Invertebrate and protozoan epibionts on the velvet swimming crab Liocarcinus puber (Linnaeus, 1767) from Scotland

Invertebrate and ciliate protozoan epibionts of velvet swimming crabs collected near Millport (Scotland) were analysed. The ecdysis peak for male crabs was at the time of collection while that for female crabs was 2 months later. The epibionts were: the polychaetes Pomatoceros triqueter and Hydroides norvegica, the cirriped Balanus crenatus, the entoproct Barentsia matsushimana, the hydroids Leuckartiara sp. and Clytia sp., and the ciliate protozoans Ephelota plana, Ephelota gemmipara, Chilodochona quennerstedti and Cothurnia longipes. The polychaetes, cirripeds, entoprocts and hydroids, all of them with comparatively larger size, were distributed on the carapace, ventral surface of the cephalothorax and the pereiopods; meanwhile the protozoans, with smaller size, were attached also on pleopods, antennae, eyes and buccal appendages. Chilodochona quennerstedti was the epibiont most abundant on the crab, followed by Ephelota plana. Cothurnia longipes was, in contrast, the least abundant epibiont, followed by Barentsia matsushimana. The anatomical unit most colonized was the left third maxilliped, followed by the left first maxilliped and the ventral surface. The less colonized anatomical units were the left antenna and the ocular orbits. Epibionts on this crab have not been described before. Statistical analyses of the epibiont distribution on the crab were carried out. There were significant correlations between right and left appendages in 66.67% of the cases. Males and females differed significantly with respect to the distribution of epibionts on their anatomical units. The comparison analysis indicated a significant differential distribution of each epibiont species on the anatomical units of the crab. Principal component analysis grouped the epibiont species according to their colonization pattern in three clusters: (1) Ephelota plana, Ephelota gemmipara and Chilodochona quennerstedti; (2) Leuckartiara sp., Clytia sp., Barentsia matsushimana and Cothurnia longipes; and (3) Pomatoceros triqueter, Balanus crenatus and Hydroides norvegica. The hierarchical cluster analysis grouped the anatomical units of the crab in relation to their colonization in five clusters.     

Hydrozoan and protozoan epibionts on two decapod species, Liocarcinus depurator (Linnaeus, 1758) and Pilumnus hirtellus (Linnaeus, 1761), from Scotland

Crabs of the species Liocarcinus depurator and Pilumnus hirtellus, collected on the west coast of Scotland, showed hydrozoan and protozoan epibionts. The epibionts of Liocarcinus depurator were the protozoan Ephelota plana and the hydrozoans Clytia gracilis and Leuckartiara sp. The epibionts of Pilumnus hirtellus were the protozoans E. plana and Zoothamnium sp. For Liocarcinus depurator the number of Ephelota per crab fluctuated between 0 and 47 and the greatest number of suctorians were located on the chelipeds, carapace and anterior pereiopods. The hydrozoans, for Liocarcinus depurator, showed densities of 0-20 (Clytia gracilis on the second pereiopod) and 0-507 individuals per crab (Leuckartiara sp., principally on chelipeds, carapace and the fourth right pereiopod). For Pilumnus hirtellus, Ephelota plana showed densities between 3 and 56 individuals per crab, the greatest number of suctorians being located on the same areas as on Liocarcinus depurator. There was a density of 10-69 individuals per crab of Zoothamnium sp. on Pilumnus hirtellus (located on the carapace). Ephelota plana has not been observed previously as an epibiont on crustacea, nor had Zoothamnium sp. as an epibiont on Pilumnus hirtellus. Both hydrozoans, Leukartiara and Clytia, have not been previously described as epibionts on Liocarcinus depurator. Data about the morphological characteristics and distribution of these epibionts are included.     

