European Lobster Homarus Gammarus Research Articles

Activity patterns of wild European lobster Homarus gammarus in coastal marine reserves: implications for future reserve design

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 429:197-207 (2011) - DOI: https://doi.org/10.3354/meps09102 Activity patterns of wild European lobster Homarus gammarus in coastal marine reserves: implications for future reserve design Even Moland1,*, Esben Moland Olsen1,2, Halvor Knutsen1,2, Jan Atle Knutsen3, Svein Erik Enersen1, Carl André4, Nils Chr. Stenseth2 1Institute of Marine Research, Nye Flødevigvei 20, 4817 His, Norway 2Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biology, University of Oslo, PO Box 1066 Blindern, 0316 Oslo, Norway 3Department of Environment, County Governor of Aust-Agder, PO Box 788 Stoa, 4809 Arendal, Norway 4Department of Marine Ecology-Tjärnö, University of Gothenburg, 452 96 Strömstad, Sweden *Email: even.moland@graduates.jcu.edu.au ABSTRACT: European lobster Homarus gammarus in Norway has been in decline over the last 30 to 40 yr, and the species is currently red listed according to International Union for Conservation of Nature criteria. In 2006, experimental lobster reserves were established in the coastal Skagerrak, southern Norway, allowing for studies in the absence of disturbance by fishing gear. We present behavioural data from individual lobsters (n = 10) within 2 of the reserves. These data were obtained from data storage tags which logged in situ temperature and depth of specific individuals for up to 1 yr. To the best of our knowledge, these are the first direct measurements of depth obtained from freely behaving lobsters. Net movement exhibited by recaptured lobsters, measured as the distance between global positioning system positions recorded at the site of capture and recapture ranged from 15 to 580 m. Lobsters used habitats within a depth range of 1 to 57 m, and experienced sea temperatures ranging from 2°C during late winter (February to March) to 18°C during late summer (August to September). ­Lobster activity levels declined from September, reaching a minimum during February and March. From April, activity levels resumed. Seasonal variation in activity was correlated to water temperature (r2 = 0.55). Lobsters were more active during nighttime than during daytime, and there was a tendency for lobsters to reside in more shallow water during nighttime versus daytime. The present study suggests that future reserves for European lobster should be designed to include deeper habitat (30 to 50 m) in areas where such habitat exists when the management objective is long-term ­protection. KEY WORDS: Archival tag · Behaviour · Marine reserve design · Diel rhythm · Data storage tag · Decapoda · Data storage tag · DST Full text in pdf format PreviousNextCite this article as: Moland E, Moland Olsen E, Knutsen H, Knutsen JA, Enersen SE, André C, Stenseth NC (2011) Activity patterns of wild European lobster Homarus gammarus in coastal marine reserves: implications for future reserve design. Mar Ecol Prog Ser 429:197-207. https://doi.org/10.3354/meps09102 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 429. Online publication date: May 16, 2011 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2011 Inter-Research.

Estimating Recreational and Commercial Fishing Effort for European LobsterHomarus gammarusby Strip Transect Sampling

AbstractRecreational fishing effort for coastal marine species can be significant but is often challenging to estimate. Here we present a case study where a probability‐based strip transect survey is used to estimate effort in the Norwegian fishery for European lobsterHomarus gammarus. This fishery is conducted by both recreational and commercial fishers, but reliable information on total fishing effort and total catch is lacking. In 2008, we conducted a strip transect sampling survey throughout the lobster fishing season in southern Norway to estimate the number of deployed lobster traps over time. Surface buoys marking lobster traps were counted along strip transects placed representatively in the survey area in five different weeks throughout the lobstering season. Calibration studies were conducted to standardize transect width and to estimate and adjust for detection rates of buoys along transect strips. Mean number of lobster traps per square kilometer and associated variance was estimated by a ratio estimator using bootstrapping, with transects as the primary sampling units. Poststratification of the counts by depth (by 10‐m depth intervals) combined with geographical information systems mapping improved the precision of the estimated density of lobster traps and increased the effective sample size of transects by 22–44% per week. Estimated daily effort for the first week was 48.95 (SE = 3.11) traps/km2, decreasing steadily to 5.96 (SE = 0.79) in the eighth (and last) week of the lobster season. Our study shows that lobster traps deployed by recreational fishers outnumber the ones deployed by commercial fishers, contributing to 65% of the total effort (number of traps) in the fishery. We show that strip transects are a suitable way to estimate effort in the Norwegian lobster fishery. We conclude that improved management efforts need to target recreational as well as commercial fishing activities in order to achieve effective management of the red‐listed species.Received August 5, 2010; accepted July 5, 2011

