Subsequent Molt Research Articles

Appendage damage effects on Southern Rock Lobster growth and mortality

Handling of crustaceans can result in injuries such as limb damage, reducing post-release survival and subsequent growth. Quantifying the impact of handling damage can provide insight into the effects of increased handling, which can occur when undersized animals are released by fishers or during translocations of animals between areas. We investigated the impact of handling on the Southern Rock Lobster (Jasus edwardsii) using three decades of scientific tag-recapture data from a no-fishing reserve. We used a Bayesian modeling approach with a modified Von Bertalanffy growth model which is robust to measurement error and Cormack-Jolly-Seber capture-recapture model to estimate growth and survival probability parameters. We found that even low levels of damage (1–4 appendages) can decrease growth by ∼ 10 % in the subsequent moult. Male lobsters suffered greater effects of handling-induced damage than did females, potentially due to the additional energy reserves available to brooding females.

New record of the sphingid moth Acherontia styx Westwood, its parasitoid Trichogramma achaeae in Jasmine Jasminum sambac L., and its bioecology

The sphingid moth larvae are voracious defoliators of several crops. The present study was conducted to investigate damage of Acherontia styx on Jasmine, their seasonal incidence, and bioecology. Larval instars fed on jasmine leaves and flowers, with the highest defoliation being 35% and highest flower damage 47% during September. The lifecycle consisted of egg, five larval instars, pupal, and adult stages. The eggs were pearly white in colour and emerged larvae were cylindrical with a prominent anal horn. In subsequent moults the larvae continued to feed and become larger until they turned a reddish colour and ceased feeding prior to pupating in the soil. Adult moths were robust and swift fliers. The total life cycle from egg to adult was 56 days for males and 59 days for females. Trichogramma achaeae Nagaraja & Nagarkatti was noticed and documented as a potential egg parasitoid of the sphingid moth, a new record. A natural parasitization of eggs was noticed under field conditions, with changed colour of eggs to deep black from which a tiny parasitic wasp emerged, identified as T. achaea.

Description of the postmarsupial manca stages of Armadillidium ficalbii (Crustacea, Isopoda, Oniscidea)

ABSTRACT The postmarsupial manca stages of Armadillidium ficalbii Arcangeli, 1911 were studied in detail by morphological analysis. Ovigerous females were reared separately under controlled conditions, allowing us to follow the stages of development from release from the marsupium until the appearance of the first juvenile stage, identified by the full development of the seventh pair of pereopods. Each newborn was followed to record the subsequent moults that identify the three postmarsupial manca stages. Manca stage M I had a mean duration of 10 h, manca stage M II 8–9 days, and manca stage M III 9–10 days. The cephalothorax width was measured to provide a growth measure for each stage. The mean values of the cephalothorax width were: 0.589 mm for M I, 0.718 mm for M II and 1.274 mm for M III. The morphological modifications in the three postmarsupial manca stages were described, the body parts illustrated, and SEM images taken. The distinguishing characteristics among mancas were discussed, and comparisons made with manca stages of other terrestrial isopod species.

Analysis of biological and biochemical parameters of adult male spiny lobsters Jasus lalandii for identification of possible growth predictors

Biological body parameters of adult male West Coast rock lobsters, Jasus lalandii, of commercial size were analysed over two years to determine reserve accumulation during two moult (i.e. growth-) cycles. Two fishing areas were compared that were historically known for fast- and slow growth, respectively. In addition, setagenic development for moult stage determination and the biochemistry of the hepatopancreas were investigated from the fast growth area. This information was intended to confirm previously proposed predictors of annual male moult increment and identify potential new ones. Annual moult increments in these areas were determined from tag-and-recapture studies, including the seasons for which reserve accumulation was analysed. Data from the present study were not robust enough to confirm previously proposed predictors from peak accumulation months (March – May). Data arranged per moult stage were also unsuitable for prediction. Further results analysis, however, identified a subset of data that are potentially more useful: Hepatosomatic index HSI (+ 6 %), lipid content (+ 9 % ww, + 12 % wD) and lipid per whole hepatopancreas (+ 24 %) are all significantly higher in July 2011 than in July 2010, the last sampled months before the respective annual moult. These differences correlate with a 26 % (0.7 mm) faster growth during subsequent moult in 2011 than in 2010. Aspects of hepatopancreas lipid metabolism in the months prior to moult have therefore the potential to provide simple and robust predictors of growth in adult male J. lalandii. However, more research is required that also includes the months adjacent to July in more than one area and for a longer period than two years.

