Ref ID : 6568
Y.C. Zhang and J.G. Baldwin; Ultrastructure of the postcorpus of the esophagus of Teratocephalus lirellus (Teratocephalida) and its use for interpreting character evolution in Secernentea (Nematoda). Can.J.Zool. 79:16-25, 2001
Reprint
In File
Notes
The ultrastructure of the postcorpus of the putative outgroup of Secernentea (Nematoda), Teratocephalus lirellus (Teratocephalida), is compared with previous observations of representative species Zeldia punctata (Cephalobina), Caenorhabditis elegans (Rhabditina), and Diplenteron sp. (Diplogastrina) in order to interpret the evolution of feeding structures within Secernentea. The postcorpus of T. lirellus consists of 6 marginal, 13 muscle, 3 gland, and 11 nerve cells. In both T. lirellus and Z. punctata, one duct from each of two subventral glands opens into the esophageal lumen at the junction of the isthmus and the basal bulb, whereas in C. elegans and Diplenteron sp., homologous openings are at the posterior end of the median bulb. Caenorhabditis elegans and Z. punctata each have two additional glands that open within the basal bulb. The postcorpus of each taxon has four anterior-to-posterior layered sets of radial muscle cells, except in Diplenteron sp., which lacks a grinder and has homologs to the anterior two sets only. The anterior set of muscles of T. lirellus and Z. punctata includes six mononucleate cells, whereas the homolog in C. elegans and Diplenteron sp. includes three binucleate cells. Evaluation of character polarity defines Rhabditina and Diplogastrina as sister taxa, and suggests that the character of five glands may result from functional convergence.