Maternal influences on offspring size variation and viability in wild European lobster Homarus gammarus

In many marine species, large females tend to produce more robust offspring than small females. However, knowledge on maternal influences in decapod crustaceans is limited. This is unfortunate since many decapod populations are being intensively harvested and show signs of 'juvenescence', i.e. the loss of large (and presumably old) individuals. In this study, we quantified maternal influences in European lobster Homarus gammarus from Skagerrak, southern Norway. His- torical lobster catches in Skagerrak were substantial but the stock has suffered a major decline over the past 30 to 40 yr and is currently red listed as near threatened according to the IUCN (International Union for Conservation of Nature) criteria. We studied eggs and larvae from wild-caught ovigerous females ranging in carapace length from 79 to 152 mm (n = 45). Mean egg size increased while sib- ling size variation decreased significantly with increasing maternal size. Mean larval size at hatching was closely linked to both maternal size and mean egg size. A laboratory experiment showed a weak but significant nonlinear increase in pelagic larval survival with increasing mean egg size in the absence of food. These findings suggest that maternal influences on offspring quality could be a sig- nificant source of variation in lobster recruitment. Consequently, maternal influences could be an important source of error in fisheries science and management if they are assumed to be absent or unimportant.

Description of the IMR Standard Light Trap and the Vertical Distribution of Some Decapod Larvae (Homarus and Nephrops)

The construction of different versions of a cheap, robust, and easy to operate light trap for catching various aquatic organisms is shown. The trap can be used to > 300 m depth and meets a number of criteria. Small-scale vertical distribution of decapod larvae was investigated during trap trials. The traps (6-10) were set for 24 h at different depths, once a week, between 25 July and 28 September 2006, within the Kåvra lobster reserve at the Swedish west coast. This is an area with low salinity in the surface water during summer due to outflow of water from the Baltic Sea. The larvae of the European lobster Homarus gammarus (stage I) and Norway lobster Nephrops norvegicus (stages I-III) were found within and below the thermo- and haloclines. No larvae were found within the upper 2 m. This finding may have important bearings on the larval transport by currents and increase the possibility for retention of larvae, but was not tested inthis study. The highest catches of both H. gammarus and N. norveigicus were obtained during August. The trap appears to be well suited for investigating small-scale vertical distribution during the dark period, and for collecting animals in good condition. However, the trap did notcatch all larval stages, and the relation between light intensity (both natural and trap light) and catch ability is unknown.

An approach to the assessment of risk from chronic radiation to populations of European lobster, Homarus gammarus (L.)

The basic principles underlying a four-discrete age group, logistic, growth model for the European lobster Homarus gammarus are presented and discussed at proof-of-concept level. The model considers reproduction, removal by predation, natural death, fishing, radiation and migration. Non-stochastic effects of chronic low linear energy transfer (LET) radiation are modelled with emphasis on (99)Tc, using three endpoints: repairable radiation damage, impairment of reproductive ability and, at higher dose rates, mortality. An allometric approach for the calculation of LD(50/30) as a function of the mass of each life stage is used in model calibration. The model predicts that at a dose rate of 1 Gy day(-1), lobster population reproduction and survival become severely compromised, leading eventually to population extinction. At 0.01 Gy day(-1), the survival rate of an isolated population is reduced by 10%, mainly through loss of fecundity, comparable to natural migration losses. Fishing is the main ecological stress and only dose rates in the range 0.03-0.1 Gy day(-1) can achieve discernible effects above it. On the balance of radiation and other ecological stresses, a benchmark value of 0.01 Gy day(-1) is proposed for the protection of lobster populations. This value appears consistent with available information on radiation effects in wildlife.

Effect of CO<sub>2</sub>-related acidification on aspects of the larval development of the European lobster, <i>Homarus gammarus</i> (L.)

