Contractile tissues in the cirri of ancient crinoids: criteria for recognition

Stalked isocrinid and 'stalkless' comatulid crinoids are able to relocate by crawling on or swimming with their muscular arms. Reattachment is achieved using cirri containing contractile tissues which produce aboral flexure. The following cirral adaptations for active attachment were observed during a SEM study of two comasterid comatulids, Davidaster rubiginosa (Pourtalès) and D. discoidea (Carpenter): synarthrial articulations; fulcral ridges corresponding to short axes of ossicles; cirri flattened laterally; each cirrus with a claw at the tip and an aboral attachment pad; cirri serrated aborally and distally. Epizoans are only able to encrust single ossicles in actively motile cirri. These adaptations are associated with crinoids that have muscular arms which are used in relocation. Such a suite of characters is unknown in Palaeozoic crinoids; the ability to relocate only evolved in crinoids during the Mesozoic.□ Crinoids, cirri, comatulids, evoiution, functional morphology .     

The skeleton of the stalked stages of the comatulid crinoid Antedon bifida (Echinodermata)

Summary The cystidean calyx of Antedon bifida (Pennant, 1777) consists of two superposed series of five inter-radially located plates called basals (lower plates) and orals (upper plates). A single radianal and five radial plates develop in early pentacrinoids. They are radially located between the orals and the basals and alternate with them. During pentacrinoid life, radials grow continuously while orals progressively regress. Basals fuse to the proximal forming the so-called rosette, and the radianal grows till the anal cone is formed and then regresses. The first primibrachials arise in 25 day pentacrinoids. Arms of detached juveniles usually have 13 secundibrachials, with IIBr13 each having a developing pinnule. No infrabasal develops between the series of basals and the upper columnal.During pentacrinoid life, the stalk progressively changes from homeomorphic to xenomorphic while most columnal articulations change from symmorphies to synarthries. Synarthrial fulcral ridges can rotate about 60° from one columnal articulation to another, allowing the stalk to be flexible in every direction. Formation of new columnals is continuous until the proximal appears (i.e. in 65 day pentacrinoids). The number of columnals in the fully-formed pentacrinoid stalk varies from 17 to 24 depending on the individual. Developing cirri are seen in 70 day pentacrinoids. Detached juveniles have two well-developed series of five cirri, which usually consist of ten cirral ossicles.     

A new type of stalk articulation in the sea lily genus Vityazicrinus (Echinodermata,Crinoidea) and its ontogeny

A new stalk articulation named pseudo-synarthry is here described from the mesistele of Vityazicrinus petrachenkoi, a rare deep-sea crinoid from the Central Pacific Ocean. Pseudo-synarthries have an articulation facet displaying a general structure closely resembling the morphology of the true synarthry, i.e., with a strong bilateral symmetry and deep ligament depressions. Pseudo-synarthries differ from synarthries in lacking a hinge-like fulcral ridge and developing two additional depressions bordered by prominent crescent ridges at opposite sides of the bilateral symmetry axis. Pseudo-synarthries develop in the mesistele below a proxistele articulated by symplexies of 6–8 crenular units. Distally, subsidiary radial ridges appear on the outer edge of ligamentary depressions and tend to multiply, transforming pseudo-synarthries into multiradiate syzygies, as previously observed in the genus Guillecrinus. A chaotic polymeric pattern locally appears in the proxistele and mesistele, which tends to develop into a holomeric pattern during growth, devoid of any visible trace of ossicle fusion. Both early columnal ontogeny in comatulid larvae and the transition from a polymeric to a holomeric pattern in the guillecrinid stalk lead to the rejection of the hypothesis that the monomeric columnal results from the fusion of pre-existing ossicles. Among Guillecrinidae, pseudo-synarthries constitute derived characters that are unique to the Vityazicrinus mesistele. The development of radial subsidiary ridges in the distal stalk corresponds to a synapomorphy shared by Vityazicrinus and Guillecrinus, the two only genera currently attributed to this family. Pseudo-synarthries in Vityazicrinus appear as advanced stalk articulations adapted to the deep-sea environment, which are unknown from the fossil record.     

