European Lobster Homarus Gammarus Research Articles

Maturity, fecundity and reproductive potential of the European lobster (Homarus gammarus) in Ireland

Fecundity and size at maturity of the European lobster Homarus gammarus (Crustacea: Decapoda) was estimated in four coastal regions of Ireland. Egg size increased with carapace length (CL) (egg size=0·9939×ln (CL)−3·0809). The size–fecundity relationship for all coasts combined was (fecundity=0·0044×CL3·1554). Physiological maturity was assessed using ovary colour, ovary factor, ova size, abdomen width/CL ratio, cement gland activity and moult status as criteria. Size at 50% maturity varied from 92·5 to 96 mm depending on region. The size–maturity relationship for all coasts combined was (Maturity= 1/(1+exp(14·595−0·15598×CL))). Over 60% of lobsters in the commercial landings were under the size at 50% maturity. Relative reproductive potential (RRP) of different size-classes was calculated from the size–fecundity and size–maturity models and the numbers by length in the landings. The modal RRP size-class was 98–100 mm. The commercial landings were dominated by the 86–92 mm size-classes.

Movement of wild European lobsters Homarus gammarus in natural habitat

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 222:177-186 (2001) - doi:10.3354/meps222177 Movement of wild European lobsters Homarus gammarus in natural habitat I. P. Smith*, A. C. Jensen, K. J. Collins, E. L. Mattey School of Ocean and Earth Science, University of Southampton, Southampton Oceanography Centre, European Way, Southampton SO14 3ZH, United Kingdom *E-mail: philip.smith@soc.soton.ac.uk ABSTRACT: Most previous mark-recapture studies of the movement of European lobsters have used externally attached tags which were lost at ecdysis, restricting the range of possible recapture intervals. Published studies of this species with tags designed to be retained through ecdysis have focussed on artificially reared lobsters, or wild lobsters released in artificial habitat. Here, we report a mark-recapture study of the mobility of wild European lobsters conducted in 3 areas on the south coast of England, using persistent tags. Tagged lobsters were smaller than the fishery minimum landing size (50 to 84 mm carapace length) and were therefore likely to be predominantly sexually immature. The majority of these lobsters do not appear to undertake extensive alongshore or on-/offshore migrations. Recapture distances ranged from 0 to 45 km, but 95% of recaptured lobsters moved <3.8 km from their original release positions over periods of up to 862 d. Distance moved did not differ between males and females, but there was a weak positive relationship between recapture distance and body size. The directional distribution of movements >0.5 km differed between the 3 study areas and appeared to be related to the spatial configuration of local lobster habitat, but with a marked tendency for offshore movement in 2 of the areas. Movements >5 km from all 3 release areas, which comprised 5% of recaptures after >6 mo, were generally undertaken by larger lobsters and were almost exclusively to the west or southwest, against the general direction of tide- and wind-generated residual water movement in the English Channel. KEY WORDS: Lobster · Mark-recapture · Movements · Migrations · Tagging Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 222. Online publication date: November 05, 2001 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2001 Inter-Research.

Effects of experience with shelter in hatchery-reared juvenile European lobsters Homarus gammarus

Hatchery-reared lobsters will be highly dependent on shelter after release, and the ability of training to enhance quick shelter-seeking behaviour was investigated. Single, emergent-phase lobsters were released in tanks, either with or without shelter present, to determine whether the lobsters reached the shelter position by chance or not. They were recovered after two days and re-released into either identical tanks or tanks without shelter. All lobsters were observed for at least 10 min after each release; walking direction from the release position and time elapsed before they entered the shelter were recorded. In additional treatments, some lobsters were exposed to a mock predator, in the form of a series of short touches, and times before they reached shelter were compared with those of lobsters not so touched. Hatchery-reared lobster juveniles adapted to new environments and shelters. Experienced juveniles were quicker to find shelter. Time to reach shelter decreased in touched lobsters. Search time increased in experienced lobsters after removal of shelter.

A long-term mesocosm study on the settlement and survival of juvenile European lobster Homarus gammarus L. in four natural substrata.

