The role of colony morphology and substratum inclination in the success of Millepora alcicornis on shallow coral reefs

 Millepora species are conspicuous members of shallow coral reefs where they occupy a variety of substrata and produce morphologically complex skeletons. This study focuses on the roles of growth on vertical and horizontal surfaces and the production of encrusting bases and branches (a “sheet-tree” morphology) for the success of the Millepora alcicornis on coral reefs. The effects of inclination were investigated by comparing the size and growth rates of M. alcicornis on vertical and horizontal surfaces at 3–5 m depth, in St. John, US Virgin Islands. The consequences of morphological complexity were investigated by comparing polyp density, chlorophyll content and biomass between encrusting bases and branches; the role of branches in asexual reproduction was also quantified. Colonies on vertical surfaces had larger encrusting bases, longer perimeters and lower densities of branches compared to those on horizontal surfaces. Growth rates also varied significantly between surfaces, largely because colonies on horizontal surfaces shrank in area while those on vertical surfaces increased in area, albeit slowly. Branches were not specialized in comparison to encrusting bases in terms of the density of dactylozooids and gastrozooids, chlorophyll content and biomass, but they were effective asexual propagules. During one storm, 79% of the branches were removed from colonies of M. alcicornis, and 4% attached to the substratum to produce new colonies at a density of ≈0.5 colonies.m^-2. Anecdotal observations suggest that such storms rarely damaged encrusting bases on vertical surfaces, but often destroyed those on horizontal surfaces. Thus, the encrusting bases on vertical surfaces are likely to be large because of greater age rather than faster growth, while those on horizontal surfaces are likely to be small because they are relatively young and short lived. These findings suggest that the success of M. alcicornis is a result, in part, of the beneficial consequences of their “sheet-tree” morphology, that supports: (a) slow growth and resistance to wave damage of encrusting bases on vertical surfaces, and (b) the use of branches as asexual propagules. Accepted: 24 November 1998     

Hidden diversity and host specificity in cycliophorans: a phylogeographic analysis along the North Atlantic and Mediterranean Sea

In order to elucidate the evolutionary history and the population structure of the members of the phylum Cycliophora, which live commensally on three species of lobsters, we studied sequence variation in the mitochondrial gene cyctochrome c oxidase subunit I. Overall 242 sequences from 16 locations on both coasts of the North Atlantic, including the North Sea and the Mediterranean, were analysed, revealing 28 haplotypes, with a maximum sequence divergence of 16.6%. Total genetic diversity was high (h = 0.8322, pi = 0.0898), as it was for the commensals on Homarus americanus (17 haplotypes, h = 0.7506, pi = 0.0504). However, it was low for commensals on Nephrops norvegicus (6 haplotypes, h = 0.3899, pi = 0.0035), and intermediate for cycliophorans on Homarus gammarus (5 haplotypes, h = 0.3020, pi = 0.0140). Although two of the host lobsters co-inhabit the coastal waters of Europe, a strong genetic structure (78.45% of the observed genetic variation) was detected among populations on all host species, indicating the existence of a reproductively isolated species on each lobster. In addition, genetic structure over long distances exists among populations on each host species. Such patterns can be explained by the limited dispersal ability of the cycliophoran chordoid larva. Demographic and phylogenetic analyses suggest old and possibly cryptic populations present on H. americanus and H. gammarus, while the latter may have experienced recent bottlenecks, perhaps during Pleistocene glaciations. Populations on N. norvegicus appear to be of recent origin.     

Replenishment of fish populations in the enclosed lagoon of Taiaro Atoll: (Tuamotu Archipelago, French Polynesia) evidence from eggs and larvae

 Taiaro Atoll Lagoon is normally isolated from the ocean, but at least 125 marine fish species of 31 families are present there. We sampled fish larvae in Taiaro Lagoon and the nearby ocean in February 1994 with plankton net, neuston net and light trap to investigate which taxa were completing their life cycles in the lagoon. Concentrations of fish eggs and larvae were very high in the lagoon indicating intense spawning, but larvae of only 18 taxa of 10 families were present. Only six, a callionymid, gobiids, a hemiramphid, a microdesmid, and two pomacentrids, were present across a full range of pelagic sizes, and were clearly completing their pelagic stage in the lagoon. Four other taxa, an apogonid, two labrids and a scarid, were common, but the largest individuals were small (<5 mm) postflexion larvae. These may have been completing their pelagic stage in the lagoon. The remaining lagoonal larvae (eight taxa) were rare and at the preflexion stage, so we could only conclude that they hatched from eggs spawned in the lagoon. Nineteen taxa of 15 families found as adults in the lagoon were present outside the lagoon as larvae, but not inside, suggesting that they may not normally complete their life cycles in the lagoon. Horizontal distributions of larvae in the lagoon are apparently due to the interaction of larval vertical distribution behaviour with a wind-driven countercurrent system. Accepted: 16 October 1996     

