Tunicate Species Research Articles

From One to Many and Back Again: A Systemic Signal Triggers Tunicate Regeneration

From One to Many and Back Again: A Systemic Signal Triggers Tunicate Regeneration

The inhibitory effect of biofilms produced by wild bacterial isolates to the larval settlement of the fouling ascidia Ciona intestinalis and Pyura praeputialis

Marine biofouling is a present and potentially increasing future problem at molluscan culture centres. The problem is highly variable, exists on different scales, and its negative impact on cultured organisms and related economic losses at these centres has not been significantly controlled. One approach to fouling control has been the incorporation of natural substances into anti-fouling paints which inhibit the settlement of common fouling organisms. The main objective of the present study was the isolation of naturally occurring substances from marine bacteria which were inhibitory to the settlement of Ciona intestinalis and Pyura praeputialis, two tunicate species causing serious fouling problems in scallop culture systems in Chile. Numerous bacterial strains were isolated from microfouling on natural and artificial substrates submerged in the sea; of 73 strains isolated, 20% demonstrated inhibitory effects on the settlement of the larvae of the above cited tunicates. The inhibitory substances produced by the active bacteria were extracellular, and could be incorporated in an inert matrix (Phytagel TM ) without losing their inhibitory properties. Some properties of the inhibitory substance isolated from bacterial strain Clon Nil-LEM ( Alteromonas sp) included thermostability, MW C. intestinalis ), and undiminished inhibitory activity when incorporated in the inert matrix.

Antimalarial activity from three ascidians: an exploration of different marine invertebrate phyla

Recent research suggests that marine organisms may produce compounds with activity against malaria parasites. Of a total of 27 aqueous extracts from different marine species, collected on the northwest Cuban coast, 20 were considered as showing no significant activity against Plasmodium falciparum F32, with minimum inhibitory concentrations (MIC) >500 microg/ml, while seven extracts (MIC < or =500 microg/ml) were selected for further investigation by determining their selectivity indices and in vivo antimalarial activity. Three species of tunicates were chosen, as more than 50% reduction of P. berghei parasitaemia was produced after administration of 250 or 500 mg/kg of their crude extracts into infected mice. The aqueous extracts of Microcosmus goanus, Ascidia sydneiensis and Phallusia nigra were partitioned between water and n-butanol; the organic phases inhibited P. falciparum growth by 50% at concentrations of 17.5 microg/ml, 20.9 microg/ml and 29.4 microg/ml respectively. In general, these results are similar to those of most ethnobotanical surveys. Further chemical studies are being undertaken in order to isolate new antimalarial compounds from these Caribbean tunicates.

Immunochemical recognition of gelatinous zooplankton: an application to identify the origin of the ‘barrel’: made by the pelagic amphipod, Phronima sedentaria

A first trial to recognize gelatinous zooplankton using an immunochemical method was carried out. Polyclonal antibodies (rabbit IgG) raised against three cnidarians and four pelagic tunicates were purified and tested for their specificity against various sympatric zooplankton and micronekton. While antibodies to cnidarians were species-specific or at least distinguishable by means of the patterns of the bands appearing, antibodies to the pelagic tunicates cross-reacted with the antigen from the other tunicate species although these did not cross-react with other animal taxa. These results suggest that the present cnidarian antibodies can be applied to the predator identification at the species level. Antibodies to pelagic tunicates would also be effective tools for basic scanning at higher taxonomic levels, i.e. pelagic tunicates or other animals. The antibodies were applied to the identification of the ‘barrel’ of Phronima, indicating that the ‘barrels’ originated from tunicates but not from cnidarians. The present study indicates that the immunochemical method using polyclonal antibodies is a powerful tool for the detection of gelatinous zooplankton.

Non-neural ectoderm is really neural: evolution of developmental patterning mechanisms in the non-neural ectoderm of chordates and the problem of sensory cell homologies

