A Motility Revertant of the <Emphasis Type="Italic">ndvB</Emphasis> Mutant of <Emphasis Type="Italic">Bradyrhizobium japonicum</Emphasis>

A motility revertant of a Bradyrhizobium japonicum ndvB mutant was isolated and characterized. The ndvB mutants of B. japonicum have been reported to be osmotically sensitive, as well as defective in motility, periplasmic cyclic -(13), (16)-D-glucan synthesis, and symbiosis with soybean. The motility revertant was restored for osmotic tolerance but not for cyclic -glucan production or effective symbiosis. These results support our hypothesis that cyclic -glucans have an important role in symbiosis—the suppression of a plant defense response—in addition to their role in periplasmic osmoprotection.     

Characterization of Na,K-ATPase genes in Atlantic salmon (<Emphasis Type="Italic">Salmo salar</Emphasis>) and comparative genomic organization with rainbow trout (<Emphasis Type="Italic">Oncorhynchus mykiss</Emphasis>)

A combination of molecular and in silico approaches was employed to assemble a survey of Na, K-ATPase genes contained in the ancestrally tetraploid genome of the Atlantic salmon (Salmo salar). Molecular characterization of genomic clones coding for the subunit revealed two single genes (1a and 2) and two pairs of presumably homeologous genes (1b/i-ii and 1c/i-ii). Each of the six genes showed high sequence similarity to isoforms previously isolated from rainbow trout and extensive structural differences relative to putative orthologs in the human genome. In silico analysis of expressed sequence tag (EST) collections indicated that at least five (1a, 1b, 1c, 2, and 3) and four (1a, 1b, 2, and 3b) subunit isoforms are expressed in Atlantic salmon. Meiotic linkage analysis further showed that Na, K-ATPase genes are dispersed throughout the salmon genome, with the exception of two multigene clusters on linkage groups AS-22 and AS-28. Duplicate gene copies for the isoform 1b were assigned to linkage groups with multiple homeologous anchors (AS-22 and AS-23), while 2 duplicates suggested a new homeologous affinity between AS-05 and AS-28. In addition, the comparison of linkage arrangements with rainbow trout also showed that the genomic organization of Na, K-ATPase genes is consistent with the evolutionary conservation of syntenic chromosome regions between these species.Electronic Supplementary Material Supplementary material is available for this article at .     

Enhancement of enzyme activity and enantioselectivity by cyclopentyl methyl ether in the transesterification catalyzed by <Emphasis Type="Italic">Pseudomonas cepacia</Emphasis> lipase co-lyophilized with cyclodextrins

The solvent effects of cyclopentyl methyl ether (CPME) on the reaction rates and enzyme enantioselectivity in the enantioselective transesterifications of racemic 6-methyl-5-hepten-2-ol (racemic sulcatol: SUL) and racemic 2,2-dimethyl-1,3-dioxolane-4-methanol (racemic solketal: SOL) with a series of enol esters catalyzed by Pseudomonas cepacia lipase co-lyophilized with cyclodextrins (-, -, -, partially methylated -,and 2,3,6-tri-O-methyl--cyclodextrin: CyD; CyD; CyD; Me_1.78 CyD; Me₃CyD) were investigated and compared with those in diisopropyl ether (IPE). In the case of SUL, enzyme activities of the co-lyophilizate with Me_1.78 CyD in CPME were lower than those in IPE with every acyl source, however, the absolute enantiopreference was shown in the transesterification with vinyl butyrate (VBR) in IPME. When the substrates were SOL and VBR, the enzyme activities in CPME were greatly enhanced as high as 1.6–9.8-fold, while the enantioselectivities in CPME were comparable to those in IPE.Revisions requested 16 December 2004; Revisions received 17 January 2005     

Biosynthesis of pectic galactan by membrane-bound galactosyltransferase from soybean (<Emphasis Type="Italic">Glycine max</Emphasis> Merr.) seedlings

