Mark C. Hove

A DNA-barcoding approach to identifying juvenile freshwater mussels (Bivalvia:Unionidae) recovered from naturally infested fishes

Abstract We developed a multilocus deoxyribonucleic acid (DNA)-barcoding approach to identify newly transformed juvenile mussels collected from naturally infested fishes in a federally protected waterway that is home to a diverse mussel community, the St Croix River (Minnesota/Wisconsin, USA). We used new and publicly available data downloaded from GenBank to build reference databases for identified adult mussels. We assessed the efficacy of the mitochondrial loci cytochrome oxidase c subunit I (COI) and nicotinamide adenine dinucleotide dehydrogenase subunit 1 (ND1) for DNA barcoding. We concluded that the barcoding gap between average intra- and interspecific genetic distances is wider for ND1 than for COI, but both loci perform well for species identification in character-based phylogenetic analyses. Almost every species formed a monospecific clade with high bootstrap and posterior-probability support. We obtained newly transformed juvenile mussels by collecting individuals of 3 different fish species that were infested with unionid larvae. We held the fish in aquaria until the mussels emerged naturally. We then extracted DNA and sequenced our loci of interest. When sequences from the juveniles were included in phylogenetic analyses, they grouped with single species (or, in one case, a pair of closely related species) with high bootstrap and posterior-probability support. Identifying juveniles using morphology alone is difficult and, in some cases, impossible. Therefore, our approach will be useful to researchers interested in the relationship between unionid mussels and their fish hosts.

Early Life-history and Conservation Status of Venustaconcha Ellipsiformis (Bivalvia, Unionidae) in Minnesota

ABSTRACT The ellipse, Venustaconcha ellipsiformis (Bivalvia: Unionidae), was first recorded in Minnesota from the Straight River in 1987, but we knew little of its distribution in the state, brooding behavior, glochidial host fish relationships or status. To examine these questions, we followed standard procedures to conduct an extensive, qualitative statewide mussel survey, described mantle flapping behavior from field and laboratory observations and identified suitable glochidia hosts in the laboratory and from naturally infested fishes. We found extant populations in five Mississippi River tributaries in southeastern Minnesota: the Cannon, Cedar, Root, Upper Iowa and Zumbro rivers. This appears to be the extent of its historic range in Minnesota as no valid records were found elsewhere. Among these, the largest population occurred in the headwaters of the Root River drainage, which was also the only drainage where we observed recent recruitment. Brooding V. ellipsiformis quickly flap a small mantle extension, often in response to passing shadows or jarring of the substrate, or their mantle extensions may be slowly undulated. We identified 11 fish species as suitable hosts for V. ellipsiformis glochidia in the laboratory: brook stickleback (Culaea inconstans), mottled sculpin (Cottus bairdii), slimy sculpin (C. cognatus), logperch (Percina caprodes), mud darter (Etheostoma asprigene), rainbow darter (E. caeruleum), Iowa darter (E. exile), fantail darter (E. flabbelare), Johnny darter (E. nigrum), banded darter (E. zonale) and blackside darter (P. maculata). Rainbow darter, fantail darter and blackside darter were also found naturally infested with V. ellipsiformis glochidia. Venustaconcha ellipsiformis should remain classified as a “Threatened” species in Minnesota and management should include conserving populations within drainages due to its restricted range and likely low dispersal ability.

Early Life History and Distribution of Pistolgrip (Tritogonia verrucosa (Rafinesque, 1820)) in Minnesota and Wisconsin

Abstract We conducted a series of studies to improve our understanding of pistolgrip life history and distribution in Minnesota and Wisconsin. In the St. Croix River, where this species is relatively abundant, we studied animals biweekly from May–Nov. 1997, Apr.–Oct. 1998 and nearly biweekly during May–Jul. 2004–2007 and observed gravid females between late Apr.–Jul. at water temperatures 13–25 C. Females held mature glochidia in a large mantle magazine that was significantly more inflated at night. Fifty-seven pistolgrip glochidia measured using scanning electron microscopy had an average height and length of 119 ± 6 µm and 102 ± 4 µm (±1 sd), respectively. Of 65 fish species (18 families) exposed to pistolgrip glochidia only flathead catfish (Pylodictis olivaris) and brown (Ameiurus nebulosus) and yellow (A. natalis) bullheads were suitable hosts, with flathead catfish showing the strongest host response. Glochidia grew 422 ± 17% while attached to fish. Pistolgrip is found in central and southeastern U.S. but is declining in several locations. Surveys conducted between 1980 and 2009 show the geographic range of pistolgrip has decreased in Minnesota and Wisconsin. It is extirpated from the Minnesota River and nearly so in the Mississippi River. However, we see evidence of a recovering population in a once heavily polluted reach of the Mississippi River downstream of Minneapolis-St. Paul. The largest populations are in the lower reaches of the St. Croix (MN, WI), Chippewa, Black, Wolf and Wisconsin rivers (WI). In light of the apparent close association between pistolgrip and flathead catfish, we recommend pistolgrip conservation efforts include sustainable flathead catfish management and habitat improvement to support expansion of remaining pistolgrip populations.

