Helminth communities of the lesser sandeel Ammodytes tobianus L. off the west coast of Ireland

The helminth parasites present in 412 lesser sandeels (Ammodytes tobianus) taken from June 1996 to May 1997 from the Aran Islands on the west coast of Ireland were examined. Ten helminth parasite species were recorded, and more than 92% of the sandeels were infected with at least 1 helminth species. Seven of the species were digeneans, including Brachyphallus crenatus, Hemiurus communis, Derogenes varicus, Lecithaster gibbosus, Opechona bacillaris, Cryptocotyle lingua, and Galactosomum lacteum; 2 nematodes, including Hysterothylacium sp. and Contracaecum sp.; and 1 cestode, Scolex pleuronectis. Three of the 7 digenean species were either larvae or immature. Only 2 species, the digeneans G. lacteum and H. communis, had prevalences greater than 50%. The dominant species was G. lacteum, accounting for 67% of all parasites present. The relationship between spawned groups, host length, and season versus the abundance, prevalence, species richness, and the total number of parasites in the infracommunities was investigated. No difference was found between the parasite communities of the 2 spawning races of the host population. Mean abundance and prevalence of the different parasite species showed seasonal variation. Numbers of parasite species and numbers of parasites increased with fish length. The role of A. tobianus as an intermediate host for helminths was assessed; it was determined that most were infectious to birds or mammals, with the majority of the parasite species being autogenic (infectious to fish). The mean number of parasites per fish was nearly a quarter of the value recorded for A. tobianus in the North Sea, where a much higher intensity of infection was recorded.     

Infections by helminth parasites in "puyenes", Galaxias maculatus (Galaxiidae, Salmoniformes), from Southern Argentina with special reference to Tylodelphys barilochensis (Digenea, Platyhelminthes).

The occurrence of Tylodelphys barilochensis, Acanthostomoides apophalliformis, Contracaecum sp. and Camallanus corderoi infecting Galaxias maculatus ("puyenes") was quantified for the first time in Lake Nahuel Huapi, southern Argentina. T. barilochensis was recorded in this lake for the first time. The role of G. maculatus population in transmission of parasites to the salmonids is more important for Contracaecum sp. (prevalence 14-34%) and A. apophalliformis (prevalence 30-54%) than for C. corderoi (prevalence 6-8%). The absence of Diphyllobothrium spp. in samples shows that the G. maculatus population does not play any role in the life cycles of these important zoonotic parasites. The sex of the host had no effect on T. barilochensis abundance. Statistical differences in T. barilochensis abundance between "puyenes" of the same size class between sampling stations and positive correlation between prevalence of infected snails and T. barilochensis abundance in fish suggest that different stocks have been sampled. Factors influencing T. barilochensis abundance are discussed.     

Parasitism in fishes and human riverside communities of the Huillinco and Natri lakes (Great Island of Chiloé), Chile

In April and December 1989, 35 fish from Lake Huillinco (42 degrees 48'S, 74 degrees 02'W) and 36 fish from Lake Natri (42 degrees 48'S, 73 degrees 50'W), in the Great Island of Chiloé (Chile) were examined. Coprological samples from 159 persons, 17 dogs, 19 pigs and 4 cats from around both lakes were examined for Diphyllobothrium spp. infection. In the Lake Huillinco the following helminths of fishes were determined: Contracaecum sp. and Hysterothylacium sp. in Salmo trutta, Cauque mauleanum and Eleginops maclovinus; Dichelyne (Cucullanellus) dichelyneformis in S. trutta and E. maclovinus and Scolex pleuronectis in S. trutta. One specimen of Mugil cephalus did not show helminth parasites. Prevalence of infection were greater for Contracaecum sp. in S. trutta (75.0%) and C. mauleanum (76.0%); and Hysterothylacium sp. in E. maclovinus (75.0%). Mean intensity was higher for D. (C.) dichelyneformis in E. maclovinus. Contracaecum sp. in S. trutta, Oncorhynchus mykiss, Oncorhynchus kisutch and Galaxias maculatus; Acanthocephalus sp. in S. trutta and G. maculatus, S. pleuronectis in O. mykiss and Cystidicoloides sp. in G. maculatus were determined at Lake Natri. Prevalence and intensity of infection were higher for Contracaecum sp. in S. trutta and O. kisutch. Infection by Diphyllobothrium sp. was determined in one domestic cat. Prevalence of infection by intestinal protozoan and helminths in human population only showed significative differences for Ascaris lumbricoides and Trichuris trichiura that were higher in the Lake Huillinco. Importance of natural infection by helminth parasites for fish in cultured condition and possible mechanisms of infections in relation to the diet of fishes are discussed.     

