Short polyP Research Articles

Inorganic polyphosphate's role in energy production and mitochondrial permeability transition pore opening in tick mitochondria.

Inorganic polyphosphate (polyP) is a biopolymer composed of phosphoanhydride-linked orthophosphate molecules. PolyP is engaged in a variety of cellular functions, including mitochondrial metabolism. Here, we examined the effects of polyP on electron transport chain enzymes and F1 Fo ATP synthase in tick embryos during embryonic development. The study found that polyPs containing medium and long chains (polyP15 and polyP65 ) enhanced the activity of complex I, complex II, complex III, and F1 Fo ATP synthase, while short polyP chains (polyP3 ) had no effect. The study also examined the activity of exopolyphosphatases (PPX) in various energy-demand situations. PPX activity was stimulated when ADP concentrations are high, characterizing a low-energy context. When complexes I-III and F1 Fo ATP synthase inhibitors were added in energized mitochondria, PPX activity decreased, whereas the mitochondrial uncoupler FCCP had no impact on PPX activity. Additionally, the study investigated the effect of polyP on mitochondrial swelling, finding that polyP causes mitochondrial swelling by increasing calcium effects on the mitochondrial permeability transition pore. The findings presented here to increase our understanding of the function of polyP in mitochondrial metabolism and its relationship to mitochondrial permeability transition pore opening in an arthropod model.

Bactericidal and bacteriostatic effects of sodium polyphosphate emulsifying salts on selected targets in processed cheese

Processed cheeses (PC) are products with extended shelf-lives, they have in their composition such additives as emulsifying salts and preservatives. Emulsifying salts are used due their desirable emulsification properties, however, little is known about their inhibitory activity against microorganisms that can survive and multiply in these products; jeopardizing cheese quality or even posing as hazards to consumers. The aim is to determine how mixtures of emulsifying salts (ESSP: emulsifying salt composed of short polyP; BSLP: bacteriostatic salt composed of long polyP; and trisodium citrate) can influence the microbial populations in PC during 90 days of storage. A total of 14 treatments (T1 - T14) were evaluated against eight target strains (Bacillus cereus INV 10(3); Bacillus subtilis ATCC 19659; Bacillus thuringiensis CFBP 3476; Clostridium perfringens ATCC 13124; Enterococcus faecalis FAIR-E 179; Listeria monocytogenes Scott A; Pseudomonas fluorescens 07A; and Staphylococcus aureus ATCC 6538) inoculated into PC. A treatment composed of emulsifying salts without antimicrobial effect (ESSP 1.5%) was considered as the positive growth control, and another treatment composed of antimicrobial additives (nisin and potassium sorbate) was considered as the negative growth control. Bacterial growth was analyzed using ANOVA and Tukey (p < 0.05), based on selected treatment grouping. Most treatments resulted in some level of bactericidal or bacteriostatic effect against the target microorganisms. Bactericidal activity was evident against Bacillus spp., and bacteriostatic effect was clear against C. perfringens, E. faecalis, L. monocytogenes and S. aureus (p < 0.05) during the storage period. T13, composed of 1.5% BSLP, presented results comparable to those observed for the negative control for bacterial inhibition in PC samples during 90 days of storage. T13 was able to reduce the B. cereus INV 10(3) and B. thuringiensis CFBP 3476 population more than the negative control (p < 0.001), as well as present better results for the inhibition of C. perfringens ATCC 13124 and L. monocytogenes Scott A by the end of storage. The performance of the negative control was better than T13 only against S. aureus - ATCC 6538 (p < 0.001). Taken together, the results contribute to expanding the understanding of emulsifying salt application in PC, with a focus on microbiological safety and shelf-life.

