Late Premoult Research Articles

Feeding rates and gross growth efficiencies in Hyasaraneus L. larvae (Decapoda: Majidae) Reared in the laboratory

Rates of food uptake were measured for individually reared larvae of the spider crab Hyas araneus L. feeding on freshly hatched Artemia nauplii at constant 12°C. Food particles and fragments thereof were registered quantitatively by means of automatic image analysis. Feeding rates ( FR) of crab larvae were given as number of nauplii and amounts of dry weight, carbon, nitrogen, hydrogen, and energy (estimated from C) consumed per day. In both zoeal stages FR increased during postmoult and intermoult, remained high during early and intermediate premoult, and decreased again during late premoult. No clear pattern was found in the course of daily FR of the megalopa. Gross growth efficiencies ( K 1) showed a dramatic decrease from postmoult to early premoult (>60 to <20%) in both zoeal stages. Daily consumption expressed as % body weight also decreased significantly in these instars. Average daily FR were highest in the zoea II, lowest in the megalopa, and intermediate in the zoea I. Since development of the megalopa took the longest time, the total amount of food consumed by this instar was equal to consumption in both zoeal stages combined. K 1 (C-based) was approximately the same in the zoeal instars (24.3 and 25.2), but lower in the megalopa (19.4%), averaging 21.5% for total larval development from hatching to the first crab stage.

Moult cycle and morphogenesis inHyas araneus larvae (decapoda, majidae), reared in the laboratory

Moult cycle and morphogenesis in larval instars (zoea I, zoea II, megalopa) of the spider crabHyas araneus (L.) were studied in the laboratory. Changes in the epidermis and cuticle were documented photographically at daily intervals to characterize the stages of the moult cycle. Stage A (early postmoult) is a very short period during which the larva takes up water. During late postmoult (B) and intermoult (C) the endocuticle is secreted, and there is conspicuous epidermal tissue condensation and growth. The onset of early premoult (D0) is characterized by epidermal apolysis, occurring first at the bases of the setae in the telson of zoeal instars or in the rostrum of the megalopa, respectively. Intermediate premoult (D1) is the main period of morphogenesis, in particular of setogenesis: in the setae of the zoeal telson and carapace there is invagination or (in the zoea II) degeneration of epidermal tissues. Formation of new setae in the interior of epidermal tubules was observed in zoeal maxillipeds and in the antennae of the zoea II and megalopa instars. During late premoult (Stages D2–4) part of the new cuticle is secreted, and the results of morphogenesis become clearly visible. For technical reasons (rigid exoskeleton) only a preliminary account of the moult cycle in the megalopa can be given. A time schedule is suggested for the stages of the moult cycle. It is estimated that postmoult (A–B) takes ca 9 to 15 % of total instar duration, intermoult (C) ca 22 to 37 %, and premoult (D) ca 48 to 69 %. There is an increasing trend of relative portions of time (% of total instar duration) from instar to instar in Stages A–C (mainly in the latter) and a decreasing trend in Stage D (mainly in D0 and D2–4).

Changes in lipid and protein during starvation and the moulting cycle in the tiger prawn, Penaeus esculentus Haswell

Tiger prawns, Penaeus esculentus Haswell (mean wt 20.8 ± 0.3 g, range 13.9–27.7 g) contained 1–2% extractable lipid, 13% protein (biuret method) and 71–74% water (wet wt). In 21 days, the weight of fed prawns increased by 3% and that of starved prawns decreased by 4.4%. Protein was the major energy source during 14 days of starvation, with a loss of 550 mg of total protein compared with a loss of 84 mg of total lipid. The absolute amount of water present remained constant. Of three different tissue compartments, abdomen, cephalothorax, and digestive gland, the abdomen contributed the most protein (330 mg) and lipid (35 mg) during 14 days of starvation. Digestive gland, although containing the largest percentage wet wt of lipid, accounted for only 8.3% of the total lipid in the prawn, and contributed only 18 mg of lipid in 14 days of starvation. Lipid concentration in the digestive gland increased during early premoult (stage D 4) and dropped in late premoult (stage D 4). Resting oxygen consumption rate remained constant at ≈0.1 ml · g −1 · h −1 at 25°C during 21 days of starvation.

Ciliary structures in the branchial unicellular glands of the grass shrimp,Palaemonetes pugio

A unicellular exocrine gland possessing an epicuticular ductule occurs in grass shrimp gills. This gland displays ultrastructural changes in relation to the molt cycle. These changes include an increase in the quantity of secretory granules during late premolt, and the development of ciliary axonemes in relation to ductule formation.