Taxonomy and distribution of the hydrozoan and protozoan epibionts on Pagurus bernhardus (Linnaeus, 1758) (Crustacea, Decapoda) from Scotland

Protozoan and hydrozoan epibionts on the hermit crab Pagurus bernhardus and its shell, collected near Cumbrae Island (Scotland) were studied. The epibionts found were the following: (1) protozoans: the suctorian ciliates Ephelota plana, Acineta compressa, Conchacineta constricta, Corynophrya anisostyla; the peritrich ciliates Cothurnia mobiusi and Zoothamnium plumula; the chonotrich ciliate Chilodochona quennerstedti; and (2) hydrozoans: the species Leuckartiara sp. and Clytia sp. The morphological characteristics of the epibionts were analysed, as well as their taxonomic position. The distribution of epibionts on the crab surface and its shell was studied, and the density and biomass of epibionts were calculated on each anatomic unit. There was a differential distribution according to the type of epibiont: hydrozoans dominated in biovolume and were present mainly on the shell, meanwhile protozoans represented the highest fraction of density and they were found exclusively on the crab (principally on eyes, antennulae, antennae, maxillipeds, pereopods and uropods). The anterior area of the cephalothorax was the most colonized. On this area, the maxillipeds and second pereopods showed the highest densities. The location of each epibiont species was described. There was a correlation between the length of the crab and the total number of hydrozoans. There was a significant correlation between the right and the left units of the crab, taking into consideration the mean densities of epibionts on each anatomical unit. The shell was colonized by the same species of hydrozoa that appeared on the crab, although in a much higher density (mean 3024.38 per shell; 6.9 per crab). There was a significant difference between both species of hydrozoan epibionts with respect to the mean densities on the different areas of the shell. The zone of the shell more occupied by Clytia sp. was the apical zone of the shell, while the highest densities of Leuckartiara sp. were registered near the aperture of the shell. The hydrozoan and protozoan epibiont species found on P. bernhardus in this study represent the first mention of their presence on this hermit crab.     

Effects of epibiosis on consumer–prey interactions

In many benthic communities predators play a crucialrole in the population dynamics of their prey. Surfacecharacteristics of the prey are important forrecognition and handling by the predator. Because theestablishment of an epibiotic assemblage on thesurface of a basibiont species creates a new interfacebetween the epibiotized organism and its environment,we hypothesised that epibiosis should have an impacton consumer–prey interactions. In separateinvestigations, we assessed how epibionts onmacroalgae affected the susceptibility of the latterto herbivory by the urchin Arbacia punctulataand how epibionts on the blue mussel Mytilusedulis affected its susceptibility to predation bythe shore crab Carcinus maenas.Some epibionts strongly affected consumer feedingbehavior. When epibionts were more attractive thantheir host, consumer pressure increased. Whenepibionts were less attractive than their host or whenthey were repellent, consumer pressure decreased. Insystems that are controlled from the top-down,epibiosis can strongly influence community dynamics.For the Carcinus/Mytilus system that westudied, the in situ distribution of epibiontson mussels reflected the epibiosis-determinedpreferences of the predator. Both direct and indirecteffects are involved in determining theseepibiont-prey–consumer interactions.     

Potential effect of floating dock communities on a South Carolina estuary

A 4-yr study on the motile epibionts colonizing hydroids on a floating dock in a South Carolina estuary indicated that the motile epibiotic community may impact benthic and nektonic community processes. Permanent members of the epibiotic community were preyed upon by fish, especially when the Atlantic silverside (Menidia menidia (L.)) became reproductively active and deposited eggs among the hydroids during the spring. When fish predation reduced the number of amphipods within the epibiotic community, crab megalopa colonized the hydroids. Crabs developed into juveniles and emigrated from the epibiotic community after 6–8 wk residence. The community on floating docks may be an important food source for some nekton and may recruit some benthic invertebrates.Although preferential larval settlement and fish predation are intuitive processes associated with floating dock communities, insufficient research has addressed the relationships in soft-bottom areas devoid of naturally occurring hard substrata.     

