Development and metamorphosis in the male pedipalp of the cob-web spider Parasteatoda tepidariorum

by Felix Simon Christian Quade
Doctoral thesis
Date of Examination:2019-02-01
Date of issue:2019-02-12
Advisor:Prof. Dr. Nikola-Michael Prpic-Schäper
Referee:Prof. Dr. Ernst A. Wimmer
Referee:Prof. Dr. Tim Salditt
Persistent Address: http://dx.doi.org/10.53846/goediss-7284

 

 

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Description:Development and metamorphosis in the male pedipalp of the cob-web spider Parasteatoda tepidariorum

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Abstract

English

Tracing from marine ancestors, spiders have adapted to a terrestrial lifestyle independent from the insects. Many of the adaptations of spiders to life on land involve the shape and function of their appendages. From these appendage modifications, the transformation of the tarsal tip of the male pedipalp into an intromittent organ, the bulbus organ, is particularly interesting. Being an autapomorphy for spiders (i.e. a distinctive feature that is unique to a given taxon) the bulbus’ role as intromittent organ for sperm transfer on land accounts for a large part of their evolutionary success. My research on the adult morphology and development of the bulbus organ of the theridiid spider model Parasteatoda tepidariorum has answered fundamental questions. It was confirmed that the adult bulbus is built up in a tripartite way, as described by Agnarsson and colleagues (2007). It is built of the subtegulum, tegulum and the embolic section which are connected through membranes, the haematodochae. The embolic section gives rise to the sclerites which are involved in the connection and penetration of the female during the copulatory act. The hitherto existing homology statements for two sclerites were corrected and the correct terms discussed. Furthermore, an innervation was found and a sensilla, which appears to be similar to that in the bulbus of Philodromus cespitum (Sentenská et al. 2017). The data on the development showed that the bulbus originates in the claw fundament and its primordium is already built in the stage before the penultimate moult. Through a newly discovered mechanism tibia and cymbium are built from scratch which involves coagulation of haemolymph and reorganisation of the coagulated material by histoblast-like cell clusters. Together these findings clearly show that a comprehensive analysis of the morphology over its ontogenesis yields deep insights. However, at the same time new questions arose which now must be answered with future research endeavours.
Keywords: Bulbus organ; Spider; Morphology; Development; µCT
 
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