Assessment of space utilisation in a subtidal temperate bryozoan community

On subtidal hard substrata, Bryozoa are often very abundant, both in terms of numbers of colonies and numbers of species. To investigate how so many species are able to co-exist, often in close proximity to each other, subtidal material was dredged from an area of bryozoan-rich coarse shelly sea-bed off the south-west of the Isle of Man (British Isles) in autumn 1984 and 1985. A survey was performed on the distribution of colonies of eight common, encrusting cheilostome bryozoan species across the surfaces of four types of empty, disarticulated bivalve shells. Each species was found to be significantly commoner on certain substratum types such as rough surfaces or inner concave surfaces. Fenestrulina malusii (Audouin) showed a further, more specific, tendency to be signficantly more abundant on the grooves of the corrugated inner surfaces of left valves of Pecten maximus (L.). In general however there was much overlap in distribution and it is proposed that such large numbers of species are able to co-exist because of the evolution of different life-history strategies ensuring that each species uses the available temporally and spatially heterogenous substrata in subtly different ways; some species, for example, occupying substrata that are optimal to bryozoan growth and other species, by reaching maturity earlier, being able to inhabit more ephemeral suboptimal substrata.     

Planktotrophic larval development is associated with a restricted geographic range in Lasaea,a genus of brooding,hermaphroditic bivalves

Members of the intertidal, near-cosmopolitan mollusc genus Lasaea brood their young either to a planktotrophic veliger or crawl-away juvenile stage of development. Developmental mode can be reliably inferred from brood masses and from prodissoconch structure. I have conducted a global developmental survey of this genus based mainly on examination of hundreds of museum lots. With one exception, Lasaea species with a planktotrophic larval development were restricted to the western Pacific. Congeners that lack planktotrophic larvae were found on all continents apart from Antarctica, and also on a large number of oceanic islands. These results indicate that (1) Lasaea species releasing crawl-away juveniles have a markedly greater collective geographic range than congeners with planktotrophic larvae; (2) pelagic larvae are not necessary for long-distance dispersal in this genus; (3) rafting has played a key role in the evolutionary success of the genus Lasaea; (4) cross-fertilizing Lasaea species with feeding larvae are less successful in utilizing chance rafting events to colonize new areas than are congeners lacking these traits.     

Reproduction,recruitment and fragmentation in nine sympatric species of the coral genus Acropora

Multispecies assemblages of the coral genus Acropora occur commonly throughout the Indo-Pacific Ocean. Nine species from such an assemblage comprising 41 species of Acropora, at Big Broadhurst Reef on the Great Barrier Reef, were studied during 1981–1983. Similarities and differences in reproductive modes and timing, oocyte dimensions and fecundity, recruitment by larvae and by fragments, and mortality were recorded. All species had an annual gametogenic cycle, were simultaneous hermaphrodites, and had the same arrangement of gonads in polyps. In six species, most colonies released gametes on the same night of the year, in early summer, during a mass spawning event involving many coral genera. A seventh species had colonies spawning at this as well as other times of the year. Another species spawned in late summer, and gametes were not observed to mature in the last species. Eggs were very large (601 to 728 m geometric mean diameter) and fecundity of polyps low, compared with other corals; no reduction in oocyte numbers occurred during oogenesis. Reef-flat species had slightly bigger and fewer eggs than reef-slope species. All species recruited by larvae, but four also multiplied by fragmentation, either year-round or during occasional rough weather. Yearround fragmenters had few larval recruits; non-fragmenters had many, and a rough-weather fragmenter had an intermediate number of larval recruits. It was concluded that larval recruitment largely determined species composition, and that reduced larval recruitment was responsible for sparse distribution of fragmenting species. Subsequent mortality in some species and increase by fragmentation in others probably determined relative abundances.     