Effects of flow restoration on mussel growth in a Wild and Scenic North American River

BackgroundFreshwater mussels remain among the most imperiled species in North America due primarily to habitat loss or degradation. Understanding how mussels respond to habitat changes can improve conservation efforts. Mussels deposit rings in their shell in which age and growth information can be read, and thus used to evaluate how mussels respond to changes in habitat. However, discrepancies between methodological approaches to obtain life history information from growth rings has led to considerable uncertainty regarding the life history characteristics of many mussel species. In this study we compared two processing methods, internal and external ring examination, to obtain age and growth information of two populations of mussels in the St. Croix River, MN, and evaluated how mussel growth responded to changes in the operation of a hydroelectric dam.ResultsExternal ring counts consistently underestimated internal ring counts by 4 years. Despite this difference, internal and external growth patterns were consistent. In 2000, the hydroelectric dam switched from operating on a peaking schedule to run-of-the-river/partial peaking. Growth patterns between an upstream and downstream site of the dam were similar both before and after the change in operation. At the downstream site, however, older mussels had higher growth rates after the change in operation than the same sized mussels collected before the change.ConclusionsBecause growth patterns between internal and external processing methods were consistent, we suggest that external processing is an effective method to obtain growth information despite providing inaccurate age information. External processing is advantageous over internal processing due to its non-destructive nature. Applying this information to analyze the influence of the operation change in the hydroelectric dam, we suggest that changing to run-of-the-river/partial peaking operation has benefited the growth of older mussels below the dam.

Genetic Diversity of Two Common Freshwater Mussel Species, Lampsilis cardium and Quadrula pustulosa (Bivalvia: Unionidae), in a Large Federally Protected Waterway (St. Croix River, Minnesota/Wisconsin, U.S.A.)

Abstract: Freshwater mussels in the family Unionidae have suffered severe population declines because of severe anthropogenic disturbances, such as habitat destruction and habitat alteration. Understanding the genetic diversity of healthy unionid populations is crucial to developing informed management plans for imperilled mussels. Here, we characterize the genetic diversity of two common species, Lampsilis cardium Rafinesque, 1820 and Quadrula pustulosa (I. Lea, 1831), using the mitochondrial gene ND1. Populations of Q. pustulosa contained more numerous and more highly divergent haplotypes than populations of L. cardium. This disparity in genetic diversity could be because of several factors, including differences in population size and location and extent of refugia during the Last Glacial Maximum. For both species, AMOVA analysis indicated no genetic structuring based on location within the river, with genetic diversity concentrated within rather than between populations. This finding is consistent with patterns seen for other common mussel species characteristic of large rivers.

Mantle display and glochidia release behaviors of five quadruline freshwater mussel species (Bivalvia: Unionidae)

Abstract: Diverse strategies have evolved in freshwater mussels to promote the transfer of their parasitic larvae to host fish. Among these, modification of the mantle as a host attracting lure has been well-documented in the Tribe Lampsilini, but only recently reported in the Tribe Quadrulini. Here we describe mantle modifications and glochidia release behaviors in five quadruline species, including members of the Quadrula quadrula (Rafinesque, 1820), Q. pustulosa (Lea, 1831), and Q. metanevra (Rafinesque, 1820) species groups. Displays were motionless and consisted of inflated mantle tissue surrounding the excurrent aperture. Gross display morphology was largely variable among species: Q. fragosa (Conrad, 1835) and Tritogonia verrucosa (Rafinesque, 1820) had relatively large, uniquely shaped displays; Cyclonaias tuberculata (Rafinesque, 1820) and Q. pustulosa had smaller, stomate-shaped displays; and Q. metanevra had a diminutive, polyp-like display. Cyclonaias tuberculata exhibited a bimodal host infection strategy where individuals had either a mantle display or released a gelatinous conglutinate. Quadrula pustulosa and Q. metanevra expelled glochidia in a forceful burst when their displays were touched. Quadruline mantle displays do not clearly mimic identifiable aquatic organisms suggesting they may represent non-specific food items to their fish hosts.

Early Life History of the Winged Mapleleaf Mussel (Quadrula fragosa)

Abstract: Early life history information on the federally endangered winged mapleleaf (Quadrula fragosa (Conrad, 1835)) mussel is needed by natural resource managers to improve conservation and propagation programs. We conducted four studies to obtain some of this information. First, we observed Q. fragosa in the St. Croix River, Wisconsin between 1997–2010 and found females brood larvae (glochidia) for a unique period, between 8 September to 8 October at water temperatures ranging between 15–21 °C Second, we tested 67 fish species and Necturus maculosus for their ability to transform glochidia into juveniles. Nearly 30,000 juvenile Q. fragosa were produced, but only on Ictalurus furcatus and I. punctatus. Unlike most mussel species, Q. fragosa glochidia grew 3 to 4-fold while attached. Third, using scanning electron microscopy we were able to distinguish Q. fragosa glochidia height and length from six other mussel species that also produce small glochidia (<120 µm in height). Finally, we recovered 535 juveniles from 15 naturally infested fish species to determine if any were Q. fragosa based on glochidia morphology. We identified one juvenile from an I. punctatus as a Q. fragosa. To improve conservation efforts we suggest monitoring not only Q. fragosa beds but also associated Ictalurus populations, whose ranges may extend beyond mussel populations.

