Colony size as a species character in massive reef corals

In a study of seven massive, Caribbean corals, I have found major differences in reproductive behavior between species with large maximum colony sizes and species with smaller maximum colony sizes. Four species (Diploria clivosa, D. strigosa, Montastrea cavernosa, Siderastrea siderea) which are large (<1000 cm² in surface area) broadcast gametes during a short spawning season. Their puberty size is relatively large (>100 cm², except M. cavernosa). In contrast, two small massive species (<100 cm², Favia fragum and S. radians), and one medium-sized (100–1000 cm², Porites astreoides) massive species, brood larvae during an extended season (year-round in Panama). The puberty size of the small species is only 2–4 cm². Given these close associations between maximum colony sizes and a number of fundamental reproductive attributes, greater attention should be given to the colony size distributions of different species of reef corals in nature, since many important life history and population characters may be inferred.     

Colony formation in the cyanobacterium Microcystis

Morphological evolution from a unicellular to multicellular state provides greater opportunities for organisms to attain larger and more complex living forms. As the most common freshwater cyanobacterial genus, Microcystis is a unicellular microorganism, with high phenotypic plasticity, which forms colonies and blooms in lakes and reservoirs worldwide. We conducted a systematic review of field studies from the 1990s to 2017 where Microcystis was dominant. Microcystis was detected as the dominant genus in waterbodies from temperate to subtropical and tropical zones. Unicellular Microcystis spp. can be induced to form colonies by adjusting biotic and abiotic factors in laboratory. Colony formation by cell division has been induced by zooplankton filtrate, high Pb²⁺ concentration, the presence of another cyanobacterium (Cylindrospermopsis raciborskii), heterotrophic bacteria, and by low temperature and light intensity. Colony formation by cell adhesion can be induced by zooplankton grazing, high Ca²⁺ concentration, and microcystins. We hypothesise that single cells of all Microcystis morphospecies initially form colonies with a similar morphology to those found in the early spring. These colonies gradually change their morphology to that of M. ichthyoblabe, M. wesenbergii and M. aeruginosa with changing environmental conditions. Colony formation provides Microcystis with many ecological advantages, including adaption to varying light, sustained growth under poor nutrient supply, protection from chemical stressors and protection from grazing. These benefits represent passive tactics responding to environmental stress. Microcystis colonies form at the cost of decreased specific growth rates compared with a unicellular habit. Large colony size allows Microcystis to attain rapid floating velocities (maximum recorded for a single colony, ∼ 10.08 m h⁻¹) that enable them to develop and maintain a large biomass near the surface of eutrophic lakes, where they may shade and inhibit the growth of less‐buoyant species in deeper layers. Over time, accompanying species may fail to maintain viable populations, allowing Microcystis to dominate. Microcystis blooms can be controlled by artificial mixing. Microcystis colonies and non‐buoyant phytoplankton will be exposed to identical light conditions if they are evenly distributed over the water column. In that case, green algae and diatoms, which generally have a higher growth rate than Microcystis, will be more successful. Under such mixing conditions, other phytoplankton taxa could recover and the dominance of Microcystis would be reduced. This review advances our understanding of the factors and mechanisms affecting Microcystis colony formation and size in the field and laboratory through synthesis of current knowledge. The main transition pathways of morphological changes in Microcystis provide an example of the phenotypic plasticity of organisms during morphological evolution from a unicellular to multicellular state. We emphasise that the mechanisms and factors influencing competition among various close morphospecies are sometimes paradoxical because these morphospecies are potentially a single species. Further work is required to clarify the colony‐forming process in different Microcystis morphospecies and the seasonal variation in this process. This will allow researchers to grow laboratory cultures that more closely reflect field morphologies and to optimise artificial mixing to manage blooms more effectively.     

