Caste-specific visual adaptations to distinct daily activity schedules in AustralianMyrmeciaants

Abstract

Animals are active at different times of the day and their activity schedules are shaped by competition, time-limited food resources and predators. Different temporal niches provide different light conditions, which affect the quality of visual information available to animals, in particular for navigation. We analysed caste-specific differences in compound eyes and ocelli in four congeneric sympatric species of Myrmecia ants, with emphasis on within-species adaptive flexibility and daily activity rhythms. Each caste has its own lifestyle: workers are exclusively pedestrian; alate females lead a brief life on the wing before becoming pedestrian; alate males lead a life exclusively on the wing. While workers of the four species range from diurnal, diurnal-crepuscular, crepuscular-nocturnal to nocturnal, the activity times of conspecific alates do not match in all cases. Even within a single species, we found eye area, facet numbers, facet sizes, rhabdom diameters and ocelli size to be tuned to the distinct temporal niche each caste occupies. We discuss these visual adaptations in relation to ambient light levels, visual tasks and mode of locomotion.

Looking and homing: how displaced ants decide where to go

“…In both cases, it is likely to help to first find the best alignment of views through rotational scanning. Yet, given the large visual field of ant compound eyes, it is not entirely obvious why displaced ants have to use rotational scanning movements, especially because their compound eyes do not have a particularly well-developed acute zone such as a frontal area of increased resolution and sensitivity (for eye maps of M. croslandi, see [25]) that would need to be directed at features of interest [32]. So why do ants have to look around when released at unfamiliar locations?…”

“…The ants are individually foraging, with no evidence of scout-or trail pheromone-guided recruitment, and are known for their ability to jump and for their potent sting [26]. They have unusually well-developed compound eyes with each eye having nearly 2400 facets [25]. We studied ants from a single nest (35815 0 05.59 00 S, 149809 0 33.18 00 E) in an urban park in Canberra, Australia.…”

“…Jack jumper ants, M. croslandi, are large (ca 1 cm body length) and strictly day-active ants that occur along the east coast of Australia [25]. The ants are individually foraging, with no evidence of scout-or trail pheromone-guided recruitment, and are known for their ability to jump and for their potent sting [26].…”

Light and dark adaptation mechanisms in the compound eyes of Myrmecia ants that occupy discrete temporal niches

“…This is reflected in the size of their eyes, with some species having more than 3000 ommatidia per eye (Gronenberg, 2008;Narendra et al, 2011), which is unusually high for ants. For instance, the desert ants, which are well known for their navigation capacities, have about 500 (in Melophorus bagoti; Schwarz et al, 2011) to 1000 ommatidia (in Cataglyphis fortis; Menzi, 1987) in each eye.…”

Experience, corpulence and decision making in ant foraging

“…Providing for others is taken to extremes in the eusocial insects, such as bees, wasps, ants and termites, in which a minority of individuals may supply the whole colony, while others stay in the nest. Environmental factors such as temperature (Ruano et al, 2000) and light intensity (Narendra et al, 2011) are important in regulating foraging in social insects. Beyond these factors, social insect foragers must cater for the needs of many individuals, and so the colony needs to be able to modulate its foraging effort when demands change.…”