Predator-induced behavioral and morphological plasticity in the tropical marine Gastropod Strombus gigas

Florida queen conch stocks once supported a significant fishery, but overfishing prompted the state of Florida to institute a harvest moratorium in 1985. Despite the closure of the fishery, the queen conch population has been slow to recover. One method used in the efforts to restore the Florida conch population has been to release hatchery-reared juvenile conch into the wild; however, suboptimal predator avoidance responses and lighter shell weights relative to their wild counterparts have been implicated in the high mortality rates of released hatchery juveniles. We conducted a series of experiments in which hatchery-reared juvenile conch were exposed to a predator, the spiny lobster (Panulirus argus), to determine whether they could develop behavioral and morphological characteristics that would improve survival. Experiments were conducted in tanks with a calcareous sand substrate to simulate a natural environment. Conditioned conch were exposed to caged lobsters while conch in the control tanks were exposed to empty cages. Conditioned conch moved significantly less and buried themselves more frequently than the naive control conch. Morphometric data indicated that the conditioned conch grew at a significantly slower rate than the naive conch, but the shell weights of the two groups were not significantly different. This implies that the conditioned conch had thicker or denser shells than the control group. As a result, the conditioned conch had significantly higher survival than naive conch in a subsequent predation experiment in which a lobster was allowed to roam free in each tank for 24 hours. In the future, the conditioning protocols documented in this study will be used to increase the survival of hatchery-reared conch in the wild.     

Attenuated reproduction of Strombus gigas by an Apicomplexa: Emeriidae-like parasite in the digestive gland

An intense and generalized sporozoan infection was detected in every population of the queen conch, Strombus gigas through the Caribbean. In this contribution we establish the relationship between occurrences of an Apicomplexa: Emeriidae-like organism and reproductive activity at San Andres archipelago, Colombia. Occurrence of the parasites was estimated counting the feeding stage Merozoites and cysts Sporozoites at 40× magnification. Nonmetric multidimensional scaling analysis (NMDS) was made to correlate the parasites stages abundance with frequency of the reproductive stages. Gametogenesis and spawning were always low coinciding with high numbers of Merozoites, a positive correlation was established between parasite abundance with reabsorption and undifferentiated stages, and negative correlation was observed between parasite abundance with maturity and spawning stages. The nonmetric multidimensional scaling (NMDS) shows that gametogenesis, maturity and spawning increase as the number of parasites decrease, factor that could be threatening reproduction of S. gigas through the Caribbean.     

Ingestion and digestion of seven species of microalgae by larvae of Strombus gigas (Mesogastropoda: Strombidae)

The potential nutritional value of seven microalgal diets as measured by their ingestibility and digestibility to queen conch Strombus gigas larvae was tested with 30 day old larvae reared at 28 degrees C and fed at 1000 cells x ml(-1). The algae were Tetraselmis suecica, Tetraselmis chuii Isochrysis aff. galbana, Dunaliella tertiolecta, Chlamydomonas coccoides, Chaetoceros sp. and Thalassiosira fluviatilis. Ingestion and digestion were measured by the four nutritional stages studied with epifluorescence microscopy with live larvae. Temporal and absolute indices showed that larvae fed Chaetoceros sp. and T. fluviatilis had lower ingestion and digestion levels. The other algae are recommend to feed S. gigas larvae.     

Isolation and characterization of eight polymorphic microsatellite markers from pink conch (Strombus gigas)

Many marine organisms have pelagic larvae, and these are often important agents of dispersal. The larval phase and the multiple paternity that occur in marine gastropods such as Strombus gigas are crucial for the success of this species throughout the Caribbean Sea. To analyse these factors, we developed eight microsatellite loci specific to S. gigas. On the same set of individuals, the microsatellite loci exhibited a greater level of polymorphism than previously studied allozyme markers and thus, will permit fine‐scale analysis and larval pool studies.     

