Benthic invertebrate larval response to substrate characteristics at settlement: Shelter preferences of the American lobsterHomarus americanus

In Barkley Sound, British Columbia, Canada, newly hatched Nucella emarginata, a direct developing prosobranch gastropod, are almost exclusively located within 3 structurally complex microhabitats: the filamentous algae Cladophora columbiana, clusters of mussels Mytilus spp., and dense assemblages of the barnacle Semibalanus cariosus. When exposed to desiccation or predators for 4 to 5 h, mortality of hatchlings located in these microhabitats (1.7 to 36% mortality) was considerably lower than for individuals on open surfaces (99 to 100%). Also, food (prey species) in C. columbiana, mussel clusters, and S. cariosus microhab~tats was more abundant but of similar energetic value to that on open rock surfaces. The microhabitats used by early juvenile N. emarginata thus provide the double advantage of a considerably reduced risk of mortality and abundant prey. The means by which hatchlings disperse after emerging from their egg capsules were established by laboratory observations and by deployment of collectors in the field. Hatchlings do not actively initiate dispersal by drifting in the water column. Crawling is the usual means of travelling from the capsule to protective microhabitats, with hatchling crawling speed averaging only 3.7 mm min-' on smooth rock surfaces in the laboratory. The abundance and distribution of microhabitats that protect early juveniles could therefore be important determinants of the local abundance and distribution of N. emarginata populations. The use of protective microhabitats may be the key to survival through the vulnerable early juvenile period in many benthic marine organisms.

Section: Distribution In the Fieldmentioning

confidence: 97%

Distribution and dispersal of early juvenile snails:effectiveness of intertidal microhabitats as refuges and food sources

Gosselin¹,

Chia²

1995

“…Larval supply could explain local differences in settlement (Katz et al 1994, Wahle & Incze 1997. The well-known shelterseeking behavior of lobsters during settlement can dramatically improve survival during the early benthic phase (Boudreau et al 1990, Incze & Wahle 1991, Wahle & Steneck 1991, Wahle 1992, Barshaw et al 1994, Cobb & Wahle 1994 Cancer irroratus (Beninger et al 1986, Clancy & Cobb 1991, Clancy 1995. Geographical patterns in settlement (i.e.…”

Section: Several Ecological Studies On Homarus Americanusmentioning

confidence: 99%

Different early post-settlement strategies between American lobsters Homarus americanus and rock crabs Cancer irroratus in the Gulf of Maine

Palma¹,

Wahle²,

Steneck³

1998

The abundance of many invertebrates with planktonic larval stages can be determined shortly after they reach the benthos. In this study, we quantified patterns of abundance and habitat utilization of early benthic phases of the American lobster Homarr~s americanus and the rock crab Cancer irroratus. These 2 decapods are among the most common and abundant macroinvertebrates in coastal zones of the Gulf of Maine, with similar densities of larger individuals. Settlement and early postsettlement survival indicate that lobsters are highly substrate-specific early in life, settling predominantly in cobble beds. Crabs appear to be less selective, settling both in cobble and sand. Cumulative settlement of crabs, inferred from weekly censuses over the summer, was an order of magnitude greater than that of lobsters over the same time period. However, only crabs showed significant postsettlement losses. Although the identity of specific predators is unknown, predator exclusion experiments and placement of vacant uninhabited nursery habitat suggested that post-settlement mortality rather than emigration was respons~ble for these losses. The selectlve habitat-seeking behavior and lower post-settlement mortality of lobsters is consistent with their lower fecundity and later onset of reproductive maturity. The patterns observed for crabs, however, suggest a different strategy which is more in accordance with their hlgher fecundity and earlier onset of maturity. It is possible that lower fecundity but greater per-egg investment, along with strict habitat selection at settlement and lower post-settlement mortality, allows adult lobster populations to equal adult populations of crabs. This occurs despite crabs being more fecund and less habitat-selective settlers but sustaining higher postsettlement mortality.KEY WORDS: Settlement -Early post-settlement . Predation . Mortality -S u~v o r s h i p . Substrate type .

“…Previous observations have shown that shelters of this size cannot accommodate more than 1 postlarva at one time. Since the light level within shelters is an important cue in microhabitat selection for settling lobsters (Boudreau et al 1990), this factor was manipulated to create a gradient in shelter quality. Four types of microhabitat, corresponding to shelters offering different light intensities (measured with a Biospherical quantum meter), were obtained ( Fig.…”

Section: Methodsmentioning

confidence: 99%

“…used = 480). The number of swimming, sheltered (> 3/1 body length in shelter), and benthic unsheltered postlarvae was then recorded once every 4 h during 2 d. Night counts were carried out using a red light (see Boudreau et al 1990). To avoid disturbances during the experiment, the number of sheltered postlarvae was obtained by subtracting swimming and benthic unsheltered postlarvae from the total number of individuals initially introduced to the aquarium.…”

Section: Methodsmentioning

confidence: 99%

“…Lobsters settle preferentially and more quickly on hard heterogeneous bottoms than on soft, fea:ure!ess substrata (Botero & Atema 1982). We suggested that light intensity within shelters could be the primary cue involved in microhabitat selection by settling lobsters (Boudreau et al 1990), postlarvae strongly preferring opaque to transparent shelters. In the present study, this factor was manipulated to create 4 microhabitats of different quality (level of illumination).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Effect of age, injury, and predator odors or settlement and shelter selection by lobster Homarus amencanus postlarvae

Boudreau¹,

Bourget²,

Simard³

1993

The effects of endogenous and exogenous factors on settlement and habitat selection behaviours of Homarus americanus postlarvae were studied under controlled conditions in the laboratory. Light level within shelters, a primary cue used in microhabitat selection by settling lobsters, was manipulated to create 4 microhabitats of different quality (= level of illumination). Preliminary experiments indicated that, when offered separately, low light intensity shelters induced more postlarvae to settle and seek a shelter than microhabitats presenting higher light levels. Choice experiments (all types of shelter offered simultaneously) were designed to test whether (1) delayed settlement, (2) injuries at metamorphosis (loss of one or both chelipeds), and (3) metabolites of the fish predator Tautogolabrus adspersus, Influenced settlement rate and selectivity of competent lobsters. Postlarvae settled more quickly and sheltered less selectively as they aged. Similarly, postlarvae released in seawater previously conditioned by T adspersus tended to exhibit a higher settlement rate and lower degree of selectivity than when tested In control (unconditioned) water. Lobsters which had lost both chelipeds at metamorphosis exhibited a reduced settlement rate compared to normal postlarvae or postlarvae with a single chela. Severely injured postlarvae also appeared less selective than normal or slightly injured postlarvae. Implications of these results for further habitat choice expenments are discussed.