Developmental types of shallow-water asteroids of McMurdo Sound,Antarctica

The mode of development was ascertained for 14 of the 16 species of sea stars known to occur in shallow waters of McMurdo Sound, Antarctica (77°51S; 166°40E). The species were collected between September 1984 and December 1985. Females of three species,Odontaster validus, O. meridionalis andPorania antarctica, spawn small to moderate eggs (0.17 to 0.55 mm), have a high fecundity, and produce feeding larvae. Females of an undescribedPorania species spawn a few eggs (150 to 310) that are 0.55 mm in diameter and develop into demersal non-feeding larvae. Females ofDiplasterias brucei andNotasterias armata produce a few (<300) large eggs (2.8 to 3.5 mm) and brood their young. Females of the remaining eight species have moderate fecundity and produce pelagic non-feeding larvae, as determined from egg type (buoyant, 0.54 to 1.28 mm diam) and direct observations of spawning and development. The high incidence (11 out of 14 species; 79%) of non-feeding development is consistent with predictions that environmental conditions in high-latitude regions are unfavorable for planktotrophic development. Nonetheless, most of the species surveyed (11 out of 14) had pelagic larvae, which contradicts inferences of unusual selection for benthic development in the Antarctic.     

Population dynamics of Eudendrium glomeratum (Cnidaria: Anthomedusae) on the Portofino Promontory (Ligurian Sea)

Eudendrium glomeratum Picard, in the Ligurian Sea, is one of the major components of hard-bottom sessile zoobenthos in the cold season. It settles mainly between 10 and 40 m depth, forming a seasonal facies. The presence of E. glomeratum has been evaluated by measuring in situ the height of the colonies present within a standard surface of 1 m². Observations were carried out every other week for a whole year. The height of the colonies was correlated with their biomass (wet weight) and trophic functionality (number of polyps). The quantitative evaluation of the population shows that the situation is stable, with almost identical values at the extremes of the observed yearly time series. The species is present from October to April–May, and it is absent in the summer. The formation and disappearance of the E. glomeratum population are sudden. The colonies are sexually mature from their appearance in October to December–January. Different categories of colonies are recognizable; and are essentially referable to two groups: (1) colonies deriving from regeneration of colonies present in the previous year (45%); (2) colonies deriving from planula settlement (43%). A third group (12%) is of uncertain origin and may belong to either of the abovementioned categories. Mortality is 60% in the first group, and 82% in the second one. By dead colonies is meant those which do not reappear after a yearly cycle.     

Influences of habitat and natural disturbances on contributions of massive Porites corals to reef communities

We compared densities, distributions and size frequencies of massive corals in the genus Porites on five relatively exposed, mid-shelf reefs (50 km offshore) in the central Great Barrier Reef with those on a sheltered inshore reef (10 km offshore). Data included various transect and mapping studies between 1984 and 1990, estimates of size-dependent damage from the crown-of-thorns starfish Acanthaster planci, estimated densities of herbivorous sea urchins (potential predators of juveniles), and observations of size-specific effects of tropical cyclones. Assemblages of Porites spp. on mid-shelf reefs were dominated by small colonies (2 to 10 cm diam) established either from planula larvae or from small tissue remnants that had survived A. planci predation in the early to mid-1980s. Large colonies (up to 10 m diam) were scarce, except for localized aggregations on terraces at the base of reef slopes (6 to 12 m deep). Extensive space suitable for settlement by coral larvae can be attributed to recurrent cyclones and A. planci outbreaks. Despite low sea urchin predation, the slowly growing Porites juveniles are likely to die from overgrowth by numerous, much faster growing corals. On the sheltered inshore reef, the coral community was dominated by very large (>5 m diam) Porites colonies, several centuries old; recruitment was mainly by fragmentation of large colonies; there was little space available for settlement, and probabilities of juvenile mortality from grazing urchins were high. Differences in settlement and early survival of Porites spp. are exacerbated by different regimes of storm damage. A model is proposed that links wave climate with the size and age reached by corals before dislodgement by storm waves, and which is consistent with observed densities and size-frequency distributions of Porites in sheltered and exposed areas.     

