Defensive strategy of twoHypselodoris nudibranchs from Italian and Spanish coasts

Hypselodoris nudibranchs from different geographic areas (Spain and Italy) have been studied in order to investigate their general defensive strategy. Longifolin (1) and nakafuran-9 (2) are the main ichthyodeterrent allomones used by the mollusks to avoid predation. Evidence of their dietary origin is presented and the very effective strategy against predators, which includes secretion of allomones into the mucus and their storage into specific mantle dermal formations (MDFs), is also discussed.F.P.I.-M.E.C. Spanish fellowship (University of Barcelona) at the I.C.M.I.B.     

Chemical defense of a dorid nudibranch,Glossodoris quadricolor,from the red sea

The nudibranch,Glossodoris quadricolor (Doridacea) feeds on the red spongeLatrunculia magnifica, which grows in the reefs of the Gulf of Aqaba, Red Sea. The ichthyotoxic substance from the sponge, latrunculin B, was also indentified in the mucous secretion of the mollusk by TLC, indicating the use of this substance as defense allomone.     

Defensive secretions of three species ofAcilius (Coleoptera: Dytiscidae) and their seasonal variations as determined by high-pressure liquid chromatography

A rapid, sensitive, stable, and quantitative high-pressure liquid chromatographic technique was developed for the analysis of defensive secretions obtained from the pygidial and prothoracic glands of dytiscids. Methods were developed for both normal phase (Porasil) and reverse phase (Bondapak C₁₈) columns. The applicability of this technique was demonstrated when defensive compounds ofAcilius semiculcatus, A. sylvanus andA. mediatus were isolated, identified, and quantitated. No major differences were found in the composition of the defensive secretions between the three species. The seasonal defensive titer ofA. semisulcatus was determined from June through October 1977. The pygidial defensive agents (benzoic acid,p-hydroxybenzaldehyde, and methylp-hydroxybenzoate varied from 9.0 to 67.8 g and exhibited a maximum in July, and a steroid from the prothoracic gland varied from 7.1 to 33.2 g and was maximum in October.     

Chemical defense of common antarctic shallow-water nudibranchTritoniella belli eliot (Mollusca: Tritonidae) and its prey,Clavularia frankliniana rouel (Cnidaria: Octocorallia)

Extracts of the dorid nudibranchTritoniella belli and stoloniferan coralClavularia frankliniana were chromatographed and analyzed by¹H NMR and thin-layer chromatography. Three glycerol ethers were detected inT. belli, primarily 1-O-hexadecyl glycerol (chimyl alcohol). Chimyl alcohol was also detected after gradient flash chromatography and reverse-phase HPLC purification in the tissues ofC. frankliniana. The common omnivorous predatory Antarctic sea starOdontaster validus, a likely predator of benthic invertebrates, showed feeding deterrence to small cubes ofT. belli mantle tissue placed on the tube feet along the ambulacral feeding groove, while always extruding the cardiac stomach when presented with cubes of shrimp tissue of similar size. Filter-paper disks soaked in an aqueous shrimp solution and then dried were found to elicit a broad range of feeding behaviors inO. validus, including movement of the shrimp disk to the mouth, extrusion of the cardiac stomach, and the assumption of a humped feeding posture. Chimyl alcohol-treated shrimp disks caused significant feeding deterrence in sea stars when compared with control disks (solvent plus shrimp treated disks alone).T. belli andC. frankliniana appear to employ a defensive compound that has been found in a variety of temperate and tropical mollusks, where it has been demonstrated to deter fish predators. We provide evidence for further deterrent capabilities of chimyl alcohol and of its trophic relationship in the polar ecosystem of McMurdo Sound, Antarctica.     

