Oculina patagonica: a non-lessepsian scleractinian coral invading the Mediterranean Sea

The scleractinian coral Oculina patagonica De Angelis is a new immigrant from the Southwest Atlantic to the Mediterranean Sea, having established itself only recently along the Israeli coast. This species is the only scleractinian coral reported to have invaded a new region. In order to understand the swift establishment of this species along the Israeli coast, from 1994 to 1999 we studied its distribution, abundance, reproduction, recruitment, survival, and the effect of bleaching events on its population abundance. In addition, population studies of O. patagonica were performed at several localities along the eastern and western Mediterranean coasts. Highest abundance was recorded along the Spanish coast, reaching 30lj colonies per 10 m line transect in shallow water. Second in abundance was the Israeli coast, with a maximum of 10DŽ colonies per transect. O. patagonica was rare along the coast of Italy, and absent along the Mediterranean coast of France. During the study, both mortality and recruitment along the Israeli coast were very low. In contrast, recruitment along the Spanish coast was very high. Reproduction of the species was studied using gonadal histology. O. patagonica is gonochoric. Female gonads were first observed in May and male gonads in July, both reaching maturity in late August and early September. Naturally occurring azooxanthellate colonies of O. patagonica inhabiting small dark caves developed gonads and spawned in parallel to zooxanthellate colonies exposed to light. No gonads were found in zooxanthellate colonies that underwent bleaching during the reproduction season. The high incidence of bleaching events along the Israeli coast observed throughout the years of this study may explain the low recruitment of new colonies during the same period. In view of its current recruitment patterns, we expect further expansion of O. patagonica in range and abundance in the western Mediterranean, but very small expansion of the population in the eastern Mediterranean, due to repetitive annual bleaching events.     

Alternate coral–bryozoan competitive superiority during coral bleaching

Bleaching of corals results from the loss of their symbiotic algae (zooxanthellae) and/or pigments. The supply of photoassimilates provided by the zooxanthellae to the coral declines during bleaching and reduces the ability to activate energy-costly processes such as maintenance, growth and reproduction. In the present study we compared the competitive outcomes, expressed as overgrowth and changes in colony sizes of Oculina patagonica (an encrusting Mediterranean stony coral) and the bryozoan Watersipora sp., growing in contact with each other, during and between bleaching events. Year-round observations of tagged colonies showed alternating competitive outcomes: O. patagonica wins over Watersipora sp. between bleaching events, but loses during bleaching events. Using the ¹⁴C-point-labeling technique on coral tissue, we examined intra-colonial translocation of photosynthetic products from the point-tissue labeling towards interaction zones. In non-bleached O. patagonica, competition resulted in preferentially oriented translocation of ¹⁴C products to the interaction zone located up to 8 cm away from the tissue-labeling site. Sites opposite the interaction zone received significantly less labeled photoassimilates compared to the interaction zone. In bleached colonies (40-85% bleached surface area), such translocation did not occur, probably explaining the failure to compete with the encrusting neighbor Watersipora sp. Our findings demonstrate the importance of colonial integration and resource orientation for the competitive superiority of O. patagonica.     

Development of the escape response in larval walleye pollock (Theragra chalcogramma)

The development of the escape response of walleye pollock (Theragra chalcogramma) larvae from attacks by macrozooplanktonic and small-fish predators was quantified in laboratory experiments. Behavior was recorded using video cameras with silhouette illumination from infrared-emitting diodes and by visual observation. Laboratory-reared larvae of 1, 3, 8, 10, 12, 18, 22, 27, 42 days post-hatching, ranging in size from 4 mm to 10 mm total length, were used in the experiments. Even the youngest larvae were observed to exhibit a fast startle response. The percentage of successful larval escapes from the different predators increased as the larvae developed. Euphausiids (Thysanoessa raschii) and amphipods (Calliopiella pratti) often touched larvae but the larvae were usually able to escape and no successful captures of larvae over 22 days old were observed. Although successful escape from initial attacks by three-spine sticklebacks (Gasterosteus aculeatus) increased ontogenetically, sticklebacks were able to consume most larvae, even of the oldest age group, by repeated attacks. Day-old larvae had the lowest percent of escapes after encounters with jellyfish (Sarsia sp.), but the percentage of escapes increased dramatically for 3-day-old larvae. Escape speeds after an attack also increased with age, and tended to be higher after stickleback attacks and lower after jellyfish attacks. This study revealed that the escape response of larval pollock to attack by predators improves rapidly with development during the early larval stage.     

