Host Fish Associations for Two Highly Imperiled Mussel Species from the Southwestern United States: Cyclonaias necki (Guadalupe Orb) and Fusconaia mitchelli (False Spike)

Authors: Jack Dudding, Michael Hart, Jennifer Khan, Clinton R. Robertson, RoelLopez, and Charles R. Randklev

Most freshwater mussels (Unionidae) require a speciﬁc host ﬁsh to advance their life cycle.

Currently, hosts are known for only one-third of the mussel species endemic to the United States and

Canada. Texas boasts the greatest diversity of freshwater mussels in the southwestern United States.

However, information on mussel-host relationships for ~52 species known to occur within the state is

either lacking or incomplete, including two species, Cyclonaias necki (Guadalupe Orb) and Fusconaia

mitchelli (False Spike), currently under review for listing under the U.S. Endangered Species Act. To

address this deﬁciency, we conducted laboratory trials that tested 12 ﬁsh species (four families and 11

genera) for C. necki and eight species (four families and seven genera) for F. mitchelli.ForC. necki,we

identiﬁed four host species, Ictalurus punctatus (Channel Catﬁsh), Pylodictis olivarus (Flathead Catﬁsh),

Noturus gyrinus (Tadpole Madtom), and Ameiurus natalis (Yellow Bullhead). The transformation period

was 11 to 22 d for I. punctatus (peak metamorphosis at 15 d), 16 d for P. olivaris and A. natalis, and 10 d

for N. gyrinus.ForF. mitchelli, we identiﬁed two host species, Cyprinella lutrensis (Red Shiner) and

Cyprinella venusta (Blacktail Shiner); for both, the transformation period was 18 d. Current

information on the status of these six host species within the Guadalupe River suggests that

imperilment of C. necki and F. mitchelli may be partly related to the status of their host ﬁshes. Our

results also provide critical information for informing recovery activities, such as translocation and

captive propagation, if deemed necessary for one or both mussel species.