Planktonic Growth of Larval Lobster (Homarus americanus) off îles de la Madeleine (Quebec), Gulf of St. Lawrence

1988 ◽  
Vol 45 (5) ◽  
pp. 868-878 ◽  
Author(s):  
Christiane Hudon ◽  
Pierre Fradette
Keyword(s):  
Growth Rates ◽  
Atlantic Coast ◽  
Larval Growth ◽  
Homarus Americanus ◽  
Stage I ◽  
Female Size ◽  
Larval Size ◽  
Size Frequency Distribution ◽  
Geographical Variations ◽  
La Madeleine

The carapace length of the three planktonic larval and one postlarval stages of Homarus americanus was measured for larvae collected off îles de la Madeleine over three summers. Mean larval size did not vary between years or locations around the islands. The size of stages I and II remained constant throughout the summer, but after molting into stages III and IV, larvae diminished in size through the summer. Size frequency distribution became more scattered as larvae grew into more advanced stages. The increase of variance with size between stages I–IV followed the same progression as that observed between stages V–XIII, allowing prediction of the variance associated with mean size at each stage. The size of stage I larvae collected in nine regions along the Atlantic coast was not correlated with the July surface water temperature or with the smallest female size at maturity. Comparison of various body proportions suggested that a single morphometric measurement is not sufficient to describe geographical variations in size. Percentage growth per molt decreased with each successive molt. During summer, increment at molt decreased and molt frequency increased. Larval growth rates followed closely the temperature regime, with maximum growth rate attained during the warmest period of the summer (July 30 – August 9). The duration of the first three larval stages estimated from field data was of 24 d compared with 21 d calculated from previous laboratory studies. The maximum abundance of stage I larvae was synchronized with the period of most rapid increase in summer temperature, thus insuring that larvae achieved highest net growth rates through their planktonic phase.

Embryonic Development and Energetic Investment in Egg Production in Relation to Size of Female Lobster (Homarus americanus)

1987 ◽  
Vol 44 (6) ◽  
pp. 1157-1164 ◽  
Author(s):  
Jean Attard ◽  
Christiane Hudon
Keyword(s):  
Embryonic Development ◽  
Egg Production ◽  
Energy Content ◽  
Larval Growth ◽  
Somatic Growth ◽  
Dry Weight ◽  
Homarus Americanus ◽  
Female Size ◽  
Growth And Survival ◽  
The Difference

The egg development index, dry weight, and energy content were measured on eggs from 148 ovigerous female lobsters (Homarus americanus) caught off îles de la Madeleine (Québec). Two modes of embryonic development were observed at stages 3 and 8 (Perkins. 1972. Fish. Bull. 70: 95–99). Stage 3 predominated among females of 71–82 mm and stage 8 among those of 83–110 mm carapace length (CL), indicating that larger females both extrude and hatch their eggs earlier than smaller females. Energy content per egg increased with female size and ranged from 4.6 cal∙egg−1 for females 72–76 mm CL to 5.2 cal∙egg−1 for females 107–110 mm CL. Females between 82 and 90 mm CL invested 0.155 kcal per gram of their own weight in egg production, which was the maximum value in the size range. Females smaller than 82 mm CL and larger than 90 mm CL expended proportionately less on egg production, with the difference allocated to either somatic growth in the smaller or maintenance in the larger animals. Large females produce proportionately more eggs, containing more calories per egg which hatch at an earlier time than small females. The higher energy content of eggs from large females and their earlier hatching are probably factors that enhance larval growth and survival. If so, large females contribute relatively more to recruitment than their greater fecundity.

Effects of Reproduction upon Molting and Growth in Female American Lobsters (Homarus americanus)

1988 ◽  
Vol 45 (5) ◽  
pp. 805-821 ◽  
Author(s):  
K. Nelson ◽  
D. Hedgecock ◽  
W. Borgeson
Keyword(s):  
Growth Rates ◽  
Homarus Americanus ◽  
Control Group ◽  
American Lobster ◽  
Cycle Duration ◽  
Female Size ◽  
Molt Cycle ◽  
Young Females ◽  
Long Day ◽  
Short Days