To date, the natural substratum preferences of early benthic phase (EBP) European lobsters (Homarus gammarus) remain largely unknown. This study utilised a large scale mesocosm experiment to determine if the animal favours cobble ground, similar to its American counterpart (Homarus americanus), or has other substratum preferences. Postlarvae were provided with the choice of settling on four natural substrata: sand, coralline algae, mussel shell and cobble. Over a nine month period, the number and size of juveniles on each substratum was recorded, with loss of chelipeds used as an indication of social interaction. After a 30 day period, a non-random distribution of lobsters was observed on the four substrata. Juveniles were more abundant in substrata which provided pre-existing shelter in the form of interstitial spaces, i.e. cobble and mussel shell, than in sand or coralline algae. The survival of individuals from postlarvae to 30 day old juveniles ranged from 5 to 14% with surviving benthic recruits showing a clear mode at 6-8 mm carapace length (CL) in size distribution. The density of lobsters per m(2) of cobble remained relatively constant (18/m(2)) throughout the study period while the density of juveniles on mussel shell decreased significantly (35 to 5/m(2)). The size distribution of lobsters on each substratum also varied with time. By the conclusion of the trial, lobsters found in mussel shell had a mode of 8-10 mm CL within a range of 6-14 mm CL while those in cobble had a mode of 10-12 mm CL within a range of 8-24 mm CL. Overall, the results underline the importance of shelter-providing habitat such as cobble or crevice-type substrata to EBP European lobsters. They also confirm that for a shelter-dwelling animal such as a lobster, the physical structure of the habitat is a key factor in determining both the size and number of its inhabitants.

On the occurrence of juvenile lobster Homarus gammarus in intertidal habitat

The early benthic phase (EBP) European lobster Homarus gammarus, and the habitat to which it recruits, remains largely undiscovered. Following reports that juvenile lobsters were being located within an intertidal lobster fishery in Johnshaven, Scotland, a three day census was undertaken. The shore consisted of a wave cut platform with a red sandstone/cobble conglomerate substratum. Three juvenile lobsters of 28, 32 and 45 mm carapace length (CL) were located in a crevice type habitat. It is hypothesized that in some areas of coastline, intertidal crevices act as a peripheral habitat for juvenile lobsters.

Na(+) and Ca(2+) pumps in the gills, epipodites and branchiostegites of the european lobster Homarus gammarus: effects of dilute sea water.

Crude homogenates and plasma-membrane-enriched fractions were prepared from the epithelium of the gills, epipodites and branchiostegites of intermoult European lobsters Homarus gammarus, and Na(+)/K(+)-ATPase, Ca(2+)-ATPase and Na(+)/Ca(2+) exchange activities were quantified in these tissues. Lobsters were kept in sea water (salinity 35 ) or were adapted to dilute sea water (22.1 ). The lobster hyperregulates haemolymph osmolarity and Ca(2+) levels in both media. Homogenates of the podobranchs, arthrobranchs and pleurobranchs had comparable Na(+)/K(+)-ATPase specific activities, and mean activities increased significantly for all three types of gills when the animals were kept in dilute sea water. In the epipodites and branchiostegites, Na(+)/K(+)-ATPase specific activities exceeded those in the gills, and exposure to dilute sea water greatly enhanced these activities. In sea water, 80 % of the total Na(+)/K(+)-ATPase activity is associated with the gills and epipodites (each tissue containing 40 %) and 20 % with the branchiostegites; in dilute sea water, the gills contained approximately 25 %, the epipodites 40 % and the branchiostegites approximately 35 % of the total activity, indicating the relative importance of the epipodites and branchiostegites for ionic hyperregulation in dilute media. In plasma membrane vesicles isolated from the gills, epipodites and branchiostegites, Ca(2+) transport driven by ATP and by a Na(+ )gradient was demonstrated. Exposure to dilute sea water enhanced Na(+)/Ca(2+ )exchange and Ca(2+)-ATPase activities in the epipodites and branchiostegites; in the gills, however, Ca(2+) transport activities decreased. The role of these tissues and enzymes in Na(+) and Ca(2+) handling by the lobster is discussed.

A comparison of claw morphology and dominance between wild and cultivated male European lobster.

