Stylochus (Imogene) matatasi n. sp. (Platyhelminthes,Polycladida): pest of cultured giant clams and pearl oysters from Solomon Islands

A large polyclad flatworm has been consistently found associated with mortalities of the cultured giant clam,Tridacna gigas (L.) and the fouling pearl oysterPinctada maculata (Gould) in Solomon Islands.Stylochus (Imogene) matatasi n. sp. is described and a brief account of its biology is given.ICLARM Contribution # 856.ICLARM Contribution # 856.     

REDESCRIPTION OF EMBLETONIA GRACILE RISBEC, 1928 (NUDIBRANCHIA: EMBLETONIIDAE): RELOCATION TO SUBORDER DENDRONOTACEA WITH TAXONOMIC AND PHYLOGENETIC IMPLICATIONS

The nudibranch mollusc Embletonia gracile Risbec, 1928 is redescribedon the basis of ten specimens from the southern Pacific Ocean(New Zealand, Fiji, Australia, Papua New Guinea). We concludethat Embletoniella paucipapillata (Baba & Hamatani, 1963)is a junior synonym. Even the most detailed previous studieswere compromised by the availability only of juvenile animals< 8 mm long; adults are now known to attain 23 mm crawlinglength. Our material permitted a reassessment both of ontogeneticand intraspecific variation within this enigmatic nudibranch.Reasons that substantiate the referral of the Embletoniidaeto the suborder Dendronotacea are presented. (Received 20 February 1991; accepted 10 May 1991)     

Predation on kamptozoans (Entoprocta)

Abstract. Predation on kamptozoans (phylum Kamptozoa = Entoprocta) is not mentioned in any literature on the phylum. We have found a plagiostomid turbellarian flatworm ( Plagios-tomum sp.) preying upon Barentsia benedeni in an estuarine sublittoral fouling community in Long Island Sound, USA. Previous records of predation on kamptozoans by nudibranch opis-thobranchs (sea slugs) are reviewed. Predation on kamptozoans by some members of two phyla, Mollusca and Platyhelminthes, is thus now known.     

Dorid nudibranchs from eastern Australia (Gastropoda, Opisthobranchia)

Collections of nudibranch gastropods made in 1968 are described. All the 18 eastern Australian species of doridaceans (excluding chromodoridiform species) obtained are illustra-ed and investigated anatomically, often for the first time since their original discovery over a century ago. A list of the dorid nudibranches reliably recorded from Australian waters (compiled by R. Burn) supplements the paper.     

Defensive responses of gastropods to the predatory flatworms Freemania litoricola (Heath and McGregor) and notoplana acticola (Boone)

Three species of gastropods were tested in the laboraory and in the field for responses to contact with the polyclad flatworms Freemania litoricola (Heath and McGregor) and Notoplana acticola (Boone). The three limpets differed considerably in their responses to Freemania litoricola All specimens of Notoacmea scutum (Rathke) responded in some way to this flatworm, mostly by running. Fewer than half of the Collisella digitalis (Rathke) responded to Freemania litoricola, and these responded by mushrooming - elevating the shell several millimeters off the substratum. Collisella scabra (Gould) did not respond any differently to contact with Freemania litoricola than to contact with a control probe. Differences in the responses of these limpets to Freemania litoricola are discussed in relation to the characteristic intertidal distributions of this flatworm and the limpets. In contrast to Freemania litoricola, the polyclad Notoplana acticola typically did not elicit defensive responses. This difference is related to the diets of the two flatworms. Freemania litoricola was found to be a predator on limpets, whereas no evidence was found that Notoplana acticola eats limpets.     

Observations on the ecology of Membranipora (bryozoa) and a major predator Doridella steinbergae (nudibranchiata) along the fronds of Laminaria saccharina at Friday Harbor,washington

The distribution of the bryozoan Membranipora and one of its major predators, the nudibranch Doridella steinbergae (Lance) along the fronds of Laminaria saccharina (L.) Lamour. at Friday Harbor, Washington were studied during the summer (July–August) 1975. Whilst the fronds are most heavily encrusted by the bryozoan in the middle and distal regions, settlement occurs principally in the younger more basal regions of the plants. The distribution pattern of the nudibranch closely parallels that of its prey though there is a tendency for the most distal regions, especially in older plants, to be avoided. An average density of 240 Doridella/plant was found for plants of mean length 91.0 cm. Despite the severe predation pressure imposed by this nudibranch, evidence tends to suggest that these extensive and highly productive Membranipora populations could probably support even higher densities of Doridella than those presently found — at least over that period of the year during which this investigation was made.     

