Eyestalk Removal Research Articles

The hexosemonophosphate pathway and its variation in the intermolt cycle in crayfish

1. 1. Through the use of the inhibitor 5-bromouracil, respirometric measurements, and nucleotide reductions the hexosemonophosphate shunt (HMS) is shown to be active in the hepatopancreas of the crayfish O. virilis during intermolt cycle stage C. The activity of this metabolic pathway was greatest at stage C 3–4 and declined to zero in the later premolt stages. Loss of sensitivity to a pentose shunt inhibitor after eyestalk removal points to the regulation of metabolic routes by eyestalk principles. 2. 2. The amount of glucose-6-phosphate which travels via the HMS in tissue from intermolt animals, as evaluated from utilization of 6-PG by the same tissue, is estimated to be approximately 10 per cent of the available substrate. 3. 3. By measuring triphosphopyridinenucleotide reduction it was shown that there is greater activity in an “incomplete carbohydrate cycle” in tissue from intermolt animals than in that of premolt animals. It is suggested that increased activity of this cycle, with an accompanying decrease in oxygen consumption during intermolt, may provide a biochemical basis for the increase in protein and lipid synthesis which occurs at this time.

The effect of eyestalk extirpation on metamorphosis of megalops of the blue crab, Callinects sapidus Rathbun

One or two eyestalks were removed from the megalops of the crab Callinectes sapidus Rathbun, reared under controlled laboratory conditions, on days 0–5 following the final zoeal molt. Following metamorphosis, the post-larval stages were maintained and measured over 4–6 consecutive molting periods. From these studies the following conclusions may be made: ( 1) Metamorphosis to the first crab stage is accelerated considerably by the extirpation of both eyestalks within 12 hours following the final zoeal molt. Removal of both eyestalks on days 1–5 following the final zoeal molt does not affect metamorphosis. Removal of one eyestalk on day 0 does not affect metamorphosis, but extirpation on days 1–4 significantly delays it. ( 2) Removal of one eyestalk on days 0–5 following the final zoeal molt accelerates some post-larval molts, but the effect is not persistent. Post-larval molting occurs more frequently in crabs which metamorphose from megalops with both eyes removed on day 0 following the final zoeal molt. Crabs which metamorphose from megalops with both eyes removed on days 1–5 do not show any acceleration in post-larval molting frequency. These results are not completely compatible with the current concept which restricts the control of molting to the x organ of the eyestalks and the Y organs. ( 3) Crabs which metamorphose from megalops without both eyestalks show a greater increase in size than crabs of the control series. Even if molting were not accelerated, as in crabs which metamorphosed from megalops with both eyes removed on days 1–5, there is a greater increase in size at the time of molting. Thus, while molting and growth are normally associated, the hormones which control the two processes are not identical. ( 4) Crabs which metamorphosed from megalops with both eyes removed showed a considerably higher mortality than either the crabs with one eye removed or the control crabs. ( 5) The results suggest that endocrines other than the molt-inhibiting hormone of the x organ and the molt-accelerating hormone of the Y organ are involved in both metamorphosis of the megalops and in post-larval molting. Additional evidence is needed to describe the source of these hormones and to define their role in metamorphosis and molting.

Gastrolith growth and calcium shifts in the freshwater crayfish, Orconectes virilis