We investigated the properties of a galactosyltransferase (GalT) that is involved in the synthesis of -(14)-galactan side chains of pectins. A membrane preparation of etiolated 6-day-old soybean (Glycine max Merr.) hypocotyls transferred [¹⁴C]Gal from UDP-[¹⁴C]Gal into intact and partially hydrolyzed lupin -(14)-galactans of various chain lengths as exogenous acceptors, while activity to endogenous acceptors was negligible. Maximal activity occurred at pH 6.5 and 20–25°C in the presence of 25 mM Mn²⁺ and 0.75% Triton X-100. The transfer reaction onto the unmodified commercial pectic galactan (M _r>150,000) from lupin we used was very low but increased when the M _r of the galactan was reduced by partial acid hydrolysis. Among the partially hydrolyzed galactans, high-M _r (average M _r 60,000) -(14)-galactan was a more efficient acceptor [specific activity 2,000–3,000 pmol min^–1 (mg protein)^–1] than low-M _r (average M _r 10,000 and 5,000) polymers. Digestion of the radiolabeled product from high-M _r galactan with endo--(14)-galactanase released mainly radioactive -(14)-galactobiose and Gal, indicating that the transfer of [¹⁴C]Gal occurred through -(14)-linkages. HPLC analysis showed that the enzyme also catalyzes incorporation of Gal into pyridylaminated (PA) -(14)-galactooligomers with degree of polymerization at least 5. Gal₇-PA chains were elongated by attachment of one, two, or three Gal residues leading to the formation of Gal_8–10-PA.Abbreviations AGP Arabinogalactan-protein - Ara Arabinose - DP Degree of polymerization - GalA Galacturonic acid - Gal _n -PA Pyridylaminated -(14)-galactooligosaccharides - GalT Galactosyltransferase - MALDI–TOF–MS Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry - Rha Rhamnose Sugars described in this paper belong to the d-series unless otherwise noted     

<Emphasis Type="Italic">In vitro</Emphasis> induction of polyploidy in annatto (<Emphasis Type="Italic">Bixa orellana</Emphasis>)

The present work aims to establish a protocol for in vitro polyploidization using hypocotyl segments or cotyledonary nodes from in vitro grown annatto seedlings. The culture medium used to induce polyploidization was supplemented with MS salts, B5 vitamin complex, 100 mg l^– myo-inositol, 3% (w/v) sucrose, 2.28 M ZEA and 0.30 M IAA (hypocotyl segments) or 4.56 M ZEA (cotyledonary nodes), 0.8% (w/v) agar, and different concentrations of microtubule depolymerising agents, namely colchicine (0, 25, 250 and 1250 M) and oryzalin (0, 5, 15 and 30 M). To determine the optimum duration of either colchicine or oryzalin treatment for the induction of tetraploids, explants were treated for 15 or 30 days on regeneration medium. High frequencies of polyploidy in regenerated shoots from cotyledonary nodes were achieved in culture medium supplemented with 15 M oryzalin, for 15 days. Ploidy determination was based on chromosome counting in metaphasic cells from apical buds, and in the number of pairs of heterochromatic markers on the biggest chromosome, as visualized in interphasic nuclei, detection being easier in the latter. Among the characteristics evaluated, the measurements based on stomata length, width, area and frequency enabled greater discrimination between diploid and polyploid regenerated shoots.     

<Emphasis Type="Italic">In vitro</Emphasis> screening of sugarcane to evaluate smut susceptibility

Tissue-cultured plantlets of three sugarcane (Saccharum spp.) cultivars having a known field smut reaction were screened for susceptibility to Ustilago scitaminea H&P Sydow. Plantlets were inoculated with 0.5 l of a suspension of equally mixed quantities of plus and minus mating type sporidia of U. scitaminea at concentrations ranging from 1×10¹ to 1×10⁶ cells. Fungal sori (whips) were produced in cultivar N12 (intermediate) 6weeks following inoculation with 1×10⁵ mixed sporidia and thereafter in cultivar NCo310 (susceptible) but not in cultivar N19 (resistant). Sori bearing teliospores were produced up to 3months following inoculation and incubation at 26°C. No sori were produced at mixed sporidial concentrations lower than 1×10⁵cells. The in vitro soral production in cultivars N19, N12 and NCo310 was 0, 27.5 and 47.5% respectively. Plantlets inoculated with 1×105sporidia of only one mating-type did not produce sori in any of the three cultivars tested. Blind scoring of an unknown sugarcane cultivar by this method corresponded exactly with its field smut rating.     