The improbability of a muscular crinoid column

Donovan, Stephen K. 1989 07 15: The improbability of a muscular crirroid column. Lethaia , Vol. 22, pp. 307–315. Oslo. ISSN 0024–1164.
It has sometimes been assumed that the stems of ancient crinoids were muscular. However, the only contractile fibres found in the stems of extant crinoids are in the cirri of isocrinids and comatulids. On uniformitarian grounds, it is improbable that any ancient crinoid had tissues in the stem that would have aided active orientation, apart from the non-muscular catch connective tissue. This conclusion is supported by a detailed functional analysis of the various forms of column and cirrus articulation. The axial canal has been seen as the probable site of any column musculature, but this is functionally impossible with symplexial and synostosial articulations, both of which are poorly adapted for muscular flexure. Columns that articulate synarthrially are much more flexible, but modern bourgueticrinids lack any stem musculature, despite having such stalks. The only crinoid columns that were functionally adapted to utilize contractile fibres were those of certain coiled-stemmed taxa, where the axial canal was not in the plane of the synarthrial fulcra. However, it is unlikely that such stems, even if muscular, possessed any advantage over a non-muscular column. The only pelmatozoans with a probable muscular column were not crinoids, but the glyptocystitid rhombiferans. * Crinoids, stem, columnal, cirrus, catch connective tissue, contractile fibres, functional morphology .     

Thoracic structure and enrolment style in middle Cambrian Eccaparadoxides pradoanus presages caudalization of the derived trilobite trunk

Abstract: The ability to enrol effectively evolved several times among trilobites. Here, we show that, unlike most redlichiid trilobites that could not enrol, both morphotypes of Eccaparadoxides pradoanus from the middle Cambrian of Spain enrolled so as to enclose most of the ventral surface beneath the exoskeleton and possessed specialized articulating devices that facilitated this behaviour. The holaspid thorax of all E. pradoanus was divided into two principal regions. The boundary between these marked a transition from anterior segments with short pleural spines, fulcra and ridge‐and‐groove inner pleural regions to posterior segments with longer, acuminate pleural spines that lack fulcra and inner pleural regions. Devices that aid articulation, such as fulcra with short articulating pleural surfaces, the petaloid articulating facet and long articulating half rings, are concentrated in the anterior region. These features, and the large number of specimens preserved in various degrees of enrolment, suggest an enrolment procedure in which the rear part of the trunk, containing both the posterior thorax and the pygidium, rotated as a single unit without significant internal flexure. As these posterior trunk articulations were apparently not required to permit enrolment, concentrating flexure in the anterior may have presaged the caudalized condition seen in many derived trilobite groups that encapsulated, in which a larger proportion of the trunk segments were allocated to the mature pygidium, and therefore unable to articulate.     

Auditory ossicles from southwest Asian Mousterian sites

The present study describes and analyzes new Neandertal and early modern human auditory ossicles from the sites of Qafzeh and Amud in southwest Asia. Some methodological issues in the measurement of these bones are considered, and a set of standardized measurement protocols is proposed. Evidence of erosive pathological processes, most likely attributed to otitis media, is present on the ossicles of Qafzeh 12 and Amud 7 but none can be detected in the other Qafzeh specimens. Qafzeh 12 and 15 extend the known range of variation in the fossil H. sapiens sample in some metric variables, but morphologically, the new specimens do not differ in any meaningful way from living humans. In most metric dimensions, the Amud 7 incus falls within our modern human range of variation, but the more closed angle between the short and long processes stands out. Morphologically, all the Neandertal incudi described to date show a very straight long process. Several tentative hypotheses can be suggested regarding the evolution of the ear ossicles in the genus Homo. First, the degree of metric and morphological variation seems greater among the fossil H. sapiens sample than in Neandertals. Second, there is a real difference in the size of the malleus between Neandertals and fossil H. sapiens, with Neandertals showing larger values in most dimensions. Third, the wider malleus head implies a larger articular facet in the Neandertals, and this also appears to be reflected in the larger (taller) incus articular facet. Fourth, there is limited evidence for a potential temporal trend toward reduction of the long process within the Neandertal lineage. Fifth, a combination of features in the malleus, incus, and stapes may indicate a slightly different relative positioning of either the tip of the incus long process or stapes footplate within the tympanic cavity in the Neandertal lineage.     