NORTH ATLANTIC NUDIBRANCHS OF THE CHROMODORTS CLENCHI COLOUR GROUP (OPISTHOBRANCHIA: CHROMODORIDIDAE)

The correct identity of three chromodorid nudibranch species,Chromodoris clenchi, C. neona and C. binza is established onthe basis of material from the Caribbean Sea. These three speciesare compared with C. britoi, from the northeastern Atlanticand the Mediterranean Sea. All four species have a colour patternof cream with red (or yellow) lines and blue spots. (Received 30 March 1993; accepted 20 November 1993)     

First records of Cotylea (Polycladida,Platyhelminthes) for the Atlantic coast of the Iberian Peninsula

A study of polyclad fauna of the Atlantic coast of the Iberian Peninsula was carried out from 2010 to 2013. The paper reports nine new records belonging to three Cotylean families: the family Euryleptidae Lang, 1884, Pseudocerotidae Lang, 1884 and the family Prosthiostomidae Lang, 1884, and describes one new species, Euryleptodes galikias sp. n.     

A NEW SPECIES OF THE AEOLID GENUS FLABELLINA (NUDIBRANCHIA) FROM THE STRAIT OF GIBRALTAR

A new species of nudibranch, Flabellina insolita, is describedfrom specimens from the Strait of Gibraltar. The new speciesis assigned to the genus Flabellina on the basis of the jaws,radula and reproductive system, despite the shape of the rhinophoresand oral tentacles and the presence of small papillae flankingthe pericardium and small laminar enlargements on the dorsalsurface of the body. These features separate this species fromother aeolids. (Received 14 June 1988; accepted 19 August 1988)     

THE GENUS TRAPANIA (NUDIBRANCHIA: GONIODORIDIDAE) IN THE INDO-WEST PACIFIC

Seven new species of the nudibranch genus Trapania Pruvot-Fol,1931 (Goniodorididae) are described from the Indo-West Pacificand an eighth species, T. japonica (Baba, 1935), originallydescribed from one preserved specimen from Japan, is redescribedfrom specimens collected in Hong Kong and tropical eastern Australia.Three of the new species are from temperate south-eastern Australiaand one from tropical eastern Australia. Two species are knownonly from Hong Kong and a third is recorded from the SudaneseRed Sea as well as Hong Kong. Only ten other species of Trapania have been described, sixof those from Europe, and one each from Brazil, California,Japan and New Zealand. The anatomy and external colour patternof these species is compared with that of the seven new species. (Received 12 December 1986;     

Initial results on the molecular phylogeny of the Nudibranchia (Gastropoda, Opisthobranchia) based on 18S rDNA data

This study investigated nudibranch phylogeny on the basis of 18S rDNA sequence data. 18S rDNA sequence data of 19 taxa representing the major living orders and families of the Nudibranchia were analyzed. Representatives of the Cephalaspidea, Anaspidea, Gymnomorpha, Prosobranchia, and Pulmonata were also sequenced and used as outgroups. An additional 28 gastropod sequences taken from GenBank were also included in our analyses. Phylogenetic analyses of these more than 50 gastropod taxa provide strong evidence for support of the monophyly of the Nudibranchia. The monophyly of the Doridoidea, Cladobranchia, and Aeolidoidea within the Nudibranchia are also strongly supported. Phylogenetic utility and information content of the 18S rDNA sequences for Nudibranchia, and Opisthobranchia in general, are examined using the program SplitsTree as well as phylogenetic reconstructions using distance and parsimony approaches. 0Results based on these molecular data are compared with hypotheses about nudibranch phylogeny inferred from morphological data.     

Phylogenetic analysis of Euthyneura (Gastropoda) by means of the 16S rRNA gene: use of a 'fast' gene for 'higher-level' phylogenies

The phylogeny of Euthyneura is analysed by using DNA sequences of the mitochondrial 16S rRNA gene. Despite the common notion that this gene is too variable to provide useful information at high taxonomic levels, such as in the present study, bootstrap proportions are high for several clades in the study. This indicates that there is a useful amount of variation despite the noise due to multiple substitutions. The analyses furthermore indicate that (i) Gymnosomata (represented by Clione) is not a part of Euthyneura, but Clione forms a clade with the caenogastropods; (ii) Acteon is the sister group to the remaining euthyneuran taxa in the study; (iii) the nudibranch taxa form two clades, one comprising Dendronotoidea, Arminoidea and Aeolidoidea (together Cladobranchia) with Notaspidea (represented by Berthella) as sister group, while the fourth nudibranch taxon, Doridoidea, forms a separate clade; (iv) Cephalaspidea s.s. and Anaspidea form clades that are each other''s sister groups (together Pleurocoela). Finally, there is no clade present in the analyses corresponding to the taxon Opisthobranchia in the traditional sense, and the use of this name is probably better abandoned altogether.     