Cell volume distribution dynamics of <Emphasis Type="Italic">Chlorella</Emphasis><Emphasis Type="Italic">vulgaris</Emphasis> Beij. in batch cultures under continuous light

Cell volume distribution in Chlorella vulgaris cultures coming out of senescence was measured by flow cytometry every 6 h for 114 h in a full-factorial experiment with initial nitrate (420–4200 g NO₃-N l^–1), phosphate (9–186 g PO₄-P l^–1), and continuous light (50–330 E m^–2 s^–1) as treatments. The maxima in median and median absolute deviation (MAD) of cell volume were achieved within 6 h of each other and their timing was not affected by any treatment. Population specific growth rate during the first 66 h calculated from volume distribution changes was significantly affected by light treatment only (p=0.002).Revisions requested 4 November 2004; Revisions received 17 January 2005     

Transformation of pollen embryo-derived explants by <Emphasis Type="Italic">Agrobacterium tumefaciens</Emphasis> in <Emphasis Type="Italic">Hyoscyamus niger</Emphasis>

Leaf, root, stem, petiole, hypocotyl, and zygotic embryo explants, as well as pollen embryoids, and redifferentiated tissues from pollen embryoid-derived plantlets of Hyoscyamus niger L. (black henbane) were inoculated with Agrobacterium tumefaciens, harboring binary vectors (pGS Gluc1) and then cultured on media containing kanamycin. Transient -glucuronidase activity and kanamycin resistant callus formation were influenced by explant origin. Transgenic calluses were obtained at a frequency of up to 30% from all the explants tested. However, transgenic shoots were obtained only from the hypocotyl of plantlets derived from pollen embryoids. Transformation was confirmed by the ability of leaf segments to produce kanamycin resistant calluses, -glucuronidase histochemical and flurometric assays, polymerase chain reaction and Southern blot analysis. The results show that pollen embryoid-derived explants may be an alternative source for both efficient transformation and regeneration of transgenic plants in recalcitrant species.     

<Emphasis Type="Italic">MICA</Emphasis> response to gliadin in intestinal mucosa from celiac patients

MHC class I chain-related gene A (MICA), a putative independent susceptibility gene in autoimmune diseases, encodes a surface protein present in epithelial cells that binds to NKG2D, an activating receptor of NK, and T cells, and could function as a stress-inducible activator of the innate immune response. There is no evidence of a long-term implication of MICA in the celiac autoimmune process. However, it could be that gliadin activation of MICA occurs only during the initial stages of the disease. In order to determine whether MICA is activated in response to gliadin in patients with celiac disease (CD), small intestinal mucosa biopsy samples from ten long-standing celiac patients on a gluten-free diet and from five non-celiac individuals were incubated with and without gliadin for 4 h. Total RNA was purified and MICA, IFNG and NKG2D mRNA were quantified by fluorescent real-time RT-PCR. Expression levels were calculated relative to GAPDH. MICA expression was detected in both patients and controls, but incubation with gliadin induced a strong increase in samples from the treated CD group compared with the non-CD controls (P=0.028), while no differences were observed for IFNG or NKG2D mRNA levels. The gliadin-provoked over-expression of MICA in normalized tissues from CD patients suggests a role for this stress-induced activator of the immune response in the early stages of organ-specific autoimmune destruction, probably preceding the onset of inflammation.     

<Emphasis Type="Italic">Agrobacterium</Emphasis>-mediated genetic transformation and development of herbicide-resistant sugarcane (<Emphasis Type="Italic">Saccharum</Emphasis> species hybrids) using axillary buds

