Increased abundance of snails and trematode parasites of <Emphasis Type="Italic">Fundulus heteroclitus</Emphasis> (L.) in restored New Jersey wetlands

The Hackensack Meadowlands District is a large heavily degraded, brackish marsh system in the urbanized northeastern region of New Jersey, USA. Six study sites were used, three of which were restored (Mill Creek, Skeetkill Creek and Vince Lombardi), and three others were unrestored (Richard DeKorte Park, Cedar Creek and Kingsland Creek). Highly significant differences were found with respect to snail abundance and gill parasite abundance. In the three restored sites, significantly more Littoridinops tenuipes were found, and Fundulus heteroclitus had significantly more digenean trematode metacercariae gill infections than at unrestored sites. As habitat quality improves following restoration, the number of suitable digenean trematode parasite hosts multiplies as substrate for benthic invertebrates (first intermediate host) increases and usage by other species, such as Fundulus spp. (second intermediate host), is encouraged, which then attracts more wading birds (definitive host). Though the restoration process enhances trophic complexity, including primary consumers (gastropods), secondary consumers (fish) and tertiary consumers (wading birds), and ultimately parasite diversity, restoration also helps facilitate parasite life cycles.     

Does parasitic infection compromise host survival under extreme environmental conditions? The case for Cerithidea californica (Gastropoda: Prosobranchia)

Summary This laboratory study examined the influence of parasitic infection by larval trematodes on the survival of extreme environmental conditions by the salt marsh snail, Cerithidea californica. Experimental treatments simulated the durations, combinations, and levels of potentially lethal environmental extremes to which the snail is exposed in its natural habitat, as determined from long-term field measurements. No significant difference was found in the rates of mortality suffered by infected and uninfected snails when exposed to simulated natural extremes of water temperature, water salinity, or exposure in air. Exposure to low levels of dissolved oxygen was the only treatment that caused differential mortality: infected snails died at higher rates than uninfected. This differential mortality was accentuated by high water temperature, and varied with the species of infecting parasite. The potential impact of this interaction between parasitism and anoxia on snail survival and population dynamics is discussed.     

Schistosoma mansoni: Electron probe X-ray microanalysis of the elemental composition of the tegument and subtegumental tissues of adult worms

The elementary composition [Na, Mg, P, S, Cl, K, Ca and Fe] of the tegument, tegumental spines, and subtegumental tissues of adult male and female Schistosoma mansoni have been determined by electron probe X-ray microanalysis of unfixed, freeze-dried cryosections. Statistical analysis of the results suggests that there are distinct differences in the elemental composition of the tissues both between and within individual male and female worms, and between male and female worms in general. In particular, there were significant variations in the elemental contents of the tissues between individual male and female worms, which may reflect differences in the physiology and/or metabolic state of the worms. Significant differences in the elemental composition of the various tissues examined within individual worms were also found. In general, in both male and female worms, there were significantly higher elemental levels in the tegument, as opposed to the subtegumental tissues. The elemental composition of the tegumental spines in both male and female worms differed from that of the tegumental cytoplasm, although the differences in the elemental composition between spines from male and female worms reflected the differences in the elemental content between the teguments themselves. Differences in the elemental composition of the tissues between male and female worms were also found, with the female tegument containing significantly higher elemental levels (with the exception of Cl) than the male tegument. In particular, the tegument of female worms contained higher levels of calcium and, in relatively small areas, isolated calcium-containing granules. This higher tegumental calcium level in female worms may reflect a higher calcium demand by sexually mature female worms due to the presence, within the mature vitelline cells, of calcium-containing corpuscles and the production of large numbers of eggs.