Fouling community of the red king crab, <Emphasis Type="Italic">Paralithodes camtschaticus</Emphasis> (Tilesius 1815), in a subarctic fjord of the Barents sea

We examined the species composition of red king crab (Paralithodes camtschaticus) fouling communities in Dolgaya Bay, a small fjord of the Barents Sea, in August 2005 and 2006. In total, there were 13 species observed on 301 crabs collected from water depths of 5–90 m. Barnacles (Balanus crenatus; prevalence 42.9%) and blue mussels (Mytilus edulis; 11.6%) were the most common epibionts, while amphipods (Ischyrocerus commensalis) were the most common symbionts (28.6%). Infestation rates in Dolgaya Bay were different from those in an “open” area of the Barents Sea (Dalnezelenetskaya Bay), probably due to differences in hydrodynamic conditions. Differences in infestation prevalence and intensity were detected neither between male and female crabs nor between crabs collected at 5–35 m versus 90 m depths. Prevalence of common fouling species increased with host size. Amphipods I. commensalis colonized the carapace and limbs in Dolgaya Bay less frequently than in Dalnezelenetskaya Bay, probably due to interspecific competition with barnacles occupying the dorsal parts of the host. Juvenile barnacles and mussels dominated the fouling communities on the crabs. The age of barnacles did not exceed 2–4 months. However, the presence of 4-year-old mussels suggests that these older mollusks have been directly transferred from mussel beds to the hosts. Our results indicate that colonization by epibionts and symbionts is generally not disadvantageous for the crab hosts, except for some possible negative impacts of amphipods occupying the gills.     

The shell of <Emphasis Type="Italic">Hexaplex (Trunculariopsis) trunculus</Emphasis> (Gastropoda: Muricidae) as a mobile hard substratum for epibiotic polychaetes (Annelida: Polychaeta) in the Ria Formosa (Algarve coast—southern Portugal)

This work reports and illustrates secondary colonisation of Hexaplex (Trunculariopsis) trunculus shells by polychaetes in the Ria Formosa lagoon (Algarve coast—southern Portugal). Information is presented in terms of qualitative and quantitative data on epibiotic polychaetes, fouling frequency, degree of epibiosis, preferential areas for colonisation and incidence of shell damages. A total of 2,880 polychaetes belonging to 10 families were identified. Besides Spirorbidae (not quantified), the most abundant families were Serpulidae (67.5%), Sabellidae (10.2%), Sabellariidae (9.6%) and Cirratulidae (8.5%). From a total of 2,264 T. trunculus individuals analysed for epibiosis, 28.4% were non-fouled, 66.8% were intermediately fouled and 4.8% were heavily fouled. The fouling frequency, degree of epibiosis and incidence of damages in the shell spire increased markedly with T. trunculus shell length. Some epibiotic polychaetes were located preferentially on/or nearby particular features of T. trunculus shells, which probably facilitate settlement and tube construction, in addition to provide some protection against tube damage. The main consequences of epibiosis (benefits and disadvantages) for the gastropod basibiont (T. trunculus) are discussed. The present study apparently indicates that besides burrowing into soft bottom substrates, sporadic inter-tidal exposure and mutual predation on epibiosis, T. trunculus lacks other typical antifouling defence adaptations. Handling editor: K. Martens     

Spatial and temporal occurrence of Rhabdostyla cf. chironomi Kahl, 1933 (Ciliophora, Peritrichia) as an epibiont on chironomid larvae in a lotic system in the neotropics

In order to show how environmental factors could influence the spatial and temporal distribution of epibiosis, we investigated the occurrence of the ciliate Rhabdostyla cf. chironomi (Ciliophora, Peritrichia) attached to Chironomidae larvae in an urban stream in southeast Brazil. Samples were collected monthly for 1-year period at five sampling stations along the stream. Among the 24 genera analyzed, the genus Chironomus was the most abundant, with 16.84% carrying R. cf. chironomi. This epibiotic relationship was only recorded in sample stations located in a heavily populated urban area of the stream. Statistical analyses demonstrated significant correlations between infestation prevalence and environmental parameters such as rainfall, bacterial density, and host abundance. The occurrence of epibionts on the larvae was spatially and temporally heterogeneous. The results are discussed in terms of possible factors related to the heterogeneous spatial and temporal occurrence. Greater understanding of the ecological factors governing the occurrence of the epibiont–host relationship is essential to establish future use of this relationship as water quality indicator in lotic systems.     