One of the Deepest Genera of Antipatharia: Taxonomic Position Revealed and Revised

The genus Abyssopathes Opresko, 2002, comprises deep-sea black corals known almost exclusively from lower bathyal and abyssal depths, mainly from seamounts covered by cobalt-rich crusts and areas of polymetallic nodules. The taxonomical position of the genus and its placement in the family Schizopathidae has been repeatedly questioned, but fruitlessly. Known only in extremely deep habitats, these corals have rarely been collected in a state suitable for morphological or molecular studies that could help to clarify their status. Recently, increasing attention has been paid to the study of fauna associated with deep-sea minerals. Using material of Abyssopathes lyra (Brook, 1889) sampled during these studies, we transfer the genus Abyssopathes from the family Schizopathidae to the family Cladopathidae based on morphological and molecular data. Morphological data includes six mesenteries in the polyps, a unique pinnulation pattern found only in genera within the Cladopathidae, and relatively short polyp tentacles, a feature typical of some cladopathids. Sequencing data, consisting of 626 bp from the mitochondrial cox1 gene, showed that Abyssopathes is 99% identical to Chrysopathes Opresko, 2003, Cladopathes Brook, 1889, Heteropathes Opresko, 2011, and Trissopathes Opresko, 2003 (all Cladopathidae), in this gene region.

Influence of Emulsifying Salts on the Growth of Bacillus thuringiensis CFBP 3476 and Clostridium perfringens ATCC 13124 in Processed Cheese

Processed cheese is a dairy product with multiple end-use applications, where emulsifying salts play a fundamental role in physicochemical changes during production. Moreover, some of these salts may be a strategy to control spoilage and pathogenic microorganisms, contributing to safety and shelf life extension. This study aimed to evaluate the in vitro inhibitory activity of two emulsifying salts (ESSP = short polyP and BSLP = long polyP) against Bacillus thuringiensis CFBP 3476 and Clostridium perfringens ATCC 13124, and to compare the in situ effects of two emulsifying salts treatments (T1 = 1.5% ESSP and T2 = 1.0% ESSP + 0.5% BSLP) in processed cheeses obtained by two different methods (laboratory- and pilot-scales), during 45-day storage at 6 °C. C. perfringens ATCC 13124 growth was not affected in vitro or in situ (p > 0.05), but both of the treatments reduced B. thuringiensis CFBP 4376 counts in the tested condition. Counts of the treatments with B. thuringiensis CFBP 3476 presented a higher and faster reduction in cheeses produced by the laboratory-scale method (1.6 log cfu/g) when compared to the pilot-scale method (1.8 log cfu/g) (p < 0.05). For the first time, the inhibitory effect of emulsifying salts in processed cheeses obtained by two different methods was confirmed, and changes promoted by laboratory-scale equipment influenced important interactions between the processed cheese matrix and emulsifying salts, resulting in B. thuringiensis CFBP 4376 growth reduction.

Evidence of the Reduced Abundance of Proline cis Conformation in Protein Poly Proline Tracts.

Proline is found in a cis conformation in proteins more often than other proteinogenic amino acids, where it influences structure and modulates function, being the focus of several high-resolution structural studies. However, until now, technical and methodological limitations have hampered the site-specific investigation of the conformational preferences of prolines present in poly proline (poly-P) homorepeats in their protein context. Here, we apply site-specific isotopic labeling to obtain high-resolution NMR data on the cis/trans equilibrium of prolines within the poly-P repeats of huntingtin exon 1, the causative agent of Huntington's disease. Screening prolines in different positions in long (poly-P11) and short (poly-P3) poly-P tracts, we found that, while the first proline of poly-P tracts adopts similar levels of cis conformation as isolated prolines, a length-dependent reduced abundance of cis conformers is observed for terminal prolines. Interestingly, the cis isomer could not be detected in inner prolines, in line with percentages derived from a large database of proline-centered tripeptides extracted from crystallographic structures. These results suggest a strong cooperative effect within poly-Ps that enhances their stiffness by diminishing the stability of the cis conformation. This rigidity is key to rationalizing the protection toward aggregation that the poly-P tract confers to huntingtin. Furthermore, the study provides new avenues to probe the structural properties of poly-P tracts in protein design as scaffolds or nanoscale rulers.

