Temperature,Herbivory and Epibiont Acquisition as Factors Controlling the Distribution and Ecological Role of an Invasive Seaweed

The invasive canopy alga, Codium fragile ssp. tomentosoides, first observed at the Isles of Shoals in 1983, has become the dominant canopy species to 8 m throughout the islands. Codium populations are replacing themselves at most sites in what appears to be a new, climax, canopy species. However, Codium densities have declined in protected Gosport Harbor areas where it first became established. Codium has only slowly expanded its presence in adjacent nearshore subtidal habitats. Recent studies suggest a combination of factors that may be influencing the relative success of populations between habitats. The herbivorous sea slug, Placida dendritica, may be reducing populations in protected areas in spite of predators such as the green crab, Carcinus maenas, while surge may inhibit herbivore buildup in exposed habitats. Temperature instability due to localized, wind-driven upwelling may be slowing the buildup of subtidal Codium populations in nearshore sites. The combination of Codium dominance and the acquisition of increasing epibiont diversity are producing a new, potentially more complex community state than the previous kelp-dominated climax typical of the Gulf of Maine.     

Detecting the impacts of notorious invaders: experiments versus observations in the invasion of eelgrass meadows by the green seaweed <Emphasis Type="Italic">Codium fragile</Emphasis>

Biological invasions can vary in the extent of their effects on indigenous communities but predicting impacts for particular systems remains difficult. In coastal marine ecosystems, the green seaweed Codium fragile ssp. fragile is a notorious invader with its reputation based on studies conducted largely on rocky shores. The green seaweed has recently invaded soft-bottom eelgrass communities by attaching epiphytically to eelgrass (Zostera marina) rhizomes, thereby creating the potential for disruption of these coastal habitats through competition or disturbance. We investigated the effect of this invader on various aspects of eelgrass performance (shoot density and length, shoot growth, above- and below-ground biomass, carbohydrate storage) using both small-scale manipulative and large-scale observational experiments. Manipulative experiments that varied Codium abundance demonstrated clear negative effects over a 4-month period on shoot density and carbohydrate reserves, but only for high, but realistic, Codium biomass levels. Light levels were much lower under canopies for high and medium density Codium treatments relative to low and control Codium cover treatments, suggesting that shading may influence eelgrass growing under the algal cover. In contrast, these effects were either not detectable or very weak when examined correlatively with field surveys conducted at larger spatial scales, even for sites that had been invaded for over 4 years. It is premature to extend generalizations of Codium’s impact derived from studies in other systems to eelgrass communities; further efforts are required to assess the long-term threats that the alga poses to this ecosystem. This study demonstrates the need to investigate impacts of invasions over multiple scales, especially those that incorporate the temporal and spatial heterogeneity of the invader’s abundance.     

INTRON REVEALED BY NUCLEOTIDE SEQUENCE OF LARGE SUBUNIT OF RIBULOSE-1,5-BISPHOSPHATE CARBOXYLASE/OXYGENASE FROM CODIUM FRAGILE (CHLOROPHYTA): PHYLOGENETIC ANALYSIS1

The coding sequence for the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (rbcL) from Codium fragile (Suringar) Hariot chloroplast DNA is 1428 bp in length and contains a 1813-bp group II intron. The only other organisms in which introns have been found in the rbcL gene are Euglena and Astasia. The Codium intron likely had a separate origin from the Euglena and Astasia introns, based on comparisons of intron sizes and sequences. Phylogenetic analyses of rbcL nucleotide and amino acid sequences place Codium between Chlorella and two Chlamydomonas spp., indicating that the Chlorophyceae may be polyphyletic.     