Ciliated epibionts on the Arctic sympagic amphipod<Emphasis Type="Italic"> Gammarus wilkitzkii</Emphasis> as indicators for sympago–benthic coupling

In September 2003 specimens of the sympagic amphipod Gammarus wilkitzkii were sampled in drifting pack ice above 50 m water depth and in the pelagic/benthic environment beneath in the coastal waters off Svalbard (Norway). Abundance values ranged between 1.5 and 8 individuals m^–2 for the pelagic/benthic and the sympagic environments, respectively, and showed corresponding sex ratios of 1:1.4, favoring males. In the ice a significantly higher number of juveniles prevailed. In contrast, ovigerous females were more abundant among pelagic/benthic living specimens. Approximately 25% of the individuals hosted ciliated epibionts of the genera Ephelota, Cryptacineta, Acineta, Podophrya (all suctoria), and Epistylis (peritrichia). Cryptacineta and Ephelota were the most abundant epibionts on this amphipod species. Female specimens of G. wilkitzkii showed the highest degree of infestation (>2,100 individual epibionts per amphipod specimen: indE/A) followed by juveniles (>1,200 indE/A) and males (>220 indE/A). Highest densities of epibionts were found on anterior body parts with the antennae bearing up to 130 individuals. This is the first sighting of epibionts on crustacea from the sympagic environment. We interpret them as biomarkers that indicate the existence of sympago–benthic coupling processes between the ice and the underlying waters and the seafloor. The population structure and the proportion of infested specimens are equal for the amphipods sampled from both the sympagic and the pelagic/benthic environment, indicating the existence of exchange (coupling) processes between the two habitats. Considering the annual ice cycle, local ice drift patterns, and the shallow water depth in the sampling area, we hypothesize that ice amphipods spend ice-free periods near the seafloor where they may serve as basibionts for protozoans and eventually re-colonize the ice with the onset of ice formation. Our observations strongly emphasize that shallow coastal areas serve as both retention (rather than sink) areas for ice fauna during ice-free periods, and as stepping-stones for re-colonizing the ice when the ice is formed in winter.Communicated by M. Kühl, Helsingor     

Vertical distribution and feeding patterns of midwater fish in the central equatorial Atlantic II. Sternoptychidae

The vertical distribution of seven sternoptychid species was examined from RMT 1+8 samples collected aboard R. V. Meteor in March-April 1979 and from Royal Research Ship R.R.S. Discovery in July 1974 in the central equatorial Atlantic. During daytime sternoptychids occupied depths between 200 and 1250 m, with Sternoptyx pseudobscura living deepest, centering between 800 and 900 m, and Argyropelecus sladeni most shallow, aggregating predominantly at 300 and 400 m. They are all considered limited or partial migrants, ascending only some 100 and 200 m towards the surface at night. Only A. sladeni was observed to enter the epipelagic zone (0 and 200 m).-Feeding patterns were investigated from stomach content analyses of Sternoptyx diaphana, S. pseudobscura, Argyropelecus sladeni and A. affinis. Additional stomach contents were analysed from samples of S. diaphana, A. hemigymnus and A. olfersi collected in June 1985 from F.R.V. Walther Herwig in the temperate NE Atlantic at 46°N, 17°W by means of the Engel Trawl. The food spectrum of the six species is generally described, and additional dietary evidence regarding calanoid copepod prey is provided for four of these taxa. All sternoptychid species investigated were planktivorous, feeding predominantly on copepods and ostracods, except for the largest size class, which preyed heavily on euphausiids and amphipods. The relationship of predator size towards prey type and prey size is analysed for both Sternoptyx species. Of these, S. pseudobscura in particular exhibits taxonomic selectivity towards polychaete prey. The diet of both species of Sternoptyx included a number of epipelagic or even neustonic calanoid copepod species which contributed more than 50% of the total copepod population by numbers. So far it is not known how the predators find access to prey organisms of the upper 200 m, as netfeeding is considered unlikely. Cyclopoid copepods of the genus Sapphirina were observed as dietary component particular of S. diaphana.     

