Identification and field evaluation of the female sex pheromone of Stathmopoda masinissa in Korea

The sex pheromone of Stathmopoda masinissa Meyrick, an important pest of persimmon fruit in East Asia such as Korea, China, and Japan, was investigated. A lure using (E4,Z6)-4,6-hexadecadienyl acetate (E4,Z6-16Ac), which was identified as a sex pheromone compound of Japanese population, did not work at all for Korean population. Therefore, components in the abdominal extract of the moth were identified and their attractiveness was evaluated in the field. Two components, E4,Z6-16Ac and (E4,Z6)-4,6-hexadecadien-1-ol (E4,Z6-16OH) were identified from the extract of female abdominal extract in a ratio of 10–15:90–85 by GC–MS analysis with synthetic standards. E4,Z6-16Ac and E4,Z6-16OH were previously identified as EAG-active components of this moth in Japanese population. However, (E4,Z6)-4,6-hexadecadienal (E4,Z6-16Ald), which is one of the abdominal extract components and EAG-active component in Japanese population, was not detected in our samples. In the persimmon orchard, single component of E4,Z6-16Ac or E4,Z6-16OH was not attractive. However, the 1:1 mixture of the two components significantly increased the captures of male S. masinissa. Interestingly, traps baited with E4,Z6-16Ac captured significantly higher number of Oedematopoda ignipicta (Lepidoptera: Stathmopodidae) than the traps baited with E4,Z6-16OH or blend of the two components. The attractiveness of E4,Z6-16Ac to O. ignipicta is a new finding.     

Chemical defense in Platyphora kollari Baly and Leptinotarsa behrensi Harold (Coleoptera: Chrysomelidae). Hypotheses on the origin and evolution of leaf beetles toxins

Summary. The defensive secretions of Platyphora kollari beetles (Chrysomelidae) from Brazil contained one oleanene glycoside. This was identified as 3-O-g-D-glucopyranosyl-(l̆)-g-D-glucuronopyranosyl-hederagenin (8), by a combination of 1D and 2D NMR methods (COSY, HMQC, MBC) and SIMS. There were also several amino acid derivatives, including the known non-protein amino acid (Z)-2-amino-3,5-hexadienoic acid (1), the new dipeptide L-n-glutamyl-2-amino-(3Z)-hexenoic acid (4), ethanolamine (7), and a mixture of phosphatidylcholines. Compounds 1 and 7 have already been identified in several leaf beetle taxa. Secretions of Leptinotarsa behrensi contained as major triterpene glycoside 3-O-g-d-glucopyranosyl-(l̅)-g-d-glucuronopyranosyl-oleanolic acid-28-O-g-d-glucopyranoside (9), already isolated from Platyphora opima. Although the host plants of these beetles were devoid of these triterpene glycosides, g-amyrin was shown to be present in three plants on which different species of triterpene-producing chrysomelids had been fed (Mikania micrantha, Ipomoea batatas and Convolvulus arvensis). This suggests that these insects are able to use g-amyrin from their food plant as a precursor to their oleanolic- and hydroxyoleanolic acid glycosides. The distribution of toxins already identified in leaf beetles suggests that amino acid derivatives could be a plesiomorphic character, considering their wide distribution, whereas the secretion of triterpene saponins, probably derived from ubiquitous plant triterpenes, could be an apomorphic character shared by some Doryphorina. The secretion of cardenolides derived from ubiquitous plant phytosterols would be another apomorphic character shared by other Doryphorina and Chrysolinina.     