In chordates, the ectoderm is divided into the neuroectoderm and the so-called non-neural ectoderm. In spite of its name, however, the non-neural ectoderm contains numerous sensory cells. Therefore, the term "non-neural" ectoderm should be replaced by "general ectoderm." At least in amphioxus and tunicates and possibly in vertebrates as well, both the neuroectoderm and the general ectoderm are patterned anterior/posteriorly by mechanisms involving retinoic acid and Hox genes. In amphioxus and tunicates the ectodermal sensory cells, which have a wide range of ciliary and microvillar configurations, are mostly primary neurons sending axons to the CNS, although a minority lack axons. In contrast, vertebrate mechanosensory cells, called hair cells, are all secondary neurons that lack axons and have a characteristic eccentric cilium adjacent to a group of microvilli of graded lengths. It has been highly controversial whether the ectodermal sensory cells in the oral siphons of adult tunicates are homologous to vertebrate hair cells. In some species of tunicates, these cells appear to be secondary neurons, and microvillar and ciliary configurations of some of these cells approach those of vertebrate hair cells. However, none of the tunicate cells has all the characteristics of a hair cell, and there is a high degree of variation among ectodermal sensory cells within and between different species. Thus, similarities between the ectodermal sensory cells of any one species of tunicate and craniate hair cells may well represent convergent evolution rather than homology.

Molecular phylogeny of the protochordates: chordate evolution

The deuterostomes are a monophyletic group of multicellular animals that include the Chordata, a phylum that exhibits a unique body plan within the metazoans. Deuterostomes classically contained three phyla, Echinodermata, Hemichordata, and Chordata. Protochordata describes two invertebrate chordate subphyla, the Tunicata (Urochordata) and the Cephalochordata. Tunicate species are key to understanding chordate origins, as they have tadpole larvae with a chordate body plan. However, molecular phylogenies show only weak support for the Tunicata as the sister-group to the rest of the chordates, suggesting that they are highly divergent from the Cephalochordata and Vertebrata. We believe that members of the Tunicata exhibit a unique adult body plan and should be considered a separate phylum rather than a subphylum of Chordata. The molecular phylogeny of the deuterostomes is reviewed and discussed in the context of likely morphological evolutionary scenarios and the possibility is raised that the ancestor of the Tunicata was colonial. In this scenario, the colonial tadpole larva would more resemble an ancestral chordate than the solitary tadpole larva. In contrast, the true chordates (vertebrates and cephalochordates) would have evolved from filter-feeding benthic worms with cartilaginous gill slits, similar to extant enteropneust hemichordates.

Checking the landing zone: do invertebrate larvae avoid settling near superior spatial competitors?

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 280:239-247 (2004) - doi:10.3354/meps280239 Checking the landing zone: Do invertebrate larvae avoid settling near superior spatial competitors? Stephan G. Bullard1,3, Robert B. Whitlatch1,*, Richard W. Osman2 1Department of Marine Sciences, University of Connecticut, Groton, Connecticut 06340, USA 2Smithsonian Environmental Research Center, PO Box 28, 647 Contees Wharf Road, Edgewater, Maryland 21037, USA 3Present address: University of Hartford Hillyer College, 200 Bloomfield Av., West Hartford, Connecticut 06117, USA *Corresponding author. Email: robert.whitch@ucom.edu ABSTRACT: It has been hypothesized that larvae of benthic marine invertebrates may reduce their risk of post-settlement competition by avoiding superior competitors during settlement. Few studies, however, have directly compared the levels of larval settlement close to and away from established competitors. We conducted experiments in the New England subtidal to determine whether larvae of fouling organisms would avoid substrata (100 cm2 PVC panels) with established adult colonies of the tunicates Botryllus schlosseri, Botrylloides violaceus, and Diplosoma listerianum compared to control substrata without tunicates. After panels had been exposed for 1 wk in the field, we assessed larval settlement on the entire surface of panels and within 1 cm of established tunicate colonies. We also monitored the fate of larvae that settled near established tunicates to determine if different tunicate species posed different risks of overgrowth to newly settled juveniles. Pair-wise comparisons revealed only 1 significant difference (out of 48 total analyses) when we examined levels of settlement on panels with tunicates relative to bare controls. We also found no significant differences in the number of settlers overgrown by different tunicate species. Thus, our results suggest that invertebrate larvae do not avoid settling near established dominant competitors (i.e. colonial tunicates). These results are in contrast to a previous study which had shown that larvae of competitively inferior species avoided settling near B. schlosseri. KEY WORDS: Ascidians · Competition · Cues · Larvae · Overgrowth · Settlement · Tunicates Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 280. Online publication date: October 14, 2004 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2004 Inter-Research.

Six novel gonadotropin-releasing hormones are encoded as triplets on each of two genes in the protochordate, Ciona intestinalis.