Correction: Resurrecting a subgenus to genus: molecular phylogeny of Euphyllia and Fimbriaphyllia (order Scleractinia; family Euphylliidae; clade V).

[This corrects the article DOI: 10.7717/peerj.4074.].

Resurrecting a subgenus to genus: molecular phylogeny of Euphyllia and Fimbriaphyllia (order Scleractinia; family Euphyllidae; clade V).

BackgroundThe corallum is crucial in building coral reefs and in diagnosing systematic relationships in the order Scleractinia. However, molecular phylogenetic analyses revealed a paraphyly in a majority of traditional families and genera among Scleractinia showing that other biological attributes of the coral, such as polyp morphology and reproductive traits, are underutilized. Among scleractinian genera, the Euphyllia, with nine nominal species in the Indo-Pacific region, is one of the groups that await phylogenetic resolution. Multiple genetic markers were used to construct the phylogeny of six Euphyllia species, namely E. ancora, E. divisa, E. glabrescens, E. paraancora, E. paradivisa, and E. yaeyamaensis. The phylogeny guided the inferences on the contributions of the colony structure, polyp morphology, and life history traits to the systematics of the largest genus in Euphyllidae (clade V) and, by extension, to the rest of clade V.ResultsAnalyses of cytochrome oxidase 1 (cox1), cytochrome b (cytb), and β-tubulin genes of 36 colonies representing Euphyllia and a confamilial species, Galaxea fascicularis, reveal two distinct groups in the Euphyllia that originated from different ancestors. Euphyllia glabrescens formed a separate group. Euphyllia ancora, E. divisa, E. paraancora, E. paradivisa, and E. yaeyamaensis clustered together and diverged from the same ancestor as G. fascicularis. The 3′-end of the cox1 gene of Euphyllia was able to distinguish morphospecies.DiscussionSpecies of Euphyllia were traditionally classified into two subgenera, Euphyllia and Fimbriaphyllia, which represented a dichotomy on colony structure. The paraphyletic groups retained the original members of the subgenera providing a strong basis for recognizing Fimbriaphyllia as a genus. However, colony structure was found to be a convergent trait between Euphyllia and Fimbriaphyllia, while polyp shape and length, sexuality, and reproductive mode defined the dichotomy better. Species in a genus are distinguished by combining polyp morphology and colony form. The cluster of E. glabrescens of the Euphyllia group is a hermaphroditic brooder with long, tubular tentacles with knob-like tips, and a phaceloid colony structure. The Fimbriaphyllia group, with F. paraancora, F. paradivisa, F. ancora, F. divisa, and F. yaeyamaensis, are gonochoric broadcast spawners with short polyps, mixed types of tentacle shapes, and a phaceloid or flabello-meandroid skeleton. Soft-tissue morphology of G. fascicularis and Ctenella chagius were found to be consistent with the dichotomy.ConclusionsThe paraphyly of the original members of the previous subgenera justify recognizing Fimbriaphyllia as a genus. The integrated approach demonstrates that combining polyp features, reproductive traits, and skeletal morphology is of high systematic value not just to Euphyllia and Fimbriaphyllia but also to clade V; thus, laying the groundwork for resolving the phylogeny of clade V.

Rational design of substrate binding pockets in polyphosphate kinase for use in cost-effective ATP-dependent cascade reactions.