Claw size and dominance in cultivated versus wild European lobsters Homarus gammarus were compared. Normally, lobsters develop a short, high and wide crusher and a slender scissor claw. In culture, both claws often develop into scissor claws. With growth, cultivated males developed one significantly elongated scissor claw (major claw), and one normal scissor claw, compared to wild males (minor claw). The differences increased with size. The wild males had higher claw index than cultured ones, due to the crusher claw. Wild lobsters with higher claw index were dominant. Cultivated males with claw indices at least 200 mm2 higher than the opponent, won. Only scissor claws were broken in the encounters. Even if cultivated lobsters in time develop claws equal to wild lobsters, they might still be less robust. In the light of these findings, we suggest that lobsters cultivated for restocking purposes should be given access to an appropriate substrate allowing them to develop one claw into a crusher during the early benthic stage.

Motor Pattern Specification by Dual Descending Pathways to a Lobster Rhythm-Generating Network

In the European lobster Homarus gammarus, rhythmic masticatory movements of the three foregut gastric mill teeth are generated by antagonistic sets of striated muscles that are driven by a neural network in the stomatogastric ganglion. In vitro, this circuit can spontaneously generate a single (type I) motor program, unlike in vivo in which gastric mill patterns with different phase relationships are found. By using paired intrasomatic recordings, all elements of the gastric mill network, which consists mainly of motoneurons, have been identified and their synaptic relationships established. The gastric mill circuit of Homarus is similar to that of other decapod crustaceans, although some differences in neuron number and synaptic connectivity were found. Moreover, specific members of the lobster network receive input from two identified interneurons, one excitatory and one inhibitory, that project from each rostral commissural ganglion. Integration of input from these projection elements is mediated by synaptic interactions within the gastric mill network itself. In arrhythmic preparations, direct phasic stimulation of the previously identified commissural gastric (CG) interneuron evokes gastric mill output similar to the type I pattern spontaneously expressed in vitro and in vivo. The newly identified gastric inhibitor interneuron makes inhibitory synapses onto a different subset of gastric mill neurons and, when activated with the CG neuron, drives gastric mill output similar to the type II pattern that is only observed in the intact animal. Thus, two distinct phenotypes of gastric mill network activity can be specified by the concerted actions of parallel input pathways and synaptic connectivity within a target central pattern generator.

Immunolocalization of Na+,K(+)-ATPase in the organs of the branchial cavity of the European lobster Homarus gammarus (Crustacea, Decapoda).

The localization of Na+,K(+)-ATPase in epithelia of the organs of the branchial cavity of Homarus gammarus exposed to seawater and dilute seawater was examined by immunofluorescence microscopy and immunogold electron microscopy with a monoclonal antibody IgG alpha 5 raised against the avian alpha-subunit of the Na-,K(+)-ATPase. In juveniles held in seawater, fluorescent staining was observed only in the epithelial cells of epipodites. In juveniles held in dilute seawater, heavier immunoreactivity was observed in the epithelial cells of epipodites, and positive immunostaining was also observed along the inner-side epithelial layer of the branchiostegites. No fluorescent staining was observed in the gill epithelia. At the ultrastructural level, the Na+,K(+)-ATPase was localized in the basolateral infolding systems of the epipodite and inner-side branchiostegite epithelia of juveniles held in dilute seawater, mostly along the basal lamina. The expression of Na+,K(+)-ATPase therefore differs within tissues of the branchial cavity and according to the external salinity. These and previous ultrastructural observations suggest that the epipodites, and to a lesser extent the inner-side epithelium of the branchiostegites, are involved in the slight hyper-regulation displayed by lobsters at low salinity. Enhanced Na+,K(+)-ATPase activity and de novo synthesis of Na+,K(+)-ATPase within the epipodite and branchiostegite epithelia may be key points enabling lobsters to adapt to low salinity environments.

Seasonal changes in the level and diel pattern of activity in the European lobster Homarus gammarus

European lobsters are large, mobile crustaceans of ecological and commercial significance. Until recently, the lack of a reliable technique for long-term, in situ monitoring of activity has hindered study of seasonal variation in activity and its determinants. Electromagnetic telemetry has been used to measure seasonal changes in locomotor activity and body movements of lobsters on an artificial reef in Poole Bay, southern England. Both measures of activity showed marked seasonal variation, related primarily to water temperature, with greatest activity in late summer and minimum values in winter. Subsidiary effects of water movement and seabed illumination were also indicated. Throughout the spring and summer, excursions outside shelter were almost exclusively nocturnal, with movement peaking in the early part of the night. Body movements followed a similar pattern, but with less abrupt changes, suggesting a degree of activity within shelters during the day. Diet timing of lobster activity appeared to be mainly governed exogenously by light level, since the length of the nocturnal active period and the timing of the activity peak varied seasonally with the times of sunset and sunrise, and there was a relative increase in diurnal activity during periods of low seabed light levels caused by increased turbidity. During low temperatures in lid to late winter, activity was low throughout the 24 h cycle. These findings suggest that there are likely to be significant seasonal changes in the relationship between fishing effort and fishing mortality that need to be taken into account in lobster stock assessment.