Geographic Variation and Tissue Distribution of Endogenous Terpenoids in the Northeastern Pacific Ocean Dorid Nudibranch Cadlina luteomarginata: Implications for the Regulation of De Novo Biosynthesis

Gas chromatography (GC) analyses of whole animal skin extracts and individual tissue extracts obtained from specimens of Cadlina luteomarginata collected in British Columbia and southern California were used to determine if concentrations of the nudibranch's biosynthetic products—albicanyl acetate (1), cadlinaldehyde (2), and luteone (3)—vary significantly between two populations, among individuals of a population, and among body tissues of individual specimens. The major biosynthetic product, albicanyl acetate (1), has the same concentration in both British Columbia and California populations, while the British Columbia population contains greater total amounts of 2 and 3 than the California population. Within individuals from one population, the largest proportion of endogenous metabolites is in the dorsum, specifically in the mantle dermal formations and margins. The GC analyses show that across geographically separated populations and within geographically localized populations the concentration of endogenous metabolites is inversely correlated with availability of structurally similar compounds from dietary sources. This suggests that the de novo biosynthesis of defensive compounds might be regulated according to need.     

Defensive secretion ofTenebrio molitor (Coleoptera: Tenebrionidae)

The defensive secretion ofTenebrio molitor contains a mixture of 2-methyl-1,4-benzoquinone andm-cresol. The phenol had not previously been detected in the secretion, although some investigators reported presence of 2-ethyl-1,4-benzoquinone as a second component. We failed to detect the latter quinone in secretion samples from three laboratory populations ofT. molitor.Paper No. 100 of the seriesDefense Mechanisms of Arthropods; No. 99 is Storey et al.,J. Chem. Ecol., 17, 687–693 (1991).     

Chemical defense secretions of some species of Malaysian rhinotermitidae (Isoptera,Rhinotermitidae)

The defense secretions of the soldiers of the Malaysian rhinotermitid,Parrhinotermes aequalis (Havilandi) andP. pygmaeus (John),Termitogeton planus (Havilandi) andSchedorhinotermes malaccensis (Holmgren) consist mainly of vinyl ketones, whereas that ofProrhinotermes flavus (Bugnion & Popoff) gives (E)-1-nitropentadecene. The chemistry of the defense secretions ofParrhinotermes andTermitogeton is documented and based on their chemical relationships;Termitogeton shows a closer affinity to the Rhinotermitinae than Heterotermitinae.     

Sex attractant for three species of the genusOncocnemis: O. chandleri (Grt.),O. cibalis (Grt.), andO. mackiei (B. & Benj.) (Lepidoptera: Noctuidae)

Oncocnemis chandleri, O. cibalis, andO. mackiei were attracted to chemically baited traps in the field. In all three cases, (5E,7Z)-dodecadienyl acetate was a key component for attraction. Attraction ofO. chandleri to traps baited with the (5E,7Z)-dodecadienyl acetate was inhibited by addition of (Z)-7-dodecenyl acetate.O. cibalis required both (5E,7Z)-dodecadienyl acetate and (Z)-7-dodecenyl acetate for attraction. Electroantennogram responses for the three species are also reported.     

Fatty acids, tocols, and carotenoids in pulp oil of three sea buckthorn species (Hippophae rhamnoides, H. salicifolia, and H. tibetana) grown in the Indian Himalayas

Sea buckthorn berries from Hippophae rhamnoides, H. tibetana, and H. salicifolia were collected from the cold deserts of the Himalayas (Lahaul, Ladakh, and Spiti; India) and characterized in terms of the FA, carotenoid, tocopherol, and tocotrienol composition in their pulp oil. These varied from species to species. Total carotenoids ranged from 692 to 3420 mg/kg in pulp oils of fresh berries, and total tocols, from 666 to 1788 mg/kg. Hippophae salicifolia berries contained substantially lower amounts of pulp oil, with lower levels of carotenoids and tocopherols. There was little difference in the proportion of individual tocols in pulp among the three species. α-Tocopherol alone constituted 40–60% of total pulp tocols in berries. Pulp oils had palmitoleic acid (32–53%) as the most abundant FA followed by palmitic (25–35%), oleic (8–26%), linoleic (5–16%), and linolenic (0.6–2.6%) acids, with the highest deviation observed in the proportion of palmitoleic acid in these berries. Hippophae rhamnoides and H. tibetana contained the highest amount of the lipophilic carotenoids and tocols. Hippophae salicifolia berries had higher amounts of lipophobic constituents such as vitamin C and flavonols.     