Are all signals the same? Ontogenetic change in the response to conspecific and heterospecific chemical alarm signals by juvenile green sunfish (<Emphasis Type="Italic">Lepomis cyanellus</Emphasis>)

Within aquatic communities, individuals may gain survival benefits by responding to the chemical alarm signals of heterospecific prey guild members. Piscivorous individuals, however, should be selected to use such chemical signals as foraging cues. A variety of centrarchid species, such as largemouth bass (Micropterus salmoides), undergo an ontogenetic change in their response to the chemical alarm cues of heterospecific guild members, switching from antipredator to foraging responses. This ontogenetic shift should occur when potential foraging benefits outweigh any survival advantage gained from an antipredator response. To test this model, we exposed juvenile green sunfish (Lepomis cyanellus) to the skin extracts of conspecifics, a heterospecific prey guild member (finescale dace, Phoxinus neogeaus) or an allopatric heterospecific (green swordtails, Xiphophorus helleri). Juvenile sunfish exhibited a significant positive relationship between standard length and time spent moving and a significant negative relationship between length and time in a spine-erect posture, when exposed to dace skin extract, but not to either swordtail or conspecific skin extracts. Smaller individuals of less than 90 mm standard length (SL) decreased time moving and increased time with spines erect (indicating an antipredator response) while larger individuals (>90 mm SL) increased time moving and decreased time with spines erect (indicating a foraging response), when exposed to dace skin extract. Conversely, juvenile sunfish, regardless of size tested, always exhibited an antipredator response to conspecific skin extract. Sunfish exhibited no change in behaviour in response to swordtail skin extracts. These data further support our model of a threat sensitive trade-off in the response to chemical alarm signals by juvenile centrarchids.     

Anti-sense expression of putrescine N-methyltransferase confirms defensive role of nicotine in Nicotiana sylvestris against Manduca sexta

Summary. Several lines of evidence support the defensive function of nicotine production in the Nicotiana genus against a range of herbivores, but the evidence is largely correlative. To suppress nicotine production in planta and to test its defensive function, we expressed DNA of putrescine N-methyl transferase in an anti-sense orientation (AS-PMT) in N. sylvestris and fed leaf material from two lines of transformed and wild type plants to Manduca sexta larvae. Larvae consumed more leaf area and gained more mass on the foliage of plants with low PMT expression and low nicotine levels as compared to plants with high PMT expression and high nicotine levels and wild type plants. Overall, larval consumption and performance were negatively correlated with constitutive nicotine levels. We conclude that nicotine decreases the palatability of N. sylvestris leaves to the nicotine-resistant M. sexta larvae.     

Biosynthetic studies on marking pheromones of bumblebee males

Summary. The biosynthetic pathway of the formation of males'marking pheromones of two bumblebee species, Bombus lucorum and B.lapidarius, was studied for the first time. After applications ofdeuterium labelled palmitic acid ([2H31]-hexadecanoic acid) into eitherthe head capsules or abdomens the corresponding deuterium labelledpheromone components were detected in the labial gland (LG) extracts ofmales of both species. In B. lucorum, ethyl [2H29]-hexadec-9-enoate andethyl [2H31]-hexadecanoate were identified. No deuterium-labelled ethyltetradecenoate, that would correspond to shortening of the carbon chain,was detected. In B. B. lapidarius, [2H31]-hexadecan-1-ol and[2H29]-hexadec-9-en-1-ol were found in the LG. Furthermore, thedeuterium labelled precursor was incorporated into triacylglycerols(TAG) of the fat bodies of males. In vitro incubation of the labialglands of B. lucorum males with deuterium-and 13C-labelled palmiticacid lead to the formation of saturated ethyl esters only.     

Selective herbivory on low-zinc phenotypes of the hyperaccumulator Thlaspi caerulescens (Brassicaceae)

Summary. The European plant Thlaspi caerulescens hyperaccumulates zinc in its leaves to concentrations exceeding 2 %. This may represent a defense against herbivory, as shown by reduced feeding on plants grown in high-zinc versus low-zinc substrates. However, the more evolutionarily relevant comparison involves plants whose metal content differs due to genetic rather than environmental causes. In our study, plants were grown in a uniform hydroponic solution containing 10 mg/l Zn. Foliar Zn concentrations were measured, and plants of contrasting Zn concentration were chosen for feeding trials using Pieris napi oleracea larvae. Comparisons revealed no statistically significant preferences when young larvae were used, but highly significant avoidance of high-Zn leaves by later-instar caterpillars, suggesting that hyperaccumulation could evolve in response to the selective pressures of herbivory.     