Thermal Acclimation of the Symbiotic Alga Symbiodinium spp. Alleviates Photobleaching under Heat Stress

A moderate increase in seawater temperature causes coral bleaching, at least partially through photobleaching of the symbiotic algae Symbiodinium spp. Photobleaching of Symbiodinium spp. is primarily associated with the loss of light-harvesting proteins of photosystem II (PSII) and follows the inactivation of PSII under heat stress. Here, we examined the effect of increased growth temperature on the change in sensitivity of Symbiodinium spp. PSII inactivation and photobleaching under heat stress. When Symbiodinium spp. cells were grown at 25°C and 30°C, the thermal tolerance of PSII, measured by the thermal stability of the maximum quantum yield of PSII in darkness, was commonly enhanced in all six Symbiodinium spp. tested. In Symbiodinium sp. CCMP827, it took 6 h to acquire the maximum PSII thermal tolerance after transfer from 25°C to 30°C. The effect of increased growth temperature on the thermal tolerance of PSII was completely abolished by chloramphenicol, indicating that the acclimation mechanism of PSII is associated with the de novo synthesis of proteins. When CCMP827 cells were exposed to light at temperature ranging from 25°C to 35°C, the sensitivity of cells to both high temperature-induced photoinhibition and photobleaching was ameliorated by increased growth temperatures. These results demonstrate that thermal acclimation of Symbiodinium spp. helps to improve the thermal tolerance of PSII, resulting in reduced inactivation of PSII and algal photobleaching. These results suggest that whole-organism coral bleaching associated with algal photobleaching can be at least partially suppressed by the thermal acclimation of Symbiodinium spp. at higher growth temperatures.Reef-building corals harbor symbiotic dinoflagellate algae of the genus Symbiodinium. Corals generally show a brownish coloration due to algal photosynthetic pigments, such as peridinin and chlorophylls a and c₂ present in in situ Symbiodinium spp. However, under increased seawater temperatures, corals become pale through the loss of Symbiodinium spp. cells and/or the loss of photosynthetic pigments of in situ Symbiodinium spp. (Glynn, 1993, 1996; Hoeghguldberg, 1999; Fitt et al., 2001; Coles and Brown, 2003). This phenomenon is so-called coral bleaching. Since a healthy algae-coral symbiotic relationship is important for coral survival (Yellowlees et al., 2008), severe coral bleaching leads to the mortality of corals and even the destruction of entire coral reef ecosystems. The frequency and intensity of coral bleaching have been increasing since the early 1980s, and it is predicted to become more severe in the future due to ongoing global climate change and warming (Hughes et al., 2003). Coral reef ecosystems are in serious decline, with an estimated 30% already severely damaged, and it is predicted that globally as much as 60% of the world’s coral reef ecosystems may be lost by 2030 (Hughes et al., 2003).Coral bleaching caused by heat stress is at least partially attributed to the photobleaching of photosynthetic pigments in Symbiodinium spp. within corals (Kleppel et al., 1989; Porter et al., 1989; Fitt et al., 2001; Takahashi et al., 2004; Venn et al., 2006). The photobleaching commonly occurs in photosynthetic organisms under conditions where the absorbed light energy for photosynthesis is in excess of the capacity to use it, particularly under environmental stress conditions in high light (Niyogi, 1999). In cultured Symbiodinium spp. cells, heat stress-associated algal photobleaching is attributed to the loss of major light-harvesting proteins, such as the peridinin-chlorophyll a-binding proteins and the chlorophyll a-chlorophyll c₂-peridin protein complexes (Takahashi et al., 2008). A recent study has also demonstrated that the heat stress-associated loss of light-harvesting proteins in Symbiodinium spp. is attributed to suppression of the de novo synthesis of light-harvesting proteins but not acceleration of the photodamage and subsequent degradation of light-harvesting proteins (Takahashi et al., 2008). High-temperature sensitivity of Symbiodinium spp. cells to photobleaching differs among Symbiodinium spp., and this is at least partially attributed to the thermal sensitivity of the de novo synthesis of light-harvesting proteins (Takahashi et al., 2008).Heat stress-associated photobleaching in Symbiodinium spp. follows severe photoinhibition of PSII (Takahashi et al., 2008). The extent of photoinhibition is a result of the dynamic balance between the rate of photodamage to PSII and the rate of its repair. In plants and green algae, the PSII repair process is primarily composed of the degradation and the de novo synthesis of the D1 proteins in photodamaged PSII protein complexes (Aro et al., 1993; Takahashi and Murata, 2008; Takahashi and Badger, 2011). However, this differs in Symbiodinium spp., in that the photodamaged PSII can be repaired without the de novo synthesis of D1 proteins (Takahashi et al., 2009b). Furthermore, a part of photodamaged PSII is repaired without protein synthesis (Takahashi et al., 2009b), indicating that Symbiodinium spp. have a unique PSII repair mechanism. In Symbiodinium spp. found within corals and also in culture, heat stress accelerates photoinhibition at least partially through the suppression of PSII repair (Warner et al., 1999; Takahashi et al., 2004, 2009b). However, the sensitivity of PSII repair to heat stress differs among Symbiodinium spp. and is strongly related to the sensitivity of PSII to photoinhibition under heat stress (Takahashi et al., 2009b).The high-temperature sensitivity of corals to bleaching is changed by their growth temperature, and this is suggested to be due to changing in situ Symbiodinium spp. populations from heat-sensitive to heat-resistant ecotypes (Baker, 2001, 2003; Baker et al., 2004; Berkelmans and van Oppen, 2006; Jones et al., 2008; Jones and Berkelmans, 2010). However, thermal tolerance of the population might also be enhanced by thermal acclimation mechanism(s) associated with both the corals and Symbiodinium spp., although experimental data that directly support this hypothesis are lacking. In this study, we examine the effect of increased growth temperature (thermal acclimation treatment) on the extent of heat stress-associated algal photobleaching using cultured Symbiodinium spp. Our results demonstrate that Symbiodinium spp. commonly have thermal acclimation mechanisms that enhance the high-temperature tolerance of PSII and alleviate heat stress-associated photobleaching. Our results strongly suggest that thermal acclimation of Symbiodinium spp. plays a role in alleviating algal photobleaching-associated coral bleaching under heat stress.     