Changes in structure of isolated chloroplasts ofCodium fragile andCaulerpa filiformis in response to osmotic shock and detergent treatment

Summary The ultrastructure of chloroplasts from two genera of coenocytic green algae,Codium andCaulerpa, were examined after suspension in hypotonic solution and in detergent at various concentrations. The capacity of the suspensions to carry out CO₂-dependent and ferricyanide-dependent O₂ evolution was measured under the same conditions of osmotic strength and detergent concentration.The chloroplasts in the preparations were in the form of cytoplasts and gave rates of O₂ evolution comparable with those expected from undamaged chloroplasts. Suspension in hypotonic solution depressed the rate of CO₂-dependent O₂ evolution in both species, but this was partially restored in theCodium chloroplasts when these were re-suspended in iso-osmotic solutions. Major structural changes were observed only after suspension in buffer when theCodium chloroplasts lost their outer envelope, most of their stroma, and the thylakoids became swollen.Caulerpa chloroplasts were more variable in their response and, even when suspended in buffer only, the proportion of the plastids which had lost all of their stroma and thylakoid swelling was never as common as inCodium chloroplasts. However, once suspended in hyper-osmotic medium below 700 mosmolar,Caulerpa chloroplasts could not regain their capacity for CO₂-dependent O₂ evolution.Detergent treatment removed the cytoplast membrane but not the cytoplasmic material adhering to the chloroplast envelope. High concentrations of detergent were needed to cause loss of the chloroplast envelope, loss of stromal contents and unstacking of the thylakoids.Caulerpa chloroplasts were less sensitive to detergent than those ofCodium. There was no indication that specific structures such as the thylakoid organizing body were resistant to detergent action. The results show that exposure to hypotonic solutions and to detergent results in less damage to these chloroplasts than it would to those of higher plants. It is proposed that the basis of this unusual resistance is not due to the properties of the chloroplast membranes but to the presence of material which coats the organelles during isolation. This material is likely to be identical with the sulphated xylo-mannogalactan isolated from the vacuole contents of these algae and which has the visco-elastic properties essential to allow the organelles to resist disruption by osmotic forces and disintegration by detergents.     

Stadial and seasonal occurrence of gregarines and nematomorphs in two New Zealand cockroaches

Abstract

Twoendemic New Zealand cockroaches, Parellipsidion pachycercum Johns, 1966 and Celatoblatta peninsularis Johns, 1966, each have a different species of gregarine and a nematomorph. Gregarine infection prevalence was low (4% in P. pachycercum, 11% in C. peninsularis). In C. peninsularis, incidence, intensity, and gametocyst production were high only in early winter; in P. pachycercum, three peaks of incidence, intensity, and gametocyst production corresponded to early autumn, mid-winter, and mid-summer. Only 0.5% of P. pachycercum and 0.26% of C. peninsularis had one or two nematomorphs. In P. pachycercum, nematomorphs were found in late spring and summer, whereas in C. peninsularis they were found only during mid-winter.     

GROWTH OF THE GREEN ALGA CODIUM FRAGILE IN A CONNECTICUT ESTUARY1

An in situ comparison of environmental and physiological factors was undertaken in 1971–72 (15 months) in the Niantic River estuary to elucidate some of the important aspects, of the growth and development of the seaweed Codium fragile. In general, Codium in the estuary has a growing season of from 6 to 9 months. Growth increments during this period are relatively constant. Temperature and salinity are the main limiting factors to growth, although low summer concentrations of inorganic nitrogen may also be involved. Reproduction by means of swarmers occurs only in late summer or autumn. Codium appears highly adapted to the role of a colonizing species. It not only possesses the capability to occupy the harshest of environments, but also a system of reproductive alternatives which facilitates rapid colonization. The availability of substrate for attachment is the chief factor limiting its spread in this estuarine system.     

