The population in Michigan is actually a subspecies population, Epioblasma obliquata perobliqua. Another subspecies, Epioblasma obliquata obliquata has a purple nacre and does not occur in Michigan.
Epioblasma obliquata is synonomous with Epioblasma sulcata. The genus Epioblasma is synonomous with Dysnomia and Plagiola.
The middle lobe of the mantle edge has most of a bivalve's sensory organs. Paired statocysts, which are fluid filled chambers with a solid granule or pellet (a statolity) are in the mussel's foot. The statocysts help the mussel with georeception, or orientation.
Mussels are heterothermic, and therefore are sensitive and responsive to temperature.
Unionids in general may have some form of chemical reception to recognize fish hosts. Mantle flaps in the lampsilines are modified to attract potential fish hosts. How the spike attracts its fish host is unknown.
Glochidia respond to touch, light and some chemical cues. In general, when touched or a fluid is introduced, they will respond by clamping shut.
Communication Channels: chemical
Perception Channels: visual ; infrared/heat ; tactile ; vibrations ; chemical
Epioblasma sulcata is a federally Endangered species in both the United States and Canada. IUCN lists this species as Critically Endangered.
US Federal List: endangered
CITES: appendix i; appendix ii
Fertilized eggs are brooded in the marsupia (water tubes) up to 11 months, where they develop into larvae, called glochidia. The glochidia are then released into the water where they must attach to the gill filaments and/or general body surface of the host fish. After attachment, epithelial tissue from the host fish grows over and encapsulates a glochidium, usually within a few hours. The glochidia then metamorphoses into a juvenile mussel within a few days or weeks. After metamorphosis, the juvenile is sloughed off as a free-living organism. Juveniles are found in the substrate where they develop into adults.
Development - Life Cycle: metamorphosis
There are no significant negative impacts of mussels on humans.
Mussels are ecological indicators. Their presence in a water body usually indicates good water quality.
While freshwater mussels require a host fish for metamorphosis, the host for the spike is unknown.
Ecosystem Impact: parasite
In general, unionids are filter feeders. The mussels use cilia to pump water into the incurrent siphon where food is caught in a mucus lining in the demibranchs. Particles are sorted by the labial palps and then directed to the mouth. Mussels have been cultured on algae, but they may also ingest bacteria, protozoans and other organic particles.
The parasitic glochidial stage absorbs blood and nutrients from hosts after attachment. Mantle cells within the glochidia feed off of the host’s tissue through phagocytocis.
Plant Foods: algae; phytoplankton
Other Foods: detritus ; microbes
Foraging Behavior: filter-feeding
Primary Diet: planktivore ; detritivore
Historically Epioblasma obliquata was found in the Ohio River drainage and the Detroit River, however its range has been greatly reduced to one population in Indiana.
In Michigan the white catspaw was historically found in the Detroit River and Lake Erie. One specimen was collected from the Raisin River in Monroe County. This species has not been collected in Michigan waters since the 1930s.
Biogeographic Regions: nearctic (Native )
Specific habitat requirements are unknown since this species is rare. However, populations recently found were in high gradient streams in riffles with gravel. In Michigan this species was historically found in the Detroit River and Lake Erie.
Habitat Regions: freshwater
Aquatic Biomes: rivers and streams
Based on growth rings on specimens, the white catspaw probably lives up to 15 years.
Typical lifespan
Status: wild: 15 (high) years.
The catspaw is up to 5.1 cm (2 inches) long. Females are rectangular or quadrate while males are oval and elongate. The posterior ridge has a wide sulcus or depression between double ridges in males. The ridge is sharp and narrow in females. The shell is usually fairly solid and inflated. The anterior end is rounded, the posterior end bluntly pointed in males. Females have a posterior margin that is extended, truncated, with ribs and a medial notch. The dorsal margin is short and straight and the ventral margin is broadly curved in males and gently curved in females.
Umbos are full and even with the hinge line. Beak sculpture is double looped.
The periostracum (outer shell layer) is smooth, yellow to yellow-tan with fine green rays.
On the inner shell, the left valve has two pseudocardinal teeth, which are wide, elevated and serrated. The two lateral teeth are short and straight to slightly curved, and rough. The right valve has one wide, elevated and serrated pseudocardinal tooth.
The beak cavity is shallow. Although the nacre is white to purple it is iridescent at the posterior end. Michigan specimens have only had a white nacre.
In Michigan, this species could be confused with the northern riffleshell. The northern riffleshell is generally smaller and females lack serrations at the edge of the posterior end of the shell.
Range length: 5.1 (high) cm.
Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry
Sexual Dimorphism: sexes shaped differently
Unionids in general are preyed upon by muskrats, raccoons, minks, otters, and some birds. Juveniles are probably also fed upon by freshwater drum, sheepshead, lake sturgeon, spotted suckers, redhorses, and pumpkinseeds.
Unionid mortality and reproduction is affected by unionicolid mites and monogenic trematodes feeding on gill and mantle tissue. Parasitic chironomid larvae may destroy up to half the mussel gill.
Known Predators:
Age to sexual maturity for this species is unknown. Unionids are gonochoristic (sexes are separate) and viviparous. The glochidia, which are the larval stage of the mussels, are released live from the female after they are fully developed.
In general, gametogenesis in unionids is initiated by increasing water temperatures. The general life cycle of a unionid, includes open fertilization. Males release sperm into the water, which is taken in by the females through their respiratory current. The eggs are internally fertilized in the suprabranchial chambers, then pass into water tubes of the gills, where they develop into glochidia.
Breeding interval: The catspaw mussel breeds once in the warmer months of the year.
Average gestation period: 10 months.
Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal ); viviparous
Females brood fertilized eggs in their marsupial pouch. The fertilized eggs develop into glochidia. There is no parental investment after the female releases the glochidia.
Parental Investment: pre-fertilization (Provisioning); pre-hatching/birth (Provisioning: Female)
Epioblasma obliquata, commonly called the catspaw, is a species of freshwater mussel. It is native to eastern North America, where it is classified as endangered under the Endangered Species Act.[5] There are two subspecies, each with distinct morphology. Due to species rarity, the behavior of this organism is unknown beyond general freshwater mussel behavior.
This species was historically widespread in the Ohio River and Great Lakes drainage basins. Like many other North American freshwater mussels, it relies on a habitat of shallow, gravelly riffle zones in larger rivers. This oxygen-rich habitat has largely been destroyed over the past 200 years by dam construction and dredging, which caused a massive population decline.[1] Freshwater mussels also face the major threats of water temperature, water velocity, and turbidity changes.[6] These factors add great stress on the survival of these mussels in their respective environments. They change the ecophysiology of the organisms and change the way they are able to interact with their resources and surroundings.[6]
Both subspecies, the white catspaw and the purple catspaw, are critically endangered. By the time E. obliquata obliquata, the purple catspaw, was listed in 1990 under the Endangered Species Act, no surviving breeding populations were known. This changed in 1994 when a few young individuals were found in Killbuck Creek, Ohio, indicating a small breeding population. An attempt to collect young individuals was made in order to start a captive breeding program. However, to the researchers disappointment, surveys from 2006–2007 recorded a population of only 12 males and zero females. It wasn't until 2012 that researchers were able to find their first female individuals that could be used for captive breeding programs, which are now underway.[7][8]
The status of subspecies E. obliquata perobliqua, the white catspaw, is more dire. Only a single population has persisted into the modern day, found in Fish Creek, a tributary of the St. Joseph River in Indiana. At this location, only five living individuals were documented during surveys from 1975 to 1999, with the last living female recorded in 1975. Since then, surveys of Fish Creek have failed to find any living white catspaw mussels.[9]
This species exhibits variable shell characteristics, which have been taxonomically treated as either subspecies or separate species. Citing phylogeny, shell characteristics and allopatry, the Fish and Wildlife Service, supported by Williams et al. (2017),[10] has separated the purple and white catspaws into distinct species, each protected by the Endangered Species Act as an endangered species.[11]
One of the subspecies, the white catspaw, exhibits morphological differences between the sexes. The males have shells that are more oval-like and the grooves are deeper than those of the female. The shell of the females appear to resemble more of a rectangle than the oval. The outer layer of the shell is a tannish color while the iridescent interior is a pearly white. Overall, the mussel is around 2 inches.[13]
The purple catspaw has a yellow/green/brownish shell surface with a deep purple iridescent interior. This subspecies demonstrates different sex morphologies as well with the male shell narrower than the wider shell of the female. Males can be up to 70mm.[14]
Due to the rarity of both subspecies, reproduction timing is unknown. Maturation, developmental morphology, and lifespan have not been observed. These muscles are filter feeders through and consuming what food available floating through the water. Basic organismal research needs to be done on the catspaw mussel if there is any hope of reintroduction to its historical ranges.[15]
Epioblasma obliquata, commonly called the catspaw, is a species of freshwater mussel. It is native to eastern North America, where it is classified as endangered under the Endangered Species Act. There are two subspecies, each with distinct morphology. Due to species rarity, the behavior of this organism is unknown beyond general freshwater mussel behavior.
