Morphological variation and abnormality of cephalic hooklets of Gnathostoma spinigerum hepatic stage larvae from laboratory infected mice.

One thousand advanced third-stage larvae of Gnathostoma spinigerum from laboratory infected mice, two to five weeks after being fed with infected cyclops, were examined specifically for the morphology of their cephalic hooklets. Among these, only the 15-day old (early hepatic-stage) larvae and the 30-day old (late hepatic-stage) larvae were measured for the size of their body and hooklets. The average body size of the 15-day old and 30-day old larvae were 3.4 +/- 0.4 x 0.4 +/- 0.04 mm and 4.9 +/- 0.4 x 0.5 +/- 0.04 mm, respectively. The average size of the hooklets from rows one to four of the 15-day old larvae was 14.6 +/- 1.7 x 6.8 +/- 0.6 microm, 15.6 +/- 2.0 x 7.2 +/- 0.5 microm, 16.0 +/- 1.8 x 7.4 +/- 0.6 microm and 15.9 +/- 1.9 x 7.3 +/- 0.6 microm, respectively. Those of the 30-day old larvae were 15.1 +/- 1.7 x 7.1 +/- 0.6 microm, 16.3 +/- 1.6 x 7.5 +/- 0.7 microm, 16.5 +/- 1.7 x 7.8 +/- 0.6 microm and 16.3 +/- 1.7 x 7.6 +/- 0.8 microm, respectively. The average number of cephalic hooklets from rows one to four of the two- to five-week old larvae were 42.8 +/- 2.6, 45.3 +/- 2.8, 46.9 +/- 2.8 and 50.2 +/- 2.9, respectively. Several types of morphological variation and abnormality of the cephalic hooklets were observed. The most common ones were extra rudimentary hooklets below row four or within the four rows of hooklets (10.8%), the present of a fifth row of hooklets (1.9%), abnormal hooklets in only row four (1.2%), lobed or branched hooklets (0.5%), spiral arrangement of the four rows of hooklets (0.4%), and fragmented hooklets (0.4%).