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Some freshwater mussels have evolved unique mantle modifications and behaviors to lure host fish to be parasitized. A few can be seen below.

(Lampsilis cardium) - mantle flapping behavior

Lampsilis cardium) - mantle flapping behavior (different population)
Ridged Pocketbook
(Lampsilis ovata) -
mantle flapping behavior

Pink Mucket
(Lampsilis abrupta) -
mantle flapping behavior
(endangered species)

Rayed Bean
(Villosa fabalis) -
mantle display
(Toxolasma parvum) - mantle display
Unlike most populations, those from Lake Erie have mantle flaps rather than caruncles.

Black Sand Shell
(Ligumia recta) -
mantle display


Northern Riffleshell (Epioblasma torulosa rangiana)

The Northern Riffleshell captures its host, usually a darter or sculpin, between its shells. It will hold the fish for 5-10 minutes, pumping glochidia onto the fish's face. In the video watch the space below the fish for clouds of glochidia. Newly transformed juveniles

Spermatozeugmata ("sperm balls"). Freshwater mussel males release sperm in structures called spermatozeugmata. Resembling a colony of Volvox, sperm are embedded head-first in a double-layered hollow sphere. The "sperm balls" seen here are from the Giant Floater, Pyganodon grandis.

Sperm removed from the gonads. Sperm have not been incorporated into spermatozeugmata. Spermatozeugmata released by a male. Individual sperm may be seen as well.
A single spermatozeugmatum Dissociation of spermatozeugmata ("exploding sperm balls")

Although sperm are released as spermatozeugmata it is obvious that they cannot fertilize eggs in this state. How and when spermatozeugmata are dissociated into individual sperm was unknown. In a simple experiment, shown here, fluid was removed from a female's intra-branchial space and added to spermatozeugmata. The result is dramatic. In the "Dissocation" video, once the camera stops moving, note a wave of dissociation beginning in the upper left (where the fluid was added). Clearly, when spermatozeugmata contact fluid from the female's gills they dissociate and are available to fertilize eggs. We are now isolating the component of the fluid responsible for the dissociation. The mechanism of dissociation remains unknown.

Lymnaea stagnalis. We have had a colony of this species since 2003. The videos show this snail just before and after hatching from the gelatinous egg mass.

Lymnaea stagnalis just before hatching Lymnaea stagnalis newly hatched