Population biology of the crustose red alga Lithophyllum incrustans Phil. 2. A comparison of populations from three areas of Britain

The age structures and reproductive characteristics of three populations of the crustose red alga Lithophyllum incrustans from Orkney, Northumberland and South Devon are described. Geographical trends in values of the generation time and the capacity for increase ( r _m) are shown for each population. Reproductive allocation, however, shows no such trend. Whilst 16% of the populations are sexual in Devon, only 4% are sexual in Northumberland, and sexual plants are absent from Orkney.     

Population biology of the crustose red alga Lithophyllum incrustans Phil. Three populations on the east coast of Britain

The distribution of the crustose red alga Lithophyllum incrustans in the British Isles is described. Three populations are analysed demographically, two having age class distributions corresponding to a type III survivorship curve characteristic of populations in which the greatest mortality occurs in the youngest age classes. The more southern of these two populations has a longer generation time (14.2 years) than the more northern (8.5 years). The third and most southern population has an age class distribution dominated by the 6- and 7-year-old categories. There were few sexual thalli (around 3^o,) but they appeared to put more effort into reproduction than the asexual thalli.     

Isolation of algal spore lytic C17 fatty acid from the crustose coralline seaweed Lithophyllum yessoense

The algal spore lytic fatty acid of heptadeca-5,8,11-trien (HpDTE: C17:3) was isolated from the crustose coralline seaweed Lithophyllum yessoense. HpDTE, an odd-numbered carbon fatty acid, showed more than 50% lysis at a concentration of 5 μg.mL⁻¹ against the spores of three chlorophyte species, nine rhodophytes, four phaeophytes, and the cells of four phytoplankton species. Lysis activity increased with the number of double bonds and carbon atoms in the fatty acid increased. HpDTE showed a ten-fold stronger activity with a LC₅₀ of 3.1 μg.mL⁻¹ than α-linolenic acid (C18:3).     

Lithophyllum cuneatum sp. nov. (Corallinaceae, Rhodophyta), a new species of non-geniculate coralline alga semi-endophytic in Hydrolithon onkodes and Neogoniolithon sp. from Fiji, South Pacific

A new species of semi-endophytic coralline alga, Lithophyllum cuneatum (Corallinaceae: Lithophylloideae), is described from Fiji. The species is characterized by a wedge-like thallus that is partially buried in the thallus of the host coralline, Hydrolithon onkodes (Heydrich) Penrose et Woelkerling or occasionally Neogoniolithon sp., and that appears at the surface of the host as a small pustule that is usually paler in color than the host. The thallus consists of erect filaments that are derived from a single cell. The basal cell, when visible, is non-palisade, and areas of bistratose margin are absent. Cells of contiguous erect filaments are joined by secondary pit connections. Epithallial cells are present in 2–3 layers, and individual trichocytes are common. Gametangial plants are dioecious. Male conceptacles have simple spermatangial systems that are confined to the floors of their elliptical chambers. Carposporangial conceptacles contain 5–8 celled gonimoblast filaments that are borne at the margin of a more-or-less discoid fusion cell, and so occupy the periphery of the elliptical conceptacle chambers. Tetrasporangial conceptacles are uniporate, with roofs formed from peripheral filaments, and chambers lack a central columella of sterile filaments. Despite its semi-endophytic nature, haustorial cells are absent, and plastids and pigmentation are present.     

The galactan sulphate of the red alga Polysiphonia lanosa.

The structure of the galactan sulphate of P. lanosa has been established by a combination of methylation, treatment with alkali, and partial methanolysis of the alkali-treated polysaccharide to give derivatives of agarobiose. The polysaccharide belongs to the agar class, in which 3-linked derivatives of beta-D-galactose alternate with 4-linked derivatives of alpha-L-galactose in a repeating sequence. In addition to D-galactose itself, the 3-linked units include 6-O-methyl-D-galactose, D-galactose 6-sulphate, and a hitherto unreported unit, 6-O-methyl-D-galactose 4-sulphate. The 4-linked units include L-galactose 6-sulphate, 2-O-methyl-L-galactose 6-sulphate, and 3,6-anhydro-L-galactose.     

