Blepharoplast Architecture of the Midstage Spermatid of Riccardia multifida

Abstract

The locomotory apparatus of the midstage spermatid of Riccardia multifida (L.) S. Gray is comprised of the characteristic four-layered multilayered structure (MLS) and two super- posed, staggered but only slightly overlapping, basal bodies. The lamellar strip (LS) is spatulate in outline, 2.7 Am long and 0.42 Am wide, decreasing in width from the right-hand margin. The overlying spline varies from 14-16 microtubules but typically is comprised of 14 at its maximum width. The anterior basal body (ABB), 0.73 Am in length and inserted 0.45 Am from the anterior margin of the spline, overlaps with the posterior basal body (PBB) which is much longer, at 2.74 Am, and located about 1.12 Am from the spline's leading edge. The ABB is essentially parallel with the spline microtubules while the PBB diverges slightly past the left-hand margin. A closed aperture is located to the right of the spline midline beneath the ABB. Blepharoplast characteristics of the midstage spermatid of Riccardia are consistent with the average blepharoplast for the midstage spermatids of the Metzgeriales. Many features of the Riccardia blepharoplast-for example shape of the LS, lengths and stagger of the basal bodies, and number of microtubules comprising the spline-fit well into the midrange for the order. The most diverse of the hepatic orders, the Metz- geriales (simple thalloid liverworts), contains a number of distinct isolated entities (Renzaglia 1982). Most of these elements are represented by 12 fam- ilies currently recognized within the order (Schuster 1984). Primary features that unify the 28-30 metz- gerialian genera include the ontogeny of the vege- tative plant body and the continuous production of archegonia along the dorsal surface of the thallus, i.e., the anacrogynous condition. The interrelation- ships among the various simple thalloid taxa, how- ever, are quite complex and by no means well un- derstood. The discontinuities in structural characteristics exhibited by metzgerialian hepatics are likewise ev- ident in features of the spermatids and spermato- zoids of taxa studied to date. Spermatids of repre- sentatives of four of the seven metzgerialian sub- orders have been studied ultrastructurally: Blasia of the Blasiineae (Carothers 1973; Renzaglia & Duck- ett 1987a,b); Fossombronia and Petalophyllum of