In the surf zone: Reproductive strategy of the calico surfperch (Amphistichus koelzi) in a comparative context

We examined the reproductive life history of calico surfperch (Amphistichus koelzi), including mating season, pregnancy, gestation and multiple paternity utilizing restriction site-associated DNA sequencing. Furthermore, we compared the mating season of calico with barred (Amphistichus argenteus), walleye (Hyperprosopon argenteum) and silver (Hyperprosopon ellipticum) surfperches to determine if the timing of reproduction is divergent within and between the genera. In calico surfperch, the mating season occurs from October to November, and females gestate from December to May. All broods exhibit multiple paternity with a range of four to seven sires per brood. The mating season of calico overlaps completely with barred surfperch; however, barred surfperches have a protracted mating season which extends until the beginning of December, which may be due to differences in reproductive strategy such as size at first reproduction. In the genus, the Hyperprosopon mating season begins earlier than Amphistichus, with divergence in the onset of mating between Hyperprosopon congeners of approximately 1 month.     

Multiple paternity is a shared reproductive strategy in the live‐bearing surfperches (Embiotocidae) that may be associated with female fitness

According to Bateman's principle, female fecundity is limited relative to males, setting the expectation that males should be promiscuous, while females should be choosy and select fewer mates. However, several surfperches (Embiotocidae) exhibit multiple paternity within broods indicating that females mate with multiple males throughout the mating season. Previous studies found no correlation between mating success and reproductive success (i.e., a Bateman gradient). However, by including samples from a broader range of reproductive size classes, we found evidence of a Bateman gradient in two surfperch species from distinct embiotocid clades. Using microsatellite analyses, we found that 100% of the spotfin surfperch families sampled exhibit multiple paternity (Hyperprosopon anale, the basal taxon from the only clade that has not previously been investigated) indicating that this tactic is a shared reproductive strategy among surfperches. Further, we detected evidence for a Bateman gradient in H. anale; however, this result was not significant after correction for biases. Similarly, we found evidence for multiple paternity in 83% of the shiner surfperch families (Cymatogaster aggregata) sampled. When we combine these data with a previous study on the same species, representing a larger range of reproductive size classes and associated brood sizes, we detect a Bateman gradient in shiner surfperch for the first time that remains significant after several conservative tests for bias correction. These results indicate that sexual selection is likely complex in this system, with the potential for conflicting optima between sexes, and imply a positive shift in fertility (i.e., increasing number) and reproductive tactic with respect to the mating system and number of sires throughout the reproductive life history of females. We argue that the complex reproductive natural history of surfperches is characterized by several traits that may be associated with cryptic female choice, including protracted oogenesis, uterine sac complexity, and sperm storage.     

Visual pigments and optical habitats of surfperch (Embiotocidae) in the California kelp forest

We studied the optical microhabitat use and visual pigment variation among a group of closely related teleosts (surfperch: Embiotocidae) living along the nearshore central California coast. We employed a diver-operated spectroradiometer to record the optical microhabitat use of eight surfperch species in Monterey Bay. and microspectrophotometry to measure visual pigment absorbance for nine surfperch species. Species were dichromatic with mixtures of A1- and A2-based visual pigments exhibiting extensive maximum absorbance (lambda(max)) variation across species: 455-482 nm for SWS cones and 527-546 nm for LWS cones. Interspecific variation in sidewelling irradiance measurements (mean lambdaFmaxs) significantly accounted for 63% of the variation in surfperch LWS visual pigments and 83% of the interspecific variation in SWS visual pigments using a phylogenetically-corrected regression technique. Optimality models for maximizing relative photon capture of background radiance demonstrate that the LWS cone lambda(max) values are tuned for maximizing photon capture of the species-specific horizontal visual field, while the SWS cone lambda(max), are well offset from the dominant background radiance. This study is one of the first to demonstrate species-specific differences in habitat usage at microhabitat scales accounting for differences in photoreceptor peak absorbance among closely related, sympatric species.     

Osteocranial development in the viviparous surfperch Amphistichus argenteus (pisces: Embiotocidae)

The development of the cranial and branchial skeleton of the surfperch Amphistichus argenteus, a member of the family Embiotocidae, is described, and phylogenetic and functional aspects of the skull development of this species are discussed. The earliest bones to appear are those dermal elements of the branchial skeleton involved with feeding, and the bones, both dermal and endochondral, located in the basicranial region of the neurocranium. These are followed by dermal bones associated with the lateral line system and finally by the remainder of the bones of the branchial skeleton and the cartilaginous bones of the otic capsules. The last bone to develop is the ethmoid.     

