Microphallus

Hechinger, Ryan F., 2012, Faunal survey and identification key for the trematodes (Platyhelminthes: Digenea) infecting Potamopyrgus antipodarum (Gastropoda: Hydrobiidae) as first intermediate host, Zootaxa 3418, pp. 1-27 : 18-19

Microphallus sp. "poulini"

(14. Mipo; Figs. 1 , 25–27 )

Stages: sporocysts (daughter) and cercariae

Host: Potamopyrgus antipodarum

Site in host: Sporocysts in gonad, digestive gland, basal visceral mass, and mantle

Voucher localities: Waimakariri River, South Island (-43.4148o lat, 172.6517o long); Opihi River, South Island (-44.1682o lat, 170.9422o long); Sutton Stream, South Island (-45.5971o lat, 170.0949o long)

Prevalence: 2% (n = 100) at Waimakariri; 2% (n = 100) at Opihi; 0.06% (n = 160) at Sutton

Specimens deposited: USNPC #s: 105688-105690

Diagnosis: Sporocyst translucent, globose to oblong (2:1 length:width). Length ~400–500. Developing cercariae number up to over 20.

Cercaria non-oculate with simple tail, no ventral sucker, prominent penetration glands, and oral stylet. Body length ~90–130. Tail length 1/2 to 1 times body length. Penetration glands post-equatorially in the third fourth of body. Stylet length ~12. Penetration glands can extrude contents into the gland ducts that become inflated anteriorly, resulting in gland bodies being less apparent. Penetration glands in many cercariae often opaque brown, in smaller, compact cluster just post-equator. In some infections, unusual cercariae occur alongside the normal cercariae: they are immobile, larger (length up to 180), elliptical, with the smaller, rounded, opaque, brown penetration glands, and appear to lack tail. I do not know whether this represents ontogenetic variation, dead cercariae, or something else.

Remarks: The “normal” cercariae from some infections are consistently under 100 microns long, while those from others appear to typically be around 130. This may represent intraspecific variation or the existence of multiple microphallid species.

This species appears to have not been included in Winterbourn (1974). However, explaining my working name, it is the “ Microphallus sp.” that has been the subject of several investigations out of Dr. Robert Poulin’s research group at Otago University, Dunedin, South Island. This work has focused on metacercariae, particularly their impacts on second intermediate hosts, which are copepods and amphipods (e.g., Coats et al. 2010; Hansen & Poulin 2005; Rauque et al. 2011). Please consult the literature for additional research.

Figures

FIGURE 1. General characteristics of the parthenitae and cercariae of the trematodes infecting Potamopyrgus antipodarum as first intermediate host. Microphallus sp. “ livelyi ” (sp. 13), whose embryos develop directly to metacercariae, is not figured. Species numbers and codes follow Table 1 and species accounts. Cercariae are all to scale, with additional magnified views of three small cercariae (indicated by dashed lines). Parthenitae are not to scale. Scale bars consistently indicate 100 µm.

FIGURES 25 – 27. Microphallus sp. “ poulini ” 25, Sporocyst, live (Sutton Stream voucher). Scale bar = 100. Numerical scale division = 10. 26, Cercariae, showing the two observed forms, live (Waimakariri River voucher). Scale bar = 100. Numerical scale division = 10. 27, Cercaria showing inflated penetration-gland ducts, live (Opihi River voucher). Scale bar = 100. Numerical scale division = 2.5.