Abstract. Oceanic uptake of anthropogenic CO2 results in a reduction in pH termed "Ocean Acidification" (OA). Comparatively little attention has been given to the effect of OA on the early life history stages of marine animals. Consequently, we investigated the effect of culture in CO2-acidified sea water (approx. 1200 ppm, i.e. average values predicted using IPCC 2007 A1F1 emissions scenarios for year 2100) on early larval stages of an economically important crustacean, the European lobster Homarus gammarus. Culture in CO2-acidified sea water did not significantly affect carapace length of H. gammarus. However, there was a reduction in carapace mass during the final stage of larval development in CO2-acidified sea water. This co-occurred with a reduction in exoskeletal mineral (calcium and magnesium) content of the carapace. As the control and high CO2 treatments were not undersaturated with respect to any of the calcium carbonate polymorphs measured, the physiological alterations we record are most likely the result of acidosis or hypercapnia interfering with normal homeostatic function, and not a direct impact on the carbonate supply-side of calcification per se. Thus despite there being no observed effect on survival, carapace length, or zoeal progression, OA related (indirect) disruption of calcification and carapace mass might still adversely affect the competitive fitness and recruitment success of larval lobsters with serious consequences for population dynamics and marine ecosystem function.

Nutritional Quality of the Edible Tissues of European Lobster Homarus gammarus and American Lobster Homarus americanus

The clawed lobsters Homarus gammarus and Homarus americanus are high-priced and appreciated food items in southern Europe. From a nutritional point of view there is still limited information on the chemical composition of edible tissues (muscle, hepatopancreas, and gonads) of both species. Therefore, the aims of the present work were to study the proximate chemical composition, energy, fatty acid and amino acid profiles, and cholesterol content in each edible tissue of both species and to evaluate their nutritional quality. Differences were observed between tissues, sexes, and species. Muscle and gonads were rich in protein, whereas hepatopancreas had high fat, cholesterol, and energy contents. All edible tissues were valuable sources of essential amino acids. Contrary to the common belief that shellfish consumption should be reduced in a low-fat and -cholesterol diet, all edible tissues of clawed lobsters have a nutritious value perfectly compatible with nutritious and healthy diets.

Sexual and aggressive interactions in a mixed species group of lobsters Homarus gammarus and H. americanus

The introduction of non-native populations can have dramatic effects on the native fauna as a result of interbreeding and aggressive interference between closely related species. This study investigates if female European lobsters Homarus gammarus would sexually interact and mate with male American lobsters Homarus americanus, recently introduced to Norwegian waters, if given the choice between the heterospecific and a conspecific male. Interactions between a mixed species pair of male lobsters and a single H. gammarus female were recorded during 1 wk periods in a large tank provided with 2 shelters. Trials included either dominant H. americanus or dominant H. gammarus males. The frequency and duration of social interactions such as aggression, shelter visits, shelter shar- ing, courtship and mating were analysed. Conspecific courtship occurred in 10 trials, and mating, in 5 trials. No sexual interactions occurred between species. H. gammarus females preferred to court and mate with a conspecific male irrespective of its dominance status. In addition, the H. americanus males showed no sexual response to the European females. Females visited conspecific male shelters more frequently than heterospecific male shelters. They received longer visits from the conspecific than from the heterospecific male. Conspecific pairs shared shelters more frequently and over longer peri- ods of time than heterospecific pairs. Conspecific shelter sharing often included courtship, while heterospecific interactions were generally of aggressive nature, with lobsters fighting over shelter. The results suggest that European lobsters are able to recognize conspecific mates, perhaps by chem- ical signals, and that these signals serve as pre-mating barriers preventing hybridisation.

Potential of Stock Enhancement for Decapod Crustaceans

To evaluate the potential of stock enhancement for decapod crustaceans, we analyzed stock enhancement programs for 4 species: the penaeid prawns (Penaeus japonicus) in Japan and (Penaeus chinensis) China, the European lobster (Homarus gammarus) in Norway, and the mud crab (Scylla paramamosain) in Japan, for which stocking effectiveness has been intensively examined. For each species, we summarized the life cycle, fishery, and stocking programs and then comparatively analyzed the recapture rates, the yield from the released individuals (YPR), and the economic efficiency. Scylla paramamosain had some advantages in stock enhancement, including restricted living areas such as bays and estuaries, a large body size, and high values of the ratio of price per landed individual to the cost per released juvenile. These characteristics promised higher values of YPR and economic efficiency, even at lower recapture rates. Therefore, hatchery releases affect areas with small stocks of S. paramamosain. This scenario might also be inferred for H. gammarus, which had the highest YPR and does not generally migrate from the release site, although the economic efficiency was low due to the high cost of juvenile production. On the other hand, fishery productions of the penaeid prawns, which had a lower YPR, could not be augmented without a huge number of released juveniles and the maintenance of nursery habitats. The restocking is a more cost-effective measure for sustainable fishery production than only a sea ranching (put and take) operation. Therefore, hatchery releases for decapod crustaceans should be applied to rebuild wild stocks (restocking) with appropriate fishing regulations and habitat restoration. In the future, selection of target species for stock enhancement programs should take into account the necessity for restocking and their life history characteristics.