Identification of tenuis of four French Polynesian Carapini (Carapidae: Teleostei)

Four species of adult Carapini (Carapidae) occur on Polynesian coral reefs: Encheliophis gracilis, Carapus boraborensis, C. homei and C. mourlani. Samples collected in Rangiroa and Moorea allowed us to obtain different tenuis (larvae) during their settlement phases or directly inside their hosts. These were separated into four lots on the basis of a combination of pigmentation, meristic, morphological, dental and otolith (sagittae) features. Comparison of these characters with those of the adults allows, for the first time, taxonomic identification of these tenuis-stage larvae.     

Stimulatory effect of ingested protein and/or free amino acids on the secretion of the gastro-endocrine hormone cholecystokinin and on tryptic activity, in early-feeding herring larvae, Clupea harengus

In the larvae of many marine teleosts, the stomach is absent until they approach or attain metamorphosis. Consequently, the formation of chyme containing specific free amino acids from the gastric digestion of protein, which are believed to be signals initiating the release of the digestive hormone cholecystokinin (CCK), is lacking. CCK, when secreted into the blood circulation from specialized intestinal cells, stimulates gallbladder motility and is a key factor causing the release of pancreatic digestive enzymes into the gut lumen. Using first-feeding Atlantic herring larvae (Clupea harengus) as a model, the aim of the present study was to determine if a CCK response together with tryptic activity could be elicited in larvae ingesting dietary protein and/or FAA. Larvae were tube fed single lamellar liposome vesicles (SLV) containing: (1) physiological saline (PS), (2) bovine serum albumin (BSA), (3) specific free amino acids (FAA), or (4) a ratio (1:1) of BSA and FAA. The CCK and trypsin levels were then assayed (radio-immunoassay) at 0, 15, 60 and 120 min after tube feeding. A marked CCK response was elicited in all treatments compared to the PS control at 15 and 30 min and was significant (p<0.05) at 120 min after tube feeding. Larvae tube fed the FAA treatment exhibited CCK levels that increased linearly from 1.6 to 5.6 fmol mg^-1 dry weight (DW) after 2 h of digestion, although this response was below the BSA and BSA:FAA treatments. The BSA and BSA:FAA treatments, after 15 min of digestion, showed a rapid CCK increase, over the PS and the FAA liposome treatments, to 8.1 and 5.4 fmol mg^-1 DW, respectively. At the end of the assay, BSA and BSA:FAA demonstrated similar levels (10.2 and 9.2 fmol mg^-1 DW, respectively). Larvae tube fed the PS control or the FAA liposome treatment did not demonstrate any appreciable increase in tryptic activity during the 2 h digestion period (0.03-0.071 and 0.03-0.048 mU mg^-1 DW, respectively). In contrast, the BSA:FAA treatment increased from 0.03-0.148 mU mg^-1 DW 1 h after feeding, which was significantly (p<0.05) higher than the PS and FAA liposomes, and then decreased markedly (0.085 mU mg^-1 DW) after 2 h of digestion. The larvae tube fed BSA liposomes, however, demonstrated steadily increasing tryptic activity throughout the sampling period, attaining 0.255 mU mg^-1 DW after 2 h, which was significantly (p<0.05) more than all the other treatments. The results showed that ingested liposomes containing FAA or the protein BSA or a combination of these two nutrients effectively stimulated CCK production in first-feeding herring larvae. In contrast, liposomes containing only physiological saline did not elicit a CCK response. In addition, liposomes containing BSA stimulated tryptic activity in herring larvae, which was not observed in fish fed liposomes that included only FAA or PS. This suggests that a suitable protein substrate is required to regulate protein digestion.     