Lipid components in anal scent sacs of three mongoose species (Helogale parvula,Crossarchus obscurus,Suricata suricatta)

Anal sac secretions of three social mongoose species (Helogale parvula, Crossarchus obscurus, andSuricata suricatta) were chemically analyzed by means of gas chromatography-mass spectrometry. Compounds with high molecular weights (greater than 250) were found to distinguish the three species. Differences in composition suggest a possible species-specific role in scent marking. MaleH. parvula had vitamin E present in the anal sac, whereas it was absent in the females. This suggests a possible sex-specific function of vitamin E inH. parvula. No differences in chemical composition were found between male and femaleS. suricatta. Ten compounds were found in femaleC. obscurus that were not present in the male.     

Evidence for chemical defense in tropical green algaCaulerpa ashmeadii (Caulerpaceae: Chlorophyta): Isolation of new bioactive sesquiterpenoids

Results of field feeding preference studies with 12 species of tropical green algae of the genusCaulerpa showed thatC. ashmeadii was preferred least by herbivorous fishes. Chemical investigations ofC. ashmeadii demonstrated the presence of high concentrations of sesquiterpenoid metabolites. The chemical isolation and structural elucidation of five majorC. ashmeadii metabolites, as well as the results of field feeding preference, antimicrobial, and ichthyotoxicity assays demonstrating the biological activities of these metabolites are reported here.     

Disturbance and reattachment behavior of sea anemonesCalliactis tricolor (Le Sueur): Temporal,textural and chemical mediation

Two hermit crabs,Dardanus venosus (Milne-Edwards) andPagurus pollicaris Say, have evolved mutualistic symbiotic relationships with sea anemones,Calliactis tricolor (Le Sueur). Anemones live on gastropod shells occupied by the crabs. Both partners are thought to participate in the transfer of the anemone to the crab's shell. However, neither species invariably exhibits transfer behavior when in contact with the other symbiont. Factors influencing transfer activity ofC. tricolor were studied. Anemone attachment is stimulated by disturbance and is time dependent. Anemones attached to shells more frequently immediately after the anemone was disturbed. Assays testing surface texture and surface composition showed that attachment activity of the sea anemone is dependent upon the organic matrix of the shell and is enhanced by texture. Attachment by anemones to shells with organic matrix removed is reduced, but is stimulated by adsorption of complex odor mixtures. Anemones respond to odor mixtures that signal food to crabs and to odor mixtures that stimulate shell investigation and shell switching in crabs. Thus,C. tricolor participates in shell transfer activity after disturbance. Behavior of the anemone is cued by texture and chemicals, including chemical mixtures that cause hermit crabs to change shells.     

Identification of cantharidin in false blister beetles (Coleoptera,Oedemeridae) from florida

Cantharidin, a potent vesicant and antifeedant, is identified for the first time in two oedemerid beetles from the western hemisphere. Amounts of the substance per beetle were found to range from 2 to 7 g inHeliocis repanda and from 15 to 35 g inOxycopis thoracica. Females had two to three times more cantharidin than males of the same species. Cantharidin loads of these beetles are sufficient to irritate human skin.     

Inhibition of larval settlement by natural products from the ascidian,Eudistoma olivaceum (Van Name)

Settlement bioassays with larvae of the cheilostome bryozoanBugula neritina were used to isolate and purify antifouling compounds from the ascidianEudistoma olivaceum (Van Name). Three inhibitors of larval settlement, two toxic and one nontoxic, were investigated. The toxic compounds accounted for approximately 0.4% of the organic fraction (on a dry weight basis) and were identified as eudistomins g and h, two of a number of alkaloids possessed byE. olivaceum. The nontoxic inhibitor of settlement was not characterized. Eudistomins g and h were effective inhibitors of larval settlement at concentrations as low as 0.5% of that present in the living animal.     