Functional morphology of synostosial articulations in the crinoid column

The rarest articulation found in the crinoid column is the synostosis, in which adjacent articular facets are essentially planar. 'Synostoses' in the columns of post-Palaeozoic isocrinids are more correctly termed cryptosymplexies. comprising symplectial articulations which have become infilled by secondary calcite. Cryptosymplexial joints are totally inflexible and are the preferred sites of stem autotomy. Synostoses sensu stricto appear to have been limited to early Palaeozoic taxa, but this form of articulation was soon succeeded by the symplexy. Synostoses were probably commonest in meric columns which evolved from hohlwurzels and in which the main flexibility was along meric sutures, rather than between columnals. With the evolution of the holomeric columnal. a more flexible articulation between columnals was a functional necessity in order that the stem did not develop into a stiffened rod. The solution was the evolution of the symplexy. *** Crinoids, columnals. synostosis, functional morphology evolution.     

Localization of pN-type IIA procollagen on adult bovine vitreous collagen fibrils.

Type II procollagen is synthesized in long (type IIA) and short (type IIB) forms because of alternative splicing of mRNA; the long form containing an additional cysteine-rich domain in the amino-propeptide. An antiserum (IIA) that recognizes this domain was used for immunolocalization studies on adult bovine vitreous at light and electron microscopic levels and for Western blot analyses. The immunolocalization studies revealed labelling by the IIA antiserum of the vitreous collagen fibrils. This labelling was removed by prior extraction of the fibrils with 6 M guanidine hydrochloride (GuHCl) and the extract was shown to contain pN-type IIA procollagen. Adult vitreous collagen fibrils are coated with pN-type IIA procollagen, a finding with potential implications for vitreous collagen fibril structure and function.     

Multiple forms of DNA-dependent RNA polymerases in Xenopus laevis. Rapid purification and structural and immunological properties

DNA-dependent RNA polymerases I, II, and III (EC 2.7.7.6) were isolated from Xenopus laevis ovaries. The soluble enzymes were precipitated with polyethyleneimine and subjected to chromatography on heparin-Sepharose, DEAE-Sephadex, and phosphocellulose. RNA polymerase I was subjected to an additional chromatographic step on CM-Sephadex. The procedure required 40 h and produced purified RNA polymerase forms IA, IIA, and III in yields of 5 to 40%. The specific activities of RNA polymerases IIA and III (on native DNA) were comparable to those reported from other eukaryotic sources, whereas that of form IA was severalfold greater than the specific activities reported for other purified class I RNA polymerases. The complex subunit compositions of chromatographically purified RNA polymerases IA, IIA, and III were distinct when analyzed by polyacrylamide gradient gel electrophoresis under denaturing conditions, although all three classes contained polypeptides with Mr = 29,000, 23,000, and 19,000. Antibodies prepared against RNA polymerase III showed common antigenic determinants within the class I, II, and III enzymes. The sites responsible for the cross-reaction are located, at least in part, on the common 29,000-dalton polypeptide.     

Radial perforations in crinoid stems from the Silurian of Gotland

Radiating intracolumnal canals are a characteristic feature of large (diameter 10 mm or more) crinoid stems from the Silurian of Gotland. They are found in nodals as well as in internodals where the columnal height exceeds one millimetre. They were formed secondarily in the median and distal portions of crinoid stems with pseudocirriferous holdfasts. Intercolumnal canals are found in the distal parts of stems with true cirri regardless of the size of the stem. It is suggested that these canals played an important role in crinoid physiology. The crinoids are believed to have sustained a large proportion of their tissues through cutaneous digestion and uptake of dissolved substances from the surrounding sea water. The intra- and intercolumnal canals increased the surface of the axial canal in relation to volume. They provided a connection between the axial canal and the surrounding sea water, thus facilitating nutrient transport to the tissues.     

Effects of maturation and co-culture treatments on the developmental capacity of early bovine embryos.