Phyllidiidae (Nudibranchia,Heterobranchia, Gastropoda): an integrative taxonomic approach including chemical analyses

Organisms Diversity & Evolution - Members of the widely distributed and common nudibranch family Phyllidiidae are often easily spotted in the marine environment because of their conspicuous...     

Evolution of flatworm central nervous systems: Insights from polyclads

The nervous systems of flatworms have diversified extensively as a consequence of the broad range of adaptations in the group. Here we examined the central nervous system (CNS) of 12 species of polyclad flatworms belonging to 11 different families by morphological and histological studies. These comparisons revealed that the overall organization and architecture of polyclad central nervous systems can be classified into three categories (I, II, and III) based on the presence of globuli cell masses -ganglion cells of granular appearance-, the cross-sectional shape of the main nerve cords, and the tissue type surrounding the nerve cords. In addition, four different cell types were identified in polyclad brains based on location and size. We also characterize the serotonergic and FMRFamidergic nervous systems in the cotylean Boninia divae by immunocytochemistry. Although both neurotransmitters were broadly expressed, expression of serotonin was particularly strong in the sucker, whereas FMRFamide was particularly strong in the pharynx. Finally, we test some of the major hypothesized trends during the evolution of the CNS in the phylum by a character state reconstruction based on current understanding of the nervous system across different species of Platyhelminthes and on up-to-date molecular phylogenies.     

Development,metamorphosis, and natural history of the nudibranch Doridella obscura Verrill (Corambidae: Opisthobranchia)

The doridacean nudibranch Doridella obscura Verrill was raised through one complete generation in laboratory culture, and spawning behavior monitored for a year at monthly intervals in Barnegat Bay, New Jersey.The nudibranch deposited egg masses throughout the year in Barnegat Bay, and the larvae remained viable at temperatures ranging from 1.5 to 28 °C. At 25 °C the eggs hatch 4 days after oviposition, and the planktotrophic veliger larvae swim and feed for 9 days before they metamorphose. Settlement occurs specifically on the bryozoan Electro crustulenta (Pallas). The spirally coiled larval shell grows rapidly until the dorsal mantle fold is retracted from the aperture 5–6 days after hatching. Although starved larvae grow only slightly and do not metamorphose, they resume normal development on introduction of suitable food. Newly metamorphosed juveniles consume algae and debris on the surface of the bryozoan until they grow large enough to attack the living zooids of E. crustulenta.The life cycle of Doridella obscura is short (26 days at 25 °C), allowing the nudibranchs to take advantage of short-lived Electra crustulenta colonies in unstable habitats in bays and estuaries.     

Chemosensory and feeding responses of the nudibranch Aeolidia papillosa to the symbiotic sea anemone Anthopleura elegantissima

Abstract. The aeolid nudibranch Aeolidia papillosa is an important predator on the sea anemone Anthopleura elegantissima , a host to two kinds of endosymbiotic algae: zooxanthellae and zoochlorellae. The possible influence of the algae on the nudibranch's predatory response to this anemone was examined in a laboratory study. In chemosensory experiments, the nudibranch detected and chose anemone scent over a seawater control, but in both chemosensory and feeding experiments showed no preference for zooxanthellate or zoochlorellate anemones. Ingestive conditioning on zooxanthellate or zoochlorellate anemones had no effect on choice of these two anemone types in chemosensory experiments. Comparisons of the productivity and photosynthetic pigments of algae obtained from nudibranch feces and from anemones show that both algae survive passage through the nudibranch gut. The productivity of fecal zooxanthellae was 1.6X greater than that of zooxanthellae freshly isolated from anemones, although the chlorophyll a content of fecal zooxanthellae was reduced. The productivity and amount of pigments were the same for zoochlorellae in nudibranch feces and freshly isolated from anemones. Comparing fecal and isolated algae, there was no significant difference in the percentage of zooxanthellae in the process of cell division. However, the percentage of dividing cells was 2.6X higher in fecal than in freshly isolated zoochlorellae (18% and 6.9% respectively). Although the endosymbiotic algae do not make their host more or less attractive to the nudibranch, this predator may play an important role in maintaining the symbiotic relationship of Anthopleura elegantissima with zooxanthellae and zoochlorellae by providing viable algae in its feces as a source for the anemone host.     