Helminth communities of four commercially important fish species from Chetumal Bay, Mexico

The relative importance of ecology and evolution as factors determining species richness and composition of the helminth communities of fish is a matter of current debate. Theoretical studies use host-parasite lists, but these do not include studies on a temporal or spatial scale. Local environmental conditions and host biological characteristics are shown to influence helminth species richness and composition in four fish species (Eugerres plumieri, Hexanematichthys assimilis, Oligoplites saurus, and Scomberomorus maculatus) in Chetumal Bay, Mexico. With the exception of H. assimilis, the helminth communities had not been previously studied and possible associations between environmental and host biological characteristics as factors determining helminth species richness and composition using redundancy analysis (RDA) are described. Thirty-four helminth species are identified, with the highest number of species (19 total (mean = 6.3 +/- 2.1)) and the lowest (9 (4.0 +/- 1.0)) occurring in H. assimilis and S. maculatus, respectively. The larval nematodes Contracaecum sp. and Pseudoterranova sp. were not only the helminth species shared by all four host species but also were the most prevalent and abundant. Statistical associations between helminth community parameters and local ecological variables such as host habitat use, feeding habits, mobility, and time of residence in coastal lagoons are identified. Phylogeny is important because it clearly separates all four host species by their specialist parasites, although specific habitat and feeding habits also significantly influence the differentiation between the four fish species.     

Helminth communities in Audouin's gulls, Larus audouinii from Chafarinas Islands (western Mediterranean)

A survey of intestinal helminth communities of Audouin's gulls Larus audouinii, from their breeding colonies in Chafarinas Islands, western Mediterranean, Spain was conducted to determine the abundance and species diversity of intestinal parasites of these birds. The sample of 58 gulls harbored intestinal helminth infracommunities composed of species that are gull generalists, including the digeneans Cardiocephalus longicollis, Knipowitschiatrema nicolai, Condylocotyla pilodora, and Aporchis massiliensis, and the cestode Tetrabothrius cylindraceus. Two nematodes are waterfowl generalists (Cosmocephalus obvelatus and Paracuaria adunca), whereas the digenean Acanthotrema armata is an Audouin's gull specialist. The relative high values of species richness and diversity of the helminth infracommunities are comparable to those of other gulls (Larus philadelphia, Larus canus), probably reflecting the specialized, nonselective fish diet of L. audouinii.     

Seasonal occurrence of helminths in the anadromous fish Coilia nasus (Engraulidae): parasite indicators of fish migratory movements

To understand the seasonal migration of the anadromous Coilia nasus , we attempted to identify the parasites infecting C. nasus and determine their seasonal occurrence. From June 2007 to July 2008, a survey of 775 C. nasus individuals from the estuary of the Yangtze River and the coast of the East China Sea revealed more than 7,300 parasites associated with the gills and alimentary tracts of C. nasus . The following 6 helminth taxa were identified, i.e., the monogeneans Heteromazocraes lingmueni and Helciferus tenuis, the digenean Elytrophallus coiliae, the acanthocephalan Acanthosentis cheni , and larvae of the nematodes Anisakis simplex and Contracaecum sp., all of which are marine or brackish-water parasites. The absence of freshwater helminths suggested that the parasites acquired in freshwater may have been accidentally, and easily, lost by the time the fish had reached the estuary and coast. Contrary to seasonal occurrence of the parasites' life cycles, the lowest mean abundance and prevalence of H. lingmueni and A. cheni occurred in August, which suggested the immigration of C. nasus from freshwater to the Yangtze estuary, with lower parasite burdens. The highest mean abundance and prevalence of the nematodes A. simplex and Contracaecum sp. in May and June, and the lowest in August, indicated the arrival of the fish from the coast and the Yangtze River, to the estuary, respectively. These findings suggested that a majority of the fish prepared for spawning migration in the estuary in spring and early summer and returned to the estuary after spawning in the lower and middle reaches of the Yangtze River in late summer.     