Direct regeneration from explants without an intervening callus phase has several advantages, including production of true type progenies. Axillary bud explants from 6-month-old sugarcane cultivars Co92061 and Co671 were co-cultivated with Agrobacterium strains LBA4404 and EHA105 that harboured a binary vector pGA492 carrying neomycin phosphotransferase II, phosphinothricin acetyltransferase (bar) and an intron containing -glucuronidase (gus-intron) genes in the T-DNA region. A comparison of kanamycin, geneticin and phosphinothricin (PPT) selection showed that PPT (5.0 mg l^–1) was the most effective selection agent for axillary bud transformation. Repeated proliferation of shoots in the selection medium eliminated chimeric transformants. Transgenic plants were generated in three different steps: (1) production of putative primary transgenic shoots in Murashige-Skoog (MS) liquid medium with 3.0 mg l^–1 6-benzyladenine (BA) and 5.0 mg l^–1 PPT, (2) production of secondary transgenic shoots from the primary transgenic shoots by growing them in MS liquid medium with 2.0 mg l^–1 BA, 1.0 mg l^–1 kinetin (Kin), 0.5 mg l^–1 -napthaleneacetic acid (NAA) and 5.0 mg l^–1 PPT for 3 weeks, followed by five more cycles of shoot proliferation and selection under same conditions, and (3) rooting of transgenic shoots on half-strength MS liquid medium with 0.5 mg l^–1 NAA and 5.0 mg l^–1 PPT. About 90% of the regenerated shoots rooted and 80% of them survived during acclimatisation in greenhouse. Transformation was confirmed by a histochemical -glucuronidase (GUS) assay and PCR amplification of the bar gene. Southern blot analysis indicated integration of the bar gene in two genomic locations in the majority of transformants. Transformation efficiency was influenced by the co-cultivation period, addition of the phenolic compound acetosyringone and the Agrobacterium strain. A 3-day co-cultivation with 50 M acetosyringone considerably increased the transformation efficiency. Agrobacterium strain EHA105 was more effective, producing twice the number of transgenic shoots than strain LBA4404 in both Co92061 and Co671 cultivars. Depending on the variety, 50–60% of the transgenic plants sprayed with BASTA (60 g l^–1 glufosinate) grew without any herbicide damage under greenhouse conditions. These results show that, with this protocol, generation and multiplication of transgenic shoots can be achieved in about 5 months with transformation efficiencies as high as 50%.Abbreviations BA 6-Benzyladenine - CaMV Cauliflower mosaic virus - GUS -Glucuronidase - Kin Kinetin - NAA -Naphthaleneacetic acid - Nos Nopaline synthase - nptII Neomycin phosphotransferase II - PCR Polymerase chain reaction - PPT Phosphinothricin - YEP Yeast extract and peptone     

<Emphasis Type="Italic">In vitro</Emphasis> propagation of the genus <Emphasis Type="Italic">Clivia</Emphasis>

We have developed a protocol for the in vitro propagation of the genus Clivia. Shoots were regenerated when fragments of the peduncle-pedicel junction (PP junction) from young inflorescences were used as explants. The optimal media for PP junction were Murashige and Skoog (MS)-based medium containing 10 M of 6-benzyladenine (BA) and 10 M of 2,4-dichlorophenoxyacetic acid (2,4-D) or MS supplemented with 5 M BA, 10 M -naphthaleneacetic acid (NAA), 250 mg l^-1 glutamine and 500 mg l^–1 casein hydrolysate and their usage depended on the breeding lines. Multiplication from initiations and in vitro seedlings was the best when the explants were cut longitudinally through the meristem and placed on MS plus 44 M BA. Plantlets were transferred on to hormone -free MS medium with charcoal for rooting.     

Complexity of phenotypes and symbiotic behaviour of <Emphasis Type="Italic">Rhizobium leguminosarum</Emphasis> biovar <Emphasis Type="Italic">trifolii</Emphasis> exopolysaccharide mutants

Quantitative in vitro antibacterial activities, i.e., minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs), of 12 -lactam antibiotics against Agrobacterium tumefaciens strains LBA4404 and EHA101 were examined, in order to identify antibiotics effective in eliminating the bacteria in Agrobacterium-mediated plant genetic transformation. The antibacterial activities of -lactams tested against strain EHA101 were equal to or less than those tested against strain LBA4404. Cefotaxime, cefbuperazone, and meropenem had high activities against strain LBA4404 (MBC <1 mg l^–1). Against strain EHA101, however, only meropenem showed activity comparable to that against strain LBA4404. The production of -lactamase was observed only in strain EHA101.Abbreviations CFU Colony-forming unit - MBC Minimum bactericidal concentration - MIC Minimum inhibitory concentration - PBP Penicillin-binding protein     

Transformation of artemisinin by<Emphasis Type="Italic"> Cunninghamella elegans</Emphasis>

Semi-synthetic derivatives of the anti-malarial drug artemisinin hold great promise in the search for an effective and economical treatment of chloroquine-resistant forms of malaria. Unfortunately, synthetic functionalization of the artemisinin skeleton is often tedious and/or impractical. We seek to utilize 7-hydroxyartemisinin, obtained from microbial transformation, as a semi-synthetic precursor for the synthesis of novel 7-substituted artemisinin anti-malarial agents. Here we employ liquid cultures of Cunninghamella elegans as a means for the rational and economical bioconversion of artemisinin to 7-hydroxyartemisinin in 78.6% yield. In addition, there were three other bioconversion products: 7-hydroxy-9-artemisinin (6.0%), 4-hydroxy-1-deoxoartemisinin (5.4%), and 6-hydroxyartemisinin (6.5%).     