1. 1. An X-ray study of crayfish ( Osrconetes virilis) induced to molt in the non-molting season demonstrated that calcium deposition in the form of gastrolith is evident 48–72 hr after the opration in the majority of animals. The subsequent growth of the gastrolith continues to the time of actual sheding of the exoskeleton. 2. 2. The time of molt can be estimated by use of a gastrolith-to-carapace relationship which reaches a value of 0.18 to 0.22 at the time of ecdysis for smalla or large animals. 3. 3. Unbound calcium in normal crayfish blood did not change markedly from intermolt to premolt though there is some evidence of a small decrease in this component. Eyestalk removal, which induces gastrolith formation, resulted in a significant decrease in the unbound blood calcium levels of intermolt crayfish with a concomitant increase in the protein-bound fraction. 4. 4. Eyestalk removal from crayfish during the non-molting period results in an increase in blood protein to 65 per cent over the normal intermolt value. The increase in protein plus the increase in calcium bound per milligram of protein accounts for more than a fourfold increase in blood calcium at the onset of premolt. 5. 5. Injection of extracts of premolt eyestalks depressed the blood level of unbound calcium while central nervous system extracts induced a significant increase in this component. These responses are interpreted as evidence for two antagonistic principles with respect to molt regulation, and thus calcium metabolism, in crayfish. 6. 6. Measurement of environmental calcium demonstrated that a population of crayfish studied between the two normal molting seasong undergoes a constant change in calcium release and uptake with, however, a net gain of approximately 2.5 mg/animal in 20 days. Animals in the premolt condition released substantial quantities of calcium to the environment despite its storage in the gastrolith at this time. The loss per animal was approximately 3.5–4.0 mg in 20 days.

Sodium Regulation in the Crayfish Astacus Fluviatilis

ABSTRACT In distilled water or artificial tap water with a very low sodium concentration, sodium uptake by Astacus is prevented or reduced and 22Na outflux is subnormal. This is accounted for to only a small extent by reduced renal sodium losses. Sodium-depleted animals replaced in artificial tap water regain sodium in a roughly exponential manner. This is shown by 22Na to be the result of a considerable increase in sodium influx coupled with an increased but lower outflux. Sodium outfiux appears to consist of three components: urine losses, passive diffusion losses over the body surface and what may be an ‘exchange diffusion’ component which is high during high influx and minimal in distilled water. This latter component represents about 30% of sodium exchange under normal conditions. Eyestalk removal did not affect the ability of Astacus to absorb sodium. In starved animals the gills take up most of the sodium absorbed and the gut is relatively unimportant. Silver staining of the gills is a passive process and the cuticle of the branchial filaments of the gill stem is selectively stained. This region would be a suitable site for ion uptake mechanisms.

LOW TEMPERATURE BLOCKAGE OF MOLTING IN UCA PUGNAX

1. A uniform population of male Uca pugnax was used in studying the effect of 10 temperatures on proecdysis resulting from eyestalk removal.2. Proecdysis duration is shortest at 29° to 32° C. and lengthens significantly at lower temperatures.3. Proecdysis initiation is markedly temperature-sensitive. At 15° or below initiation is completely blocked; at 15° to 20° a substantial proportion of the crabs fail to begin proecdysis.4. Temperatures which block proecdysis initiation also block basal limb bud regeneration (a molt-independent growth process) . It is hypothesized that a metabolic event common to both processes is being blocked.5. The physiological and ecological significance of the proecdysis temperature block is considered.

Aspects of the intermoult cycle in natantians

1. (1) The stages in the intermoult cycle of the caridean natantians Leander xiphias, Processa acutirostris, and P. edulis edulis have been determined according to the modified criteria of Drach, and the duration of the stages estimated for female L. xiphias in the winter, and for both sexes in the spring, at Villefranche-sur-Mer. 2. (2) The cycle is very much shortened in females in spring, as compared with winter, but the duration of individual stages relative to the whole cycle is not greatly altered. In spring, the cycle of males is much shorter than that of females, and the intermoult period (stage C) is much shorter in males, relative to the entire cycle. No evident difference in cycle length was noted between ovigerous and non-ovigerous females in spring. 3. (3) The duration of the intermoult cycle and the duration of embryonic development are closely related in L. xiphias. Eggs are deposited in late postmoult (B) and hatched during early to late premoult (D 1 to D 3). The approximate time of initiation of reproductive activity was noted for all three species. 4. (4) Eyestalk removal does not appear to alter the course of the intermoult cycle in male, female or ovigerous female species of L. xiphias. 5. (5) In all three species, the males are typically smaller than the females, and the ovigerous females are typically larger than the non-ovigerous females. This suggests a consecutive protandrous sexuality. 6. (6) The chromatophore patterns of the three species are described, and a diurnal rhythm of colour change is noted in the monochromatic erythrophores of the Processidae. The rhythm appears to be dependent on the integrity of the eyestalks. A significant variation in the state of dispersion of each of the four pigment types in L. xiphias was observed during premoult and postmoult stages. 7. (7) In general, the total acid-soluble carbohydrate of the three species varies little in amount during the intermoult cycle; the concentration is typically 1–3 mg glucose equivalent per g body weight, with no evident sexual differences. Eyestalk removal, in stage C or D 1 (intermoult or early premoult), is followed by a marked increase in total carbohydrate, to values of 3–10 mg/g. These observations are discussed in relation to current views concerning the hormonal regulation of moulting and metabolism.