Epibionts on the krill (Euphausia pacifica) from the E coast of Japan

Fernandez‐Leborans, G. 2011. Epibionts on the krill (Euphausia pacifica) from the E coast of Japan. —Acta Zoologica (Stockholm) 00 : 1–10. Specimens of Euphausia pacifica collected from shallow waters of the E coast of Japan showed ciliate epibionts belonging to two suctorian species: Ephelota plana and Gymnodinioides sp. The epibionts were present in a total of 27 anatomical units of E. pacifica, in numbers fluctuating between 8 and 80 individuals per basibiont. Gymnodinioides showed the highest mean number of epibionts. The presence–absence of epibionts indicated some specificity of the species by different locations on the basibiont body, which is corroborated by the analysis of the colonization throughout the longitudinal axis of the basibiont. Ephelota plana was recorded by the first time on E. pacifica, while Gymnodinioides sp. extended its geographical area with respect to previous studies. Morphological, taxonomical features of the species and the statistical analysis of their spatial distribution on E. pacifica are included.     

The effect of epibionts on the susceptibility of the red seaweed Cryptonemia seminervis to herbivory and fouling

Epibiosis or fouling on living organisms can have direct and indirect detrimental effects, in particular on photosynthetic organisms such as seaweeds. It thus seems reasonable to hypothesize that macroalgae have been selected for the presence or induction of antifouling (AF) defences. The red seaweed Cryptonemia seminervis is usually found in nature with an elevated cover of epibionts. To assess the effect of epibiosis on the susceptibility of this seaweed to herbivory and fouling, the abundance of fouling was evaluated and compared to herbivore consumption (by amphipods and sea urchins) of fouled (bryozoan and sponge) and non-fouled C. seminervis. Attachment of the mussel Perna perna to surfaces treated with extracts from seaweeds with and without epibionts was also assessed. Epibiosis corresponded to ca. 51% of the blade surface of C. seminervis, sometimes covering as much as 90% and up to 51% of the thallus weight, encompassing mainly the bryozoan Membranipora membranacea and an unidentified sponge. Algae colonized by M. membranacea were preferred compared to algae devoid of epibionts, a ‘shared doom’ effect, either by the amphipod Elasmopus brasiliensis or by the urchin Lytechinus variegatus (p < 0.01). Sponge epibiosis also increased consumption by both herbivores (p < 0.001), suggesting that epibionts may act as lures to herbivores, attracting consumers that otherwise would not feed significantly on the seaweed. Foods containing extracts from fouled C. seminervis were preferred by urchins over the alga devoid of epibionts. However, extracts from fouled alga inhibited mussel attachment when compared to epibiont-free alga. Differences might be a direct detrimental effect of the presence of epibionts. On the other hand, epibiosis may induce the production of AF defences in C. seminervis.     

First record of an epibiosis between the sand crab Emerita analoga (Stimpson, 1857) (Decapoda: Hippidae) and the mussel Semimytilus algosus (Gould, 1850) (Bivalvia, Mytilidae) in southern Peru

Coastal zones of the Humboldt Current Upwelling System (HCUS) are composed both of rocky and sandy beaches inhabited by macrozoobenthic communities. These show oscillating changes in the dominance of species; the abundance of the sand crab Emerita analoga is linked to phases of the El Niño Southern Oscillation (ENSO). The biogenic surfaces of these crabs serve as substrate for opportunistic colonizers. This study is the first record of an epibiosis between E. analoga and the rock mussel Semimytilus algosus, detected at a southern Peruvian sandy beach. Mussels fouled a wide size-range of adult E. analoga (7.3%) but they themselves belonged to small-size classes. The largest S. algosus was 17.4 mm in length. Highest permanence of epibionts was found on larger sand crabs (maximum between 24 and 27 mm). Significantly more mussels were found on the ventral surface (39.4%) compared to 10 other surface areas of the sand crab. Possible benefits and disadvantages of the observed epibiosis for both the basibiont and the epibiont are discussed.     

