Attenuated reproduction of Strombus gigas by an Apicomplexa: Emeriidae-like parasite in the digestive gland.

An intense and generalized sporozoan infection was detected in every population of the queen conch, Strombus gigas through the Caribbean. In this contribution we establish the relationship between occurrences of an Apicomplexa: Emeriidae-like organism and reproductive activity at San Andres archipelago, Colombia. Occurrence of the parasites was estimated counting the feeding stage Merozoites and cysts Sporozoites at 40× magnification. Nonmetric multidimensional scaling analysis (NMDS) was made to correlate the parasites stages abundance with frequency of the reproductive stages. Gametogenesis and spawning were always low coinciding with high numbers of Merozoites, a positive correlation was established between parasite abundance with reabsorption and undifferentiated stages, and negative correlation was observed between parasite abundance with maturity and spawning stages. The nonmetric multidimensional scaling (NMDS) shows that gametogenesis, maturity and spawning increase as the number of parasites decrease, factor that could be threatening reproduction of S. gigas through the Caribbean.

Testosterone levels and gular pouch coloration in courting magnificent frigatebird (Fregata magnificens): variation with age-class, visited status and blood parasite infection.

Male magnificent frigatebirds (Fregata magnificens) possess a seasonally expressed skin ornament, namely the red and inflatable gular pouch, and are, therefore, a convenient model for the study of some theories related to the evolution of possible testosterone-dependent sexual skin coloration. Here we report the findings of a study performed over four consecutive mating seasons in the Mexican national park Isla Isabel. We investigated differences in testosterone level and gular pouch coloration in courting males in relation to the categories: age-class, visited status and blood parasite infection. Gular pouch color saturation increased with age-class. Investigated frigatebirds were infected only with Haemoproteus iwa (Haemosporida, Haemoproteidae), with an overall prevalence infection of 15.5%. Prevalence of the infection increased with birds' age-class. Testosterone levels were significantly higher in infected males, who also had lighter colored gular pouches. In non-infected males, those visited by a female had higher testosterone levels than non-visited males. Gular pouch lightness and redness were negatively correlated but only redness in non-visited non-infected males was positively correlated with testosterone levels. Gular pouch saturation in visited and infected males was positively correlated with body mass, which also increased with age-class. Mated males had lower testosterone levels and lighter, less red and saturated gular pouch coloration than courting males. In summary, we found that coloration of the male skin ornament could reflect age-class (saturation), parasite infection (lightness) and mated status (all), together with indications of condition and testosterone dependency of ornament expression.

Histologic study of head cartilage degeneration in rainbow trout (Oncorhynchus mykiss) infected with the parasite Myxobolus cerebralis.

A light microscopy study of head cartilage tissue in rainbow trout alevins (Oncorhynchus mykiss) infected with the parasite Myxobolus cerebralis showed that, regardless of the presence or absence of whirling disease symptoms such as black tail and whirling swimming due to altered tail and spine morphology, some fish presented large amounts of spores lodged in the head after three months of infection. The spores were located in regions where the cartilage was extensively destroyed.

Study of the tail fin rays of rainbow trout (Oncorhynchus mykiss) infected with the parasite Myxobolus cerebralis.

A light, transmission and scanning microscope study of the rays (lepidotrichia) forming the tail fin of rainbow trout (Oncorhynchus mykiss) fingerlings infected with the parasite Myxobolus cerebralis showed that triactinomyxon adherence to the tail fin of host fingerlings occurred 10 min after infection. After 2 h of exposure, it was possible to observe triactinomyxon spores in the epidermis. Although the characteristic symptoms of the disease, such as a black tail and a change in tail morphology, were observed, there was no attack against the tissue forming the tail fin rays and triactinomyxon spores were not observed inside the leptotrichial matrix at any stage, indicating that the spores do not reach the rays or that their observation was not possible under the conditions of the present study.