Abstract：
:From the elongated neck of the giraffe to the elaborate train of the peacock, extreme traits can result from natural or sexual selection (or both). The extreme chelicerae of the long-jawed spiders (Tetragnatha) present a puzzle: do these exaggerated chelicerae function as weapons or genitalia? Bristowe first proposed that Tetragnatha chelicerae function as a holdfast because these spiders embrace chelicerae during mating. This hypothesis has remained untested until now. Here, we use functional allometry to examine how extreme chelicerae develop and perform in the long-jawed spider Tetragnatha elongata. Similar to other Tetragnatha species, chelicerae were longer in adult males than in adult females. Overall, we confirm Bristowe's hypothesis: elongation only occurred in the adult stage. However, we propose that chelicerae function as more than a holdfast in T. elongata. Male chelicerae exhibited positive allometry, which suggests scaling as weapons rather than genitalia. However, fieldwork revealed that the operational sex ratio is female-biased and both adult male-male competition and sexual cannibalism were rarely observed. Consequently, we propose that the positive allometry of male chelicerae may result from sexual selection to mechanically mesh with larger and more fecund females. Evidence for mechanical mesh includes multiple traits ranging from apophyses and grooves to guide teeth on the basal portion of the chelicerae. In contrast, we propose that chelicerae of females are analogous to the female peacock's tail: shortened by natural selection limiting the exaggeration of sexually selected traits. Indeed, females had increased foraging efficiency compared to males and exhibited negative cheliceral allometry. We discuss the implications for the evolution of elongated chelicerae in Tetragnatha.
journal_name
J Morpholjournal_title
Journal of morphologyauthors
Danielson-François A,Sullivan HNdoi
10.1002/jmor.21282subject
Has Abstractpub_date
2020-10-19 00:00:00eissn
0362-2525issn
1097-4687pub_type
杂志文章abstract：:Sexual dimorphism in the distribution of antennal sense organs is common among adults of the genus Periplaneta. In three out of the four strains of Periplaneta americana examined, adult males had more contact chemoreceptros than females. In the fourth strain of P. americana and in P. australasiae, P. brunnea, P. fulig...
journal_title：Journal of morphology
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更新日期：1996-10-01 00:00:00
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