Induced Maturation of Prawn Penaeus indicus

Viable spawns have been obtained in the laboratory from untreated prawn Penaeus indicus and from others which had one eyestalk ablated. Fecundity was shown to be dependent on spawning technique, female size and whether the spawner was wild or domestic. Using low aeration during spawning, domestic unablated female fecundity was significantly lower than it was for wild females, due to a concomitantly smaller ovary volume. During late premoult, mature ovaries are resorbed to ovarian Stage 1-2 and after ecdysis they redevelop. 52.1 O/O of spawnings occurred during early premoult, 44.4 O/o during intermoult, 3.5 O/O at premoult, while no spawns occurred during late premoult or early postmoult. Average egg numbers and hatch successes were higher for unablated females when compared with ablated females. Average spawns per moult cycle were 1.98 and 2.24, respectively. It was conservatively estimated that wild females spawn at least 7-9 times in a lifetime. There were twice the number of spawns with a black tank background as there were with a white one and the former yielded higher average egg numbers and hatch successes. General pigmentation, ovary, egg and nauplius colour was dependent on background colour. Moult-cycle duration was temperature dependent but generally shorter for ablated females. As female condition decreased, moult-cycle duration decreased accordingly for any given temperature. Spawning activity declined when the condition factor was less than 0.8. Both ablated and unablated spawning females > 39 g tended to decrease in mass and condition while females < 39 g continued to grow. Nutrition is probably the main contributory factor to this anomalous growth. Large females possibly have nutritional requirements different from females of less than 39 g. A viable F, generation of P. indicus has been reared.

Ammonia excretion of the sand-shrimpCrangon crangon (L.) during the moult cycle

Ammonia excretion in the shrimpCrangon crangon (L.) shows a cyclical pattern during the moult cycle. At the early premoult (stage D0) there is a 7 to 17% increase over that characteristic at intermoult; at late premoult (stage D2) excretion decreases to a minimum; immediately after ecdysis, the excretion rate is 1.5 to 2.6 times higher than at the intermoult stage (Table 1).

The urinary flow inCrangon vulgaris(Fabr.) (Crustacea, natantia) during the moult cycle

Abstract The urinary flow, measured as changes in medium conductivity, was investigated during the moult cycle of Crangon vulgaris living in 10%0 at 20.5 °C. The urination frequency in an intermoult animal was once per 50-55 minutes, while the frequency in the early postmoultincreased to once per 15-20 minutes. A continous recording of the urination frequency during the moult showed a decrease in late pre moult from the intermoult values to once per 60-80 minutes. Together with a fall in urine production this indicates that part of the increase in water content prior to ecdysis is caused by decreasing diuresis. The urine production in the intermoult was found to be around 20 μl · g-1 · h-1. After the moult the production increased to 50-60 μl · g-1 · h-1. The changes in diuresis are interpreted as changes in water fluxes due to, among other factors, changes in surface permeability.

Activity and kinetic properties of pyruvate kinase from some tissues of the crayfish, Orconectes limosus Raf. (Crustacea: decapoda) in different stages of the moult cycle

1. 1. An increase in pyruvate kinase activity from an O. limosus crayfish abdominal muscle was stated during premoult and postmoult stages. In hepatopancreas and heart, changes in enzyme activity were not observed during the moult cycle. 2. 2. The pyruvate kinase of crayfish hepatopancreas, in intermoult (C 4), late premoult (D 3–D 4) and postmoult (A–B) stages, was characterized by hyperbolic kinetics with the phosphoenolpyruvate as substrate; whereas, in early premoult stages (D 0–D 2) by the sigmoidal one. The enzymes from the abdominal muscle and heart showed hyperbolic kinetics.

Variation in lipid classes during the molting cycle of the prawn Penaeus japonicus

The variation in the concentration and fatty acid composition of lipid classes during the molting cycle of the prawn Penaeus japonicus was investigated. The lipid concentration of the whole body reached a maximum at mid-premolt (Stage D2) and then decreased to low level at late premolt (Stage D3–4). The accumulation of lipids during the premolt period seemed to be attributable to the increase of both polar and neutral lipids. The increase of neutral lipids at Stage D2 was derived from not only triglycerides but also free sterols and free fatty acids. Regarding the fatty acid composition of every lipid class, a marked variation occurred mainly at the intermolt (Stage C). In this stage, the polar lipids were rich in monoenoic acids such as 18:1 and poor in polyenoic acids such as 20:5ω3 and 22:6ω3. The triglycerides were rich in polyenoic acids at Stage C, but poor in monoenoic acids such as 16:1 and 18:1. The steryl esters contained large amounts of saturated acids such as 16:0 and 18:0 throughout the molting cycle, however the level of polyenoic acids increased at Stage C.

Variation in lipid classes during the molting cycle of a shrimp.