Antifibrotic effects of <Emphasis Type="Italic">Salvia miltiorrhiza </Emphasis>on dimethylnitrosamine-intoxicated rats

Excessive oxidative stress is implicated in hepatic fibrogenesis. Extracts of Salvia miltiorrhiza (Sm) have been shown to protect cells against oxidative stress. In this study we investigated the in vitro and in vivo effects of Sm on hepatic fibrosis. A cell line of rat hepatic stellate cells (HSC-T6) was stimulated with transforming growth factor-1 (TGF-1). The inhibitory effects of Sm (50~400 g/ml) on TGF-1-induced -smooth muscle actin (-SMA) secretion and the mRNA expressions of fibrosis-related genes, including -SMA, connective tissue growth factor (CTGF), and tissue inhibitor of metalloproteinase-1 (TIMP-1), were assessed. Fibrosis was induced by dimethylnitrosamine (DMN) administration in rats. DMN-treated rats were randomly assigned to 1 of 4 groups: saline, Sm (20 mg/kg), Sm (100 mg/kg), or silymarin (100 mg/kg), each given by gavage twice daily for 5 weeks starting from the onset of DMN administration. Sm (200 and 400 g/ml) significantly inhibited TGF-1-stimulated -SMA secretion and the mRNA expressions of -SMA, CTGF, and TIMP-1 in HSC-T6 cells. Fibrosis scores of livers from DMN-treated rats with either a low (1.8 ± 0.2) or high (1.8 ± 0.1) dose of Sm, or silymarin (1.4 ± 0.2) were significantly reduced in comparison with DMN-treated rats receiving saline (3.1 ± 0.1). Hepatic collagen contents were also significantly reduced by either Sm or silymarin treatment. The mRNA expression levels of -SMA, TGF-1, and procollagen I were all attenuated in Sm- and silymarin-treated rats. Moreover, levels of plasma aspartate transaminase activities were reduced by Sm and silymarin treatment. In conclusion, our results show that Sm exerted antifibrotic effects in both HSC-T6 cells and in rats with DMN-induced fibrosis.     

Structure,regulation, and function of <Emphasis Type="Italic">micro1</Emphasis> in the sea urchin <Emphasis Type="Italic">Hemicentrotus pulcherrimus</Emphasis>

The animal-vegetal axis of sea urchin embryos is morphologically apparent at the 16-cell stage, when the mesomeres, macromeres, and micromeres align along it. At this stage, the micromere is the only autonomously specified blastomere that functions as a signaling center. We used a subtraction PCR survey to identify the homeobox gene micro1 as a micromere-specific gene. The micro1 gene is a representative of a novel family of paired-like class homeobox genes, along with PlHbox12 from Paracentrotus lividus and pmar1 from Strongylocentrotus purpuratus. In the present study, we showed that micro1 is a multicopy gene with six or more polymorphic loci, at least three of which are clustered in a 30-kb region of the genome. The micro1 gene is transiently expressed during early cleavage stages in the micromere. Recently, nuclear -catenin was shown to be essential for the specification of vegetal cell fates, including micromeres, and the temporal and spatial coincidence of micro1 expression with the nuclear entry of -catenin is highly suggestive. We demonstrated that micro1 is a direct target of -catenin. In addition, we showed that micro1 is necessary and sufficient for micromere specification. These observations on the structure, regulation, and function of micro1 lead to the conclusion that micro1 and pmar1 (and potentially PlHbox12) are orthologous.     

Comparative Genomic Analysis of the <Emphasis Type="Italic">sigB</Emphasis> Operon in <Emphasis Type="Italic">Listeria monocytogenes</Emphasis> and in Other Gram-Positive Bacteria

The stress-responsive, alternative sigma factor ^B has been described in members of three Gram-positive genera, Bacillus, Listeria, and Staphylococcus. In these bacteria, ^B appears to play an important role in facilitating rapid adaptation to and survival in stressful environments. ^B activity is regulated through a complex system of phosphatases and kinases encoded by rsb (regulator of sigma B) genes. We describe the sigB operon structure for the facultative intracellular pathogen Listeria monocytogenes and apply this sequence as well as other previously described sigB operon sequences to probe the evolution and functional conservation of the ^B stress response system among different Gram-positive bacteria. While ^B as well as two Rsbs (RsbS and RsbT) are highly conserved (73%, 84%, and 79% average amino acid [aa] identities, respectively), the predicted aa sequences of the other Rsb proteins showed less conservation (62–71% aa identities). Furthermore, the sigB operon structure varies among bacterial species. Bacterial species differ in the numbers and identities of rsb genes encoded in their genomes. We thus conclude that the ^B stress-response system as represented by the sigB operon has diverged in both its overall components as well as in the sequences of its individual proteins, even among closely related bacterial species. Differential evolution of this stress response system among various genera may represent a strategy that enables bacteria to adapt cellular response and survival systems to a variety of stress conditions.     

