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Male harvestmen penial armature has a remarkable morphology; however, it is poorly known regarding its functions. We examined the male genitalia of virgin and mated males of the gonyleptid Pachyloides thorellii under Scanning Electron Microscope looking for evidence that the penis could remove sperm from the female ovipositor lumen during mating. Micrographs show sperm agglutinations over and within the microsetae fields in six out of the 12 mated males studied. For the mating experiments we used only virgin females, therefore the sperm found in the penis was in all cases their own sperm. This self-sperm removal could be the extraction of sperm excess in cooperation (or not) with the females. This is the first study to show for the Order Opiliones direct evidence that a male penis contains structures that can effectively remove sperm from the female ovipositor. Further behavioral and morphological studies are needed to confirm the conditions of occurrence and participation of each sex in sperm removal processes in this species. [ABSTRACT FROM AUTHOR]

Abstract In many species of scorpions (Order Scorpiones) and spiders (Order Araneae), mating plugs (gel-like or sclerotized) are deposited in the female reproductive tract, minimizing the possibilities of further matings. Although harvestmen (Order Opiliones) have direct sperm transfer via copulatory organs (penis or spermatopositor in the male and ovipositor in the female), prior studies of the reproductive anatomy of these arachnids have not reported the occurrence of these structures. With the aid of scanning electron microscopy, we observed distinct masses of amorphous, gel-like material in the distal openings of the ovipositors of six different specimens including representatives of the families Cosmetidae (Cynorta marginalis and Flirtea picta), Gonyleptidae (Discocyrtulus bresslaui and Geraeocormobius sylvarum), Kimulidae (Kimula sp.) and Metasarcidae (Metasarcus clavifemur). Dissection of one of these structures from a specimen of the cosmetid harvestman C. marginalis revealed a detailed endocast of the internal surfaces of the female reproductive tract. Considerable interspecific variation in the relative sizes and shapes (smooth and rough) of the amorphous gel-like structures were observed, but evidence of sclerotized components (i.e., parts of the male genitalia) was not found. The location and morphology of the gel-like structures are consistent with observations of mating plugs in other arachnids. The composition, source (male, female or both) and function of these amorphous gel-like structures (i.e. effective matting plug) requires additional study. [ABSTRACT FROM AUTHOR]

Most harvestman species are dependent on high humidity levels and amenable temperatures for homeostasis. While they are known to actively choose environments with these conditions, no thermo-/hygroreceptor has yet been identified in harvestmen. Using electron microscopy, we investigated the ultrastructure of two types of hair sensilla of the armored harvestman Heteromitobates discolor (Laniatores, Gonyleptidae): namely the sensillum basiconicum and the hooded sensillum. Both structures occur in small numbers ( sensilla basiconica : 28 units; hooded sensilla: 4 units) and are distributed on the distal parts of the legs. On the distalmost tarsomeres I and II, the receptor cells of paired sensilla basiconica and single hooded sensillum occupy a large volume of the inner tissue, and appear tightly associated. The sensillum basiconicum is innervated by 3-4 dendrites and has a longitudinal slit giving the impression of a shaft with two flaps, resembling a beak. The slit probably allows for evaporation of sensillum lymph. The hooded sensillum is innervated by two bundles of three dendrites each, has two pore-like structures on its tip and displays an unusual reticulate cuticle of the shaft. Details of shaft cuticle, the evidence of evaporation of sensillum lymph, and specific innervation patterns support our hypothesis that sensilla basiconica are thermo- and/or hygroreceptors. Even though the definite function of hooded sensilla remains unclear, its putative receptor modalities are assessed by means of specific ultrastructures. Finally, we discuss with regard to functional ultrastructures as to whether the evaporation system of sensilla basiconica fits mechanisms of hygroreception as known from current literature. [ABSTRACT FROM AUTHOR]