Parasites and parental care in male upland bullies (Eleotridae)

Parental care of eggs by male upland bullies Gobiomorphus breviceps was studied in the field and in the laboratory, with special emphasis on the effect of infection by trematode cysts. In the field, the proportion of old eggs in the nest affected the time taken by males to return to their nest after being chased away, but only in one year of the study. No effects of male size, male parasite load, number of eggs per nest or nest characteristics were observed. In the laboratory, heavily-infected males spent more time fanning their eggs than lightly-infected ones. Smaller males also tended to spend more time fanning than large males. Male size, parasite load and number of eggs per nest had no measurable effect on the aggressiveness of guarding males towards intruders, weight loss in males or egg incubation time. Parental investments did not vary as a function of age of the eggs. All males cannibalized some of their eggs, and there appeared to be a threshold brood size below which males consumed their entire brood. Overall, results were not consistent with those of studies on other fish species, and indicate that rules of investment in parental care may be different for fish inhabiting harsh, unpredictable environments.