GnRH is the key regulator of the reproductive axis in vertebrates, but little is known about GnRH before the origin of vertebrates. We have identified two genes encoding GnRH in a protochordate, Ciona intestinalis, thought to be related to the ancestral animal that gave rise to vertebrates. Each gene, Ci-gnrh1 and Ci-gnrh2, encodes in tandem three GnRH peptides, each of which is unique compared with known forms. Ci-gnrh1 encodes three peptides and contains no introns, whereas Ci-gnrh2 encodes three more peptides but has two introns. This is the first report in which more than one GnRH peptide is encoded on a single gene. The Ciona genes reveal consensus promoter elements that are conserved compared with human GNRH1. Both tunicate genes are expressed as mRNA early and throughout development, measured at the stages of four-cell, gastrulation, tail release, and tail resorption. In a closely related tunicate species, Ciona savignyi, we used in silico analysis to identify two similar genes encoding six peptides, only one of which is unique compared with C. intestinalis. Immunohistochemistry showed that at least one GnRH peptide was in the nerve net that surrounds the dorsal strand. Synthetic forms of the seven novel tunicate peptides induced release of gametes in adult tunicates. In contrast, the peptides did not activate the human GnRH-I receptor or cause release of LH in a rat pituitary cell assay. These data provide insight into the structural evolution of the GnRH peptides and their genes and show a functional role for GnRH in tunicate spawning.

Phylogeny of Tunicata inferred from molecular and morphological characters

The phylogeny of the Tunicata was reconstructed using molecular and morphological characters. Mitochondrial cytochrome oxidase I ( cox1) and 18S rDNA sequences were obtained for 14 and 4 tunicate species, respectively. 18S rDNA sequences were aligned with gene sequences obtained from GenBank of 57 tunicates, a cephalochordate, and a selachian craniate. Cox1 sequences were aligned with the sequence of two ascidians and a cephalochordate obtained from GenBank. Traditional, morphological, life history, and biochemical characters of larval and adult stages were compiled from the literature and analyzed cladistically. Separate and simultaneous parsimony analyses of molecular and morphological data were carried out. Aplousobranch ascidians from three different families were included in a molecular phylogenetic analysis for the first time. Analysis of the morphological, life history, and biochemical characters results in a highly unresolved tree. Aplousobranchiata form a strongly supported monophylum in the analysis of the 18S rDNA data, the morphological data, and the combined data set. Cionidae is not included in the Aplousobranchiata but nests within the Phlebobranchiata. Appendicularia (=Larvacea) nest within the ‘Ascidiacea’ as the sister taxon of Aplousobranchiata in the parsimony analysis of the 18S rDNA data and the combined analysis. A potential morphological synapomorphy of Aplousobranchiata plus Appendicularia is the horizontal orientation of the larval tail. In the 18S rDNA and the combined analysis, Thaliacea is included in the ‘Ascidiacea’ as the sister group to Phlebobranchiata. Pyrosomatida is found to be the sister taxon to the Salpidae in analyses of 18S rDNA and combined data, whereas the analysis of the morphological data recovers a sister group relationship between Doliolidae and Salpidae. Results of cox1 analyses are incongruent with both the 18S rDNA and the morphological phylogenies. Cox1 sequences may evolve too rapidly to resolve relationships of higher tunicate taxa. However, the cox1 data may be useful at lower taxonomic levels.

Pitx genes in Tunicates provide new molecular insight into the evolutionary origin of pituitary

We have initiated a project aimed at documenting molecular and cellular changes underlying the emergence of the hypothalamo-hypophyseal axis in Chordates. Considering the phylogenetic position of Tunicates and the ‘pan-hypophyseal’ expression pattern of Pitx genes in Vertebrate pituitary, we searched for a Pitx-related homeobox gene in the ascidian Ciona intestinalis, and identified Ci-Pitx ( Ci ona intestinalis Pit uitary homeobo x gene). We also isolated Cs-Pitx and Bs-Pitx, the Ci-Pitx respective counterparts of Ciona savignyi and Botryllus schlosseri, two other Tunicate species. Ci-Pitx mRNA encodes a putative protein exhibiting the diagnostic K50-Paired-class homeodomain and a conserved C-terminal Aristaless domain. Embryonic expression pattern of Ci-Pitx revealed a conserved expression domain in the anterior neural ridge and subsequently in the pharyngeal primordium, defined in Vertebrates as the stomodeal ectomere, which encompasses the presumptive pituitary territory. This shows that expression at early steps of pituitary development is a feature of Pitx-related genes that was already present in the last common ancestor of Chordates.

