Posterior Basal Body Research Articles

Updating the trachelocercids (Ciliophora, karyorelictea). II. Prototrachelocerca nov.gen. (Prototrachelocercidae nov. fam.), with a redescription of P. fasciolata (Sauerbrey, 1928) nov. comb. and P. caudata (Dragesco & Raikov, 1966) nov. comb.

Summary The morphology and infraciliature of Prototrachelocerca fasciolata ( Sauerbrey, 1928 ) nov. comb, and P. caudata ( Dragesco & Raikov, 1966 ) nov. comb, were studied in live and protargol impregnated specimens. The entire somatic and oral infraciliature consists of dikinetids which have both basal bodies ciliated or only the anterior or posterior ones, depending on the region of the cell. The right side is densely and uniformly ciliated. Its ciliary rows extend onto the left side to the glabrous stripe, where an anterior and posterior secant system are formed, reducing the number of kineties in the narrowed neck and tail region. The left side bears a broad glabrous stripe bordered by slightly irregularly arranged dikinetids having rather stiff, elongated cilia (bristles), possibly forming a continuous, prolate-ellipsoidal (bristle) kinety as indicated by their ciliation. The bristle kinety commences subapically at the right margin of the glabrous stripe, extends posteriorly, then anteriorly at the left, to end up at the right margin again. The dikinetids of the right posterior portion of the bristle kinety have the posterior basal bodies ciliated, whereas the anterior basal bodies are ciliated in its left and right anterior portion. The ends of the bristle kinety meet subapically at the right margin of the glabrous stripe, as indicated by the diametrically (180°) opposed ciliation of the dikinetids. The anterior region (head) of the cell bears a distinct oral apparatus consisting of a circumoral (paroral?) ciliature interrupted on the left side of the head, where 2–4 small, oblique brosse kineties (adorai?) insert in a distinct pocket. The oral dikinetids are associated with conspicuous nematodesmata forming an oral basket, together with the nematodesmal bundles originating from the oralized somatic dikinetids at the anterior end of the somatic kineties. The circumoral ciliature consists of 2–3 rather irregular rows of dikinetids, possibly composed of many short, superimposed or oblique kinety segments. This pattern is basically different from that known from other trachelocercids and thus used to define a new genus, Prototrachelocerca , and a new family, Prototrachelocercidae, which is possibly closely related to the Loxodidae. In addition to the species mentioned above, Tracheloraphis angustivittata is assigned to the new genus: Prototrachelocerca angustivittata ( Borror, 1963 ) nov. comb.

Updating the Trachelocercids (Ciliophora, Karyorelictea). I. A Detailed Description of the Infraciliature of Trachelolophos gigas N. G., N. Sp. and T. filum (Dragesco & Dragesco‐Kernéis, 1986) N. Comb

ABSTRACT. Trachelolophos gigas n. g., n. sp. and T. filum (Dragesco & Dragesco‐Kernéis, 1986) n. comb. (basionym: Tracheloraphis filum) were discovered in the mesopsammon of the French Atlantic coast at Roscoff. Their morphology and infraciliature were studied in live and protargol impregnated specimens. The new genus, Trachelolophos, belongs to the family Trachelocercidae and is unique in having a conspicuous ciliary tuft, which is very likely a highly modified brosse, in the oral cavity. The two species investigated have a very similar infraciliature, differing only in morphometric characteristics and in the nuclear configuration. The entire somatic and oral infraciliature consists of dikinetids which have both basal bodies ciliated or only the anterior or posterior ones, depending on the region of the cell. The right side is densely and uniformly ciliated. Its kineties extend onto the left side to the glabrous stripe, where an anterior and posterior secant system are formed, reducing the number of kineties in the narrowed neck and tail region. The left side bears a narrow glabrous stripe bordered by slightly irregularly arranged dikinetids having rather stiff cilia (bristles), possibly forming an uninterrupted, prolate ellipsoidal (bristle) kinety as indicated by their ciliation. The bristle kinety commences subapically at the right margin of the glabrous stripe, extends posteriorly, then anteriorly at the left, to end up at the right margin again. The dikinetids of the right posterior portion of the bristle kinety have the posterior basal bodies ciliated, whereas the anterior basal bodies are ciliated in its left and right anterior portion. The ends of the bristle kinety meet distinctly subapically at the right margin of the glabrous stripe, as indicated by the diametrically opposed ciliation of the dikinetids. The anterior region (head) of the cell bears a distinct circumoral kinety composed of very regularly arranged dikinetids, associated with nematodesmata forming an oral basket together with the nematodesmal bundles originating from the oralized somatic dikinetids at the anterior end of the somatic kineties. The systematics of trachelocercid ciliates are briefly reviewed and discussed.

