02063nas a2200181   4500008004100000245009900041210006900140520137900209653002101588653001701609653001401626653002601640653001201666100002801678700002201706700002201728856013101750       2019                        eng d00aGrowling from the gut: co-option of the gastric mill for acoustic communication in ghost crabs0 aGrowling from the gut cooption of the gastric mill for acoustic 3 a<p>Animal acoustic communication systems can be built upon co-opted structures that become specialized for sound production or morphological novelties. The ghost crab, Ocypode quadrata, evolved a novel stridulation apparatus on the claws that is used during agonistic interactions, but they also produce a rasping sound without their claw apparatus. We investigated the nature of these sounds and show that O. quadrata adopted a unique and redundant mode of sound production by co-opting the gastric mill (grinding teeth of the foregut). Acoustic characteristics of the sound are consistent with stridulation and are produced by both male and female crabs during aggressive interactions. Laser Doppler vibrometry localized the source of maximum vibration to the gastric region and fluoroscopy showed movement of the gastric mill that coincided with stridulation. The lateral teeth of the gastric mill possess a series of comb-like structures that rub against the median tooth to produce stridulation with dominant frequencies below 2 kHz. This previously undescribed gastric stridulation can be modulated and provide a means of assessment during aggressive interactions, similar to the use of the claw stridulation apparatus. This functional redundancy of stridulation in crabs offers unique insights into the mechanisms of evolution of acoustic communication systems.</p>
10aanimal behaviour10abioacoustics10aCrustacea10afunctional morphology10aOcypode1 aTaylor, Jennifer, R. A.1 adeVries, Maya, S.1 aElias, Damian, O.  uhttps://royalsocietypublishing.org/doi/10.1098/rspb.2019.1161https://royalsocietypublishing.org/doi/pdf/10.1098/rspb.2019.1161