Polar constituents of the ascidia Botryllus schlosseri

Eighteen compounds were identified by GC-MS of their trimethylsilyl derivatives in n-butanolic extract from the biomass of Botryllus schlosseri. Three of them, 5-oxoproline, 5-hydroxyhydantoin, and kinurenic acid, were found in marine invertebrates for the first time. In addition to cellulose, the biomass was also shown to contain complex water-soluble sulfated polysaccharides. These were extracted and fractionated, and sulfate content and monosaccharide composition were determined in the fractions; fucose, xylose, galactose, mannose, glucose, glucosamine, galactosamine, and uronic acids were found. Unlike several other tunicate species, Botryllus schlosseri does not seem to contain any simple galactan sulfate.

Brachyury (T) gene expression and notochord development in Oikopleura longicauda (Appendicularia, Urochordata).

Appendicularia (Larvacea) is a subgroup of Urochordata (Tunicata) comprised of holoplanktonic organisms that retain their tailed architecture throughout their life history, while other tunicates, including ascidians and doliolids, resorb the tail after metamorphosis. In order to investigate the characteristics of the appendicularian unresorbed notochord, we isolated a partial genomic clone and a full-length cDNA sequence homologous to the mouse Brachyury (T) gene from the appendicularian Oikopleura longicauda. Brachyury is known to be predominantly expressed in the notochord cells and plays an important role in their differentiation in other chordates. While phylogenetic analysis robustly supports the orthology of the isolated Brachyury gene, the exon-intron organization found in the genomic clone was distinct from that well-conserved among other T-box genes. In addition to a detailed observation of notochord development in living specimens, whole-mount double in situ hybridization was carried out using a Brachyury probe along with a muscle actin probe. The Brachyury transcripts were found in the notochord of the tailbud embryos and persisted into later stages. The present study highlights characteristics of notochord development in the appendicularian. Furthermore, these results provide basic knowledge for comprehensive understanding of the cellular- and molecular-based mechanisms needed to build the characteristic cytoarchitecture of notochord that varies among tunicate species.

A C-type lectin from the Tunicate, Styela plicata, that modulates cellular activity

Previous studies have identified proteins from tunicates (invertebrate members of the Phylum Chordata) that have physicochemical and functional properties similar to those of the inflammatory cytokine, interleukin 1 (IL-1). Here we characterize one of those proteins from the tunicate, Styela plicata, that can stimulate tunicate and mammalian cell proliferation, activate phagocytosis, increase interleukin 2 (IL-2) secretion by mammalian peripheral blood mononuclear cells and enhance IL-2 receptor (IL-2R) expression by mammalian EL-4.IL-2 cells. Partial amino acid sequence data showed that the S. plicata protein resembles three C-type lectins (TC14, TC14-1 and TC14-2) from a closely related tunicate species, Polyandrocarpa misakiensis. Its similarity to carbohydrate recognition domains (CRDs) from P. misakiensis lectins suggests that the S. plicata protein modulates the activities of mammalian immunocompetent cells by interacting with carbohydrate moieties of glycosylated cell surface receptors.

Insecticidal Activity of the Methanol Extracts of Some Tunicate Species against Aedes aegypti and Anopheles maculatus

The methanol extracts of seven species of Malaysian tunicates (Clavelina picta, Eudisma obscuratum, Didemnum molle, Atriolum robustum, Phallusia sp., Didemnum sp. and Aplidium sp.) were investigated for their insecticidal activity against Anopheles maculatus and Aedes aegypti. The mortality values of the extracts on the adult mosquitoes were dose-dependent and increased with exposure period. The tunicate extracts demonstrated significant insecticidal effect after 3 h exposure with LC 50 values ranging from 0.03 to 3.79 µg ml -1 against An. maculatus and from 0.02 to 2.49 µg ml -1 against Ae. aegypti. The extracts of Didemnum sp. and Phallusia sp. were highly effective against Ae. aegypti with LC 50 values of 0.02 and 0.03 µg ml -1, respectively, while the extracts of Eu. obscuratum, Aplidium sp. and At. robustum showed similarly low LC 50 values against An. maculatus. The values were comparable to that of DDT, indicating that the tunicate extracts were as effective as the synthetic insecticide in killing the mosquitoes.

