Arachnologische Gesellschaft

Sensory structures and sexual dimorphism in the harvestman Dicranopalpus ramosus (Arachnida: Opiliones)

Sensory structures and sexual dimorphism in the harvestman Dicranopalpus ramosus (Arachnida: Opiliones)

Sinnesorgane und Sexualdimorphismus der Weberknechtart Dicranopalpus ramosus (Arachnida: Opiliones)

Abstract

A survey on sensory organs of both sexes of the harvestman Dicranopalpus ramosus classifies structure and frequency of campaniform sensilla, falciform setae, sensilla basiconica, slit sensilla, solenidia, spines, sensilla chaetica, trichomes (simple hairs) and plumose setae. Sensilla are equally distributed on the pedipalp tarsi of both males and females, but females show higher counts of campaniform and falciform setae than males. Females furthermore have about 1000 glandular plumose setae on each pedipalp, that at the same positions in males are replaced by sensilla chaetica. The walking legs of both sexes show a similar distribution of sensory organs, with females showing more sensilla basiconica at the legs I and II and more solenidia on the first pair of legs. Males have a large number of bipterate setae (about 2200 per specimen) at the metatarsi and tarsi of the third and fourth pair of legs. In females these are replaced by simple hairs. Although females show a similar (or slightly higher) number of leg sensilla than males, their density is higher due to their shorter legs. In both sexes the second pair of legs has the largest number of falciform setae, sensilla basiconica, chaetica and solenidia, followed by the legs I, III and IV. The first pair of legs has the highest density of falciform setae, sensilla basiconica and solenidia, followed by the legs II, III and IV. The genital operculum, sternites and tergites show a multitude of slit sensilla. The slit sensilla of the genital operculum and sternites are associated with insertion plaques of muscles operating the penis/ovipositor and regulating opisthosomal volume and hemolymph-pressure.

Im Rahmen einer Untersuchung der Sinnesorgane beider Geschlechter der Weberknechtart Dicranopalpus ramosus werden die Struktur und Anzahl der Kuppelsensillen (campaniform), sichelformigen Borsten (falciforme Setae), Riechkegel (Sensilla basiconica), Spaltsensillen, Solenidien (röhrenförmige Setae) und Dornen sowie der Haarsensillen (Sensilla chaetica), Trichome (einfache Haare) und federförmige Haare (plumose Setae) beschrieben. Die Pedipalpen-Tarsen der männlichen und weiblichen Tiere weisen identische Verteilungen der Sensillen auf, wobei die Weibchen mehr Kuppelsensillen und sichelförmige Borsten besitzen als die Männchen. Weiterhin konnte festgestellt werden, dass auf jedem weiblichen Pedipalpus 1000 gefiederte Drüsenhaare (glanduläre plumose Setae) vorkommen, wohingegen bei den Männchen an den gleichen Stellen Haarsensillen vorgefunden werden. Die Beine beider Geschlechter weisen eine ähnliche Verteilung der Sinnesorgane auf, wobei Weibchen mehr Riechkegel in den Beinen I und II und mehr Solenidien am ersten Beinpaar aufweisen. männliche Tiere besitzen eine große Anzahl zweiflügeliger Borsten (bipterate Setae) (insgesamt ca. 2200 pro Tier) auf den Metatarsen und Tarsen des dritten und vierten Beinpaares . An gleicher Stelle sind bei weiblichen Tieren einfache Haare vorzufinden. Weibchen besitzen eine ähnliche (oder höhere) Anzahl an Beinsensillen als Männchen. Da die Beine der weiblichen Tiere jedoch kürzer sind, stehen die Beinsensillen bei ihnen dichter. In beiden Geschlechtern weisen die zweiten Beinpaare die größte Anzahl an sichelförmigen Borsten, Riechkegeln, Haarsensillen und Solenidien auf, gefolgt von den ersten, dritten und vierten Beinpaaren. Auf den ersten Beinpaaren erreichen die sichelformigen Borsten, Riechkegel und Solenidien die höchste Dichte, gefolgt von den zweiten, dritten und vierten Beinpaaren. Das Genitaloperculum, die Sternite und Tergite weisen eine Vielzahl von Spaltsensillen auf. Die Spaltsensillen des Genitaloperculums und der Sternite sind mit Muskelansätzen verbunden. Diese Muskeln steuern Penis bzw. Ovipositor und regeln das Opisthosoma-Volumen und den Hämolymph-Druck.

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