Colonial development in Pandorina morum. II. Colony morphogenesis and formation of the extracellular matrix

The colonial green alga, Pandorina morum, resembles its unicellular relative Chlamydomonas in both intracellular architecture and the composition of the extracellular matrix. Despite these similarities, cell division in Pandorina leads to the formation of a colony instead of the 8 or 16 single cells produced by cell division in Chlamydomonas. To study colony formation, partially synchronized cultures of P. morum were sampled periodically and stained with ruthenium red for electron microscopy. The cells of the colony were found to be held together during development by medial and basal connections between cells; the basal connections include strands of chloroplast. Studies of cells removed from the parental matrix before division confirmed that the cytoplasmic connections are strong enough to maintain the colonial configuration. After the medial connections break, the cells of the plate of the developing colony swing outward and attain the nearly spherical colonial configuration; the basal connections are still present. After this inversion, the formation of the extracellular matrix begins, with the colonial boundary appearing first. Capsule and sheath then form on the outer and inner faces of the colonial boundary until the extracellular matrix is complete. The process is compared to previous observations of Volvox, and possible evolutionary implications are discussed.     

Sexual reproduction,development and larval biology in scleractinian corals

This paper brings together widely scattered information on sexual reproduction in scleractinian corals. It includes a review of information and ideas on sex determination, gametogenesis, gametogenic cycles, fertilization and embryonic development, spawning and planula release, larval behavior, settlement and metamorphosis. The review deals with corals from different habitats and organismic assemblages, including tropical reef corals, temperate water corals, solitary and colonial forms. A summary table of coral species and their known reproductive characteristics is presented.     

Colony formation and inversion in the green algaEudorina elegans

Summary During development of daughter coenobia in the volvocalean algaEudorina a rapid synchronized series of mitotic divisions and cytokineses gives rise to a slightly cup-shaped, patterned array of 16 or 32 cells, the plakea; the nuclei and centrioles of each cell lying at the concave face and the plastids at the convex face. Each cell is connected to its neighbours by cytoplasmic bridges. All cells within a plakea simultaneously elongate and enlarge their nuclear poles; while remaining interconnected by the cytoplasmic bridges at their plastid poles. The result is inversion of the developing coenobia so that the nuclei and centrioles come to lie on the convex, outer surface. Inversion is inhibited by colchicine and cytochalasin B. Both lengthening of the cells and expansion of their nuclear end is apparently mediated by microtubules. Striations on the plasmalemma encircling the bridges are thought to stablize the membrane at these sites during inversion.     

Larval development of certain gamete-spawning scleractinian corals

Embryogenesis and larval development were documented in 19 species of hermatypic scleractinians which release gametes during the summer coral spawning season on the Great Barrier Reef. Cleavage of fertilized eggs began approximately 2 h after spawning in all species, and gave rise to blastulae after 7–10 h. Endoderm formation in Platygyra sinensis was by invagination, and this appeared to occur in all species studied. All species observed at 36 h after spawing were mobile and full mobility was reached by 48 h. Settlement of planulae placed in aquaria occurred between 4 and 7 days after fertilization. These results suggest that larval corals produced by most gamete-releasing coral species are likely to be dispersed away from the parent reef.     

Colony formation of free-living and particle-associated sulfate-reducing bacteria

Abstract Some of the components that are likely to be involved in the respiratory chains that transfer electrons from the ferrous iron substrate of various acidophilic bacteria have been revealed by spectroscopic analysis. An apparently unique, soluble and acid-stable cytochrome was found in Leptospirillum ferrooxidans which appeared to lack any of the major cytochromes or the rusticyanin of the better-studied iron-oxidizing mesophile, Thiobacillus ferrooxidans . A specific absorption peak, only found in iron-grown cells, was revealed in a whole cell spectra of thermoacidophilic archaebacteria of different genera.     

Larval development and survivorship in the corals Favia favus and Platygyra lamellina

Two Red Sea faviid species, Favia favus and Platygyra lamellina spawn eggs and sperm once a year, during the summer. External fertilization occurs 0.5 h after spawning, and mobile gastrulae appear 20 h later. Four stages in the early ontogenesis of these corals are described. The slow development (2–3 months) to the polyp stage in broadcasting species is attributed to the lack of zooxanthellae in their planulae and their appearance in the primary polyp only at a later stage. Survivorship of one-month-old primary polyps is ca 0.21% and 0.25% in F. favus and P. lamellina respectively, from the populations of 2–9-day-old planulae. Despite these low rates of survival, both species form dense populations in the Gulf of Eilat.     