AOP Report: Inhibition of Chitin Synthase 1 Leading to Increased Mortality in Arthropods.

AOP Report: Inhibition of Chitin Synthase 1 Leading to Increased Mortality in Arthropods.

Growth and biochemical composition of hatchery reared Scyllaridae lobster (Thenus australiensis) larval stages, nisto and juvenile first stage

Understanding the nutrition of lobster larvae through the examination of growth and biochemical composition across different life stages is a critical component of aquafeed development of new aquaculture species. Therefore, in the present study, we benchmarked growth and changes in biochemical composition of Thenus australiensis from first larval stage (S1) to the juvenile first stage (J1). The larval cycle was completed in a maximum duration of 31 d and comprised four successive larval stages followed by a post-larvae stage (nisto) and a subsequent moult to J1. Growth during all larval stages, metamorphosis to nisto, and moult to J1 were tracked through the measurement of size (total length, TL and cephalic/carapace width, CW), individual wet (WW) and dry (DW) weights. Bulk samples of all developmental stages were collected and analysed for ash, crude protein, total lipid, nitrogen free extract (NFE) and gross energy of dry matter (DM). Lipid class, fatty acid and mineral composition of S1, S4 and J1 of DM were also measured to provide more detailed analysis of composition. As expected, TL, CW, WW and DW increased with each subsequent stage except for lower TL and CW of the nisto stage when compared to S4 larvae. The DW increases throughout larval development until nisto and was defined by higher ash, crude protein, total lipid and NFE absolute amounts. However, from nisto to J1, total lipid decreased by half. The total lipid of DM increased as larval stages progressed to the nisto phase, declining rapidly when monitored at J1. The accumulation of lipid during the larval phase highlights the importance of building lipid stores to maintain metabolism during the non-feeding nisto stage and moult to J1. Polar lipid was the dominant lipid group in comparison to neutral lipids stores. The energy content of larvae, nisto and J1 reflected the accumulation of lipid over the larval stages and its depletion during the non-feeding nisto stage. The environmental influence on elemental uptake was evident at the moult to J1 with a >4-fold increase in ash content in individual J1 compared to nisto. This was supported by an increase of major mineral constituents of the exoskeleton, particularly, calcium. The present study is the first describing in detail the growth and biochemical composition of all the larval stages until J1 for T. australiensis. The new knowledge on nutrition will support progress in aquafeed development for this new aquaculture species.

Baseline corticosterone does not reflect iridescent plumage traits in female tree swallows

The production of high quality secondary sexual traits can be constrained by trade-offs in the allocation of energy and nutrients with other metabolic activities, and is mediated by physiological processes. In birds, the factors influencing male plumage quality have been well studied; however, factors affecting female plumage quality are poorly understood. Furthermore, it remains uncertain which physiological traits mediate the relationship between body condition and ornaments. In this three-year study of after-second-year female tree swallows (Tachycineta bicolor), we investigated (1) the relationship between baseline corticosterone near the end of the brood-rearing period (CORTBR) and feather colour characteristics (hue, saturation, brightness) the following year, and (2) the relationship between baseline corticosterone measured during incubation (CORTI) and brood rearing (CORTBR), and feather colour in the same year. To control for reproductive effort, we included reproductive parameters as covariates in all analyses. In this first study between CORT and the plumage colour characteristics of a species bearing iridescent feathers, we did not find any relationship between CORTBR and the colour of subsequently-produced feathers, nor did we find any relationship between CORT and the colour of feathers displayed during that breeding season. If CORT levels at the end of breeding carry over to influence the immediately subsequent moult period as we expect, our results generally indicate that structural plumage quality may not be as sensitive to circulating CORT levels compared to carotenoid-based colouration. Future studies, particularly those employing experimental manipulations of CORT during moult in species with iridescent traits, are necessary to fully determine the role glucocorticoids play in mediating the quality of secondary sexual characteristics.