Structural analysis of the digestive gland of the queen conch Strombus gigas Linnaeus, 1758 and its intracellular parasites

This study describes the structure of the digestive gland ofStrombus gigas in individuals from Guadeloupe and discussesthe function of its cell types and their relationship with intracellularApicomplexa-like parasites. Three cellular types were foundin the epithelium of the blind-ending tubules of the digestivegland according to histological and transmission electron microscopy(TEM) observations; these were: digestive cells, pyramidal cryptcells and vacuolated cells. Columnar digestive cells were characterizedby large Alcian blue-positive granules, which have not beenpreviously described in digestive cells of other caenogastropods.Such granules contain large quantities of proteoglycans thatare exported to the stomach through the physiological destructionof the digestive cells, which undergo a holocrine secretion.Their cytoplasm appears vacuolar due to lipid extraction bysolvents used for tissue preparation. Vacuolated cells alsoappear to be lipid-storage cells. Small triangular-shaped cryptcells, on the other hand, appear to be metabolically activeas suggested by a strong positive in situ hybridization of eukaryoticribosomes, which was confirmed by their large content of ribosomesand rough endoplasmic reticulum compared to the other cell types.These observations suggest that crypt cells may be immaturecells that are involved in the replacement of eliminated digestivecells. However, their spherocrystal inclusions indicate thatthey may be excretory cells or calcium cells. Large brown inclusionswere frequently observed in vacuolated cells; these were identifiedas parasitic protozoans and were present in the digestive glandof all sampled specimens. These protozoans have previously beendescribed from a queen conch population in the San Andres Archipelago(Colombia). Several life cycle stages of the parasite were identifiedby scanning electron microscopy and TEM; trophozoites were characterizedby their conoid-like structure, sporocysts by their thick walls,and gamonts by their thin walls. These observations suggestthat this parasite completes its entire life cycle within thesame host and type of tissue. Although previous investigationsplace this parasite within the Apicomplexa group, further investigationsare necessary in order to confirm the identification of theparasite. (Received 13 May 2008; accepted 3 October 2008)     

Genetic diversity in two populations of the snail Strombus gigas (Gastropoda: Strombidae) from Yucatan, Mexico, using microsatellite

The pink conch Strombus gigas is an important fisheries resource in the Caribbean region, including the Yucatán Peninsula. We analyzed the genetic diversity and genetic structure of two populations (Alacranes Reef and Chinchorro Bank) with the use of five microsatellite molecular markers. The results indicate that the two populations are in the same rank of genetic diversity (He), from 0.613 to 0.692. Significant deviation from H-WE was observed in the both populations due to deficit to heterozygotes, this was attributed to inbreeding as a consequence of over-fishing; nevertheless, other possible causes considered are mixing of individuals from two or more populations, and the existence of null alleles. Levels of genetic differentiation indicated the existence of a single homogenous population in the Yucatan Peninsula (F(ST) de 0.003, p = 0.49), which fits with highest levels of gene flow is significant (2.3 individuals) between both populations. Results from this study support the hypothesis that S. gigas is part of a single panmictic population in the Yucatan Peninsula; therefore, this fishery resource should be regulated the same way for both areas.     

