The Reproductive System of Gastrotrichs. III. Genital organs of Thaumastodermatinae subfam. n. and Diplodasyinae subfam. n. with discussion of reproduction in Macrodasyida¹

Abstract

A comparative structural and ultrastructural investigation is made of genital organs of selected, genera of Thaumastodermatidae and their constructions are defined. Two new subfamilies are designated within the family based on reproductive features and other characteristics. The occurrence of bounding epithelia about the gonads, ova and central body region is noted. Paramyosin type muscles are noted for Platydasys. General and specific features of spermatogenesis, oogenesis and fertilization are defined and discussed. The evolution of accessory reproductive organs in Macrodasyida is discussed.

Macrodasyida (Gastrotricha): a cladistic analysis of morphology

“…The order Macrodasyida is well defined in terms of overall morphology and reproductive anatomy, and is usually considered a monophyletic group (Ruppert 1982(Ruppert , 1991Travis 1983). Our analysis clearly supported monophyly (Fig.…”

“…Gnathostomulida and Neodasys were chosen as outgroups because they have figured prominently in previous phylogenetic discussions featuring macrodasyidan gastrotrichs (Rieger & Rieger 1977;Ruppert 1982;. Chuetonotus was chosen as the third outgroup based on the results of a previous molecular study of several gastrotrichs (Wirz et al 1999).…”

“…Monophyly of the Macrodasyida was tested, and an attempt was made to reconstruct the ground pattern and to examine in-group relationships. We also re-evaluated characters used in previous phylogenetic analyses of Gastrotricha (Ruppert 1982;Travis 1983;Hochberg & Litvaitis 2000a) and formulated hypotheses about evolutionary character transformations within the order. Our overall intent was not to reorder macrodasyidan systematics but to examine the validity of the included families using cladistic methodology and to propose future directions for inquiry that might lead to better systematic and phylogenetic resolution.…”

“…Few morphologists have attempted to reconstruct relationships within the phylum (Ruppert 1982;Travis 1983) or to reconstruct its ground patterns (reproductive system of specific families, Ruppert 1978a,b;myoepithelial pharynx, Ruppest 1982;muscle, Travis 1983;protonephridia, Neuhaus 1987). A single molecular study using 18s rRNA sequences found a paraphyletic Chaetonotida-2 macrodasyidans clustered with 3 chaetonotids (Wirz et al 1999).…”

Ultrastructural observations on the spermatozoa of a species of Lepidodasys (Gastrotricha, Macrodasyida)

“…In particular, Lepidodasys, despite it is the type genus of the family, diVers from the other genera for a number of morphological characters: the complexity of the cuticle, the presence of Y-cells containing myoWlaments, the non-striated pharyngeal myo-epithelium, the absence of circular musculature in the lateral body regions and the lack of pharyngeal pores (Rieger and Rieger 1977;Ruppert 1978). Even the ultrastructure of the mature spermatozoon diVers in showing a ribbon-like nucleus, and in lacking any accessory structure around the axoneme (Guidi et al 2004;Marotta et al 2005).…”