Helminth parasites of Madeiran rockpool fishes,with a redescription of Schikhobalotrema longivesiculatum Orecchia & Paggi, 1975 (Digenea: Haplosplanchnidae), and some comments on their zoogeographical relationships

Seven species of Madeiran rockpool fishes were examined for their helminth parasites. Only two of these harboured helminth parasites. The most frequently encountered parasite was the digenean Schikhobalotrema longivesiculatum Orecchia & Paggi, 1975 from Parablennius parvicornis; this species is redescribed and discussed. The paucity of the parasite fauna of Madeiran rockpool fishes and the zoogeographical relationships of the digenean fauna of Madeiran marine fishes are commented upon.     

The relationship between fish assemblages and the helminth communities of a prey fish, in a group of small shallow lakes

Galaxias maculatus (small puyen) is an abundant native fish distributed in lakes and rivers of the Patagonia, and it is the frequent prey of other fishes, fish-eating birds, and mammals. Previous studies have shown that it is parasitized by 33 metazoan species and that the richness and composition of the parasite communities vary between lakes. The aim of the present work was to analyze the relationship between the composition of fish assemblages and the helminth component community structure of G. maculatus . Ten environmentally similar, small, shallow lakes, belonging to the Nahuel Huapi Lake basin, were chosen because of the differences in the native fish assemblages. Parasite community structure in G. maculatus varied according to the fish assemblage of each lake. The presence of the piscivorous fish Percichthys trucha regularly produced variations in the composition and richness at the component and infracommunity levels, as well as the percentage of autogenic parasite species in G. maculatus .     

Differences in proximate lipid composition,heavy metals,and mineral contents in bogue (Boops boops,Linnaueus, 1758) captured far away and directly at sea bass and sea bream cage farms

The objective of this study was to investigate the differences in proximate lipid composition, heavy metals, and mineral contents between bogue (Boops boops, Linnaeus, 1758) captured directly around and near a cage fish farm and those captured far away from it (“wild”). Wild fish were obtained from the fishery of the Aegean Sea and Northeastern Mediterranean. Fish were also caught at a distance of at least 100 meters away from the net cages using a commercial trammel set net. The fish captured near cages were taken at farms cultivating mainly sea bass and sea bream. Samples were taken in March 2016 to determine crude lipid content, moisture, and ash amounts. There were some differences between wild fish and near farm captured fish for both genders. Crude lipid contents of female wild fish and near farm captured fish were found to be higher than those in males (p < .05). The moisture contents of the males near the farms were higher than those in females. Results showed that the predominant macro minerals were potassium in females and males for both capture locations (near and far away from farms: range of 1070–1205 mg/kg). The near farm captured fish had a higher heavy metal content than those captured further away. This may be the result of environmental influences caused by the farm operations.     

A comparative study of the host-parasite relationship of Pomphorhynchus patagonicus (Acanthocephala) in two species of fish from Lake Rosario (Chubut, Argentina).

Some aspects of the host-parasite relationships of Pomphorhynchus patagonicus (Acanthocephala) in 2 fish species from Lake Rosario (Chubut, Argentina) were studied. The fish species Patagonina hatcheri (Atherinidae) is autochthonous, and Oncorhynchus mykiss (Salmonidae) is introduced. The host species appears to influence attachment, size, sexual maturity, and distribution of parasites along the digestive tract. In P. hatcheri, an effective major host, parasites are attached firmly to the wall of the gut, well developed, attain a greater size, and a large proportion of females is gravid with ripe eggs. In O. mykiss, an unsuccessful host, there were many unattached parasites that were small and not well developed; gravid females were rare and never had ripe eggs.     