Effects of secondary metabolites from marine algae on feeding by the sea urchin,Lytechinus variegatus

A bioassay was developed to test the hypothesis that secondary metabolites from marine algae affect feeding by sea urchins. During experiments measuring chemoreception and gustation, feeding by the regular sea urchin,Lytechinus variegatus (Lamarck), was inhibited by extracts from the green marine alga,Caulerpa prolifera (Forsskal) Lamouroux andCymopolia barbata (Linneaus) Lamouroux. Cymopol, a monoterpene-bromohydroquinone component ofC. barbata, was partially responsible for the inhibited feeding observed in tests of theCymopolia crude extract. Caulerpenyne, an oxygenated sesquiterpene fromC. prolifera, was responsible for all of the urchin feeding inhibition observed in tests of theC. prolifera crude extract. Feeding was not affected by: (1) extracts from several otherCaulerpa species includingC. mexicana (Sonder) J. Agardh,C. ashmaedii Harvey,C. racemosa v.macrophysa (Kutzing) Taylor, andC. racemosa v.laetevirens (Montagne) Weber-van Bosse; (2) caulerpin, an indole-containing pigment isolated from all of theCaulerpa species exceptC. mexicana; and (3) an extract from the red marine alga,Gracilaria foliifera v.angustissima (Harvey) Taylor, which has no known secondary metabolites. Feeding inhibition was independent of the test diameter which correlated with the reproductive state of the urchins. Feeding inhibition was also independent of the starvation periods between experiments, and the temperature and salinity in ranges tolerated byL. variegatus obtained from the Florida Gulf Coast. The data strongly suggest that at least one alga,Caulerpa prolifera, is chemically defended against a dominant omnivore in its community.     

Structures,absolute configurations,and syntheses of volatile signals from three sympatric ant-lion species,Euroleon nostras,Grocus bore,andMyrmeleon formicarius (Neuroptera: Myrmeleontidae)

The thoracic gland of the ant-lionEuroleon nostras was found to contain nerol oxide (1a) and (Z)-6-undecen-2-ol (nostrenol,3) while the speciesGrocus bore contained 10-homonerol oxide (1b) and nostrenol (3). Nerol (2a) and 10-homonerol (2b) were found in a third species,Myrmeleon formicarius. 10-Homonerol, racemic 10-homonerol oxide, and racemic as well as (R)- and (S)-nostrenol were synthesized. The nerol oxide ofE. nostras and the 10-homonerol oxide ofG. bore were found to be racemic, while both species contained optically pure (R)-nostrenol (28).Visiting research scientists from Institute of Photographic Chemistry, Academia Sinica, Beijing, China (H. H.-Z.) and Shanghai Institute of Organic Chemistry, Academia Sinica, 345 Ling Lu, Shanghai, China (L. G.-Q.).     

Sex pheromone components of three species ofSemiothisa (Geometridae), (Z,Z,Z)-3,6,9-heptadecatriene and two monoepoxydiene analogs

Adult males ofSemiothisa signaria dispuncta (Walker) were attracted to field traps baited with (Z,Z,Z)-3,6,9-octadecatriene and (Z,Z)-6,9-cis-3,4-epoxy-octadecadiene. However, analyses of sex pheromone gland extracts of females of this species by GC-MS and by GC in combination with an electroantennograph detector (GC-EAD) showed the pheromone to be comprised of a mixture of the next lower homologs: (Z,Z,Z)-3,6,9-heptadecatriene and (Z,Z)-6,9-cis-3,4-epoxy-heptadecadiene. Blends of these two C₁₇ compounds were subsequently found to be more attractive to males in the field than the corresponding C₁₈ mixtures. Sex pheromones of two otherSemiothisa species were also found to contain C₁₇ components. (Z,Z,Z)-3,6,9-Heptadecatriene, detected by GC-EAD analysis of a female abdominal tip extract ofS. bicolorata (Fabricius), attracted conspecific males, and this attraction was significantly reduced by additions of (Z,Z)-6,9-cis-3,4-epoxyheptadecadiene, the major pheromone component ofS. signaria dispuncta, to the lure. (Z,Z)-3,9-cis-6,7-Epoxy-heptadecadiene was detected by GC-EAD analysis as the primary male antennal stimulatory component present in abdominal tip extracts ofS. ulsterata (Pearsall), and males of this species were attracted to traps baited with this epoxide. Each of these three C₁₇ compounds constitute previously unknown lepidopteran sex pheromone components. Blends of (Z,Z, Z)-3,6,9-heptadecatriene and (Z,Z)-3,9-cis-6,7-epoxyheptadecadiene attracted males of a fourth species,S. delectata Hulst, but no females of this species were obtained to permit analysis of its sex pheromone. The occurrence of (Z,Z,Z)-3,6,9-heptadecatriene inS. neptaria (Guenee) females was indicated by GC-MS analysis of an abdominal tip extract; however, no males were attracted to any of the fielded mixtures containing this hydrocarbon.     