Effects of Low Salinity on Adult Behavior and Larval Performance in the Intertidal Gastropod Crepipatella peruviana (Calyptraeidae)

Shallow-water coastal areas suffer frequent reductions in salinity due to heavy rains, potentially stressing the organisms found there, particularly the early stages of development (including pelagic larvae). Individual adults and newly hatched larvae of the gastropod Crepipatella peruviana were exposed to different levels of salinity stress (32(control), 25, 20 or 15), to quantify the immediate effects of exposure to low salinities on adult and larval behavior and on the physiological performance of the larvae. For adults we recorded the threshold salinity that initiates brood chamber isolation. For larvae, we measured the impact of reduced salinity on velar surface area, velum activity, swimming velocity, clearance rate (CR), oxygen consumption (OCR), and mortality (LC50); we also documented the impact of salinity discontinuities on the vertical distribution of veliger larvae in the water column. The results indicate that adults will completely isolate themselves from the external environment by clamping firmly against the substrate at salinities ≤24. Moreover, the newly hatched larvae showed increased mortality at lower salinities, while survivors showed decreased velum activity, decreased exposed velum surface area, and decreased mean swimming velocity. The clearance rates and oxygen consumption rates of stressed larvae were significantly lower than those of control individuals. Finally, salinity discontinuities affected the vertical distribution of larvae in the water column. Although adults can protect their embryos from low salinity stress until hatching, salinities <24 clearly affect survival, physiology and behavior in early larval life, which will substantially affect the fitness of the species under declining ambient salinities.     

Acquisition of symbiotic dinoflagellates (Symbiodinium) by juveniles of the coral Acropora longicyathus

Scleractinian corals may acquire Symbiodinium from their parents (vertically) or from the environment (horizontally). In the present study, adult colonies of the coral Acropora longicyathus from One Tree Island (OTI) on the southern Great Barrier Reef (Australia) acquired two distinct varieties of symbiotic dinoflagellates (Symbiodinium) from the environment. Adult colonies had either Symbiodinium from clade C (86.7%) or clade A (5.3%), or a mixture of both clades A and C (8.0% of all colonies). In contrast, all 10-day-old juveniles were associated with Symbiodinium from clade A, while 83-day-old colonies contained clades A, C and D even though they were growing at the same location. Symbiodinium from clade A were dominant in both 10- and 83-day-old juveniles (99 and 97% of all recruits, respectively), while clade D was also found in 31% of 83-day-old juveniles. Experimental manipulation also revealed that parental association (with clade A or C), or the location within the OTI reef, did not influence which clade of symbiont was acquired by juvenile corals. The differences between the genetic identity of populations of Symbiodinium resident in juveniles and adult A. longicyathus suggest that ontogenetic changes in the symbiosis may occur during the development of scleractinian corals. Whether or not these changes are due to host selective processes or differences in the physical environment associated with juvenile versus adult colonies remains to be determined.     

Molecular Phylogenetic Study of Larval Trematode from the Gastropod Tritia mutabilis (Gastropoda: Nassariidae) in the Mediterranean Sea off Naples

Russian Journal of Marine Biology - Larval trematode that infecting the gastropod Tritia mutabilis (Nassariisae) in natural beds of the Neapolitan Gulf (off Campania, Pozzuoli) was characterized...     

Deep-Sequencing Method for Quantifying Background Abundances of Symbiodinium Types: Exploring the Rare Symbiodinium Biosphere in Reef-Building Corals

The capacity of reef-building corals to associate with environmentally-appropriate types of endosymbionts from the dinoflagellate genus Symbiodinium contributes significantly to their success at local scales. Additionally, some corals are able to acclimatize to environmental perturbations by shuffling the relative proportions of different Symbiodinium types hosted. Understanding the dynamics of these symbioses requires a sensitive and quantitative method of Symbiodinium genotyping. Electrophoresis methods, still widely utilized for this purpose, are predominantly qualitative and cannot guarantee detection of a background type below 10% of the total Symbiodinium population. Here, the relative abundances of four Symbiodinium types (A13, C1, C3, and D1) in mixed samples of known composition were quantified using deep sequencing of the internal transcribed spacer of the ribosomal RNA gene (ITS-2) by means of Next Generation Sequencing (NGS) using Roche 454. In samples dominated by each of the four Symbiodinium types tested, background levels of the other three types were detected when present at 5%, 1%, and 0.1% levels, and their relative abundances were quantified with high (A13, C1, D1) to variable (C3) accuracy. The potential of this deep sequencing method for resolving fine-scale genetic diversity within a symbiont type was further demonstrated in a natural symbiosis using ITS-1, and uncovered reef-specific differences in the composition of Symbiodinium microadriaticum in two species of acroporid corals (Acropora digitifera and A. hyacinthus) from Palau. The ability of deep sequencing of the ITS locus (1 and 2) to detect and quantify low-abundant Symbiodinium types, as well as finer-scale diversity below the type level, will enable more robust quantification of local genetic diversity in Symbiodinium populations. This method will help to elucidate the role that background types have in maximizing coral fitness across diverse environments and in response to environmental change.     