Adenosine-5'-triphosphate (ATP) is the energy equivalent of the living system. Polyphosphate (polyP) is the ancient energy storage equivalent of organisms. Polyphosphate kinases (PPKs) catalyze the polyP formation or ATP formation, to store energy or to regenerate ATP, respectively. However, most PPKs are active only in the presence of long polyPs, which are more difficult and more expensive to generate than the short polyPs. We investigated the PPK preference towards polyPs by site-directed mutagenesis and computational simulation, to understand the mechanism and further design enzymes for effective ATP regeneration using short polyPs for in vitro cascade reactions, which are highly desired for research and applications. The results suggest that the short polyPs inhibit PPK by blocking the ADP-binding pocket. Structural comparison between PPK (Corynebacterium glutamicum) and PPK (Sinorhizobium meliloti) indicates that three amino acid residues, i.e., lysine, glutamate, and threonine, are involved in the activity towards short polyP by fixing the adenosine group of ADP in between the subunits of the dimer, while the terminal phosphate group of ADP still offers an active site, which presents a binding pocket for ADP. A proposed triple mutant PPK (SMc02148-KET) demonstrates significant activity towards short polyP to form ATP from ADP. The obtained high glutathione titer (38.79mM) and glucose-6-phosphate titer (87.35mM) in cascade reactions with ATP regeneration using the triple mutant PPK (SMc02148-KET) reveal that the tailored PPK establishes the effective ATP regeneration system for ATP-dependent reactions.

Phosphate Homeostasis in Conditions of Phosphate Proficiency and Limitation in the Wild Type and the phoP Mutant of Streptomyces lividans

Phosphate, as a constituent of the high energy molecules, ATP/GTP and polyphosphate, plays a crucial role in most of the metabolic processes of living organisms. Therefore, the adaptation to low Pi availability is a major challenge for bacteria. In Streptomyces, this adaptation is tightly controlled by the two component PhoR/PhoP system. In this study, the free intracellular Pi, ATP, ADP and polyP content of the wild type and the phoP mutant strain of S. lividans TK24 were analyzed at discrete time points throughout growth in Pi replete and limited media. PolyP length and content was shown to be directly related to the Pi content of the growth medium. In Pi repletion, ATP and high molecular weight (HMW) polyP contents were higher in the phoP mutant than in the WT strain. This supports the recently proposed repressive effect of PhoP on oxidative phosphorylation. High oxidative phosphorylation activity might also have a direct or indirect positive impact on HMW polyP synthesis. In Pi sufficiency as in Pi limitation, the degradation of these polymers was shown to be clearly delayed in the phoP mutant, indicating PhoP dependent expression of the enzymes involved in this degradation. The efficient storage of Pi as polyphosphate and/or its inefficient degradation in Pi in the phoP mutant resulted in low levels of free Pi and ATP that are likely to be, at least in part, responsible for the very poor growth of this mutant in Pi limitation. Furthermore, short polyP was shown to be present outside the cell, tightly bound to the mycelium via electrostatic interactions involving divalent cations. Less short polyP was found to be associated with the mycelium of the phoP mutant than with that of the WT strain, indicating that generation and externalization of these short polyP molecules was directly or indirectly dependent on PhoP.

Factor XII promotes blood coagulation independent of factor XI in the presence of long‐chain polyphosphates

Inorganic polyphosphates (polyP), which are secreted by activated platelets (short-chain polyP) and accumulate in some bacteria (long-chain polyP), support the contact activation of factor XII (FXII) and accelerate the activation of FXI. The aim of the present study was to evaluate the role of FXI in polyP-mediated coagulation activation and experimental thrombus formation. Pretreatment of plasma with antibodies that selectively inhibit FXI activation by activated FXII (FXIIa) or FIX) activation by activated FXI (FXIa) were not able to inhibit the procoagulant effect of long or short-chain polyP in plasma. In contrast, the FXIIa inhibitor, corn trypsin inhibitor, blocked the procoagulant effect of long and short polyP in plasma. In a purified system, long polyP significantly enhanced the rate of FXII and prekallikrein activation and the activation of FXI by thrombin but not by FXIIa. In FXI-deficient plasma, long polyP promoted clotting of plasma in an FIX-dependent manner. In a purified system, the activation of FXII and prekallikrein by long polyP promoted FIX activation and prothombin activation. In an ex vivo model of occlusive thrombus formation, inhibition of FXIIa with corn trypsin inhibitor but not of FXI with a neutralizing antibodies abolished the prothrombotic effect of long polyP. We propose that long polyP promotes FXII-mediated blood coagulation bypassing FXI. Accordingly, some polyp-containing pathogens may have evolved strategies to exploit polyP-initiated FXII activation for virulence, and selective inhibition of FXII may improve the host response to pathogens.