Adaptive variation in energy acquisition and allocation among latitudinal populations of the Atlantic silverside

Understanding the evolution of growth rate requires knowledge of the physiology of growth. This study explored the physiological basis of countergradient variation (CnGV) in somatic growth across latitudinal populations of the Atlantic silverside, Menidia menidia. Energetics of northern (Nova Scotia, Canada) and southern (South Carolina, USA) genotypes were compared across resource levels, temperatures, and fish sizes to identify trade-offs to rapid growth. Offered unlimited resources, genotypes differed in both energy acquisition and allocation. Food consumption, growth, and efficiency of northern genotypes were consistently higher than in southern genotypes, across temperatures and body sizes. Feeding metabolism (specific dynamic action; SDA) was proportional to meal size, differing between genotypes to the extent that food consumption differed. Given limited resources, northern and southern genotypes displayed similar growth, efficiency, routine activity, and SDA across temperatures and fish sizes. Routine metabolism was equal at 17°C and 22°C, yet was significantly higher in northern fish at 28°C. Growth rates in M. menidia do not appear to trade off across environments or body sizes, i.e., at no temperature, ration, or size do southern fish outgrow northern conspecifics. Nor does submaximal growth result from increased costs of maintenance, tissue synthesis, or routine activity. Based on our findings, we propose that CnGV consumption and growth in M. menidia likely result from trade-offs with other energetic components, namely sustained and burst swimming. Received: 26 January 1999 / Accepted: 14 September 1999     

Vegetation dynamics and arbuscular mycorrhiza in old-field successions of the western Italian Alps

The relationships between vegetational and arbuscular mycorrhizal (AM) dynamics were investigated in an old-field succession in the western Italian Alps. Vegetation and AM colonization were determined in eight sites corresponding to different stages of successional dynamics: (a) a field under cultivation; (b) fields abandoned for 1, 2 and 3 years supporting ruderal vegetation; (c) grasslands; (d) shrublands; (e) early wood communities; (f) mature woods. AM colonization was evaluated on the roots of representative plants from each community. The data thus obtained, together with those from the literature, were then used to calculate the plant community mycorrhizal index. This index provides qualitative and quantitative information concerning the relative percentage of non-mycorrhizal, AM and ectomycorrhizal plant cover in an entire plant community. The AM inoculum potential of each site was also determined using a bait approach. Farming disturbance temporarily reduced soil infectivity. Non-mycorrhizal ruderal annuals dominated after 1 year abandonment and covered 90–100 % of the surface. After 2 or 3 years, a rapid change to AM-colonized competitive and competitive-ruderal perennials was observed. The increase in AM inoculum was associated with an increase in floristic richness and equitability in the community. AM were also dominant in the shrublands and early wood communities, but gave way to ectomycorrhizal species in the mature woods. The observed AM inoculum potentials are in accordance with these findings. The results of this study further emphasize the need to take into account AM infection in plans for the renaturalization of degraded areas. Accepted: 16 June 1999     

Exploring the nature of ecological specialization in a coral reef fish community: morphology,diet and foraging microhabitat use

Patterns of ecological specialization offer invaluable information about ecosystems. Yet, specialization is rarely quantified across several ecological niche axes and variables beyond the link between morphological and dietary specialization have received little attention. Here, we provide a quantitative evaluation of ecological specialization in a coral reef fish assemblage (f. Acanthuridae) along one fundamental and two realized niche axes. Specifically, we examined ecological specialization in 10 surgeonfish species with regards to morphology and two realized niche axes associated with diet and foraging microhabitat utilization using a recently developed multidimensional framework. We then investigated the potential relationships between morphological and behavioural specialization. These relationships differed markedly from the traditional ecomorphological paradigm. While morphological specialization showed no relationship with dietary specialization, it exhibited a strong relationship with foraging microhabitat specialization. However, this relationship was inverted: species with specialized morphologies were microhabitat generalists, whereas generalized morphotypes were microhabitat specialists. Interestingly, this mirrors relationships found in plant–pollinator communities and may also be applicable to other ecosystems, highlighting the potential importance of including niche axes beyond dietary specialization into ecomorphological frameworks. On coral reefs, it appears that morphotypes commonly perceived as most generalized may, in fact, be specialized in exploiting flat and easily accessible microhabitats.     