Description of the postmarsupial manca stages of Armadillidium granulatum (Crustacea, Isopoda, Oniscidea)

ABSTRACTThe development of the postmarsupial manca stages of Armadillidium granulatum Brandt, 1833 was studied in detail by morphological analysis. Ovigerous females were reared separately under controlled conditions, allowing us to follow the stages of development from release from the marsupium until the appearance of the first juvenile stage, identified by the full development of the seventh pair of pereopods. Each newborn was followed to record the subsequent moults that identify the three postmarsupial manca stages. Manca stage M I had a mean duration of 6 h, manca stage M II 15 days, and manca stage M III 32 days. The cephalothorax width was measured to provide a growth measure for each stage. The mean values of the cephalothorax width were: 0.512 mm (± 0.083 SD) for M I, 0.677 mm (± 0.058 SD) for M II and 1.194 mm (± 0.079 SD) for M III. The morphological modifications in the three postmarsupial manca stages were described, the body parts illustrated, and SEM images taken. The distinguishing characteristics among mancas were discussed, and comparisons made with manca stages of other terrestrial isopod species.

Harbor seal use of glacier ice and terrestrial haul‐outs in the Kenai Fjords, Alaska

AbstractHarbor seals, Phoca vitulina, use diverse haul‐out substrates including ice calved by tidewater glaciers. Numbers of seals at glacial and terrestrial haul‐outs on the southeastern Kenai Peninsula, Alaska, were assessed using aerial, vessel, and video surveys. Mean annual abundance at glacial and terrestrial haul‐outs differed temporally. From 2004 to 2011, numbers of seals counted during the molt increased 5.4%/yr at glacial haul‐outs and 9%/yr at terrestrial haul‐outs while numbers of pups increased 5.0%/yr at glacial sites and 1.5%/yr at terrestrial sites. Numbers of seals without pups counted during pupping increased 7.96%/yr at glacial sites and 5.1%/yr at terrestrial sites. Results indicate that pupping and molting locations are not equivalent and population monitoring during the molt does not necessarily reflect habitat association of pupping seals. Ratios of pups to total seals counted during pupping and the subsequent molt were used to contrast habitat use. Low proportions of pups at terrestrial haul‐outs, relative to most glacial haul‐outs, indicate an overall preference for pupping in glacial haul‐outs. High proportions of pups at most glacial sites (during pupping and molting) suggest reduced use of tidewater glacier habitats by nonbreeders and molting seals. Results suggest more seals associate with glacial haul‐outs than currently estimated.

Biomarker of burden: Feather corticosterone reflects energetic expenditure and allostatic overload in captive waterfowl

AbstractAllostatic load describes the interplay between energetic demand and availability and is highly context dependent, varying between seasons and life‐history stages. When energy demands exceed physiological set points modulated by glucocorticoid hormones, individuals may experience allostatic overload and transition between stages in sub‐optimal physiological states.Corticosterone, the major glucocorticoid hormone regulating energy expenditure in birds, is incorporated into growing feathers (CORTf), and it has been suggested that CORTfreflects long‐term records of allostatic load during feather growth. However, relationships between allostatic load and CORTfhave not been adequately evaluated. If such relationships exist, the use of CORTfto investigate cross‐seasonal effects could provide novel insights into impacts of past allostatic load and/or overload events.We tested whether experimental increases in daily workload during two adjacent life‐history stages would be reflected in CORTflevels, and examined if CORTflevels reflected either current energetic demand or allostatic load prior to feather growth.Daily workloads in female mallardAnas platyrhynchosducklings were increased over a 6‐week period using physical obstacles and/or carrying back‐mounted weights. We measured daily energy expenditure, growth, body mass, and CORTfin growing ducklings. Then, we induced feather moult and reapplied combinations of workload treatments for an additional 6 weeks to investigate whether effects of past energetic demands would be detected in future CORTflevels.Ducklings confronted with higher workloads during development had reduced body mass, growth rates and consequently higher daily energy expenditure and CORTfvalues compared to controls. When ducklings were fully developed, CORTfpatterns in birds re‐exposed to workload treatments reflected only current, rather than past, energetic demands. However, under allostatic overload conditions, past levels of CORTfwere positively associated with CORTfin the subsequent moult.Our study confirms the previously untested assumption that CORTfreflects energetic demand during the period of feather growth in a precocial bird. We show that allostatic overload conditions early in life, which temporarily suppress growth, can be detected using CORTf, an event potentially missed in studies which rely solely on measures of body condition alone.We suggest that CORTfcan provide a valuable biomarker of allostatic load and overload conditions during the period of feather growth, but highlight how context should be considered for studies using CORTfto investigate influences of carryover effects. Our study contributes to building a physiological foundation to inform interpretations of ecological patterns using CORTf.Aplain language summaryis available for this article.

