Feeding and growth of Asellus aquaticus (Isopoda) on food items from the littoral of Windermere, including green leaves of Elodea canadensis

Abstract

In the laboratory, Asellus aquaticus .devoured intact green leaves from growing shoots of the aquatic macrophyte Elodea canadensis. in four collections of A. aquaticus on Elodea in a lake (Windermere), c. 20% of the specimens contained in their guts fragments of green Elodea leaves; this material and pieces of oak (Quercus) were identified from characteristic leaf hairs. Some specimens had also eaten the filamentous alga Oedogonium. Fluorescence microscopy is a useful aid for screening Invertebrates that may have eaten living plant tissues.Immature A. aquaticus, with an initial mean body length of c. 3 mm, wet weight c. 1 mg, were grown through sexual maturity over a 49-day period at 15°C in a series of twenty-two experiments (six to twelve isolated specimens in each experiment) comparing growth rates on different foods, including instances where no food was given. Animals were fed on a variety of items collected from the littoral of Windermere, plus some laboratory cultures of algae and bacteria. The highest mean specific growth rate (5.8% day"') was obtained on young Elodea leaves mechanically shaken to remove epiphytes. Other diets yielding fast growth rates (3.7-5.3%day"') were young growing leaves oi Elodea with few epiphytes and older green and brown living leaves covered with a thick growth of epiphytic algae, epiphytic algae removed from Elodea., plastic imitation Elodea immersed in the lake until covered with attached algae, epilithic algae on stones, Oedogonium, and decaying oak leaves. Slower growth (l.3-2.2%day"') and poorer survival was obtained on the following: a pure culture of the bacterium Sphaerotilus natans; cultured bacteria from lakewater; the filamentous algae Gadophora and Stigeoclonium both with and without epiphytes; faecal matter from Asellus; freshly killed Asellus; lake sediment. Some growth (mean = 0.7% day"') and 50% survival for 21 days occurred in 'starved' animals kept in filtered, sterilized lakewater. Better survival and slightly faster growth (1.0-1.5%day"') occurred in 'starved' animals kept in filtered and unfiltered lakewater.Growth of A. aquaticus was also experimentally determined from birth in animals fed on young green Elodea leaves and on decaying oak leaves. On both diets, growth was curvilinear and approximately exponential from birth to sexual maturity reached at c. 2mg wet weight in 46-60 days at \5°C. In older specimens the relative growth rate gradually fell over a period of 50 days, representing a more linear phase of growth during sexual maturity.

Toxicokinetics and Bioconcentration of Polycyclic Aromatic Hydrocarbons in Freshwater Isopods

“…The extremely low elimination rate constants for pyrene and benzo[ghi]perylene in the peripheral compartment signify that some PAHs are strongly bound in stable compartments and probably will never leave the organism during its normal life span. In feeding experiments relative growth rates of 0.01-0.05 day -1 have been determined for freshwater isopods (45). It may be expected that growth dilution is an important factor leading to a reduced apparent bioconcentration of slowly exchanging compounds in the field situation.…”

Polycyclic Aromatic Hydrocarbons in Freshwater Isopods and Field-Partitioning Between Abiotic Phases

“…In toxicokinetic experiments with PAHs in A. aquaticus elimination rate constants decreased with increasing K ow (Van Hattum and Cid Montañés 1998). Using relative growth rate values for freshwater isopods (0.01-0.05 day Ϫ1 ) reported by Marcus et al (1978), it can be demonstrated that growth dilution is likely to restrain the maximum apparent bioconcentration. This may have been the case for compounds with elimination rate constants less than 0.01-0.05 day Ϫ1 , which were observed for PAHs with 5 Ͻ log K ow Ͻ 6.…”

“…The suitability of the benthic invertebrate Asellus aquaticus (L.) as a model species for the monitoring of the bioavailability of sediment-bound trace metals has been previously demonstrated (Van Hattum et al 1991. Freshwater isopods are widely distributed in littoral habitats of many meso-and eutrophic waters in the northern hemisphere and usually represent an important food source for predatory invertebrates, fish, and waterfowl (Williams 1962;Marcus et al 1978). Previous work of our group on the bioconcentration and toxicokinetics of chlorpyrifos (Cid Montañés et al 1995) and PAHs (Cid Montañés 1994;Van Hattum and Cid Montañés 1998) indicated an absent biotransformation activity in A. aquaticus (L.).…”

Review and comparison of available testing approaches and protocols for testing effects of chemicals on sediment‐dwelling organisms with potential applicability to pesticides

“…Asellus aquaticus has a one year life-cycle with increased growth rate at higher temperatures (Okland, 1978) and sexual maturity reached within 60 days at a temperature of 15 o C (Marcus et al 1978). A further 150-200 days is required for production of the next generation and each female produces 1-2 broods and the number of eggs produced can range from 21-100 as female length increases (Steel, 1961).…”

“…Asellus aquaticus has been suggested as a suitable species for use in sediment toxicity tests, since it is in continuous contact with the sediment and feeds on detritus (Marcus et al 1978).…”