Phylogeny of bird-grasshopper subfamily Cyrtacanthacridinae (Orthoptera: Acrididae) and the evolution of locust phase polyphenism

Locust phase polyphenism is an extreme form of density-dependent phenotypic plasticity in which solitary and cryptic grasshoppers can transform into gregarious and conspicuous locusts in response to an increase in local population density. We investigated the evolution of this complex phenotypic plasticity in a phylogenetic framework using a morphological phylogeny of Cyrtacanthacridinae, which contains some of the most important locust species, and a comprehensive literature review on the biology and ecology of all known members of the subfamily. A phylogenetic analysis based on 71 morphological characters yielded a well-resolved tree and found that locust phase polyphenism evolved multiple times within the subfamily. The literature review demonstrated that many cyrtacanthacridine species, both locust and sedentary, are capable of expressing density-dependent color plasticity. When this color plasticity was divided into two smaller components, background coloration and development of black pigmentation, and when these plastic traits were optimized on to the phylogeny, we found that the physiological mechanisms underlying this plasticity were plesiomorphic for the subfamily. We also found that different locust species in Cyrtacanthacridinae express both similarities and differences in their locust phase polyphenism. Because locust phase polyphenism is a complex syndrome consisting of numerous plastic traits, we treat it as a composite character and dissected it into smaller components. The similarities among locust species could be attributed to shared ancestry and the differences could be attributed to the certain components of locust phase polyphenism evolving at different rates.
© The Willi Hennig Society 2007.     

The name of the father: conflict between Louis and Alexander Agassiz and the Embiotoca surfperch radiation

The surfperch genus Embiotoca currently comprises two species, Embiotoca jacksoni , the black surfperch, and Embiotoca lateralis , the striped surfperch. Originally, however, Louis Agassiz described a third species in the genus Embiotoca , the rainbow surfperch, Embiotoca caryi . This latter name was changed by Louis' son, Alexander, to Hypsurus caryi , a name that remains valid. In this study, new molecular data (3545 bp of DNA from four mitochondrial and two nuclear DNA regions) indicated that the rainbow surfperch should be retained within the genus Embiotoca , a result consistent with recent morphological data. Adaptive radiation combined with sexual selection resulting in rapid morphological changes in the rainbow surfperch may have contributed to the conflicting position of this species.     

Pseudomonas aeruginosa-Candida albicans Interactions: Localization and Fungal Toxicity of a Phenazine Derivative

Phenazines are redox-active small molecules that play significant roles in the interactions between pseudomonads and diverse eukaryotes, including fungi. When Pseudomonas aeruginosa and Candida albicans were cocultured on solid medium, a red pigmentation developed that was dependent on P. aeruginosa phenazine biosynthetic genes. Through a genetic screen in combination with biochemical experiments, it was found that a P. aeruginosa-produced precursor to pyocyanin, proposed to be 5-methyl-phenazinium-1-carboxylate (5MPCA), was necessary for the formation of the red pigmentation. The 5MPCA-derived pigment was found to accumulate exclusively within fungal cells, where it retained the ability to be reversibly oxidized and reduced, and its detection correlated with decreased fungal viability. Pyocyanin was not required for pigment formation or fungal killing. Spectral analyses showed that the partially purified pigment from within the fungus differed from aeruginosins A and B, two red phenazine derivatives formed late in P. aeruginosa cultures. The red pigment isolated from C. albicans that had been cocultured with P. aeruginosa was heterogeneous and difficult to release from fungal cells, suggesting its modification within the fungus. These findings suggest that intracellular targeting of some phenazines may contribute to their toxicity and that this strategy could be useful in developing new antifungals.     

Apd1(+), a Gene Required for Red Pigment Formation in Ade6 Mutants of Schizosaccharomyces Pombe, Encodes an Enzyme Required for Glutathione Biosynthesis: A Role for Glutathione and a Glutathione-Conjugate Pump