Long-term changes (1979–1994) in two coastal benthic communities (English Channel): analysis of structural developments

The long-term variations of two coastal benthic communities (Eastern English Channel, France) were studied between 1979 and 1994 by means of factor correspondence analysis (FCA), trophic structure and rank-frequency diagrams (RFD). FCA identified periods of relative homogeneity and periods of strong variation in the structure of the two communities. The first community, established on heterogeneous sand, showed a multi-annual cycle linked to grain-size variations in the sediment. As passive supplies of organic matter were not important and suspension feeders could hardly live in these conditions, the community remained poor and stable and was dominated by deposit-feeders and carnivores. The other one, a rich and diverse mussel ( Mytilus edulis) bed, showed great variations in the abundance of the main species which generated the enrichment of the community by its suspension-feeding behaviour (biodeposition). Beyond these variations, the community remained stable until 1990 as no continuous trend or permanent change could be seen. Since 1990, no recruitment of M. edulis occurred and the relative dominance of suspension feeders, as well as the number of species, strongly decreased. During the following years, several species of tunicates (sessile suspension feeders with gregarious recruitment) recruited and partly took the ecological niche of M. edulis but they did not induce an increase of biodeposition and the previous richness was not restored. After a strong and rapid shift in the structure, a new equilibrium has been established within the community.

Genetic Evolution of Morphology

Two commentaries in the 4 July issue, by their contrast, inadvertently point to a missing element in most discussions of the evolution of animal form. In his Perspective “Which came first, the hypha or the yeast?” ([p. 52][1]), P. T. Magee draws the lesson from a report by B. R. Braun and A. D. Johnson ([4 July, p. 105][2]) that the existence of a simple genetic switch between the budding yeast and the thread-like hypha morphologies of Candida albicans suggests that “there is no ‘default’ form for this organism.” This seems reasonable: C. albicans is thought of as polymorphic, with numerous forms being consistent with a single genetic constitution. The choice between alternative forms in such cases may depend on epigenetic or environmental factors, although, in principle, heritable genetic change could bias such choices, leading to distinct morphological varieties. This view may be compared with one presented in the Special News Report by Elizabeth Pennisi and Wade Roush “Developing a new view of evolution” ([4 July, p. 34][3]), in which they discuss, among other things, recently published evidence that a gene called manx distinguishes a species of tunicates whose larvae lack tails from a related species whose larvae develop them (B. J. Swalla and W. R. Jeffery, Reports, 15 Nov., 1996 p. 1205). We are told in the News article that the result “raises the possibility that a single genetic change could be responsible for the innovation that led to a tail in primitive vertebrates.” The attribution of ineffable creative power to individual genes is not an isolated instance, but can be traced back at least to the erroneous “unit character” model of Mendelism propounded by some early geneticists ([1][4]) and lives on in some precincts of developmental and evolutionary biology (Letters, C. Nielsen, [5 Sept., p. 1422][5]). Investigators of the regulation of morphogenesis of protists and bacteria seem relatively resistant to this form of mystification, as exemplified by the recent work on C. albicans [see also ([2][6])]. Genetic absolutism does not take into account that the correspondence of a given genotype to a nearly unique morphological phenotype seen in modern animals may itself be a product of evolution: in the absence of more recently evolved redundancies and other back-up mechanisms, the earliest animals may have been as polymorphic, or more so, as C. albicans . If true, this would imply that once the metazoa emerged, the genetic evolution of morphology would have been implemented not so much by the origination of novelty as by the selective stabilization of particular forms from those within the ancestral animals' morphological repertoire ([3][7]). 1. [↵][8]L. C. Dunn, A Short History of Genetics (McGraw-Hill, New York, 1965). 2. [↵][9]J. T. Bonner, Life Cycles: Reflections of an Evolutionary Biologist (Princeton Univ. Press, Princeton, NJ, 1993). 3. [↵][10]1. S. A. Newman , J. Evol. Biol. 7, 467 (1994). [OpenUrl][11][CrossRef][12][Web of Science][13] [1]: /lookup/doi/10.1126/science.277.5322.52 [2]: /lookup/doi/10.1126/science.277.5322.105 [3]: /lookup/doi/10.1126/science.277.5322.34 [4]: #ref-1 [5]: /lookup/doi/10.1126/science.277.5331.1421 [6]: #ref-2 [7]: #ref-3 [8]: #xref-ref-1-1 View reference 1 in text [9]: #xref-ref-2-1 View reference 2 in text [10]: #xref-ref-3-1 View reference 3 in text [11]: {openurl}?query=rft.jtitle%253DJ.%2BEvol.%2BBiol.%26rft.volume%253D7%26rft.spage%253D467%26rft_id%253Dinfo%253Adoi%252F10.1046%252Fj.1420-9101.1994.7040467.x%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [12]: /lookup/external-ref?access_num=10.1046/j.1420-9101.1994.7040467.x&link_type=DOI [13]: /lookup/external-ref?access_num=A1994NX82300005&link_type=ISI

On endostyle ultrastructure in two new species of doliolid-like tunicates

The endostyle is a glandular and ciliated groove lining the pharyngeal floor of tunicates. This paper describes the histological structure of this organ in two new species of doliolid-like animals, Doliopsis bahamensis and Paradoliopsis harbisoni, and compares it with that of Doliolum nationalis. The results confirm the distinction between the Doliolida and the other Thaliacea.

