K. Ranga Rao

Effects of exogenous ecdysones on the molt cycles of fourth and fifth stage american lobsters, Homarus americanus

Abstract 1. 1. Bilateral ablation of the eystalks of the lobster, Homarus americanus, results in the acceleration of proecdysial preparations and precocious initiation of ecdysis. 2. 2. Injection of either α-ecdysone or 20-hydroxyecdysone into fourth stage lobsters in stage D0 of the molt cycle accelerated proecdysial preparations and led to precocious initiation of ecdysis. 3. 3. Lobsters which initiated precocious ecdysis in response to 20-hydroxyecdysone died during the initial stage of ecdysis (E1) whereas the α-ecdysone-injected lobsters either completed ecdysis successfully or died in the later stages of ecdysis (E2 or E3). 4. 4. α-Ecdysone was ineffective in inducing proecdysis and shortening the molt cycle in fifth stage lobsters when injected during early postecdysial stages but was effective when injected late in the intermolt stage and in early proecdysis (D0).

Action of biogenic amines on crustacean chromatophores, II. Analysis of the responses of erythrophores in the fildler crab, Uca pugilator, to indolealkylamines and an eyestalk hormone☆

Abstract 1. 1. The effects of injection of certain indolealkylamines on the erythrophores of the fiddler crab, Uca pugilator , were determined. 2. 2. Among the compounds tested only those which possess a free 5-hydroxy group on the indole nucleus evoked dispersion of the red chromatophoric pigment after injection into eyestalkless Uca pugilator . 3. 3. Serotonin which was very effective in vivo failed to evoke pigment dispersion when assayed in vitro on the erythrophores in legs isolated from Uca . In contrast, red pigment-dispersing hormone from the eyestalks of Uca stimulated the erythrophores in vitro as well as in vivo . 4. 4. UML (1-methyl lysergic acid butanolamide) antagonized the action of serotonin in vivo , but was without effect on hormonally induced dispersion of the red pigment. 5. 5. Injection of serotonin resulted in a marked decrease in the red pigment-dispersing potency of the supra-oesophageal ganglia and the attached circumoesophageal connectives of the recipients. 6. 6. It is concluded that serotonin acts primarily on the central nervous system to stimulate the release of a red pigment-dispersing hormone, whereas the red pigment-dispersing hormone stimulates the erythrophores directly.

A female-limited lipoprotein and the diversity of hemocyanin components in the dimorphic variants of the fiddler crab, Uca pugilator, as revealed by disc electrophoresis

Abstract 1. 1. A female-limited lipoprotein is found in the hemolymph of only those individuals with maturing oocytes. The relative concentration of the lipoprotein in the ovary increases progressively with oocyte maturation. 2. 2. There is no difference between the electrophoretic patterns of hemocyanin from males and females. 3. 3. The electrophoretic pattern of the hemocyanin components is not the same in the two morphological variants of the fiddler crab, Uca pugilator. After electrophoresis of hemolymph from the light patch variant of Uca pugilator four hemocyanin components are seen whereas only three components are seen in the hemolymph from the dark patch variant.

Comparison of the abilities of ?-ecdysone and 20-hydroxyecdysone to induce precocious proecdysis and ecdysis in the fiddler crab, Uca pugilator

Summary1.The effects of single, double or multiple injections of α-ecdysone and 20-hydroxyecdysone on molting and limb regeneration in the fiddler crab, Uca pugilator, were determined.2.A single injection of 12 μg of 20-hydroxyecdysone failed to initiate proecdysis in crabs weighing 1.2 to 1.6 g. Administration of 12, 5, and 5 μg of 20-hydroxyecdysone on Days 0, 3, and 6 respectively induced precocious initiation of proecdysis but not precocious ecdysis. However, when two large dosages (20 or 25 μg) of 20-hydroxyecdysone were injected within a period of one or two days all the crabs completed proecdysis and initiated ecdysis precociously but failed to complete the ecdysis and died.3.Administration of 25 μg of α-ecdysone as a single injection failed to initiate precocious proecdysis. However, when two injections of 25 μg each were given 36% of the crabs completed proecdysis and successfully molted precociously. Injection of larger dosages (80 μg α-ecdysone either as four 20 μg injections or two 40 μg injections) induced precocious proecdysis and ecdysis in 75–86% of the crabs. In contrast to the crabs which died during ecdysis after receiving high dosages of 20-hydroxyecdysone, the recipients of α-ecdysone underwent successful ecdysis and their postecdysial survival was normal.4.The response of the regenerating limb buds depended on the dosage of the ecdysones administered. Dosages of 20-hydroxyecdysone which failed to initiate proecdysis promoted basal limb growth. Stronger dosages of 20-hydroxyecdysone and α-ecdysone which induced precocious proecdysis and ecdysis accelerated limb growth and caused proecdysial limb growth. The slope of the growth curve obtained for the crabs injected with high dosages of ecdysones was much steeper than that for eyestalkless crabs.5.The interrelationship between regenerative limb growth and proecdysis and the possible role of ecdysones in the control of proecdysial events in crustaceans are discussed.

Action of biogenic amines on crustacean chromatophores. 3. Antagonism by lysergic acid diethylamide of the effect of serotonin on colour changes in the fiddler crab, Uca pugilator.