Competition and Coexistence In a Multi-partner Mutualism: Interactions Between two Fungal Symbionts of the Mountain Pine Beetle In Beetle-attacked Trees

Despite overlap in niches, two fungal symbionts of the mountain pine beetle (Dendroctonus ponderosae), Grosmannia clavigera and Ophiostoma montium, appear to coexist with one another and their bark beetle host in the phloem of trees. We sampled the percent of phloem colonized by fungi four times over 1 year to investigate the nature of the interaction between these two fungi and to determine how changing conditions in the tree (e.g., moisture) affect the interaction. Both fungi colonized phloem at similar rates; however, G. clavigera colonized a disproportionately larger amount of phloem than O. montium considering their relative prevalence in the beetle population. High phloem moisture appeared to inhibit fungal growth shortly after beetle attack; however, by 1 year, low phloem moisture likely inhibited fungal growth and survival. There was no inverse relationship between the percent of phloem colonized by G. clavigera only and O. montium only, which would indicate competition between the species. However, the percent of phloem colonized by G. clavigera and O. montium together decreased after 1 year, while the percent of phloem from which no fungi were isolated increased. A reduction in living fungi in the phloem at this time may have significant impacts on both beetles and fungi. These results indicate that exploitation competition occurred after a year when the two fungi colonized the phloem together, but we found no evidence of strong interference competition. Each species also maintained an exclusive area, which may promote coexistence of species with similar resource use.     

Light-evoked depolarizations in the retina of Strombus: role of sodium and potassium ions

Light-evoked depolarizations (LED's) in retinal cells of Strombus luhuanus can exhibit an early phase of depolarization (DE), a brief repolarizing phase (RE), and a later depolarizing phase (DL). Lowering external Na+ by substitution with choline, tetramethylammonium or sucrose, reduced the amplitude of the entire LED, but DL was reduced more than DE. Replacement of Na+ with Li+ reduced DE more than DL. Lowering pH reduced DL more than DE, while raising it increased DL but not DE. K+ channel blocking agents, tetraethylammonium and 4-aminopyridine, increased RE. During the LED, cell membrane conductance increased in two phases, corresponding to DE and DL. The results suggest LED generation by two separable conductance increases to Na+, corresponding to DE and DL, and another to K+ during RE.     

In Vitro Interactions Between Yeasts and Bacteria and the Fungal Symbionts of the Mountain Pine Beetle (Dendroctonus ponderosae)

Multi-trophic interactions between prokaryotes, unicellular eukaryotes, and ecologically intertwined metazoans are presumably common in nature, yet rarely described. The mountain pine beetle, Dendroctonus ponderosae, is associated with two filamentous fungi, Grosmannia clavigera and Ophiostoma montium. Other microbes, including yeasts and bacteria, are also present in the phloem, but it is not known whether they interact with the symbiotic fungi or the host beetle. To test whether such interactions occur, we performed a suite of in vitro assays. Overall, relative yield of O. montium grown with microbes isolated from larval galleries was significantly greater than when the fungus was grown alone. Conversely, the yield of G. clavigera grown with these same microbes was less than or equal to when it was grown alone, suggesting that O. montium, and at least some microbes in larval galleries, have a mutualistic or commensal relationship, while G. clavigera and those same microbes have an antagonistic relationship. A bacterium isolated from phloem not colonized by beetles was found to inhibit growth of both G. clavigera and O. montium and appears to be an antagonist to both fungi. Our results suggest that bacteria and yeasts likely influence the distribution of mycangial fungi in the host tree, which, in turn, may affect the fitness of D. ponderosae.     

