Early Juvenile Development Research Articles

The source of microbial transmission influences niche colonization and microbiome development.

Early life microbial colonizers shape and support the immature vertebrate immune system. Microbial colonization relies on the vertical route via parental provisioning and the horizontal route via environmental contribution. Vertical transmission is mostly a maternal trait making it hard to determine the source of microbial colonization in order to gain insight into the establishment of the microbial community during crucial development stages. The evolution of unique male pregnancy in pipefishes and seahorses enables the disentanglement of both horizontal and vertical transmission, but also facilitates the differentiation of maternal versus paternal provisioning ranging from egg development, to male pregnancy and early juvenile development. Using 16S rRNA amplicon sequencing and source-tracker analyses, we revealed how the distinct origins of transmission (maternal, paternal and horizontal) shaped the juvenile internal and external microbiome establishment in the broad-nosed pipefish Syngnathus typhle. Our data suggest that transovarial maternal microbial contribution influences the establishment of the juvenile gut microbiome whereas paternal provisioning mainly shapes the juvenile external microbiome. The identification of juvenile key microbes reveals crucial temporal shifts in microbial development and enhances our understanding of microbial transmission routes, colonization dynamics and their impact on lifestyle evolution.

Extreme polygyny results in intersex differences in age-dependent survival of a highly dimorphic marine mammal.

Developmental differences in vital rates are especially profound in polygamous mating systems. Southern elephant seals (Mirounga leonina) are highly dimorphic and extremely polygynous marine mammals. A demographic model, supported by long-term capture-mark-recapture records, investigated the influence of sex and age on survival in this species. The study revealed clear differences between female and male age-dependent survival rates. Overall juvenile survival estimates were stable around 80-85% for both sexes. However, male survival estimates were 5-10% lower than females in the same age classes until 8 years of age. At this point, male survival decreased rapidly to 50% ± 10% while female estimates remained constant at 80% ± 5%. Different energetic requirements could underpin intersex differences in adult survival. However, the species' strong sexual dimorphism diverges during early juvenile development when sex-specific survival rates were less distinct. Maximizing growth is especially advantageous for males, with size being a major determinant of breeding probability. Maturing males may employ a high-risk high-reward foraging strategy to compensate for extensive sexual selection pressures and sex-specific energetic needs. Our findings suggest sex-specific adult survival is a result of in situ ecological interactions and evolutionary specialization associated with being a highly polygynous marine predator.

Comparisons of cell proliferation and cell death from tornaria larva to juvenile worm in the hemichordate Schizocardium californicum

BackgroundThere are a wide range of developmental strategies in animal phyla, but most insights into adult body plan formation come from direct-developing species. For indirect-developing species, there are distinct larval and adult body plans that are linked together by metamorphosis. Some outstanding questions in the development of indirect-developing organisms include the extent to which larval tissue undergoes cell death during the process of metamorphosis and when and where the tissue that will give rise to the adult originates. How do the processes of cell division and cell death redesign the body plans of indirect developers? In this study, we present patterns of cell proliferation and cell death during larval body plan development, metamorphosis, and adult body plan formation, in the hemichordate Schizocardium californium (Cameron and Perez in Zootaxa 3569:79–88, 2012) to answer these questions.ResultsWe identified distinct patterns of cell proliferation between larval and adult body plan formation of S. californicum. We found that some adult tissues proliferate during the late larval phase prior to the start of overt metamorphosis. In addition, using an irradiation and transcriptomic approach, we describe a genetic signature of proliferative cells that is shared across the life history states, as well as markers that are unique to larval or juvenile states. Finally, we observed that cell death is minimal in larval stages but begins with the onset of metamorphosis.ConclusionsCell proliferation during the development of S. californicum has distinct patterns in the formation of larval and adult body plans. However, cell death is very limited in larvae and begins during the onset of metamorphosis and into early juvenile development in specific domains. The populations of cells that proliferated and gave rise to the larvae and juveniles have a genetic signature that suggested a heterogeneous pool of proliferative progenitors, rather than a set-aside population of pluripotent cells. Taken together, we propose that the gradual morphological transformation of S. californicum is mirrored at the cellular level and may be more representative of the development strategies that characterize metamorphosis in many metazoan animals.

