Milton Fingerman

Crustacean endocrinology: a retrospective, prospective, and introspective analysis.

From the first discovery of a hormone in a crustacean in the 1920s until the present, the field of crustacean endocrinology has undergone, as do many crustaceans during their development, a marked metamorphosis. The field has moved from the classical era of endocrinological techniques, such as extirpation and additive methods, to the modern era of sophisticated biochemistry and molecular biology. As new investigatory techniques have been devised, crustacean endocrinologists have quickly adopted them and, as a consequence, have made major advances. Nevertheless, there is still much room (and need) for the older techniques, particularly because there is still a vast gap in our knowledge of the endocrine mechanisms of the less highly evolved crustaceans. The bulk of the information we have about crustacean endocrinology has been derived from studies of decapods. Crustacean endocrinology not only provides information about the basic biology of this important group of organisms but also has the potential of greatly enhancing our ability to culture species used as food sources for humans.

HEAT TOLERANCE AND TEMPERATURE RELATIONSHIPS OF THE FIDDLER CRAB, UCA PUGILATOR, WITH REFERENCE TO BODY COLORATION

1. Upper thermal death points were determined for the fiddler crab, Uca pugilator. In saturated air the lethal temperature for 50% of the crabs, determined graphically from the experimental data, after an exposure of one hour, was 40.7° C. All of the crabs died after one hour at 42° C. In dry air the corresponding temperatures were 45.1° C. and 47° C. for the same time of exposure.2. Five minutes after having been placed in sunlight the body temperature of dark crabs was 2° C. higher than that of pale crabs. More visible light is reflected from the dorsal surface of the cephalothorax of a pale crab than from a dark crab. The difference is more striking with the rays of longer wave-length which have a greater heating capacity than the rays at the violet end of the visible spectrum. These observations support the hypothesis that the blanching that occurs at high temperatures has a thermoregulatory role.3. The body temperatures of crabs maintained either in dry air or in air having a relative humidity of 50%...

PERSISTENT DAILY AND TIDAL RHYTHMS OF COLOR CHANGE IN CALLINECTES SAPIDUS

1. The pigment in the melanophores of Callinectes sapidus displays an endogenous diurnal rhythm with a frequency of 24.0 hours. The pigment is in the dispersed state during the day and in the concentrated state at night.2. The amplitude of the diurnal rhythm neither increases nor decreases under constant laboratory conditions.3. Superimposed upon the diurnal rhythm is a tidal rhythm with a frenquency of 12.4 hours. This rhythm is manifested by a supplementary dispersion of the melanin which occurs about fifty minutes later each day.4. The tidal rhythm is most evident when the low or high tide is either in the morning or late afternoon. When either a low tide or a high tide occurs at these times, the diurnal rhythm curve is skewed to the left or right or tends to be bimodal, depending upon the times of high and low tides. There is no difference of response to low and high tides.5. The tidal rhythm of Callinectes maintained under constant laboratory condititions has its phases bearing a definite relationshi...

Neuroendocrine Control of the Hepatopancreas in the Crayfish Procambarus clarki

T HE crustacean hepatopancreas is involved in secretion of the digestive juice, absorption of digested food, and storage (Vonk, 1960). Earlier investigators (Jordan, 1927; Kriiger and Graetz, 1927, 1928; Wiersma and van der Veen, 1928; Vonk, 1935) have described the enzymatic activities of the digestive juice, pH and temperature optima of the enzymes, and changes in the pH of the digestive juice after feeding. The juice contains enzymes that act on carbohydrates, fats, and proteins. However, only comparatively recently has attention been turned to the possible role of neuroendocrine substances in regulating the activity of the crustacean hepatopancreas. Yamamoto (1953, 1960a, b) found that removal of both eyestalks from the crayfish Procambarus clarki results in degenerative changes within the hepatopancreas as observed histologically For example, pycnosis was obvious 10 days after the operation. Implants of the contents of the eyestalk or of the sinus gland alone from the eyestalk retarded the degeneration. By histochemical means, Miyawaki, Matsuzaki, and Sasaki (1961) demonstrated the presence of ribonucleic acid (RNA) in the hepatopancreas of P. clarki. Miyawaki and Tanoue (1962), through elec-

REGULATION OF THE RELEASE OF CHROMATOPHOROTROPIC NEUROHORMONES FROM THE ISOLATED EYESTALK OF THE FIDDLER CRAB, UCA PUGILATOR

Electrical stimulation of the isolated eyestalk of Uca pugilator induces the release of several peptides which affect epidermal chromatophores. Thresholds for release of these peptides were different, that for red pigment concentrating hormone (RPCH) being lowest, for black pigment dispersing hormone (BPDH) highest, and for black pigment concentrating hormone (BPCH) intermediate, but no red pigment dispersing hormone(RPDH) was detected at any voltage. Neurotransmitters, known to be present in crustacean central nervous systems, induced chromatophore dose dependent responses. Norepinephrine induced BPDH release, and dopamine induced both RPCH and BPCH release.