Hatchery production of European lobster (Homarus gammarus, L.): broodstock management and effects of different holding systems on larval survival

The biometry of wild berried females was collected during an entire reproductive season at the South-Wexford Lobster Co-op hatchery in Nethertown, Ireland. Second degree regressions between total body weight (TW, g) and carapace length (CL, mm) (TW=CL2 -36.675CL+1793.2, R2=0.9022) and number of ,“weaned” larvae and carapace length (Larvae number=1.217CL2–21.777CL-5281.1, R2 =0.743) were observed. Afterwards, berried females were divided according to two variables: 1. holding system: recirculating system (Rs) vs barrel (Bar); 2. CL size: <101 mm (A), 101-120 mm (B), >120 mm (C). The total weight of larvae (212.5 vs 92.4 g) and their numbers (7788 vs 5679) were significantly higher for the largest females than for the smaller sizes (P<0.01). The maximum survival rate of larvae (77.86%) was noted for initial stocking density <1000 individuals/hopper, but the optimal stocking density for management purposes in the hatchery is higher (2001-3000 individuals/hopper).

Identification and characterization of a cDNA encoding a crustin-like, putative antibacterial protein from the American lobster Homarus americanus

Pathogenic challenges in decapod crustaceans are combated by innate immune responses, including the production and secretion of soluble antibacterial proteins into the hemolymph. Among the antibacterials that have been identified in decapod species are the crustins, a group of four-disulfide core/whey-acidic-protein (WAP) domain-containing proteins, which target marine/salt tolerant Gram-positive bacteria. To begin to assess the possible role of crustins in combating bacterial invasion in the American lobster Homarus americanus, we identified and sequenced a 744 base pair cDNA that encodes a novel 96 amino acid crustin-like protein. Comparison of H. americanus crustin (Hoa-crustin) with crustins from other decapod species showed that it is most similar to an isoform predicted from the European lobster Homarus gammarus (∼86% identity). With our identification of the Hoa-crustin cDNA, we are positioned to begin molecular and physiological investigations of the regulation and function of this putative antibacterial protein in H. americanus.

Cloning and characterisation of a prophenoloxidase from the haemocytes of mud crab Scylla serrata

A prophenoloxidase (proPO) cDNA was cloned from the haemocytes of mud crab Scylla serrata using oligonucleotide primers and RT-PCR. Both 3′- and 5′-regions were isolated by rapid amplification of cDNA end (RACE) method. Analysis of the nucleotide sequence revealed that the cDNA clone has a full length of 2663 bp, with an open reading frame of 2019 bp, a 124-bp 5′-untranslated region, and a 520-bp 3′-untranslated region containing a poly A signal. It encodes a protein of 673 amino acids with a predicted molecular weight of 77.5 kDa and with an estimated p I of 5.96. It contains two putative tyrosinase copper-binding motifs with six histidine residues (copper A, 185, 189, 211, and copper B, 346, 350, 386). The proPO has thiol-ester-like motif (GCGWPQHM), which showed similar structural features of proPOs from other decapod crustaceans. It also contains five possible glycosylation sites, and a conserved C-terminal region common to all known proPOs. Sequence comparison showed that the proPO-deduced amino acid of mud crab S. serrata has an overall similarity of 78%, 57%, 56%, 51–55%, 54%, 53%, 52%, 52%, and 52% to that of Dungeness crab Cancer magister, American lobster Homarus americanus, European lobster Homarus gammarus, kuruma prawn Marsupenaeus japonicus, crayfish Pacifastacus leniusculus, white shrimp Litopenaeus vannamei, tiger shrimp Penaeus monodon, green tiger shrimp Penaeus semisulcatus, and giant freshwater prawn Macrobrachium rosenbergii, respectively. The proPO was strongly expressed in haemocytes, but not in heart, eyestalk, gill, muscle, ovary, hepatopancreas, stomach, and intestine. The proPO transcript of mud crab S. serrata increased significantly in 12 and 24 h post-lipopolysaccharide (LPS) injection, but returned to the original values in 72 h post injection.