Role of the nutritive value of sediment in regulating population dynamics of the deposit-feeding polychaete Streblospio shrubsolii

The importance of changes in nutritive value of the sediment in regulating the dynamics of the small deposit-feeding polychaete Streblospio shrubsolii (Buchanam, 1890) was examined. First, fluctuations in the population dynamics of S. shrubsolii and in the nutritive content of the sediment were studied on a seasonal scale. Subsequently, a manipulative field experiment was used to test the hypothesis that, in summer, availability of food regulates aspects of the population dynamics of S. shrubsolii. In summer 1997, sharp increases in protein concentrations and in the number of individuals of S. shrubsolii were found compared to all the other seasons. Densities of S. shrubsolii also showed an increase in the subsequent season. Newly recruited juveniles (19-31 setigers) were abundant in summer and autumn 1997, whereas the number of juveniles (32-42 setigers) increased in autumn 1997. Large numbers of adults were found in summer 1997. Significant negative correlations occurred in summer 1997 between the concentrations of proteins and the total number of individuals, the number of newly recruited juveniles and the density of adults. No differences in densities of juveniles, adults or total number of individuals were found among plots before starting the experiment. After 20 days of experimental enrichment, proteins showed a tendency to increase. After 40 days of enrichment, the total number of individuals was significantly greater in the enriched plots. Large numbers of newly recruited larvae and postlarval adults were found in the enriched plots. The experiment corroborated the model that the growth of population was limited by the availability of food in summer. Thus, in this season, patches of food could have a fundamental role in determining the population dynamics of small deposit-feeders under natural conditions and over short time scales.     

Postingestive selection in the sea scallop (Placopecten magellanicus) on the basis of chemical properties of particles

Suspension-feeding bivalves are adapted to use a highly variable mixture of particles by sorting them before and after ingestion. Postingestive sorting in bivalves has been confirmed for several bivalve species, but few studies have attempted to isolate the factors influencing postingestive selection among different particles presented simultaneously. The ability of the sea scallop, Placopecten magellanicus (Gmelin), to sort a mixture of organic (¹⁴C-labeled dinoflagellates, Prorocentrum minimum) and inorganic (⁵¹Cr-labeled beads, diameter 16-18 µm) particles of similar size and shape within the stomach was examined. The study was carried out in August 1997 using scallops collected near Deer Island, New Brunswick, Canada. Sorting of the two particle types was measured by dissecting the scallops at intervals after feeding and comparing the ¹⁴C:⁵¹Cr ratios within the stomach, digestive gland, and feces. The ¹⁴C:⁵¹Cr ratio in the stomach decreased over time, indicating that sea scallops were sorting organic from inorganic particles. The ability of P. magellanicus to sort particles solely on the basis of chemical properties was tested in a second study by presenting them with a mixture of protein-coated and uncoated beads of two different colors. This study was carried out in February 2000 using scallops collected near Maces Bay, New Brunswick, Canada. Gut retention times of the two types of beads were measured using flow cytometry. Scallops retained protein-coated beads in the gut longer than uncoated beads, indicating postingestive selection by chemical properties. This study provides the first evidence for simultaneous postingestive sorting by bivalves of particles based solely on chemical properties. This would potentially enable P. magellanicus to preferentially retain particles of higher food quality longer than those of poor quality, thereby enhancing digestive efficiency.     

Effects of exposure to toxic and non-toxic dinoflagellates on oxygen consumption and locomotion in stage 1 larvae of the crabs Cancer oregonensis and C. magister

Sublethal effects on larval crabs upon exposure to toxic dinoflagellates were examined in the laboratory in early 1999. Specifically, oxygen consumption rates and geotaxis responses were determined for stage 1 larvae of the crabs Cancer oregonensis (Dana) and C. magister Dana that were exposed to non-toxic (Alexandrium tamarense, strain 115) or toxic (A. fundyense, strain 1719) dinoflagellates or to freshly hatched nauplii of the brine shrimp Artemia sp. In C. oregonensis, larvae exposed to the toxic dinoflagellate showed reduced rates of oxygen consumption compared to those exposed to non-toxic dinoflagellates or brine shrimp nauplii. Larvae exposed to a filtrate of the non-toxic dinoflagellate showed no change in oxygen consumption, but a reduced rate when exposed to filtrate from the toxic alga at densities >5᎒² cells ml^-1. In C. magister, larvae exposed to the non-toxic A. tamarense or the toxic A. fundyense had reduced oxygen consumption rates. Larvae exposed to filtrates of non-toxic and toxic dinoflagellates had no change in oxygen consumption. In geotaxis tests, C. oregonensis larvae exposed for 1 day to the toxic A. fundyense reduced their level of locomotion compared to those exposed to non-toxic A. tamarense or to brine shrimp nauplii. C. magister larvae showed no change in activity after a 1-day exposure to the toxic A. fundyense. After a 4-day exposure to A. fundyense, C. magister larvae had much reduced locomotion. Reduced locomotory activity in larvae exposed to toxic algae is consistent with the changes in oxygen consumption rates. Responding to exposure to toxic algae by reducing locomotion may affect vertical migration in these negatively buoyant crab larvae, resulting in sinking below a toxic alga bloom, at least temporarily.     