Development of nocturnal feeding and photosensitivity in early juveniles of the warty sea cucumber Stichopus cf. horrens

Behavioral responses to light of early life stages provide insights on the development of photosensitivity in nocturnal species such as Stichopus cf. horrens. In this study, the onset of nocturnal feeding behavior, growth, and survival during early juvenile development (0.56 ± 0.16 cm; 47 days post-settlement) of the species were investigated for 30 days, in the presence (S) or absence (W) of artificial shelters and under three light regimes: constant light (24 L), constant dark (24D), and a 12 -h light, 12 -h dark period (12 L:12D). Juveniles in all treatments fed initially during daytime hours but eventually exhibited a shift to nocturnal feeding by day 11. This behavioral shift to nocturnality was delayed among individuals under constant dark conditions. Continuous light exposure without shelter resulted in low juvenile survival and mass mortality in some replicates of the treatment. In contrast, growth and survival were highest for juveniles in constant dark. This study showed the endogenous control of feeding in this species. It also demonstrated that growth increases significantly when early juveniles are reared with shelters or in constant dark. Optimizing the light regime and type of shelter can improve food accessibility and juvenile growth without hindering the development of photosensitivity in early juveniles. Further studies are needed to enhance the nursery culture of this species.

Paternal exposure to a common herbicide alters the behavior and serotonergic system of zebrafish offspring.

Increasingly, studies are revealing that endocrine disrupting chemicals (EDCs) can alter animal behavior. Early life exposure to EDCs may permanently alter phenotypes through to adulthood. In addition, the effects of EDCs may not be isolated to a single generation − offspring may indirectly be impacted, via non-genetic processes. Here, we analyzed the effects of paternal atrazine exposure on behavioral traits (distance moved, exploration, bottom-dwelling time, latency to enter the top zone, and interaction with a mirror) and whole-brain mRNA of genes involved in the serotonergic system regulation (slc6a4a, slc6a4b, htr1Aa, htr1B, htr2B) of zebrafish (Danio rerio). F0 male zebraFIsh were exposed to atrazine at 0.3, 3 or 30 part per billion (ppb) during early juvenile development, the behavior of F1 progeny was tested at adulthood, and the effect of 0.3 ppb atrazine treatment on mRNA transcription was quantified. Paternal exposure to atrazine significantly reduced interactions with a mirror (a proxy for aggression) and altered the latency to enter the top zone of a tank in unexposed F1 offspring. Bottom-dwelling time (a proxy for anxiety) also appeared to be somewhat affected, and activity (distance moved) was reduced in the context of aggression. slc6a4a and htr1Aa mRNA transcript levels were found to correlate positively with anxiety levels in controls, but we found that this relationship was disrupted in the 0.3 ppb atrazine treatment group. Overall, paternal atrazine exposure resulted in alterations across a variety of behavioral traits and showed signs of serotonergic system dysregulation, demonstrating intergenerational effects. Further research is needed to explore transgenerational effects on behavior and possible mechanisms underpinning behavioral effects.

Warmer waters masculinize wild populations of a fish with temperature-dependent sex determination

Southern flounder (Paralichthys lethostigma) exhibit environmental sex determination (ESD), where environmental factors can influence phenotypic sex during early juvenile development but only in the presumed XX female genotype. Warm and cold temperatures masculinize fish with mid-range conditions producing at most 50% females. Due to sexually dimorphic growth, southern flounder fisheries are dependent upon larger females. Wild populations could be at risk of masculinization from ESD due to globally increasing water temperatures. We evaluated the effects of habitat and temperature on wild populations of juvenile southern flounder in North Carolina, USA. While northern habitats averaged temperatures near 23 °C and produced the greatest proportion of females, more southerly habitats exhibited warmer temperatures (>27 °C) and consistently produced male-biased sex ratios (up to 94% male). Rearing flounder in the laboratory under temperature regimes mimicking those of natural habitats recapitulated sex ratio differences observed across the wild populations, providing strong evidence that temperature is a key factor influencing sex ratios in nursery habitats. These studies provide evidence of habitat conditions interacting with ESD to affect a key demographic parameter in an economically important fishery. The temperature ranges that yield male-biased sex ratios are within the scope of predicted increases in ocean temperature under climate change.