Phytotoxic effects of phenolic acids from <Emphasis Type="Italic">Merostachys riedeliana,</Emphasis> a native and overabundant Brazilian bamboo

Merostachys riedeliana Rupr. is a native and overabundant bamboo species in the Brazilian Atlantic Forest. Moderate to strong allelopathic activity may be one mechanism that explains this super-dominance and the changes in structure and composition of forest areas occupied by bamboo. This study evaluated the phytotoxic effect of M. riedeliana extracts and fractions and identified their putative allelochemicals. We investigated the presence of allelochemicals in soil collected from stands occupied by M. riedeliana. Furthermore, we evaluated the putative effect of tree allelochemicals, individually and combined, on germination and growth. The aqueous extract of leaves and its ethyl acetate fraction presented the highest inhibitory effects on seed germination and seedling growth. The effect of the extracts and fractions on the target species was species-specific. Neither the individual nor the combined phenolic acids significantly inhibited seed germination; however, a pronounced growth inhibition was observed in M. bimucronata seedlings treated with vanillic acid and in E. verna and M. bimucronata seedlings treated with combined phenolic acids. Isovitexin, vitexin, isoorientin, orientin, and their O-glycoside derivatives, the lactonic dimer of the p-hydroxybenzoic acid and 3,4-methylenedioxymandelic acid were identified in the aqueous extracts and ethyl acetate fraction by Liquid Chromatography-Diode Array Dectector/Electrospray Ionization/Mass Spectrometry (LC-DAD/ESI–MS/MS). The Gas Chromatography-Mass Spectrometer (GC–MS) profile of the same extract and fraction showed the presence of benzoic, benzeneacetic, salicylic, p-hydroxybenzoic, p-hydroxyphenylacetic, vanillic, p-coumaric, protocatechuic, syringic, gallic, m-coumaric vanillylmandelic, 4-methylmandelic, 3,4-methylenedioxymandelic and trans-ferulic acids. The p-benzoic acid and the apigenin 6-C-glucoside (isovitexin) were identified in the soil extract collected from under bamboo-growing areas. Even though laboratory bioassays are not completely predictive of the allelopathic effects that occur in nature, the results of this study provide preliminary evidence of allelopathy as a possible species-specific inhibition mechanism of native species that explain the impoverishment of floristic richness and the functional groups in areas where M. riedeliana is overabundant.     

团花锦蛇、绿锦蛇和三索锦蛇的核型及Ag-NORs

报道了锦蛇属团花锦蛇（Ｅ．ｄａｖｉｄｉ）、绿锦蛇（Ｅ．ｐｒｖｓｉｎａ）和三索锦蛇（Ｅ．ｒａｄｉａｔａ）３个种的核型和Ａｇ－ＮＯＲｓ,团花锦蛇的型２ｎ＝３６（８Ｖ＋６ｓＶ＋２Ｉ＋２０Ｍ）,绿锦蛇的核型２ｎ＝３６（７Ｖ＋７ｓＶ＋２Ｉ＋２０ｍ）,三索锦蛇的核型２ｎ＝４０（６Ｖ＋３ｓＶ＋２ｓＩ＋５Ｉ＋２４ｍ）;①团花锦蛇和绿锦蛇的染色体数目和结构与此属大多数咱的相似,;②此种为雄性,未见染色体异型。③Ａｇ     

Depth-related variability in the photobiology of two populations of<Emphasis Type="Italic"> Halophila johnsonii</Emphasis> and<Emphasis Type="Italic"> Halophila decipiens</Emphasis>