This study deals with the variations in the content and fatty acid composition of lipid classes during the molting cycle of a fresh-water shrimp, Palaemon paucidens. The lipid content increased at mid premolt (stage D2) and then decreased at late premolt (stage D3-4). The accumulation of lipids during the early premolt period seemed to be attributed mainly to that of polar lipids. Throughout the molting cycle, the shrimp con-tained more polar than neutral lipids, the latter consisting mainly of triglycerides, free sterols, and free fatty acids. In the case of the polar lipids, the percentage composition of saturated acids such as 16:0 and 18:0 increased at stage D2. In contrast to the polar lipids, the tri-glycerides showed no marked variation in the fatty acid composition during the molting cycle. The free fatty acids showed an increase in saturated acids such as 16:0 and monoenoic acids such as 16:1 and 18:1 at intermolt (stage C).

The mandibular organ of the lobster, Homarus americanus.

The lobster mandibular organ is well vascularized and its polygonal cells are arranged loosely around blood vessels and blood sinuses. Numerous mitochondria and microbodies (peroxisomes) give the acidophilic cytoplasm a finely granular appearance, but there is no evidence of secretory granules. The abundant endoplasmic reticulum is almost entirely agranular and occurs in two morphologically distinct forms: tubular and cisternal. The tubular reticulum is randomly distributed and may represent the site of synthesis and transport of the mandibular organ product. The cisternal reticulum is frequently associated with microbodies. Both forms of endoplasmic reticulum proliferate during mid to late premolt. Mandibular organ ultrastructure closely resembles that of cells known to synthesize steroids or lipids, which suggests that this organ may have a similar function. There is no functional evidence of involvement in molt control in Homarus, but ultrastructural and other evidence suggests an analogy with insect corpus allatum.

Bioconversion of desmosterol to cholesterol at various stages of molting cycle in Palaemon serratus pennant, crustacea decapoda

1. 1. The bioconversion of desmosterol to cholesterol during the molting cycle of the shrimp, Palaemon serratus, was investigated in conjunction with the variation of lipids, unsaponifiable matter and sterol concentrations. 2. 2. The lipid concentration was high at stages D 1′ and D 1″ (early premolt). The unsaponifiable matter concentration was high at stages A 2, B 1 and B 2 (postmolt). However, the sterols were contained at an almost constant level in the tissues throughout all the molting stages examined. 3. 3. The ability for conversion of desmosterol to cholesterol rose markedly at stages A 2-B 1, decreased at stage B 2 and then appeared to increase slightly up to stage D 1′ and decreased notably at stages D 1′-D 1″ to the almost constant levels maintained throughout the late premolt (stages D 1‴ and D 2).

Protein and RNA synthesis in the premolt crayfish, Orconectes virilis

1. The protein and RNA content of the hepatopancreas of the crayfish Orconectes virilis increases during the normal premolt stage while the quantity of DNA remains unchanged. Eyestalk removal from intermolt animals elicits premolt activity including changes in RNA and protein content similar to that observed in normal premolt crayfish. 2. The rate of incorporation of labelled leucine into hepatopancreatic protein in vitro increased during early premolt and decreased at late premolt. The rate of incorporation of 3H-uridine into hepatopancreatic RNA in vitro was essentially constant from intermolt to mid-premolt but increased at late premolt. 3. No striking changes occurred in the rates of protein synthesis or RNA synthesis when the hepatopancreas was incubated in vitro in the presence of crustecdysone or eyestalk extracts (molt inhibiting hormone).

Blood and hepatopancreas copper in crangon vulgaris (fabricus)

1. 1. The concentration of copper in the blood of Crangon vulgaris collected in the autumn 1967 from East Anglesey and West Anglesey ranged from 41 to 159 μg/ml respectively. Individual variation in blood copper concentration could not be correlated with sex or size. 2. 2. A significant correlation was found betwee blood copper concentration a moult stage; highest values were found in the late premoult (D 2/D 3) animals and lowest values found in postmoult (A-B) animals 3. 3. Hepatopancreas (Cu) varied from 13 to 480 μg/g dry wt. for animals collected in the autumn from East Anglesey and 118 to 2900 μg/g dry wt. for West Anglesey. 4. 4. Histochemical studies revealed copper located in vacuoles within cells of the hepatopancrease of all animals examined. Wide variation was found in the sizes of these bodies, their numbers and the number of cells containing them. 5. 5. The copper content of the blood of shrimps maintained in copper-enriched sea water did not increase whereas the hepatopancreas accumulated copper. 6. 6. All the detectable copper eluted from agar electropherograms of blood was carried by haemocyanin. An estimate of approximately 0·2 per cent was found for the copper/protein ratio of unpurified Crangon haemocyanin.

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.