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*Bythotrephes longimanus* typically measures over 20 millimeters in length.
Answer: False
Explanation: *Bythotrephes longimanus* is a small crustacean, typically measuring less than 15 millimeters in length.
The common name 'spiny water flea' refers to the organism's large size and aquatic habitat.
Answer: False
Explanation: The common name 'spiny water flea' refers to the organism's prominent, elongated abdominal spine and its classification as a water flea, not its size or general habitat.
The elongated abdominal spine of *Bythotrephes longimanus* is primarily used for propulsion through the water.
Answer: False
Explanation: The elongated abdominal spine of *Bythotrephes longimanus* is primarily a defensive structure, adorned with barbs, and is not used for propulsion.
Juvenile spiny water fleas possess multiple pairs of barbs on their abdominal spine, unlike adults.
Answer: False
Explanation: Adult individuals of *Bythotrephes longimanus* typically possess one to three pairs of barbs on their abdominal spine, whereas juveniles possess only a single pair.
Female spiny water fleas are significantly smaller than males, typically reaching only half their size.
Answer: False
Explanation: Female spiny water fleas are considerably larger than males, often reaching up to eight times the size of their male counterparts.
*Bythotrephes longimanus* possesses compound eyes and multiple antennae for sensory input.
Answer: False
Explanation: *Bythotrephes longimanus* possesses a single, large eye and a pair of antennae used for swimming, not multiple antennae for sensory input.
The first pair of legs on *Bythotrephes longimanus* is adapted for capturing prey.
Answer: True
Explanation: The first pair of legs in *Bythotrephes longimanus* is specialized for the capture of prey, playing a crucial role in its feeding strategy.
The term 'cladoceran' refers to a type of predatory fish found in the same habitat as the spiny water flea.
Answer: False
Explanation: 'Cladoceran' refers to a type of crustacean belonging to the order Cladocera, commonly known as water fleas, which includes *Bythotrephes longimanus*.
The spiny water flea is classified in the phylum Chordata, which includes vertebrates.
Answer: False
Explanation: The spiny water flea belongs to the phylum Arthropoda, not Chordata. Arthropods are invertebrates characterized by exoskeletons and jointed appendages.
The spiny water flea possesses a single, large, black or red eye.
Answer: True
Explanation: *Bythotrephes longimanus* is characterized by a single, large eye, which is typically black or red in coloration.
The abdominal spine of *Bythotrephes longimanus* constitutes approximately 70% of its total body length.
Answer: True
Explanation: The prominent abdominal spine of *Bythotrephes longimanus* typically accounts for approximately 70% of its total body length.
What is the common name for the crustacean *Bythotrephes longimanus*?
Answer: Spiny water flea
Explanation: The common name for *Bythotrephes longimanus* is the spiny water flea, derived from its characteristic elongated, barbed spine.
Which of the following is NOT part of the scientific classification of the spiny water flea?
Answer: Order Copepoda
Explanation: *Bythotrephes longimanus* belongs to the order Onychopoda, not Copepoda.
What is the typical maximum length of *Bythotrephes longimanus*?
Answer: 15 millimeters
Explanation: *Bythotrephes longimanus* typically measures less than 15 millimeters in length.
What is the most distinctive physical characteristic of *Bythotrephes longimanus*?
Answer: Its unusually long abdominal spine
Explanation: The most distinctive physical characteristic of *Bythotrephes longimanus* is its elongated abdominal spine, which is often barbed.
Approximately what percentage of the organism's total body length does the abdominal spine of *Bythotrephes longimanus* typically represent?
Answer: 70%
Explanation: The abdominal spine of *Bythotrephes longimanus* typically constitutes approximately 70% of its total body length.
How does the number of barbs on the spine typically differ between adult and juvenile *Bythotrephes longimanus*?
Answer: Adults usually have 1-3 pairs, while juveniles have only one pair.
Explanation: Adult *Bythotrephes longimanus* typically possess one to three pairs of barbs on their spine, whereas juveniles have only a single pair.
What is the primary difference in size between male and female spiny water fleas?
Answer: Females are up to eight times larger than males.
Explanation: Females of *Bythotrephes longimanus* exhibit significant sexual dimorphism, growing considerably larger than males, often up to eight times their size.