Moulting hormones in Palaemon (=Leander) (Crustacea Decapoda) II. Differences between populations

Eye-stalk removal in certain species of Brachyura and Astacura has almost invariably led to the initiation of proecdysis. In other decapod crustaceans, however, there have been significant variations in the results of this operation. Thus Travis (1951) found that eye-stalk ablation had no effect on the duration of the moult cycle in Panulirus argus. And in the Natantia, even in a single species, quite different results have been reported. Drach (1944) found that eye-stalk removal in Palaemon (=Leander) serratus (Pennant) led, as in crabs, to the initiation of proecdysis and to accelerated moulting. In ignorance of this work I repeated some of the same experiments and found that eye-stalk removal in P. serratus led to slower moulting (Carlisle, 1953 a)— a result quite opposite to that of Drach. Scheer & Scheer (1954) confirm my results in the same species.

THE HORMONAL CONTROL OF METABOLISM IN CRUSTACEANS. IX. CARBOHYDRATE METABOLISM IN THE TRANSITION FROM INTERMOULT TO PREMOULT IN CARCINIDES MAENAS

1. A laboratory population of Carcinides maenas was sampled three times over period of 70 days, and the blood carbohydrate, blood lipochromes, total body carbohydrate, total body polysaccharide, non-protein nitrogen, and ammonia nitrogen were determined; the effect of eyestalk removal on these quantities was also examined.2. During the course of the observations, there was a progression within the population from late intermoult (C4) to early premoult (D) stages.3. The change from intermoult to premoult was signalized by the appearance of relatively large amounts of lipochromes in the blood and integument, and by an increase in total body carbohydrate content. These biochemical changes preceded any morphological signs of preparation for moult.4. Eyestalk extirpation caused an increase in the body carbohydrate, but did not alter the blood lipochromes. The increase in carbohydrate was observed only in those animals which had not undergone the change spontaneously.5. The other quantities measured showed no variation attributable either to the stage in the intermoult cycle or to eyestalk removal.6. The results are discussed with relation to the possible mechanisms of the effects observed, and the hormonal factors concerned.

Relation of Colour Change to Moulting in Prawns

STUDIES of crustacean hormones have heretofore been concentrated either on chromatophorotropic actions, or upon effects on moulting and related metabolic phenomena. We have now obtained evidence that, in Leander serratus (Pennant), the chromatophorotropic hormones are also concerned in the intermoult cycle. Numerous previous studies have shown that eyestalk removal accelerates moulting in many species of crustaceans, including L. serratus 1. We found that, in a series of 114 eyestalkless animals, only two moulted, while of 146 normal animals kept under identical conditions, twelve moulted. This difference is statistically significant at the 5 per cent level of probability. We are unable to account for the difference from Drach's results1; but Carlisle (personal communication) has suggested that there are important racial differences between prawns of the same species at Naples, Roscoff and Plymouth. Analysis of the effect of removal of eyestalk showed that it could be attributed to an increase in length of stage D 2 of the intermoult cycle2, during which the old integument is undergoing resorption, and the new integument is being formed, and to an increased mortality immediately preceding the moult in eyestalkless specimens.

Neurosecretory systems in decapod crustacea.