Artificial Infection of Ticks with Borrelia burgdorferi Using a Microinjection Method and Their Detection In Vivo Using Quantitative PCR Targeting flaB RNA.

Borrelia burgdorferi is maintained in nature by a tick-rodent infection cycle where it traverses and colonizes a variety of host and vector tissues. A tick-borne murine model has been developed to study Lyme disease in the laboratory, which has a substantial impact in advancing our knowledge of spirochete infectivity and pathogenesis. Here, we detail a microinjection-based method for rapid and efficient infection of ticks with B. burgdorferi. While laboratory generation of B. burgdorferi-infected nymphs via natural larval engorgement on infected hosts and subsequent molting could take several weeks to months, the microinjection-based infection procedure requires only a few hours to generate infected ticks and allows introduction of defined quantities of spirochetes, including mutant isolates that are attenuated for infection in mice and thus cannot be naturally acquired by ticks. We also describe a quantitative PCR-based protocol for the measurement of B. burgdorferi in tick and murine hosts targeting spirochete RNA that is highly efficient, reproducible, and a better surrogate of active infection.

Effects of Prior Experience on Shelter-Seeking Behavior of Juvenile American Lobsters.

Shelter-seeking behaviors are vital for survival for a range of juvenile benthic organisms. These behaviors may be innate or they may be affected by prior experience. After hatching, American lobsters Homarus americanus likely first come into contact with shelter during the late postlarval (decapodid) stage, known as stage IV. After the subsequent molt to the first juvenile stage (stage V), they are entirely benthic and are thought to be highly cryptic. We hypothesized that postlarval (stage IV) experience with shelter would carry over into the first juvenile stage (stage V) and reduce the time needed for juveniles to locate and enter shelters (sheltering). We found some evidence of a carryover effect, but not the one we predicted: stage V juveniles with postlarval shelter experience took significantly longer to initiate sheltering. We also hypothesized that stage V juveniles would demonstrate learning by relocating shelters more quickly with immediate prior experience. Our findings were mixed. In a maze, juveniles with immediate prior experience were faster to regain visual contact with shelter, suggesting that they had learned the location of the shelter. In contrast, there was no significant effect of immediate prior experience on time to initiate sheltering in an open arena, or in the maze after juveniles had regained visual contact. We conclude that very young (stage V) juvenile lobsters modify their shelter-seeking behavior based on prior experiences across several timescales. Ecologically relevant variation in habitat exposure among postlarval and early juvenile lobsters may influence successful recruitment in this culturally and commercially important fishery species.

Precocious mating in the freshwater crab Candidiopotamon rathbunae (De Man, 1914)

In Brachyura copulation prior to the instar in which females become fully morphologically and functionally mature (i.e., produce fertile eggs) is exceptional. However, in the freshwater crab Candidiopotamon rathbunae (family Potamidae), adult males frequently mate with immature females (precocious mating). The size of female functional maturity is 22-23 mm carapace width. Immature females larger than 15 mm carapace width are observed mating, usually have sperm in their seminal receptacles, and this sperm is retained through subsequent moults. Precocious mating in C. rathbunae could potentially increase the reproductive capacity of females. It could have evolved as an adaptation to a seasonally amphibious life, during which the mating opportunities are reduced compared to a permanently aquatic lifestyle. Data from the few other brachyuran taxa with precocious mating fail to indicate a common rationale.

Biological and physiological effects of Coriandrum sativum on House fly Musca domestica (Diptera: Muscidae)

This Study is conducted to evaluate effects of (leaves, fruits) powder and (oil, alcohol) extract of Coriander (Coriandrum sativum) plant on some biological and physiological aspects of House fly, Musca domestica at laboratory conditions. Result show that these preparations caused biological effects represented in high dead percentage in second instar, fed on different concentrations of food treated with them reached to 27.6, 55.3 at concentration 20% of leaf and fruit powder respectively and 67.3, 77.2% at 10% of oil and alcohol extract of fruit, respectively. Furthermore, study also show reduction in pupation and adults emergence percentage. However, leafs powder had slighter effect than powder and extract of fruit of tested plant. The study show physiological effects in treated larvae such as molting failure at subsequent molt to larvae , pupa or to adult, also morphological aberration represented in small size, dark pigment, reduce age and folding of the adult wings. In almost cases, the higher concentration the more morphogenetic aberration. This study leads us to conclude that coriander had chemical compounds which played a negative role in some biological and physiological aspects of house fly.

