Two populations of the marine fish Porichthys notatus,one lacking in luciferin essential for bioluminescence

Porichthys notatus is a common benthic fish found along the Pacific coast of North America. It possesses more than 700 small dermal photophores on its head and trunk. When P. notatus collected in Monterey Bay, California, is injected subcutaneously with norepinephrine, the photophores emit a long-lasting luminescence that is readily visible to the dark-adapted eye. The light emission is due to the oxidation of luciferin (substrate) by molecular oxygen, catalyzed by luciferase. In contrast, P. notatus collected in Puget Sound, Washington, is nonluminous, even though the photophores do not differ ultrastructurally from those of the California fish. The inability of the Puget Sound fish to luminesce is due to lack of luciferin in its photophores. Luminescence capability, however, may be induced in the Puget Sound fish by the oral or intraperitoneal administration of a small amount of luciferin from the tiny luminescent marine ostracod crustacean, Vargula hilgendorfii, suggesting that the origin of luciferin in P. notatus may be from the diet. In this study, specimens of P. notatus were collected over the entire known range of the species, between November 1981 and September 1987, and the presence of luciferin in the photophores determined. The results indicate that there are two populations of P. notatus: a luciferin-deficient, nonluminescent population located north of northern California and a luciferin-containing, luminescent population extending south of Cape Mendocino, California, to Baja California, Mexico. At the northern end of the southern population, a mixture of luminescent and nonluminescent P. notatus was found.     

Observations on the comparative morphology and operation of the photogenic tissues of myctophid fishes

Lanternfishes (Myctophidae) often bear not only small primary photophores, but also larger regions of luminous tissue, described as glands or patches. These have a superficial appearance very different to that of the primary photophores, but examination of the tissues of some 14 genera has shown that all the luminous organs are composed of fundamentally similar stacks of photogenic lamellae. The degree of organisation of the lamellae varies in different genera, but the caudal organs and the other larger luminous regions contain much more of this photogenic tissue than do the primary photophores. Some observations on the operation of both primary and caudal organs are described.     

Effect of blue light on early sporophyte development of Saccharina japonica (Phaeophyta)

Growth and photosynthesis in the blade of Saccharina sporophytes are strongly stimulated by blue light. However, little is known about the effect of blue light on the early development and longitudinal photosynthesis profile of Saccharina sporophytes. In this study, S. japonica sporelings were cultured under blue or red light for 8 weeks. Blue light affected longitudinal, tangential cell divisions and tissue differentiation early in sporophyte development. The number of latitudinal cells in the blade under blue light was over fivefold that under red light. In addition, the number of cell layers was higher in the growing point than in the blade under blue light, whereas sporelings grown under red light contained only a single cell layer. Under blue light, the photosynthetic capacities of the growing region, blade and stipe were similar, and the maximum relative electron transport rate was even lower in the growing point than in the blade. The longitudinal photosynthesis profile suggested that blue light stimulated the enzymes participating in light-independent carbon fixation in the growing point and accordingly was less dependent on high light irradiances. Collectively, the results indicated that blue light promotes the early development of S. japonica sporophytes, which was attributed to both photomorphogenetic responses and photosynthetic reactions.     

Diel migration of phytoplankton and spectral light field in the Ría de Vigo (NW Spain)

Diel migration of Mesodinium rubrum, Eutreptiella sp., Scrippsiella trochoidea, Dinophysis acuminata and Ceratium furca throughout a 24 h cycle is described for a stable, well-stratified estuary (Ría de Vigo, NW Spain). Daily changes in light quantity and in spectral light ratios i.e. red:far-red, blue:red, green:red and blue:green have been analysed. The spectral light ratios changed at twilight and around noon at various depths. Some of the downward migrations were well predicted by Stokes' law, while other migrations were faster and deeper than calculated. The coincidence of these movements with abrupt changes in red:far-red, green:red and blue:green light ratios is discussed. Some species are able to migrate through the pycnocline, whereas others do not seem to be able to do so. Several species are present in maximum numbers at depth at night, while others display upward migration independent of light, suggesting the existence of endogenous rhythms. Upward migration at dusk began with dispersal of populations, with renewed aggregation at the sea surface coincident with an increase in the red:far-red ratio at 6 m and the green:red ratio at 6 and 10 m. Based on direct evidence for the control of flagellar mobility by light quality reported by other authors from laboratory studies, it is suggested that, together with other cues, spectral light ratios of different light qualities modulate vertical phytoplanktonic migration. Received: 18 July 1997 / Accepted: 17 October 1997     

