ANATOMY OF PSEUDOTRITONIA THIELE, 1912 AND NOTAEOLIDIA ELIOT, 1905 (GASTROPODA: OPISTHOBRANCHIA: NUDIBRANCHIA) FROM SIGNY ISLAND, ANTARCTICA

Several species of nudibranch molluscs are abundant amongstthe rich benthic hard substratum communities found close tothe British Antarctic Survey base at Signy Island, in the Atlanticsector of the Antarctic. Over the austral summer 1992/1993,two of the authors (LWB and DKAB) were able to collect someof the lesser known species of Nudibranchia at depths between3 and 40 metres, using SCUBA. New information on morphologyand anatomy of two of these species, Pseudotritonia gracilidensOdhner, 1944 (Charcotiidae, Arminoidea) and Notaeolidia gigasEliot, 1905(Notaeolidiidae, Aeolidoidea) are presented in thispaper. The validity of the species Notaeolidia gigas is strengthened. (Received 9 February 1994; accepted 18 September 1994)     

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;     

NEW SPECIES OF SMEAGOL FROM AUSTRALIA AND NEW ZEALAND, WITH A DISCUSSION OF THEAFFINITIES OF THE GENUS (GASTROPODA: PULMONATA)

Five species of the marine pulmonate genus Smeagol (family Smeagolidae)are described from upper littoral shingle habitats from southeastern Australia and New Zealand. The systematic position ofthe family is discussed. (Received 24 June 1991; accepted 2 October 1991)     

PROTECTIVE-COMMENSAL MUTUALISM BETWEEN THE QUEEN SCALLOP CHLAMYS OPERCULARIS(LINNAEUS) AND THE ENCRUSTING SPONGE SUBERITES

The relationship between the two encrusting sponges, Suberitesrubrus (Sole-cava & Thorpe, 1986) and Sub-erites luridus(Sole-cava & Thorpe, 1986) and the pectinid bivalve molluscChlamys opercularis (Linnaeus) was shown to be a protective-commensalmutualism. The sponge protected the scallop from asteroid predation(Asterias rubens, L.) probably by reducing their tube-feet adhesionand also by excluding the settlement of other taxa likely tohinder the scallop's mobility. The sponge benefited in turnby protection from predation by the nudibranch Archidoris pseudoargus(Pallas) and more generally from transport to favourable locations. Both Asterias and Archidoris were frequently observed movingdirectly towards their prey, possibly indicating chemotaxicmechanisms. Yet, the sponges did not appear to confer any chemicalprotection to the scallop from asteroid attack. Similarly theliving scallop conferred no chemical protection to the sponge. (Received 12 December 1990; accepted 24 September 1991)     

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)     

REVIEW OF THE GENUS DENDRODORIS EHRENBERG, 1831 (GASTROPODA: NUDIBRANCHIA) IN THE ATLANTIC OCEAN

Six valid species of the nudibranch genus Dendrodons Ehrenberg,1831 inhabit the Atlantic Ocean, including the Mediterraneanand Caribbean Seas. Dendrodons lumbata (Cuvier, 1804), Dendrodonsgrandiflora (Rapp, 1827), Dendrodons nigra (Stimpson, 1855)(immigrant from the Red Sea), Dendrodons krebsu (Mörch,1863), Dendrodoru senegalensis Bouchet, 1975 and Dendrodonswarta Marcus & Gallagher, 1976. Additional data about thebiology and geographical distribution of these species are presented.New evidence suggests that other species assigned to the genusDendrodons, Dendrodons racemosa Pruvot-Fol, 1951 and Dendrodonsminima Pruvot-Fol, 1951, must be included in the genus DoriopsillaBergh, 1880. Three new species of Dendrodoris are describedfrom the Northeastern Atlantic and West Africa;Dendrodons angolensis,Dendrodoris guineana and Dendrodons herytra. The variable external morphology makes species recognition difficult.Instead, the diagnostic characters utilised to separate speciesare the shape of the male cirrus hooks, the structure of thereproductive system and features of the egg-mass. (Received 25 April 1995; accepted 1 August 1995)     

FURTHER STUDIES ON THE TAXONOMY AND BIOLOGY OF THE OCTOCORAL-FEEDING GENUS PHYLLODESMIUM EHRENBERG, 1831 (NUDIBRANCHIA: AEOLIDOIDEA)

The aeolid nudibranch genus Phyllodesmium (Mollusca: Gastropoda)is reviewed, three new species are described and further informationon the biology, anatomy and distribution on the eight previouslyknown species is reported. The genus Ennoia Bergh, 1896 is considereda synonym of Phyllodesmium and the type species Ennoia briareusredescribed. The genus Phyllodesmium is unique amongst the aeolidsin feeding on octocoral cnidarians. This has led to the evolutionof nudibranch- zooxanthellae symbioses, zooanthellae being obtainedfrom the octocoral prey. The adaptations developed throughoutthe genus are described and possible relationships between thespecies proposed. (Received 6 January 1990; accepted 20 May 1990)     