Early life history of the sheepnose (Plethobasus cyphyus) (Mollusca: Bivalvia: Unionoida)

Abstract Managing a rare species can be improved with knowledge of its natural history. The sheepnose (Plethobasus cyphyus) is a freshwater mussel recently listed by the US as federally endangered. We used standard methods to study P. cyphyus brooding behaviour, host fishes in the laboratory and under natural conditions, and glochidial morphology. We monitored a population of P. cyphyus in the Chippewa River, WI during spring and summer 2007–2009 and 2011 and found brooding animals between mid-May and early August. Gravid individuals ranged between 5 and 27 yr (mean age ± 1 s.d. = 13 ± 4 yr). Plethobasus cyphyus brooded glochidia in outer gills, which varied in colour from red, orange, pink, cream, or white. We observed mature glochidia more commonly in individuals with cream or white gills and these glochidia were released in a clear, adhesive, mucus matrix. In laboratory trials we found several minnow and topminnow species (29 spp.) served as productive suitable native hosts. The mean number of juvenile mussels released per cyprinid per day was significantly higher for trials conducted at 22–25°C compared with those at 18–20°C, and 83% of trials conducted at 18–20°C using suitable host species produced no juveniles. Glochidia had a unique outline and shell morphometrics that distinguished P. cyphyus from seven other Chippewa River mussel species that produce similar sized glochidia. Using morphometrics we determined that mimic shiners (Notropis volucellus) were natural hosts for P. cyphyus, round pigtoe (Pleurobema sintoxia), and Wabash pigtoe (Fusconaia flava). Releasing mucus-bound glochidia has evolved in a variety of mussel species and may be more common than is currently realized. Our data show that P. cyphyus is a cyprinid host specialist, and propagation efforts for this species can be strengthened through improved access to mature glochidia by using females with cream-coloured gills and increased juvenile production through warmer fish holding temperatures.

Host Fishes and Conservation Status of Alasmidonta marginata (Bivalvia: Unionidae) in Minnesota

Abstract We examined laboratory host suitability and assessed the distribution and status of Alasmidonta marginata (Elktoe) in Minnesota. Of the 85 fish species tested, glochidia metamorphosed on 27 species in 6 families (Cyprinidae, Catostomidae, Fundulidae, Poeciliidae, Gasterosteidae, and Cottidae). All catostomid species facilitated metamorphosis, and overall, Catostomidae produced more juvenile mussels per fish. This result, in combination with a previous finding of naturally infested fish, suggests that catostomids are an important host for A. marginata in nature. From extensive surveys, we found extant populations of A. marginata in the St. Croix River, Upper Mississippi River, and Minnesota River systems. Alasmidonta marginata is apparently extirpated or its range has decreased in several interior Minnesota watersheds and the Mississippi River main stem. Barrier waterfalls and habitat degradation have influenced A. marginatas historic and recent distribution more so than the range of its hosts. Further study of naturally occurring and laboratory hosts for A. marginata and other Alasmidonta species is needed in order to improve conservation efforts and elucidate phylogenetic relationships for this group of mussels.

Host attraction, brooding phenology, and host specialization on freshwater drum by 4 freshwater mussel species

Freshwater mussels are a diverse group of bivalves with equally diverse life-history traits. We examined host-attracting behaviors, larval-brooding phenology, and larva–host relationships for Ellipsaria lineolata, Leptodea fragilis, Potamilus alatus, and Truncilla truncata through extensive field and laboratory studies. Our data from laboratory trials and recovery and identification of juvenile mussels from naturally infected fish support the long-held assumption that freshwater drum (Aplodinotus grunniens) probably is the exclusive host for these species and is a suitable host for Potamilus ohiensis and Truncilla donaciformis. These species have subtle but distinctive host-attracting behaviors involving use of a mantle lure to facilitate larval transfer to the host. General lure morphology and movement behavior were similar between E. lineolata and T. truncata and between L. fragilis and P. alatus, species pairs that are closely related, whereas displaying orientation was variable among species. Ellipsaria lineolata, L. fragilis, and P. alatus were long-term larval brooders, but duration and correspondence with displaying activity were dissimilar. Truncilla truncata was a short-term larval brooder in the St Croix River and is among the few documented examples of short-term brooding in the Tribe Lampsilini. The range of morphological and behavioral characters in these mussels coupled with the relatively uncommon character of specializing on a single host species make this group a model for evolutionary, phylogenetic, and ecological studies.