Abstract 1. 1. Lysergic acid diethylamide (LSD) evokes strong concentration of the erythrophoric pigment in intact fiddler crabs, Uca pugilator, but does not evoke pigment concentration in the erythrophores of eyestalkless crabs or legs isolated from intact crabs. 2. 2. LSD has no effect on maximally concentrated erythrophoric pigment. 3. 3. LSD inhibits the red pigment dispersing action of serotonin (5-hydroxytryptamine), but does not antagonize the action of red pigment dispersing hormone from the eyestalk. 4. 4. LSD does not stimulate the erythrophores directly; its action is mediated by the neuroendocrine system in the crab.

Control of distal retinal pigment migration in the fiddler crab Uca pugilator

Several concentrations of extracts prepared from the eyestalks of a specimen of Uca pugilator were injected into other U. pugilator individuals. The distal pigment of the eyes first became light adapted and then dark adapted, the whole process lasting 6 h. The mean integrated response for light adaptation increased progressively up to the highest tested extract (3 eyestalk equivalents/dose), but with the darkadapting response the maximal effect was produced by the extract containing 2 eyestalk equivalents/dose. Gel filtration of eyestalk extracts in Sephadex G-50 showed that the fractions associated with greatest light adaptation were also associated with greatest pigment dispersion in the melanophores. Almost no light or dark adaptation of the retinal pigment resulted from injections of eyestalk extracts treated with α-chymotrypsin which supports the interpretation that these substances are polypeptides of neurosecretory origin.

Comparison of the melanin-dispersing fractions in extracts prepared initially in ethanol, saline or distilled water from eyestalks of the fiddler crab, Uca pugilator

Abstract 1. 1. Dosages above 0·3 eyestalk equivalent of the ethanol-soluble fraction of eyestalks evoke much more prolonged melanin-dispersing responses than do extracts prepared directly in saline. 2. 2. The high activity of the ethanol-soluble fraction is due to a micellar lipoprotein with a melanophorotropic polypeptide component. 3. 3. Both vigorous stirring and lyophilization of the ethanol-soluble fraction dissociate the active polypeptide from the lipoprotein. Dissociation is accompanied by reduction in activity. The high activity seems due to slow release of the polypeptide from the lipoprotein. 4. 4. It is postulated that the lipoprotein serves as a carrier for the polypeptide within neurosecretory cells and possibly in the blood.

Relationship between the response of melanophores in the fiddler crab, Uca pugilator, and the concentration of eyestalk extract

Summary1.Eyestalks from the fiddler crab, Uca pugilator, were extracted directly in either water or absolute ethyl alcohol. Dosage-response curves for these extracts were then determined.2.The melanin-dispersing response produced by the alcohol soluble material increased sharply with increasing concentration of the extract between 1 and 80 eyestalks/ml. In contrast, the dosage-response curves for the extracts prepared directly in water did not rise at all as sharply as did that of the alcohol extract.3.A water extract seems to contain a substance which at the higher concentrations antagonized the melanin-dispersing hormone. Elimination of this antagonist by the technique of gel filtration resulted in an increased melanin-dispersing activity.4.The possible action of absolute ethyl alcohol which results in a preparation of melanin-dispersing hormone from the eyestalk that is much more active at higher concentrations than a similar extract prepared in water is discussed.

Solubility and stability properties of the melanin-dispersing substances from the eyestalks of the fiddler crab,Uca pugilator

Summary1.Extracts of fresh, freeze-dried, and heat-dried eyestalks prepared directly in physiological saline evoked nearly identical melanin-dispersing responses. The highly active ethanol-soluble fraction extractable from fresh eyestalks ofUca was to a great extent unextractable after the eyestalks were freeze-dried, heat-dried, or pretreated with a variety of organic solvents, whereas the melanin-dispersing substance in the ethanol-insoluble fraction of the eyestalk was resistant to these treatments. The melanin-dispersing substance obtained by direct extraction of the eyestalk in water is more resistant to treatment with organic solvents than the substance present in the ethanol-soluble fraction.2.The melanin-dispersing activities of the eyestalk material soluble in various solvents showed no overall relationship with the dielectric constants of the solvents used. However, the melanin-dispersing activity was related to the dielectric constants of the normal alcohols used in the following decreasing order: methanol>ethanol>propanol>butanol>amyl alcohol.3.Ether and isopropyl ether destroyed most of the melanin-dispersing material present in the ethanol-soluble and water-soluble fractions of the eyestalk, possibly due to excessive oxidation.4.The melanin-dispersing material in the ethanol-soluble fraction of the eyestalk is greatly destroyed by heat. In contrast, the melanin-dispersing material in the water-soluble fraction of the eyestalk is resistant to heat.5.The possibility that two melanin-dispersing substances are present in the eyestalks ofUca is considered and discussed.

Chromatophorotropic activity of extracts of radial nerves from the starfish, Asterias amurensis

Summary1.Extracts of radial nerves from the starfish, Asterias amurensis, were assayed for chromatophorotropic activity in the fiddler crab, Uca pugilator.2.The radial nerve extracts evoked pigment dispersion in the melanophores and pigment concentration in the leucophores and erythrophores of Uca. Gel filtration studies revealed that the chromatophorotropic material is different from the gamete-shedding substance.3.Like chromatophorotropins in arthropod neural tissues, the chromatophorotropic material in the radial nerves appears to have a peptide nature. Chromatography on Bio-Gel P-6 and analysis of solubility properties indicate that the latter is different from the chromatophorotropins which have been found in crustaceans.4.The possibility that these chromatophorotropic effects were caused by a single substance was discussed.