The Y-organs (YOs) synthesize and secrete molting hormones, and thus regulate crustacean growth and reproduction. However, the YOs of the orange mud crab Scylla olivacea is yet to be described due to its minute size and ambiguous feature. This study describes the location, morphological characteristics, histology, and the changes of YOs at different molt stages, and examines in vitro ecdysteroid secreted by the YOs of S. olivacea. Mature male crabs (> 90 mm carapace width, CW) were used to identify the location of the YOs while male juveniles (50-65 mm CW) at three molt stages (intermoult, premoult, postmoult) were dissected for the characterization of 20-Hydroxyecdysone (20E) levels. The yellowish-white, compact, and oval-shaped YOs are located in pairs at the anterior cephalothorax region, beneath the mandibular external adductor muscle, anterior to the branchial chamber space, and around the end of the nerve tract. The YOs index and YO's cell diameter increased from postmoult to premoult; YO's diameter increased only during premoult stage. Under electron microscopy, the YO's surface morphology is rough, bumpy, network-like, and porous, with several lacunar system tubules. High concentrations of haemolymph 20E during premoult correlated with the changes in the characteristics of YOs at this stage. The presence of ecdysteroid in YOs was confirmed by high performance liquid chromatography (HPLC). The characteristics of the YOs of S. olivacea are similar to the YO descriptions of other brachyurans. The successful identification and characterization of YOs will spearhead future research on understanding its role in molt regulation of mud crabs, consequently contributing to the development and progress of crab culture and soft-shell crab industries.
Sex pheromonal components of the tephritid fruit fly Bactrocera dorsalis (Hendel), 2-allyl-4,5-dimethoxyphenol and (E)-coniferyl alcohol, are biosynthesized from a highly potent male attractant, methyl eugenol, then sequestered and stored in the rectal gland prior to their release during courtship at dusk. These sex pheromonal components have been detected in the haemolymph and crop organ. Hence, attempts were made to separate and identify the haemolymph fractions which contained the sex pheromonal components. Identification of these bioactive fractions in methyl eugenol-fed male flies using gel filtration column chromatography and biodetection using live male flies showed two fractions as highly attractive to conspecific males. These fractions show a significant increase in protein absorbance in the elution profile of haemolymph from methyl eugenol-fed males compared with that from methyl eugenol-deprived males. The molecular mass of these bioactive fractions as determined by using gel filtration was in the peptide range of 3.3 to 5.5 kDa. Subsequent gas chromatography-mass spectrometry analyses further confirmed the presence of the pheromonal components in the bioactive fractions. The presence of these methyl eugenol-derived sex pheromonal components in specific haemolymph fractions suggests the involvement of a sex pheromone binding complex.
Pharmacophagy of methyl eugenol (ME)--a highly potent male attractant, by Bactrocera papayae results in the hydroxylation of ME to sex pheromonal components, 2-ally-4,5-dimethoxyphenol (DMP) and (E)-coniferyl alcohol (CF). These compounds, which are also male attractants, are then sequestered and stored in the rectal gland prior to their release during courtship at dusk. Chemical analyses of the digestive tract (excluding the crop and rectal gland) showed the absence of the sex pheromonal components and their precursor, ME. However, B. papayae males were attracted to and fed on the ME-fed male hemolymph extracts but not on hemolymph extracts of ME-deprived males. After thin layer chromatography in a hexane:ethyl acetate solvent system, flies were attracted to and fed on the original point on the TLC plate where the hemolymph extract had been spotted, suggesting that the pheromone components were bound in polar complexes. Chemical analyses of the ME-fed male hemolymph and crop extracts revealed the presence of the sex pheromonal components. The presence of the ME-derived pheromonal components and the absence of ME in the hemolymph suggest that the hemolymph is involved in the transportation of sex pheromonal components from the crop to the rectal gland.