Mutants in the adenine biosynthetic pathway of yeasts (ade1 and ade2 of Saccharomyces cerevisiae, ade6 and ade7 of Schizosaccharomyces pombe) accumulate an intense red pigment in their vacuoles when grown under adenine-limiting conditions. The precise events that determine the formation of the pigment are however, still unknown. We have begun a genetic investigation into the nature and cause of pigmentation of ade6 mutants of S. pombe and have discovered that one of these pigmentation defective mutants, apd1 (adenine pigmentation defective), is a strict glutathione auxotroph. The gene apd1(+) was found to encode the first enzyme in glutathione biosynthesis, γ-glutamylcysteine synthetase, gcs1(+). This gene when expressed in the mutant could confer both glutathione prototrophy and the characteristic red pigmentation, and disruption of the gene led to a loss in both phenotypes. Supplementation of glutathione in the medium, however, could only restore growth but not the pigmentation because the cells were unable to achieve sufficient intracellular levels of glutathione. Disruption of the second enzyme in glutathione biosynthesis, glutathione synthetase, gsh2(+), also led to glutathione auxotrophy, but only a partial defect in pigment formation. A reevaluation of the major amino acids previously reported to be present in the pigment indicated that the pigment is probably a glutathione conjugate. The ability of vanadate to inhibit pigment formation indicated that the conjugate was transported into the vacuole through a glutathione-conjugate pump. This was further confirmed using strains of S. cerevisiae bearing disruptions in the recently identified glutathione-conjugate pump, YCF1, where a significant reduction in pigment formation was observed. The pump of S. pombe is distinct from the previously identified vacuolar pump, hmt1p, for transporting cadystin peptides into vacuoles of S. pombe.     

Color changes in Halyomorpha brevis (Heteroptera: Pentatomidae) correlated with distribution of pteridines: regulation by environmental and physiological factors

Halyomorpha brevis (Heteroptera: Pentatomidae) produces adults with different color patterns, most noticeable in the sternum. The color, ranging from ivory to red, depends on the extent of the accumulation of red pigment. The present work investigated the effects of photoperiod, temperature and aging on the pigmentation. The red pigment was identified as erythropterin by comparing the Rf with standard pteridines in paper chromatography in three solvent systems. Erythropterin was found in all organs, red or light red. Uric acid was detected prominently in ivory or light red sternum. A negative correlation was found between the extent of red pigmentation and that of uric acid content. The relative proportion of males and females with a red sternum progressively increased as they aged from day 0 to day 20 after adult emergence, particularly in males reared under a long day (non-diapausing). In males, an age-dependent decrease in red pigmentation was observed in the gastric ceca and tracheae. The sternum was lighter in short-day adults (diapausing) than that in non-diapausing adults at the same age, and the latter never achieved the intense red color. The possible functions of pteridines are discussed.     

Tissue-specific patterns of a maize Myb transcription factor are epigenetically regulated

The maize p1 gene encodes a Myb-homologous regulator of red pigment biosynthesis. To investigate the tissue-specific regulation of the p1 gene, maize plants were transformed with constructs combining promoter and cDNA sequences of two alleles which differ in pigmentation patterns: P1-wr (white pericarp/red cob) and P1-rr (red pericarp/red cob). Surprisingly, all promoter/cDNA combinations produced transgenic plants with red pericarp and red cob (RR pattern), indicating that the P1-wr promoter and encoded protein can function in pericarp. Some of the RR patterned transgenic plants produced progeny plants with white pericarp and red cob (WR pattern), and this switch in tissue-specificity correlated with increased transgene methylation. A similar inverse correlation between pericarp pigmentation and DNA methylation was observed for certain natural p1 alleles, which have a gene structure characteristic of standard P1-wr alleles, but which confer red pericarp pigmentation and are consistently less methylated than standard P1-wr alleles. Although we cannot rule out the possible existence of tissue-specific regulatory elements within the p1 non-coding sequences or flanking regions, the data from transgenic and natural alleles suggest that the tissue-specific pigmentation pattern characteristic of the P1-wr phenotype is epigenetically controlled.     

Genetic versus environmental influence on pigment variation in the ephippia of Daphnia pulicaria

1. The dormant eggs of Daphnia (Crustacea: cladocera) are encased in a protective, chitonous casing known as an ephippium. Ephippia are pigmented with melanin, and the degree of pigmentation ranges from transparent to opaque. Variation in pigmentation exists within and across populations and species, raising questions about the factors that influence the natural distribution of pigmentation. 2. We used image analysis to quantify pigmentation in ephippial casings of Daphnia pulicaria that were produced both in the field and in the laboratory. The percentage of the surface area of ephippia that is darkly pigmented ranged from 0.5 to 99.5%. The range, mean and variance of ephippial pigmentation varied across our 11 study lakes. 3. Laboratory experiments compared clonal variation (five clones/lake) and population variation (five lakes) at three temperatures (15 °C, 20 °C and 25 °C). The degree of pigment variation between clones was much greater than pigment variation between temperatures, indicating that there is a genetic component to pigmentation in the ephippia which is stronger than the effect of temperature. 4. Comparisons of pigment levels and lake characteristics were used to identify physical and biological factors associated with ephippial pigmentation. Investment in ephippial production was the strongest predictor with darker ephippia occurring more often in lakes with the highest ephippial production.     