The sinus glands of the Brachyura are composed of swollen nerve fiber endings, which store and release secretory material synthesized within cells of the eyestalks, the brain and probably the thoracic ganglionic mass. Removal of the sinus glands from the land crab, Gecarcinus lateralis, does not induce molt, because sinus glands are reservoirs, not sources, of molt-inhibiting hormone. Increase in respiratory rate and fall in respiratory quotient, which follow eyestalk removal and signify the approach of molt, do not occur after sinus gland removal.

ENDOCRINE CONTROL OF METABOLISM IN THE LAND CRAB, GECARCINUS LATERALIS (FRÉMINVILLE). I DIFFERENCES IN THE RESPIRATORY METABOLISM OF SINUSGLANDLESS AND EYESTALKLESS CRABS ,

1. A volumetric macrorespirometer and gas analyzer are described. Procedures and precautions for their use are discussed.2. Determinations of respiratory rates and respiratory quotients before and after surgical removal of both sinus glands from the eyestalks of the land crab, Gecarcinus lateralis, indicated that, except in one respect, the crabs were fundamentally unaffected by the loss of organs which had been thought essential for maintenance of normal metabolism.3. The exception lay in an operated crab's eventual loss of its normal ability to vary the type and rate of metabolism. Indications of this loss were a constant respiratory quotient at the normal mean value and a low and relatively invariable respiratory rate. Fluctuations in rate of oxygen consumption and level of respiratory quotient were recorded from normal crabs.4. Eyestalkless crabs showed a sudden and pronounced alteration from normal respiratory rates and respiratory quotients, a change indicative of a pre-molt metabolism and culminating in a second, even more marked metabolic shift at the time of molt.5. It is clear that removal of eyestalks does, but removal of sinus glands does not, deprive these crabs of the molt-inhibiting and respiration-regulating hormone. Previous bilateral sinus gland removal does not alter the capacity of a crab to respond to subsequent bilateral eyestalk removal in the manner described above. The same is true when unilateral eyestalk removal is followed by removal of the other eyestalk.6. These metabolic data supplement and confirm morphological observations reported in an earlier paper (Bliss and Welsh, 1952). One may conceive of a brachyuran neurosecretory system composed of neurosecretory cell bodies as synthesizing elements, axons as transporting elements, and the sinus glands as storing and releasing organs. This is an extension of a concept developed originally by Scharrer and Scharrer (1944) for vertebrates and insects.

CHROMATOPHOROTROPINS IN THE CENTRAL NERVOUS ORGANS OF THE CRAB, HEMIGRAPSUS OREGONENSIS

1. The melanophores of Hemigrapsus oregonensis become punctate after eyestalk removal.2. Chromatophorotropins, which cause dispersion of the melanin when injected, are present in greatest concentration in the sinus gland, and are also present in the optic ganglia and possibly in the brain and thoracic mass of ganglia.3. The melanin dispersion in response to electrical stimulation of the eyestalk stubs and to deep probing with a hypodermic needle indicates that some source of releasable chromatophorotropins exists other than the eyestalks.4. The total amount of chromatophorotropins in the sinus gland is not necessarily greater than in any of the central nervous organs. The specialized structure and the innervation of the sinus gland suggests that its importance lies in its ability to store and rapidly release effective amounts of chromatophorotropins.5. Injection of sufficient amounts of certain substances, including muscle and gill extracts and egg albumin solution, also induces melanin dispersion in eyestalk-less Hemigrapsus oregonensis. It is suggested that these substances do not contain chromatophorotropic hormones, but the response to them is the result of a more general stimulation causing the release of chromatophorotropins from central nervous sources.