Direct male-male competition can facilitate invasion of new colour types in Lake Victoria cichlids

The possibility that disruptive sexual selection alone can cause sympatric speciation is currently a subject of much debate. The initial difficulty for new and rare ornament phenotypes to invade a population, and the stabilisation of the resulting polymorphism in trait and preference make this hypothesis problematic. Recent theoretical work indicates that the invasion is facilitated if males with the new phenotype have an initial advantage in male-male competition. We studied a pair of sympatric incipient species of cichlids from Lake Victoria, in which the red (Pundamilia nyererei) and blue males (P. pundamilia) vigorously defend territories. Other studies suggested that red phenotypes may have repeatedly invaded blue populations in independent episodes of speciation. We hypothesised that red coloration confers an advantage in male-male competition, assisting red phenotypes to invade. To test this hypothesis, we staged contests between red and blue males from a population where the phenotypes are interbreeding morphs or incipient species. We staged contests under both white and green light condition. Green light effectively masks the difference between red and blue coloration. Red males dominated blue males under white light, but their competitive advantage was significantly diminished under green light. Contests were shorter when colour differences were visible. Experience of blue males with red males did not affect the outcome of a contest. The advantage of red over blue in combats may assist the red phenotype to invade blue populations. The apparently stable co-existence of red and blue incipient species in many populations of Lake Victoria cichlids is discussed.Communicated by C. St. Mary     

Luminescence from non-bioluminescent tissues in oceanic cephalopods

Several tissues (e.g. kidney, blood, digestive gland) in oceanic cephalopods which do not exhibit in vivo bioluminescence, luminesce when homogenized in the presence of air or when simply exposed to air in a vial (blood). The source of the luminescence appears to be a luciferin: treatment of kidney homogenates and blood with a photophore extract presumably containing luciferase resulted in a 20-fold increase in light production. Luminescence was also found in the renal fluid, which may be the source of luminescent clouds produced by squids. The variability in luminescence found in some tissues of cephalopods appeared to be related to feeding. Luminescence was also detected in the digestive glands of midwater octopods.     

Light quality effects on carbon metabolism and allocation in Gracilaria verrucosa

Under conditions of new nitrogen availability and low light intensities, light quality (blue, green, or red light) was not found to affect carbon fixation patterns into major metabolic fractions (total ethanol soluble, carbohydrate, and protein) in preconditioned nitrogen enriched or limited apical tips of Gracilaria verrucosa Papenfuss. Within the ethanol soluble fractions of both nitrogen enriched and limited tips, blue light treatment led to a greater percentage of ¹⁴ carbon in amino acids as compared to non-ninhydrin reactive metabolites. A lesser effect was observed with red light, and green light did not appear to stimulate amino acid synthesis appreciably. The low intensity blue light effect in G. verrucosa appears to be an enhancement of nonphotosynthetic carbon incorporation into amino acids, possibly through some form of the urea-ornithine cycle.Harbor Branch Foundation Contribution No. 237     

Presence of coelenterazine in mesopelagic fishes from the Strait of Messina

Coelenterazine, a luciferine, and luciferase activity specific to coelenterazine were detected and assayed in various tissues of mid-water fishes, Argyropelecus hemigymnus, Chauliodus sloani, Myctophum punctatum, Vinciguerria attenuata and Cyclothone braueri. Coelenterazine was found mainly in digestive systems and photophores of these fishes. A large species to species variation was found: extremely high levels of coelenterazine and luciferase were found in the M. punctatum digestive system whereas only a very low level of coelenterazine was detected in C. braueri. Coelenterazine was detected in A. hemigymnus eggs supporting the hypothesis of a maternal transfer of luminous capabilities. Luciferase activity specific to coelenterazine was found in photophores as well as in various other tissues suggesting another (besides light emission) biological function for this enzymatic activity. Distribution of coelenterazine in all tissues of the individuals supports the hypothesis of the dietary acquisition of coelenterazine by these fishes.     