HORMONAL REGULATION OF THE DISTAL RETINAL PIGMENT OF PALAEMONETES

1. After removal of one eyestalk the distal pigment of the intact eye of Palaemonetes light-adapts more slowly and to a less extent for a given illumination; dark-adaptation is unaffected.2. The eyestalks are the chief sources of light-adapting hormone; lesser amounts are found in brain, connectives and ventral ganglia.3. The eyestalks and central nervous organs are sources of dark-adapting hormone. The tritocerebral commissure possesses dark-adapting, but no light-adapting hormone.4. Both light- and dark-adapting hormones can be elaborated and stored, to be discharged in quantity upon appropriate stimulation.5. Light-adapting hormone is elaborated and stored during a few hours in darkness; no store appears to be present in prawns kept in light.6. Dark-adapting hormone appears to be stored in animals in light; following transfer to darkness, the store is depleted but the capacity to re-dark-adapt following response to a brief light flash gradually increases during a few hours in darkness.

Relative Effectiveness of Ultraviolet and Visible Light in Eliciting Pigment Dispersion Directly in Melanophores of the Fiddler Crab, UCA Pugilator

The direct responses of chromatophores to light stimuli have been observed in a wide diversity of organisms (Fingerman 1963; Van der Lek 1967). With very few exceptions, pigment dispersion occurs in bright light (visible and ultraviolet) and pigment concentration in darkness. For example, when melanophores of eyestalkless fiddler crabs Uca pugilator were exposed to sunlight, pigment dispersion occurred as a direct response to the illumination (Brown and Sandeen 1948). However, the relative spectral efficiency of this response is not known. As in the fiddler crab, bright illumination also causes pigment dispersion to occur in the chromatophores of the sea urchin Diadema setosum (Yoshida 1956). Using visible light alone, Yoshida (1957) reported a peak effectiveness for pigment dispersion in this sea urchin in the region 450-500 mnt. Van der Lek (1967) determined the spectral sensitivity of the fin melanophores in isolated tails of the amphibian Xenopus laevis. The pigment in these melanophores atypically concentrates when they are illuminated. With visible light, the wavelength of maximal sensitivity was 425 mp. Van der Lek also obtained

Quantitative Analysis by Reverse Phase High Performance Liquid Chromatography of 5-Hydroxytryptamine in the Central Nervous System of the Red Swamp Crayfish, Procambarus clarkii

The concentrations of 5-hydroxytryptamine (5-HT) in central nervous organs of the red swamp crayfish, Procambarus clarkii, were determined by reverse phase high performance liquid chromatography (RPHPLC) with electrochemical detection. The quantity ranged between 54 and 168 pg/mg wet weight of tissue. The amount is highest in the brain, followed in decreasing order by the thoracic ganglia, subesophageal ganglion, eyestalks, and abdominal nerve cord. Significant increases in the levels of 5-HT in the eyestalks, brain, subesophageal ganglion, and thoracic ganglia occurred in crayfish exposed for three days to continuous light on a white background, whereas the 5-HT levels in these tissues decreased in crayfish kept in darkness. Electrical stimulation of central nervous organs in vitro produced significant decreases in the levels of 5-HT. Fenfluramine (5-HT releaser), 5,6-DHT (5-HT neurotoxin), and reserpine (5-HT depletor) induced significant decreases in the 5-HT levels in the portions of the central nervous system tested.

THE ROLES OF HEMOCYTES IN TANNING DURING THE MOLTING CYCLE: A HISTOCHEMICAL STUDY OF THE FIDDLER CRAB, UCA PUGILATOR

Histochemical data support the previous biochemical finding that the blood is a major site for the production of proteinaceous and diphenolic substances for tanning of the cuticle in the fiddler crab, Uca pugilator. Five types of hemocytes are described. Specifically in tanning, the hyaline cells (cystocytes) appear responsible for the production of diphenolic tanning agents whereas the granulocytes synthesize the proteins involved. Other types of hemocyte may be transitional forms involved in clotting (intermediate cells). Various histochemical reactions for each type of hemocyte and the cuticle are recorded throughout the molting cycle, and appear cyclic. The data suggest there is hormonal control of the cyclic events during the tanning process.

A STUDY OF THE MECHANISM INVOLVED IN SHIFTING OF THE PHASES OF THE ENDOGENOUS DAILY RHYTHM BY LIGHT STIMULI

1. A study was made of the mechanism of reversal of phases of the persistent daily rhythm in the fiddler crab, Uca pugnax, by illumination by night and darkness by day.2. Fiddler crabs were subjected to a series of combinations of brighter illumination by night and dimmer illumination by day.3. A graded series of amount of shift was obtained which was capable of being interpreted in terms of two operating factors: (a) the strength of the stimulus in the form of the dark to light change, and (b) the absolute brightness of the higher illumination.4. An hypothesis is advanced which appears to account adequately for all currently known characteristics of the mechanism of persistent shift in phases of the daily rhythm by light stimuli.