Priority effects, taxonomic resolution, and the prediction of variable patterns of colonisation of algae in littoral rock pools

This study focuses on succession of macroalgae in littoral rock pools on the west coast of Italy. Previous studies in this system indicated that either canopy algae or turf-forming algae may dominate late in succession. Priority effects and non-hierarchical interactions have been proposed as possible explanations for these patterns. From previous knowledge on the timing of reproduction and recruitment of the two groups of algae and their interactions, I predicted that: (1) canopy algae would dominate patches of substratum cleared during their main period of recruitment (between April and July); (2) the turf-forming algae, although initially present, would be replaced by canopies in these patches; (3) turf-forming algae would characterise both the early stages of colonisation and the mature assemblage in patches cleared before or after the main period of recruitment of canopy algae, and (4) succession would be more consistent in space (i.e. canalised) in the presence of canopy algae than when the turf-forming plants achieve dominance. These predictions were tested in a multifactorial experiment where patches of substratum were cleared in three different periods (before, during and after the main period of recruitment of canopy algae), on three dates within each period and in two replicate pools in each date. Univariate and multivariate analyses indicated that variability at early stages of colonisation dictated much of the subsequent dynamics in this system. Predictions 1–3 were supported by the results, but only at a gross level of taxonomic resolution. Patterns of colonisation of individual species of turf-forming algae were unpredictable due to large small-scale spatial and temporal variation in abundance. Prediction 4 was not supported by the results. This study indicated that knowledge of the life-histories and ecology of individual populations is crucial to increase the accuracy and precision of ecological models that attempt to predict succession in variable systems. Received: 4 May 1999 / Accepted: 8 November 1999     

Inoculation and nitrate alter phytohormone levels in soybean roots: differences between a supernodulating mutant and the wild type

 The levels of different cytokinins, indole-3-acetic acid (IAA) and abscisic acid (ABA) in roots of Glycine max [L.] Merr. cv. Bragg and its supernodulating mutant nts382 were compared for the first time. Forty-eight hours after inoculation with Bradyrhizobium, quantitative and qualitative differences were found in the root's endogenous hormone status between cultivar Bragg and the mutant nts382. The six quantified cytokinins, ranking similarly in each genotype, were present at higher concentrations (30–196% on average for isopentenyl adenosine and dihydrozeatin riboside, respectively) in mutant roots. By contrast, the ABA content was 2-fold higher in Bragg, while the basal levels of IAA [0.53 μmol (g DW)⁻¹, on average] were similar in both genotypes. In 1 mM NO₃ ⁻-fed Bragg roots 48 h post-inoculation, IAA, ABA and the cytokinins isopentenyl adenine, and isopentenyl adenosine quantitatively increased with respect to uninoculated controls. However, only the two cytokinins increased in the mutant. High NO₃ ⁻ (8 mM) markedly reduced root auxin concentration, and neither genotypic differences nor the inoculation-induced increase in auxin concentration in Bragg was observed under these conditions. Cytokinins and ABA, on the other hand, were little affected by 8 mM NO₃ ⁻. Root IAA/cytokinin and ABA/cytokinin ratios were always higher in Bragg relative to the mutant, and responded to inoculation (mainly in Bragg) and nitrate (both genotypes). The overall results are consistent with the auxin-burst-control hypothesis for the explanation of autoregulation and supernodulation in soybean. However, they are still inconclusive with respect to the inhibitory effect of NO₃ ⁻. Received: 16 April 1999 / Accepted: 13 December 1999     

Effects of Habitat Connectivity on the Abundance and Species Richness of Coral Reef Fishes: Comparison of an Experimental Habitat Established at a Rocky Reef Flat and at a Sandy Sea Bottom

