The Y-organ secretory activity fluctuates in relation to seasons of molt and reproduction in the brachyuran crab, Metopograpsus messor (Grapsidae): Ultrastructural and immunohistochemical study (original) (raw)
Zoological studies
Hemolymph ecdysteroid titers in a brachyuran crab Uca triangularis that concomitantly undergoes molting and reproduction. Zoological Studies 51(7): 966-976. Investigations conducted thus far suggest that premolt growth and ovarian growth are antagonistic events in brachyuran crabs, arguably implying that yolk deposition does not occur during premolt when the ecdysteroid titer is very high. The present paper examines ecdysteroid levels in a brachyuran crab Uca triangularis that exhibits simultaneous programming of premolt growth and reproduction during certain seasons of the year. The species exhibits 2 patterns of breeding cycles, 1 (premolt breeding cycle) synchronous with the premolt cycle during Feb.-May, and the other (intermolt breeding cycle) taking place only during intermolt (Aug.-Jan.); no breeding activity occurs during June-July. Results depicted in the present paper are also expected to help us evaluate the possible role of ecdysteroids in reproduction in crustaceans, a ...
Zoological Studies, 2014
Background Mandibular organ (MO) in decapods is suggested to play regulatory role in reproduction, in few species; however, MO is considered to control growth. The present study addresses this question by an ultrastructural study on the MO of the field crab, Paratelphusa sp. Our sampling for consecutive years (2008 to 2012) revealed that Paratelphusa sp. devotes July to October for reproduction, judged by the occurrence of growing ovaries and the berried females. From November to the succeeding June, the females are in a state of reproductive arrest (non-reproductive period); ovaries during this season would appear as white bands with no signs of yolk deposition. Results Morphologically, MO of Paratelphusa sp. is positioned posterior to the mandibles and is in close apposition with the distal end of the mandibular apodeme. MO of Paratelphusa sp. exhibited significant levels (t = 8.097, P
Metopograpsus messor, a brachyuran crab inhabiting the estuaries of North Kerala (India), is a prolific breeder releasing approximately 14-16 broods a year. The present paper reports the sequence information on the DNA binding domain (C domain, DBD), linker (D domain) and ligand binding domain (E domain, LBD) of M. messor ecdysteroid receptor (MmEcR) gene, the first grapsid brachyuran crab EcR examined. We have also measured MmEcR transcript levels in the ovary and the hepatopancreas throughout the annual cycle, with special reference to seasons of molt and reproduction. MmEcR expression in both the tissues is found to be at its peak (P < 0.05) in late premolt crabs (January/May, molt/reproduction season); the expression levels are lowest (P < 0.05) during June/July, when the females would neither molt nor reproduce (season for molt/reproduction repose). Intermediate levels of expression were found during the breeding season (August/December). Interestingly, this pattern of gene expression is in concordance with the fluctuating ecdysteroid levels of the hemolymph and Y organ secretory activity. The significant levels of fluctuation in the ovarian expression of MmEcR strongly suggest the ovary as a potential target for ecdysteroid action. A season-wise comparison of the gene expression reveals that ovarian MmEcR transcript levels are higher in breeding crabs (August/December) than the non-breeding animals (June/July), implicating a possible ecdysteroid role in reproduction in M. messor.
Effect of moult-inhibiting hormone on ketodiol conversion by crab Y-organs
Journal of Insect Physiology, 1988
Ketodiol incubated in vitro witli &minus mamas Y-organs, is converted into three molecules 22,25-dideoxyecdysone, 25deoxyecdysone and ecdysone. Two of these three products (25deoxyecdysone and ecdysone) are secreted into the medium and are possible precursors of ponasterone A and 20-hydroxyecdysone respectively, the major haemolymph ecdysteroids. The ratio of ecdysone to 25-deoxyecdysone varies during the moulting cycle of the animal; no conversion occurs in intermoult crabs (C4), in premoult crabs (Dl), 25-deoxyecdysone is the predominant ketodiol metabolite whereas in crabs in the stage DO (apolysis period) the predominant metabolite is ecdysone. The regulation of ecdysteroid synthesis is achieved by moult-inhibiting hormone stored and released by the sinus glands. The sinus gland extracts and purified moult-inhibiting hormone were tested for their effect on ketodiol conversion by crab Y-organs. The effects of the sinus gland extract or moult-inhibiting hormone on synthesis of ecdysone and 25-deoxyecdysone depend on the moulting stage. In crabs in which 2%deoxyecdysone is the predominant metabolite, sinus gland extracts of the hormone inhibit ketodiol conversion into 25-deoxyecdysone and, at higher concentration, its conversion into ecdysone. In crabs in which ecdysone is the predominant compound, its level decreases as the concentration of sinus gland extract or moult-inhibiting hormone is increased.