Embryonic and early juvenile development in the Silurian basal nautilid Peismoceras Hyatt, 1894

The family Lechritrochoceratidae Flower, 1950 includes the earliest cephalopods acquiring a lateral pair of retractor muscles—a diagnostic character of the Nautilida. The embryonic shell of Silurian lechritrochoceratids is minute, with a diameter of 2–4 mm, a length of 4.5–7.5 mm and consists of three growth stages: (1) elliptical, dorsoventrally elongated and flattened cicatrix with a central bar, (2) a short, rapidly expanding shell part and (3) a gradually expanding, very slightly curved shell. The sculpture consists of longitudinal lirae, and faintly distinct growth lines or ridges. A ventral lobe formed by ridges corresponds in its course to post-hatching ribs. This lobe indicates the early development of the hyponome in the egg capsule. The hatching is indicated by the appearance of ribs and sometimes also by a change in shell curvature. The juvenile stage is characterised by the prolongation of the body chamber, a change in the shape of the cross section, increasing expansion rate, and by a deepening of the hyponomic sinus. The juveniles were probably demersal with the aperture oriented more or less towards the sea floor. The dorsoventrally elongated cicatrix with a central bar and a depression corresponding to the caecum position and the appearance of longitudinal lirae near the cicatrix margin support systematic position of the lechritrochoceratids among the Nautilida. The hemispherical apex and the very slightly curved embryonic shell, ribbed juvenile shell and narrow annular elevation around the body chamber base, however, call for the definition of a new suborder Lechritrochoceratina.

Hormetic Effects of Early Juvenile Radiation Exposure on Adult Reproduction and Offspring Performance in the Cricket (Acheta domesticus).

Exposure to low-dose ionizing radiation can have positive impacts on biological performance—a concept known as hormesis. Although radiation hormesis is well-documented, the predominant focus has been medical. In comparison, little research has examined potential effects of early life radiation stress on organismal investment in life history traits that closely influence evolutionary fitness (eg, patterns of growth, survival, and reproduction). Evaluating the fitness consequences of radiation stress is important, given that low-level radiation pollution from anthropogenic sources is considered a major threat to natural ecosystems. Using the cricket (Acheta domesticus), we tested a wide range of doses to assess whether a single juvenile exposure to radiation could induce hormetic benefits on lifetime fitness measures. Consistent with hormesis, we found that low-dose juvenile radiation positively impacted female fecundity, offspring size, and offspring performance. Remarkably, even a single low dose of radiation in early juvenile development can elicit a range of positive fitness effects emerging over the life span and even into the next generation.

Energetic changes throughout early ontogeny of the brooding Antarctic sea star Rhopiella hirsuta (Koehler, 1920)

An unusually high proportion of Antarctic echinoderms brood their young. Protection, reproductive constraints, low temperatures and limited food supply are all suggested motives for this reproductive pattern. This study looks at the reproductive energetics of the Antarctic asteroid Rhopiella hirsuta, and to establish the dynamics of feeding and elemental composition throughout its early juvenile development. Brooding females were analysed in terms of adult size, brood size and juvenile size with non-significant trends occurring with depth. Four brooding females were frozen straight after sampling and enabled the study of changes in elemental composition throughout embryo and early juvenile development with regard to their feeding mode. Morphological and elemental analyses indicate aseasonality of reproduction and lecithotrophic early ontogeny in this species. The most advanced juveniles found were significantly different from all earlier stages, with an increase in dry weight (DW) to 5.87 (± 1.08) mg suggesting growth, but a high C:N ratio of 8.60 (± 0.59) that would indicate lecithotrophy. However, as the increase in DW was attributed to an increase in carbon, but not to an increase in nitrogen, it was not possible for the food source to be of organic origin.