Leg Regrowth in Blaberus discoidalis (Discoid Cockroach) following Limb Autotomy versus Limb Severance and Relevance to Neurophysiology Experiments.

BackgroundMany insects can regenerate limbs, but less is known about the regrowth process with regard to limb injury type. As part of our neurophysiology education experiments involving the removal of a cockroach leg, 1) the ability of Blaberus discoidalis cockroaches to regenerate a metathoracic leg was examined following autotomy at the femur/trochanter joint versus severance via a transverse coxa-cut, and 2) the neurophysiology of the detached legs with regard to leg removal type was studied by measuring spike firing rate and microstimulation movement thresholds.Leg Regrowth ResultsFirst appearance of leg regrowth was after 5 weeks in the autotomy group and 12 weeks in the coxa-cut group. Moreover, regenerated legs in the autotomy group were 72% of full size on first appearance, significantly larger (p<0.05) than coxa-cut legs (29% of full size at first appearance). Regenerated legs in both groups grew in size with each subsequent molt; the autotomy-removed legs grew to full size within 18 weeks, whereas coxa-cut legs took longer than 28 weeks to regrow. Removal of the metathoracic leg in both conditions did not have an effect on mortality compared to matched controls with unmolested legs.Neurophysiology ResultsAutotomy-removed legs had lower spontaneous firing rates, similar marked increased firing rates upon tactile manipulation of tibial barbs, and a 10% higher electrical microstimulation threshold for movement.SummaryIt is recommended that neurophysiology experiments on cockroach legs remove the limb at autotomy joints instead of coxa cuts, as the leg regenerates significantly faster when autotomized and does not detract from the neurophysiology educational content.

Biostable insect kinin analogs reduce blood meal and disrupt ecdysis in the blood-gorging Chagas’ disease vector, Rhodnius prolixus

Rhodnius prolixus is a blood-gorging hemipteran that takes blood meals that are approximately 10 times its body weight. This blood meal is crucial for growth and development and is needed to ensure a successful molt into the next instar. Kinins are a multifunctional family of neuropeptides which have been shown to play a role in the control of feeding in a variety of insects. In this study, two biostable Aib-containing kinin analogs were tested to see if they interfere with blood-feeding and subsequent development into the next instar. One of the analogs, 1729 (Ac-R[Aib]FF[Aib]WGa), had no effect on the size of the blood meal or on the subsequent molting of the insect into the next instar. This analog also did not interfere with either short-term or long-term diuresis. The second analog, 1728 ([Aib]FF[Aib]WGa), appeared to be an antifeedant. Insects feeding on blood containing this analog (15μM) only consumed 60% of the blood meal taken by insects fed on blood without analog. Insects feeding on blood containing 1728 had a slower rate of rapid diuresis (diuresis in the first 3–5h after feeding) leading to less urine being excreted by 5days post feeding. The consequence of these effects was that insects fed on 1728 did not molt. This data indicates that the biostable Aib-containing analog 1728 disrupts normal growth and development in the blood-feeding insect, R. prolixus.

Gene Regulation During the Enzootic Cycle of the Lyme Disease Spirochete.

Borrelia burgdorferi, the spirochete that causes Lyme disease, exists in an enzootic cycle, alternating between a tick vector and a vertebrate host. To adapt to and survive the environmental changes associated with its enzootic cycle, including nutrient availability, B. burgdorferi uses three different systems to regulate the expression of genes: RpoN-RpoS, histidine kinase (Hk)1/response regulator 1 (Rrp1), and RelBbu. The RpoN-RpoS alternative sigma factor cascade activates genes required for transmission from the tick to the vertebrate, maintenance of the vertebrate infection, and persistence in the tick. RelBbu controls the levels of the alarmones guanosine pentaphosphate and guanosine tetraphosphate, which are necessary for surviving the nutrient-deficient conditions in the midgut of the tick following absorption of the blood meal and the subsequent molt. The Hk1/Rrp1 two-component system produces cyclic dimeric guanosine monophosphate that regulates the genes required for the transitions between the tick and vertebrate as well as protective responses to the blood meal.