Disruptive counterillumination and its anti-predatory value in the plainfish midshipman Porichthys notatus

The plainfin midshipman Porichthys notatus Girard occurs in nearshore waters off the western coast of North America. We found that the ventrally directed photophores of juvenile laboratory-grown P. notatus function in counterillumination. Their bioluminescence matched downwelling light to obscure the silhouette as viewed from below. P. notatus did not obligatorily counterilluminate at all times in appropriate light. A hydrodynamic stimulus, in addition to appropriate downwelling light, was required to induce counterillumination. This is perhaps an adaptation to conserve its Vargula-type luciferin, which is obtained from its diet. The angular distribution of light produced by P. notatus approximated that typical of downwelling light in the ocean. There was a direct relationship between downwelling irradiance and the maximum intensity of P. notatus luminescence. Insufficient light was produced to replace the light blocked by the fish under lighting conditions typical of the natural environment. The luminescence was, however, effective in eliminating the silhouette of P. notatus as observed with an image-intensifying camera and by dark-adapted human observers. Consequently, the effectiveness of counterillumination probably originates in part from the disruptive pattern of the luminous photophores. P. notatus from the Puget Sound population, which lacks a luciferin source and is non-luminous, displayed counterillumination behavior when its luminescent system was activated by force-feeding the fish with dried Vargula hilgendorfi. Experiments using adult P. notatus as predators on a mixed population of non-luminous (Puget Sound) and luminous (Santa Barbara Channel) juvenile P. notatus revealed that under conditions of dim overhead illumination non-luminous P. notatus were preyed upon at twice the rate of luminous individuals. This is the first experimental evidence suggesting that counterillumination is effective as an anti-predatory strategy. Received: 25 August 1998 / Accepted: 25 March 1999     

Correlation of bioluminescence emissions with ventral photophores in the mesopelagic squidAbralia veranyi (Cephalopoda: Enoploteuthidae)

Specimens of the squidAbralia veranyi were collected off the Bahamas in 1989. The bioluminescence of the ventral photophores was recorded on videotape at 11 to 12°C and 24°C, in conjunction with measurements of the spectral emission at the same temperatures. At 11 °C, the spectrum was unimodal, peaking at 490 nm with a narrow bandwidth. At the higher temperature a shoulder at about 440 nm appeared in the emission spectrum. The short, bright flashes from the subocular photophores had a broader bandwidth and a shorter wavelength emission maximum (475 nm) than that of the ventral photophores. Video recordings at the two temperatures showed no changes in either the identities of the luminescing photophores or their relative intensities. One structurally distinct type of photophore was not illuminated. We conclude that the observed spectral changes were produced within one group of photophores, and that recruitment of the unilluminated photophores would produce an additional spectral component, previously reported from another species ofAbralia (A. trigonura).     

Reproduction,growth and photosynthesis of gametophytes of Laminaria saccharina grown in blue and red light

The induction of reproductive activity by blue light in female gametophytes of the brown alga Lamnaria saccharina has been investigated and related to other effects of red and blue light on these plants. Although germination of zoo-spores is slightly delayed in red light, female gametophytes grow at similar rates in blue and red light of the same quantum irradiance up to an age of 8 to 10 days, when plants in blue light begin to form eggs. The percentage of plants forming eggs is proportional to the total quanta of blue wavelengths received up to a saturating value of about 400 μE·cm^-2; a 50% response is induced by 200 μE·cm^-2. The action spectrum for the induction of fertility has a main peak at 430 to 450 nm, with two subsidiary peaks in the blue and one in the near-ultraviolet light, but the action spectrum for photosynthesis is quite different, with peaks in the red, green and blue regions. These results indicate that egg formation in female gametophytes occurs as a specific morphogenetic response to blue light, which is independent of photosynthesis and growth, and trial experiments with male gametophytes of L. saccharina and gametophytes of other species of Laminariales indicate that these plants react similarly.     