Relative Quantitation of Neuropeptides at Multiple Developmental Stages of the American Lobster Using N,N-Dimethyl Leucine Isobaric Tandem Mass Tags

Neuromodulators and neurotransmitters play important roles in neural network development. The quantitative changes of these signaling molecules often reflect their regulatory roles in physiological processes. Currently, several commercial tags (e.g., iTRAQ and TMT) have been widely used in proteomics. With reduced cost and higher labeling efficiency, we employed a set of custom-developed N, N-dimethyl leucine (DiLeu) 4-plex isobaric tandem mass tags as an attractive alternative for the relative quantitation of neuropeptides in brain tissue of American lobster Homarus americanus at multiple developmental stages. A general workflow for isobaric labeling of neuropeptides followed by LC-MS/MS analysis has been developed, including optimized sample handling procedures. Overall, we were able to quantify 18 trace-amount neuropeptides from 6 different families using a single adult brain as a control. The quantitation results indicated that the expressions of different neuropeptide families had significant changes over distinct developmental stages. Additionally, our data revealed intriguing elevated expression of neuropeptides in the early juvenile development stage. The methodology presented here advanced the workflow of DiLeu as an alternative labeling approach and the application of DiLeu-based quantitative peptidomics, which can be extended to areas beyond neuroscience.

Captive Hybridization of the Giant ClamsTridacna maxima(Röding, 1798) andTridacna noae(Röding, 1798)

The giant clam Tridacna noae is a recently resurrected taxon distinguished from Tridacna maxima on the basis of reproductive isolation, mitochondrial DNA differences, and mantle morphology and ornamentation; however, the morphological characteristics used to distinguish the two species are not consistent with genetic assignment throughout their zone of overlap. This has led to the suggestion that hybridization occurs and constituted a need to reexamine the reproductive isolation of T. noae and T. maxima. This study provides evidence that sympatric populations of T. maxima and T. noae in the center of their range overlap and can hybridize and produce juveniles. Breeding trials using T. maxima and T. noae for both maternal and paternal hybrid crosses were conducted to compare larval and early juvenile development. The fertilization success and survival of both hybrid crosses suggest potential for T. maxima and T. noae hybrids to exist in nature. On this basis, the previously reported reproductive isolation between T. maxima and T. noae may not be apposite across their zone of overlap. Future genetic, population demographic, and ecological studies should consider the possibility of hybridization between T. maxima and T. noae.

Behavioral development in embryonic and early juvenile cuttlefish (Sepia officinalis)

Though a mollusc, the cuttlefish Sepia officinalis possesses a sophisticated brain, advanced sensory systems, and a large behavioral repertoire. Cuttlefish provide a unique perspective on animal behavior due to their phylogenic distance from more traditional (vertebrate) models. S. officinalis is well-suited to addressing questions of behavioral ontogeny. As embryos, they can perceive and learn from their environment and experience no direct parental care. A marked progression in learning and behavior is observed during late embryonic and early juvenile development. This improvement is concomitant with expansion and maturation of the vertical lobe, the cephalopod analog of the mammalian hippocampus. This review synthesizes existing knowledge regarding embryonic and juvenile development in this species in an effort to better understand cuttlefish behavior and animal behavior in general. It will serve as a guide to future researchers and encourage greater awareness of the utility of this species to behavioral science.