Crustacean hyperglycemic and vitellogenesis‐inhibiting hormones in the lobster Homarus gammarus

Crustacean hyperglycemic hormone (CHH) and vitellogenesis-inhibiting hormone (VIH), produced by the X organ-sinus gland neurosecretory complex, belong to a peptide group referred to as the CHH family, which is widely distributed in arthropods. In this study, genetic variants and post-translationally modified isoforms of CHH and VIH were characterized in the European lobster Homarus gammarus. With the use of RP-HPLC and ELISA with specific antibodies that discriminate between stereoisomers of CHH and VIH, two groups of CHH-immunoreactive peaks were characterized from HPLC fractions of sinus gland extract (CHH A and CHH B); each group contained two variants (CHH and D-Phe3CHH). In the same way, two VIH-immunoreactive peaks (VIH and D-Trp4VIH) were demonstrated in HPLC fractions from sinus gland extract. The masses of these different neuropeptides were determined by FT-ICR MS: CHH A and CHH B spectra exhibited monoisotopic ions at 8557.05 Da and 8527.04 Da, respectively, and both VIH isomers displayed an m/z value of 9129.19 Da. Two full-length cDNAs encoding preprohomones of CHH A and CHH B and only one cDNA for VIH precursor were cloned and sequenced from X organ RNA. Comparison of CHH sequences between European lobster and other Astacoidea suggests that the most hydrophobic form appeared first during crustacean evolution.

A Potential Method for Discriminating Between Tissue from the European Lobster (Homarus Gammarus) and the American Lobster (H. Americanus)

A Potential Method for Discriminating Between Tissue from the European Lobster (Homarus Gammarus) and the American Lobster (H. Americanus)

The Carotenoproteins During Embryogenesis and Larval Development of the European Lobster Homarus Gammarus

Abstract Embryos and larvae of the european lobster H. gammarus, reared under laboratory conditions, were investigated in order to determine the nature and metabolism of carotenoproteins during embryogenesis. Extracts of embryonic as well as larval stages were analysed, using DEAE-Cellulose filtration, electrophoresis, and thin layer chromatography. Ovoverdin is the main carotenoprotein of the yolk; two fractions, having different molecular weight (No1: 700 kDa and No2: 600 kDa) were observed. Larval extracts were found to contain three coloured carotenoproteins: blue (Lm1a), red (Lm1b), and yellow (Lm1c). Yolk carotenoids were identified as free astaxanthin and unesterified phoenicoxanthin, whereas esterified astaxanthin was found to occur in the forming tissues. Astaxanthin diester is the main carotenoid of the embryo; in larval tissues, this carotenoid is associated to the red carotenoprotein. The increase in esterified astaxanthin suggests enzymatic mechanisms leading to acylation reactions occurring ...

Growth of tissues related to haemolymph copper throughout the moult cycle of the lobster Homarus gammarus

The relationship between tissue weights and haemolymph copper levels in field-collected European lobsters Homarus gammarus was investigated to assess whether haemolymph copper concentration can be used to reliably determine nutritional condition in lobsters. During the moult cycle, the soft tissue weight (mostly muscle) increased concomitantly with a decrease in haemolymph weight while exoskeleton weight increased from postmoult to intermoult. Haemolymph copper concentration gradually increased from postmoult to premoult with a range of 29.7 (Stage B) to 163.5 pg g -1 wet weight (ww) (Stage D 0 ). Our measurements suggest that the main processes that increase haemolymph copper concentration is a reduction in haemolymph space and an increase in haemolymph copper content, indicating synthesis of new haemocyanin for the oxygen supply of growing tissues. During the moult cycle, haemolymph copper content was proportional to soft tissue mass and amounted to 43.6 pg Cu g -1 of soft-tissue ww (95% confidence limits = 35.5 and 51.6 μg g -1 ). Models for estimating soft-tissue and haemolymph wet weights from the haemolymph copper concentration and moult stage are presented. The use of haemolymph copper concentration as an index of nutritional condition reflecting tissue growth and food quantity and quality is validated.

Immunolocalization of NA(+),K(+)-ATPase in the branchial cavity during the early development of the European lobster Homarus gammarus (Crustacea, Decapoda).