EOLID NUDIBRANCHIATE MOLLUSCA FROM BARBADOS

17 species of eolid nudibranch are described from Barbados inthe Caribbean sea of which three are new: Cuthona iris, Cuthonabarbadiana and Learchis evelinae. The present status of thefamilies Cuthonidae and Facelinidae is discussed. (Received 8 July 1982;     

OBSERVATIONS ON THE GROWTH, REPRODUCTION AND FEEDING OF THE NUDIBRANCH ARMINA TIGRINA

One specimen of the sand-burrowing nudibranch Armina tigrinaRafinesque was collected from South Carolina in June. The specimendeposited a single egg mass of approximately 6500 white eggswhich developed into lecithotrophic veligers in 8 days at 23°C.Of the veligers which metamorphosed, 9 lived 4–5.5 months(i.e. the life cycle was subannual). Eight individuals reachedsexual maturity in about 80 days. Copulation began at a bodylength of 24 mm and oviposition at 28 mm. During the 1.5 monthegg-laying period, each individual laid 2–4 wavy egg masseswith 2000–7000 eggs per mass. Death followed oviposition.Average growth rate of fed and starved pre-ovipositional nudibranchswas 3.4% and 0.9% per day respectively. Growth rate of ovipositingspecimens was 0.6% or less per day. Based on average feedingrates, each nudibranch consumed approximately 1.6 g damp weightof Renilla reniformis (one small colony) between metamorphosisand egg laying and 6.1 g damp weight (about two average colonies)from egg laying to death. Feeding efficiency is presumably increasedby interlocking and abutting radular teeth. Egg diameters reportedfor Armina tigrina from South Carolina and Florida were 199µm and 82 µm respectively. This difference suggeststhe existence of two species of Armina or ne species with twogeographically separated developmental types. Current address: Marine Science Institute, Northeastern University,Nahant, Massachusetts 01908. U.S.A. (Received 10 April 1980;     

PARTHENOGENESIS, SEX AND CHROMOSOMES IN POTAMOPYRGUS

Widely different sex ratios in certain New Zealand populationsof the hydrobiid gastropod Potamopyrgus antipodarum (Gray) weregenerally found to vary little though in one stream a high-male/low-maleboundary moved steadily upstream over 20 years. Laboratory breeding and chromosome studies indicated that NewZealand high-male populations are diploid with 2n = 34 and reproducesexually, while New Zealand low-male populations and all thosefrom Europe and Australia have 2n = 52 or 46 and reproductionis largely parthenogenetic. (Received 15 July 1991; accepted 30 August 1991)     

DESCRIPTION OF A NEW SPECIES OF PHYLLIDIOPSIS BERGH (NUDIBRANCHIA: DORIDOIDEA: PHYLLIDIIDAE) FROM THE TROPICAL WESTERN PACIFIC, WITH COMMENTS ON THE ATLANTIC SPECIES

A new species of phyllidiid nudibranch, Phyllidiopsis shireenae,is described. The new species has a middorsal crest insteadof being flattened dorso-ventrally like most phyllidiids. Itsbody is a very pale shade of pink with black bands, and itsrhinophores are salmon pink. The anatomy of the alimentary systemand reproductive system are described. Characters originallyused by Bergh (1875) to differentiate the genus are supportedby this new species. Phyllidiopsis shi-reenae is presently knownfrom coral reef habitats in the extreme western Pacific Ocean.A review of the taxonomic status of the Atlantic specis of Phyllidiopsisis required. ^*Present address: Australian Biological and Environmental Survey.Australian National Parks and Wildlife Service, GPO Box 1383,Canberra. ACT 2601. Australia. (Received 15 August 1989; accepted 8 January 1990)     

FEEDING AND GROWTH OF THE AEOLID NUDIBRANCH CUTHONA NANA (ALDER AND HANCOCK, 1842)

Feeding and growth of the aeolid nudibranch Cuthona nana wasdocumented. Cuthona nana feeds specifically on the colonialhydroid Hydractinia echinata. Nudi-branchs were observed onhermit crab shells in Gos-port Harbor at the Isles of Shoals,Maine and on old bridge pilings near Gerrish Island, Maine. Grazing rates of nudibranchs (3–25 mm) were quantifiedover 24 hour periods in the laboratory. Larger nudibranchs consumedmore hydroid tissue feeding mostly on polyps, whereas smallerindividuals consumed less and fed on mat tissue. Grazing intensityin the field at Gosport Harbor was determined by estimatingthe area of grazed patches of hydroid colonies attached to hermitcrab shells. The average patch size was 5.75% of the total colonyarea. Growth rates for nudibranchs were determined in the laboratory.Growth rates were greatest prior to maturation and oviposition.Animals from Gerrish Island and Gosport Harbor decreased insize after oviposition due to senescence. Nudibranchs from GerrishIsland reached a maximum size of 12 mm, compared to 23 mm foranimals at Gosport Harbor. ^*Present address: Division of Science and Mathematics. Universityof Minnesota, Morris. Minnesota 56267, USA     

