Excretion and ultrastructure of the antennal gland of the fiddler crab Uca mordax

Abstract

Function and ultrastructure of the excretory organs (antennal glands) of the shore crab U c a m o r d a x were investigated. The crabs were maintained at three different salinities: 50%, 100% and 200% seawater. In spite of previous reports to the contrary, the investigation showed that the powerful osmoregulatory ability found in Uca m o r d a x is not due to participation of the antennal glands. Freezing point depression of urine under all conditions was found to be slightly less than that of the hemolymph, indicating a slightly hypoosmotic urine. It was further found that the antennal gland is extremely effective in resorbing sodium from the filtrate. The higher the salinity to which the crabs were acclimated the lower the sodium concentration in the urine. No water was resorbed from the filtrate as shown by the fact that the inulin U / P ratio remained unity regardless of the salinity to which the crabs were adapted. Electronmicroscopy of the antennal glands revealed that the coelomosac cells are similar to the podocytes described in the crayfish by Kummel ('64), and the coelomosac appears to be a typical filtration organ. The cells of the labyrinth showed brush border and very elaborate basal infoldings with numerous mitochondria. The deep cytoplasmic infoldings which represent interdigitations with neighboring cells may be correlated with the effective sodium reabsorption in the labyrinth, but apparently not with water movement.The combination of physiologic with electron microscopic investigations have become increasingly important in the current attempts to understand how solutes and water are transported across biological membranes. The purpose of the present investigation was to compare the structuralfunctional relationship of the excretory organ, the antennal gland, of a shore crab, Uca, with that of the excretory organs of other invertebrates and vertebrates. Uca, and other shore crabs were of particular interest mainly because of the claim that the urine, under certain conditions was hyperosmotic to the hemolymph. Riegel and Lockwood ('61), found that the urine osmolality of Carcinus maenas exceeded the hemolymph osmolality by about 3% after four days of dehydration. In Uca p u g n a x the urine osmolality was 10 to 20% higher than the hemolymph when the crabs had been exposed for 2 to 3 days to 100 or 175% seawater (Green et al., '59). The fiddler crab Uca. mordax was selected for the present study, because it lives in salt pools in which the salinity for several months of the year is 2 to 3 times the salinity of seawater. Therefore it seemed J. MORPH., 125: 473-496. that if relatives of Uca mordax were able to produce a hyperosmotic urine, this animal should be at least as effective.Each of the paired antennal glands of the crabs consists of a coelomosac followed by a labyrinth, or single tubule which leads into the bladder ( fig. 1 ) . In the crayfish a nephridial canal is found between the labyrinth and the bladder. According to Grobben (1880) a nephridial canal is present only in fres...

Adaptation of the black tiger shrimp, Penaeus monodon, to different salinities through an excretory function of the antennal gland

“…Negative control shows no specific staining (d). Bars 80 µm structurally comparable with those found in mammalian kidneys, which function during the filtration of serum (Schmidt-Nielsen et al 1968). Therefore, the morphological changes of the antennal gland in shrimps reared in 7 ppt salinity would enhance the tubular filtration function that is involved in the regulation of hemolymphatic osmolarity (Lin et al 2000).…”

“…Labyrinth cells in the antennal glands are structurally and functionally comparable with the epithelial cells lining renal tubules in vertebrates, cells that are known to play a key role in the reabsorption of water and Na + ions through the regulation of ATP-dependent Na + /K + -ATPase activity (Schmidt-Nielsen et al 1968;Peterson and Loizzi 1974). Structural changes of the labyrinth cells including an increase in basal membrane infolding and numbers of mitochondria in the basal striation ( Fig.…”

“…2d-f); these processes contacted each other via a slit membrane (Fig. 2d-f, arrows), a feature resembling the pedicles of podocytes in the kidney of vertebrates (Schmidt-Nielsen et al 1968). …”

Function-Related Structural Characters and Their Modifications in the Hindgut Epithelium of Two Terrestrial Isopods, <i>Armadillidium vulgare </i>and <i>Oniscus asellus</i>

“…Since the studies of Sjostrand and Rhodin [34] and Pease [28,29], it is now gen erally accepted that many cells which engage in intensive transport activity have exten sively infolded plasma membranes which are intimately associated with mitochondria. These specializations, which are found in iso pod hindgut cells, are very evident in the anal papillae of the mosquito larvae [5], in maxil lary and green glands of crustaceans [32,39], the rectal papillae of the blowfly Calliphora [15], the mammalian kidney proximal tubule [34] and the gallbladder epithelium [38].…”

Ecophenotypic physiology: osmoregulation by fiddler crabs (Ucaspp.) from the northern Caribbean in relation to ecological distribution

“…In subtropical, semiarid south Texas, Uca subcylindrica was found to be an exceptional osmoregulator over a range of 3100 mosmol (Rabalais and Cameron 1985). In the Caribbean, Uca mordax (Smith, 1870) from Jamaica (Schmidt-Nielsen et al 1968) and Uca speciosa (Ives, 1891) from Curac¸ao (Spaargaren 1975) were also reported to be excellent regulators. Unfortunately, the identity of the species used in the latter is questionable since we now realize neither is likely to occur at those locations (Barnwell 1986).…”