Biodiversity and distribution of epibiontic communities on Caridina ensifera (Crustacea,Decapoda, Atyidae) from Lake Poso: comparison with another ancient lake system of Sulawesi (Indonesia)

Fernandez‐Leborans, G. and von Rintelen, K. 2010. Biodiversity and distribution of epibiontic communities on Caridina ensifera (Crustacea, Decapoda, Atyidae) from Lake Poso: comparison with another ancient lake system of Sulawesi (Indonesia). — Acta Zoologica (Stockholm) 91 : 163–175 The epibiont communities of the shrimp Caridina ensifera, endemic to Lake Poso (Sulawesi, Indonesia), were analysed. Most of the epibiont species were ciliated protozoa belonging to three suctorian genera (Acineta, Podophrya and Spelaeophrya), three peritrich genera (Zoothamnium, Vorticella and Cothurnia), and a haptorid genus (Amphileptus). There was also a rotifer epibiont of the genus Embata. Epibionts were identified to species level. There were 14 to 1114 epibionts per shrimp. The distribution of the epibiont species on the surface of the basibiont was recorded, calculating the number on the different colonized individuals of C. ensifera. The most abundant species, Zoothamnium intermedium and Acineta sulawesiensis, were also the most widely distributed. There was a significant difference between the spatial distributions of the different epibiont species. The analysis of the number of the epibiont species throughout the anteroposterior axis of the shrimp showed a gradient from the anterior to the posterior end of the body. Data from Lake Poso were compared with those of the Malili lake system (Sulawesi), obtained from its endemic shrimp, Caridina lanceolata. Lake Poso had the highest mean diversity, while Lake Mahalona showed the highest maximum diversity. All lakes were correlated with respect to the mean number of epibionts on the anatomical units of the shrimp, which showed a similar general distribution. The distributions of the different epibiont species were compared between the lakes. The possible adaptations of the epibionts as well as the colonization patterns were discussed. From the statistical results and the analysis of the distributions, we propose that in these communities epibiont species have a pattern of colonization in which they follow a behaviour as a whole; each species has a differential distribution, with the species occupying the available substratum with the particular requirements of each functional group, but there is a trend towards maintaining an equilibrium among species and groups, compensating for diversity and number of individuals. In all lakes there was an epibiont distribution model comprising the maintenance of an anteroposterior axis gradient, which was supported by the fluctuation in diversity and number of individuals of the different functional groups of epibiont species. The functional role of the different groups of species seems to tend towards sustainability with little global variation among the lakes.     

Molecular evidence of digestion and absorption of epibiotic bacterial community by deep-sea crab Shinkaia crosnieri

The hydrothermal vent crab Shinkaia crosnieri is considered to obtain nutrition from the epibiotic bacteria found on the setae, but previous studies have not shown how nutrients can be transferred from the epibionts to the host. In this study, microscopic observations of S. crosnieri intestinal components detected autofluorescent setae fragments and pigmentation derived from the digestion of epibionts in a dye-stained epibiont tracer experiment. An in vitro digestion experiment with epibiotic populations using an intestinal extract demonstrated the degradation of epibiotic cells by digestive enzymes. A phylogenetic analysis showed that many of the bacterial 16S ribosomal RNA gene sequences obtained from the intestine were closely related to the sequences of the epibionts, thus they were probably derived from the epibionts. A stable isotope tracer experiment also indicated that ¹³C assimilated by the epibionts provided a carbon (nutrition) source for the host. Both activity measurements and isotope studies showed that chemosynthetic metabolism by the gut microbial components were inactive. Together with the feeding behaviour of living S. crosnieri, these results indicate that S. crosnieri ingests the epibionts using maxillipeds and assimilates them via its digestive organs as a nutrient source. The results of this study elucidate the mechanism of nutritional transfer in ectosymbiosis between chemosynthetic bacteria and deep-sea invertebrates.     