Distribution of deep-water gorgonian corals in relation to benthic habitat features in the Northeast Channel (Atlantic Canada)

The distribution and abundance of deep-water gorgonian corals were investigated along 52 transects at 183–498 m depth in the Northeast Channel, between Georges Bank and Browns Bank in the northwest Atlantic, using a remotely operated vehicle and a towed video-camera system. Three species (Paragorgia arborea, Primnoa resedaeformis, and Acanthogorgia armata) were observed. Primnoa occurred on 35 transects below 196 m depth, with highest local abundance in stands of 104 colonies per 100 m². Paragorgia was present on 21 transects deeper than 235 m, with highest local abundance of 49 colonies per 100 m². Acanthogorgia was observed at only four transects between 231 m and 364 m, with a local maximum abundance of 199 colonies per 100 m². The maximum abundance averaged for whole transects was 19.2 and 6.2 colonies per 100 m² for Primnoa and Paragorgia, respectively. The corals were more common in the outer part of the channel along the shelf break and slope than on the shelf in the inner part. All three species showed a patchy distribution with no signs of competitive exclusion at any spatial scale. Transects with high abundance of corals were characterised by depths greater than 400 m, maximum temperatures less than 9.2°C, and a relatively high percentage coverage of cobble and boulder (more than 19% and 6%, respectively). High temperatures probably control the upper depth limit of the corals, and Primnoa seems to tolerate slightly higher temperatures than Paragorgia. Abundance of both species was negatively correlated with average temperature and positively with cobbles. Together, temperature, percentage cobble and salinity accounted for 38% of the variance of Primnoa. The comparable figure for Paragorgia was 15%. The observed distribution indicated that the abundance of coral is controlled by additional factors such as larger-scaled topographic features governing the current regimes and thus also the supply of food and larvae.Communicated by R. J. Thompson, St. Johns     

The enantiomeric composition of monoterpene hydrocarbons in the defensive secretions ofNasutitermes termites (Isoptera): Inter- and intraspecific variations

Summary Frontal gland secretions of termite soldiers of the speciesNasutitermes costalis, N. ephratae, N. nigriceps, N. rippertii, andN. hubbardii were analyzed. The chiral compositions of the monoterpene hydrocarbons were investigated by means of two-dimensional gas chromatography. Two of them, 3-carene and-pinene were present in the form of (–)-enantiomers of high purity in the majority of the samples. The other monoterpenes,-pinene, camphene, sabinene, limonene, and-phellandrene, exhibited a great variation in the enantiopurity between different species.-Pinene and limonene varied significantly even between different colonies within the species.N. costalis was the only species with an invariable composition of the secretion, independent of the locality or origin.     

Genetic distances among fishes of the genus Siganus (Siganidae) from the Western Pacific Ocean