Leptocephalus energetics: assembly of the energetics equation

The principles of energetics were used to examine the energetic requirements of leptocephali. Respiration and excretion rates and daily growth rates combined with proximate composition were used to examine the allocation of energy into each of the three main components of energetics: metabolism, excretion and growth. The daily energetic requirements for leptocephali, referred to as type 2 larvae based upon their unique developmental strategy, were compared to the requirements of non-leptocephalus larvae, known as type 1. Leptocephalus daily energetic requirements were also compared to the energy available from the leptocephalus' proposed food sources. The four species of eel larvae selected were all from the order Anguilliformes: Paraconger caudilimbatus (Poey), Ariosoma balearicum (Delaroche), Gymnothorax saxicola Jordan and Davis, and Ophichthus gomesii (Castelnau). The allocation of energy to each of the components of energetics as well as the total energetic requirements for the leptocephali proved to be very different from those of type 1 larvae. Metabolism received the majority, 60-92%, of the energy required per day. Growth and excretion were allocated 4-39% and <1-21%, respectively, of the total energy needed per day. Leptocephali required <50% of the energy needed by type 1 larvae of equal dry mass. The unique growth strategy used by leptocephali allows them to increase rapidly in size while allocating the majority of their energy, not to growth as in most larval fish, but to metabolism.     

In vivo and in vitro differences in chloroplast functionality in the two north Atlantic sacoglossans (Gastropoda,Opisthobranchia) <Emphasis Type="Italic">Placida dendritica</Emphasis> and <Emphasis Type="Italic">Elysia viridis</Emphasis>

The photosynthetic functionality in chloroplasts in the two sacoglossan molluscs Placida dendritica and Elysia viridis from the Trondheim fjord in Norway was studied. P. dendritica and E. viridis with no functional chloroplasts in their digestive system were introduced to the green macroalgae Codium fragile. Our results showed that P. dendritica was not able to retain functional (photosynthetic) chloroplasts. Transmission electron microscopy (TEM) showed that chloroplasts were directly digested when phagocytosed into the digestive cells. Four stages of chloroplast degradation were observed. A corresponding operational quantum yield of chl a fluorescence (Φ_PSII ~ 0) indicated autofluorescence, and the presence of highly degraded chl a supported these observations. In contrast, E. viridis was able to retain functional chloroplasts. For this species it took only 1 week for the chloroplasts inside the digestive cells to acquire the same Φ_PSII and light utilisation coefficient (α) as C. fragile kept under the same light conditions. Data for 8 days showed a 2–6-fold increase in the maximum photosynthetic rate (P _max) and light saturation index (E _k) relative to C. fragile. This increase in available light was probably caused by a reduced package effect in the digestive gland of E. viridis relative to C. fragile, resulting in a partial photoacclimation response by reducing the turnover time of electrons (τ). Isolated pigments from C. fragile compared to E. viridis showed the same levels of photosynthetic pigments (chl a and b, neoxanthin, violaxanthin, siphonaxanthin, siphonein and β,ε-carotene) relative to μg chl a (w:w), indicating that the chloroplasts in E. viridis did not synthesise any new pigments. After 73 days of starvation, it was estimated that chloroplasts in E. viridis were able to stay photosynthetic 5–9 months relative to the size of the slugs, corresponding to an RFC of level 8 (a retention ability to retain functional chloroplasts (RFC) for more than 3 months). The reduction in Φ_PSII, P _max and α as a function of time was caused by a reduction in chloroplast health and number (chloroplast thylakoid membranes and PSII are degraded). These observations therefore conclude that chloroplasts from C. fragile cannot divide or synthesise new pigments when retained by E. viridis, but are able to partially photoacclimate by decreasing τ as a response to more light. This study also points to the importance of siphonaxanthin and siphonein as chemotaxonomic markers for the identification of algal sources of functional chloroplasts.     