Parasitic infections in freshwater ornamental fish in Sri Lanka

A total of 1520 ornamental fish of 13 species from 26 export farms in Sri Lanka were collected between October 1999 and March 2000 and examined for parasites. Fish species examined were guppy Poecilia reticulata, goldfish Carassius auratus, platy Xiphophorus maculatus, molly Poecilia sphenops, angel Pterophyllum scalare, swordtail Xiphophorus helleri, tetras Hyphessobrycon species, barbs Capeota and Puntius spp., gourami Colisa sp., carp Cyprinus carpio, fighters Betta spelendens and others (Brachydanio and Astronotus spp.). Nine species of monogenean trematodes (Dactylogyrus extensus, Dactylogyrus cf. extensus, D. vastator, Dactylogyrus cf. vastator Dactylogyrus spp., Gyrodactylus turnbulli, G. katherineri, Gyrodactylus cf. katherineri, Gyrodactylus spp.), 7 protozoan species (Trichodina nigra, Trichodina spp., Tetrahymena corlissi, T. pyriformis, Ichthyophthirius multifiliis, Ichthyobodo necator, Piscinoodinium spp.), 3 species of copepod arthropods (Lernaea cyprinacea, Ergasilus ceylonensis, Argulus foliaceus), 1 metacercarial stage of a digenean trematode (Centrocestus spp.) and 1 nematode (Capillaria spp.) were identified. Parasites were found in fish from 23 of the 26 farms with an overall prevalence of parasitism in 45.3% of fish. The variation in farm prevalence among different parasites was significant (p < 0.01). Fish infection rates with monogenean trematodes, protozoans, copepod crustaceans, digenean trematodes and nematodes were 28.3, 18.4, 4.8, 0.8 and 0.4%, respectively. In all, 50 out of 590 (50/590) guppies were infected with Tetrahymena, compared with 13/930 for all other species, which is a statistically significant result (p < 0.01). Similarly, 13/44 and 18/44 carp were infected with Argulus foliaceus and Lernaea cyprinacea, compared with 7/1476 and 15/1476, respectively, for all other species combined (p < 0.01). Capillaria spp. was found only in guppies (4/590) and angel fish (3/92) while Centrocestus spp. was found in goldfish (12/153) only.     

Parasitic infections in live freshwater tropical fishes imported to Korea

We examined 15 species of ornamental tropical fishes originating from Southeast Asia to determine the cause of losses among 8 fish farms in Korea. A total of 351 individuals belonging to 5 different families (1 species of Characidae, 6 of Cichlidae, 3 of Cyprinidae, 1 of Heleostomatidae, and 4 of Poecilidae) were collected for the purpose of detecting metazoan and protozoan parasites. Parasites were fixed and stained using routine methods, and identified. We found 3 ciliates, 2 monogeneans, 1 nematode, and 1 copepod from 7 host species. Of these, Ichthyophthirius multifiliis was the most common parasite in our study, and together with Trichodina sp., caused mass mortality of Sumatra barb Puntius tetrazona at 1 farm. We also found Camallanus cotti and Tetrahymena corlissi from guppies Poecilia reticulata, both for the first time in Korea. Farmers consider these 2 pathogens to be the most serious ones in Korea. Gussevia asota from oscar Astronotus ocellatus, and Gyrodactylus bullatarudis from platy Xiphophorus maculatus were also found in Korea for the first time. We believe that appropriate quarantine practices for tropical ornamental fishes should be introduced because the failure to require and implement quarantines has already resulted in the accidental introduction of exotic parasites to fish farms, and because these parasites can cause further economic losses if they become established in the wild.     

Interspecific associations among larval helminths in fish

Various processes can generate associations between the larvae of different helminth species in their fish intermediate or paratenic host. We investigated the pairwise associations among larval helminth species in eight different fish populations, using two different coefficients of associations, in order to determine in what situations they are strongest. All helminth species included use the fish studied as either their second intermediate host or their paratenic host, and are acquired by the fish when it ingests an infected first intermediate host. The intensity of infection correlated positively with fish length for most helminth species. Pairs of species which both exhibited positive correlations with fish length tended to be more strongly associated with one another, although this tendency was not pronounced. Similarity in life cycle had a more important influence on pairwise associations. Among the 62 pairwise associations that could be computed, pairs of helminth species that shared both first intermediate hosts and definitive hosts were the most strongly associated, followed by pairs that shared only one other host, and finally by pairs that did not share other hosts. The results suggest that assemblages of larval helminth parasites in fish are not random collections of locally available species, but rather structured packets of larval parasites that travel together along common transmission routes.     

Helminth infracommunities of a population of the Gran Canaria giant lizard Gallotia stehlini

A survey of gastro-intestinal helminth communities of Gallotia stehlini (Sauria: Lacertidae) from Gran Canaria island (Canary Archipelago, Spain), was conducted to determine the prevalence, abundance and species diversity of intestinal parasites in these lizards. Pharyngodonid nematodes were the most common intestinal helminths, three species being Gallotia specialists. Helminth infracommunities of G. stehlini were rich and appear to be closer to the interactive end of the continuum isolationist-interactive helminth communities, according to the high values of helminth diversity. It is the first case of a saurian reptile showing this kind of diverse helminth infracommunity, produced by a large size, a wide-ranging plant diet and exposure to helminths with direct life-cycles.     