Epibiotic macroalgae on the scallop <Emphasis Type="Italic">Mizuhopecten yessoensis</Emphasis> in Peter the Great Bay,Sea of Japan

The composition and structure of the epibiotic flora of the Japanese scallop Mizuhopecten yessoensis were studied on the basis of data from long-term (1979 to 2007) observations on the scallop beds in Peter the Great Bay (Sea of Japan). In all, 52 species of macroalgae belonging to three phyla were found on the scallop shells; 3 species were new records for the benthic flora of the area studied. Red algae constituted the bulk of the species richness of algal epibionts; brown algae were represented by the lowest number of species. Species of Chlorophyta predominated in terms of biomass; species of Rhodophyta were found in lower numbers. The main form of the thallus of epibiotic algae was bushy or filamentous. The ratio of common to rare species was 30 : 70. As compared to the benthic flora, the epibiotic flora on the scallop shells was characterized by a greater number of warm-water species.     

Associational resistance of fouled blue mussels (<Emphasis Type="Italic">Mytilus edulis</Emphasis>) against starfish (<Emphasis Type="Italic">Asterias rubens</Emphasis>) predation: relative importance of structural and chemical properties of the epibionts

Several epibiotic species reduce starfish (Asterias rubens) preference for the blue mussel Mytilus edulis in the Baltic. The aim of this study was to reveal whether this associational resistance was caused by structural or chemical aspects of the different epibionts. To assess structural epibiont effects, an in situ experiment was conducted with unfouled mussels and mussels equipped with artificial epibionts (dummies) exposed to natural predation by A. rubens. The chemically inert dummies closely matched the structural properties of the locally common epibionts Balanus improvisus (barnacle), Ceramium strictum (red alga), Halichondria panicea (sponge), and Laomedea flexuosa (hydrozoan). Starfish fed indiscriminately in all treatments. Chemical effects of epibionts on the attractiveness of mussels for A. rubens were investigated by incorporating freeze-dried epibionts or mussel tissue into Phytagel pellets at natural concentrations. Starfish were allowed to choose among these structurally similar but chemically different prey items in an in vitro experiment. The predators exhibited significant preferences among the food pellets, which closely matched their preferences for corresponding natural mussel–epibiont associations. Thus, chemical aspects of epibionts appear to play a larger role in this associational resistance than do structural aspects. Implications of these indirect interactions for benthic communities are discussed.Communicated by H.-D. Franke     

Dancing for food in the deep sea: bacterial farming by a new species of Yeti crab

Vent and seep animals harness chemosynthetic energy to thrive far from the sun's energy. While symbiont-derived energy fuels many taxa, vent crustaceans have remained an enigma; these shrimps, crabs, and barnacles possess a phylogenetically distinct group of chemosynthetic bacterial epibionts, yet the role of these bacteria has remained unclear. We test whether a new species of Yeti crab, which we describe as Kiwa puravida n. sp, farms the epibiotic bacteria that it grows on its chelipeds (claws), chelipeds that the crab waves in fluid escaping from a deep-sea methane seep. Lipid and isotope analyses provide evidence that epibiotic bacteria are the crab's main food source and K. puravida n. sp. has highly-modified setae (hairs) on its 3(rd) maxilliped (a mouth appendage) which it uses to harvest these bacteria. The ε- and γ- proteobacteria that this methane-seep species farms are closely related to hydrothermal-vent decapod epibionts. We hypothesize that this species waves its arm in reducing fluid to increase the productivity of its epibionts by removing boundary layers which may otherwise limit carbon fixation. The discovery of this new species, only the second within a family described in 2005, stresses how much remains undiscovered on our continental margins.     

Optimal foraging versus shared doom effects: interactive influence of mussel size and epibiosis on predator preference