Coral reef fish assemblages are widely recognized for the coexistence of numerous species, which are likely governed by both coral diversity and substratum complexity. However, since coral reefs provide diverse habitats due to their physical structure and different spatial arrangements of coral, findings obtained from an isolated habitat cannot necessarily be applied to fish assemblages in other habitats (e.g. continuous habitats). The aim of this study, therefore, was to determine by a field experiment whether habitat connectivity (spatial arrangement of coral colonies) affects abundance and species richness of fishes in an Okinawan coral reef. The experiment consisted of transplanted branching coral colonies at a 4m×8m quadrat at both a rocky reef flat and sandy sea bottom. Generally, the abundance of fishes was greater at the sandy sea bottom, especially for three species of pomacentrids, one species of labrids, one species of chaetodontids and two species of apogonids. Species–area curves showed that the species richness of fishes was significantly greater in the quadrat at the sandy sea bottom at 3, 6 and 9 months after the start of the experiment. The rate of increase in abundance of fishes per area was significantly greater in the quadrat at the sandy sea bottom over the study period. The results of rarefaction analyses showed that the rate of increase in species richness per abundance was significantly higher in the quadrat at the sandy sea bottom in the juvenile settlement period, indicating that the magnitude of dominance by particular species was greater at the sandy sea bottom habitat. Our findings suggest that habitat connectivity affects the abundance and species richness of coral reef fishes, i.e. the isolated habitat was significantly more attractive for fishes than was the continuous habitat. Our findings also suggest that the main ecological factors responsible for organization of fish assemblage at a continuous habitat and at an isolated habitat are different.     

Lateral specificity in resistance training: the effect of bilateral and unilateral training

 Maximal voluntary strength of simultaneous bilateral exertion has been shown to be small compared to the sum of the unilateral exertions. Three experiments were conducted to determine the effects of bilateral and unilateral resistance training on this bilateral deficit and to compare these in hands, arms, and legs. In each experiment, the subjects were divided into three groups: unilateral training group, bilateral training group, and control group. The subjects of the training group performed maximal isometric handgrip training in experiment I, and maximal isokinetic arm and leg extension training in experiments II and III. In each experiment, the subjects of the training group continued one of these resistance training exercises three times a week, for 6 weeks. The increase in handgrip strength of the bilateral training group produced in the bilateral condition [5.1 (SEM 2.4)%, after 3 weeks, 6.4 (SEM 2.3) %, after 6 weeks] was significantly greater compared with the control group [−1.1 (SEM 1.0) %, after 3 weeks, −1.5 (SEM 1.1) %, after 6 weeks. The increase in leg extension power of the bilateral training group produced in the bilateral condition [16.1 (SEM 9.6) %, after 3 weeks, 24.1 (SEM 7.4) %, after 6 weeks] was significantly greater compared with the unilateral training group [−5.0 (SEM 3.4) %, after 3 weeks, −3.4 (SEM 4.2) %, after 6 weeks] and the control group [−4.3 (SEM 2.5) %, after 3 weeks, 1.5 (SEM 5.5) %, after 6 weeks]. The increase in handgrip strength of the unilateral training group produced in the unilateral condition [7.3 (SEM 1.7) %, after 3 weeks] was significantly greater compared with the control group [−0.9 (SEM 1.8) %, after 3 weeks]. The increase in arm extension power of the unilateral training group produced in the unilateral condition [7.2 (SEM 1.8) %, after 6 weeks] was significantly greater compared with the bilateral training group [−3.0 (SEM 2.3) %, after 6 weeks] and the control group [−2.1 (SEM 2.6) %, after 6 weeks]. Bilateral indexes (BI) were shifted in a positive direction by bilateral training and tended to shift in a negative direction by unilateral training. With regard to the magnitude of change in BI, there were no significant differences among handgrip, arm extension, and leg extension training. It is suggested that there is lateral specificity in resistance training and that there is no difference among body parts in the modification of bilateral deficit by lateral training. Accepted: 27 August 1996     

Limb development in a primitive crustacean,Triops longicaudatus: subdivision of the early limb bud gives rise to multibranched limbs

 Recent advances in developmental genetics of Drosophila have uncovered some of the key molecules involved in the positioning and outgrowth of the leg primordia. Although expression patterns of these molecules have been analyzed in several arthropod species, broad comparisons of mechanisms of limb development among arthropods remain somewhat speculative since no detailed studies of limb development exist for crustaceans, the postulated sister group of insects. As a basis for such comparisons, we analysed limb development in a primitive branchiopod crustacean, Triops longicaudatus. Adults have a series of similar limbs with eight branches or lobes that project from the main shaft. Phalloidin staining of developing limbs buds shows the distal epithelial ridge of the early limb bud exhibits eight folds that extend in a dorsal ventral (D/V) arc across the body. These initial folds subsequently form the eight lobes of the adult limb. This study demonstrates that, in a primitive crustacean, branched limbs do not arise via sequential splitting. Current models of limb development based on Drosophila do not provide a mechanism for establishing eight branches along the D/V axis of a segment. Although the events that position limbs on a body segment appear to be conserved between insects and crustaceans, mechanisms of limb branching may not. Received: 28 February 1996/Accepted: 24 June 1996     

