On the Fine Structure of Gastrotrichs with Description of Chordodasys antennatus sp.n.¹

Abstract

Rieger, R. M. the fine structure of gastrotrichs u'ith description of Chordodasys antennatus sp.n. 2001. Scr. 3 (5-6): [219][220][221][222][223][224][225][226][227][228][229][230][231][232][233][234][235][236][237] 1974.-Chordodasys antennatus sp.n. is described from sublittoral sediments off the US Atlantic Coast. This species has been also studied by transmission electron microscopy. The new species is particularly characterized by extremely enlarged sensory processes which have a segmented appearance. The fine-structure of the chordoid organ, characteristic of the genus Chordodasys, has been studied in both known species of this genus. According to this investigation the chordoid organ consists of plate-like muscle cells, surprisingly similar to the notochord of Amphioxus. Particular emphasis has been made in this study to elucidate the fine structure of the body cavity and the system of lateral and central chambers as described by Remane in 1936. The electron micrographs substantiate the fact that gastrotrichs exhibit an acoelomate construction of their body cavity. The systematic position of the new species and the genus Chordudusys is discussed in the light of the new ultrastructural information. Occurrence Specimen IS I was collected a t 97 m depth in sandy shell off Beaufort, N.C. (Eastward Cruise E-10-70, Station 14452, a t 34"17' N and 76O7.7' W, May 1970, Courtesy Dr B. Coull). Sediment analysis with standard sieve series: 4.0 mm-0.480,!, 2 4 mm=2.08%, 1-2 mm=8.74%, 0.5-1 mm = 29.62 %, 0.25-0.5 mm = 51.21 %, 0.125-0.25 mm= 6.74 %, 0.063-0.025 mm=0.46%, 0.037-0.063 mm=0.1304,, silt-0.037 mm=0.07%, silt=0.27%,, clay-0.57%.

Comparative immunohistochemistry of the cerebral ganglion in Gastrotricha: an analysis of FMRFamide-like immunoreactivity in Neodasys cirritus (Chaetonotida), Xenodasys riedli and Turbanella cf. hyalina (Macrodasyida)

“…Likewise, the results also attest to the basal position of Xenodasys, a group of gastrotrichs that once shared taxonomic propinquity to other basal macrodasyidans based on the retention of plesiomorphic characteristics (as members of the Dactylopodolidae, see Todaro et al 2006). Furthermore, these results place species of Xenodasys in a basal position relative to other members of Xenodasyidae, e.g., species of Chordodasiopsis (the senior synonym of Chordodasys), which are known to possess only a single pair of major nerve cords (see Rieger et al 1974). …”

Unusual spermatozoa and reproductive modalities ofXenodasys eknomios(Gastrotricha: Xenodasyidae)

“…An elongate frontal organ, lateral to the intestine and opening into a ventrolateral pore, has been described in X. riedli (Schoepfer-Sterrer 1969) and also in C. antennatus (Rieger et al 1974). However, in both species it appears larger and more complex than the simple, rounded frontal organ of X. eknomios, since two distinct parts of it can be clearly recognized (receptaculum seminis and bursa).…”

“…Xenodasyidae; Todaro et al 2006). The fact that male pores were not detected on the body surface in X. riedli (Schoepfer-Sterrer 1969), as in X. eknomios and C. antennatus (Rieger et al 1974), could be related to their extremely small size or their possible Figure 2. Frontal organ of Xenodasys eknomios observed with transmission electron microscopy (TEM).…”

“…The hermaphroditic reproductive system of Xenodasys eknomios, X. riedli and Chordodasiopsis antennatus (Rieger et al 1974) is characterized by the possession of two club-like testes that extend into sperm ducts, paired caudal ovaries, and a frontal organ. This is likely also true for X. sanctigoulveni (Swedmark 1967), although there are no data on Figure 1.…”

“…Todaro et al (2006) made the following amendments: (a) the transfer of the type species of the genus Chordodasys (i.e. C. riedli) to Xenodasys, (b) the establishment of a new genus, Chordodasiopsis, to allocate the single remaining Chordodasys species (Chordodasys antennatus Rieger, Ruppert, Rieger & Schoepfer-Sterrer, 1974), and (c) the institution of the new family Xenodasyidae to allocate both Xenodasys and Chordodasiopsis. The new family was separated from the remaining Dactylopodolidae (i.e.…”