Role of Polyphosphate in Mitochondria: From Modification of Energy Metabolism to Induction of the Cell Death

Inorganic polyphosphate (polyP) is found in all living organisms ranging from bacteria to mammals. PolyP plays multiple physiological functions, which are distinct and dependent on the type of organism and the subcellular localization of the polymer. Recently we demonstrated that polyP levels are dependent on the cell metabolism and can be changed by mitochondrial substrates and inhibitors. We propose the existence of a feedback mechanism where polyP production and cell energy metabolism regulate each other. In order to investigate this we study the effect of polyP on mitochondrial oxygen consumption. We have found that application of short polyP (14 phosphate residues) or medium polyP (70 ortophosphates) significantly increase the level of respiratory coefficient by activation of state V3 and inhibition of V4 compare to control. Importantly, both short and medium polyP significantly reduced efficiency of oxidative phosphorylation (ADP/O ratio). It has previously been reported that polyP can modify membrane permeability for ions that can be a trigger for changes in mitochondrial metabolism. Furthermore polyP has been linked to activation of the mitochondrial permeability transition pore (mPTP) in different cells that also can be activated by calcium. Long, medium, and in lower degree, short polyP increase permeability of de-energised mitochondria for Ca2+. This effect was dependent on inhibitor of mPTP - cyclosporine A. We also found that long polyP (130 orthophosphates) caused cell death in primary neurons and astrocytes, while medium (70) polyP had a much smaller effect and short (14) did not cause any. Thus, polyP has a multiple action on mitochondrial function from modification of mitochondrial energy metabolism to stimulation of calcium permeability and cell death.

FXII Promotes Coagulation in a FXI and FIX Independent Manner

AbstractAbstract 3362Activation of coagulation factors (F) XII and XI support thrombogenesis through multiple pathways. FXII-deficient mice are more resistant to FeCl3-induced arterial occlusion than either FIX or FXI deficient mice, suggesting that the resistance of FXII-deficient mice to experimental thrombosis is not completely explained by the FXII-FXI-FIX pathway, suggesting the existence of a pathological FXII by-pass, in vivo.The APTT of FXII deficient plasma is longer than the APTT of FXI, FIX, or FX deficient plasmas. We found that addition of 150 nM activated FXII (FXIIa) decreased the recalcification time of FXI or FIX-deficient plasma by up to 85%. In a purified system FXIIa could activate prothrombin but not FX. Addition of rivaroxaban, a FXa inhibitor, to FXI or FIX-deficient plasma blocked the observed procoagulant effect of FXIIa, suggesting that FXIIa promotes the activation of FX independent of FXI or FIX, but the ability of FXIIa alone to induce coagulation is insufficient in plasma, in vitro.Addition of long polyphosphate (polyP), typically found in bacteria, but not short polyP, which is secreted by activated platelets, decreased the recalcification time of FXI or FIX-deficient plasma. The presence of either corn trypsin inhibitor (CTI), that inhibits FXIIa, or rivaroxaban blocked the procoagulant effect of long polyP, suggesting that the activation of FXII by long polyP promotes coagulation in an FXI- and FIX-independent manner.Addition of CTI or an antibody that inhibits FIX activation by FXIa, but not addition of an antibody that inhibits activation of FXI by FXIIa, increased the time of occlusive thrombus formation in recalcified human blood that was driven through collagen and tissue factor (TF)-coated capillary tubes, consistent with the thrombogenic roles of FXIIa and feedback activation of FXI. Only CTI inhibited the prothrombotic effect of long polyP, also suggesting that FXIIa could be thrombogenic independent of FXI and FIX.In summary, we propose that pathological FXII activation, e.g., by foreign surfaces or long polyP, is thrombogenic both in FXI/FIX-dependent and -independent manners. Provided that FXII has no significant physiological function in humans, our data support the hypothesis that inhibition of FXII activity or activation may have safe antithrombotic effects. Disclosures:Morrissey:No organization, but the speaker is co-inventor on pending patent applications on the medical uses of polyphosphate: Patents & Royalties.

