relatively long size of the dorsal ray of the former have acted as reliable characters [ 7 , 18 , 20 ]. Guerrerostrongylus includes four known species that infect sigmodontine and caviomorph rodents throughout the eastern half of South America.…”