American lobster (Homarus americanus) females characteristically extrude eggs (E) in the summer of the year following a summer or autumn molt (M), but young females may extrude in the same year. The subsequent M is delayed until after hatching, resulting in the former case in a 2-yr reproductive molt cycle, measuring from M to M. Adult female lobsters were exposed to periods of short days (8 h light: 16 h dark) followed by long day onset (L) (16 h light: 8 h dark) at different times with respect to M, or as controls were kept under continuous long-day conditions. In this way were generated molt cycles with delayed or undelayed extrusions, as well as ones with incomplete vitellogeneses resulting from too-long delayed L, and molt cycles in which vitrellogenesis did not begin (control group). Delayed L results in delayed E and M, as measured either in days or in day-degrees above 6 °C. An incompleted vitellogenesis following a too-long delayed L changes neither the duration of the molt cycle nor its characteristic positive correlation with female size; the duration of molt cycles containing either delayed or undelayed E appears in contrast to become independent of size. Intermolt intervals following prior E are shorter than those following anovulatory cycles. Retention of the clutch to hatching is associated with an additional increment to the intermolt interval. The results suggest that following E, a "reproductive" program replaces the "somatic" program of control of molt cycle duration. Incompleted vitellogeneses are associated with significantly smaller molt increments and growth rates than in the evidently avitellogenic continuous long-day control group, even though intermolt duration and its relation to size remain the same. Growth rates of molt cycles containing incompleted vitellogeneses are significantly higher than ones containing E only if that is delayed. Differential dependence of molt cycle duration and growth rate measures upon size and temperature indicate that molting and growth are distinct and rather independently controlled processes in adult lobsters, however tightly linked they may be in juveniles. Implications for molting and reproduction in the natural environment are discussed.

La répartition horizontale et verticale des larves de homard (Homarus americanus) autour des îles de la Madeleine, golfe du Saint-Laurent

1986 ◽  
Vol 43 (11) ◽  
pp. 2164-2176 ◽  
Author(s):  
Christiane Hudon ◽  
Pierre Fradette ◽  
Pierre Legendre
Keyword(s):  
Vertical Distribution ◽  
General Pattern ◽  
Stage Iv ◽  
Homarus Americanus ◽  
Stage I ◽  
Larval Abundance ◽  
Larval Stages ◽  
Vertical Distributions ◽  
Horizontal And Vertical Distributions ◽  
La Madeleine

Thirty-nine stations localized around the eastern tip of the Îles de la Madeleine, in two lagoons, and in the baie de Plaisance were sampled using plankton net tows during the summers of 1978, 1980, and 1981. The horizontal and vertical distributions of each of the four larval stages of Homarus americanus were assessed from sets of surface tows using simple neuston and meter nets (1978 and 1980) as well as a three-compartment plankton net (1981). Most of the stage I larval production takes place in the northeast and southeast regions. However, the abundance of stage IV larvae is low in the southeast and almost nil in the northeast. By contrast, the baie de Plaisance harbors very few stage I larvae, but a very high proportion of stage III and IV larvae. The periods of first appearance and maximum abundance are also out of phase for the three regions, occurring in the northeast before the southeast and the baie de Plaisance. These results suggest that the general pattern of abundance of larvae is driven by the current regime, flushing the larvae around the Pointe de l'Est and concentrating them in the baie de Plaisance following a gyre. On a smaller scale, 12 stations arranged in a 3 × 4 grid in the baie de Plaisance were sampled for 12 wk in the summer of 1980. The first three larval stages show a strongly aggregated distribution and are most frequent at the mouth of the bay. Conversely, stage IV larvae are found more frequently in the shore stations and inside the bay. There is a significant correlation between stage IV larval abundance and the distance to rocky bottoms favorable to benthic life. The vertical distribution of larvae at two stations (1981) shows that only the stage I larvae have a vertical distribution related to light intensity, being found in highest abundance in the surface layer (0–0.8 m) at dusk and dawn. Stage I larvae were uniformly distributed between 0 and 1.6 m during the day and down to 2.4 m at night. Stage II, III, and IV larvae were always found near the surface.

The influence of larval size, temperature, and components of the functional response to prey density on growth rates of the dragonflies Lestes disjunctus and Coenagrion resolutum (Insecta: Odonata)

1995 ◽  
Vol 73 (9) ◽  
pp. 1672-1680 ◽  
Author(s):  
Rangathilakam Krishnaraj ◽  
Gordon Pritchard
Keyword(s):  
Growth Rate ◽  
Regression Analysis ◽  
Multiple Regression Analysis ◽  
Functional Response ◽  
Growth Rates ◽  
Prey Density ◽  
Larval Growth ◽  
Handling Time ◽  
Sampling Errors ◽  
Larval Size