Preliminary acoustic tracking of native and transplanted European lobsters (Homarus gammarus) in an open sea lagoon

In a larger release project, European lobsters (Homarus gammarus) under legal size have been captured, checked for magnetic microtags, externally tagged, and released to their home site for population and migration studies. To see if transplanted lobsters behave differently from native lobsters, four acoustically tagged males were released between three stationary hydrophones in an open sea lagoon and tracked continuously for 2–3 weeks. Lobster 1 was from the lagoon, Lobster 2 was transplanted less than 1000 m from its capture location, and Lobsters 3 and 4 were transplanted more than 5000 m. Within a few hours, Lobsters 1 and 2 took up residence in the area of their original home sites. Lobsters 3 and 4 took up residence in the lagoon after extended roaming. Six days after release, Lobsters 1 and 4 engaged in nocturnal activity, Lobster 2 changed locations occasionally without moving long distances, and Lobster 3 did not move. The odd movement patterns in the transplanted lobsters could be caused by their lack of local knowledge. Since rocks caused blocking of the acoustic signals, manual monitoring was needed to confirm the lobster positions. In cryptic animals such as lobsters, a continuous tracking system that can penetrate stones is required.

Within‐burrow behaviour of juvenile European lobstershomarus gammarus(L.)

The behaviour of juvenile European lobsters (Homarus gammarus (L.)) in artificial burrows was observed in the laboratory to determine features of within‐burrow behaviour likely to be important in their survival and well‐being during the early benthic phase of life. Burrow construction methods and within‐burrow behaviour of individually held, hatchery reared, juvenile lobsters (12 to 20 mm CL) in mid‐intermoult were observed in clear plastic aquaria half filled with cohesive mud taken from Newcastle Bay. Eleven separate behaviour categories were identified although it was found that most activities did not occur on their own or, necessarily, in one particular location. Behaviour categories included pleopod fanning, cleaning, food burying and retrieval, feeding, substrate probing and picking, sieving and moving substrate and resting. Factors affecting burrow occupancy and the durations of selected activities inside the burrow were burrow chamber size, number of entrances, water flow, moulting and hunger. Hu...

Nature and metabolism of carotenoid pigments during the embryogenesis of the European lobster Homarus gammarus (Linné, 1758)

Abstract The carotenoid concentration of the whole developing egg of the lobster Homarus gammarus remains unchanged during the embryogenesis. The decrease of pigment amounts in the vitellin mass corresponds to the transfer of carotenoids to the forming embryo. Esterified astaxanthin (mono and diester forms) appear during the early metanauplius stage EI 90. Unesterified astaxanthin is the main pigment occurring in the vitellus. Esterified forms were found to increase whereas free astaxanthin decreases up to hatch. The esterification of astaxanthin permits the storage of pigment in the tissues as an adaptative feature related to the formation of the embryo.

Ageing the European lobster Homarus gammarus by the lipofuscin in its eyestalk ganglia

Ageing the European lobster Homarus gammarus by the lipofuscin in its eyestalk ganglia

Evolution of carotenoid metabolic capabilities during the early development of the European lobster Homarus gammarus (Linné, 1758)

The quantification of carotenoids during the early developmental stages of the European lobster Homarus gammarus, indicates a rapid decrease of pigment concentration, occurring immediately after hatching. Conversely, the carotenoid amount of the individual increases progressively at the end of larval stage I, as a result of an enhanced feeding activity. Free astaxanthin represents the bulk of carotenoids of the unhatched embryo ( metanauplius), whereas larval, post-larval and juvenile stages exhibit the typical adult carotenoid pattern, in which astaxanthin esterified forms (diester and monoester) appear preponderant. The Artemia strain used as food material is not found to contain astaxanthin, while important amounts of canthaxanthin are observed; nevertheless, this carotenoid is not detected in the larvae, indicating that metabolic transformation capabilities are already occurring in freshly hatched individuals.