Development of high frequency multiple shoot formation in Persian clover (<Emphasis Type="Italic">Trifolium resupinatum</Emphasis> L.)

An efficient and reliable micropropagation system for Persian clover (Trifolium resupinatum L.) was developed using different explants and media. Node, hypocotyl and cotyledonary node explants were cultured on Murashige and Skoog (MS) medium supplemented with combinations of either 6-benzyladenine (BA) and indole-3-butyric acid (IBA) or BA, Kinetin (KIN) and IBA. Direct multiple shoots developed within 6weeks in all explants in most media tested. The best shoot multiplication capacity was obtained from cotyledonary node explants on MS medium containing 7.1M BA and 1M IBA or 14.1M BA and 1M IBA. Elongated shoots were rooted on either MS medium alone or combination with different concentrations of indole-3-butyric acid (IBA), indole-3-acetic acid (IAA) and -naphthaleneacetic acid (NAA). High rooting was achieved in half strength MS medium containing 8M IBA.     

Expression of<Emphasis Type="Italic"> ENOD40</Emphasis> during tomato plant development

In legumes, ENOD40 expression is increased upon interaction of plants with rhizobia. Little is known of the expression pattern of ENOD40 during other stages of the plant life cycle. Studies of ENOD40 expression in non-legume development may give an indication of the function of the gene. To investigate the ENOD40 expression pattern during plant development, a fusion between the -glucuronidase (GUS) reporter gene and 150 bp of the 5 untranslated region plus 3,000 bp of 5 untranscribed tomato ENOD40 sequence was constructed and introduced into Lycopersicon esculentum Miller. Based on the observed GUS expression patterns in transgenic tomato we speculate that ENOD40 in tomato has a role in counteracting ethylene-provoked responses.Abbreviations GUS -glucuronidase - FISH fluorescence in situ hybridisation - RACE rapid amplification of cDNA ends - RFLC restriction fragment length polymorphism     

<Emphasis Type="Italic">In vitro</Emphasis> regeneration of <Emphasis Type="Italic">Bambusa balcooa</Emphasis> Roxb.: Factors affecting changes of morphogenetic competence in the axillary buds

Axillary buds from field-grown culms of Bambusa balcooa were used as explants to induce multiple shoots in liquid Murashige and Skoogs (MS) medium supplemented with 11.25 M of 6-benzylaminopurine (BAP) and 4.5 M kinetin (Kn). A clump of at least 3 shoots was used for root induction in half strength MS medium with 1.0 M of 3-indolebutyric acid (IBA). Morphogenetic competence of the axillary buds varied widely in different months of two consecutive calendar years. The highest morphogenetic potentials were observed in October. The major problem encountered was presence of systemic fungal contaminants. Perhaps, rainfall positively contributed to induce morphogenetic competence. A moderately high phenolic content of the nodal explant was also detrimental for in vitro morphogenesis. The morphogenetic competence of B. balcooa correlated with the season in which the explants were excised from the natural stands. To the best of our knowledge this is the first report on in vitro regeneration of B. balcooa from mature field-grown axillary buds.     

The role of dilution and differential predation in brood adoptions of the Midas cichlid (<Emphasis Type="Italic">Amphilophus xiloaensis</Emphasis>)

Laboratory experiments were conducted to determine if the addition of conspecific foreign fry affects the survival of host fry in the Midas cichlid, Amphilophus xiloaensis. The study consisted of two separate experiments: (1) adoption treatments simulated by adding 75 foreign fry to a host brood containing 150 fry and parents (10 trials where host fry were larger, 10 trials where foreign fry were larger); (2) control treatments in which no foreign fry were added to a host brood containing 150 fry and parents (20 trials). Predation was imposed by introducing three bigmouth sleepers (Gobiomorus dormitor). No significant differences were found between the survival of host, foreign, and control fry after 24 h. Survival was significantly affected by fry size, leading to differential predation on smaller fry. Mean predation rate increased proportionally with brood size, therefore the addition of conspecific foreign fry did not result in dilution of the host brood.