Lankesteria barretti n. sp. (Eugregarinida,Diplocystidae), a Parasite of the Mosquito Aedes triseriatus (Say) and a Review of the Genus Lankesteria Mingazzini*

SYNOPSIS. Lankesteria barretti n. sp. (Eugregarinida, Diplocystidae) is named from the mosquito Aedes triseriatus in Texas. The young cephalins occur within the midgut epithelial cells. When they reach a length of about 150–200 μ they rupture the host cell and are released into the space between the epithelium and the peritrophic membrane, becoming gamonts. These grow to about 140–310 by 40 μ at the anterior end and 12 μ at the posterior end. When the host pupates they enter the lumen of the Malpighian tubules; pairs join in syzygy by their anterior ends and later more laterally. Each pair forms a spherical gametocyst about 60–100 μ (exceptionally 250 μ) in diameter. A large number of oocysts develop in each gametocyst. The mature oocysts are spindle-shaped, 11 by 5.4–5.7 μ, and contain 8 elongate sporozoites and a refractile residuum. The gametocyst wall breaks down, releasing oocysts in the Malpighian tubules of the host when it is adult. The oocysts pass out in the feces and presumably infect new larvae by ingestion. The cephalins and gamonts of L. barretti differ from those of L. culicis (of Aedes aegypti) in having a relatively anterior instead of a central nucleus and in lacking a noticeable mucron; its longitudinal folds are not as well-developed as in L. culicis, and its paraglycogen granules are larger. The fine structure of L. culicis and L. barretti is described in detail. Their gamonts have a polar ring but no definite conoid. The taxonomy of the genus is reviewed, but its species have been so poorly described that it is impossible to be sure whether they are all really Lankesteria. About 19 species have been described (5 from turbellaria, 8 from tunicates, perhaps 1 from Amphioxus, 1 from the chaetognath Sagitta sp., 1 from Phlebotomus and 3 from mosquitoes).     

Synthesis of Diaryl Sulphonates and N-Acyl-aryl Sulphonamides as Potential Fungicides

A novel lectin (CBA) was isolated from the green alga, Codium barbatum, by conventional chromatographic methods. The hemagglutination-inhibition profile with sugars and glycoproteins indicated that CBA had preferential affinity for complex type N-glycans but not for monosaccharides, unlike the other known Codium lectins specific for N-acetylgalactosamine. CBA consisted of an SS-linked homodimer of a 9257-Da polypeptide containing seven cysteine residues, all of which were involved in disulfide linkages. The cDNA of the CBA subunit coded a polypeptide (105 amino acids) including the signal peptide of 17 residues. The calculated molecular mass from the deduced sequence was 9705 Da, implying that the four C-terminal amino acids of the CBA proprotein subunit were post-translationally truncated to afford the mature subunit (84 amino acids). No significantly similar sequences were found during an in silico search, indicating CBA to be a novel protein. CBA is the first Codium lectin whose primary structure has been elucidated.     

TRACING SPECIES INVASION IN CODIUM,A SIPHONOUS GREEN ALGA,USING MOLECULAR TOOLS

The siphonous green alga Codium fragile occurs in many temperate marine regions and is composed of a number of distinct subspecies. Included in this taxon is the common open coast C. fragile subsp. fragile of the northeast Pacific and the weedy C. fragile subsp. tomentosoides which has invaded temperate marine communities in the Atlantic and Pacific oceans. The center of origin of this weedy subspecies is not known, although it is thought to have dispersed from the northwest Pacific. To examine the relationship of the weedy subspecies to the indigenous northeast Pacific form, chloroplast DNA was compared. Each of these subspecies has a restriction map that is uniform throughout its geographic distribution, and the patterns are distinct from each other and from other Codium species examined. However, the two share an almost identical genome size and arrangement of genes. A population in San Francisco Bay was found to be indistinguishable from the weed C. fragile subsp. tomentosoides from the Atlantic. The potential for using molecular data in solving systematic problems in Codium has been clearly demonstrated.     

Anticoagulant properties of a sulfated galactan preparation from a marine green alga, Codium cylindricum

An anticoagulant was isolated from a marine green alga, Codium cylindricum. The anticoagulant was composed mainly of galactose with a small amount of glucose, and was highly sulfated (13.1% as SO Na). The anticoagulant properties of the purified anticoagulant were compared with that of heparin by assays of activated partial thromboplastin time (APTT), prothrombin time (PT) and thrombin time (TT) using normal human plasma. The anticoagulant showed similar activities with heparin, however, weaker than heparin. On the other hand, the anticoagulant did not affect PT even at the concentration at which APTT and TT were strongly prolonged. The anticoagulant did not potentiate antithrombin III (AT III) and heparin cofactor II (HC II), thus the anticoagulant mechanism would be different from that of other anticoagulants isolated so far from the genus Codium.     

