Brief description
Interactions between native and introduced species can help to elucidate the impact of exotic species on the broader community. This work examines utilisation of an introduced gastropod, the New Zealand screwshell (Maoricolpus roseus) by native hermit crabs in eastern Tasmania.Lineage
Maintenance and Update Frequency: notPlanned
Statement: Pagurixus handrecki and Micropagus acantholepis were collected from:
Pirates Bay 43°0353 S 147°9425 E
(at 6m depth)
The larger species, P. tuberculatus, was collected from:
Dennes Point 43°03.618 S 147°19.703 E
(at 10-15m depth)
Statement: Shell preference trials
Trials were conducted in 165x110x55 mm plastic containers with 20mm of sediment and seawater at 14°C. For each trial a naked (no shell) crab was placed at one end of the container with a number of randomly arranged empty shells at the opposite end. Shell occupation was recorded at 1,2,3,6,12,24 and 48 hours - at which the shell occupied was classified as the preferred shell.
1. Shell species preference trials
Shell species preferences of P. handrecki and M. acantholepis were investigated using choice and no-choice trials:
No-choice trials:
A single naked crab was placed in a container equidistant from 3 Bittium granarium or 3 Maoricolpus roseus shells which differed in size (one ~4mm smaller, one ~ 4mm larger and one approx the same size as the crabs original shell). There were 17 replicates for both shell species.
Choice trials
Individual crabs were offered a single shell of each species available at Pirates Bay (Nassarius nigellus, Bittium granarium, Phasianotrochus irisidontes and Maoricolpus roseus. There were 32 replicates for this trial.
2. Utilisation of Maoricolpus roseus shells by hermit crabs
M. roseus shells were used to investigate preference for shell size and condition by hermit crabs.
Shell condition
Shell condition (aperture damage, spire damage and epibiont fouling) was classified. Experiment 1: individual hermit crabs were given 3 shells of equal condition, but differing in length. Each level of condition was replicated 15 times. Experiment 2: same shell length, but varying levels of condition (for each condition parameter (spire damage=32 replicates, aperture damage=24 replicates, epibiont fouling=28 replicates).
Shell size
Experiment 1: Naked hermit crabs offered 5 different sized shells. Shells offered in an arc, equal distances from the individual. 35 replicates. Experiment 2: Examined a trade-off between shell size and availability. 10 crabs (similar size) were simultaneously offered 20 shells (10 were expected size, 10 were larger than expected size).
Competition for Maoricolpus rosues shells
Three competition experiments:
1: 150 naked P. tuberculatus were offered 40 shells of each 5mm size class (14 classes, 560 shells).
2: 62 naked P.handrecki were offered 40 shells of each 5mm size class (14 classes, 560 shells).
3: 150 P. tuberculatus and 49 P. handrecki were placed in aquaria simultaneously and offered 40 shells of each 5mm size class (14 classes, 560 shells).
Statement: A sub-sample of approx 300 Maoricolpus roseus shells were used from each site.
Shell length and width were measured to the nearest 0.1 mm using Vernier callipers (shell length = longest distance of the shell from apex to anterior and width = widest part, below aperture).
Shell weight was measured to the nearest 0.01g after drying at 110°C for 24 hours.
Spire damage was given a relative score of 0-3.
Shells were also scored as live, dead and available or dead and unavailable.
Shells were broken, and if hermit crabs were present, they were identified to species, sexed and carapace measured with Vernier callipers to the nearest 0.1mm.
Notes
CreditSchool of Zoology, University of Tasmania
Credit
Natural Heritage Trust (NHT) Grant
Natural Heritage Trust (NHT) Grant
Purpose
To examine the association between Maoricolpus roseus and hermit crabs - and thereby identify potential impacts of this introduced screwshell on native populations of hermit crabs in eastern Tasmania - specifically looking at shell preferences for occupancy and utilisation of M. roseus shells by species of hermit crabs: Pagurixus handrecki and Micropagurus acantholepis, and the larger P. tuberculatus.
To examine the association between Maoricolpus roseus and hermit crabs - and thereby identify potential impacts of this introduced screwshell on native populations of hermit crabs in eastern Tasmania - specifically looking at shell preferences for occupancy and utilisation of M. roseus shells by species of hermit crabs: Pagurixus handrecki and Micropagurus acantholepis, and the larger P. tuberculatus.
Created: 27 05 2008
Data time period: 2003 to 2003
text: westlimit=147.3284; southlimit=-43.0603; eastlimit=147.9425; northlimit=-43.0353
text: uplimit=15; downlimit=6
Subjects
24 079001 |
ANIMALS/INVERTEBRATES |
ARTHROPODS |
BIOLOGICAL CLASSIFICATION |
Biological Sciences |
Crustaceans |
EARTH SCIENCE |
Ecological Applications |
Ecology |
Environmental Sciences |
Hermit crab occupancy |
Invasive Species Ecology |
Mollusks |
Maoricolpus roseus |
Marine and Estuarine Ecology (Incl. Marine Ichthyology) |
Shell length |
Shell weight |
Shell width |
biota |
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Other Information
Identifiers
- global : af4559e0-2c70-11dd-bcd1-00188b4c0af8