Population dynamics and conservation biology of the over-exploited Mediterranean red coral

The main goal of ecologists is nowadays to foster habitat and species conservation. Life-history tables and Leslie-Lewis transition matrices of population growth can be powerful tools suitable for the study of age-structured over harvested and/or endangered species dynamics. Red coral (Corallium rubrum L 1758) is a modular anthozoan endemic to the Mediterranean Sea. This slow growing, long lived species has been harvested since ancient times. In the last decades harvesting pressure increased and the overall Mediterranean yield reduced by 23. Moreover, mass mortality (putatively-linked to global warming) recently affected some coastal populations of this species. Red coral populations are discrete genetic units, gonochoric, composed by several overlapping generations and provided of a discrete (annual) reproduction. A population of this precious octocoral was studied in detail and its static life table was compiled. In order to simulate the trends overtime of the population under different environmental conditions and fishing pressures, a discrete, non-linear model, based on Leslie-Lewis transition matrix, was applied to the demographic data. In this model a bell-shaped curve, based on experimental data, representing the dependence of recruitment on adult colonies density was included. On these bases the stability of the population under different density, reproduction and mortality figures was analysed and simulations of the population trends overtime were set out. Some simulations were also carried out applying to the studied population the mortality values measured during the anomalous mass mortality event which really affected some red coral populations in 1999. The population under study showed high stability and a strong resilience capability, surviving to a 61% reduction of density, to a 27.7% reduction of reproduction rate and to an unselective harvesting affecting 95% of the reproductive colonies.     

Helper effects on pup lifetime fitness in the cooperatively breeding red wolf (Canis rufus)

The evolutionary maintenance of cooperative breeding systems is thought to be a function of relative costs and benefits to breeders, helpers and juveniles. Beneficial effects of helpers on early-life survivorship and performance have been established in several species, but lifetime fitness benefits and/or costs of being helped remain unclear, particularly for long-lived species. We tested for effects of helpers on early- and late-life traits in a population of reintroduced red wolves (Canis rufus), while controlling for ecological variables such as home-range size and population density. We found that the presence of helpers in family groups was positively correlated with pup mass and survival at low population density, but negatively correlated with mass/size at high density, with no relation to survival. Interestingly, mass/size differences persisted into adulthood for both sexes. While the presence of helpers did not advance age at first reproduction for pups of either sex, females appeared to garner long-term fitness benefits from helpers through later age at last reproduction, longer reproductive lifespan and a greater number of lifetime reproductive events, which translated to higher lifetime reproductive success. In contrast, males with helpers exhibited diminished lifetime reproductive performance. Our findings suggest that while helper presence may have beneficial short-term effects in some ecological contexts, it may also incur long-term sex-dependent costs with critical ramifications for lifetime fitness.     

The amino acid sequence of ferredoxin from the red alga Porphyra umbilicalis.

The amino acid sequence of the ferrodoxin of Porphyra umbilicalis was determined by the dansyl-phenyl isothiocyanate method, on peptides obtained by tryptic, chymotryptic and thermolytic digestion of the protein or its CNBr-cleavage fragments. The molecule consists of 98 residues, has an unblocked N-terminus and shows considerable similarity with other plant-type ferredoxins. It is the first reported sequence of a red-algal ferredoxin.     

The use of environmental variables in the interpretation of genotype-environment interaction.

The method proposed by Hardwick and Wood (1972) for relating genotype-environment interactions to measures of environmental variables is extended and two examples are discussed.     

The minimal eukaryotic ribosomal DNA units in the primitive red alga Cyanidioschyzon merolae.

Cyanidioschyzon merolae is a small unicellular red alga that is considered to belong to one of the most deeply branched taxa in the plant kingdom. Its genome size is estimated to be 16.5 Mbp, one of the smallest among free-living eukaryotes. In the nucleus containing this small genome, one nucleolus is clearly observed, but the molecular basis for the intranuclear structure including ribosomal DNA organization is still unclear. We constructed a bacterial artificial chromosome library for C. merolae 10D composed of two subsets with different insert size distributions. The two subsets have average insert sizes of 97 and 48 kb, representing 10.0- and 6.9-fold genome-equivalent coverage of the haploid genome, respectively. For application to whole-genome shotgun sequencing, the termini of each clone were sequenced as sequence-tagged connectors and mapped on the contigs assigned to chromosomes. Screening for rRNA genes by conventional colony hybridization with high-density filter blots and subsequent sequencing revealed that the C. merolae genome contained the smallest number of ribosomal DNA units among all the eukaryotes examined to date. They consist of only 3 single units of rRNA genes distributed on separate chromosomal loci, representing an implication for concerted evolution. Based on these results, the origin and evolution of the nucleolus are discussed.     