Electrochemiluminescence from Tunicate, Tunichrome–Metal Complexes and Other Biological Samples

Low level intrinsic electrochemiluminescence (ECL) was induced from body fluids and homogenized tissues of oysters and several species of tunicates. No significant ECL was detected in human blood cell lysates, or bovine haematin, but minor ECL was observed in avian blood cell lysates. Both terrestrial grass and seagrass exhibited ECL, which is probably attributable to chlorophyll, since dead (brown) grass did not demonstrate ECL. It was postulated that organic–metal complexes in marine invertebrates were, at least in part, responsible for the intrinsic ECL, since such animals are known to be rich in organically bound metals. However, alternative biochemical mechanisms for the observed ECL, which do not involve metal chelates, are possible. Various metal ions were added to the invertebrate preparations to determine whether exogenous metals could enhance or inhibit the ECL reactions. Strongly oxidizing metal ions such as Ag+, Au+, Cu2+, Hg2+ and Sb2+ at ≥100 ppm severely inhibited the intrinsic ECL response. No statistically significant ECL enhancement due to addition of metal ions was noted. ECL ‘profiles’ were generated which demonstrated differences in the ECL responses of individual tunicate preparations to the presence of various exogenous metal ions. Differences in ECL profiles may represent differences in types or levels of endogenous metal chelates or other biochemical constituents. In addition, synthetic tunichromes (tunicate pigments) were analysed for ECL in the presence and absence of various added metal ions. One synthetic tunichrome isomer demonstrated a specific ECL interaction with Hg2+, while the other demonstrated broader ECL activity with several metal ions.

Electrochemiluminescence from tunicate, tunichrome-metal complexes and other biological samples.

Low level intrinsic electrochemiluminescence (ECL) was induced from body fluids and homogenized tissues of oysters and several species of tunicates. No significant ECL was detected in human blood cell lysates, or bovine haematin, but minor ECL was observed in avian blood cell lysates. Both terrestrial grass and seagrass exhibited ECL, which is probably attributable to chlorophyll, since dead (brown) grass did not demonstrate ECL. It was postulated that organic-metal complexes in marine invertebrates were, at least in part, responsible for the intrinsic ECL, since such animals are known to be rich in organically bound metals. However, alternative biochemical mechanisms for the observed ECL, which do not involve metal chelates, are possible. Various metal ions were added to the invertebrate preparations to determine whether exogenous metals could enhance or inhibit the ECL reactions. Strongly oxidizing metal ions such as Ag+, Au+, Cu2+, Hg2+ and Sb2+ at > or = 100 ppm severely inhibited the intrinsic ECL response. No statistically significant ECL enhancement due to addition of metal ions was noted. ECL "profiles' were generated which demonstrated differences in the ECL responses of individual tunicate preparations to the presence of various exogenous metal ions. Differences in ECL profiles may represent differences in types or levels of endogenous metal chelates or other biochemical constituents. In addition, synthetic tunichromes (tunicate pigments) were analysed for ECL in the presence and absence of various added metal ions. One synthetic tunichrome isomer demonstrated a specific ECL interaction with Hg2+, while the other demonstrated broader ECL activity with several metal ions.

The genus Polycarpa (Ascidiacea, Styelidae) on the Atlantic and Mediterranean coasts of the Iberian Peninsula

The present work is a review of the 13 species of tunicates belonging to the genus Polycarpa, Heller, 1877 which are present in the Iberian Peninsula. Taxonomic, ecological, and distributional references are given for each species and descriptions of Polycarpa kornogi, P. violacea, P. pomaria, P. mamillaris, P. scuba, P. gracilis, and P. tenera are provided. The main diagnostic character between species of the fibrosa group lies in the shape of the polycarps. The distinction between P. pomaria and P. mamillaris is based on the number of sinuses on and between the branchial folds and the shape of the gonads. The morphology of the digestive tract and polycarps allows an easy distinction between P. tenera and P. graciiis. A tabular key for the identification of the iberian species is presented.