Sequential utilization of free amino acids, yolk proteins and lipids in developing eggs and yolk-sac larvae of barfin flounder Verasper moseri

Changes in the contents of free amino acids (FAA), M_r 170,000 lipovitellin (oLv B), that is the major yolk protein in ovulated eggs, and lipids were measured in developing eggs and yolk-sac larvae of barfin flounder (Verasper moseri) to elucidate the sequential utilization of these nutrient stocks before the first feed. Hatching takes place on the 10th day after fertilization at a water temperature of 8°C, and the hatched larvae absorb almost all of their yolk masses within 21 days after fertilization. The total FAA content showed no change during the first 4 days, then decreased to about 13% of the initial level by the 13th day after fertilization. During the consumption of FAA, non-essential amino acids tend to decrease earlier than essential amino acids. The native molecular weight and immunoreactivity of M_r 170,000 oLv B did not show any change during the first 16 days after fertilization, though the sodium dodecyl sulphate-polyacrylamide gel electrophoresis patterns of oLv B showed a serial change. The oLv B contents, measured by quantitative immunodiffusion using antiserum against oLv B of ovulated eggs, were approximately stable during the 13 days after fertilization, then decreased rapidly until the end of yolk-sac absorption. Phospholipids (PL), which seem mostly to bind with lipovitellin-proteins, decreased gradually after hatching coincident with the decrease in oLv B and M_r 330,000 lipoprotein. From these results, we conclude that there are three periods for sequential nutrient utilization in barfin flounder embryos and larvae: (1) pre-FAA utilization period, 0-4th day; (2) FAA utilization period, 4th-13th day; (3) oLv B and PL utilization period, 16th-21st day post-fertilization.     

Population dynamics and secondary production of the wedge clam <Emphasis Type="Italic">Donax</Emphasis><Emphasis Type="Italic">hanleyanus</Emphasis> (Bivalvia: Donacidae) on a high-energy,subtropical beach of Brazil

The population biology of Donax hanleyanus (Philippi, 1845) (Bivalvia: Donacidae) was studied by monthly sampling from June 1998 through June 2000, at Restinga da Marambaia Beach, Brazil. Two transects were established and divided into ten strata parallel to the waterline, and five replicates were taken with a 0.04 m² sampler in each stratum. The highest densities of D. hanleyanus were recorded in winter (September 1998, July 1999) and autumn (April 2000). A stratified distribution was observed: recruits were found mainly in the middle swash zone, while juveniles and adults occurred across the tidal gradient up to the retention zone. Mortality rates did not differ significantly between years. Annual production (in ash-free dry mass) ranged from 0.76 g AFDM m^-2 year^-1 (1998) to 3.67 g AFDM m^-2 year^-1 (1999), while the production-to-biomass (P/B) ratio varied from 1.45 to 1.59. Life span was ca. 17 months. Of all variables tested, only two, one biological and one physical, seem to have influenced the population dynamics of this species. A significant negative correlation between the densities of the suspension-feeders D. hanleyanus and Emerita brasiliensis (Crustacea: Decapoda) indicated possible intraguild competition, and there was a significant exponential correlation between beach slope and the mean across-shore position of D. hanleyanus. Data compiled from literature suggests a latitudinal gradient in population parameters, with mortality and renewal rate (P/B) of different species of Donax increasing and life span decreasing from temperate to tropical regions. Other factors influencing population dynamics, such as food availability, and the contributions of individual and community biomass to energy and nutrient cycling are also discussed.     

Quinones in cockchafers: additional function of a sex attractant as an antimicrobial agent

Summary. Females of the forest cockchafer, Melolontha hippocastani Fabr. (Coleoptera: Scarabaeidae, Melolonthinae), are known to produce toluquinone and 1,4-benzoquinone. The latter component has been shown in our earlier studies to act as a sex attractant that enhances synergistically the attraction of males towards plant volatiles induced by feeding females. Analyses of whole body extracts from adults and grubs (L3) of M. hippocastani by coupled gas chromatography--mass spectrometry revealed the presence of 1,4-benzoquinone and toluquinone also in males and larvae. Quantitative analyses showed that extracts from females contained significantly more of 1,4-benzoquinone and toluquinone than extracts from males. Remarkably, extracts from grubs contained significantly higher amounts of both compounds than extracts from females. Inhibition assays using Escherichia coli, Saccharomyces cerevisiae, and the entomopathogenic fungi Metarhizium anisopliae and Beauveria brongniartii revealed inhibitory effects of 1,4-benzoquinone and toluquinone against all tested microorganisms. However, the amounts necessary for inhibition of entomopathogenic fungi and S. cerevisiae in the laboratory assay were higher than those found in the extracts from M. hippocastani.     