Spatial scale and the detection of density dependence in spruce budworm outbreaks in eastern North America

Using two tests for direct density dependence and standard techniques of time series analysis, we identified density dependence in defoliation time series of the spruce budworm across its outbreak range in eastern North America over the years 1945–1988. We carried out analyses for the entire region and for grid cells of defoliation maps at five spatial scales created by aggregating the smallest grid cells. The rate of detection of direct density dependence, as assessed by two previously published methods, decreased with increasing spatial scale. Using both methods, density dependence was detected more frequently at the periphery of the outbreak range, where defoliation rate was lower. This result suggested that density-dependent regulation may be stronger in those areas. The first order autoregressive process was the basic model for defoliation dynamics overall and the most common model across spatial scales. Second-order processes were encountered much less frequently, and those commonly identified as resulting from delayed density dependence generally occurred across spatial scales at a rate expected by chance alone. Our results were similar to those of other published studies, which have found the detection of density dependence to decrease at larger spatial scales. The results also reinforced the importance of considering spatial scale when diagnosing population processes using time series of abundance for single species. Received: 26 December 1999 / Accepted: 17 March 2000     

Marine molluscs and fish as biomarkers of pollution stress in littoral regions of the Red Sea, Mediterranean Sea and North Sea

The intensive development of industry and urban structures along the seashores of the world, as well as the immense increase in marine transportation and other activities, has resulted in the deposition of thousands of new chemicals and organic compounds, endangering the existence of organisms and ecosystems. The conventional single biomarker methods used in ecological assessment studies cannot provide an adequate base for environmental health assessment, management and sustainability planning. The present study uses a set of novel biochemical, physiological, cytogenetic and morphological methods to characterize the state of health of selected molluscs and fish along the shores of the German North Sea, as well as the Israeli Mediterranean and Red Sea. The methods include measurement of activity of multixenobiotic resistance-mediated transporter (MXRtr) and the system of active transport of organic anions (SATOA) as indicators of antixenobiotic defence; glutathione S-transferase (GST) activity as an indicator of biotransformation of xenobiotics; DNA unwinding as a marker of genotoxicity; micronucleus test for clastogenicity; levels of phagocytosis for immunotoxicity; cholinesterase (ChE) activity and level of catecholamines as indicators of neurotoxicity; permeability of external epithelia to anionic hydrophilic probe, intralysosomal accumulation of cationic amphiphilic probe and activity of non-specific esterases as indicators of cell/tissue viability. Complete histopathological examination was used for diagnostics of environmental pathology. The obtained data show that the activity of the defensive pumps, MXRtr and SATOA in the studied organisms was significantly higher in the surface epithelia of molluscs from a polluted site than that of the same species from control, unpolluted stations, providing clear evidence of response to stress. Enhanced frequency of DNA lesions (alkaline and acidic DNA unwinding) and micronucleus-containing cells was significantly higher in samples from polluted sites in comparison to those from the clean sites that exhibited genotoxic and clastogenic activity of the pollutants. In all the studied molluscs a negative correlation was found between the MXRtr levels of activity and the frequency of micronucleus-containing hemocytes. The expression of this was in accordance with the level of pollution. The complete histopathological examination demonstrates significantly higher frequencies of pathological alterations in organs of animals from polluted sites. A strong negative correlation was found between the frequency of these alterations and MXRtr activity in the same specimens. In addition to these parameters, a decrease in the viability was noted in molluscs from the polluted sites, but ChE activities remained similar at most sites. The methods applied in our study unmasked numerous early cryptic responses and negative alterations of health in populations of marine biota sampled from the polluted sites. This demonstrates that genotoxic, clastogenic and pathogenic xenobiotics are present and act in the studied sites and this knowledge can provide a reliable base for consideration for sustainable development. Received: 2 March 1999 / Received in revised form: 2 August 1999 / Accepted: 3 August 1999     

