Touch-sensitive bristles on the carapace of the mud crab Scylla paramamosain may be receptors for courtship signals
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ORIGINAL ARTICLE Biology
Touch‑sensitive bristles on the carapace of the mud crab Scylla paramamosain may be receptors for courtship signals Gunzo Kawamura1 · Teodora Uy Bagarinao2 · Chi Keong Loke1 · Hsein‑Loong Au1 · Annita Seok Kian Yong1 · Leong‑Seng Lim1 Received: 3 August 2020 / Accepted: 26 October 2020 © Japanese Society of Fisheries Science 2020
Abstract Bristle patches on the carapace behind the eyes were found for the first time in both males and females of the four species of mud crab Scylla spp. Electrocardiography revealed that the bristle patches of Scylla paramamosain were sensitive to touch (with a glass capillary) but not to chemical stimulation (with sugarcane juice). To elucidate the function of these touch signals, the courtship behaviour of S. paramamosain was video-recorded in a broodstock tank. A male approached a female, extended a walking leg over her carapace, touched her bristle patches with a dactyl, mounted her, and probed the bristle patches further with the third maxillipeds. Touch stimulus may be a signal for courtship in Scylla and one of the chain stimuli for the completion of mating behaviour. Keywords Electrocardiography · Video observation · Courtship signal · Mating
Introduction The courtship behaviour of crustaceans involves initial interactions between a male and a female by way of chemical, visual or acoustic communication, followed by mate guarding of the receptive female, and finally copulation. Pheromones significantly influence the sexual attraction and courtship behaviour of several crustacean species (reviewed in Schmidt and Mellon, 2011; Breithaupt and Hardege 2012). Mate recognition occurs only after physical contact in the Chinese mitten crab Eriocheir sinensis (Herborg et al. 2006). Terrestrial and semiterrestrial crab species use visual signals such as claw waving (Murai and Backwell 2005) and claw colour (Detto 2007; Baldwin and Johnsen 2012). Acoustic signals for mating have been well documented in fiddler crabs and ghost crabs (Salmon and Atsaides 1969; Horch and Salmon 1969). * Leong‑Seng Lim [email protected] 1
Borneo Marine Research Institute, Universiti Malaysia Sabah, 88400 Kota Kinabalu, Sabah, Malaysia
Aquaculture Department, Southeast Asian Fisheries Development Center, 5021 Tigbauan, Iloilo, Philippines
2
Touch is also important for sexual interaction in a variety of crabs. In the fiddler crabs, genus Uca, sexual activity depends mainly on tactile signals during the initial stages of mating (Schöne 1968). The male fiddler crab approaches the female and strokes the anterior part of her carapace (Crane 1975). The male tanner crab Chionoecetes bairdi extends the cheliped and touches the surface of the female’s carapace (Donaldson and Adams 1986). In the flower crab Charybdis feriata, the male touches the female by extending the larger chela, and finally embraces her with his walking legs (Soundarapandian et al. 2013). Animal signalling can only be understood by elucidating how signals are perceived and processed by signal receivers (Guil
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