LEARNING AS A FACTOR IN DIET SELECTION BY ELYSIA VIRIDIS (MONTAGU) (OPISTHOBRANCHIA).

Elysia viridis (Montagu) occurs naturally in populations feedingon the fleshy, siphonalean green alga Codium or on the coarse,filamentous green alga Chaetomorpha. Only about half of theE. viridis transferred from Codium to Chaetomorpha in the laboratorywere able to learn to feed on this alga. Handling time decreasedsignificantly during the learning-period. All E. viridis transferredfrom Chaetomorpha to Codium in the laboratory were able to learnto feed on the latter alga. Handling time also decreased withexperience in these animals. Ingestive conditioning occurredin animals transferred from Chaetomorpha to Codium. These animalshad to go through a learning-period again when they were offeredChaetomorpha after 6–9 weeks with Codium Ingestive conditioningwas also evident from preference experiments; animals preferredthe food they had been kept on prior to the experiments. Thesefindings are discussed in relation to optimal diet theory. (Received 14 December 1987; accepted 22 March 1988)     

DNA analysis methods for recognizing species invasion: the example of Codium,and generally applicable methods for algae

Analysis of DNA can help to distinguish those morphological characters indicative of species difference from those representing retained traits or parallel evolution. This can be of great value in detecting recent invaders. The choice of which DNA characters to examine not only dictates the methodology to be used but must also be appropriate for the detection level sought. Restriction endonuclease fragment comparisons of plastid DNA have been used to assess Codium species; the results show C. fragile subsp. tomentosoides from east and west coast North America to be identical while sympatric endemic Codium species each display their own unique set of fragments. For species of other algae, plastid DNA fragment patterns are not necessarily identical across a morphological species, e.g. Pandorina morum. Such repetitive element probes as M13 and the use of RAPDs are more appropriate for analysis of populations within species. DNA base sequence comparisons of nuclear rDNA genes often yield too few variant bases between closely related species for reliable identifications. Analysis of the more variable Internal Transcribed Spacer (ITS) region, lying between the small and large ribosomal subunit genes in nuclear DNA, yields more extensive base pair variation between species and relatively little within species; it may be an alternative choice for endonuclease restriction fragment analysis or for sequencing.     

Artificial substrates enhance non-native macroalga and N2 production

The introduction of non-native species occurs within a context of other anthropogenic impacts: thus a holistic approach is needed to understand interactive effects. Installation of shoreline protection structures is increasing in response to rising sea levels and increasing frequency of intense storms. Shoreline hardening structures can facilitate establishment of non-native species with multiple potential consequences. We measured abundances of both native and non-native Codium, a green macroalga, on natural hard substrates (oyster reefs) and artificial substrates (bulkheads and revetments) in two estuaries and assessed the effects of each Codium species on nitrogen fixation and net N₂ fluxes. Native C. decorticatum was the most abundant (86 %) Codium on oyster reefs, while exotic C. fragile dominated (99 %) artificial substrates. N₂ production via denitrification was greater than nitrogen fixation for both species and the net N₂ production associated with non-native C. fragile was greater than with native C. decorticatum. Comparing our results with surveys conducted in the 1940s before C. fragile had invaded, indicates that non-native Codium has outcompeted native Codium on artificial substrates, but that natural substrate provided by oyster reefs remains a refuge for native Codium. Although shoreline hardening with artificial structures can reduce ecosystem services provided by coastal marsh and other habitats, an unexpected beneficial consequence was the N₂ production associated with the non-native Codium, which has the potential to mitigate anthropogenic nutrient loading. Our results illustrate that the interaction between multiple anthropogenic impacts can be positive, and indicate that non-ephemeral macroalgae could be an overlooked component in nitrogen removal from marine ecosystems by enhancing denitrification.     