Stability of facial scale patterns on green sea turtles Chelonia mydas over time: A validation for the use of a photo-identification method

Photographic identification (photo-ID) has been increasingly used as a reliable tool to track individuals over time, which provides essential knowledge on a species' population dynamics. For photo-ID to work, natural markings must be individual-specific and stable over time. In sea turtle research, the use of facial scale patterns has been proposed and tested as a reliable means for individual recognition. Nevertheless, as sea turtles are migratory and long-lived individuals, the stability of those patterns over long periods of time is yet to be confirmed to validate this method. Stability of facial scale patterns was evaluated on green sea turtles, Chelonia mydas, sighted and photographed in coastal waters of Reunion Island (21°06 S, 55°36 E) or reared in captivity. From 53 free-ranging individuals previously identified, 90 head profiles were selected based on the photographic quality and the distinctiveness of facial scale patterns. The time interval between two sightings of a same individual ranged from 2 (738d) to 11years (3954d). Additionally, facial scale patterns of captive green turtles from two different age groups were compared: (1) from adult-sized individuals reared in captivity (n=13) and (2) from hatchlings and then at later developmental stages (until 1800d) to assess the stability of facial scale patterns throughout early juvenile development (n=16). In both the free-ranging and captive-reared groups, there were no significant changes in facial scale patterns over time. Conversely, changes in pigmentation were observed in free-ranging turtles at successive sightings and in captive-reared turtles at different developmental stages. These results on the stability of facial scale patterns over time, combined with previous findings on the uniqueness of patterns between individual green turtles, validate the method of using facial scale patterns as a long-term identification tool for green turtles. Nonetheless, the variability of pigmentation patterns should be kept in mind when using photo-identification on sea turtle species.

Growth and Burrowing Rates of Juvenile GeoducksPanopea generosaandPanopea globosaunder Laboratory Conditions

ABSTRACT The burrowing behavior, growth, and size-dependent burrowing rates of two geoduck species—Panopea globosa and Panopea generosa—from the Mexican coast were assessed during early juvenile development (6–7 mo) using 30-L aquariums with a muddy or sandy sediment substrate. Preburial response time, digging rates, and growth were recorded monthly for organisms with an initial shell length of 5 mm (P. globosa) or 10mm (P. generosa), and continued for 6 or 7 mo. Organisms were fed Isochrysis sp. (clone T-ISO) at libitum on a daily basis during the experimental period. Digging behaviors included the inflation of the geoduck siphon, followed by expulsion of a water jet through the pedal orifice, in conjunction with coordinated muscular contractions of the foot. Both species exhibited a lag in their burial response time that was related linearly to shell length, with rates of 4.5 min/mm (P. globosa) and 3.4 min/mm (P. generosa). Burrowing rates were independent of shell length and were similar in both speci...

Early development and growth of sterlet (Acipenser ruthenus) in the Czech Republic

Growth rate of sterlet larvae and juveniles during 2008 and 2009 was studied under experimental and farming conditions in the Czech Republic. The embryos hatched when reaching a mean total length (TL) of 9.0 mm. Larvae were fed by living food, with a gradual transition to dry diet. The exogenous feeding and the larval period of ontogeny started at DAH 9 (day after hatching) reaching TL of 15–17 mm accompanied by melanin plug exclusion. Towards the end of larval period (DAH 39–43, TL 50–58 mm), the embryonic finfold disappeared and the formation of fin apparatus was nearly completed. During the larval and early juvenile development, daily increments of TL and weight (w) ranged between 0.33–4.23 mm.d−1 and 0.0018–1.6400 g.d−1, respectively. The specific growth rate (SGR) ranged from 25.65 to 2.73 %.d−1. Growth intensity and length parameters are similar to the Starry sturgeon, lower than those of the Siberian sturgeon and Russian sturgeon and significantly lower than at Beluga sturgeon. Sterlet’s Fulton weight condition factor (FWC) was higher than in the Siberian and Starry sturgeon. The development was also observed on the basis of morphological changes. The larval development could be divided into six steps.

