Ecological Archives E095-165-A3

Irit Altman, James E. Byers. 2014. Large-scale spatial variation in parasite communities influenced by anthropogenic factors. Ecology 95:1876–1887. http://dx.doi.org/10.1890/13-0509.1

Appendix C. Analysis and discussion of relationships between prevalence of Ilyanassa obsoleta trematodes that mature in fish hosts and abundance of definitive fish hosts measured from salt marsh sites.

While the literature indicates that individual species of I. obsoleta trematodes use only a subset of fishes identified from fyke net samples, full knowledge of host pathways for many trematodes is limited and the number of documented host species likely greatly underestimates the number that serve in this role in nature. We identified a total of five fish species from fyke net sampling that are known definitive hosts of I. obsoleta trematodes or likely hosts because they are closely related taxonomically and prey on organisms that are second intermediate hosts (Table C1). We examined relationships between prevalence of individual trematode species and abundance of their known and likely definitive fish hosts (Fig. C1 black squares and solid regression line). We also examined the relationship between prevalence of trematode species and total abundance of definitive fish hosts for any species of I. obsoleta trematode (Fig. C1 open squares and hashed regression line). All analyses use Anscombe transformed prevalence (see methods in main text) as well as ln(abundance) of fish. For brevity, however, we do not refer to transformations when describing the results below.

Results indicate a marginally significant positive relationship between prevalence of Stephanostomum spp. trematodes and the abundance of two known definitive fish hosts associated with this trematode group (R² = 0.22, p = 0.08; Fig. C1a). The relationship between Stephanostomum spp. prevalence and abundance of definitive fish hosts of any I. obsoleta trematode was similar, although not significant (R² = 0.18, p = 0.11; Fig. C1a). For Z. rubellus, no significant relationship was found between prevalence and the abundance of its known definitive fish host (R² = 0.00, p = 0.96; Fig. C1b). The relationship, between Z. rubellus and abundance of definitive fish hosts of any I. obsoleta trematode, however, was strong and significant (R² = 0.48, p = 0.004; Fig. C1b). A non-significant relationship was found between L. setiferoides prevalence and the abundance of known and likely definitive fish hosts of this trematode (R² = 0.01, p = 0.71; Fig. C1c). In comparison, the relationship between L. setiferoides prevalence and abundance of definitive fish hosts of any I. obsoleta was stronger, albeit still non-significant (R² = 0.14, p = 0.17; Fig. C1c). These results suggest that the prevalence of individual trematode species was often better or, in one case, similarly well predicted by the abundance of definitive fish hosts associated with any I. obsoleta trematode compared to the abundance of known and likely definitive fish hosts of the trematode species in question.

Table C1. Fish species identified from fyke net sampling across 15 salt marsh sites that are documented definitive hosts of I. obsoleta trematodes or likely serve in this role because they are closely related taxonomically to known hosts and prey on relevant second intermediate hosts taxas.

Fish Species

Family

Common name

Stephanostomum spp.

Lepocreadium setiferoides

Zoogonus rubellus

Aguilla rostrata

Anguillidae

American eel

   

Documented (Stunkard 1938, McDermott 1951, Schell 1970)

Morone axatilis

Moronidae

striped bass

Documented (Martin 1939, Linton 1940, McDermott 1951, Schell 1970)

   

Morone americana

Moronidae

white perch

Documented (Linton 1940, McDermott 1951)

   

Pseudopleuronectes americanus

Pleuronectidae

winter flounder

 

Documented
(Martin 1938, McDermott 1951, Magendanzt 1969)

 

Pleuronectes putnami

Pleuronectidae

smooth flounder

 

Likely

 

 

FigC1

Fig. C1. Relationships between infection prevalence of I. obsoleta trematodes that mature in fish and the abundance of different fish groups (measured as number of individuals per fyke net catch) at salt marsh sites. Note that raw prevalence values are plotted, however all statistics are based on Anscombe transformed prevalence metrics. Three trematode species or species groups are presented: (a) Stephanostomum spp., (b) Lepocreadium setiferoides, and (c) Zoogonus rubellus. The ln(abundance) of known and likely definitive fish hosts associated with each trematode species (as identified in Table C1) is plotted (black squares, solid line). In addition, prevalence of each trematode species is plotted against the ln(abundance) of definitive fish hosts for any I. obsoleta trematode (i.e., all species presented in Table C1; open squares, hashed line).


 

Literature Cited

Linton, E. 1940. Trematodes from fishes mainly from the Woods Hole region, Massachusetts. Proceedings of the United States Natural Museum 88:1–172.

Magendanzt, M. 1969. The life history, and ultrastructural development of the epidermis, of a marine trematode, Lepocreadium setiferoides. PhD Thesis, University of New Hampshire, Durham, New Hampshire, USA.

Martin, W. E. 1939. Studies on the trematodes of Woods Hole II. The life cycle of Stephanostomum tenue (Linton). Biological Bulletin 77:65–73.

McDermott, J. J. 1951. Larval trematode infection in Nassa obsoleta (Say), from New Jersey waters. Masters Thesis. Rutgers University, New Brunswick, New Jersey, USA.

Schell, S. C. 1970. How to know the trematodes. W. C. Brown Co., Dubuque, Iowa, USA.


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