Meeting Abstract

P1.55  Tuesday, Jan. 4  Building a Model Organism: Major Embryological Events of the Mite Archegozetes longisetosus BARNETT, A.A.*; THOMAS, R.H.; Southern Illinois University Carbondale; Southern Illinois University Carbondale

Development of acarine (mites and ticks) appendages, neural tube, hindgut, midgut, and the reproductive system is very poorly understood. In order to clarify how these major morphological events unfold in acariform mites, we followed the development to the oribatid mite Archegozetes longisetosus from the early segmentation of the prelarval stage using DAPI staining and time-lapse microscopy, and compared these events to past studies of other arachnids. As in other studied acarines, segmentation of the germ band begins when both the acron and telson are located dorsally, while the germ band is split into two lateral halves. Delineation of the chelicerae is delayed in comparison to the other prosomal appendages. As opisthosomal segmentation occurs, the opisthosoma moves to a ventral position and folds anteriorly in a manner similar to spiders. Unlike all other studied acariforms, the opisthosoma of Archegozetes displays brief physical segmentation, which is lost following the ventral migration of the opisthosoma. Archegozetes neural development is similar to that of ticks, in which the ventral nerve cord is formed by the lateral fusion of the two halves of the germ band. These movements also result in the formation of the proctadeal invagination as well the fusion of the prosomal and opisthosoma to form the idiosoma. The development of the midgut of Archegozetes differs from that of ticks in that the posterior midgut rudiment does not form malphigian tubules. The anlagen of the oviducts were observed and appear to develop in a manner similar as that of ticks. These findings clarify major morphological events in acarine embryogenesis and help to establish Archegozetes longisetosus as a model acarine in the molecular age.