The threatened seagrass Halophila johnsonii Eiseman coexists subtidally with H. decipiens Ostenfeld in southeastern Florida, but only H. johnsonii also occurs intertidally. Pulse amplitude modulated fluorometry and fiber-optic spectrometry were used to investigate the photobiology of two populations of H. johnsonii and H. decipiens in an attempt to explain these distribution patterns. Maximum photosynthetic quantum yields (Fv/Fm) were measured in situ as a function of depth distribution within, and between, these two species at two sites (Jupiter Sound, 26°57′N; 80°04′W, and northern Biscayne Bay, 25°55′N; 80°07′W) along the east coast of Florida, USA, during 6–10 March 2001. Reciprocal transplants at the northern site were used to evaluate the plasticity of photosynthetic patterns and pigment absorption spectra and to gain insights into the mechanisms responsible for variations in the observed depth-distribution patterns. Subtidal-population Fv/Fm values were generally higher for H. johnsonii than for H. decipiens, at both sites. At the northern site, intertidal H. johnsonii had significantly lower Fv/Fm (0.494±0.138) than both subtidal H. johnsonii (0.696±0.045) and subtidal H. decipiens (0.668±0.048). In contrast, at the southern site intertidal H. johnsonii had the highest Fv/Fm (0.663±0.047) and were the largest plants. Fv/Fm values of subtidal plants of both species decreased when they were transplanted into shallow, intertidal beds. Correspondingly, Fv/Fm increased for intertidal H. johnsonii transplanted into the subtidal, 2 m deep beds. Rapid light curves indicated that H. decipiens had lower maximum relative electron transport rates (RETRmax) than did H. johnsonii. In addition, the onset of photoinhibition occurred at lower irradiances for H. decipiens (537–820 μmol photons m⁻² s⁻¹) compared to H. johnsonii (1141–2670 μmol photons m⁻² s⁻¹). RETRmax values decreased for intertidal H. johnsonii transplanted into subtidal beds, but they increased for both species when transplanted from subtidal to intertidal beds. Absorption spectra for the acetone-soluble leaf pigments of intertidal H. johnsonii exhibited a dominant peak near 345 nm; this UV peak was 30% lower for subtidal plants. Pigment absorption spectra for H. decipiens lacked the 345 nm peak and absorbances, normalized to leaf pairs, were lower across the spectrum. Our results indicate that photosynthetic tolerance to higher irradiances and presence of UV-absorbing pigments (UVP) in H. johnsonii may allow this species to exploit the shallowest waters without competition from the closely related, but UVP-lacking H. decipiens.     

Evidence for a female sex pheromone mediating male trailing behavior in the red-sided garter snake, Thamnophis sirtalis parietalis

Summary. Male garter snakes locate females during the breeding season utilizing conspecific trailing behavior. It has been hypothesized that the female-derived chemical cue responsible for mediating male reproductive trailing behavior is the sexual attractiveness pheromone, a previously characterized contact pheromone responsible for releasing male courtship behavior. To examine this hypothesis, we tested the response of male red-sided garter snakes, Thamnophis sirtalis parietalis, to pheromone trails produced by males, females and ‘she-males’. She-males are a small subset of males in the natural population that are morphologically and behaviorally similar to other males except that they produce and express the sexual attractiveness pheromone during the breeding season. When tested on a Y-maze, males were found to detect and follow the skin lipid trails of females and she-males, but displayed no behavioral responses to male trails. In addition, males were unable to discriminate between she-male and female trails when given a choice. These results are consistent with the hypothesis that the sexual attractiveness pheromone is the chemical cue primarily utilized by males to mediate reproductive trailing behavior.     

On the effective hydraulic conductivity and macrodispersivity for density-dependent groundwater flow

In this paper, semi-analytical expressions of the effective hydraulic conductivity ( $K^{E})$ and macrodispersivity ( $\alpha ^{E})$ for 3D steady-state density-dependent groundwater flow are derived using a stationary spectral method. Based on the derived expressions, we present the dependence of $K^{E}$ and $\alpha ^{E}$ on the density of fluid under different dispersivity and spatial correlation scale of hydraulic conductivity. The results show that the horizontal $K^{E}$ and $\alpha ^{E}$ are not affected by density-induced flow. However, due to gravitational instability of the fluid induced by density contrasts, both vertical $K^{E}$ and $\alpha ^{E}$ are found to be reduced slightly when the density factor ( $\gamma $ ) is less than 0.01, whereas significant decreases occur when $\gamma $ exceeds 0.01. Of note, the variation of $K^{E}$ and $\alpha ^{E}$ is more significant when local dispersivity is small and the correlation scale of hydraulic conductivity is large.     