Blepharoplast Architecture of the Midstage Spermatid of Riccardia multifida

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

Blepharoplast Characteristics of the Midstage Spermatid of Monoclea gottschei Subsp. elongata

The midstage spermatid ofMonoclea gottschei subsp. elongata displays typicalfeatures of the subclass Marchantiidae. The multilayered structure (MLS) is four-layered (S,-S4). The spline (Sj is comprised of 26 microtubules at its maximum width and has a closed aperture with a predominant width of 3 microtubule diameter equivalents. The outline of the spline is spatulate, resultingfrom the presence of shorter microtubules on the left margin. The underlying lamellar strip (LS, S2-S4) is longitudinally elongate and ovate, 1.8 jtm in length and 0.8 1tm in width, with a right lateral offset or notch. The basal bodies are staggered in insertion and overlapping. The anterior basal body (ABB), at 0.7 ,im, diverges outward from the longitudinal axis of the spline while the posterior basal body (PBB), at 0.8 ,im, is essentially parallel with the spline microtubules. These data indicate a relationship of the monotypic order Monocleales, with the subclass Marchantiidae and also with the genus Blasia. The compact blepharoplast, overlapping basal bodies of similar lengths, LS with right lateral notch and the three-microtubule aperture are shared features that characterize this alliance of liverworts.

IMMUNOLOCALIZATION OF CENTER IN THE FLAGELLAR APPARATUS OF MALE GAMETES OF ECTOCARPUS SILICULOSUS (PHAEOPHYCEAE) AND OTHER BROWN ALGAL MOTILE CELLS1

ABSTRACTCentrin or a centrin homologue was localized using immunofluorescence in the flagellar basal body region in zoids of five brown algal species: Ectocarpus siliculosus (Dillw.) Lyngb., Scytosiphon lomentaria (Lyngb.) Link, Laminaria digitata (Huds.) Lamour., Sphacelaria rigidula (Kütz.) Prud'homme van Reine, and Fucus serratus L. The antigen is restricted to short rods extending along the basal body(ies) and towards the nucleus, which always remains firmly linked to the flagellar apparatus in isolated cytoskeletons. To identify these antigenic sites, pre‐ and postembedding immunogold electron microscopy was applied to male gametes of E. siliculosus. At least three different structures associated with the basal bodies were antigenic: a fibrous structure connecting the proximal end of the posterior basal body to the nucleus (nucleus‐basal body connector), a striated band that links the two basal bodies to each other and is located in the angel formed by them, and amorphous material interconnecting the basal bodies in their most proximal regions. In addiction, specific labeling occurs along the external surface and within the lumen of both basal bodies and in the flagellar transitional region. The possible function of these centrin‐containing structures is discussed.