Surface mesoderm in Xenopus: a revision of the stage 10 fate map

 We have used two complementary cell labeling techniques to investigate dorsal mesoderm formation in Xenopus laevis and Hymenochirus boettgeri. Epithelial grafts from fluorescently labeled donors into unlabeled hosts demonstrate that in Xenopus, as previously shown for Hymenochirus, superficial cells of the dorsal marginal zone have the ability to invade the notochord and somite and participate in their normal morphogenesis, in a stage-specific and region-specific manner. A new method for superficial fate mapping using cell surface biotinylation confirms this result for Hymenochirus and demonstrates that in Xenopus as well, even in normal development in the absence of surgical disruption, notochord and the most posterior somitic mesoderm originate partly in the superficial epithelial layer. This finding is contrary to the widespread belief that Xenopus mesoderm originates solely in the deep mesenchymal layer. In Xenopus (but not in Hymenochirus), the amount of superficial contribution to mesoderm varies, such that in some spawnings it appears not to be present, while in others it is evident in all or most embryos. Received: 13 May 1997 / Accepted: 17 July 1997     

Maternal factors and the evolution of developmental mode: Evolution of oogenesis in Heliocidaris erythrogramma

 Evolutionary change in developmental mode in sea urchins is closely tied to an increase in maternal provisioning. We examined the oogenic modifications involved in production of a large egg by comparison of oogenesis in congeneric sea urchins with markedly different sized oocytes and divergent modes of development. Heliocidaris tuberculata has small eggs (95 μm diameter) and the ancestral mode of development through feeding larvae, whereas H. erythrogramma has large eggs (430 μm diameter) and highly modified non-feeding lecithotrophic larvae. Production of a large egg in H. erythrogramma involved both conserved and divergent mechanisms. The pattern and level of vitellogenin gene expression is similar in the two species. Vitellogenin processing is also similar with the gonads of both species incorporating yolk protein from coelomic and hemal stores into nutritive cells with subsequent transfer of this protein into yolk granules in the developing vitellogenic oocyte. Immunocytology of the eggs of both Heliocidaris species indicates they incorporate similar levels of yolk protein. However, H. erythrogramma has evolved a highly divergent second phase of oogenesis characterised by massive deposition of non-vitellogenic material including additional maternal protein and lipid. Maternal provisioning in H. erythrogramma exhibits recapitulation of the ancestral vitellogenic program followed by a novel oogenic phase with hypertrophy of the lipogenic program being a major contributor to the increase in egg size. Received: 12 August 1998 / Accepted: 25 November 1998     

Single-stranded DNA in the genetic transformation of wheat (Triticum aestivum L.): transformation frequency and integration pattern

Two non-linked marker genes (gus and bar) were co-introduced by microprojectile bombardment into wheat cells. Four different DNA structures were compared with respect to ability to integrate into the wheat genome: circular or linear (l) DNA as a single- or double-stranded plasmid (ss and ds, respectively). In eight independent experiments, linearized DNA integrated in the ds or ss form with a high efficiency of up to 14% for l-ssDNA. Molecular analyses by Southern blotting showed that all DNA forms gave a similar complicated integration pattern of the bar gene. Received: 20 July 1998 / Accepted: 30 January 1999     

Light-harvesting complex II pigments and proteins in association with Cbr, a homolog of higher-plant early light-inducible proteins in the unicellular green alga Dunaliella

 Like higher plants, unicellular green algae of the genus Dunaliella respond to light stress by enhanced de-epoxidation of violaxanthin and accumulation of Cbr, a protein homologous to early light-inducible proteins (Elips) in plants. Earlier studies indicated that Cbr was associated with the light-harvesting complex of photosystem II (LHCII) and suggested it acted as a zeaxanthin-binding protein and fulfilled a photo-protective function (Levy et al. 1993, J. Biol. Chem. 268: 20892–20896). To characterize the protein-pigment subcomplexes containing Cbr in greater detail than attained so far, thylakoid membranes from Dunaliella salina grown in high light or normal light were solubilized with dodecyl maltoside and fractionated by isoelectric-focusing. Analysis of the resolved LHCII subcomplexes indicated preferred associations among the four LHCIIb polypeptides and between them and Cbr: subcomplexes including Cbr contained one or two of the more acidic of the four LHCIIb polypeptides as well as large amounts of lutein and zeaxanthin relative to chlorophyll a/b. After sucrose gradient centrifugation, Cbr free of LHCIIb polypeptides was detected together with released pigments; this Cbr possibly originated in subcomplexes dissociated in the course of the analysis. These results agree with the conclusion that Cbr is part of the network of LHCIIb protein-pigment complexes and suggest that the role played by Cbr involves the organization and/or stabilization of assemblies highly enriched in zeaxanthin and lutein. Such assemblies may function to protect PSII from photodamage due to overexcitation. Received: 6 August 1999 / Accepted: 23 November 1999