Metamorphosis in Craniiformea revisited: Novocrania anomala shows delayed development of the ventral valve

We revisited the brachiopod fold hypothesis and investigated metamorphosis in the craniiform brachiopod Novocrania anomala. Larval development is lecithotrophic and the dorsal (brachial) valve is secreted by dorsal epithelia. We found that the juvenile ventral valve, which consists only of a thin layer that was previously described as periostracal, is not a valve and is not secreted by the same epithelia as the dorsal valve. It is secreted by the attachment area of the larva at the posterior-most tip of the posterior larval lobe. The same attachment area is used by larvae of rhynchonelliform brachiopods during metamorphosis to cement their pedicle to the substrate. N. anomala is therefore not initially attached by a valve but by material corresponding to pedicle cuticle. This is different to previous descriptions, which had led to speculations about a folding event in the evolution of Brachiopoda. We show that the “brachiopod fold hypothesis,” which argues that brachiopods are transversely “folded” across the ontogenetic anterior–posterior axis, should be rejected at least with respect to the craniiforms. The data now suggest that the Craniiformea may be a derived group within the Rhynchonelliformea. This interpretation suggests that the last common ancestor of the Craniiformea has lost the pedicle and the ventral valve in early juvenile development. Characters that have previously been considered to be shared between the Craniiformea and the Linguliformea (clade Inarticulata), such as a through-gut and missing hinge articulation, may thus be secondarily derived characters of the Craniiformea within the Rhynchonelliformea.

Temperature and salinity interactively impact early juvenile development: a bottleneck in barnacle ontogeny

When juvenile mortality or juvenile growth is impacted by temperature and salinity, these factors have a substantial effect on recruitment success and population dynamics in benthic ecosystems. Using freshly settled cyprids of Amphibalanus improvisus, we investigated the combined effects of temperature (12, 20 and 28 °C) and salinity (5, 15 and 30 psu) on early juvenile stage performance. Mortality as well as size (basal diameter, dry weight, and ash-free dry weight) was monitored for a period of 40 days. Mortality was high (42–63 %) during the first week following attachment, regardless of the temperature and salinity treatments. Subsequently, mortality and size were interactively influenced by temperature and salinity. Highest mortality and lowest size of juveniles occurred at lowest temperature (12 °C) and salinity (5 psu). Apparently, low temperature (12 °C) narrowed the barnacles’ salinity tolerance. Juvenile barnacles constructed more shell material compared to body mass at high temperature and high salinity, while a reverse situation was observed at low temperature and low salinity. Our results demonstrate that environmental changes can directly and/or indirectly alter patterns of survivorship and size. Warming and desalination as predicted for the Baltic Sea in the course of climate change may, however, act antagonistically and compensate each other’s isolated effect on barnacles.

Carry-over effects of delayed larval metamorphosis on early juvenile performance in the mangrove crab Ucides cordatus (Ucididae)

Competent larvae of most benthic marine invertebrates including brachyuran decapod crustaceans can delay their settlement and metamorphosis in the absence of suitable environmental cues. This however may carry significant costs for the post-larval performance and fitness of early benthic juveniles. In this paper, we examined in the laboratory whether delayed larval metamorphosis affects early juvenile performance of the mangrove crab Ucides cordatus, measured as survival and growth through the first five juvenile crab stages (JI–JV). We further investigated whether ‘carry-over’ effects of an extended larval period vary intraspecifically among juveniles from three different hatches (F1–F3). Ucides megalopae were cultivated in two treatments. In the first one, the control, megalopae were cultivated continuously in exposure to conspecific crab odours (adult-conditioned seawater=ACSW) until moulting to the first juvenile crab stage. In the second, the delay-treatment, settlement-competent megalopae were kept for 20days in pure filtered seawater without metamorphosis-triggering odours. From day 21 onwards, megalopae were transferred to ACSW to induce larval moult. The results showed that delayed metamorphosis affects early juvenile survival and growth of U. cordatus. In the delay-treatment, survival rates of juveniles (JI–JV) from F1–F3 were 11–31% lower and intermoult development periods 1.5–4.2days longer than in the control. Delayed juveniles (F1–F3) exhibited 9.2–14.1% smaller body sizes (carapace width) and 1.4–3.9% lower growth rates mostly in the first two moulting events compared to specimens derived from non-delayed megalopae. Most of the detrimental effects were observed in almost all five crab stages studied, indicating that the costs of delayed metamorphosis may persist throughout early juvenile development. Juvenile morphology, however, was not affected. Our study also showed that carry-over effects of delayed larval moult vary intraspecifically among offspring produced by different females. This plasticity in phenotypic effects could relate to differences in the nutritional state, health or age of the females, to stressful environments during embryogenesis or to genetic differences. The observed carry-over effects of delayed settlement on early juvenile performance may affect the overall recruitment success and population dynamics of U. cordatus. In the field, such a situation would appear when new mangrove areas void of conspecific crabs are colonized or when degraded sites are re-populated by larvae originating from elsewhere populations.