In the western Baltic Sea, the highly competitive blue mussel Mytilus edulis tends to monopolize shallow water hard substrata. In many habitats, mussel dominance is mainly controlled by the generalist predator Carcinus maenas. These predator-prey interactions seem to be affected by mussel size (relative to crab size) and mussel epibionts.There is a clear relationship between prey size and predator size as suggested by the optimal foraging theory: Each crab size class preferentially preys on a certain mussel size class. Preferred prey size increases with crab size.Epibionts on Mytilus, however, influence this simple pattern of feeding preferences by crabs. When offered similarly sized mussels, crabs prefer Balanus-fouled mussels over clean mussels. There is, however, a hierarchy of factors: the influence of attractive epibiotic barnacles is weaker than the factor ‘mussel size’. Testing small mussels against large mussels, presence or absence of epibiotic barnacles does not significantly alter preferences caused by mussel size. Balanus enhanced crab predation on mussels in two ways: Additional food gain and, probably more important, improvement in handling of the prey. The latter effect is illustrated by the fact that artificial barnacle mimics increased crab predation on mussels to the same extent as do live barnacles.We conclude that crab predation preferences follows the optimal foraging model when prey belong to different size classes, whereas within size classes crab preferences is controlled by epibionts.     

Fouling of gastropods: a role for parasites?

A sample of mud snails Hydrobia ulvae (Prosobranchia) from an intertidal population revealed that the shells of trematode-infected specimens were especially likely to be fouled with epibionts. Experimentally trematode-infected Biomphalaria glabrata (Pulmonata) appeared to be especially prone to develop epigrowth in comparison with uninfected conspecifics as well. These findings suggest an interaction between trematode infections and epibiosis in aquatic gastropods. The two most likely explanations for this are (1) that trematode infections weakens the snails' natural defences against epibionts, or (2) that the defences against epibionts also are effective against invading trematodes, causing snail specimens with a particularly good fouling defence to be less likely to become infected.     

Seasonal dynamic of phototrophic epibionts on crustacean zooplankton in a eutrophic reservoir with cyanobacterial bloom

Seasonality of burden and prevalence of phototrophic (microalgal) epibionts Characidiopsis ellipsoidea, Colacium vesiculosum and Colacium sp. on dominating crustacean zooplankton (Daphnia longispina, Cyclops vicinus and Mesocyclops leuckarti) were studied in a small reservoir Bugach with cyanobacterial bloom. The correlations between the seasonal dynamics of prevalence and the dynamics of others biotic and abiotic factors were calculated. The conclusions were as follows. The substrate species, that determined the development of the epibionts on the three studied crustacean zooplankton, was Daphnia longispina (Cladocera). Despite intensive epibiotic infestation of crustacean zooplankton, epibionts did not appear to have caused non-consumptive mortality of the crustacean zooplankton. But they could have contributed to the Daphnia summer decline by increasing mortality due to its consumption by planktivorous fishes. The phototropic epibionts may successfully coexist with cyanobacterial bloom. The possible role of the epibionts in changing nutrient fluxes in pelagic food web is discussed.     

Associational resistance and shared doom: effects of epibiosis on herbivory

The potential for spatial associations between palatable and unpalatable plant species to reduce herbivore pressure on the palatable species has been described as associational resistance, associational refuge or associational defense for numerous terrestrial and marine communities. One of the closest associations between species-epibiosis-has not been thoroughly investigated in this regard. In this study we evaluated how different associations between host seaweeds and epibiotic plants and animals influenced the movement of an omnivorous sea urchin (Arbacia punctulata) to the host and subsequent feeding on the host. A. punctulata showed clear preferences when given pairwise choices between 12 prey species (3 animals, 9 algae). These preferences were consistent and allowed us to rank the six epibiont species and six host species linearly from least to most preferred by A. punculata. Most host-epibiont associations dramatically changed urchin preference, increasing or decreasing urchin grazing on fouled hosts as compared to clean conspecifics. Herbivory on the host increased when the epibiont was more preferred, and decreased when it was less preferred than the unfouled host alga. Taking the host species as a point of reference, we classified epibiosis-caused decrease in herbivory as associational resistance, while epibiont-caused increases in herbivory were defined as shared doom. These epibiont-host-herbivore interactions could select for hosts that facilitate the growth of certain low preference epibionts on their surfaces in situations where the resulting decreases in herbivory would offset the various negative effects of being fouled. In contrast, in situations where herbivores are common, the negative effects of being fouled by palatable epibionts may be much greater than is generally assumed. In our assays, unpalatable hosts fouled by palatable epibionts became much more attractive to urchins and rose several ranks on the urchins' preference hierarchy.