We examined the ontogeny of the osmoregulatory sites of the branchial cavity in embryonic and early postembryonic stages of the European lobster Homarus gammarus through transmission electron microscopy, immunofluorescence microscopy, and immunogold electron microscopy using a monoclonal antibody IgGalpha(5) raised against the avian alpha-subunit of the Na(+),K(+)-ATPase. In mid-late embryos, Na(+),K(+)-ATPase was located along the pleurites and within the epipodite buds. In late embryos just before hatching, the enzyme was confined to the epipodite epithelia. After hatching, slight differentiations of ionocytes occured in the epipodites of larval stages. Na(+),K(+)-ATPase was also located in the ionocytes of the epipodites of larvae exposed to seawater (35.%o) and to dilute seawater (22.1 %o). After metamorphosis, the inner-side branchiostegite epithelium appeared as an additional site of enzyme location in postlarvae held in dilute seawater. Within the ionocytes, Na(+),K(+)-ATPase was mostly located along the basolateral infoldings. These observations are discussed in relation to the physiological shift from osmoconforming larvae to slightly hyper-regulating (in dilute seawater) postmetamorphic stages. The acquisition of the ability to hyper-osmoregulate probably originates from the differentiation, on the epipodites and mainly along the branchiostegites, of ionocytes that are the site of ion pumping as evidenced by the location of Na(+),K(+)-ATPase.

Morphometric variability in UK populations of the European lobster

European lobsters (Homarus gammarus) were sampled from nine sites around the UK coast to determine whether populations could be differentiated on the basis of morphometric variability, and to relate this to depth and indices of population size at each site. Discriminant analysis indicated that exoskeleton damage was the only characteristic that could distinguish males between sites. In contrast, females were distinguished between sites on the basis of variation in exoskeleton damage, claw spines and rostrum teeth, which tended to be positively correlated to indices of population density. This study suggests that female morphology may respond more strongly than male morphology to local selection pressures, albeit in a limited capacity.

Growth, feeding frequency, protein turnover, and amino acid metabolism in European lobster Homarus gammarus L.

The effect of feeding frequency on growth and protein metabolism in the European lobster, Homarus gammarus, was investigated. Fourth (IV) stage lobsters H. gammarus were fed individually a marine animal meal (herring/mussels meal) for 56 days. Feeding a daily ration equivalent to 10% of their body weight gave better growth than feeding daily rations of 5% and 20%. Protein synthesis rates were similar for the three food rations but protein growth rates were significantly lower and protein degradation rates highest in the 5% body weight per day ration group. The efficiency with which synthesised protein was retained as growth was found to be 38% in the in the 10% ratio group. Protein synthesis rates of lobsters were found to be lower than those for shrimps (Penaeus vannamei). The amino acid flux also suggests a lower protein conversion efficiency than shrimps P. vannamei. The results suggests that lobsters are slow, periodic feeders and that growth can be readily increased by manipulation of particular environmental factors such as feeding frequency.

Ontogeny of Modulatory Inputs to Motor Networks: Early Established Projection and Progressive Neurotransmitter Acquisition

Modulatory information plays a key role in the expression and the ontogeny of motor networks. Many developmental studies suggest that the acquisition of adult properties by immature networks involves their progressive innervation by modulatory input neurons. Using the stomatogastric nervous system of the European lobster Homarus gammarus, we show that contrary to this assumption, the known population of projection neurons to motor networks, as revealed by retrograde dye migration, is established early in embryonic development. Moreover, these neurons display a large heterogeneity in the chronology of acquisition of their full adult neurotransmitter phenotype. We performed retrograde dye migration to compare the neuronal population projecting to motor networks located in the stomatogastric ganglion in the embryo and adult. We show that this neuronal population is quantitatively established at developmental stage 65%, and each identified projection neuron displays the same axon projection pattern in the adult and the embryo. We then combined retrograde dye migration with FLRFamide-like, histamine, and GABA immunocytochemistry to characterize the chronology of neurotransmitter expression in individual identified projection neurons. We show that this early established population of projection neurons gradually acquires its neurotransmitter phenotype complement. This study indicates that (1) the basic architecture of the known population of projection inputs to a target network is established early in development and (2) ontogenetic plasticity may depend on changes in neurotransmitter phenotype expression within preexisting neurons rather than in the addition of new projection neurons or fibers.