The amino acid sequence of a flavodoxin from the eukaryotic red alga Chondrus crispus.

The amino acid sequence of the constitutive flavodoxin from the red alga Chondrus crispus was determined from the analyses of peptide fragments derived by enzymic digestions of the carboxymethylated protein. This is the first sequence reported for a flavodoxin from a eukaryote. The protein is composed of 173 amino acid residues and is a member of the longer-chain group of flavodoxins. The extent of sequence homology to the three other flavodoxins in the group for which sequences are available is in the range 36-39%, with the most strongly conserved regions being those implicated in binding of the FMN, the redox-active prosthetic group. Nevertheless, Chondrus crispus flavodoxin stands apart in a number of respects, in particular the possession of an unusually high content of proline, with these residues distributed more or less regularly along the peptide chain.     

The reproductive biology of Scyliorhinus canicula in the Bristol Channel, U.K.

Among 972 Scyliorhinus canicula , the overall sex ratio (males:females) was 1:1·23. Males matured between 490 and 540 mm L _T with 50% maturity at 520 mm. Females matured between 520 and 640 mm L _T with 50% maturity at 550 mm. Female gonadosomatic index peaked in May. Fecundity increased with fish length. The egg laying season lasted 10 months with a peak in June and July. The importance of erect, sessile invertebrates such as bryozoans, poriferans and hydroids as egg-case deposition sites has been established. Recently hatched fish were born in an equal sex ratio and at a mean length of 100·5 mm and mean weight of 3·07 g. One intersexual fish is described.     

The reproductive structures of the Mediterranean alga Laurencia pelagosae (Ceramiales,Rhodophyta)

Reproductive structures of Laurencia pelagosae are described for the first time. Tetrasporangia, in parallel arrangement, are cut off from the mother cells adaxially; antheridial branches, which are unramified, are inserted in depressions lacking a row of axial cells on their bases; cystocarps are sessile and subspherical. The occurrence of secondary pit-connections between epidermal cells and of lenticular thickenings in the walls of medullary cells is documented. The species is included in the new section Pelagosae within the subgenus Laurencia.     

The covalent linkage of protein to carbohydrate in the extracellular protein-polysaccharide from the red alga Porphyridium cruentum.

The extracellular anionic polysaccharide isolated from cultures of a unicellular red alga, Porphyridium cruentum, contains a small amount of protein after extensive purification. The polysaccharide and protein are recovered in the same fraction after isopycnic CsCl-density-gradient centrifugation in 4M-guanidinium chloride, under conditions designed to separate proteins from polysaccharide. The peptide portion of the protein-polysaccharide is released from the polysaccharide by alkali under conditions for beta-elimination. The released peptide is non-diffusible, but in can be separated from the polysaccharide by precipitation of the polysaccharide as the cetylpyridinium complex. Under conditions for beta-elimination of certain O-glycosidic carbohydrate-protein linkages, selective destruction of serine and threonine occurs. The addition of a reducing agent to the alkali mixture produces a selective increase in alanine and alpha-aminobutyric acid. Addition of a tritiated reducing agent to the alkali mixture produces radioactive alanine and alpha-aminobutyric acid, and xylitol as the only sugar alcohol. Similar results are obtained from glycopeptides isolated from partial acid hydrolysates. A macromolecular structure of the protein-polysaccharide is suggested by a comparison of the intrinsic viscosity of material before and after treatment with alkali and proteolytic enzymes.     

The effect of local environmental variables on the helminth parasite communities of the pointedbelly frog Leptodactylus podicipinus from ponds in the Pantanal wetlands

Understanding the patterns of species distribution and abundance has been at the core of ecology. In general, these patterns are determined by species dispersion as well as by abiotic and biotic environmental conditions. Similarly, host-parasite relations and the structure of parasite assemblages are also shaped by environmental conditions and landscape composition. Herein, we assessed the influence of environmental variables and parasite species dispersion on the structure of helminth parasites communities in the frog Leptodactylus podicipinus. We sampled 10 ponds and recorded area, depth, altitude, pH, dissolved oxygen, salinity, temperature, and extent of soil, water, and vegetation cover as well as the distances between the ponds. We collected 121 frogs and found 9 helminth taxa; 2 of them were core species (prevalence higher than 50%), which contributed to the relatively high similarity observed among the ponds. Most of the helminths showed some variation in the frequencies of occurrence among communities from different ponds. The change in species composition among ponds was explained by the environmental variables but not by the distance between the ponds. Moreover, the results indicated that local processes (variation in environmental conditions) were more important than the regional processes (species distribution) in determining the structure of parasite communities. The variation in helminth communities among ponds in response to moderate differences in pond environmental characteristics points to the potential of helminth species as indicators of environmental conditions.     

