Consecutive Moults Research Articles

Modeling discontinuous growth in reared Panulirus ornatus: A generalized additive model and Cox proportional hazard model approach.

Crustaceans exhibit discontinuous growth as they shed hard shells periodically. Fundamentally, the growth of crustaceans is typically assessed through two key components, length increase after molting (LI) and time intervals between consecutive molts (TI). In this article, we propose a unified likelihood approach that combines a generalized additive model and a Cox proportional hazard model to estimate the parameters of LI and TI separately in crustaceans. This approach captures the observed discontinuity in individuals, providing a comprehensive understanding of crustacean growth patterns. Our study focuses on 75 ornate rock lobsters (Panulirus ornatus) off the Torres Strait in northeastern Australia. Through a simulation study, we demonstrate the effectiveness of the proposed models in characterizing the discontinuity with a continuous growth curve at the population level.

Biological insights into the rapid tissue regeneration of freshwater crayfish and crustaceans.

The freshwater crayfish is capable of regenerating limbs, following autotomy, injury and predation. In arthropod species, regeneration and moulting are two processes linked and strongly regulated by ecdysone. The regeneration of crayfish limbs is divided into wound healing, blastema formation, cellular reprogramming and tissue patterning. Limb blastema cells undergo proliferation, dedifferentiation and redifferentiation. A limb bud, containing folded segments of the regenerating limb, is encased within a cuticular sheath. The functional limb regenerates, in proecdysis, in two to three consecutive moults. Rapid tissue growth is regulated by hormones, limb nerves and local cells. The TGF-β/activin signalling pathway has been determined in the crayfish, P. fallax f. virginalis, and is suggested as a potential regulator of tissue regeneration. In this review article, we discuss current understanding of tissue regeneration in the crayfish and various crustaceans. A thorough understanding of the cellular, genetic and molecular pathways of these biological processes is promising for the development of therapeutic applications for a wide array of diseases in regenerative medicine.

Assessing the feasibility of dietary soybean meal replacement for fishmeal to the swimming crab, Portunus pelagicus, juveniles

The feasibility of dietary soybean meal (SBM) replacement for fishmeal was evaluated to the swimming crab Portunus pelagicus juveniles over six consecutive molts by measuring their growth, development, hemolymph cholesterol, triglycerides, phosphate, whole-body crude protein and cholesterol as well as hepatopancreatic trypsin activity, histopathology and glycogen reserves. A total of six isonitrogenous, isolipidic and isoenergetic diets were formulated with SBM replacing fishmeal at 0 (control), 20, 40, 60, 80 or 100% of total dietary protein. Each treatment consisted of 30 replicate crabs starting from the first juvenile stage and after the crabs molted to the seventh stage, three-day post molt crabs were sampled. Results showed that crabs fed the 20% SBM diet had the best growth, which was significantly higher than the control diet (0% SBM). Growth became significantly lower in the 60% dietary SBM treatment and above, while hemolymph cholesterol, triglycerides and phosphate significantly decreased with increasing dietary SBM. The whole-body moisture, crude protein and cholesterol were unaffected by dietary SBM. Meanwhile, hepatopancreatic trypsin activity significantly decreased in the 20 to 60% SBM treatments, with a further significant decrease in the 80 and 100% SBM treatments. Hepatopancreatic damage, significantly fewer epithelial cells and glycogen reserves occurred at 60% SBM and above. Results indicate that dietary SBM can replace up to 40% of fishmeal in the diets of P. pelagicus juveniles without reducing their growth or hepatopancreatic condition. Statement of relevanceSBM at 40% can be used in the diets of P. pelagicus without affecting survival or growth.

Temporal Assessment of Molting in Workers of Formosan Subterranean Termites (Isoptera: Rhinotermitidae).

Molt frequency of workers in laboratory-reared juvenile colonies and foraging population from field colonies of Coptotermes formosanus Shiraki was determined using planar arenas in laboratory. Given that, chitin synthesis inhibitor (CSI)-incorporated baits disrupt the molting process of workers that comprises the major population of a termite colony, temporal assessment of molting frequency in workers can give insights into potential methods of reducing the time to eliminate a CSI-baited colony. In our study the 10-d observation of juvenile colonies of C. formosanus suggested average daily molting incidence of workers in a colony is 1.7 ± 0.3% (mean ± SD). The results from a time lapse study on foraging population of workers showed that on average there is a 44-d intermolt period for second-instar workers molting to third instar and 45 d for third-instar workers molting to fourth instar. At low temperature (21 °C), molting frequency of workers (0.6% per day) was significantly lower than that of workers at 27 °C (2.2% per day). Information from this study suggests that time to molt is an important component of total time for eliminating colonies treated with CSI baits and reduction in time lapse between two consecutive molts may reduce the time required for colony elimination.

