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

Abstract

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 booklets. 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 booklets. The average body size of the 15-day old and 30-day old larvae were 3.4 ± 0.4 × 0.4 ± 0.04 mm and 4.9 ± 0.4 × 0.5 ± 0.04 mm, respectively. The average size of the booklets from rows one to four of the 15-day old larvae was 14.6 ± 1.7 × 6.8 ± 0.6 μm, 15.6 ± 2.0 × 7.2 ± 0.5 μm, 16.0 ± 1.8 × 7.4 ± 0.6 μm and 15.9 ± 1.9 × 7.3 ± 0.6 μm, respectively. Those of the 30-day old larvae were 15.1 ± 1.7 × 7.1 ± 0.6 μm, 16.3 ± 1.6 × 7.5 ± 0.7 μm, 16.5 ± 1.7 × 7.8 ± 0.6 μm and 16.3 ± 1.7 × 7.6 ± 0.8 μm, respectively. The average number of cephalic booklets 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 booklets were observed. The most common ones were extra rudimentary booklets below row four or within the four rows of booklets (10.8%), the present of a fifth row of booklets (1.9%), abnormal booklets in only row four (1.2%), lobed or branched booklets (0.5%), spiral arrangement of the four rows of booklets (0.4%), and fragmented booklets (0.4%).