Defining purpose: a key step in genetic test evaluation

The introduction of new genetic tests, like other medical innovations, can be conceptualized as a three-step process. Tests are proposed for use based on research findings and clinical reasoning; an evaluation occurs; and judgments are made about clinical use and reimbursement (Fig. 1). The evaluation may be informal, as when a clinician determines whether a new test will be helpful in a particular patient encounter, or formal, as when a practice guideline panel utilizes a defined methodology to assess a test or a health care funder utilizes a set of criteria to determine test coverage. Although genetic tests are often described in terms of technology, a full evaluation requires that the test be considered as a clinical process in which the laboratory assay, or other testing procedure, is done to acquire information about a particular health condition, in a defined population, for a specific clinical purpose.1 Genetic tests have a wide range of health care applications. They are used to confirm the presence of a genetic condition, identify reproductive risks, and select preventive therapy. Testing occurs in newborn screening programs and in primary, specialty, and prenatal care, and may be initiated on the basis of clinical symptoms, family history, or population demographics. Genetic tests also utilize a range of technologies, and vary considerably in their predictive value. This diversity poses a challenge for the evaluation process. Several groups have considered methods for genetic test evaluation,2–5 and model programs for systematic evaluation have been established in the United States (Evaluation of Genomic Applications in Practice and Prevention6) and the UK (the UK Genetic Testing Network7). To date, however, the evaluation process has not fully addressed the clinical diversity of genetic tests. The Evaluation of Genomic Applications in Practice and Prevention project has focused on genetic tests related to common disorders and drug therapy, whereas the United Kingdom Genetic Testing Network has primarily addressed tests for single gene disorders. An effort by the Secretary’s Advisory Committee on Genetic Testing to categorize genetic tests into those requiring higher versus lower levels of scrutiny was not successful.8 To address the challenge of genetic test diversity, we propose an outcome-orientated taxonomy for defining test purpose. A focus on health outcomes allows the definition of a small and informative set of purposes for genetic testing, despite the range of technologies and clinical settings in which testing occurs. Defining test purpose in turn clarifies the benefits to be expected from the testing process, and provides guidance to clinicians and policy makers concerning the evidence needed to support test use. Defining test purpose, therefore, is an important first step in genetic test evaluation.

Polyphosphate:AMP Phosphotransferase and Polyphosphate:ADP Phosphotransferase Activities of Pseudomonas aeruginosa

In Pseudomonas aeruginosa PAO1, we have found massive polyphosphate:AMP phosphotransferase activity and polyphosphate:ADP phosphotransferase activity known as the reverse catalytic activity of polyphosphate kinase which participates in polyphosphate synthesis in the bacterium. Biochemical analysis using the partially purified polyphosphate:ADP phosphotransferase has revealed that it is independent of polyphosphate kinase and can function as polyphosphate-dependent nucleoside diphosphate kinase which most prefers GDP to the other three nucleoside diphosphates as a phospho-acceptor. It has been also demonstrated that polyphosphate:AMP phosphotransferase activity marked in the bacterium mainly originates from the combined action of the polyphosphate:ADP phosphotransferase described above and adenylate kinase. Both of the polyphosphate-utilizing activities require short polyP as a phospho-donor whose chain length is <75.