Colony formation by chicken hematopoietic cells and virus-induced myeloblasts

Leukemic myeloblasts and cells derived from normal chick hematopoietic tissue produced colonies in soft agar. Colonies produced by leukemic myeloblasts differed from normal chick tissue in their morphological characteristics, in the greater initial number of cells required for colony formation and in their decreased dependence on conditioned medium for development. The colony forming cells for both types were enriched when allowed to grow for several days in liquid growth medium. In soft agar, myeloblasts differentiated into more mature granulocytic cells and macrophages. These differentiated cells accumulated between one and two weeks after seeding. When tested for release of avian myeloblastosis virus (AMV), 6 out of 18 colonies were releasing AMV at one week whereas 3 out of 39 were releasing AMV at two weeks. Five two week old colonies which were negative for AMV were producing myeloblastosis associated viruses (MAVs). Normal colony forming cells were present in leukemic buffy coat and although colonies made by these cells contained MAVs, no AMV could be detected. The data obtained with normal avian tissues were similar to those obtained by others with mammalian hematopoietic tissue. Colony formation by normal hematopoietic tissues was strictly dependent on factors present in conditioned medium. Tissues producing colonies included bone marrow, yolk sac, spleen and peripheral leukocytes. Colonies were not obtained from thymus and bursa. Furthermore, the colony origin did not appear to be erythroid in nature.     

Colony formation in agar by multipotential hemopoietic cells.

Agar cultures of CBA fetal liver, peripheral blood, yolk sac and adult marrow cells were stimulated by pokeweed mitogen-stimulated spleen conditioned medium. Two to ten percent of the colonies developing were mixed colonies, documented by light or electron microscopy to contain erythroid, neutrophil, macrophage, eosinophil and megakaryocytic cells. No lymphoid cells were detected. Mean size for 7-day mixed colonies was 1,800-7,300 cells. When 7-day mixed colonies were recloned in agar, low levels of colony-forming cells were detected in 10% of the colonies but most daughter colonies formed were small neutrophil and/or macrophage colonies. Injection of pooled 7-day mixed colony cells to irradiated CBA mice produced low numbers of spleen colonies, mainly erythroid in composition. Karyotypic analysis using the T6T6 marker chromosome showed that some of these colonies were of donor origin. With an assumed f factor of 0.2, the mean content of spleen colony-forming cells per 7-day mixed colony was calculated to vary from 0.09 to 0.76 according to the type of mixed colony assayed. The fetal and adult multipotential hemopoietic cells forming mixed colonies in agar may be hemopoietic stem cells perhaps of a special or fetal type.     

Colony aggregation and biofilm formation in xylem chemistry-based media for Xylella fastidiosa

Two chemically defined media based on xylem fluid chemistry were developed for Xylella fastidiosa. These media were tested and compared to chemically defined media XDM2, XDM4 and XF-26. New media were evaluated for the Pierce's disease (PD) strain UCLA-PD. Our media either was similar to the concentration of some amino acids found in the xylem fluid of the PD-susceptible Vitis vinifera cv. Chardonnay (medium CHARD2) or incorporated the tripeptide glutathione found in xylem fluid composition (medium 3G10-R). CHARD2 and 3G10-R are among the simplest chemically defined media available. Xylem fluid chemistry-based media supported X. fastidiosa growth and especially stimulated aggregation and biofilm formation.     

Colony formation in agar by adult bone marrow multipotential hemopoietic cells

Erythroid colony formation in agar cultures of CBA bone marrow cells was stimulated by the addition of pokeweed mitogen-stimulated spleen conditioned medium (SCM). Optimal colony numbers were obtained when cultures contained 20% fetal calf serum and concentrated spleen conditioned medium. By 7 days of incubation, large burst or unicentric erythroid colonies occurred at a maximum frequency of 40–50 per 10⁵ bone marrow cells. In CBA mice the cells forming erythroid colonies were also present in the spleen, peripheral blood, and within individual spleen colonies. A marked strain variation was noted with CBA mice having the highest levels of erythroid colony-forming cells. In CBA mice erythroid colony-forming cells were mainly non-cycling (12.5% reduction in colony numbers after incubation with hydroxyurea or 3H-thymidine). Erythroid colony-forming cells sedimented with a peak of 4.5 mm/hr, compared with CFU-S, which sedimented at 4.25 mm/hr. The addition of erythropoietin (up to 4 units) to cultures containing SCM did not alter the number or degree of hemoglobinisation of erythroid colonies. Analysis of the total number of erythroid colony-forming cells and CFU-S in 90 individual spleen colonies gave a correlation coefficient of r = 0.93 for these two cell types. In addition to benzidine-positive erythroid cells, up to 40% of the colonies contained, in addition, varying proportions of neutrophils, macrophages, eosinophils, and megakaryocytes. Taken together with the close correlation between the numbers of CFU-S in different adult hemopoietic tissues, including individual spleen colonies, the data indicate that the erythroid colony-forming cells expressing multiple hemopoietic differentiation are members of the hemopoietic multipotential stem cell compartment.     

