Parental care patterns increase offspring fitness but may drive energetic costs to parents. The costs associated with parental care can change over time, decreasing the condition of parents that experience prolonged parental care. Thus, males can modulate parental effort based in the relative fitness cost/benefit pay-offs under different stages and environmental conditions. The present study assesses the condition of parental males of Abedus dilatatus Say by measuring their lipid, glycogen and carbohydrate contents. We compare the condition in parental males that have experienced recent and prolonged care and that were also collected in the summer and winter. Waterbug males provide parental care via carrying and ventilating eggs on their back. Winter males are smaller and carry fewer eggs compared with summer males. Males with recent care and carrying more eggs present a more lipid content. However, at the end of care, males carrying more eggs present less lipids than males with smaller egg-pads. Additionally, we find that males collected in the summer present more carbohydrates than males in the winter. Moreover, larger males with prolonged care present less carbohydrates than smaller males, in contrast to males with recent care where there is a positive relationship between size and carbohydrate content. Our results suggest that parental care in A. dilatatus may be a sexually-selected trait, as has been found in related species, and further experiments could test this idea. This is the first study to provide evidence of physiological costs related to exclusive paternal care in arthropods.

Secondary sexual traits can be indicators of individual condition that may present seasonal polyphenism as a result of the differential costs of expression along the season. Wing spots in male damselflies of the Calopterygidae family are secondary sexual traits associated with intrasexual competition and mate choice. Hetaerina titia Drury is a calopterygid damselfly where males show red and black wing spots, contrasting with other species of the genus whose males only express a red wing spot. In the present study, we evaluate the seasonal variation of the expression of male's red and black wing spots and their allometric patterns. Additionally, we measure male condition in the form of proteins, lipids, soluble carbohydrates and glycogen in early and late seasons. Black wing spots present higher variation than red wing spots and males of the late season are more pigmented. Allometry is positive for wing red spot in the early season and for black spot in the late season. Males of the late season present a higher concentration of proteins, soluble carbohydrates and glycogen, although there is no variation in the lipid content. The results of the present study suggest that, in H. titia males, black pigmentation replaces the function of the red pigmentation to signal condition. Both traits, however, may be heavily affected by environmental situations (e.g. food availability).

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