Comparison of Egg Morphometrics and Number of Two Molecularly Delineated Species of Diplostomum (Digenea)
2018
Lapierre, Angela Rose | McLaughlin, J Daniel | Marcogliese, David J.
While it generally has been accepted that evolutionary pressures may drive parasitic worms to produce many small eggs to overcome the challenges of transmission, recent studies suggest wide variability in reproductive strategies among such worms. Although egg morphometrics and numbers have been reported from many species of Diplostomum, the presence of cryptic species has resulted in uncertainty in morphometric measurements for different life history stages. Here we examine differences between egg characteristics of 2 molecularly delineated species of Diplostomum (Digenea). We investigate whether interspecific differences exist in egg morphometrics or egg number and test if there are intraspecific relationships between size of the egg and the hindbody of adult worms or between size of the egg and fecundity. Egg measurements were obtained from both those collected in feces of experimentally infected ring-billed gulls (Larus delawarensis) and those observed in stained adult specimens of Diplostomum spp. Regardless of the source of measurement, there was a significant difference in the length of the eggs and in egg number between the 2 species, while there was no difference in the widths. Larger worms did not produce significantly larger eggs in either species. Further, egg size was not correlated with the number of eggs present in the stained specimens of either species; smaller eggs were not present in greater numbers. Egg morphometrics can assist in differentiating between these 2 species of Diplostomum. Furthermore, differences in egg sizes and number may reflect other potential differences in life history traits between the 2 species, such as miracidial longevity and infectivity and cercarial output, among others, that still need to be investigated.
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