95 Development of macroalgal (seaweed) taxonomic keys utilizing digital & media technology

Specimens of Codium fragile (Suringar) Hariot ssp. tomentosoides were collected from 9 sites in New England, and Long Island, New York at intervals throughout the years 1999‐2003. Segments were removed from the thalli and chopped into fine fragments, mostly individual utricles and medullary filaments. Fragments were incubated in enriched seawater in dim light at 15C, 12:12 LD. Within 2–3 days, in almost all cases (more than 300) motile cells formed in many of the utricles and filaments. These were 10–15 micrometer elongated biflagellate heterokont cells. They appeared to consume the chloroplasts, and within 24 hours were reduced to colorless cells, about 5 micrometers long. These cells are unable to grow in Codium chloroplast suspensions. They appear to be always associated with Codium thalli, despite attempts to clean the thalli, and were never seen in utricles or filaments of intact plants. Their ultrastructure is under investigation and will be reported on here.     

From introduced species to invader: what determines variation in the success ofCodium fragile ssp.tomentosoides (Chlorophyta) in the North Atlantic Ocean?

The green algaCodium fragile ssp.tomentosoides (Chlorophyta) has been introduced accidentally and successfully from Japan to many shores of the northern and southern hemispheres, including those of the Northeast and Northwest Atlantic Ocean. On most European coasts,Codium occurs regularly but at low abundances in the intertidal zone and is absent from subtidal habitats. In contrast,Codium is extremely abundant in subtidal kelp beds in the Northwest Atlantic Ocean where it often reaches nuisance proportions. This differential success cannot be accounted for by either the properties of the invader or by physico-chemical differences between invaded coasts. A theoretical comparison between two regions on opposite sides of the Atlantic Ocean, i.e. Eastern Nova Scotia, Canada, and south central Britain, illustrates how the resident benthic community may determine the difference in relative abundance ofCodium in subtidal habitats between northeast America and Europe. In this review, low floral species diversity, biological disturbance and facilitation by a previous species invasion are suggested as potential factors for the establishment, success and abundance ofCodium in the Northwest Atlantic Ocean, but these require testing in field experiments.     

The Life Cycle of Ganymedes oaklandi n. sp., an Acephaline Gregarine of Gammarus fasciatus (Say)*

SYNOPSIS. Ganymedes oaklandi n. sp. (Ganymedidae) from the intestine of Gammarus fasciatus (Say) is described, and its life cycle is given. In the trophic stage the gregarine is acephaline, with an elongated cylindrical body slightly tapered anteriorly, and is up to 298 × 64 μ. The gametocysts are up to 121 × 99 μ, and are covered with a secreted thick sticky gelatinous coat. The spores are released from the gametocyst by rupturing of the cyst wall. The spore body is spherical, approximately 6 μ in diameter, and has 4 episporal rays about 20 μ long.     

Cytochromes and other pigments of dissimilatory sulphate-reducing bacteria

Summary A survey was made of various visible light absorption spectra of whole cells, particulate and soluble fractions and haem extracts of representative strains of all known species of sulphate-reducing bacteria. The previously accepted distinction that Desulfovibrio species contain only a c-type cytochrome whereas Desulfotomaculum species contain only a b-type cytochrome was not confirmed. The pigment contents of the genera Desulfovibrio and Desulfotomaculum were not completely distinct from each other, but both genera had characteristic spectral patterns. Reduced minus oxidized spectra of whole cells and particulate fractions showed the presence of b-type cytochromes in all Desulfotomaculum species and in Desulfovibrio africanus. However, protohaem, the prosthetic group of b-type cytochromes, occurred in haem extracts from all species, although only just detectable in the extract from Desulfovibrio vulgaris NCIB 8303. Particulate c-type cytochromes were found in Desulfotomaculum orientis, Desulfotomaculum nigrificans and all the Desulfovibrio species, but the amount in Desulfotomaculum nigrificans was very small. Only the Desulfovibrio species contained soluble c-type cytochromes. Spectral properties indicated that a d-type cytochrome might exist in species in addition to Desulfovibrio africanus, but no supporting evidence was obtained from results of haem extractions. Some spectra contained peaks which could not be identified.     