Coelenterazine distribution and luciferase characteristics in oceanic decapod crustaceans

Coelenterazine biosynthesis has recently been demonstrated in the developing eggs of the decapod Systellaspis debilis. The cellular source of coelenterazine and the potential for biosynthesis in adult decapods, however, have not been fully investigated. We have conducted a systematic study of coelenterazine content in >230 individual decapods representing 19 species of Oplophoridae and 22 species from other families. We show for the first time that coelenterazine is responsible for both secretory and photophore luminescence in the same decapod. Tissues associated with secretory luminescence (hepatopancreas and stomach) in the Oplophoridae contained almost 3 orders of magnitude more coelenterazine (mean value=2154 pmol per specimen) than cuticular photophores (mean value=8 pmol per specimen). Coelenterazine content increases by 2 to 4 orders of magnitude during the development of three species of Oplophoridae. Species of Oplophoridae contain an order of magnitude more coelenterazine than those of other families (mean value=154 pmol per specimen). Coelenterazine was also detected in 11 apparently nonluminous decapod species (mean value=200 pmol per specimen). S. debilis luciferase characterisation enabled a luciferase assay to be developed to facilitate studies of the environmental control of bioluminescence. We hypothesise that the coelenterazine requirement in secretory bioluminescence exceeds that which could be assimilated from the food-chain. The significant increase of coelenterazine during the life cycle of secretory decapods supports this hypothesis. Putative evidence for environmental control of coelenterazine luminescence is also reported.     

Effects of light quality on initiation and development of meroplanktonic diatom blooms in a eutrophic shallow sea

We investigated the effects of light quality on resting stage cell germination and vegetative cell growth of meroplanktonic diatoms in a small port in Hakata Bay, Japan and in the laboratory. During the investigation over the year of 2006, the meroplanktonic diatom bloom first occurred in the end of May and then repeated wane and wax until October in the small port. From late April to middle May, light penetrating the water column was often strong and attenuations of all spectral lights were low. During this period, Skeletonema costatum, Thalassiosira minima, and Chaetoceros sp. appeared frequently, followed by the blooms of S. costatum and Chaetoceros sp. in late May. Thereafter, S. costatum and Chaetoceros sp. bloomed in late June but not in middle June, when pigmented flagellates bloom appeared. The attenuation of short-wavelength light such as violet and blue lights was markedly high during these diatom and flagellate blooms; all blooms disappeared within several days. Vegetative cell strains of the three diatoms under light emitting diodes (LEDs) with six different spectra (violet, blue, green, orange, red, and near-infrared) grew at a higher rate under short-wavelength light, violet and blue. On the other hand, when suspensions of bottom sediments from Hakata Bay were cultured under the same LEDs and in the dark, vegetative cells of S. costatum appeared under all LEDs except for orange and near-infrared, vegetative cells of T. minima appeared under all LEDs but not in the dark, and vegetative cells of Chaetoceros sp. appeared under violet and blue LEDs. However, vegetative cell densities of the three diatoms increased much more under violet light than under other LEDs within a short period (6 days). Our study indicates that underwater penetration by short-wavelength light, such as violet and blue, may be an important factor in the initiation and development of meroplanktonic diatom blooms.     

Contrast enhancement through structural variations in the rhabdoms of oplophorid shrimps

Rhabdom morphology in oplophorid shrimps varies both interspecifically and also within the eye of an individual, particularly with respect to the relative sizes of distal and proximal rhabdoms. We have combined published data on anatomical measurements, visual pigment absorption, and underwater light distribution to model the absorptance of light from different sources by the rhabdoms in these shrimps. In Systellaspis debilis the violet-sensitive distal rhabdom is prominent and increases in size along a dorso-ventral gradient. The model shows that the dorsal ommatidia are efficient at detecting downwelling irradiance and photophore emissions. In more ventral regions of the eye, the enlarged distal rhabdom results in the ommatidia in this region being more sensitive to eyeshine from other shrimps and to their bioluminescent secretions. This will improve the contrast of such light sources against the background space light. Acanthephyra pelagica has virtually no distal rhabdom and the model shows that this arrangement results in greater sensitivity.Communicated by J.P. Thorpe, Port Erin     