Recruitment in the intertidal limpet Lottia digitalis (Patellogastropoda: Lottiidae) may be driven by settlement cues associated with adult habitat

The ribbed limpet, Lottia digitalis, is found high in rocky intertidal habitat throughout its geographic range. In order to identify likely natural settlement locations for larvae of this species, laboratory-reared larvae were settled onto substrata collected from within and near an adult L. digitalis habitat. Of larvae exposed to rock chiseled from within high-intertidal adult habitat, 31.0% and 23.3% underwent metamorphosis during two separate experiments. Similarly, an unidentified filamentous green alga that was isolated from this rock induced metamorphosis in 26.6% and 8.7% of larvae during additional experiments. In contrast, larvae did not metamorphose upon bare rocks or upon rocks encrusted with a crustose corraline alga (CCA) that were collected from lower intertidal zones, nor did they metamorphose upon the macroalgae Ulva sp., Enteromorpha contorta, Alaria marginata, or Polysiphonia sp. The presence of mucus from adult conspecifics during these experiments did not enhance metamorphosis onto rock taken from adult habitat, but it did induce metamorphosis in an average of 13.5% and 7.0% of larvae introduced to the mid-intertidal bare rock and CCA substrata, respectively. Finally, 38.0% and 34.4% of larvae from two experiments underwent metamorphosis when exposed to the high-intertidal barnacle Pollicipes polymerus. These results suggest that larval settlement, rather than differential post-settlement mortality and/or migration, drives recruitment of L. digitalis in high-intertidal habitats.     

The influence of swimming speed on sustained swimming performance of late-stage reef fish larvae

Replicate clutches of larvae were swum in a swimming flume at 4, 7, 10, 13, and 16 cm s^-1 and the time swum until exhaustion recorded. There was a significant relationship between sustained swimming time and swimming speed for both maximum (R²=0.77; P<0.05) and mean sustained swimming times (R²=0.78; P<0.05), with fish swimming at slower speeds swimming longer and covering greater total distances. The relationship observed agrees with theoretical principles relating increasing swimming speed with increasing drag. We used our data for Amphiprion melanopus, combined with published information, to predict the swimming speeds that other reef fish taxa should be able to maintain for significant lengths of time (12-48 h) using three different models. The results agree well with field estimates (R² values from 0.45 to 0.84), suggesting that there may be underlying factors influencing swimming ability in reef fish larvae that can be used to predict swimming abilities of different taxa. These models suggest that sustained swimming behaviour by reef fish larvae could have a much greater impact on modifying larval dispersal than previously thought.     

Blue sprat <Emphasis Type="Italic">Spratelloides robustus</Emphasis> (Clupeidae: Dussumieriinae): a temperate clupeoid with a tropical life history strategy?

This article describes the life-history strategy of the blue sprat Spratelloides robustus in South Australia and compares the demographic traits observed with those of other clupeoids. Validation studies that involved marking the sagittae of captive fish with oxy-tetracycline suggested that growth increments are deposited daily. The oldest fish examined was 82 mm caudal fork length and 241 days old, which suggests S. robustus may live for less than 1 year. Growth rates were high during larval stages (0.34 mm day^у) and remained high throughout juvenile (0.33 mm day^у) and adult stages (0.19 mm day^у). S. robustus reached 50% maturity at approximately 60 mm caudal fork length after approximately 135 days. Spawning occurred from October to February (spring to late summer) and larvae were found mainly in Spencer Gulf, Gulf St Vincent, and Investigator Strait. Females spawned multiple batches of demersal eggs every 1-2 days. Batch fecundities were low (mean=756, SD=341) and increased linearly with length and weight. The life history of S. robustus is dissimilar to other small to medium-sized temperate clupeoids, but similar to those of many small sub-tropical and tropical clupeoids, including other Spratelloides species. Gulf St Vincent and Spencer Gulf may be considered to be "seasonally subtropical systems" in an otherwise temperate region that support a suite of species, including S. robustus, that have life-history strategies similar to those of sub-topical and tropical taxa.     