A soluble CO- and NO-bindingc-type cytochrome inNeisseria meningitidis

Group BNeisseria meningitidis (SDIC) was grown aerobically in Mueller-Hinton medium to stationary phase and then broken either by sonic oscillation or high pressure extrusion from a French pressure cell. The particulate fraction (345,000×g, 3 h) contained cytochromesc, b, o, and evidence of ana-type. The supernatant fraction contained a solublec-type cytochrome (c ₅₄₉). The pyridine hemochrome derivatives of acid-acetone-extracted supernatant fractions were shown to be free of other cytochrome types. The solublec cytochrome increased during the growth cycle of the organism, reaching a maximum after cells entered stationary phase, whereas the cellular level of other cytochromes from the particulate fraction started to decline as cells progressed from log into stationary phase. Osmotic shock, as well as other treatments, failed to selectively release the solublec cytochrome from the cell. When untreated, thec ₅₄₉ in the supernatant fraction remained in a reduced form. While it was not air oxidizable, it was readily oxidizable with K₃Fe(CN)₆. In the reduced form, thec ₅₄₉ bound either CO or NO, but in the oxidized form, only NO was bound. The results obtained from this study indicate that the solublec ₅₄₉ is probably best classified as a cytochromec′.     

Acquired Phototrophy through Retention of Functional Chloroplasts Increases Growth Efficiency of the Sea Slug Elysia viridis

Photosynthesis is a fundamental process sustaining heterotrophic organisms at all trophic levels. Some mixotrophs can retain functional chloroplasts from food (kleptoplasty), and it is hypothesized that carbon acquired through kleptoplasty may enhance trophic energy transfer through increased host growth efficiency. Sacoglossan sea slugs are the only known metazoans capable of kleptoplasty, but the relative fitness contributions of heterotrophy through grazing, and phototrophy via kleptoplasts, are not well understood. Fitness benefits (i.e. increased survival or growth) of kleptoplasty in sacoglossans are commonly studied in ecologically unrealistic conditions under extended periods of complete darkness and/or starvation. We compared the growth efficiency of the sacoglossan Elysia viridis with access to algal diets providing kleptoplasts of differing functionality under ecologically relevant light conditions. Individuals fed Codium fragile, which provide highly functional kleptoplasts, nearly doubled their growth efficiency under high compared to low light. In contrast, individuals fed Cladophora rupestris, which provided kleptoplasts of limited functionality, showed no difference in growth efficiency between light treatments. Slugs feeding on Codium, but not on Cladophora, showed higher relative electron transport rates (rETR) in high compared to low light. Furthermore, there were no differences in the consumption rates of the slugs between different light treatments, and only small differences in nutritional traits of algal diets, indicating that the increased growth efficiency of E. viridis feeding on Codium was due to retention of functional kleptoplasts. Our results show that functional kleptoplasts from Codium can provide sacoglossan sea slugs with fitness advantages through photosynthesis.     

Typification of species of Codium (Bryopsidales, Chlorophyta) described by Okamura

Type specimens of six species of Codium described by Okamura are illustrated, including the holotype of Codium barbatum and lectotypes of Codium coactum, Codium intricatum, Codium pugniforme, Codium saccatum, and Codium subtubulosum. All species are currently recognized except C. pugniforme, which is indistinguishable from the previously described Codium spongiosum Harvey, Codium subtubulosum was abandoned by Okamura in favor of the previously described Codium divaricatum Holmes, but because of the prior existence of C. divaricatum (C. Agardh) Biasoletto, C. subtubulosum is the correct name for this species.