Bernard E. Sietman

Relic Populations of the Ebony Shell, Fusconaia ebena (Bivalvia: Unionidae), in the Upper Mississippi River Drainage

ABSTRACT The ebony shell (Fusconaia ebena) is extirpated from much of the upper Mississippi River drainage. Nonetheless, in the past 25 years 94 live individuals were collected at 23 sites in the upper Mississippi River between Lock and Dam 6 and 26, three sites in the lower St. Croix River, and one site in the lower Wisconsin River. Most of the recent records were from the lower St. Croix River and the lower reaches of the upper Mississippi River. These data support the hypothesis that Lock and Dam 19 inhibits F. ebena from recolonizing the Mississippi River above the dam by preventing its migratory host fish, skipjack herring (Alosa chrysochloris), from moving upstream. Populations above Lock and Dam 19 are probably pre-lock and dam remnants that have persisted for over a half century and are at risk of extirpation. Conservation efforts should focus on artificial propagation and dam modifications that allow the passage of migratory fishes.

Post-Extirpation Recovery of the Freshwater Mussel (Bivalvia: Unionidae) Fauna in the Upper Illinois River

ABSTRACT Freshwater mussels are recolonizing the upper Illinois River following their extirpation by pollution in the early part the 20th century. From 1990 to 1999, we collected 332 individuals of 18 species between river miles 232.0 and 271.2. Age structure of the community suggests mussels began recolonizing in the early 1980s, which coincides with improvements in water quality and the upper river fish community. We found four sites with five or more species, which we considered to be recently formed mussel beds. We collected live individuals of six species (Actinonaias ligamentina, Alasmidonta marginata, Lampsilis cardium, Lasmigona costata, Pleurobema sintoxia, and Strophitus undulatus) thought to have been extirpated from the entire Illinois River mainstem, and one species (Anodonta suborbiculata) that has recently expanded its range into the upper river. Upper Illinois River tributaries and lower reaches of the Illinois River harbored source populations for the recolonizing mussels. Although the present community does not approximate the pre-disturbance fauna, these data show that given adequate time and improved conditions, mussel communities may recover from a devastating disturbance.

Muskrat (Ondatra zibethicus) Predation on Zebra Mussels (Dreissena polymorpha) Attached to Unionid Bivalves

ABSTRACT Muskrats (Ondatra zibethicus) commonly prey upon unionid bivalves, discarding the empty shells in discrete piles or middens. We found large numbers of live unionids and the shell remains of zebra mussels (Dreissena polymorpha) in muskrat middens on the upper Ohio River and upper Mississippi River. Muskrats apparently began preying on zebra mussels that were attached to unionids following an increase in zebra mussel abundance at the study sites. Significantly fewer zebra mussels were attached to live unionids at muskrat middens than to ones collected from reference sites away from middens. We also found a group of stones with numerous zebra mussel byssal threads at an Ohio River midden, suggesting muskrats retrieved and ate the attached zebra mussels. We view this, as well as the fact that muskrats discarded live unionids, as evidence that muskrats were selectively preying on zebra mussels rather than unionids.

Pyganodon (Bivalvia: Unionoida: Unionidae) phylogenetics: a male- and female-transmitted mitochondrial DNA perspective.

Species boundaries, evolutionary relationships and geographic distributions of many unionoid bivalve species, like those in the genus Pyganodon, remain unresolved in Eastern North America. Because unionoid bivalves are one of the most imperiled groups of animals in the world, understanding the genetic variation within and among populations as well as among species is crucial for effective conservation planning. Conservation of unionoid species is indispensable from a freshwater habitat perspective but also because they possess a unique mitochondrial inheritance system where distinct gender-associated mitochondrial DNA lineages coexist: a female-transmitted (F) mt genome and a male-transmitted (M) mt genome that are involved in the maintenance of separate sexes (=dioecy). In this study, 42 populations of Pyganodon sp. were sampled across a large geographical range and fragments of two mitochondrial genes (cox1 and cox2) were sequenced from both the M- and F-transmitted mtDNA genomes. Our results support the recency of the divergence between P. cataracta and P. fragilis. We also found two relatively divergent F and M lineages within P. grandis. Surprisingly, the relationships among the P. grandis specimens in the F and M sequence trees are not congruent. We found that a single haplotype in P. lacustris has recently swept throughout the M genotype space leading to an unexpectedly low diversity in the M lineage in that species. Our survey put forward some challenging results that force us to rethink hybridization and species boundaries in the genus Pyganodon. As the M and F genomes do not always display the same phylogeographic story in each species, we also discuss the importance of being careful in the interpretation of molecular data based solely on maternal transmitted mtDNA genomes. The involvement of F and M genomes in unionoid bivalve sex determination likely played a role in the genesis of the unorthodox phylogeographic patterns reported herein.

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.

Distribution of the Non-Native Viviparid Snails, Bellamya chinensis and Viviparus georgianus, in Minnesota and the First Record of Bellamya japonica from Wisconsin

ABSTRACT We documented the currently known distribution of the Asian snail Bellamya (=Cipangopaludina) chinensis in Minnesota, along with another viviparid snail, Viviparus georgianus, a North American native whose range has expanded. We also recorded the first known occurrence of Bellamya japonica in Wisconsin. Bellamya chinensis and V. georgianus occurred predominately in lakes within the MinneapolisISt. Paul metropolitan area and the lakes region of northcentral Minnesota. Both species are now established in the three major watersheds that drain Minnesota. We collected Bellamya japonica at six sites in the Namekagon River, part of St. Croix River system in Wisconsin.

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.

Colonization of Bedrock by Freshwater Mussels (Bivalvia: Unionidae)

Abstract We document the occurrence of freshwater mussels living on bedrock, a substrate generally considered to be unsuitable. We found 54 individuals of six species in this habitat. Our observations support the hypothesis that substrate stability is an important component of mussel habitat.

The extremely divergent maternally- and paternally-transmitted mitochondrial genomes are co-expressed in somatic tissues of two freshwater mussel species with doubly uniparental inheritance of mtDNA

Freshwater mussel species with doubly uniparental inheritance (DUI) of mtDNA are unique because they are naturally heteroplasmic for two extremely divergent mtDNAs with ~50% amino acid differences for protein-coding genes. The paternally-transmitted mtDNA (or M mtDNA) clearly functions in sperm in these species, but it is still unknown whether it is transcribed when present in male or female soma. In the present study, we used PCR and RT-PCR to detect the presence and expression of the M mtDNA in male and female somatic and gonadal tissues of the freshwater mussel species Venustaconcha ellipsiformis and Utterbackia peninsularis (Unionidae). This is the first study demonstrating that the M mtDNA is transcribed not only in male gonads, but also in male and female soma in freshwater mussels with DUI. Because of the potentially deleterious nature of heteroplasmy, we suggest the existence of different mechanisms in DUI species to deal with this possibly harmful situation, such as silencing mechanisms for the M mtDNA at the transcriptional, post-transcriptional and/or post-translational levels. These hypotheses will necessitate additional studies in distantly-related DUI species that could possess different mechanisms of action to deal with heteroplasmy.