Polycladida phylogeny and evolution: integrating evidence from 28S rDNA and morphology

Polyclad flatworms have a troubled classification history, with two contradicting systems in use. They both rely on a ventral adhesive structure to define the suborders Acotylea and Cotylea, but superfamilies were defined according to eyespot arrangement (Prudhoe’s system) or prostatic vesicle characters (Faubel’s system). Molecular data available cover a very limited part of the known polyclad family diversity and have not allowed testing morphology-based classification systems on Polycladida yet. We thus sampled a suitable marker, partial 28S ribosomal DNA (rDNA), from Polycladida (19 families and 32 genera), generating 136 new sequences and the first comprehensive genetic dataset on polyclads. Our maximum likelihood (ML) analyses recovered Polycladida, but the traditional suborders were not monophyletic, as the supposedly acotyleans Cestoplana and Theama were nested within Cotylea; we suggest that these genera should be included in Cotylea. The partial 28S rDNA trees were generally well supported and robust but in conflict with both Faubel’s and Prudhoe’s superfamilies. Therefore, we compiled morphological and anatomical characters for all taxa used and examined their distribution on our molecular tree. Combining morphological and molecular evidence, we redefined polyclad superfamilies. Acotylea contain tentaculated and atentaculated groups and is now divided in three superfamilies. The suborder Cotylea can be divided in five superfamilies. In general, there is a trait of anteriorization of sensory structures, from the plesiomorphic acotylean body plan to the cotylean gross morphology. Traditionally used characters, such as prostatic vesicle, eyespot distribution, and type of pharynx, are all homoplastic and likely have misled polyclad systematics so far.     

Discharge of nematocysts isolated from aeolid nudibranchs

Nematocysts were extracted from 3 nudibranch species and one sea anemone species, and the ability of several test fluids to promote discharge was examined. Except when isolated in sodium citrate, nudibranch nematocysts did not discharge in response to any test fluids. Nudibranch nematocysts isolated in sodium citrate discharged when tested with EGTA, distilled water, and calcium-free artificial seawater, but there were differences among the 3 nudibranch species. Nematocysts isolated from one nudibranch species and nematocysts isolated from that nudibranch's sea anemone prey differed in the percentage that discharged in response to EGTA and distilled water. These results suggest that nematocysts stored by nudibranchs are altered in some way, resulting in the different discharge responses.     

Discriminatory predation by three invertebrates on eastern oysters (Crassostrea virginica) compared with non-native Suminoe oysters (C. ariakensis)

Abstract. Diminished populations of eastern oysters Crassostrea virginica in Chesapeake Bay have stimulated proposals to introduce Crassostrea ariakensis from Asia to restore oyster stocks. As part of a program evaluating possible ramifications of such an introduction, we studied how invertebrate predators responded to this non-native oyster. We compared predation activity under laboratory conditions by oyster drills ( Urosalpinx cinerea; Eupleura caudata ) that bore through an oyster's shell and by the seastar Asterias forbesi that pulls shell valves apart. These three predators preyed significantly (p<0.05) more on the familiar C. virginica than on the novel C. ariakensis . We previously reported that five crab species preyed significantly more on C. ariakensis than on C. virginica , with predation by polyclad flatworms similar between oyster species. Thus, the drills and the seastar differed from the crabs and the flatworms in their response to novel prey. When Urosalpinx cinerea was placed in a Y-maze after being held for 40 d with oysters of one species or the other, the drills moved toward C. virginica effluent more than toward C. ariakensis effluent. This response did not depend on the species of oyster the drills had been held with, suggesting that the drills were responding to more familiar infochemicals from eastern oysters than from the non-native oysters.     

Endobacterial morphotypes in nudibranch cerata tips: a SEM analysis

The SEM investigation of nudibranch cerata material exhibits endobacterial morphotypes found in 12 out of 13 species tested: Aeolidia papillosa, Berghia caerulescens, Coryphella brownii, Coryphella lineata, Coryphella verrucosa, Cuthona amoena, Facelina coronata, Flabellina pedata, Dendronotus frondosus, Doto coronata, Tritonia plebeia and Janolus cristatus. Endobacteria could not be detected inside Tritonia hombergi. Endobacterial morphology found inside nudibranch species was compared to bacterial morphotypes detected earlier in tentacles of cnidarian species. SEM micrographs show endobacterial analogy among nudibranch species, but also similarity to cnidarian endobacteria investigated earlier. Of course, morphological data of microbes do not allow their identification. However, since most of these nudibranch species prey on cnidaria, it cannot be excluded that many of the endobacteria detected inside nudibranch species may originate from their cnidarian prey. Our previous data describing genetic affiliation of endobacteria from nudibranchian and cnidarian species support this assumption. Dominant coccoid endobacteria mostly exhibit smooth surface and are tightly packed as aggregates and/or wrapped in envelopes. Such bacterial aggregate type has been described previously in tentacles of the cnidarian species Sagartia elegans. Similar coccoid bacteria, lacking envelopes were also found in other nudibranch species. A different type of coccoid bacteria, characterized by a rough surface, was detected inside cerata of the nudibranch species Berghia caerulescens, and surprisingly, inside tentacles of the cnidarian species Tubularia indivisa. In contrast to cnidarian endobacteria, rod-shaped microorganisms are largely absent in nudibranch cerata.