Larval growth of Lestes disjunctus was completed in 70 d in the field, whereas in Coenagrion resolutum it took 10–22 months. This was not simply the result of occupying warmer microhabitats, because L. disjunctus larvae grew faster than C. resolutum at all constant temperatures between 10 and 25 °C in the laboratory. Multiple regression analysis showed that growth rates of both species were positively related to temperature and negatively related to larval size and to the square of temperature. The latter term is necessary to describe the decrease in growth rate at high temperatures. The equation predicted that the growth rate of L. disjunctus reached a maximum at 28.8 °C, whereas that of C. resolutum decreased above 22.4 °C. Small and medium-sized larvae of L. disjunctus ate more prey (Daphnia magna) in 15 min than C. resolutum at all prey densities. In 15-min experiments the attack coefficient for small L. disjunctus larvae was significantly larger than for small C. resolutum larvae and handling time for medium larvae was shorter. Other comparisons had large associated sampling errors, but the trends were the same. These differences may be associated with the relatively longer labia of L. disjunctus and its ability to change hunting methods from ambush to active search.

The missing links: larval and post-larval development of the ascoglossan opisthobranch Elysia viridis

2000 ◽  
Vol 80 (6) ◽  
pp. 1087-1094 ◽  
Author(s):  
Cynthia D. Trowbridge
Keyword(s):  
Larval Development ◽  
Growth Rates ◽  
Shell Length ◽  
Larval Growth ◽  
Model Organism ◽  
Larval Life ◽  
Codium Fragile ◽  
Planktotrophic Larvae ◽  
Algal Diet ◽  
Better Than

The stenophagous ascoglossan (=sacoglossan) opisthobranch Elysia viridis has long been a model organism for the study of endosymbiosis or kleptoplasty as well as one of the few herbivores to consume the introduced green macroalga Codium fragile on European shores. Larval and post-larval dynamics of the ascoglossan were investigated. Planktotrophic larvae of E. viridis grew at 5–10 μm d−1 (shell length) at 15°C on a unicellular algal diet (the cryptophyte Rhodomonas baltica); larvae became competent one month post-hatching. Effective feeding and chloroplast acquisition typically started within 2–3 d of metamorphosis. Slugs grew about 8 mm in the first month of post-larval life. During this period, juveniles held in the light did not grow faster or survive better than conspecifics held in the dark; thus, functional kleptoplasty did not occur during first three weeks of benthic life. While larval growth rates and the nature of metamorphic cues are consistent with those of many other opisthobranch species with planktotrophic larvae, measures of post-larval growth—particularly as it pertains to kleptoplasty—is a new contribution to opisthobranch biology.

scholarly journals Variation in growth and instar number in field and laboratory Manduca sexta

2007 ◽  
Vol 274 (1612) ◽  
pp. 977-981 ◽  
Author(s):  
Joel G Kingsolver
Keyword(s):  
North Carolina ◽  
Body Size ◽  
Manduca Sexta ◽  
Growth Rates ◽  
Developmental Plasticity ◽  
Larval Growth ◽  
Physiological Control ◽  
Larval Instars ◽  
Laboratory Colony ◽  
Early Larval Development

The tobacco hornworm Manduca sexta has been an important model system for understanding physiological control of growth, development and metamorphosis of insects for more than half a century. Like all Manduca , M. sexta typically has five larval instars, with developmental commitment to metamorphosis occurring early in the 5th (final) instar. Here we show that M. sexta from a field population in North Carolina (USA) shows substantial intraspecific variation in the number of larval instars when feeding on a modified artificial diet. Individuals with six instars consistently exhibited slower growth rates during early larval development than individuals with five instars. The frequency of individuals with six instars decreased with increased rearing temperature. In contrast, M. sexta from a laboratory colony consistently had five instars, and had more rapid larval growth rates than M. sexta from the field. We identify a threshold body size at the start of the 5th instar that predicts whether an individual will have five (greater than 600 mg) or six instars (less than 600 mg). Variation in field populations in Manduca provides an important resource for understanding physiological control, developmental plasticity and evolution of growth rate, body size and instar number.