Morphology of submarine channel-levee systems in the eastern Bay of Bengal near Andaman region

Multibeam echo-sounder (MBES), sub-bottom profiler, singlebeam tracks and public-domain bathymetry geophysical datasets were analyzed in a Geographic Information System (GIS) for accuracy assessment and further used to update the previous map (Curray et al. Mar Pet Geol 19: 1191–1223, 2003) of submarine channel-levee systems in the eastern Bengal Fan near the Andaman region. Comparative analysis of singlebeam with MBES indicated 2.8 % of root-mean-square difference in bathymetry, and could clearly bring out distinct submarine channel profiles. The channel map revealed that the previously named E6 [updated as E7(1a)] and E7 [updated as E7(1b)] channels emanate from the middle and lower Bengal Fan, respectively and merge together at 91.28°E, 10.64°N where they form a second order channel [E7(2)] that flows southward along the east of Ninety-east Ridge. Similarly, two first order channels [E6(1a) and E6(1b)] emanate from the lower Bengal Fan which merge together at 88.78°E, 06.92°N to form a second order channel [E6(2)] that flows along the west of Ninety-east Ridge towards the equator. This channel was previously thought to be linked to the middle Bengal Fan. High-resolution MBES tracks over the channel shows extensive meandering patterns with the channel gently deepening and widening towards south. Variations in the morphology and stratigraphy indicate that the E7 channel is characterized by a curvilinear course, with higher observed sinuosity wherever gradient decreases.     

Ecology of a corallivorous gastropod,<Emphasis Type="Italic"> Coralliophila abbreviata</Emphasis>, on two scleractinian hosts. II. Feeding,respiration and growth

Coralliophila abbreviata is a corallivorous gastropod that has been observed to cause large feeding scars on reef-building corals on Floridian and Caribbean reefs. We detected differences in the population structure (length-frequency distribution and sex ratios) of C. abbreviata populations living on two coral host taxa, Acropora palmata and Montastraea spp., in the Florida Keys in a previous study. We hypothesize that diet (host) has a major influence on snail population structure and, thus, we characterize metabolism, feeding and growth for snails residing on these coral taxa. Here, we present results of a reciprocal transplant experiment demonstrating that the taxon of the host influences snail growth rates, as indicated by changes in shell and body tissue weight. Regardless of the host from which they were drawn, snails resident on A. palmata grew faster than those resident on Montastraea spp. Thus, diet influences snail population structure. However, the tissue of Montastraea spp. provides more N and C per area of tissue than that of A. palmata. Respiration rates and tissue composition of snails collected from the two host taxa did not differ. Therefore, snails feeding on Montastraea spp. should have to consume less tissue per day to satisfy their metabolic requirements compared to snails feeding on A. palmata. Feeding rates for snails on A. palmata were measured in the laboratory over 48 h (1–9 cm² coral tissue snail⁻¹ day⁻¹) and estimated from feeding scars observed in the field (weekly mean rate of 1.07 cm² coral tissue snail⁻¹ day⁻¹). The lack of definition of snail feeding scars on Montastraea spp. required the calculation of coral tissue consumption rates based on estimated minimum carbon requirements. Calculated feeding rates for C. abbreviata were 0.13–0.88 cm² coral tissue day⁻¹ snail⁻¹, when feeding on Montastraea spp., and 0.44–3.28 cm² coral tissue day⁻¹ snail⁻¹, when feeding on A. palmata. The calculated range for the latter is consistent with measured rates. Thus, C. abbreviata exhibits high variation in growth parameters in response to environmental variability and/or food source. At mean levels of snail density on reefs off Key Largo, Fla., 20% of A. palmata colonies lose between 1.32 and 9.84 cm² tissue day⁻¹, while 50% of Montastraea spp. colonies lose between 1.04 and 7.04 cm² tissue day⁻¹. Together with published coral tissue regeneration rates, these results suggest that if sustained, such rates of predation could have a serious effect on the viability of these coral populations on Florida's reefs.     