Temperature-Dependent Growth of Early Juvenile Southern Tanner CrabChionoecetes bairdi: Implications for Cold Pool Effects and Climate Change in the Southeastern Bering Sea

Temperature strongly influences the growth of crustaceans and directly controls distribution. Despite being commercially important, there are no data on temperature effects upon growth in newly settled southern Tanner crab Chionoecetes bairdi. Recently settled crabs were reared through three consecutive molts, both individually and in groups, at four different temperatures; 2°C, 6°C, 9°C, and 12°C. Survival was higher for crabs grown individually (92%) than those in groups (66%) owing to cannibalism, particularly during molting. There were no temperature effects on survival. Growth rate (mm/day) increased linearly with temperature, a product of exponential decline in intermolt period with increasing temperature and amolt increment that was relatively constant across temperatures. Growth rate, intermolt period, and growth increment did not differ between crabs grown singly or in groups. These data suggest that growth in 0 y aged southern Tanner crabs is strongly inhibited at temperatures less than 2°C. A small mesh beam trawl survey was conducted in the southeast Bering Sea during September 2012, a year when a cold pool (<2°C bottom water) dominated the middle shelf. Southern Tanner crab less than 12 mm (carapace width) were concentrated just north of the Alaska Peninsula and along the outer shelf where bottom water was more than 2°C, but largely absent from the middle shelf. In contrast, adult southern Tanner crabs were widely distributed across the middle and outer shelves. It was hypothesized that early juvenile southern Tanner growth is inhibited by cold pool conditions, prolonging vulnerability to predation, and reducing survival. In the future, if sea temperature rises and sea ice is diminished, less frequent and less intense cold pool events may lead to increased persistence of thermally suitable juvenile southern Tanner crab habitat across the southeastern Bering Sea middle shelf region.

Growing reared spider crabs (Maja squinado) to sexual maturity: The first empirical data and a predictive growth model

In this paper, we report the first successful attempt to grow Maja squinado in captivity from larvae to sexual maturity. Eggs were obtained from wild-caught crabs in the laboratory. The larvae–juveniles were reared together to an age of 150–210days. Subsequently, up to seven consecutive molts were individually monitored to an age of 490days maximum. Based on these individually monitored crabs, a growth model was developed to predict the molting probability and molting increment as a function of sex, temperature, and pre-molt size. The predictions of the model show that the females (25–75% percentiles of the 7th monitored molt: 106 to 139mm and 456 to 654days) appear to have a lower but less variable growth rate than the males (98 to 152mm and 378 to 518days). The size at first maturity for females was estimated to be 103.6mm. Although the model was parameterized using individuals raised in aquaculture, data and models of this type are very scarce for crustaceans and will be useful for managing the ongoing stocking program for M. squinado in the Balearic Islands. In addition, the full life cycle of the Mediterranean spider crab was completed in captivity. The mating of laboratory-reared crabs was repeatedly observed, and viable eggs and larvae were obtained from laboratory-reared adults.

Bed bugs, their blood sources and life history parameters: a comparison of artificial and natural feeding

A blood-feeding system that utilizes a small amount of whole heparinized human blood in parafilm bags is described in detail, and similarities and differences between artificially fed and naturally rodent-fed bed bugs (Hemiptera: Cimicidae) are discussed. Blood with high levels of heparin (10%) was unsuitable for artificial colony rearing, whereas bed bugs fed on 1% heparinized blood and those that naturally ingested rat blood completed their lifecycle with similar stage structures over time, with no significant differences in mortality. No differences in feeding efficiency or fertility were found in a direct comparison of bed bugs maintained under each of these two treatments, but analysis of the full lifecycle revealed that artificially fed bed bugs became significantly smaller and laid fewer eggs than rodent-fed bed bugs. The level of membrane stretching regulated the number of bed bugs that fed. When the membrane was stretched to twice its length and width, 96% of bed bugs successfully fed through the parafilm. Whole heparinized blood that was stored at 6 °C for ≥ 14 days failed to retain its nutritional value and the amount of blood consumed and number of consecutive moults were significantly reduced.

Change of external sexual characteristics during consecutive moults in Crangon crangon L

Adult males of the North Sea shrimp, Crangon crangon, were maintained for 8 months in the laboratory under natural temperature and light cycles. Successive moults were analysed for morphological changes. Out of the 70 shrimps, one male performed morphological sex reversal by reducing the male characteristics and developing female characteristics. The morphological changes including the loss of the appendix masculina appeared within a single moult cycle. This observation proves that C. crangon males may be capable of changing sex. The low number of sex reversals indicates that C. crangon is a facultative rather than an obligate protandric hermaphrodite.