Cellulose digestion and phenol oxidation in coastal isopods (Crustacea: Isopoda)

In order to test three hypotheses on digestive constraints that may have affected the colonization of land by isopods, two marine isopods and one semi-terrestrial species were screened for their ability to oxidize phenolic compounds and digest cellulose in natural and artificial diets. Ligia pallasii (Isopoda: Oniscidea) and Gnorimosphaeroma oregonense (Isopoda: Sphaeromatidea) oxidized dietary phenolics, but Idotea wosnesenskii (Isopoda: Valvifera) did not, even though it feeds on seaweeds that are rich in phenolics. All three species were able to digest some cellulose, but this ability was least developed in the marine phytophagous species, Idotea wosnesenskii, and best developed in the semi-terrestrial L. pallasii. After reducing the number of endosymbiotic bacteria in the hepatopancreas (midgut digestive gland) by feeding antibiotics, cellulose digestion in L. pallasii was significantly reduced. Our results are consistent with the hypotheses that (1) the ability to oxidize phenolics is absent in phytophagous marine isopods, but present in saprophagous marine and semi-terrestrial species, (2) the ability to digest cellulose was an important pre-adaptation facilitating a fully terrestrial life-style in isopods, and (3) endosymbiotic bacteria in the hepatopancreas aid digestion in terrestrial isopods, and to a lesser degree in semi-terrestrial species, but not in marine isopods.     

Genetic analysis of sexual reproduction in the dendrophylliid coral Balanophyllia elegans

The ahermatypic scleractinian Balanophyllia elegans has served as a model of limited larval dispersal in an aclonal species. However, other species from the same family (Dendrophylliidae) produce larvae asexually, and closely connected polyps of B. elegans, potentially the result of asexual reproduction, are commonly observed in the field. Here, we use a combination of laboratory experiments, controlled crosses, and genetic surveys of field-collected individuals to demonstrate (1) marker allozymes are inherited in accordance with Mendel's laws, (2) polyps that are connected in the field are not genetically identical, and (3) laboratory manipulation of a single polyp can produce a second polyp on the aboral side of the original, but not adjacent to the original. In combination, these results suggest that the larvae of B. elegans result from mictic sexual reproduction, and that connected polyps result not from asexual budding but rather from the fusion of genetically distinct individuals.     

Induction of larval settlement and metamorphosis of the sea urchin Strongylocentrotus intermedius by glycoglycerolipids from the green alga Ulvella lens

In aquaculture centers of the northern region of Japan, "Nami-ita" (waved polycarbonate plates), on which the green alga Ulvella lens Crouan frat. (Chaetophoraceae: Chaetophorales) was cultured, are used to promote larval settlement and metamorphosis of the sea urchin species Strongylocentrotus intermedius (A. Agassiz) and S. nudus (A. Agassiz). We investigated chemical inducer(s) for larval settlement and metamorphosis of these sea urchins with extracts of U. lens. Bioassay-guided separation of the methanol extract using a combination of column and thin-layer chromatography led to the isolation of several active compounds, the chemical structures of which were determined by spectral and chemical methods. These active compounds were identified as glycoglycerolipids, all comprising several molecular species: sulfoquinovosyl monoacylglycerols (SQMGs), sulfoquinovosyl diacylglycerols (SQDGs), monogalactosyl monoacylglycerols (MGMGs), monogalactosyl diacylglycerols (MGDGs), digalactosyl monoacylglycerols (DGMGs) and digalactosyl diacylglycerols (DGDGs). Among these glycolipids, SQMGs, MGMGs, MGDGs and DGMGs induced larval metamorphosis of the sea urchin S. intermedius. SQMGs and MGDGs induced larval metamorphosis at a concentration of 5 µg ml^-1, whereas SQDGs and DGDGs only induced larval settlement. These glycoglycerolipids are new congeners of chemical inducers to settlement and metamorphosis of planktonic larvae of sea urchins. The findings would provide a better understanding of larval settlement and metamorphosis in sea urchins.