Phenotypic,Molecular and Symbiotic Characterization of the Rhizobial Symbionts of Desmanthus paspalaceus (Lindm.) Burkart That Grow in the Province of Santa Fe,Argentina

Desmanthus paspalaceus (Lindm.) Burkart belongs to the D. virgatus complex, subfamily Mimosoidae. The known potential as livestock fodder of several of these legumes prompted us to undertake a phenotypic, molecular, and symbiotic characterization of the D. paspalaceus symbionts in the Santa Fe province, Argentina. The rhizobia collected—containing isolates with different abiotic-stress tolerances—showed a remarkable genetic diversity by PCR fingerprinting, with 11 different amplification profiles present among 20 isolates. In selected isolates 16S-rDNA sequencing detected mesorhizobia (60%) and rhizobia (40%) within the collection, in contrast to the genus of the original inoculant strain CB3126—previously isolated from Leucaena leucocephala—that we typified here through its 16S rDNA as Sinorhizobium terangae. The results revealed the establishment by diverse bacterial genera -rhizobia, sinorhizobia, and mesorhizobia- of full N₂-fixing symbiotic associations with D. paspalaceus. This diversity was paralleled by the presence of at least two different nodC allelic variants. The identical nodC alleles of the Mesorhizobia sp. 10.L.4.2 and 10.L.5.3 notably failed to group within any of the currently described rhizo-/brady-/azorhizobial nodC clades. Interestingly, the nodC from S. terangae CB3126 clustered close to homologs from common bean nodulating rhizobia, but not with the nodC from S. terangae WSM1721 that nodulates Acacia. No previous data were available on nod-gene phylogeny for Desmanthus symbionts. A field assay indicated that inoculation of D. paspalaceus with the local Rhizobium sp. 10L.11.4 produced higher aerial-plant dry weights compared to S. teranga CB3126–inoculated plants. Neither the mesorhizobia 10.L.4.2 or 10.L.5.3 nor the rhizobium 10L.11.4 induced root nodules in L. leucocephala or P. vulgaris. The results show that some of the local isolates have remarkable tolerances to several abiotic stresses including acidity, salt, and temperature; while exhibiting prominent N₂ fixation; thus indicating suitability as candidates for inoculation of D. paspalaceus.     

Nutrients,Signals, and Photosynthate Release by Symbiotic Algae (The Impact of Taurine on the Dinoflagellate Alga Symbiodinium from the Sea Anemone Aiptasia pulchella)

Exogenous concentrations of 10 [mu]M to 1 mM of the nonprotein amino acid taurine stimulated photosynthate release from the dinoflagellate alga Symbiodinium, which had been freshly isolated from the sea anemone Aiptasia pulchella. Photosynthate release, as induced by taurine and animal extract, was metabolically equivalent at both concentrations in that they (a) stimulated photosynthate release to the same extent and (b) induced the selective release of photosynthetically derived organic acids. A complex mixture of amino acids at 75 mM also promoted photosynthate release, but the release rate was reduced by 34% after the omission of taurine (3 mM) from the mixture, suggesting that much of the effect of amino acids was largely attributable to taurine. Exogenous 14C-labeled taurine was taken up by the cells, and more than 95% of the internalized 14C was recovered as taurine, indicating that taurine-induced photosynthate release was not dependent on taurine metabolism. Both taurine uptake and taurine-induced photosynthate release by Symbiodinium exhibited saturation kinetics, but with significantly different Km values of 68 and 21 [mu]M, respectively. The difference in Km values is compatible with the hypothesis that Symbiodinium has a taurine signal transducer that is responsible for photosynthate release and is distinct from the taurine transporter.     

Adaptations of Host and Symbionts in the Intertidal Zone

SYNOPSIS. Different species of larval trematodes that utilizethe same intermediate host characteristically exhibit distinctivepatterns of response to environmental fluctuations. Not onlyare the responses distinctive for each species, but also theycannot be correlated with that of the host. The physiologicalresponses of the molluscan host to physical changes in the environment,however, are modified significantly by the presence of a larvaltrematode infection. The thermal metabolic acclimation patternsof infected Nassarius obsoleta are quite distinct from thoseof non-infected N. obsoleta. Thex activity patterns during thermalacclimation of cytochrome c oxidase from digestive glands ofsnails infected with different species of larval trematodesindicate that each species of larval trematodes differentiallyinfluences the hosttissue, so that the cytochrome oxidase systemdoes not respond to temperature in the same way as does uninfectedhost tissue.