CARBOHYDRATE DIGESTION IN THE EUROPEAN LOBSTER HOMARUS GAMMARUS (L.)

ABSTRACT The ability of lobsters to utilize dietary carbohydrates is dependant upon the nature and amount of carbohydrases present in these crustaceans. Since this is a potential species for culture, a knowledge of its ability to digest carbohydrates could usefully be applied in the formulation of inert diets. The aim of this study was to identify the activities present in the gut and to assess the digestibility of physically modified starches using midgut-gland extracts. A range of carbohydrase activities including a-amylase (EC 3.2.1.1), maltase (EC 3.2.1.20), α-glucosidase (EC 3.2.1.20), β-glucanase (EC 3.2.1.39), β-glucosidase (EC 3.2.1.21), α- and β-galactosidases (EC 3.2.1.22 and EC 3.2.1.23) were detected in the midgut gland and in the gastric juice of the European lobster Homarus gammarus. Optimal activity for the above enzyme activities was in the pH range of 4.5-5.5 and highest levels were generally located in the gastric contents. α-Glucans were more readily digested than β-glucans; hydrolysis of pentosans was minimal and chitin was poorly hydrolyzed. Polysaccharides and disaccharides were well digested by gastric extracts, whereas the predominant digestive capacity of the midgut gland was toward disaccharides. Molecular weights of the midgut gland a-amylase and maltase activities were estimated by gel-filtration to be approximately 21 kDaltons and 63 kDaltons, respectively. Physical modification of starch granules enhanced their susceptibility to digestion by midgut-gland extracts and therefore pretreatment of dietary starches may be considered in order to increase their nutritional value in inert aquaculture diets.

Suspension feeding in adult Nephrops norvegicus (L.) and Homarus gammarus (L.) (decapoda)

Suspension feeding in adults of the Norway lobster Nephrops norvegicus (40–74 g) and the European lobster Homarus gammarus (280–350 g) was tested in experiments offering planktonic food items of different sizes from 200 to 600 μm and measuring the clearing capacity. Both lobster species were found to effectively clear water of food particles comprising nauplii of the brine shrimp Artemia salina of about 600 μm in size. These were reduced to 50% of the initial concentration within 5 h and to 90% within 12 h. When N. norvegicus was offered food particles averaging 200 μm, a significant reduction in average size occurred, indicating that the minimum retention size is around 200 μm. Fluorescently dyed Artemia salina were recovered in the stomach and intestine of lobsters proving that the filtered particles are passed to the digestive tract. Results from other experiments, using the blood pigment (haemocyanin) concentration as an index of nutritional state, indicated that the lobsters can get some nutritional advantage from suspension feeding. Suspension feeding in larger decapods has not been described previously, so the significance of this finding is discussed with respect to changes in behavioural and ecological role.

Temperature-specific rates of embryonic development of the European lobster Homarus gammarus (L.)

Berried Homarus gammarus (L.) females were reared at three constant temperatures (10, 15 and 20°C), and the rates of development of their embryos monitored by measuring embryonic eye index according to Perkins. An equation relating the increase in eye index to temperature was established, yielding the estimated time to hatch at different temperatures. It may be used to approximate the rate of hatch according to rearing temperature in H. gammarus.

Age Determination of the Spider Crab Maja squinado and the European Lobster Homarus gammarus by 228Th/228Ra Chronology: Possible Extension to Other Crustaceans

A method of age determination was developed on carapaces of the spider crab, Maja squinado Herbst and European lobster Homarus gammarus L., by measuring the natural radionuclides activity ratio, 228Th/228Ra in the exoskeleton. This method allows the determination of the time elapsed since the preceding molt of the animal. It was successfully tested on five spider crabs and four lobsters which had molted in captivity and therefore had a carapace of known age. It is probable that the method could, with some reservations, be extended to all marine Decapod Crustacea bearing a well calcified exoskeleton.

Histo-autoradiographic localisation of americium (241Am) in tissues of European lobster Homarus gammarus and edible crab Cancer pagurus after uptake from labelled sea water

Histo-autoradiographic localisation of americium (241Am) in tissues of European lobster Homarus gammarus and edible crab Cancer pagurus after uptake from labelled sea water