Feeding factors for the sea anemone Anthopleura midorii

The carnivorous feeding behavior of the sea anemone Anthopleura midorii was found to be a sequence of successive feeding motions, which consisted of several separate actions: (1) tentaculation on any solid matter; (2) retention of prey by tentacles; (3) mouth opening; (4) ingestion of food; (5) digestion of food; (6) extrusion of indigestible waste material. Hot water extract of a natural prey induced the entire feeding sequence when extract was given in the form of an artificial food by mixing with -potato starch and water. The fractionated extract induced only a limited feeding action. Several amino acids induced feeding. Alanine, glycine or histidine stimulated the retention of artificial food by tentacles, and proline evoked mouth opening. Cysteine or reduced glutathione (GSH) induced food ingestion. Unnatural food stuff such as -potato starch was ingestible, if an appropriate amount of a chemical substance was added.     

Diets of four deep-water scaphopod species (Mollusca) in the North Atlantic and the Nordic Seas

The buccal pouch contents of four deep-water scaphopod (Mollusca) species, Pulsellum affine, Pulsellum teres, Siphonodentalium lobatum and Polyschides olivi, collected in the North Atlantic and the Nordic Seas, were examined. The buccal pouches of the examined scaphopod species contained almost exclusively foraminifers, which agrees with previous studies on shallow and deep-water scaphopods. The scaphopods seemed to be engulfing at least some of the most common foraminifer species, which are distributed in the cold waters of the Nordic Seas or the temperate waters in the northernmost part of the North Atlantic. About half of the food species (30 foraminifer species) occurred in only one scaphopod species, nearly always in very low numbers, and seemed to be an unimportant food source. The remaining and more frequent food species occurred in two or more scaphopod species. A similarity tree was calculated with parsimony and presence–absence coding of the food species in the scaphopods. This resulted in the similarity tree: 100%{P. teres 79%[P. affine 70%(P. olivi and P. lobatum)]}, when branch support was measured with percentage jackknife stability. A general trend was found towards larger food items being consumed by larger scaphopod species, indicated by the positive correlation between the size of the scaphopods and the food species. It is suggested that microdistribution of the foraminifers and the large individual size of the foraminifers may be important factors in avoiding predation by scaphopods.     

Interspecific differences in fouling of two congeneric ascidians (Eudistoma olivaceum and E. capsulatum): is surface acidity an effective defense?

Ascidian specimens were collected from the Indian River Lagoon, Florida, USA, in November 1987. Eudistoma olivaceum (Van Name) was fouled by only two species of epifaunal invertebrates and the percent cover of epibionts was negligible. Colonies of E. capsulatum (Van Name) were fouled by up to 17 species of epifaunal invertebrates, epibionts covered an average of 12.5% of the surface area of these colonies. Extracts of E. olivaceum exhibited potent cytotoxic, antimicrobial and antiviral activity in laboratory bioassays, while the activity of extracts of E. capsulatum was insignificant. The toxicity of extracts of each ascidian was negatively related to the percent cover of fouling organisms. Surface acidity of each ascidian was positively related to the percent cover of epibionts: E. olivaceum was nearly neutral (pH=6), while E. capsulatum was highly acidic (pH=1 to 2). Larval settlement and growth of ancestrulae of the cheilostome bryozoan Bugula neritina (Linnaeus) were inhibited at very low concentrations of crude extract of E. olivaceum. Crude extracts of E. capsulatum inhibited settlement and growth of B. neritina only at concentrations of approximately an order of magnitude greater than those of E. olivaceum. Differences in the degree to which these congeneric ascidians are fouled is related to differences in the chemical defenses they possess. Acidity is not an effective inhibitor of settlement by epifaunal invertebrates.     