Colony formation and plant regeneration from mesophyll protoplasts of Solanum etuberosum

A procedure for the culture of Solanum etuberosum mesophyll protoplasts with subsequent shoot regeneration is described. Several factors affected protoplast yield, colony formation, and shoot regeneration from in vitro plants. A protoplast isolation medium with 0.6 M sucrose produced twice the yield as one with 0.3 M sucrose. uowever, a higher concentration of osmoticum was inhibitory to colony development unless it was diluted into a lower osmoticum medium in a bilayer system. A 16 hour light/8 hour dark photoperiod for stock plants allowed twice the protoplast yield compared to plants grown under continuous light but no effect was found on subsequent colony formation or shoot regeneration. The concentrations of four major salts in the protoplast plating medium were critical for a high frequency of colony formation from protoplasts. Levels of 0.25 × or 1 × were considerably better than 4 ×. Fast colony formation, but at a lower efficiency, was obtained with a monolayer plating method. A bilayer plating system allowed a higher efficiency but colonies developed more slowly. For the best treatments, the frequency of colony formation from protoplasts ranged from 2.4 to 3.6 × 10^-3 with 37% to 66% of the colonies producing shoots ten weeks after protoplast isolation.Cooperative investigation of the USDA-ARS and the Wisconsin Agric. Exp. Stn.     

Colony formation in Scenedesmus: grazer-mediated release and chemical features of the infochemical

In the unicellularly growing green alga Scenedesmus acutus, the formation of many-celled coenobia may be induced by an infochemical released by the grazer Daphnia magna. We used a standardized bioassay to obtain information about the release of the infochemical by actively feeding D.magna and its chemical nature. The infochemical could not be extracted from the alga or the grazer by aqueous or more lipophilic solvents. When the release of coenobia-inducing activity by actively feeding D.magna was investigated as a function of the individual's body mass, no increase with increasing individual body mass was observed, indicating that the chemical cue originates for zooplankton's non-digestive metabolism rather than from digestion of alga by the grazer. The infochemical released by D.magna can be characterized as an olefinic low-molecular-weight carboxylic acid. Hydroxy and amino groups can be excluded as moieties of the infochemical essential for biological activity. We present a method to concentrate the infochemical from Daphnia incubation water using lipophilic solid-phase extraction. Subsequent separation by reversed-phase HPLC yielded only one active fraction.      

Constructal pattern formation in stony corals, bacterial colonies and plant roots under different hydrodynamics conditions

This paper explores a new application of the constructal theory, namely in describing and predicting the formation of dissimilar patterns inside elements of the same species under different hydrodynamics conditions. Our study proposes an explanation for the differences found in morphology of stony corals, bacterial colonies and plant roots. It specially provides an answer to the following question: have their shapes (architecture) been developed by chance, or do they represent the optimum structure serving their ultimate purpose? We show that in order to persist in time, these systems must evolve in such a way that an easy access to nutrients is ensured: their shapes develop in such a way as to minimize the time to reach the nutrient source. Moreover, it is also shown that it is the combination of a dispersive (diffusive) and a convective mechanism that allows for the maximization of nutrient transfer through use of the best of these mechanisms at a specific time. In the light of this outcome, it is straightforward to conclude why the existence of an optimal architecture makes sense: it is because there is an overriding natural tendency and because the system has the freedom to morph its shape in the search for an optimal attainment of this goal within a set of constraints imposed by the situation.