Scrota1 melanins in bats (Chiroptera): description, distribution and function

Several species of bats contain pigment granules within the scrotal skin, tunica vaginalis, or tunica albuginea surrounding the testis and/or epididymis. Seventy-two species of bats, representing 49 genera were examined for the presence of such pigmentation. Histological, chemical and spectrophotometric tests were performed and confirmed the pigment as melanin. Melanin was found only in the families Pteropidae, Megadermatidae, Myzopodidae and Vespertilionidae. A strong correlation exists between scrotal pigmentation and roosting in locations where the bats are exposed to solar radiation. Melanin pigmentation in the scrotal region appears to be an adaption protecting male germinal tissue from the harmful effects of ultraviolet radiation. In one species, Laoiu frons , melanin deposited within the scrotal skin appears to have a social/reproductive communication function.     

Variegated expression and delayed retinal pigmentation during development in transgenic mice with a deletion in the locus control region of the tyrosinase gene

Deletion of the tyrosinase locus control region (LCR) in transgenic mice results in variegated expression in the skin. Here we investigate the pigmentation pattern of other tissues that express tyrosinase: iris, choroid, and retina in the same animals. A mosaic distribution of pigmentation appears in the iris and choroid. Interestingly, a markedly different mosaic pattern is found in the retina, where central areas contain little or no melanin while pigmentation rises to normal levels towards periphery. Further, there is a temporal delay in the initiation and accumulation of pigment in retinal pigmented epithelium (RPE) cells during development, and patterns of adult retinal melanisation in these mice appear arrested at a stage found in early embryogenesis in wild-type mice. These results demonstrate that the tyrosinase LCR is needed for the correct establishment and maintenance of this expression domain throughout development, but particularly during the later stages of retinal melanisation.     

Gene loss and parallel evolution contribute to species difference in flower color

Although the importance of regulatory and functional sequence evolution in generating species differences has been studied to some extent, much less is known about the role of other types of genomic changes, such as fluctuation in gene copy number. Here, we apply analyses of gene function and expression of anthocyanin pigment pathway genes, as well as cosegregation analyses in backcross populations, to examine the genetic changes involved in the shift from blue to red flowers in Andean Iochroma (Solanaceae). We demonstrate that deletion of a gene coding for an anthocyanin pathway enzyme was necessary for the transition to red floral pigmentation. The downregulation of a second pathway gene was also necessary for the novel flower color, and this regulatory pattern parallels the genetic change in the two other red-flowered species in the sister family Convolvulaceae in which flower color change has been examined genetically. Finally, we document a shift in enzymatic function at a third locus, but the importance of this change in the transition to red flowers depends on the exact order with which the three changes occurred. This study shows that gene inactivation or loss can be involved in the origin of phenotypic differences between species, thereby restricting the possibility of reversion to the ancestral state. It also demonstrates that parallel evolution of red flowers in three different species occurs via a common developmental/regulatory change but by mutations in different genes.     

Realized evolvability: quantifying phenotypic evolution in a Drosophila clade

Understanding the evolutionary potential of morphological evolution is still a major problem in evolutionary biology. In this study, we tried to quantify the amount of variation of different traits among species of a Drosophila clade reared under standard conditions. Nineteen different traits have been measured on nine species of the same clade, the Neotropical saltans group of Drosophila. Measured traits can be distributed into five categories: size‐traits (wing and thorax), shape indices (ratios among the size traits), number of sternopleural bristles on the thorax, number of abdominal bristles on successive sternites, and dorsal pigmentation of abdomen. All species are of medium size with a generally dark pigmentation. A remarkable feature is the presence of numerous bristles on the 6th sternite of the males, while this segment is bare in other Drosophila species. A multivariate analysis revealed that it was possible to discriminate all the investigated species by using the complete set of measured traits. For each trait, phenotypic variability was investigated at the within‐ and between‐species levels. As a rule, the interspecific coefficient of variation (CV) was much greater than the within species CV, and it is proposed to call it realized evolvability. All possible correlations were calculated between traits across species, providing many unexpected results. Size traits were highly correlated among them, but not correlated with shape indices. Abdominal traits (bristles and pigmentation) were correlated, but often in opposite directions, with thoracic shape indices. Tergite pigmentation was negatively correlated with bristle number on sternite. For the moment, most of the correlations cannot be explained by developmental processes or parallel selective pressures. Nonetheless, mapping the evolution of the two characters on a molecular phylogeny of the studied species revealed two opposite phylogenetic trends for abdominal pigmentation and setation, respectively. Our data suggest a need for similar studies in other well‐defined Drosophila clades.     