Effect of light quality on photosynthesis of the reef coral Montipora verrucosa

Pieces of the reef coral Montipora verrucosa (Lam.), collected from Kaneohe Bay, Oahu, Hawaii in 1982, were grown in four low-light treatments (11% sunlight): blue, green, red and the full spectrum of photosynthetically active radiation (PAR); and at high-intensity full PAR (90% sunlight). These acclimated corals were then tested for photosynthetic ability in blue, green, red, and white light. The photosynthetic parameters that were measured were; ligh-saturated photosynthetic rate, the initial slope of the photosynthesis/irradiance curve, the light intensity where these two lines crossed, and dark respiration. While acclimation intensity had a pronounced effect, the results also showed that the color of the acclimation treatment influenced the photosynthetic responses of the corals. The color of the light used in the measurements of photosynthesis had much less effect on the photosynthetic responses of the corals.Contribution No. 729 of the Hawaii Institute of Marine Biology     

Effects of light of altered spectral composition on coral zooxanthellae associations and on zooxanthellae in vitro

Pocillopora damicornis (Linnaeus) and Montipora verrucosa (Lamarck) were collected from Hawaiian reefs. In two experiments (September 1979-January 1980: ca. 4 mo; August-October 1980; ca. 2 mo), these reef corals were grown under sunlight passed through filters producing light fields of similar quantum flux but different spectral composition. In vitro cultures of symbiotic zooxanthellae (Symbiodinium microadriaticum Freudenthal) from M. verrucosa were cultured under similar conditions for 15 d. Blue or white light promoted more coral skeletal growth than green or red light. In both coral species, blue light increased the total amount of chlorophyll a of the coral-zooxanthellae association. In the perforate species, M. verrucosa, the pigment concentration was elevated by an increase in the density of zooxanthellae, but the pigment concentrations per algal cell remained unchanged; in the non-perforate species, P. damicornis, it appears that pigment concentration was elevated by an increase in pigment per algal cell, and not by an increase in density of zooxanthellae. The sunloving reef-flat coral P. damicornis did not grow as rapidly as the shade-species M. verrucosa at the low quantum flux (about 10% sunlight) provided by the experimental treatments. The in vitro cultures of zooxanthellae from M. verrucosa exhibited growth rates in light of altered spectral quality that correlated with the responses of the host coral species: blue and white light supported significantly greater growth than green light, and red light resulted in the lowest growth rate.Contribution No. 678 of the Hawaii Institute of Marine Biology     

Effects of light quality on chlorophyll and biliprotein accumulation in seaweeds

The control of chlorophyll and biliprotein synthesis by different qualities of continuous light in four seaweeds, collected off the coast of Málaga (Spain) in the winter of 1986 and 1987, was investigated over the short term. In the green algaUlva rigida C. Aghardh, and in the red algaeCorallina elongata Ellis et Soland andPlocamium cartilagineum (L.), chlorophyll synthesis was induced by blue light. However, in the red algaPorphyra umbilicalis (L.), chlorophyll accumulation was primarily induced by red light. Phycoerythrin synthesis inCorallina elongata, Plocamium cartilagineum andPorphyra umbilicalis was stimulated primarily by green light, whilst phycocyanin synthesis was induced by red. The effect of light quality on the synthesis of photosynthethic pigments was rapid. The induction of chlorophyll synthesis of after 6 h in light was 11 to 20% higher than in the dark control. The induction of biliprotein synthesis was two times greater than that of chlorophyll. The results are discussed in terms of chromatic adaptation and as adaptative responses to the underwater light environment. The possible role of phytochrome, and of a blue-light photoreceptor, in the control of chlorophyll and biliprotein synthesis is discussed.Please address all correspondence and requests for reprint to Dr López-Figueroa at his present address: Botanisches Institut der Universität München, Menzingerstraße 67, D-8000 München 19, FRG     

Molecular evidence for multiple lineages in the gorgonian family Plexauridae (Anthozoa: Octocorallia)