Avoiding predation: alarm responses of Caribbean sea urchins to simulated predation on conspecific and heterospecific sea urchins

Alarm responses to the extracts of conspecifics and hetero-specifics were measured for the Caribbean sea urchins Echinometra viridis, E. lucunter, Lytechinus variegatus, L. williamsi, Tripneustes ventricosus, Diadema antillarum, and Eucidaris tribuloides collected along the Caribbean coast (9°3314N; 78°5523W) during October 1984 and July–December 1985. Responses to seawater and extracts of the gnathostomate echinoid Clypeaster sybdepressus were used as controls. The intensity of the response resulting from exposure to sea-urchin extracts was measured by: (1) the percentage of individuals that responded by moving away from the extract and/or towards shelter, and (2) the mean distance moved. Echinometra viridis, E. lucunter, and L. williamsi responded to sea-urchin extracts by moving towards nearby shelter sites. The distance that individuals of each species moved in the first minute following exposure to conspecific extracts was correlated with the distance that species moved from shelter while foraging. L. variegatus and D. antillarum, living in microhabitats not providing protection from predators, responded to extracts of conspecifics and heterospecifics by moving away from the direction of the extract. Eucidaris tribuloides did not exhibit alarm responses to the extracts of con- or hetero-specifics. E. tribuloides secures itself with its stout spines into protected sites within corals. Similarly, L. variegatus living in long, dense seagrass that provided protection from detection by predators, and D. antillarum occupying crevices, showed no alarm responses to extracts of conspecifics. Presumably, in these situations, sea urchins cannot increase their defenses against predation by moving away from an injured neighbor. T. ventricosus showed a weak response to extracts of L. variegatus, but no response to extracts of other species including conspecifics. The reasons for this lack of an alarm response are unclear. For the five species that demonstrated an alarm response to sea-urchin extracts, the intensity of the response varied depending on the type of extract used. L. variegatus, L. williamsi, and D. antillarum responded most strongly to extracts from conspecifics, while Echinometra viridis and E. lucunter responded strongly to extracts from both conspecifics and congeners. The weakest responses were shown to the extracts of T. ventricosus and Eucidaris tribuloides. Habitat overlap, overlap in predators, and phylogenetic relationships did not consistently explain patterns of alarm responses to the extracts of heterospecific sea urchins.     

Elysia timida (Risso, 1818) (Gastropoda, Opisthobranchia): relationship and feeding deterrence to a potential predator on the south-western Mediterranean coast

The relationship between the sacoglossan Elysia timida and the ornate wrasse Thalassoma pavo was studied in two laboratory experiments using artificial models. A feeding-preference experiment was conducted to determine whether mollusc extract deterred feeding by T. pavo, by using a "realistic" mollusc model (imitating the colour pattern of E. timida) coated with mollusc extract, and a reference model (without imitation or extract), and fishes collected from two locations. It was observed that fish approached, attacked and ate more reference models than mollusc models. A second feeding-preference experiment was designed with four different coloured models: "realistic" (W), green (G), red (R) and chequered (S) pattern. Both fish populations clearly rejected the S model, and differed in their colour preferences. Although both populations seemed to prefer the R and G models equally, the W model was clearly rejected by the fish that coexist with the mollusc at one site (Mazarrón), but was not rejected by the other population of fish which does not coexist with it (Cabo de Palos). Mazarrón fishes would identify the W model with the presence of a toxic compound during their coexistence, and therefore avoid attacking conspicuously coloured E. timida models as a response to their visual signals. Therefore, it was concluded that extract of E. timida is a deterrent for T. pavo, and its effect is sufficiently noxious that the fish tend to avoid it, so that the ability of the fishes to learn to recognise colours and identify certain colour patterns associated with obnoxious prey provides the molluscs the opportunity to survive by exhibiting a conspicuous coloration.     