Blepharoplast Morphology in Treubia tasmanica (Hepaticae: Treubiales)

Detailed ultrastructural analysis and diagrammatic representation of the blepharoplast in Treubia tasmanica reveal a morphology strongly resembling that reported for Haplomitrium. The major distinguishing features common to both include: 1) A very wide spline (with up to 104 microtubules, Treubia's spline is the widest reported for any bryophyte); 2) a spline aperture of the open type; 3) the aperture located on the left side of the spline midline; 4) the anterior basal body located on the left of the spline midline; 5) the left-divergent orientation of the anterior basal body; and 6) nearly total overlap between the anterior and posterior basal bodies. These same six characters exhibit sharply contrasting expressions in the three metzgerialian representatives similarly analyzed. The evidence presentedfor Treubiafurther supports the isolated position of the group and its elevation to ordinal rank. It also reveals an important affinity with the calobryalian line. The Treubiaceae is a small family of liverworts consisting of only two extant genera: Treubia with seven species (Schuster & Scott 1969) and Apotreu- bia with two (Schuster 1984). The initial description of the generic type, Treubia insignis Goebel (1891), and subsequent morphological studies, e.g., those by Campbell (1916), Griin (1914), Schuster and Scott (1969), and Wijk (1928), have shown the members of the Treubiaceae to be anacrogynous while having an intermediate position between the thallose and foliose conditions. Further, this unusual family has long been viewed as having an isolated position in the Metzgeriales; however, the interpretations of its affinities within that order have been largely con- jectural (for examples see the taxonomic mono-

COMPARATIVE ULTRASTRUCTURAL STUDIES OF SPERMATOGENESIS IN THE METZGERIALES (HEPATOPHYTA) II. THE BLEPHAROPLAST OF BLASIA PUSILLA

As in other hepatics, the young spermatid of Blasia pusilla contains a well‐developed blepharoplast comprising a four‐layered multilayered structure (MLS) and two overlying dimorphic basal bodies. The asymmetrical spline (S1 or upper stratum of the MLS) numbers 20 or 21 microtubules (MTs) at its anterior tip and reduces to eight at the posterior limit of the lamellar strip (LS). Behind this the shank of the spline is five or six tubules in width over most of its length, approximately one revolution of the circumference of the gamete. The three‐microtubule spline aperture underlies the anterior basal body and like those of most hepatics, it is closed at its anterior end. The asymmetrical LS (approx. 2.0 μm in length) is characterized by a right‐hand posterior notch which lies below the spline aperture at the region of the cartwheel configuration of the anterior basal body (ABB). The staggered dimorphic basal bodies overlap for approximately one third of their lengths. Both lie parallel to the long axis of the spline. As in other hepatics, the ABB (1.2 μm in length) is subapical and comprises an anterior hub extension with progressive rearward additions of lateral, dorsal and ventral triplets. Over most of its length (2.1 μm) the longer posterior basal body (PBB) consists of a distinct central hub and three ventral triplets. Transition zones of both basal bodies contain stellate configurations into which the two central axonemal MTs frequently extend. The blepharoplast of Blasia shows several features in common with leafy, simple thalloid and complex thalloid liverworts. Compared with the few Metzgeriales observed thus far, the LS is less elongate and the basal bodies less staggered. Dimensions of basal body components and spline dimensions, however, are comparable to those of most leafy and thalloid hepatics. Striking similarities with the complex thalloid liverworts include a posterior notch in the LS and a spline aperture three MTs wide.

Comparative Studies of Spermatogenesis in the Bryopsida. III. Blepharoplast Morphology in Thuidium delicatulum

Ultrastructural observations of the spermatids of Thuidium delicatulum reveal a blepharoplast comprising a multilayered structure of the typical four-layered type and two super- posed, overlapping basal bodies. The longitudinally elongated lamellar strip is approximately rhom- boidal, 2.6 ,m long and 0.5 Cm wide. Most commonly, the spline comprises 14 microtubules at its widest region. These are separated into two sets (10 at left andfour at right) by a 3 ,m long aperture of the open type. The aperture is three microtubule-diameters wide along its midregion, narrowing to only one at its anterior end. The anterior basal body is 2.1 ,im long and lies directly above and parallel to the spline aperture. The posterior basal body is 7.0 gm long and diverges posteriorly in association with the left marginal microtubule of the spline. The stellate patterns, each measuring 46 nm in length, are the shortest reported for any bryophyte. Although differing substantially in lamellar strip morphology and overall dimensions, the blepharoplast of Thuidium shares more features with that of Funaria than with those of Archidium, Polytrichum or Sphagnum.

