Biology subjects

Narendra, A.

Publications and source records attributed to Narendra, A..

3 recordsLinked to original sources

bioRxiv2023

Parallel and divergent morphological adaptations underlying the evolution of jumping ability in ants

Jumping is a rapid locomotory mode widespread in terrestrial organisms. However, it is a rare specialization in ants. Forward jumping has been reported within four distantly related ant genera: Gigantiops, Harpegnathos, Myrmecia, and Odontomachus. The temporal engagement of legs/body parts during jump, however, varies across these genera. It is unknown what morphological adaptations underlie such behaviors, and whether jumping in ants is solely driven directly by muscle contraction or additionally relies on elastic recoil mechanism. We investigate the morphological adaptations for jumping behavior by comparing differences in the locomotory musculature between jumping and non-jumping relatives using x-ray micro- CT and 3D morphometrics. We found that the size-specific volumes of the trochanter depressor muscle (scm6) of the middle and hind legs are 3-5 times larger in jumping ants, and that one coxal remotor muscle (scm2) is reduced in volume in the middle and/or hind legs. Notably, the enlargement in the volume of other muscle groups is directly linked to the legs or body parts engaged during the jump. Furthermore, a direct comparison of the muscle architecture revealed two significant differences between in jumping versus non-jumping ants: First, the relative Physiological Cross-Sectional Area (PCSA) of the trochanter depressor muscles of all three legs were larger in jumping ants, except in the front legs of O. rixosus and M. nigrocincta; second, the relative muscle fiber length was shorter in jumping ants compared to non-jumping counterparts, except in the front legs of O. rixosus and M. nigrocincta. This suggests that the difference in relative muscle volume in jumping ants is largely invested in the area (PCSA), and not in fiber length. There was no clear difference in the pennation angle between jumping and non-jumping ants. However, the length of hind legs relative to body length was longer in jumping ants. Based on direct comparison of the observed vs. possible work and power output during jumps, we surmise that direct muscle contractions suffice to explain jumping performance, in two species, but elastic recoil is likely important in one. We suggest that increased investment in jumping-relevant musculature is a primary morphological adaptation that separates jumping from non-jumping ants. These results elucidate the common and idiosyncratic morphological changes underlying this rare adaptation in ants.

evolutionary biology↗

bioRxiv2022

Deconstructing a visual signal: the role of motion and colour in predator deterrence

Visual animal communication, whether to the same species or to other species, is largely conducted through dynamic and colourful signals. For a signal to be effective, the signaller must capture and retain the attention of the receiver. Signal efficacy is also dependent on the sensory limitations of the receiver. However, most signalling studies consider movement and colour separately, resulting in a partial understanding of the signal in question. We explored the structure and function of predator-prey signalling in the jumping spider-tephritid fly system, where the prey performs a wing waving display that deters an attack from the predator. Using a custom-built spider retinal tracker combined with visual modelling, and behavioural assays, we studied the effect of fly wing movement and colour on the jumping spiders visual system. We show that jumping spiders track their prey less effectively during wing display and this can be attributed to a series of fluctuations in chromatic and achromatic contrasts arising from the wing movements. These results suggest that displaying flies deter spider attacks by manipulating the movement biases of the spiders visual system. Our results emphasise the importance of receiver attention on the evolution of interspecific communication.

animal behavior and cognition↗

bioRxiv2021

Ocellar spatial vision in Myrmecia ants

In addition to the compound eyes insects possess simple eyes known as ocelli. Input from the ocelli modulates optomotor responses, flight-time initiation and phototactic responses, behaviours that are predominantly mediated by the compound eyes. In this study, using pattern electroretinography (pERG), we investigated the contribution of the compound eyes to ocellar spatial vision in the diurnal Australian bull ant, Myrmecia tarsata by measuring the contrast sensitivity and spatial resolving power of the ocellar second-order neurons under various occlusion conditions. Furthermore, in four species of Myrmecia ants active at different times of the day and in European honeybee, Apis mellifera, we characterized the ocellar visual properties when both visual systems were available. Among the ants, we found that the time of activity had no significant effect on ocellar spatial vision. Comparing day-active ants and the honeybee we did not find any significant effect of locomotion on ocellar spatial vision. In M. tarsata, when the compound eyes were occluded, the amplitude of the pERG signal from the ocelli reduced by three times compared to conditions when the compound eyes were available. The signals from the compound eyes maintained the maximum contrast sensitivity of the ocelli as 13 (7.7%), and the spatial resolving power as 0.29 cpd. We conclude that ocellar spatial vison improves significantly with input from the compound eyes, with a noticeably larger improvement in contrast sensitivity than in spatial resolving power.

evolutionary biology↗