Reproductive Performance of Macrobrachium rosenbergii Females in Captivity

Abstract.— The breeding frequency, fecundity, egg hatchability, larval output and viability of pond‐reared, mature Macrobrachium rosenbergii females were individually followed up during 180 d. Sexually mature prawns were maintained under controlled laboratory conditions (28.7 C and 12‐h light/d) in a 190‐L freshwater recirculation system and fed a formulated diet. Ovarian development, moulting and spawning events were checked daily. At least six consecutive moults were recorded for each of the 18 females. The duration of the intermoult period averaged 27.5 d and was not affected by ovarian development or spawning, but intermoult periods followed by spawning had significantly lower growth rates. From a total of 126 moulting events recorded, egg laying successfully followed 76 (60.3%) of them. The number of eggs per spawn (NES) varied from 26,587 to 74,775 for females weighing 20.0 to 55.8 g. The relationship between NES and female size (W; in g) was found to be NES = 484 + 1454W (r2= 0.74). Results suggest that the number of viable larvae produced per egg clutch may be increased by in vitro incubation, as the losses of eggs, which usually occur under in vivo incubation, are prevented. The present study illustrates that under adequate and stable rearing conditions, M. rosenbergii females are able to spawn up to five times during 180 d, in comparison to three to five times per year as reported for wild prawn populations.

Claw Transformation and Regeneration in Adult Snapping Shrimp: Test of the Inhibition Hypothesis for Maintaining Bilateral Asymmetry.

In the paired asymmetric claws of adult snapping shrimp, Alpheus heterochelis, the minor, or pincer, claw may transform into a major, or snapper, claw if the existing snapper claw is damaged or lost, implying that an intact snapper claw normally inhibits the contralateral pincer claw from advancing to a snapper. We find that the pincer-to-snapper advancement in external form occurs almost immediately after the snapper is lost even as late as the premolt stage. The transforming claw in turn inhibits the newly regenerating pincer claw from becoming a snapper, but if the dactyl of the transforming claw is cut, then snapper-based inhibition is removed and the contralateral claw may regenerate as a snapper, resulting in shrimp with paired snapper claws. However, damaging an established snapper claw will not allow another snapper claw to regenerate at the pincer site, implying that less inhibition is required to restrict a newly regenerating claw to a pincer than to arrest an existing pincer claw. Inhibition may be manifested largely in terms of quantity of innervation. Hence the greater innervation of the snapper side over the pincer side would inhibit the pincer side, accounting for the regeneration of paired claws in their previous configuration following loss of both claws. Loss of the paired claws in two consecutive molts retards their development so that both claws often appear as pincers, but in succeeding molts one usually differentiates into a snapper and bilateral asymmetry is restored. In contrast, shrimp with paired snapper claws retain this configuration over several molts unless one or both of the claws are lost; in that case, regeneration restores bilateral asymmetry. Thus, bilateral asymmetry of the paired claws of adult shrimp is governed by a strong intrinsic lateralizing mechanism in which the snapper claw inhibits the pincer from advancing to another snapper.

Habitat Selection, Growth Rate and Density of Juvenile Panulirus Japonicus (Von Siebold, 1824) (Decapoda, Palinuridae) At Banda, Chiba Prefecture, Japan

[Preliminary observations via SCUBA found juvenile Panulirus japonicus using small holes as a daytime refuge in the rock surface of shallow reefs (2-3 m below Chart Datum) adjacent to the Banda Marine Laboratory of Tokyo University of Fisheries. Monthly samples of juvenile P. japonicus and regular observations along a vertical rock face (area 53.2 m2) were carried out between April 1991 and December 1992, in order to detail the growth rate, density on the reef face, morphology of holes occupied and period of retention of juveniles in individual holes. Peak settlement of pueruli occurred in September with pueruli and first stage juveniles using holes of a mean diameter of approximately 12±4 mm. Initially pholad holes, predominantly of the species Lithophaga curta, were used by juveniles at Banda, however with growth the availability of suitably sized pholad holes diminished and holes of various morphologies were used. At the observation site, pueruli and first stage specimens were followed over several consecutive molts. Mean intermolt period increased with juveniles size and molting from the first through to the sixth molt stage required approximately 2.5 months (78.5±2.2 days). The maximum number of individuals on the rock face occurred immediately after peak settlement in autumn (0.21 and 0.32 inds.m-2, September 1991 and 1992 respectively) with this density declining prior to winter. Densities on the rock face from November (0.094 inds.m-2) remained relatively constant over winter period and from May/June declined further as juveniles changed from using holes to cave/crevice style habitats situated off the rock face. Growth rate of juvenile P. japonicus was fast, from peak settlement ofpueruli [carapace length (C.L.) ~ 7.5 mm] in September, a mean size of C.L. 35-40 mm was attained after one year. Recruitment to the fishery (minimum landing size C.L. 42 mm) is estimated to occur over the second winter after settlement as a puerulus., Preliminary observations via SCUBA found juvenile Panulirus japonicus using small holes as a daytime refuge in the rock surface of shallow reefs (2-3 m below Chart Datum) adjacent to the Banda Marine Laboratory of Tokyo University of Fisheries. Monthly samples of juvenile P. japonicus and regular observations along a vertical rock face (area 53.2 m2) were carried out between April 1991 and December 1992, in order to detail the growth rate, density on the reef face, morphology of holes occupied and period of retention of juveniles in individual holes. Peak settlement of pueruli occurred in September with pueruli and first stage juveniles using holes of a mean diameter of approximately 12±4 mm. Initially pholad holes, predominantly of the species Lithophaga curta, were used by juveniles at Banda, however with growth the availability of suitably sized pholad holes diminished and holes of various morphologies were used. At the observation site, pueruli and first stage specimens were followed over several consecutive molts. Mean intermolt period increased with juveniles size and molting from the first through to the sixth molt stage required approximately 2.5 months (78.5±2.2 days). The maximum number of individuals on the rock face occurred immediately after peak settlement in autumn (0.21 and 0.32 inds.m-2, September 1991 and 1992 respectively) with this density declining prior to winter. Densities on the rock face from November (0.094 inds.m-2) remained relatively constant over winter period and from May/June declined further as juveniles changed from using holes to cave/crevice style habitats situated off the rock face. Growth rate of juvenile P. japonicus was fast, from peak settlement ofpueruli [carapace length (C.L.) ~ 7.5 mm] in September, a mean size of C.L. 35-40 mm was attained after one year. Recruitment to the fishery (minimum landing size C.L. 42 mm) is estimated to occur over the second winter after settlement as a puerulus.]