Contrasting effects of giant kelp on dynamics of surfperch populations

Summary The effect of giant kelp, Macrocystis pyrifera, on the population dynamics of two temperate reef fishes, striped surfperch (Embiotoca lateralis) and black surfperch (E. jacksoni), was examined. Based on an understanding of how particular reef resources influence abundances of the surfperch and of the effect of giant kelp on those resources, we anticipated that Macrocystis would adversely affect populations of striped surfperch but would enhance those of black surfperch. The natural establishment of giant kelp at sites at Santa Cruz Island, California, resulted in the predicted dynamical responses of surfperch. Abundances of striped surfperch declined rapidly when and where dense forests of giant kelp appeared, but showed little change where Macrocystis was continuously absent over the 8 y period of study. Abundances of adult black surperch, which increased following the appearance of giant kelp, were lagged by >1 y because the dynamical response involved enhanced local recruitment. No change in abundance of black surfperch populations was evident at areas without giant kelp.The mechanism by which giant kelp altered the dynamics of the surfperch involved modification of the assemblage of understory algae used by surfperch as foraging microhabitat. Foliose algae (including Gelidium robustum) were much reduced and turf was greatly enhanced following the appearance of Macrocystis; these two benthic substrata are the favored foraging microhabitat for striped surfperch and black surfperch respectively. Populations of both surfperch species tracked temporal changes in the local availability of their favored foraging microhabitat. Thus, while neither species used Macrocystis directly, temporal and spatial variation in giant kelp indirectly influenced the dynamics of these fishes by altering their foraging base. These results indicate that the dynamics of striped surfperch and black surfperch were governed to a large degree by density-dependent consumer-resource interactions. The present work underscores the predictive value that arises from a knowledge of the mechanisms by which processes operate.     

Ascidian neural crest-like cells: phylogenetic distribution, relationship to larval complexity, and pigment cell fate

Migratory neural crest-like cells, which express the cell surface antigen HNK-1 and develop into pigment cells, have recently been identified in the ascidian Ecteinascidia turbinata. Here we use HNK-1 expression as a marker to determine whether neural crest-like cells are responsible for pigment development in diverse ascidian species. We surveyed HNK-1 expression and tyrosinase activity in 12 ascidian species, including those with different adult organizations, developmental modes, and larval sizes and complexities. We observed HNK-1 positive cells in every species, although the timing of HNK-1 expression varied according to the extent of larval complexity. HNK-1 expression was initiated during the late tailbud stage in species in which adult features are formed precociously in large complex larvae. In contrast, HNK-1 positive cells did not appear until the swimming tadpole or juvenile stage in species with small simple larvae in which most adult features appear after metamorphosis. Double labeling experiments indicated that HNK-1 and tyrosinase are expressed in the same subset of pigment-forming mesenchymal cells in species with complex or simple larvae. In addition, the absence of HNK-1 and tyrosinase expression in albino morphs of the colonial ascidian Botryllus schlosseri suggested that the major fate of neural crest-like cells is to become pigment cells. The results suggest that ascidian neural crest-like cells and vertebrate neural crest cells had a common origin during chordate evolution and that their primitive function was to generate body pigmentation.     

基于类胡萝卜素着色的鸟类羽色多样性形成机制

人们对动物体色的研究由来已久。作为一类让生物呈现出多变色彩的重要色素, 类胡萝卜素可以在鸟类的羽毛、鸟喙和皮肤等体表组织中沉积, 产生红、橙、黄、粉、紫等颜色。类胡萝卜素不能在鸟类体内合成, 需从食物中摄取, 进而在体内完成吸收、运输、代谢和沉积等一系列过程, 才能用于羽毛着色。与类胡萝卜素着色相关的生理及遗传调控机制一直备受关注, BCO2、SCARB1和CYP2J19等影响类胡萝卜素在鸟类羽毛中着色的关键基因, 推动了对羽色遗传调控机制的深入认识。本文介绍了鸟类可利用类胡萝卜素的主要类型和基本特征, 综述了类胡萝卜素着色相关的生理过程以及调控基因研究的最新进展, 旨在增加对鸟类羽毛中类胡萝卜素着色过程和相关遗传机制的理解。