Extralimital Species

Species present outside the metro area but within the adjacent northeast region are included to provide a more complete picture of the local fauna

Family Dreissendae

Status:

Two species of the genus Dreissena occur in North America. Both are established invasives. D. bugensis is confined to the eastern Great Lakes and the St. Lawrence River, and reaches only the northern edge of the region. It does not occur in the metro area. By contrast, the zebra mussel D. polymorpha is abundant in the metro area, and is distributed widely throughout the eastern and midwestern US, reaching from Quebec (Canada) south on the Atlantic slope to Georgia, and west to Minnesota, Oklahoma and Louisiana.

Note: Although not extralimital to the metro area, D. polymorpha is described here with its sister species for convenience; it is also included among the descriptions of the other metro area species.

Species Summaries

Dreissena bugensis (Andrusov, 1897)
quagga mussel

Features:

size: 40mm
beak: pointed
color patterns: dark, irregular stripes
shape: outer margin evenly curved, posterior end and ventral surface rounded
shell features: valves attached by an internal hinge ligament (byssus); ventrolateral shoulder reduced or absent
teeth: absent

Status:

abundance: uncommon
status: US, NY, NJ, CT: not legally protected
conservation challenges: D. bugensis does not appear to present the problems of explosive population growth, damage to power plants and displacement of native species caused by the zebra mussel

Distribution:

N.A. distribution: Lake Ontario (Canada), the eastern Great Lakes, and the St. Lawrence River
present metro distribution: absent
other regional localities: NY: Lake Ontario, Lake Erie, western St. Lawrence River; CT: does not occur

Life History:

habitat: large rivers and lakes with a hard substrate; this species shows some tolerance of salinity, and a limited tolerance of acidity and low calcium content
hosts: no host required; free-swimming veliger larva

Plates

D. bugensis

left view	right view
dorsal view	profile view
no teeth; hinge ligament present	dark striping reduced to spots; ends rounded

Dreissena polymorpha (Pallas, 1771)
zebra mussel

Features:

size: 40mm
beak: pointed
color patterns: dark, irregular stripes
shape: triangular in cross section, ventral surface flat, outer margin curved evenly; "D"-shaped, angled posterior end
shell features: acute shoulder laterally across ventral surface
teeth: absent; valves attached by internal hinge ligament

Status:

abundance: abundant
status: US, NY, NJ, CT: not legally protected

Distribution:

N.A. distribution: Quebec (Canada) and the lower St. Lawrence River west to the Great Lakes basin and Minnesota, south to Georgia on the Atlantic slope, and in the Mississippi River basin to Louisiana and Oklahoma;
current US range includes the states of: AK, AL, CT, IA, IL, IN, KY, LA, MD, MI, MN, MO, MS, NJ, NY, OH, OK, PA, TN, VT, WI, WV
present metro distribution: NY: lower Hudson River watershed; CT: East Twin Lakes
other regional localities: St. Lawrence River, Lake Ontario, Lake Erie, upper Hudson River, Erie Canal to the Mohawk River (upper Hudson River watershed), Susquehanna River watershed

Life History:

habitat: large rivers and lakes on any hard substrate; displays some tolerance to salinity, limited tolerance to low calcium and acidity; high tolerance to cold
hosts: no host required; free-swimming veliger larva

Plates

D. polymorpha

left view	right view
dorsal view	profile view
teeth absent	byssal thread
flattened ventrally; D-shaped posterior end	strong dark banding