Ultrastructure of the sexually dimorphic tarsal glands and tegumental glands in gonyleptoid harvestmen (Opiliones, Laniatores)

Abstract

In at least four closely related families of the diverse harvestmen lineage Gonyleptoidea, males may possess sexually dimorphic tarsal glands in the swollen tarsomeres of the basitarsus and/or metatarsus of leg I. The first histological and ultrastructural examination of the sexually dimorphic tarsal glands in leg I focused only on Manaosbiidae. In this study, we examine the morphology and ultrastructure of the sexually dimorphic glands, and their associated glandular openings, found in the basitarsus and/or metatarsus of leg I of males representing Cosmetidae, Gonyleptidae, and Cranaidae (glandular openings only). In cosmetids and gonyleptids, the tarsal glands are made up of 20–60 glandular units that form distinct groups within the prolateral and retrolateral half of the tarsomere. Each glandular unit consists of a pair of terminal secretory cells, an intercalary cell wrapped around the receiving canal, and a canal cell tightly wrapped around the length of the conducting canal. Cosmetidae, Gonyleptidae, and Cranaidae exhibit remarkably similar tarsal glands and gland openings although the location of the glands in the leg differs slightly among them. Males of these three families exhibit markedly different glands and glandular openings compared to males of the family Manaosbiidae. The sexually dimorphic tarsal glands may provide an important morphological character for determining phylogenetic relationships among gonyleptoid families. Finally, we provide morphological and ultrastructural data for the common tegumental glands. These data indicate that the sexually dimorphic tarsal glands are strikingly similar to, and may possibly be derived from, the tegumental glands.

The harvestman tarsus and tarsal flexor system with notes on appendicular sensory structures in laniatores

“…A tubular hemocoelic vessel, hereafter referred to simply as a "vessel," runs along the midline of the ventral surface of the leg and contains the inferior depressor/flexor tendon ( Fig. 3A; see Proud and Felgenhauer, 2013, this volume). The inferior depressor/flexor tendon enters through the dorsal wall of the vessel within the metatarsus and continues to the insertion point on the pretarsus.…”

“…The glandular units consist of a secretory cell, intercalary cell, and cuticular duct with an associated enveloping cell ( Fig. 3A; see Proud and Felgenhauer, 2013, this volume). inermipes) that has been cut with a razor blade showing the superior tarsal tendon in the hemocoelic space and the inferior tarsal tendon within the leg vessel.…”

Sexual dimorphism in the Arachnid orders

“…Chemical communication has also been correlated to sex in Opiliones. Tegumental gland openings located on the tarsus of the first, fourth and occasionally third leg, or the femur of leg one, are present in males but not females ( Willemart et al, 2010 ; Proud & Felgenhauer, 2013 ; Da Silva Fernandes & Willemart, 2014 ). Males rub the glandular pores on surfaces, and control the flow of pheromones excreted ( Da Silva Fernandes & Willemart, 2014 ; Murayama & Willemart, 2015 ).…”

Interspecific variation in the microanatomy of cosmetid harvestmen (Arachnida, Opiliones, Laniatores)

“…Gnaspini and Rodrigues () surveyed the morphology of the external openings of the ozopores of over 30 species of laniatorean harvestmen, including three cosmetid species, and found that cosmetid harvestmen have rounded, “simplified” ozopores in anatomical positions different from other gonyleptoideans. Proud and Felgenhauer () examined sexual variation in the morphology and ultrastructure of the tarsal glands of four cosmetid species. Bennett and Townsend () described intraspecific variation in ovipositor morphology for the cosmetid harvestman Cynortula granulata .…”