Mark C. Rigby

Why should parasite resistance be costly

Parasite resistance is sometimes associated with fitness costs. Costs of resistance are fundamentally important in epidemiology, and in the ecology and evolution of host-parasite interactions. The cost of resistance is often envisioned as the cost of re-allocating limiting resources to resistance machinery from other traits. This popular paradigm has resulted in a spate of research that assumes a fitness cost to resistance. We comment on this trend and propose a working framework of various resistance means and mechanisms. Within these means and mechanisms, we suggest that many are not likely to incur significant fitness costs.

Parasites of coral reef fish recruits, Epinephelus merra (Serranidae), in French Polynesia

Honeycomb grouper recruits Epinephelus merra (Serranidae) from 2 recruitment events on Moorea Island, French Polynesia, were examined for internal parasites. Trypanorhynch blastocysts (Eucestoda: Trypanorhyncha) and encysted phyllobothriid metacestodes (Eucestoda: Phyllobothriidae) were found in recruits from both events. Fish from the second event were examined later as juveniles and were found to harbor apparently melanized parasites. Neither parasite was found in adults. Evidence suggests these patterns are not due to differential mortality among recruits but to the elimination of parasites by host immune responses. The data also suggest that pelagic fish larvae may represent a dispersal mechanism for parasites if transfer occurs before the death of the parasite.

CUCULLANIN NEMATODES FROM CORAL REEF FISHES OF FRENCH POLYNESIA, WITH A DESCRIPTION OF CUCULLANUS FALIEXAE N. SP. (NEMATODA: CHITWOODCHABAUDIIDAE)

Cucullanus faliexae n. sp. is described from the moray eel Gymnothorax javanicus (Muraenidae) collected in Rangiroa (Tuamotu Islands, French Polynesia) in the South Pacific and is reported from the same host collected in Moorea (Society Islands, French Polynesia). This nematode is distinguished from its congeners by its protrubant anus and the presence of a single pair of subdorsal postanal papillae. Cucullanus faliexae resembles C. laurotravassosi from which it is distinguished by the farther anterior position of the first pair of male caudal preanal papillae and by the greater size of its spicules. Cucullanus bourdini Petter and Le Bel, 1992 is reported from the coral reef fishes Balistapus undulatus (Balistidae), Lutjanus gibbus (Lutjanidae), and Myripristis kuntee (Holocentridae) from French Polynesia. Additionally, Cucullanus sp. is reported from the coral reef fish Sufflamen bursa (Balistidae) in Moorea and Rangiroa. Given that C. faliexae and C. bourdini have been found in widely disparate locations between which their definitive hosts cannot migrate, it would seem likely that the life cycles of these worms include an intermediate or transport host that has a greater capability for dispersal.

Two New Species of Camallanus (Nematoda: Camallanidae) From Freshwater Turtles in Queensland, Australia

Abstract We describe 2 new species of Camallanus (Nematoda: Camallanidae) from freshwater turtles collected in Queensland, Australia: Camallanus nithoggi n. sp. from Elseya latisternum (Gray) and Camallanus waelhreow n. sp. from Emydura krefftii (Gray), Emydura macquarrii (Gray), and Em. macquarrii dharra Cann. The only Camallanus sp. previously reported from turtles is C. chelonius Baker, 1983 (all other species in the family have been transferred to Serpinema). The 2 new species described here differ from C. chelonius in the number of male preanal papillae (7 vs. 6 in C. chelonius), the number of male postanal papillae (5 vs. 4 in C. chelonius), and the number of buccal capsule ridges. Additionally, we removed the tissues overlying the buccal capsule and used scanning electron micrographs (SEM) to show that the peribuccal shields extend laterally from the buccal capsule, the basal ring is separated from the buccal capsule by a narrow isthmus, and there is a buttress along the lateral margin of the buccal capsule that has not previously been observed in species of Camallanus.

Statistical Reanalysis of the Distinction Between Spirocamallanus istiblenni and S. monotaxis (Nematoda: Camallanidae)

In the central Pacific, the nematodes Spirocamallanus istiblenni and S. monotaxis (Camallanidae) are common intestinal parasites of coral reef fishes. The 2 worm species are encountered in hosts in similar environments and are very similar morphologically. In recent published redescriptions, only 1 character was found to differ between the 2 species. Because that character had not previously been examined among worms of this family and because the original authors did not statistically test their results, the morphological data are here statistically reexamined for consistency with the differentiation between the 2 species. Both a discriminant function analysis and a hierarchical cluster analysis support the existing species designations based on morphological data. These analyses reaffirmed the conclusions of previous studies; i.e., the relative position of the males second preanal papilla is the only diagnostic characteristic.