Comparative Studies of Spermatogenesis in the Bryopsida. II. Blepharoplast Morphology in Archidium tenerrimum Mitt.

A micrographic and diagrammatic representation of blepharoplast structure in the pygmy moss Archidium tenerrimum Mitt. (Bryopsida: Archidiales) is presented. The morphology of the blepharoplast conforms generally to that of Funaria, each having the open-aperturate type of spline. The Archidium spline comprises 24 microtubules at its widest region. Flanked on the right side by six microtubules, the aperture of the spline is two microtubule-diameters wide over most of its length, increasing to three for a short distance at the anterior end. The multilayered structure exhibits three rather than four strata. Much of the right-lateral margin of the lamellar strip extends beyond the spline for a distance of up to 90 nm. The basal bodies are unequal in length. The posterior basal body is highly unusual in that the forward-extending central hub ter- minates at approximately the same level as that of the anterior basal body. In overall length, the posterior basal body measures 5 lim and is about four times longer than the anterior basal body. Beneath the blepharoplast the wide anterior tip of the nucleus lies juxtaposed to the truncated posterior end of the lamellar strip and subtending mitochondrion.

The blepharoplast ofHypnum

AbstractUltrastructural analyses of mid-stage spermatids of Hypnum jutlandicum and H. mammillatum reveal a maximally structured blepharoplast closely similar in most respects to the other moss taxa previously investigated. The multilayered structure is four-layered and the dimorphic basal bodies highy staggered. The latter are inserted into the gamete in a slightly staggered subapical position. Both are longer than those reported for the majority of mosses and hepatics. Like other true mosses, the posterior basal body diverges from the longitudinal axis of the spermatid and is associated with a solitary microtubule which is equally divergent from the main body of the spline. In contrast to previous reports on other mosses, the stray microtubule of Hypnum is here interpreted as remaining separate from the spline, i.e., it does not converge posteriorly with the body of the spline.The lamellar strip of Hypnum is roughly oblong in outline with an acute anterior tip which extends beyond the spline microtubules...

The absolute configuration of the flagellar apparatus in zoospores from two species ofLaminariales (Phaeophyceae

We examined the zoospores produced by the unilocular sporangia ofLaminaria digitata (L.) Lamour. andNereocystis luetkeana Post. & Rupr. by serial sectioning to determine the absolute configuration of their flagellar apparatuses. The basal bodies, which are interconnected by three striated bands, lie parallel to the ventral face of the zoospore, and the posterior basal body always is found to the right of the anterior basal body when the cell is viewed from the ventral face, anterior end up. The four rootlets associated with the basal bodies include a major anterior rootlet of about seven microtubules extending from the anterior basal body along the ventral face towards the apex, a five-membered bypassing rootlet that passes ventral to the basal bodies and is connected to the posterior basal body by a posterior fibrous band, and two short rootlets having a single member each, the minor anterior and posterior rootlets. We consider the configuration observed here to be typical of most phaeophycean motile cells. The flagellar apparatus features suggest a considerable phylogenetic difference between thePhaeophyceae and other classes of chlorophyll c-containing organisms.

ULTRASTRUCTURE OF SWARMERS IN THE LAMINARIALES (PHAEOPHYCEAE). I. ZOOSPORES1

ABSTRACTZoospores of 17 species in 14 genera of Laminariales, collected in the northeast Pacific Ocean, were studied by electron microscopy. These zoospores are unique in the brown algae in lacking both an eyespot in the single chloroplast and any associated swelling at the base of the shorter, posterior flagellum. Spores of all species examined possess a distal whiplash portion on the longer, mastigoneme‐bearing anterior flagellum. This appendage may sometimes be as long as the mastigoneme‐bearing portion of the flagellum, but it is only seldom preserved in the preparations for electron microscopy. A microtubular cytoskeleton is probably responsible for maintaining the shape of the spore. It consists of a short band of about 10 microtubules between the two basal bodies, scattered tubules converging at the anterior of the spore, a band of 7–9 tubules directed anteriorly from the anterior basal body, and a band directed posteriorly from the posterior basal body. These anterior and posterior bands may form one continuous band looping around the periphery of the spore. Variation with possible taxonomic significance was found in the ultrastructure of vesicles which apparently contain adhesive material, and which are extruded through the plasmalemma when the zoospores settle.