A total of 901 cumulus-oocyte complexes (COCs) were collected from bovine ovaries obtained at a local abattoir. COCs randomly assigned to Treatment I (n = 451), were cultured in TCM-199 + 10% fetal bovine serum (FBS) and hormones, while oocytes in Treatment II (n = 450) were cultured in TCM-199 + 20% estrous cow serum (ECS). Assessment of maturation revealed that 91.3% (42/46) of oocytes in Treatment I had reached metaphase II of meiosis, which was greater (P less than 0.05) than the 73.3% (33/45) in Treatment II. Following in vitro fertilization, 203 oocytes from Treatment I were co-cultured on bovine granulosa cells (Treatment IA) while the remaining 202 oocytes were co-cultured on bovine oviductal cells (Treatment IB). Similarly, 203 oocytes from Treatment II were co-cultured on granulosa cells (Treatment IIA) or oviductal cells (Treatment IIB, n = 202). Co-culture was maintained for 8 days. The proportion of cleaved zygotes was higher (P less than 0.05) in Treatment IB (86.6%) compared to Treatments IA (78.8%), IIA (58.1%), and IIB (64.8%). The proportion of cleaved zygotes that progressed beyond the 16-cell stage was also greater (P less than 0.001) in Treatment IB (71.4%) compared to Treatments IA (50.0%), IIA (35.4%) and IIB (55.8%). Treatment IB also produced the highest proportion of blastocysts (P less than 0.0001) (41.1%) versus 24.6% (IA), 11.3% (IIA) and 18.3% (IIB). The proportion of day 6 morulae that progressed to form day 8 blastocysts was similar for both co-culture treatments (IA, 70.1%; IB 70.2%; IIA, 51.5%; IIB 50.8%) and varied only between in vitro maturation groups.(ABSTRACT TRUNCATED AT 250 WORDS)     

Early stalked stages in ontogeny of the living isocrinid sea lily Metacrinus rotundus

The early stalked stages of an isocrinid sea lily, Metacrinus rotundus, were examined up to the early pentacrinoid stage. Larvae induced to settle on bivalve shells and cultured in the laboratory developed into late cystideans. Three‐dimensional (3D) images reconstructed from very early to middle cystideans indicated that 15 radial podia composed of five triplets form synchronously from the crescent‐shaped hydrocoel. The orientation of the hydrocoel indicated that the settled postlarvae lean posteriorly. In very early cystideans, the orals, radials, basals and infrabasals, with five plates each in the crown, about five columnals in the stalk, and five terminal stem plates in the attachment disc, had already formed. In mid‐cystideans, an anal plate appeared in the crown. Late cystideans cultured in the field developed into pentacrinoids about 5 months after settlement. These pentacrinoids shared many crown structures with adult sea lilies. On the other hand, many features of the stalk differed from those in adult isocrinids, while sharing many characteristics with the stalk of feather star pentacrinoids, including disc‐like proximal columnals, high and slender median columnals, synarthrial articulations developmentally derived from the symplexial articulations, limited formation of cirri only in the proximal columnal(s), and an attachment disc. On the basis of these findings, phylogenetic relationships among extant crinoid orders are discussed.     

The effects of endurance, strength, and power training on muscle fiber type shifting

Muscle fibers are generally fractionated into type I, IIA, and IIX fibers. Type I fibers specialize in long duration contractile activities and are found in abundance in elite endurance athletes. Conversely type IIA and IIX fibers facilitate short-duration anaerobic activities and are proportionally higher in elite strength and power athletes. A central area of interest concerns the capacity of training to increase or decrease fiber types to enhance high-performance activities. Although interconversions between type IIA and IIX are well recognized in the literature, there are conflicting studies regarding the capacity of type I and II fibers to interconvert. Therefore, the purpose of this article is to analyze the effects of various forms of exercise on type I and type II interconversions. Possible variables that may increase type II fibers and decrease type I fibers are discussed, and these include high velocity isokinetic contractions; ballistic movements such as bench press throws and sprints. Conversely, a shift from type II to type I fibers may occur under longer duration, higher volume endurance type events. Special care is taken to provide practical applications for both the scientist and the athlete.     

New deep-sea Tardigrada (Arthrotardigrada,Halechiniscidae) from a manganese nodule area of the eastern South Pacific*

Three new Tardigrada species are described from a manganese nodule area of thc abyssal castern South Pacific. Moebjergarctus mangunis gen. et sp.n. is characterized by its segmcntcd ccphalic cirri, club-shaped and forward bent primary clavae, spherical secondary clavae, spines on legs I, 11, 111, small clavoid papillae on legs IV, long cirri E, and corkscrew-shaped digits with simple claws. Angursa capsula sp.n. is distinguished by the presence of secondary and tertiary clavac, occurring as elevated cuticular areas, club-shaped primary clavae, short lateral cirri, short median cirrus, spines on legs I and hcmisphcrical, capsulc-shaped papillae on legs IV. Angursa lingua sp.n. is characterized by the presence of secondary and tertiary clavae, occurring as elevated cuticular areas, balloon-shaped primary clavae, long lateral cirri, long median cirrus, spines on legs I, clavoid papillae on legs IV and weakly broadened distal parts of cirri E, resulting in tongue-shaped swellings. A simple key to the species of Angursa is presented.     