Octocorals are diverse and abundant on many marine hard substrates, and, within this group, members of the family Plexauridae are an important component of tropical reef assemblages, especially in the Caribbean. To understand historical relationships within this large and diverse assemblage, and to test the monophyly of the family and some of its genera, DNA sequences of two mitochondrial loci (msh1 and ND2, ~1,185 bp) were analyzed from 46 species in 21 genera from deep and shallow waters in the tropical western Atlantic and in the tropical western and eastern Pacific (plus 9 taxa in the closely related Gorgoniidae and 1 species of the more distantly related Alcyoniidae). Five strongly supported clades were recovered. Three large clades correspond roughly to the Plexauridae, Paramuriceidae, and Gorgoniidae, and two smaller clades were comprised of taxa previously assigned to several families. Astrogorgia sp. did not group with any of the clades. The mutual relationships among the five clades remain unclear. Several genera previously regarded as unrelated appear to be grouped among the three families; e.g. Hypnogorgia sp. (Paramuriceidae) falls within a clade consisting of both Pacific and Atlantic Muricea spp. (Plexauridae), while Swiftia sp., Scleracis sp., and an Atlantic Thesea sp. (all Paramuriceidae) group with the gorgoniids. In several instances, genera containing Atlantic and Pacific species were recovered as monophyletic (Muricea spp., Bebryce spp.). However, in at least three cases (Echinomuricea spp., Thesea spp., Villogorgia spp.), placement of Atlantic and Pacific species in the same genus may reflect convergence of sclerite morphology. The results indicate a strong need for reexamination of octocoral taxonomy using a combination of molecular, morphological, and chemical evidence.Electronic Supplementary Material Supplementary material is available in the online version of this article at http://dx.doi.org/10.1007/s00227-005-1592-y.Communicated by J.P. Grassle, New Brunswick     

Green and blue fluorescing dinoflagellates in Bahamian waters

At three stations in Bahamas waters, in 1989, 15 to 30% of all the dinoflagellates >20µm diameter observed in near-surface waters fluoresced green under blue excitation light, 55 to 66% fluoresced red, and the remainder did not fluoresce at all. The abundance of these green-fluorescing dinoflagellates ranged from ca 5 to 10 cells l^–1 at the study sites. Under UV excitation, however, the dinoflagellates had a blue to blue-green appearance. Almost all the blue-green fluorescing dinoflagellates appeared to be heterotrophic, except for one species,Phalacroma rapa Stein, which also contained red-fluorescing (under blue light) chlorophylla. The emission spectra from all species examined were of three basic types. Type 1 typically had two fluorescence emission peaks (ca 440 and ca 510 nm). Type 2 spectra possessed one sharp peak at 495 nm. Spectra belonging to Type 3 had a broad peak around 470 to 480 nm. The green fluorescence thus is likely caused by different substances in individual species. The attempt to reconstitute observed spectra with nicotinamide adenine dinucleotide (NADH) and riboflavin 5-phosphate (FMN) solutions was unsuccessful.     

Light quality in relation to growth,photosynthetic rates and carbon metabolism in two species of marine plankton algae

The effect of light quality on growth, photosynthesis and carbon metabolism in two species of marine algae,Cyclotella nana (Hustedt) andDunaliella tertiolecta (Butcher), was examined. Relative growth constants forC. nana were 0.37, 0.29 and 0.25 in blue, white and green light, respectively. Corresponding constants were 0.41, 0.31 and 0.29 forD. tertiolecta. Photosynthetic rates in both species were higher in blue light and lower in green light compared with white light of the same intensity. More than 60% of¹⁴C assimilated byC. nana orD. tertiolecta grown in blue or green light was incorporated into the ethanol-insoluble fraction, compared with 10 to 30% in this fraction in white light. The relative importance of the various components within this fraction was independent of light quality. Although less¹⁴C was assimilated into the ethanol-soluble fraction in blue or green light, there was a relative increase in some amino acids and organic acids in this fraction and a decrease in sugars and sugar phosphates relative to white light of the same intensity. These differences were independent of light intensity, photosynthetic rate and cell density in the cultures.