Chemical protection of a fish (Abudefduf leucogaster bleeker) by a soft coral (Litophyton viridis May)

Around Laing Island (Bismarck Sea), juveniles of the fishAbudefduf leucogaster are associated with the alcyonarianLitophyton viridis which, on mechanical stimulation, can release a potent ichthyotoxin and appears to be accordingly disliked by large predators. The fish has no special immunity to high levels of toxin but is affected more slowly than others. This has been interpreted in terms of an original strategy wherebyA. leucogaster plays its long reaction time against the diffusion of the toxin, allowing the fish to remain around the soft coral and benefit from indirect chemical protection. Possible biological implications of the toxin release are discussed.Laing Island Biological Station contribution No. 39.     

Aggregation pheromones inDryocoetes affaber (Mann.) (Coleoptera: Scolytidae): stereoisomerism and species specificity

Chemical analysis of whole body extracts and volatiles produced by feeding malesDryocoetes affaber (Mann.) disclosed (+)-exo-brevicomin and (+)-endo-brevicomin [(+)EXOB and (+)ENDOB], as the major insect-produced potential pheromones. Laboratory bioassays and field-trapping experiments demonstrated that (+)ENDOB is the main pheromone component, and (-)ENDOB has an inhibiting effect. EXOB either as (+) or (±) appears to be a multifunctional pheromone. It has a synergistic effect in blends of EXOB and ENDOB in ratios up to 1:1, and it is inhibitory at higher ratios. (-)EXOB was inactive. The most attractive blend forD. affaber was a 1:2 blend of (+)EXOB and (+)ENDOB. When this blend was compared with a 9:1 blend, the best known blend forDryocoetes confusus Swaine, the responses by beetles of each of the two species were highly specific, providing evidence for pheromonal exclusion between the two congenerics. We conclude that the combined effect of chirality and the ratio of geometrical isomers of brevicomin determines both the level of response and the species-specificity of the chemical signal inD. affaber.On educational leave from the Escuela Nacional de Ciencias Biológicas. I.P.N. Depto. de Zoología, Prol. Carpio y Plan de Ayala, México 11340 D.F. México.     

Butenolides in small ermine moths,Yponomeuta spp. (Lepidoptera: Yponomeutidae), and spindle-tree,Euonymus europaeus (Celastraceae)

A new butenolide, isosiphonodin [3-hydroxymethyl-2(5H)-furanone], along with a trace of siphonodin [4-hydroxymethyl-2(5H)-furanone], was isolated from fifth-instar larvae of the small ermine mothYponomeuta cagnagellus. Leaves of its host plant spindle-tree,Euonymus europaeus, were found to contain the same two butenolides with siphonodin being present as the major compound. TLC showed that isosiphonodin was also present in larvae or pupae of six other small ermine moths which did not feed on spindle-tree. InY. cagnagellus butenolides might be plant derived, while isosiphonodin in the other investigated small ermine moths is probably synthesized by the insect. The possible role of butenolides in the chemical defense of small ermine moths is discussed.