Photomovement of the red alga Porphyridium cruentum (Ag.) naegeli I. Photokinesis

Photokinesis of the red alga Porphyridium cruentum was studied with the aid of a population method. Because of the slow spreading velocity (0.35 m/min) the duration of the experiments was 7 days in general. According to the white light illuminance-response curve the zero threshold of photokinesis lies below 10 lx and the optimum around 10,000 lx. With further increasing illuminance the photokinetic effect decreases, reaching zero at about 100,000 lx. The action spectrum indicates that the photokinetically active radiation is absorbed by photosynthetic pigments, namely the biliproteins B-phycoerythrin, R-phycocyanin and allo-phycocyanin, as well as by chlorophyl a, although the photokinetic effect of blue light is relatively low. From the action spectrum and the results of inhibitor experiments with DCMU, DBMIB and DSPD it is concluded that the photokinetic effect is due to an additional ATP supply from non-cyclic and/or pseudo-cyclic photophosphorylation to the motor apparatus.Abbreviations DCMU 3-(3,4-dichlorophenyl)-1, 1-dimethylurea - DBMIB Dibromothymoquinone (2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone) - DSPD Disalicylidenepropanediamine-(1,3)     

The distribution of colonies of the bryozoan Antarctothoa bougainvillei on the red alga Hymenena laciniata

The cheilostome bryozoan Antarctothoa bougainvillei (d’Orbigny) is the most frequent epibiont on the ribbon-like red alga Hymenena laciniata (Hooker f. & Harvey) Kylin in San Sebastián Bay (Tierra del Fuego, Argentina). Twenty-one thalli and 1,484 colonies were examined to analyse the relationship between both species. In most cases, number and area of colonies did not differ significantly at both sides of the thallus. Ancestrulae (i.e., founder zooids originating colonies by asexual budding) were mostly oriented facing the algal growing edge. Colonies were more frequent on central than on marginal zones of the thalli. The population of A. bougainvillei was mainly composed of very small colonies (<10 mm²). Larger colonies predominated and intraspecific competition was more intense near the basal portions of the thalli. Fecundity (number of ovicells) increased at a significantly higher rate in colonies with margins obstructed by conspecific neighbours than in free-growing colonies. Colonies were significantly larger on somatic than on reproductive algal tissues. As total and reproductive surfaces covered by colonies of A. bougainvillei were on average very low (4.43% and 0.53%, respectively), this epibiont is not supposed to produce a negative effect on H. laciniata. Handling editor: T. P. Crowe     

The effect of temporal variability in salinity on the invasive red alga Gracilaria vermiculophylla

Non-native, invasive species are often characterized by being tolerant to environmental stressors, leaving them more fit relative to native species. The red alga Gracilaria vermiculophylla originates from the NW Pacific but has recently spread along the coastlines of Western Europe, where it has become abundant in many shallow, soft-bottom estuaries. Salinity is important for the local and regional distribution of algae. The distribution of G. vermiculophylla in Europe suggests that it thrives well in hyposaline environments and that it may be more fit than some native algae under such conditions. Little, however, is known about the ecophysiology of G. vermiculophylla and it is therefore difficult to predict its spread and future distribution. Laboratory experiments with G. vermiculophylla showed that steady-state salinity above 15?psu was optimal for growth and that the growth rate was reduced at salinities below 15?psu. Variable salinity reduced the growth rate and larger oscillations were more stressful than small ones. Exposure to very low salinity (0–5?psu) was stressful for the alga and algae exposed to these low levels for 2–4 days were unable to recover fully. Gracilaria vermiculophylla did not seem to perform better in hyposaline conditions than many native, estuarine species. The present distribution of G. vermiculophylla in Scandinavia can be explained well by its response to salinity, but this may not explain its present success relative to many naturally occurring algal species.