Uca pugilator

About: Uca pugilator is a research topic. Over the lifetime, 376 publications have been published within this topic receiving 12303 citations.

Circadian rhythm of distal retinal pigment migration in the fiddler crab, Uca Pugilator, maintained in constant darkness and its endocrine control∗∗

Abstract: The distal retinal pigment in the fiddler crab, Uca pugilator, displays a circadian rhythm in constant darkness. The pigment approaches the fully light adapted position by day and the fully dark adapted position by night. This rhythm is presumably due at least to rhythmical release by day of a distal retinal pigment light‐adapting hormone. Extracts of eyestalks from Uca produce a light‐adaptational response in the crab, but extracts of eyestalks from the prawn, Palaemonetes vulgaris, do not produce a light‐adaptational response in the crab, but a dark‐adaptational response instead. In contrast, both types of extract produce a light‐adaptational response of the distal retinal pigment in Palaemonetes. The possibility of a species specificity in the action of distal retinal pigment light‐adapting hormones in crustaceans is discussed.

Further evidence for norepinephrine as a neurotransmitter stimulating release of melanin-dispersing hormone in the fiddler crab, Uca pugilator: the changes in the melanophores of the crabs following reserpine, 6-hydroxydopamine and bretylium administration.

Abstract: 1. 1. The effects on the melanophores of the fiddler crab, Uca pugilator, of the amine depletor reserpine, the catecholamine neurotoxin 6-hydroxydopamine and the noradrenergic neuron blocker bretylium were investigated. 2. 2. The most striking effect of these drugs was that they strongly reduced the amount of melanin dispersion that normally results on transferring the crabs from a white to a black background. The drugs had no effect on pigment migration in melanophores of isolated legs. These results are in accord with the hypothesis that norepinephrine serves as a neurotransmitter stimulating release of a melanin-dispersing hormone in Uca pugilator. 3. 3. Norepinephrine was found in the central nervous system of Uca pugilator.

Relative Effectiveness of Ultraviolet and Visible Light in Eliciting Pigment Dispersion in Melanophores of the Fiddler Crab, Uca pugilator, through the Secondary Response

Abstract: Adaptive color changes in animals have been the subject of a large number of investigations. One genus that has been extensively studied is the fiddler crab, Uca (Fingerman 1968). The effects of light, temperature, and hormones on the chromatophores of this animal have been successfully described and analyzed. However, incident radiation can elicit chromatophore responses in Uca in two ways (Brown and Sandeen 1948). One is the direct action of light on the chromatophores (primary response). The other effect (secondary response) is an indirect one caused by light entering the eyes of the animal and ultimately resulting in secretion of neurohormones that affect the crab's chromatophores. Background responses of Uca are typical secondary responses (Brown and Hines 1952). In a previous publication (Coohill, Bartell, and Fingerman 1970), it was shown that wavelengths in the nearultraviolet (300-400 nm) region of the spectrum could elicit a primary (melanin-dispersing) response in Uca pugilator. This light region is, in fact, 200 times more efficient in eliciting melanin dispersion in this crab than is visible light. It was possible in this case to obtain accurate measurements of the incident dose of near ultraviolet required to elicit a certain response level in the melanophores. We calculated that there was enough near-ultraviolet l ght in the solar spectrum to produce the same response in the natural setting as observed under laboratory conditions. The adaptive value of this response was discussed. This result differe from those obtained with the amphibian, Xenopus laevis, where visible light was more effective than near ultraviolet for the melanophore primary response (Van der Lek 1967). The results of Yoshida (1956, 1957) on the primary response of the sea urchin, Diadema setosum, are ambiguous in that a peak of sensitivity was found in the blue region of the spectrum, but no attempt was made to expose these chromatophores to near-ultraviolet light. The only investigation dealing with the direct spectral response of crustacean chromatophores, other than that of Coohill et al. (1970), is that of Pau sch (1953), who, using the shrimp, Crangon crangon, obtained maximum pigment dispersion when the illumination was in the region of 300-450 nm. The objective of the present investigation was to compare the relative efficiences of ultraviolet and visible light in inducing melanin dispersion in the fiddler crab, Uca pugilator, by means

Primary Structure and Relative Potency of an Analog of β-PDH (Pigment-Dispersing Hormone) From the Crayfish Procambarus clarkii

Abstract: A pigment-dispersing hormone (PDH) from eyestalks of the crayfish Procambarus clarkii was purified by gel filtration, cation-exchange chromatography, partition chromatography, and reversed-phase HPLC. Based on automated sequencing and by the identical chromatographic behavior of the native PDH and the synthetic amidated form of the deduced sequence, the primary structure of Procambarus PDH has been established as: Asn-Ser-Glu-Leu-Ile-Asn-Ser-Ile-Leu-Gly-Leu-Pro-Lys-Val-Met-Asn-Glu-Ala- NH2. This peptide differs from beta-PDH of the fiddler crab Uca pugilator at a single position, Glu17 in place of Asp17. Because of this substitution, Procambarus PDH was 4 to 7-fold less potent than beta-PDH in causing pigment dispersion in the erythrophores, leucophores, and melanophores of Uca. In contrast, Procambarus PDH was 4-fold more potent than beta-PDH in eliciting pigment dispersion in the erythrophores of Procambarus. These peptides displayed less marked differences in potency in triggering leucophore pigment dispersion and light-adaptational distal eye pigment movement in Procambarus. These findings indicate that the structural requirements for PDH-receptor interactions vary with the species and with the target cell type within a given species.

Comparative aspects of the chromatophoric responses to light and temperature in fiddler crabs of the genus uca

Abstract: Fiddler crabs undergo a variety of physiological color changes in their natural habitat (Crane, 1944). These alterations in shade and hue are produced by the concentration and dispersion of pigments within a well developed system of chro matophores. Although several aspects of color change in fiddler crabs have been examined in detail, few experimental studies have dealt with its biological sig nificance. In only one species, Uca pugilator (Bosc), has there been a systematic investigation of the chromatophoric responses to light intensity, shade of back ground, and temperature with a discussion of their possible functional roles (Brown and Sandeen, 1948). In view of the extensive adaptive radiation and the diversity of coloration within the genus (Crane, 1941), it is of interest to learn to what extent the findings with Uca pugilator niay apply to other species. In this paper some chroniatophoric responses to light and temperature are described in two tropical species from Costa Rica, Uca galapagensis herradurensis (Bott) and Uca .@acae (Crane), aiid a temperate species, Uca pugnax (Smith). The results are then compared with the earlier findings on Uca pugilator.