The Good, the Bad and the Plenty: Interactive Effects of Food Quality and Quantity on the Growth of Different Daphnia Species

Effects of food quality and quantity on consumers are neither independent nor interchangeable. Although consumer growth and reproduction show strong variation in relation to both food quality and quantity, the effects of food quality or food quantity have usually been studied in isolation. In two experiments, we studied the growth and reproduction in three filter-feeding freshwater zooplankton species, i.e. Daphnia galeata x hyalina, D. pulicaria and D. magna, on their algal food (Scenedesmus obliquus), varying in carbon to phosphorus (C∶P) ratios and quantities (concentrations). In the first experiment, we found a strong positive effect of the phosphorus content of food on growth of Daphnia, both in their early and late juvenile development. Variation in the relationship between the P-content of animals and their growth rate reflected interspecific differences in nutrient requirements. Although growth rates typically decreased as development neared maturation, this did not affect these species-specific couplings between growth rate and Daphnia P-content. In the second experiment, we examined the effects of food quality on Daphnia growth at different levels of food quantity. With the same decrease in P-content of food, species with higher estimated P-content at zero growth showed a larger increase in threshold food concentrations (i.e. food concentration sufficient to meet metabolic requirements but not growth). These results suggest that physiological processes such as maintenance and growth may in combination explain effects of food quality and quantity on consumers. Our study shows that differences in response to variation in food quality and quantity exist between species. As a consequence, species-specific effects of food quality on consumer growth will also determine how species deal with varying food levels, which has implications for resource-consumer interactions.

The early life history of Chiromantes ortmanni (Crosnier, 1965) (Decapoda: Brachyura: Sesarmidae): morphology of larval and juvenile stages

The early life history of the sesarmid crab Chiromantes ortmanni (Crosnier, 1965) was studied at constant laboratoryconditions, and the complete larval and early juvenile development are described. Chiromantes ortmanni showsintraspecific variability in the pattern of larval development, which typically includes 5 or, less frequently, 6 zoeal stagespreceding the megalopa. The regular pathway (with 5 zoeal stages) required ca 18–20 days. During this time span, zoealsize (carapace length) increased by a factor of 2.2 from 0.33 to 0.73 mm, while biomass (measured as zoeal dry mass andcontents of carbon, nitrogen and hydrogen) showed an 8-fold increment. The megalopa moulted after 10–12 days to thefirst juvenile crab stage, the total larval development from hatching to metamorphosis taking approximately one month(or ca. 4 days longer in larvae passing through an additional zoeal stage). First egg-laying was observed 8.5 months later,at a female carapace width of 14.4 mm. After an embryonic development time of 26–27 days, a total of 3,470 larvaehatched during two subsequent nights. Hence, the minimum generation time (from hatching to first offspring release)comprised slightly more than 10 months. Unlike the regular zoeal stages, the supernumerary stage VI showed atypicalcharacters for Sesarmidae larvae, especially in the setation pattern of the first maxilliped and the segmentation of theendopod of the second maxilliped. Some characteristics presented an intermediate morphology between that of the zoeaV and the megalopa. The first juvenile stage (crab I) is described in detail, while only the most relevant morphologicalchanges and sexual differentiation are highlighted for subsequent crab stages (II–IX). Males and females can bedistinguished from instar V onward, based on sexual dimorphism in the pleopods and the presence of gonopores in thefemales. The morphological characters of all larval stages and of the first juvenile crab are compared with those of other Chiromantes spp.