A comparison of the parasite fauna of young whiting, Odontogadus merlangus (L.) (Gadidae) from an inshore and an offshore location off the Isle of Man

The occurrence of 12 helminth and 4 crustacean parasites on young whiting 0–2 years old from an inshore (Port Erin Bay) and an offshore (off Bradda Head) area of the Isle of Man were compared. No parasites were found on whiting 4.5–15 mm long and the intestinal digenean Lecithaster gibbosus Rudolphi together with the larvae of the copepod Caligus rapax M. Edwards were the first parasites to appear in whiting 15–42 mm long. This appears to be the only time during the life history of the whiting that C. rapax is of importance as a parasite. In whiting 6 months-2 years old from off Bradda Head such helminths as the acanthocephalan Echinorhynchus gadi Muller and the digeneans Podocotyle atomon Muller and Cryptocotyle lingua Creplin (metacercariae) were found in significantly fewer fish than in an equivalent group from Port Erin Bay. The differences are correlated with the availability of intermediate hosts and the different food spectra of the two groups of fish and are used to support the theory that inshore and offshore whiting of these age groups form separate populations and that the offshore fish may be more important than the inshore fish in replenishing stocks of older whiting.     

Correlates of helminth community in the red-legged partridge (Alectoris rufa L.) in Spain

Between 1992 and 1996, 587 wild red-legged partridges (Alectoris rufa) from 16 Spanish provinces were examined to study the variations of helminth communities in this game species across a broad geographical area. The survey revealed 13 species of helminth parasites. Dicrocoelium sp.. Rhabdometra nigropunctata, and Cheilospirura gruweli were the most common species, whereas Raillietina bolivari, Choanotaenia infundibulum, Tetrameres sp., and Capillaria anatis were the most rare. Subulura suctoria, Heterakis gallinarum, Heterakis tenuicaudata, Capillaria contorta, Trichostrongylus tenuis, and Raillietina tetragona occurred with intermediate frequencies. The abundance of C. gruweli, S. suctoria, H. tenuicaudata, T. tenuis, and R. tetragona was inversely correlated to latitude and directly correlated to yearly mean temperature, whereas the abundance of Dicrocoelium sp. was directly correlated to latitude and inversely correlated to yearly mean temperature. The abundance of R. tetragona was inversely correlated to latitude and yearly mean humidity. The number of helminths per partridge and the number of helminth species per partridge were lower in young birds than in adults. Partridge body condition was inversely correlated to abundance of C. contorta. Richer infracommunities were linked to richer component communities. At the infracommunity level, total number of helminths per partridge and number of helminth species per partridge were inversely correlated to latitude and directly correlated to yearly mean temperature. At the component community level, both species richness and diversity (Simpson's index) were inversely correlated to latitude and directly correlated to mean temperature. Across the broad geographical range of the study area, the helminth parasite communities of red-legged partridges had marked geographical variation in their structure. Our results suggest that this variation is determined by the distribution of both intermediate and definitive hosts. We discuss the implications of this variation for the hypothesis that supplementary releases of captive-bred partridges for sport hunting can affect the helminth fauna of wild red-legged partridges.     

Parasite fauna and food contents of Notothenia c.f. angustata Hutton, 1875 (Pisces: Nototheniidae) from two intertidal localities of the Arauco Gulf,Chile

We studied the parasite fauna and food contents of 38 juvenile of Notothenia c.f. angustata specimens captured in the intertidal of Island Santa María and Maule, in the Arauco Gulf, Chile. Trophic habits of Notothenia c.f. angustata were not different between localities, which was mainly algae. A total 11 parasitic taxa among were found with the digenean Lecitasther macrocotyle, cestode larvae Tetraphyllidea and Diphyllidea and nematode Ascarophis sp. being the dominant taxa. The abundance of parasites was similar in the two localities, although the infracommunity richness was higher in fish from Maule. The most abundant parasite was L. macrocotyle in hosts from Isla Santa María, while those from Maule they were the Diphyllidea larvae and nematodes Ascarophis sp. The body length of the hosts was not a good predictor of the variations in abundance and richness at infracommunities, probably because of the early ontogenetic stage of fishes.     