Ecology and Growth of Postlarval and Juvenile Lobster, Homarus americanus, off Îles de la Madeleine (Quebec)

1987 ◽  
Vol 44 (11) ◽  
pp. 1855-1869 ◽  
Author(s):  
Christiane Hudon
Keyword(s):  
Growth Factor ◽  
Size Structure ◽  
Stage Iv ◽  
High Growth ◽  
Homarus Americanus ◽  
Fine Tuning ◽  
Mean Size ◽  
Density And Biomass ◽  
Rocky Bottoms ◽  
La Madeleine

Lobsters, Homarus americanus were studied in various habitats off Îles de la Madeleine, Quebec, from June to October 1985. Density, biomass, and size structure were estimated quantitatively using underwater corrals (40 m2) on rocky bottoms or transects (200 m2) on sandy bottoms and eelgrass beds. On the basis of behavioural observations during capture, lobsters were divided into postlarvae (<25 mm carapace length, CL), juveniles (25–76 mm CL), and adults (>76 mm CL). Density, biomass, and size structure were closely related to the coarseness of the bottom. Density and biomass were greater and mean size was larger on algae-covered boulders than on bare stones. Postlarval and juvenile lobsters were most numerous on shallow rocky bottoms where high densities (0.8–3.8 ind∙m−2) of small lobsters (mean size from 23.8 to 35.5 mm CL) were captured. Low density of juveniles and adults occurred on sand covered with eelgrass. No resident lobsters were found on bare sand. Temporal variation of postlarval density was synchronous at the three stations investigated. Postlarval density decreased during the summer until the settlement of planktonic postlarvae in mid-August. Moulting activity occurred throughout the summer, with a peak in early July. Mean size values for stages V–XIV were fitted to the cumulated size distribution and were used to calculate the percent increment for each moult stage (growth factor) and the expected duration of each stage. The 2-mo duration of the stage IV settlement period could result in a size range of 6–21 mm CL (mean size 14.5 mm CL, stage VIII) for a cohort by the end of its first season of benthic growth. The transition from planktonic to benthic life was characterized by a decrease of the growth factor at stage V, which was subsequently compensated at stages VI and VII by high growth factor values. In the first three growth seasons, spring and summer moults exhibit higher growth factor values than fall moults. These seasonal variations result in regular oscillations of the growth factor dampening progressively between stages V and XIV, instead of the smooth decline hypothesized in previous studies. A combination of factors, such as cryptic behaviour, high substrate selectivity, gradual settlement over the late summer months, and variability in growth factor, reflect the very fine tuning of the lobster's early benthic life stages to the constraints of its physical environment.

Changes in female lobster (Homarus americanus) size at maturity and implications for the lobster resource in Long Island Sound, Connecticut

2001 ◽  
Vol 52 (8) ◽  
pp. 1283 ◽  
Author(s):  
Donald F. Landers Jr ◽  
Milan Keser ◽  
Saul B. Saila
Keyword(s):  
Sexual Maturity ◽  
Egg Production ◽  
Long Island ◽  
Homarus Americanus ◽  
Long Island Sound ◽  
Female Size ◽  
Size At Maturity ◽  
Size At Sexual Maturity ◽  
Average Size ◽  
Island Sound

Population theory predicts that, under conditions of high age/size-specific mortality rates, individuals in highly exploited populations increase their fitness by decreasing size at sexual maturity, relative to less exploited populations. The benefit of early reproductive maturation is that individuals have a higher probability of surviving to maturity and contributing progeny to maintain the population. Empirical evidence, based on morphometric data from nearly 60 000 female lobsters collected since 1981, suggests that size at sexual maturity of female lobsters in Long Island Sound (USA) has recently decreased. Our findings were supported by decreases in average size and increases in abundance of egg-bearing females over the past two decades. Changes in female size at maturity and subsequent higher egg production may also help to explain the recent increase in lobster recruitment and landings. It is unclear whether these changes were caused by density-dependent factors related to the high exploitation of the species, by natural environmental factors (e.g. higher seawater temperatures), or a combination of the two.

Incidence of Gaffkya homari in Natural Lobster (Homarus americanus) Populations of the Atlantic Region of Canada

1966 ◽  
Vol 23 (9) ◽  
pp. 1325-1330 ◽  
Author(s):  
James E. Stewart ◽  
John W. Cornick ◽  
Doris I. Spears ◽  
D. W. McLeese
Keyword(s):  
Atlantic Coast ◽  
Homarus Americanus ◽  
Atlantic Region ◽  
Infection Source ◽  
Natural Incidence

Hemolymph samples drawn from 2035 lobsters captured in five areas off the Canadian Atlantic coast were individually tested for the bacterium Gaffkya homari, using a qualitative, presumptive test, followed by a confirmatory procedure. Ninety-six lobsters, or almost 5% of the total, were confirmed as being infected. The approximate range of G. homari incidence was from 2 to 40% indicating that G. homari is resident in the natural lobster population of this region. Evidence suggested that a high natural incidence can lead to an epizootic among stored, captive lobsters. The possibility that an infection source exists in addition to the G. homari strains resident in the lobster population is discussed.

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