Evaluation of a nonlethal technique for hemolymph collection in Elliptio complanata, a freshwater bivalve (Mollusca: Unionidae)

Abstract

Hemolymph, the circulatory fluid of bivalves, transports nutrients, respiratory gases, enzymes, metabolic wastes, and toxicants throughout the body. Hemolymph can provide information pertinent to health assessment of animals or populations, but is not commonly used in freshwater bivalves partly because of the lack of tested, practical techniques for its nonlethal collection. The objective of this study was to evaluate the effect of hemolymph collection on the growth and survival of Elliptio complanata, a freshwater bivalve (Unionidae). We describe a simple technique for the collection of hemolymph from the anterior adductor muscle sinus of E. complanata. To evaluate the effect of hemolymph sampling on mussel survival and growth, 30 mussels sampled using the technique and 30 unsampled controls were followed for 3 mo post collection. Nine animals were sampled 3 times over 7 mo to monitor effects of repeated sampling. No negative impacts on survival or growth were observed in either the singly or repeatedly sampled animals. We also compared the composition of hemolymph collected from the adductor muscle sinus with that collected from the ventricle of the heart. Calcium levels and cell count of hemolymph obtained from the adductor sinus and ventricle were significantly different. There was no significant difference between collection sites for magnesium, phosphorus, ammonia, protein, sodium, potassium, or chloride. We conclude that collection of hemolymph from the adductor sinus is safe for sampled E. complanata and should be explored as a relatively non-invasive, and potentially useful, approach to the evaluation of freshwater mussel health.KEY WORDS: Unionidae · Freshwater mussels · Hemolymph · Nonlethal sampling Resale or republication not permitted without written consent of the publisherDis Aquat Org 65: [159][160][161][162][163][164][165] 2005 water mussels play roles in water filtration, bioturbation, and nutrient cycling and retention (Hauer & Lamberti 1996). They are also food sources for many riparian and aquatic animals (McMahon & Bogan 2001).Health assessment of freshwater bivalves traditionally involves lethal tissue collection from animals for histology (Chittick et al. 2001), contaminant (Muncaster et al. 1990, Cope et al. 1999, enzymatic (Doran et al. 2001, McMahon & Bogan 2001 or energy analysis (Baker & Hornbach 2000, McMahon & Bogan 2001. These techniques have successfully identified unionid populations suffering the impacts of dramatic localized habitat degradation (Foe & Knight 1987) or major infestations of invasive species (Baker & Hornbach 2000). In these situations, because a large proportion of a localized population is affected, only a relatively small number of animals need be sampled to identify the health effect.However, many devastating environmental threats are more insidious, with diffuse impacts. Health effects may be subtle and initially present a picture of low prevalence. Sampling restrictions on endangered or threatened populations limit access to these animals for ...

Temporal and spatial variability in stable isotope compositions of a freshwater mussel: implications for biomonitoring and ecological studies

“…Non-lethal collection of hemolymph is a relatively simple procedure (Gustafson et al 2005b) and seems a suitable alternative to the more-invasively sampled foot tissue for estimation of 15 N composition. Our calculations of inter-population variability (Lancaster and Waldron 2001) for E. complanata reveal the CV (5%) is reasonable for foot tissue and whole hemolymph in cohort sizes of Wve and six animals, suggesting that relatively small sample sizes may provide reasonable estimates of a population mean.…”

“…At each visit we collected a water sample for Wltration and water 15 N-NO 3 and particulate organic 15 N analysis. We targeted whole hemolymph for this translocation study because repeated collection is non-lethal (Gustafson et al 2005b), much less invasive than tissue biopsy, and does not depend upon Weld access to a centrifuge. Duplicate hemolymph samples were collected from one of the cohorts of six mussels to evaluate sampling variability.…”

“…Bivalves have an open circulatory system: the circulatory Xuid, called hemolymph, bathes tissues directly via large open spongy sinuses (McMahon and Bogan 2001) rather than diVusion through a complicated system of veins and arteries. Freshwater mussels have large hemolymph volumes for their size (McMahon and Bogan 2001), and this Xuid is easily and safely collected from the sinus of the anterior adductor muscle, the surface of which is visible through slightly gaping valves (Gustafson et al 2005b). Paired foot tissue and whole hemolymph samples were collected from all 47 animals.…”

“…At these two sites, animals were collected where their availability was greatest (above the crossing at one site, and below at the other). A biopsy of foot tissue was taken nonlethally from each animal from each stream with ophthalmic surgical scissors through slightly open shell valves (Gustafson et al 2005b). Animals were returned to their streams of origin directly after tissue collection.…”

Enhanced trace element concentrations in tissues of the clam <em>Ruditapes decussatus</em> transplanted to areas influenced by human activities (Ria Formosa, Portugal)

“…Osmolarity and pH were determined in the hemolymph collected immediately after sampling from the foot and adductor muscle of ten clams with a 21G needle and 1-mL syringes. Then, it was centrifuged for 10 min (4500 g, 4°C), snap-frozen in liquid nitrogen and stored at -80°C until analysis (Gustafson et al 2005).…”