A growth model for a hyperiid amphipodThemisto japonica (bovallius) in the Japan Sea, based on its intermoult period and moult increment

Themisto japonica was reared at 1, 5, 8, and 12°C in the laboratory to estimate its intermoult period (IP) and increase in body length (BL) at each moulting (ΔBL).IP was found to be a function of temperature andBL of the specimens, longerIPs being associated with lower temperature and larger specimens.ΔBL was not affected by temperature but increased with growth of the specimens. Observations on consecutive moults indicated that one new segment was added to pleopod rami at each moulting.ΔBLs obtained from the measurement of the segment number of pleopod rami andBL of wild specimens were slightly larger than values obtained from laboratory-raised specimens.IP data obtained from laboratory-reared specimens are combined withΔBL data from wild specimens to establish a growth model forT. japonica from its release from the marsupium (1.31 mmBL) to the maximum size (17 mmBL) as a function of temperature. This growth model predicts that a total of of 18 moultings is needed forT. japonica to reach the maximum size regardless of temperature, although the time needed to reach the maximum size is highly dependent on temperature. The life cycle, from the newly released larvae (1.31 mmBL) to the spent females (10–17 mmBL), was estimated as 333–593 days at 1°C, 195–347 days at 5°C, 118–210 days at 10°C and 82–146 days at 15°C; the last may be the upper temperature limit forT. japonica. Growth rates ofT. japonica expressed on the basis of body mass are comparable to the rates of euphausiids of equivalent size when the effect of temperature is accounted for. Feeding conditions ofT. japonica in the field are also discussed.

Resting Stage in the Reproductive Cycles of Gammarus

WHEN mature, a female Gammarus has long oostegites fringed with setae which lock together to form a brood pouch where the fertilized eggs are incubated. The development of the setae coincides with the enlargement of oogonia and is presumably dependent on hormonal control. The setose oostegites may persist through several consecutive moults, provided a new brood is produced each time. If the development of oogonia is stopped either by removal of the ovary or by some external physical factor, the oostegite setae are lost at the next moult and the female is said to have entered a resting stage. The reappearance of the setae may be brought about by the subsequent enlargement of the oogonia1,2. It is apparent that the resting stage is a mechanism by which the reproductive cycle may be regulated.

A study of the biology of the wild rabbit in climatically different regions in eastern Australia. II. Seasonal changes in the pelt

Data are presented on moulting in the wild rabbit, Oryctolagus cuniculus (L.), at four sites in eastern Australia — subalpine, semi-arid, subtropical, and Mediterranean. The Australian wild rabbit moults twice a year. A spring–summer moult, which shortens the fur for summer, progresses from the ventral surface towards the dorsal (dorsad) and an autumn–winter moult, in which longer and more wavy fur grows, progresses from the dorsal surface to the ventral (ventrad). During the breeding season the pattern of moulting in females becomes scattered. Rabbits under 3 months old appear to have consecutive moults which usually progress dorsad, irrespective of season. The wave pattern of the moults becomes less regular with increasing age. In the subalpine area moulting was limited to definite seasons and was completely absent during the cold winter. At the other three sites where the winter was milder, moulting occurred throughout the year but still with definite peaks of ventrad moulting in spring–summer and of dorsad moulting in autumn-winter.