Biological and physiological effects of Coriandrum sativum on House fly Musca domestica (Diptera: Muscidae)

This Study is conducted to evaluate effects of (leaves, fruits) powder and (oil, alcohol) extract of Coriander (Coriandrum sativum) plant on some biological and physiological aspects of House fly, Musca domestica at laboratory conditions. Result show that these preparations caused biological effects represented in high dead percentage in second instar, fed on different concentrations of food treated with them reached to 27.6, 55.3 at concentration 20% of leaf and fruit powder respectively and 67.3, 77.2% at 10% of oil and alcohol extract of fruit, respectively. Furthermore, study also show reduction in pupation and adults emergence percentage. However, leafs powder had slighter effect than powder and extract of fruit of tested plant. The study show physiological effects in treated larvae such as molting failure at subsequent molt to larvae , pupa or to adult, also morphological aberration represented in small size, dark pigment, reduce age and folding of the adult wings. In almost cases, the higher concentration the more morphogenetic aberration. This study leads us to conclude that coriander had chemical compounds which played a negative role in some biological and physiological aspects of house fly.

Ecdysteroids regulate the levels of Molt-Inhibiting Hormone (MIH) expression in the blue crab, Callinectes sapidus.

Arthropod molt is coordinated through the interplay between ecdysteroids and neuropeptide hormones. In crustaceans, changes in the activity of Y-organs during the molt cycle have been regulated by molt-inhibiting hormone (MIH) and crustacean hyperglycemic hormone (CHH). Little has been known of the mode of direct effects of ecdysteroids on the levels of MIH and CHH in the eyestalk ganglia during the molt cycle. This study focused on a putative feedback of ecdysteroids on the expression levels of MIH transcripts using in vitro incubation study with ecdysteroids and in vivo RNAi in the blue crab, Callinectes sapidus. Our results show a specific expression of ecdysone receptor (EcR) in which EcR1 is the major isoform in eyestalk ganglia. The initial elevation of MIH expression at the early premolt stages is replicated by in vitro incubations of eyestalk ganglia with ecdysteroids that mimic the intrinsic conditions of D0 stage: the concentration (75 ng/ml) and composition (ponasterone A and 20-hydroxyecdysone at a 3:1 (w:w) ratio). Additionally, multiple injections of EcR1-dsRNA reduce MIH expression by 67%, compared to the controls. Our data provide evidence on a putative feedback mechanism of hormonal regulation during molting cycle, specifically how the molt cycle is repeated during the life cycle of crustaceans. The elevated concentrations of ecdysteroids at early premolt stage may act positively on the levels of MIH expression in the eyestalk ganglia. Subsequently, the increased MIH titers in the hemolymph at postmolt would inhibit the synthesis and release of ecdysteroids by Y-organs, resulting in re-setting the subsequent molt cycle.

Identification of late larval stage developmental checkpoints in Caenorhabditis elegans regulated by insulin/IGF and steroid hormone signaling pathways.

Organisms in the wild develop with varying food availability. During periods of nutritional scarcity, development may slow or arrest until conditions improve. The ability to modulate developmental programs in response to poor nutritional conditions requires a means of sensing the changing nutritional environment and limiting tissue growth. The mechanisms by which organisms accomplish this adaptation are not well understood. We sought to study this question by examining the effects of nutrient deprivation on Caenorhabditis elegans development during the late larval stages, L3 and L4, a period of extensive tissue growth and morphogenesis. By removing animals from food at different times, we show here that specific checkpoints exist in the early L3 and early L4 stages that systemically arrest the development of diverse tissues and cellular processes. These checkpoints occur once in each larval stage after molting and prior to initiation of the subsequent molting cycle. DAF-2, the insulin/insulin-like growth factor receptor, regulates passage through the L3 and L4 checkpoints in response to nutrition. The FOXO transcription factor DAF-16, a major target of insulin-like signaling, functions cell-nonautonomously in the hypodermis (skin) to arrest developmental upon nutrient removal. The effects of DAF-16 on progression through the L3 and L4 stages are mediated by DAF-9, a cytochrome P450 ortholog involved in the production of C. elegans steroid hormones. Our results identify a novel mode of C. elegans growth in which development progresses from one checkpoint to the next. At each checkpoint, nutritional conditions determine whether animals remain arrested or continue development to the next checkpoint.