Academic journal article The American Midland Naturalist

Thermal Criteria for Early Life Stage Development of the Winged Mapleleaf Mussel (Quadrula Fragosa)

Academic journal article The American Midland Naturalist

Thermal Criteria for Early Life Stage Development of the Winged Mapleleaf Mussel (Quadrula Fragosa)

Article excerpt

ABSTRACT.-

The winged mapleleaf mussel [Quadrula fragosa (Conrad)] is a Federal endangered species. Controlled propagation to aid in recovering this species has been delayed because host fishes for its parasitic glochidia (larvae) are unknown. This study identified blue catfish [Ictaluris furcatus (Lesueur)] and confirmed channel catfish [Ictaluris punctatus (Rafinesque)] as suitable hosts. The time required for glochidia to metamorphose and for peak juvenile excystment to begin was water temperature dependent and ranged from 28 to 37 d in a constant thermal regime (19 C); totaled 70 d in a varied thermal regime (12-19 C); and ranged 260 to 262 d in simulated natural thermal regimes (0-21 C). We developed a quantitative model that describes the thermal-temporal relation and used it to empirically estimate the species-specific low-temperature threshold for development of glochidia into juveniles on channel catfish (9.26 C) and the cumulative temperature units of development required to achieve peak excystment of juveniles from blue catfish (383 C*d) and channel catfish (395 C*d). Long-term tests simulated the development of glochidia into juveniles in natural thermal regimes and consistently affirmed the validity of these estimates, as well as provided evidence for a thermal cue (17-20 C) that presumably is needed to trigger peak juvenile excystment. These findings substantiate our model and provide an approach that could be used to determine corresponding thermal criteria for early life development of other mussel species. These data can be used to improve juvenile mussel production in propagation programs designed to help recover imperiled species and may also be useful in detecting temporal climatic changes within a watershed.

INTRODUCTION

The winged mapleleaf mussel [Quadrula fragosa (Conrad)], which historically ranged in parts of 11 midwestern states and three major river drainages, was listed as a Federal endangered species in 1991 as a result of range restriction, small population sizes, poor recruitment and habitat alterations caused by changes in watershed land-use practices (U.S. Fish and Wildlife Service, 1991). This mussel currendy has only four known populations which are distributed from portions of the St. Croix National Scenic Riverway (Minnesota and Wisconsin) in the north to the Saline River (Arkansas) in the south. Active reproduction has been confirmed within only two populations, one each at the northern and southern extremes of the current range. Efforts to recover the species have been focused on the St. Croix River (SCR) population which is jeopardized by several factors including the spread of invasive zebra mussels [Dreissena polymorpha (Pallas)] by watercraft, rapid water level changes from dam operations and water quality deterioration as urban development expands in the SCR watershed.

Greater knowledge of fundamental mussel biology and habitat requirements is needed to better manage and conserve members of this faunal group (National Native Mussel Conservation Committee, 1998). A common impediment to the recovery of many imperiled mussels has been a lack of early life-history information, especially the identity of host fish species on which parasitic mussel glochidia (larvae) metamorphose into juveniles. Initial actions to recover the winged mapleleaf began with descriptive observations of reproductive activities. For example, Heath et al (2000) observed winged mapleleaf in the SCR for 3 y before diey described it as a late season, short-term (~5 wk) brooder that typically released its glochidia as water temperature decreased to ~ 15 C in early autumn. Most other Quadrula species are reported to brood and release glochidia over longer periods during spring and summer (Oesch, 1995; Headi et al, 2000). Therefore, the winged mapleleaf may be a hostoverwintering mussel (Watters and O'Dee, 2000) throughout much of its range.

Discovery of the reproductive timing of winged mapleleaf in the SCR facilitated laboratory trials at the University of Minnesota that screened more than 60 potential host fish species during a 5-y period (M. …

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