Spatial variation in population density across the geographical range in helminth parasites of yellow perch Perca flavescens

The abundance of a species is not constant across its geographical range; it has often been assumed to decrease from the centre of a species’ range toward its margins. The central assumption of this “favourable centre” model is tested for the first time with parasites, using different species of helminth parasites exploiting fish as definitive hosts. Data on prevalence (percentage of hosts that are infected) and abundance (mean no. parasites per host) were compiled for 8 helminth species occurring in 23 populations of yellow perch Perca flavescens, from continental North America. For each parasite species, correlations were computed between latitude and both local prevalence and abundance values. In addition, the relationships between the relative prevalence or abundance in one locality and the distance between that locality and the one where the maximum value was reported, were assessed separately for each species to determine whether abundance tends to decrease away from the presumed centre of the range, where it peaks. For both the cestode Proteocephalus pearsei and the acanthocephalan Leptorhynchoides thecatus, there was a positive relationship between prevalence or abundance and the latitude of the sampled population. There was also a significant negative relationship between relative prevalence and the distance from the locality showing the maximum value in P. pearsei, but no such pattern was observed for the other 7 parasite species. Since this single significant decrease in prevalence with increasing distance from the peak value may be confounded by a latitudinal gradient, it appears that the distribution of abundance in parasites of perch does not follow the favourable centre model. This means that the environmental variables affecting the density of parasites (host availability, abiotic conditions) do not show pronounced spatial autocorrelation, with nearby sites not necessarily providing more similar conditions for the growth of parasite populations than distant sites.     

Effects of water quality and trophic status on helminth infections in the cyprinid fish, Schizothorax niger Heckel, 1838 from three lakes in the Kashmir Himalayas

Water quality greatly influences the population density of aquatic biota, including parasites. In order to evaluate the relationship between fish parasites and water quality in Kashmir Himalayas, we assessed helminth parasite densities in Schizothorax niger Heckel, 1838 (an endemic cyprinid fish of Kashmir) from three lakes, namely Anchar, Manasbal and Dal, which reflected the varied stages of eutrophication. The overall prevalence of helminth infections was higher in the hypertrophic Anchar Lake (prevalence = 18.6%) compared to Manasbal Lake, which was the least eutrophied (prevalence = 6.4%). Furthermore, mean prevalence of monoxenous and heteroxenous parasites was higher in lakes containing higher levels of water degradation (Anchar and Dal). The mean number of helminth species per fish host was the highest in the hypertrophic lake (1.3 ± 0.3) in comparison to the least eutrophic lake (0.2 ± 1.5). Variability of calculated infection indices (prevalence, mean intensity and mean abundance) revealed that helminth parasite composition in the fish was affected by the lakes' environmental stress (degraded water quality). Therefore, data on the density of helminth parasites in fish can provide supplementary information on the pollution status of a water body.     

Effect of the digenean parasites of fish on the fauna of Mediterranean lagoons

Attention is drawn to the effects of parasites on their hosts, taking as a model the digenean parasites of teleosts (hereafter: fish) from lagoons along the French Mediterranean coast. Because digeneans have a heteroxenic life cycle, their impact is not limited to the definitive host, which harbours the sexual adults, but is extended to the first host (mollusc) and to the second host ("invertebrate" or fish). Adult parasites, in order to ensure efficient sexual reproduction, never cause excessive damage to their definitive host, usually only exploiting the intestinal fluids; however, the host must intensify its search for prey, which results in a diminished fitness. Within the first host, 'larval' stages of digenean parasites invade the gonads, resulting in its castration, then exhaustion and eventually death. The diversion of energy from the second hosts towards the parasites forces them to intensify their search for food, resulting in decreased fitness and an increased risk of being eaten; in addition, manipulation of the host's behaviour by parasites drives this host into the food chain of the definitive host. In lagoons, many individuals of almost all species of fish and invertebrates act as first, second and/or definitive hosts for digeneans. Obviously, parasites have a severe impact on the population dynamics of key taxa, on the food web and therefore also on the functioning of the whole lagoon ecosystem. Yet this impact has been largely overlooked or underestimated in functioning models, by ecologists, who tend to prioritize more apparent trophic relationships.