Frequencies of electromorphs encoded by 14 polymorphic loci were used to estimate genetic distances among samples of the rabbitfishes Siganus argenteus, S. doliatus, S. fuscescens, S. guttatus, S. javus, S. punctatus, S. randalli, S. spinus, S. vermiculatus, and S. (Lo) vulpinus. Samples of the surgeonfish Naso lituratus (Acanthuridae) were included in the electrophoretic survey for the purpose of outgroup comparison. A matrix of genetic-distance estimates was used for construction of dendrograms by neighbor-joining, complete-linkage and single-linkage procedures, and the unweighted pair-group method of arithmetic averages (UPGMA). Cluster analysis revealed interspecific relationships that are concordant with several predictions intimated in the most recent taxonomic revision of this assemblage of fishes. S. randalli and S. vermiculatus, the pair postulated to be sibling species on the basis of strikingly similar external morphology, were found to exhibit the lowest levels of genetic divergence relative to all other pairs of study species. S. randalli, S. guttatus, and S. vermiculatus comprised one of three clusters discerned in all resultant topologies (i.e., ball clusters). S. argenteus, S. fuscescens, and S. spinus, three fusiform-bodied species, formed a second ball cluster that was clearly separable from the remainder of the siganids studied (which are all relatively deep-bodied). A third ball cluster contained S. punctatus and S. vulpinus: S. doliatus was depicted as being allied with S. punctatus and S. vulpinus in the neighbor-joining and complete-linkage topologies but not in topologies generated by UPGMA and single linkage. It is noteworthy that S. punctatus, S. vulpinus, and S. doliatus are the only three species included in the present study which purportedly school when young but form pair-bonds as adults. In all topologies, S. javus occupied branches stemming from furcation points between fusiform-bodied and deep-bodied species. Of all the siganids studied, S. argenteus was found to be least divergent genetically from N. lituratus. S. argenteus is the only siganid known to spawn pelagic eggs and undergo a specialized pelagic stage (features typical within the Acanthuridae). Hence, genetic relationships within the Siganidae and among the Siganidae and a representative acanthurid coincide with a host of predictions stemming from morphologic and life-history studies of the Acanthuroidei.     

Resource translocation in a marine bryozoan: quantification and visualization of 14C and 35S

Colonial marine invertebrates are characterized by their ability to share resources among the modules of a colony. In most colonial groups, but particularly the Bryozoa, the dynamics of resource transport among modules is unknown. We developed radioisotope techniques to visualize and quantify the movement of carbon and sulfur-based compounds within colonies of the marine bryozoan Membranipora membranacea. The research was conducted in 1991 and 1992 in Friday Harbor, Washington, USA. Autoradiography, using X-ray film, was used to visualize the transport of both ¹⁴C and ³⁵S, and a liquid scintillation counter was used to quantify transport of metabolites. We were able to localize feeding by introducing 10 l aliquots of labelled algal cells with a microinjection syringe into a containment ring on the surface of the colony. The labelled cells were consumed by zooids feeding within the ring, but not by those outside. In time-course within the ring, but not by those outside. In time-course experiments, 15% of the ingested carbon radioisotope was transported from a source in the center of the colonies to the growing edges over a period of 48 h. Approximately 10% of the sulfur was transported from central to edge regions of colonies over 72 h. Transport of carbon isotope was unidirectional in all experiments, irrespective of whether colonies were fed near the edge or the center. Pulse-chase experiments revealed that up to 46% of the initial ¹⁴C radioisotope was lost from the colony to respiration and egestion in the 24 h following ingestion.     

Benthic and pelagic fish biomass of the upper continental slope off eastern Tasmania

Benthic and pelagic fishes were sampled east of Maria Island, Tasmania, at two-monthly intervals from April 1984 to June 1985, from the surface to the bottom (500 m depth), using commercial-sized trawls. Biomass was calculated by the area swept/volume filtered method and divided by estimated catchability coefficients so that catches from the two sampling gears could be combined. Of the 54 families caught, three (Myctophidae, Squalidae, Sternoptychidae) contributed 25% of the 115 species. Most benthic and dispersed species were caught regularly, whereas most pelagic species occurred only occasionally and in low numbers, although a core group was always present. Total fish biomass was high (range=77 to 532 g m^-2; x= 390 g m^-2), due almost entirely to the myctophid Lampanyctodes hectoris (over 90% of the biomass). Benthic biomass was relatively low and stable, but derived from many species. Pelagic biomass was high, fluctuated widely and was composed of a few species. Biomass was highest in summer: Maurolicus muelleri increased by a factor of 200, Diaphus danae by 50, and L. hectoris, Macruronus novaezelandiae and Lepidorhynchus denticulatus by almost 10. Peaks in biomass may correlate with the interactions of the subtropical convergence and the East Australian Current and the resultant marked seasonal cycle in water temperature, nutrients and primary productivity.With an appendix by T.J. Kenchington, CSIRO Division of Fisheries, Hobart, Tasmania 7001, Australia     

