Fine structure and phylogenetic significance of a muscular basal bulb in Basiria gracilis Thorne, 1969 (Nematoda: Tylenchidae)
Authors: Baldwin, James G.; Souza, Ricardo M.; Dolinski, Claudia M.
Source: Nematology, Volume 3, Number 7, 2001 , pp. 681-688(8)
Publisher: BRILL
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Abstract:
Classical hypotheses of the phylogenetic position of Tylenchida within Secernentea are evaluated considering the comparative fine structure of the basal bulb of the pharynx of Basiria gracilis, putatively a representative of the most morphologically conserved members of the order. Unlike other Tylenchida examined in detail, B. gracilis has a full complement of nonglandular cells in the basal bulb including 13 radial muscle cells and six marginal cells. With respect to types and numbers of cells, the basal bulb of B. gracilis most nearly resembles representatives of Cephalobina, differing only by three vs five gland cells. There are more muscle cells in the basal bulb of B. gracilis than in representatives of Rhabditina (ten muscles) and Diplogastrina (six muscles). Considering Teratocephalus as a representative of the outgroup (to establish character polarity), B. gracilis appears to retain most of the conserved features of the basal bulb of Secernentea, with the exception of loss of a heavily cuticularised grinder valve or pump.Keywords: EVOLUTION; NEMATODE; PHARYNGEAL GLANDS; PHYLOGENY; SECERNENTEA; TYLENCHIDA; ULTRASTRUCTURE
Document Type: Research article
DOI: 10.1163/156854101753536055
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