Early development and life cycle of Contracaecum multipapillatum s.l. from a brown pelican Pelecanus occidentalis in the Gulf of California, Mexico

Abstract

The initial developmental stages of Contracaecum multipapillatum (von Drasche, 1882) Lucker, 1941 sensu lato were studied using eggs obtained from the uterus of female nematodes (genetically identified) found in a brown pelican Pelecanus occidentalis from Bahía de La Paz (Gulf of California, Mexico). Optical microscopy revealed a smooth or slightly rough surface to the eggs. Egg dimensions were approximately 53 x 43 μm, although when the larvae developed inside their size increased to 66 x 55 μm. Hatching and survival of the larvae was greater at 15 ºC than 24 ºC and increased salinity resulted in a slight increase in hatching but seemed to reduce survival at 24 ºC, but not at 15 ºC. The recently hatched larvae measured 261 x 16 μm within their sheath. When placed in culture medium the larvae grew within their sheath and a small percentage (~2%) exsheathed completely (314 x 19 μm). The larvae continued to grow and develop once they had exsheathed, attaining mean dimensions of 333 x 22 μm. Although they did not moult during culture, optical microscopy revealed a morphology typical of third-stage larvae. Finally, the genetic identity found between the larvae of the parasite from mullet and adult females from the brown pelican suggests a life cycle of C. multipapillatum in which the mullet are involved as intermediate/paratenic hosts and the brown pelicans as final hosts in the geographical area of Bahía de La Paz.