Hoch H, Deckert J, and Wessel A. 2006. Vibrational signaling in a Gondwanan relict insect (Hemiptera: Coleorrhyncha: Peloridae). Biology Letters 2: 222-224.

In the January 27 and 29 introductory lectures on general communication and sound, we discussed the need for any type of communication to have both a sender and a recipient. Furthermore, if the sender must employ some mechanisms to send that signal, any true recipient must have the ability to perceive or be modified by that signal. This is summarized in the Duesbery quote on sensory ecology from 1992.

Understanding that senders and recipients are both adapted to send and receive certain signals suggests that there are species or higher-level-group-specific morphologies or behaviors that allow for this communication. Thus, communication such as sound production/hearing may have associated morphological and historical data that could be useful for phylogenetic analyses if it is based on heritable and selectable structures or behaviors. These topics are explored in the two articles I selected to summarize this week.

Hoch et al. researched the sound production of a morphological structure familiar to us from the course reading—the cicadan tymbal. The authors of this study believe the tymbal structure may be one of the first sound-producing structures to appear during the Permian period. It is present in relatives of the clade Coleorrhyncha (a sister group of the true bugs, Heteroptera), which is a largely extinct lineage that persists only in areas formerly a part of the super continent Gondwanaland such as Queensland, New Zealand, and Patagonia. The lineage is highly conserved in morphology and habitat preference over the entire range, and flightless (with one exception), suggesting that this suborder has not differentiated substantially from Heteropteran ancestors in the Permian. However, the authors do not indicate if the tymbal structure is known to be present in Coleorrhyncha. Furthermore, the degree to which this ancient tymbal was actually used for communication in ancestral Heteroptera was unknown and thus tested by the researchers in this study.

Adult male specimens of an extant Coleorrrhynchan were collected and their vibrational signals recorded and amplified to be audible to the human ear (approximately 1000x). Sound analysis on these vibrations yielded rhythmic pulsing that, while not especially complicated, suggest that it is not being produced randomly or by accident. The soft forced pulse frequencies produced in the study are comparable to those produced by extant cicadas, so the authors hypothesize elements of a resonator-less tymbal organ are likely present in Coleorrhyncha.

The scope of the Hoch et al article was small, so many questions I had regarding the morphology of Coleorrhyncha and allies were unanswered. I was surprised no mention in this article was made to whether members from the suborder were known from fossil evidence and, if so, if this evidence had been used to characterize the 13 genera that form the single family classification, Peloridiidae. There was also no information on whether said fossils, museum samples, or collected samples had been examined to form a physical description of the proposed ancient tymbal organ. It is possible this data may be added to future publications on the topic.