STUDIES OF SPERMATOGENESIS IN THE HEPATICAE V. BLEPHAROPLAST DEVELOPMENT IN MARCHANTIA POLYMORPHA

Coaxial centrioles and a microtubule organizing center (MTOC) constitute each centrosome in spermatid mother cells of Marchantia polymorpha. During cell division the centrosome separates at its midregion and the two centrioles undergo a planar rotation that brings them to lie somewhat staggered and nearly parallel with their proximal ends embedded in osmiophilic granular material similar in appearance to that of the MTOC. Microtubules of the multilayered structure (MLS) arise in this material below the posterior centriole and parallel to its long axis. The rotation of centrioles and the initiation of S1 tubules below the posterior centriole determine polarity of the incipient blepharoplast. Lower MLS strata are formed under the anterior centriole by the compaction of granular, osmiophilic matrix. Formation and growth of S2 vertical lamellae occur at the left front edge of the MLS in association with MTOC‐like matrix localized near the cell membrane. The MLS enlarges to about 0.4 μm wide by 0.6 μm long and is ovoid in outline except for a short distal projection underlying the posterior centriole. Subsequently the lamellae are transformed into homogenous, osmiophilic matrix that contributes directly to the expansion of all MLS strata including microtubules. The stratum of lamellae is interpreted as a planar MTOC subject to morphogenetic control. Each of the four strata grows proximally while the tapering distal projection lengthens beneath the posterior basal body. Dense matrix above the MLS, apparently elaborated by the S2 layer, is organized into cartwheel and triplet components of the basal bodies’ proximal extensions. Organization of triplet tubules proceeds from proximal to distal toward preexisting triplets. Osmiophilic matrix contributes to the formation of microtubule keels and osmiophilic crests and may serve as a cementing material that stabilizes the spatial relationships of blepharoplast components. After full expansion of the MLS’ lower strata, the S2 layer is reorganized into lamellae. Flagellar growth in Marchantia is postulated to involve a process whereby subunits or their precursors are elaborated by the MLS, translocated to the distal end of the flagellum and incorporated into the axonemal tubules. When MLS microtubules elongate to form a long, narrow band, the distal half of the S2 layer is again in the osmiophilic matrix state.

Spermatogenesis in Polytrichum juniperinum

In the mature sperm of Polytrichum, the nucleus contains only condensed chromatin. The apical body is as long as the posterior basal body, and the anterior basal body remains short. The microtubules that were part of the multilayered structure persist to form the filamentous appendage of the mature sperm. The cytoplasmic remnant contains the plastid and a few mitochondria that did not participate in the formation of the apical body.

Spermatogenesis in Polytrichum juniperinum

Spermatogenesis in Polytrichum juniperrinum includes a series of precise and coordinated morphogenetic movements among the organelles of the androcyte. The basal bodies, the underlying microtubules, and the multilayered structure (MLS) are positioned as an integrated unit at the periphery of the cell, and the nucleus migrates into contact with them. The shape of the nucleus begins to change, with the formation of an anterior projection, or beak. The mitochondrial sheath that has coalesced on the plastid divides to form the apical body, and elongation of the nucleus begins. The posterior basal body and one microtubule undergo lateral displacement from the rear forward, as elongation of the nucleus and the microtubules continues. The mitochondrial mass that is now the apical body grows rearward along the side of the elongated nucleus, and the two groups of microtubules in the MLS rearrange themselves. The lower elements of the MLS also participate in the morphogenetic rearrangement. By the time the nucleus has elongated once around the cell and the apical body has begun it s rearward growth, the lower elements of the MLS are found only beneath the anterior basal body. Subsequently these layers disappear from this location also.