Gonadal development and infrequent sex change in a population of the humbug damselfish,Dascyllus aruanus,in continuous coral-cover habitat

The expression of protogyny often differs among populations of a single species. The humbug damselfish, Dascyllus aruanus (Linnaeus), typically lives in spatially discrete groups of several individuals around live coral colonies and has been reported to be protogynous. The size and sexual composition of groups of this species, however, vary with the size of the coral patch or the degree of coral cover. The present study examined gonadal development and sexual pattern in a population of D. aruanus living in continuous coral-cover habitat. Fish were collected in Tumon Bay, Guam (13°31′N; 144°47′E), during a 2-week period in July and August 1996. Reflecting their distributions, small fish (n=54) were collected at depths of 1–2 m over continuous Porites spp. patches, and large fish (n=56) were collected at depths of 2–3 m over a continuous Acropora spp. patch. Gonadal development was examined histologically. Gonads of D. aruanus first developed an ovarian lumen and primary-growth stage oocytes. From this ovarian state or from more developed ovaries with cortical-alveolus stage oocytes, some gonads developed into testes through degeneration of oocytes and development of spermatogenic tissue. Developing spermatogenic tissue only occurred in gonads having pre-cortical alveolus stage oocytes, and the size of individuals with gonads of this type overlapped mainly with the size range of individuals with gonads containing only pre-vitellogenic oocytes (i.e. immature females). This suggested that functional female-to-male sex change was rare or absent in this population of D. aruanus. Moreover, the different habitat distributions of small and large fish suggest that sex determination in immature fish occurs in the absence of adults.     

Depth-independent reproductive characteristics for the Caribbean reef-building coral<Emphasis Type="Italic"> Montastraea faveolata</Emphasis>

Photosynthetic, growth, and reproductive characters for colonies of the massive coral Montastraea faveolata were measured at 3-m-depth and 18-m-depth populations in the Florida Keys in 1993 to investigate reproductive behavior across depth. I tested the hypothesis that reproductive traits would exhibit depth-related decreases similar to those documented for photosynthetically derived energy availability and growth rate. Colonies at the 18 m site had significantly reduced access to photosynthetically derived energy compared to colonies at 3 m depth. Linear skeletal extension rates were also reduced at the deep site (mean±SE; 3 m: 6.13 mm year⁻¹±0.35; 18 m: 3.44 mm year⁻¹±0.36; P<0.001). Contrary to expectations, depth did not affect most reproductive characters. Reproductive allocation, the amount of lipid invested in reproduction, was similar between depths (3 m: 3.74 mg lipid cm⁻²±0.55; 18 m: 3.88 mg lipid cm⁻²±0.62; P<0.8). Reproductive effort, the proportion of total lipid invested in reproduction, was also similar between sites (3 m: 41.4%±4.7; 18 m: 47.3%±7.12; P<0.163). Colonies within a depth did differ significantly in many gametic characteristics including eggs per gonad, total egg area, spermary area, total gonad area, and male allocation (the proportion of total gonad area invested in spermary tissue), but only total egg area differed between depths, and this was greater at 18 m (3 m: 55.63 μm²×10⁴±4.76; 18 m: 60.51 μm²×10⁴±3.41; P<0.035). Colonies at the two sites had similar polyp fecundity (egg production per polyp); however, a difference in polyp density between sites (3 m: 5.56 polyps cm⁻²±0.21; 18 m: 4.87 polyps cm⁻²±0.15; P<0.028) resulted in a significant reduction in area fecundity (egg production per square centimeter) at the 18 m site (3 m: 554 eggs cm⁻²±27.9; 18 m: 422 eggs cm⁻²±31.0; P<0.045). Thus, there was a depth-related fecundity cost arising from a change in colony architecture (i.e. polyp spacing) rather than a direct effect of depth on the number of eggs produced per polyp. Egg production per gonad was positively correlated between 1993 and 1994 (r=0.540, P<0.05), indicating that other reproductive characteristics may also be stable between years.