Sinus Gland Extirpation in the Crayfish Without Eyestalk Removal

In view of the increasing volume of literature pertaining to endocrine activities of the crustacean sinus gland, it is unfortunate that the only simple and sure method of removal of these glands from the body has involved the removal of the total eyestalk. The eyestalk constituting the most important light receptor of the organism, contains, in addition to the sinus gland, several important nerve ganglia, the x-organ, and other possible endocrine sources. For this reason the usual removal of so much additional tissue with the glands leaves the interpretation of the results of eyestalk removal somewhat uncertain, to say the least. Furthermore, such a function as control of retinal pigment migration, which is believed by a number of endo-crinologists to be normally under the control of the sinus gland, has not yet been confirmed by such a crucial experiment as gland extirpation since this latter has also always involved removal of the effector mechanism as well. Nearly every recent investigator in crustacea...

THE INFLUENCE OF THE SINUS GLANDS ON GASTROLITH FORMATION IN THE CRAYFISH

1. Removal of both eyestalks of Cambarus virilis and Cambarus immunis induces the formation of gastroliths at times of the year when they would not normally form. Removal of one eyestalk fails to induce gastrolith formation.2. Transplantation of sinus glands into the abdominal region of eyestalkless crayfish prevents the formation of gastroliths.3. Temperatures of 15° C. and lower prevent or greatly retard the formation of gastroliths in eyestalkless crayfish.4. As early as twenty-four hours after eyestalk removal marked histological changes occur in the regions of the stomach which secrete the gastroliths. There is proliferation and increase in height of the epithelial cells and they have already begun the secretion of the gastroliths.

Effects of Eye-Stalk Removal on Decapod Crustaceans

Effects of Eye-Stalk Removal on Decapod Crustaceans

STUDIES ON THE EFFECTS OF EYESTALK REMOVAL UPON YOUNG CRAYFISH (CAMBARUS CLARKII GIRARD)

1. Removal of both eyestalks causes a shortening of the following intermoults in Cambarus clarkii. The removal of a moult-inhibiting substance produced in the eyestalks is accepted as a reasonable explanation.2. The methods employed have been such as to show: (a) that the processes leading up to moulting can be initiated in the absence of the eyestalks; and (b) that the effect upon moulting is associated with the absence of the eyestalks, not with the shock of their removal.3. Injury other than eyestalk removal does not shorten the intermoult when performed early in the intermoult.4. Eyestalk removal always results in death, but the processes related to viability which are affected by eyestalk removal can be distinguished from the moulting processes which are affected by the same operation, although there is an apparent correlation between moulting and viability.

MOULTING, GROWTH, AND SURVIVAL AFTER EYESTALK REMOVAL IN UCA PUGILATOR

After removal of the eyestalks in Uca pugilator, all of the animals moulted within 35 days after the operation, and a few of the animals moulted twice within 48 days. Only 29 per cent of the normal animals moulted within 48 days, and none moulted twice. Eyestalk removal not only accelerated moulting but shortened the time in which the first and second moults occurred. The time at which the same percentage of moulting occurred was somewhat greater for non-segregated than for segregated animals.Viability is related to moulting, and most of the deaths following eyestalk removal in this species are due in part to a mechanical difficulty and in part to some severe deficiency occurring during or aggravated by ecdysis. There is insufficient evidence to decide whether the eyestalks secrete a specific, life-sustaining hormone directly responsible for the continued life of the animal, or whether the viability effect is in some way dependent on the moult-inhibiting function of the eyestalk. We do not believe that the loss of the eyestalks per se is directly responsible for the total mortality seen in eyestalkless crabs because of the negligible percentage of deaths occurring from 1 to 5 weeks before moulting, and because operated animals live for 5 weeks without showing any external signs of serious debilities only to succumb after ecdysis. Seventy-five per cent of the total mortality can be related directly or indirectly to ecdysis, while 25 per cent (which includes the 10.5 per cent viable specimens) does not fall in this category and may be cited in support of a differentiation of the viability and moult-inhibiting functions of the eyestalk.Eyestalk removal also leads to increased size. Some of the eyestalkless specimens 48 days after the operation have attained gigantic proportions. Pigmentation also seems to be lost, an effect which is noticeable after the first moult. No effect of eyestalk removal has been noted on copulation and shedding of eggs.