DESCRIPTION OF A NEW GENUS AND SPECIES BELONGING TO THE FAMILY PHYLLIDIIDAE (NUDIBRANCHIA: DORIDOIDEA)

A new genus of phyllidiid nudibranch, Reticulidia, is described.Distinguishing features are the reticulate pattern of smoothridges on the dorsum and the radially arranged, glandular discswhich make up the pharyngeal bulb. Additional features of theforegut are described and compared with other genera. The importanceof the alimentary system for the separation of genera withinthe Phyllidiidae is supported and its validity reinforced bythis new genus. One species, Reticulidia halgerda, is describedas new and differentiated from a second, sympatric species.Reticulidia is presently known from the eastern Indian Ocean,South China Sea and western Pacific Ocean. ^*Present address: Australian Biological and Environmental Survey,Australian National Parks and Wildlife Service. GPO Box 1383,Canberra. ACT 2601. Australia. (Received 15 August 1989; accepted 8 January 1990)     

TAXONOMY AND OCCURRENCE OF DENDRODORIS NIGRA AND DENDRODORIS FUMATA (NUDIBRANCHIA: DENDRODORIDIDAE) IN THE INDO-WEST PACIFIC REGION

The nudibranch Dendrodoris nigra (Stimpson, 1855) has hithertobeen considered as a single, highly poly-chromic species. Ourinvestigations of external morphology, anatomy and colour variationhave revealed more than one species exists. This conclusiongives credibility to the previous discovery of differing developmentalpatterns within D. nigra. Besides D. nigra, we recognise Dendrodorisfumata (Rüppell & Leuckart, 1830) which has three distinguishablecolour forms. The occurrence of D. nigra is confirmed to beextensive, however, the species was not found to be circum-Australianas previously reported. The presence of D. fumata in Australiais confirmed and the species is also reported from Hong Kongand Fiji for the first time. The clear separation of these twospecies and recognition of the different colour forms will permita more accurate picture of their distribution. (Received 15 November 1994; accepted 2 January 1997)     

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)     

MORPHOLOGICAL AND CHEMICAL CAMOUFLAGE OF THE MEDITERRANEAN NUDIBRANCH DISCODORIS INDECORA ON THE SPONGES IRCINIA VARIABILIS AND IRCINIA FASCICULATA

The nudibranch Discodoris indecora shows a perfect camouflageon its prey, the dictyoceratid sponge Ircinia variabilis. Shapeand colour of the nudibranch are remarkably similar to thatof the sponge which is widespread in the shallow waters of theMediterranean Sea. The metabolite pattern of I. variabilis isdominated by unusual molecules, the sesterter-penoids palinurinand variabilin, containing 25 carbons and displaying at theends a ß-substituted furan ring and a tetronic acid.However, a chemical polymorphism has been recently describedfor I. variabilis. Some specimens contain either palinurin orvariabilin whereas others possess a mixture of both sestertepenoids.During the study of Mediterranean sponges, a linear sesterterpenoidrelated to palinurin and variabilin was found in Ircinia fasciculata,that from a taxonomic point of view is closely relatedto Irciniavariabilis. Discodoris indecora shows a typical defence behaviourwhen it is disturbed, secreting a copious white slime that containslarge amounts of palinurin and variabilin. Most likely the animalis able to transfer the sponge metabolites from the digestiveglands to mantle glands. Electron micrographs of the nudibranchmantle showed the presence of unicellular glands characterizedby a cylindrical vacuole with a big nucleus on the basis. Theglands were concentrated in the most conspicuous tubercles ofthe dorsal mantle. Probably, the sponge metabolites are storedin these glands. Comparative chemical analysis of mucous secretions, dorsal tubercles,mantle, foot, digestive glands and hepatopancreas of D. indecoraconfirmed this hypothesis. Palinurin and fasciculation were,of course, present in the digestive glands but they were alsofound in the mucus and in the mantle sections enriched by theabove described unicellular glands. The defensive role of palinurinand variabilin, strongly suggested by their anatomical location,was supported by recording the induction of feeding-deterrencein the fresh-water fish Carassius auratus and in the marinefish Chromis chromis and Sparus auratus. (Received 15 March 1996; accepted 27 January 1997)