Zooid size parallels contemporaneous oxygen isotopes in a large colony of<Emphasis Type="Italic"> Pentapora foliacea</Emphasis> (Bryozoa)

The relationship between seasonal changes in temperature and the size of zooids within cheilostome bryozoans is explored by comparing zooid size and contemporaneous carbonate mineralogy within a single colony of a perennial species that grew in a highly seasonal environment. Previously published oxygen isotope profile data from two fronds of a large colony of Pentapora foliacea from the Irish Sea record the cyclical patterns related to seasonal changes in temperature experienced by the colony over 3 years of growth. Zooid size data gathered from the same points at which the oxygen isotope data were taken reveal that zooid size and contemporaneous ¹⁸O values covary. These and previously published data show that zooid size profiling can be confidently used to easily estimate rates of growth and longevity of bryozoan colonies, and further illustrate the negative relationship between zooid size and ambient temperature. Some inconsistencies in timing between zooid size and ¹⁸O data may provide insights into the mechanisms behind temperature mediated body size changes in poikilothermic animals.Communicated by P. W. Sammarco, Chauvin     

Sex ratios in bumble bee colonies: Complications due to orphaning?

Summary Highly male-biased investment ratios (1:2.86, F:M, biomass wet weight) were found among reproductives reared by 32 Bombus terricola colonies set out in the field and 35 B. melanopygus colonies held in laboratory confinement. The numerical sex ratios were almost identical for the two species (1 queen to 6.1 males). Most of the males were produced early in the season by small weak colonies. It is argued that in a population where some colonies are orphaned and rear only males, female-biased sex ratios are expected among the surviving queen-producing colonies.     

Interspecific aggression in colonies of the slave-making ant Harpagoxenus sublaevis

Colonies of the slave-making ant, Harpagoxenus sublaevis, may simultaneously contain workers of several Leptothorax slave species. We observed aggressive interactions among slave-makers, between slavemakers and slaves, and among slaves in 11 mixed colonies. The first two types of aggression appear to be correlated with reproductive competition for the production of males. Aggressive interactions among slaves, however, occurred mainly between slaves belonging to different species. In two colonies, in which one slave species clearly outnumbered the other, the majority attacked and finally expelled all nestmates belonging to the minority species. Our observations thus suggest that in Harpagoxenus colonies a homogeneous colony odor is not always achieved and that heterospecific slaves may occasionally be mistaken for alien ants. Gas chromatographic analyses of ants from mixed colonies similarly show that cuticular hydrocarbon profiles may differ strongly between heterospecific nestmate slaves.     

Lipids and stable carbon isotopes in two species of Hawaiian corals,<Emphasis Type="Italic"> Porites compressa</Emphasis> and<Emphasis Type="Italic"> Montipora verrucosa</Emphasis>, following a bleaching event