Structure of the topoisomerase VI-B subunit: implications for type II topoisomerase mechanism and evolution

Type IIA and type IIB topoisomerases each possess the ability to pass one DNA duplex through another in an ATP-dependent manner. The role of ATP in the strand passage reaction is poorly understood, particularly for the type IIB (topoisomerase VI) family. We have solved the structure of the ATP-binding subunit of topoisomerase VI (topoVI-B) in two states: an unliganded monomer and a nucleotide-bound dimer. We find that topoVI-B is highly structurally homologous to the entire 40-43 kDa ATPase region of type IIA topoisomerases and MutL proteins. Nucleotide binding to topoVI-B leads to dimerization of the protein and causes dramatic conformational changes within each protomer. Our data demonstrate that type IIA and type IIB topoisomerases have descended from a common ancestor and reveal how ATP turnover generates structural signals in the reactions of both type II topoisomerase families. When combined with the structure of the A subunit to create a picture of the intact topoisomerase VI holoenzyme, the ATP-driven motions of topoVI-B reveal a simple mechanism for strand passage by the type IIB topoisomerases.     

Locomotion in ground beetles (Coleoptera carabidae): An interpretation of leg structure in functional terms

Recordings of maximum running speeds and maximum horizontal pulling (= pushing) forces have been obtained for 72 species of cursorial and fossorial ground beetles (Carabidae: Coleoptera) belonging to 19 tribes and 12 supertribes. Fore leg, pro- and meso-femoral and tibial and mid leg measurements have also been made and all these parameters have been correlated with body lengths. It was found that those species (mainly Carabinae group I, i.e. Nebriini, Notiophilini, Loricerini, Elaphrini, Cicindelini) with relatively long, slender pro-and mesofemora, long pro - and mesotibiae and small meso-coxal articulations were faster runners (i.e. sprinters) but weaker horizontal pushers. In contrast, species (mainly Carabinae group II, i.e. Broscini, Trechini, Pogonini, Bembidiini, Patrobini, Pterostichini, Zabrini, Callistini, Oodini, Licinini, Harpalini) with relatively short, broad pro-femora, short (slender) mesofemora, short pro– and mesotibiae, and larger meso-coxal articulations were stronger horizontal pushers but were slower runners. Carabinae group III (Scaritini), however, which have very short, narrow pro- and mesofemora, very short pro- and mesotibiae, and large meso-coxal articulations were found to be very strong horizontal pushers but very slow (relatively) runners.
The Carabini (including Cychrini), however, resemble Carabinae group II in their running and pushing abilities although their legs are structurally similar to those of Carabinae group I (i.e. relatively long and slender with small meso–coxal articulations). In fact, species of Carabini are fast walkers, their prey is generally slow moving (i.e. slugs, snails and caterpillars) and they hunt in restrictive habitats such as weed patches, meadows or woodland grass which produce a considerable amount of environmental resistance. Most Carabini have a heavy, powerful body which seems to be well adapted to overcoming this resistance.     

Isolation and characterization of subunits from the predominant form of Dolichos biflorus lectin.

The subunits of the two molecular forms (A and B) of the Dolichos biflorus lectin were isolated by ion-exchange chromatography on DEAE-cellulose in 8.0 M urea. Subunits IA and IIA which comprise the predominant molecular form A of the lectin were found to have molecular weights of 27,700 and 27,300, respectively, as determined by sedimentation equilibrium studies in 8.0 M urea. These subunits have similar amino acid compositions and each have alanine at their amino-terminal ends. Comparison of the IA and IIA subunits by immunodiffusion against antisera to the seed extract as well as to subunits IA and IIA showed no antigenic differences between the two subunits. Carboxyl terminal analyses of subunits IA and IIA with carboxypeptidase A produced an essentially simultaneous release of both leucine and valine residues from subunit IA; no detectable amino acids were released from subunit IIA under identical conditions. The data suggest that the molecular form A of the lectin (molecular weight 113,000, Carter and Etzler, 1975) consists of four subunits with a possible stoichiometry of IA2IIA2. Other possible arrangements of the subunits are discussed.     