Inorganic Polyphosphates in the Acquisition of Competence in Escherichia coli

A complex of polyhydroxybutyrate (PHB), Ca2+, and inorganic polyphosphate (polyP) was proposed as the membrane component responsible for competence for DNA entry in Escherichia coli (Reusch, R. N., and Sadoff, H. L. (1988) Proc. Natl. Acad. Sci. U.S.A. 85, 4176-4180). While chemical and immunological assays and 1H NMR have unequivocally established the identity and content of PHB in the complex, comparable methods were not available for polyP. With specific enzyme assays developed for polyP, we have identified, in chloroform extracts of competent cell membranes, a novel form of polyP of about 60 to 70 residues in a stoichiometric ratio of PHB to polyP of 2:1. In E. coli mutants, incapable of synthesizing the predominant, thousand-long polyP chains, appearance of this short polyP and its inclusion in membranes can account for their capacity to develop competence and indicates an auxiliary pathway for polyP synthesis. A variety of fluorescent lipid probes demonstrate the appearance of extensive rigid domains in membranes of competent cells. We propose that the PHB.Ca2+.polyP complex perturbs the conformation of the lipid matrix, making it more permeable to charged molecules and thus allowing the entry of DNA.

The effects of flow on feeding of three gorgonians from southern Taiwan

The feeding performances of three gorgonians, Subergorgia suberosa, Melithaea ochracea, Acanthogorgia vegae, in different flow regimes were studied. The three gorgonians expanded their polyps and fed in varying ranges of flow velocities. Differences in the feeding range are possibly related to polyp morphologies. S. suberosa, which has tall polyps and encounters higher drag, is more easily deformed in currents; it feeds in a narrow range of flow velocities (7–9 cm·s −1). M. ochracea, which has short polyps and encounters lower drag, is less readily deformed in currents; it feeds in a wider range of flow velocities (4–40 cm·s −1). Polyp heights of A. vegae are intermediate and this coral feeds in currents of 2–22 cm·s −1. The upper limits on the flow ranges are considered to be determined by the balance between the energy gained from feeding and the cost of keeping the polyps expanded. Optimal feeding rates of the three gorgonians were found at moderate flow velocities. Feeding rates increased initially with flow velocity, reached a peak value at 8 cm·s −1, then decreased with increasing flow velocities. Both the colony feeding effectiveness and the polyp feeding effectiveness at 8 cm·s −1 are ranked: S. suberosa >A. vegae>M. ochracea.

SURFACE BROODING IN THE RED SEA SOFT CORAL PARERYTHROPODIUM FULVUM FULVUM (FORSKÅL, 1775).

Parerythropodium fulvum fulvum (Forskål, 1775) is an encrusting soft coral commonly found between 3 and 40 m, at the coral reefs of the Gulf of Eilat. The annual gonadal development and sexual reproduction of this species were studied both in shallow water (3-5 m) and in the deep reef zone (27-30 m). P. f. fulvum is a dioecious species. Sex ratio of the shallow population favors higher abundance of females, while on the deep reef a 1:1 sex ratio was recorded. These differences are probably due to local aggregations of colonies of the same sex caused by asexual reproduction. Oocytes and sperm sacs are found even in very young colonies (1-3 years). The frequency of sexually mature males is higher than mature females among small corals. Young oocytes appear annually in August and within 10-11 months reach their maximal diameter. Sperm sacs start to develop later and mature after 7-9 months. A marked synchronization in the development of the oocytes and the testes exists among different polyps within each colony. Spawning occurs at dusk, and is fully synchronized by lunar periodicity (a few days after the new moon and a few days preceeding its last quarter). Fertilization takes place inside the polyp cavities. The shallow water population breeds prior to the deeper one with the whole reproductive period lasting approximately two months (end of June, beginning of August). Among anthozoans, P. f. fulvum represents a unique mode of sexual reproduction and planulae development. This species is oviparous, yet eggs cleave on the surface of the female colonies while entangled in a mucoid suspension. We term this mode of planula development "surface brooding". Within 6 days after fertilization the planulae complete their development, detach from the surface of the colony, and sink to the bottom. The encrusting growth form of P. f. fulvum is characterized by a thin coenenchyme and short polyp cavities, yet the eggs exhibit a large diameter (500-700 µm). Egg production of P. f. fulvum is rather low (18-24 eggs per polyp), but it is compensated for by surface brooding, which protects the offspring during embryogenesis. It is suggested that surface brooding is an adaptation to the encrusting shape of the colony and it maximizes fecundity.