Mass coral bleaching events have occurred on a global scale throughout the worlds tropical oceans and can result in large-scale coral mortality and degradation of coral reef communities. Coral bleaching has often been attributed to periods of above normal seawater temperatures and/or calm conditions with high levels of ultraviolet radiation. Unusually high shallow-water temperature (>29°C) in Kaneohe Bay, Hawaii, USA, in late summer (20 August–9 September) and fall (1–7 October) of 1996 produced visible bleaching of two dominant corals, Porites compressa Dana, 1864 and Montipora verrucosa Dana, 1864. The present study examined chlorophyll a (chl a), total lipid concentrations, and lipid class composition in corals of both species in which the entire colony was non-bleached, moderately bleached, or bleached. Skeletal, host tissue, and algal symbiont ¹³C values were also measured in non-bleached and bleached colonies. In additional unevenly bleached colonies, paired samples were collected from bleached upper surfaces and non-bleached sides. Samples were collected on 20 November 1996 during the coral recovery phase, a time when seawater temperatures had been back to normal for over a month. Chl a levels were significantly lower in bleached colonies of both species compared with non-bleached specimens, and in bleached areas of unevenly bleached single colonies. Total lipid concentrations were significantly lower in bleached P. compressa compared with non-bleached colonies, whereas total lipid concentrations were the same in bleached and non-bleached M. verrucosa colonies. The proportion of triacylglycerols and wax esters was lower in bleached colonies of both species. Both bleached and non-bleached M. verrucosa had from ~17% to 35% of their lipids in the form of diacylglycerol, while this class was absent in P. compressa. ¹³C was not significantly different in the host tissue and algal symbiont fractions in non-bleached and bleached samples of either species. This suggests that the ratio of carbon acquired heterotrophically versus photosynthetically was the same regardless of condition. Skeletal ¹³C was significantly lower in bleached than in non-bleached corals. This is consistent with previous findings that lower rates of photosynthesis during bleaching results in lower skeletal ¹³C values. The two species in this study displayed different lipid class compositions and total lipid depletions following bleaching, suggesting that there is a difference in their metabolism of lipid reserves and/or in their temporal responses to bleaching and recovery.Communicated by J.P. Grassle, New Brunswick     

Feeding habits of marine cladocerans in the Inland Sea of Japan

Natural food items of five species of marine cladocerans, Evadne nordmanni, E. tergestina, Penilia avirostris, Podon leuckarti and P. polyphemoides, were investigated in the Inland Sea of Japan between April 1986 and May 1987. Gut content examination with SEM (scanning electron microscopy) revealed that feeding was largely limited to centric diatoms and a few exceptions of pennate diatoms and dinoflagellates. No animal remains were detected, and some unidentified materials were also found. Phytoplankton smaller than 35 m in size (cell diameter in centric diatoms and longest dimension in others) was found most frequently in the gut of cladocerans. The role of grazing of marine cladocerans in trophodynamic pathways of the pelagic realm is discussed.     

Three party symbiosis: acoelomorph worms,corals and unicellular algal symbionts in Eilat (Red Sea)

Epizoic worms were found to occur on certain coral colonies from reefs off the coast of Eilat (Red Sea). We identified 14 coral species infested by acoelomorph worms at a depth range of 2–50 m. The host corals were all zooxanthellate and included both massive and branching stony corals and a soft coral. Worms from all hosts were identified as belonging to the genus Waminoa and contained two distinct algal symbionts differing in size. The smaller one was identified as Symbiodinium sp. and the larger one is presumed to belong to the genus Amphidinium. Worm-infested colonies of the soft coral, Stereonephthya cundabiluensis, lacked a mucus layer and exhibited distinct cell microvilli, a phenotype not present in colonies lacking Waminoa sp. In most cases, both cnidarian and Acoelomorph hosts displayed high specificity for genetically distinctive Symbiodinium spp. These observations show that the epizoic worms do not acquire their symbionts from the “host” coral.     

Genetic evidence for cryptic speciation in the marine bryozoan Alcyonidium gelatinosum

The common subtidal marine bryozoan Alcyonidium gelatinosum (L.) is one of the most confusing species of a taxonomically very difficult genus. It shows massive variation for almost all morphological characters. A number of sympatric colonies collected off the coast of Lundy (Bristol Channel) could be clearly divided on morphological grounds into two quite distinct types. Using starch gel electrophoresis the products of a range of genetic enzyme loci were compared between the two morphotypes and also between these and other Bristol Channel populations of A. gelatinosum. Minimal differences were observed between one Lundy morphotype and the other allopatric populations, which it was consequently concluded were conspecific. The second morphotype showed considerable genetic differentiation [genetic identity (Nei, 1972) =0.417] from the other Lundy population, with no common alleles at some loci. The probability of obtaining the observed results by chance in a single population is significantly low (P<10^–14). It is therefore concluded that the two morphotypes of A. gelatinosum from Lundy are not conspecific.