Growth patterns and evolutionary trends of Devonian crinoid columns

The general morphology of the crinoid column is briefly reviewed; growth patterns deduced from the study of stem fragments and dissociated columnals are analysed in the two commonest groups occurring in the Devonian strata of France: the Cyclici and the Pentameri. Problems concerning the introduction of new columnals beneath the calyx and the differentiation of cycles in the proximal part of heteromorphic stems are set. Evolutionary trends affecting various morphological elements include size increase, ornamentation development, cirri insertion and distribution, epifacet regression and formation of composite and secondary holdfasts. At present, these trends appear to be limited to small systematic units but proxistelisation, defined as the downward extension of proxistele characters to the other stem regions, seems to be wide-spread in the Pentameri. The difficulty in determining the evolutionary process (neoteny, progenesis…) due to the lack of information on early ontogenetic stages is emphasized.     

Alternative Male Spawning Tactics and Acoustic Signals in the Plainfin Midshipman Fish Porichthys notatus Girard (Teleostei,Batrachoididae)

The plainfin midshipman Porichthys notatus has two male reproductive morphs, ‘Type I’ and ‘Type II’, which are distinguishable by their physical traits alone. Type I males are eight times larger in body mass than Type II males and have a six-fold larger relative sonic (vocal) muscle mass than Type II males. In contrast, the testicles of Type II males are seven times larger than those of Type I males. This study demonstrates morph-specific patterns of reproduction, including acoustic signals, for Type I and II males. Field censuses of nests showed that only Type 1 males maintained nests. Type II males and females transiently appeared in these nests in association with each other. Infra-red video and hydrophone recordings in aquaria showed that Type I males maintained nests and readily vocalized. Long-duration ‘hums’ and sequences of short-duration ‘grunts’ were produced during advertisement and agonistic contexts, respectively. Humming Type I males attracted females to their nests, pair-spawned, and then guarded egg clutches alone. By contrast, Type II males neither acoustically courted females nor maintained available nest sites, but rather ‘sneak-’ or ‘satellite-spawned’ at the nests of Type I males. Type II males infrequently produced low amplitude, short duration grunts that were similar in spectral, temporal and amplitude characteristics to the grunts of females. Type II males appear to be obligate sexual parasites of the nest-building, mate-calling, and egg-guarding Type I males. The dimorphic body and vocal muscle traits of the two male morphs in the plainfin midshipman are thus paralleled by a divergence in their reproductive tactics and the properties of their acoustic signals.     

Electrophoretic microheterogeneity and subunit composition of the 13S coupling factors of oxidative and photosynthetic phosphorylation.

Two electrophoretically distinguishable species of the 13S coupling factor of oxidative phosphorylation from Alcaligenes faecalis are detectable by standard polyacrylamide gel electrophoresis in the absence of urea, detergents, or any other protein-denaturing reagents. The slower species (type IA) can be converted into the faster species (type IB) by treatment with ATP, and the fast form converts into the slow form when aged at 4 degrees. The enzyme undergoes these conversions both when it is free in solution and when it is membrane bound. The ATP analog adenylyl imidodiphosphate (AMP-PNP) gives the conversion without being hydrolyzed and without causing any apparent change in the mass of the protein, which suggests that the conversion may be a ligand-induced conformational change. Types IA and IB can convert into three other electrophoretically distinguishable species (types IIA, IIB, and III) if the purification procedure involves chromatography on a DEAE-Sephadex column equilibrated in phosphate buffer. These conversions can be prevented if the column is eluted in morpholinoethanesulfonic acid (Mes) buffer and KCl. Type IIA is convertible into type IIB by ATP treatment. Types IA and IB will also convert into types IIA and IIB and finally into type III when aged for extended periods of time at 4 degrees, without a detectable change in mass. Coupling factor activity is lost when type I enzyme converts into type II enzyme, as is the ability of the enzyme to bind to the membrane. However, ATPase activity does not change significantly. The mitochondrial 13S coupling factor shows up to three electrophoretically distinguishable species. The use of phosphate buffer during DEAE-Sephadex chromatography gives conversion of slower species into faster species. ATP treatment does not give interconversions, and aging at 4 degrees gives only a slow dissociation of the enzyme into subunits. The chloroplast 13S coupling factor also shows up to three electrophoretic species. Incubation with ATP does not give interconversions, but a temperature-dependent conversion of the major species into a faster species occurs upon aging. The subunit composition of the three 13S enzymes is very similar by polyacrylamide gel electrophoresis in sodium dodecyl sulfate, the major difference being in the number of classes of small polypeptides.