General and Comparative Endocrinology, 1998
In the fiddler crab, Uca pugilator, we have investigated the temporal expression of receptors in various tissues using probes that encode Uca ecdysteroid receptor (UpEcR) and retinoid-X-receptor (UpRXR) gene homologs. During molt stages C 4 through D 1-4 , UpEcR and UpRXR transcripts are expressed in regenerating limb buds, gills, eyestalks, hypodermis, hepatopancreas, muscle from nonregenerating walking legs, and the large cheliped. Some of these tissues have not previously been recognized as ecdysteroid-target tissues. Levels of ecdysteroids in the hemolymph fluctuate significantly during the molt cycle of U. pugilator. The variation in steadystate concentrations of UpEcR transcripts in tissues from C 4 to D 1-4 implies molt cycle-related differences in the potential of these tissues to respond to changing titers of ecdysteroids in the hemolymph. In singly autotomized crabs, highest concentrations of UpEcR transcript in some tissues did not coincide with the highest levels of circulating ecdysteroids, suggesting that UpEcR expression in these tissues is not dependent on high ecdysteroid titers and may be induced by low or rising concentrations of ecdysteroids. UpEcR and UpRXR genes were expressed simultaneously in tissues, supporting the possibility of heterodimerization for EcR and RXR in vivo. In some tissues, however, levels of transcripts differed, suggesting other possible receptor interactions. Moreover, UpEcR expression in tissues from multiply autotomized crabs differed from the expression patterns in tissues from singly autotomized crabs. 1998 Academic Press General and Comparative Endocrinology 109, 375-389 (1998) Article No. GC977046 375
Cell & Tissue Research, 1992
The sinus gland of the shore crab, Carcinus maenas, is a compact assembly of interdigitating neurosecretory axon endings abutting upon the thin basal lamina of a central hemolymph lacuna. Four types of axon endings are distinguishable by the size distribution, shape, electron density and core structure of their neurosecretory granules. One additional type of axon ending is characterized by electron-lucent vacuoles and vesicles. The axon profiles are surrounded by astrocyte-like glial cells. Various fixations followed by epoxy-or Lowicrylembedding were compared in order to optimize the preservation of the fine structure of the granule types and the antigenicity of their peptide hormone contents. By use of specific rabbit antisera, the crustacean hyperglycemic, molt-inhibiting, pigment-dispersing, and red-pigment-concentrating hormones were assigned to the four distinct granule types which Showed no overlap of immunostaining. Epi-polarization microscopy and ultrathin section analysis of immunogold-stained Lowicrylembedded specimens revealed that immunoreactivity to Leu-enkephalin and proctolin is co-localized with moltinhibiting hormone immunoreactivity in the same type of granule. The size and core structure of the immunocytochemically identified granule types vary little with the different pretreatments but, in some cases, to a statistically significant extent. The present results are compared with those from earlier studies of sinus glands in different crustaceans. The methods of granule identification used in this study supplement the classical approach in granule typing; they are easier to perform and more reliable for the analysis of release phenomena in identified secretory neurons supplying the neurohemal sinus gland.
We studied the anatomy and cytology of the midgut gland (MGl) of the common spider crab Maja brachydactyla Balss, 1922 at several life stages (zoea, megalopa, first juvenile, and adult) using dissection, histology, electron microscopy, computed tomography, and micro-computed tomography (micro-CT). In newly hatched larvae, 14 blind-end tubules form the MGl. The length of the tubules increases during the larval development. In the late megalopa, the number of tubules also increases. In adults, 35,000 to 60,000 blind-ending tubules comprise the MGl. In all life stages, a square-net network of muscle fibers surround the tubules. We describe five cell types in the MGl in all larval stages, which have a similar location, histology, and ultrastructure in larvae and adults: embryonary (E-) cells, resorptive (R-) cells, fibrillar (F-) cells, blister-like (B-) cells, and midget (M-) cells. Major difference between larval and adult cells is the larger size of the adult cells. Microapocrine secretion occurs from the microvilli of the B-cells. No ultrastructural changes were observed during larval development, which suggests that the function of each cell type might be similar in all life stages. The role of each epithelial cell type in larvae and adults is discussed.