Which pair of appendages is specialized for prey capture in *Bythotrephes longimanus*?
Answer: First pair of legs
Explanation: The first pair of legs in *Bythotrephes longimanus* is morphologically adapted for the capture of prey.
What is the scientific name established by Leydig in 1860 for the spiny water flea?
Answer: *Bythotrephes longimanus*
Explanation: The scientific name *Bythotrephes longimanus* was established by Leydig in 1860 and is the currently accepted binomial nomenclature for the spiny water flea.
The spiny water flea belongs to which class of crustaceans?
Answer: Branchiopoda
Explanation: *Bythotrephes longimanus* is classified within the Class Branchiopoda, a group of crustaceans commonly known as fairy shrimp and water fleas.
What is the primary function of the barbs on the spiny water flea's spine?
Answer: Defense against predators
Explanation: The barbs adorning the spine of the spiny water flea primarily serve as a defense mechanism against predation.
Which of the following is a key characteristic of the phylum Arthropoda, to which *Bythotrephes longimanus* belongs?
Answer: Jointed legs and an exoskeleton
Explanation: A defining characteristic of the phylum Arthropoda is the presence of jointed appendages and a segmented body protected by an exoskeleton.
Which of the following statements about the spiny water flea's classification is accurate?
Answer: It is in the Class Branchiopoda.
Explanation: The spiny water flea, *Bythotrephes longimanus*, is accurately classified within the Class Branchiopoda.
The spiny water flea, *Bythotrephes longimanus*, is primarily found in tropical marine environments.
Answer: False
Explanation: This statement is factually incorrect. *Bythotrephes longimanus* is native to temperate freshwater ecosystems in Eurasia and has established invasive populations in North America, not tropical marine environments.
*Bythotrephes longimanus* was first detected in North America in Lake Michigan in 1975.
Answer: False
Explanation: *Bythotrephes longimanus* was first detected in North America in Lake Ontario in 1982.
The introduction of *Bythotrephes longimanus* to the Great Lakes is thought to have occurred via recreational boating activities.
Answer: False
Explanation: The introduction of *Bythotrephes longimanus* to the Great Lakes is primarily attributed to untreated ballast water discharged from international ships.
Spiny water fleas spread to new inland lakes primarily through natural water currents.
Answer: False
Explanation: Spiny water fleas spread to new inland lakes and rivers primarily through attachment to fishing equipment, such as lines, down-riggers, and nets.
The spiny water flea is native to parts of North America and South America.
Answer: False
Explanation: The spiny water flea is native to freshwater ecosystems in Northern Europe and Asia, not North and South America.
*Bythotrephes longimanus* was first discovered in the Great Lakes in 1982.
Answer: True
Explanation: The initial detection of *Bythotrephes longimanus* in the Great Lakes occurred in 1982, specifically in Lake Ontario.
In which regions is *Bythotrephes longimanus* naturally found?
Answer: Northern Europe and Asia
Explanation: The native freshwater range of *Bythotrephes longimanus* includes Northern Europe and Asia.
When and where was *Bythotrephes longimanus* first detected in North America?
Answer: 1982 in Lake Ontario
Explanation: *Bythotrephes longimanus* was first detected in North America in Lake Ontario in 1982.
What is the most likely method by which *Bythotrephes longimanus* was introduced to the Great Lakes?
Answer: Untreated ballast water from international ships
Explanation: The most probable vector for the introduction of *Bythotrephes longimanus* into the Great Lakes is untreated ballast water discharged from international vessels.
How does the spiny water flea typically spread to new inland lakes and rivers?
Answer: Via attachment to fishing equipment
Explanation: The spread of spiny water fleas to new inland water bodies is commonly facilitated by their attachment to fishing gear such as lines, down-riggers, and nets.
The primary diet of the spiny water flea consists of small fish and insect larvae.
Answer: False
Explanation: The primary diet of the spiny water flea consists of smaller planktonic organisms (zooplankton), particularly species of *Daphnia*.
An individual spiny water flea can consume up to 50 prey organisms per day.
Answer: False
Explanation: An individual spiny water flea typically consumes between 10 and 20 prey organisms per day.
*Daphnia pulicaria* is a primary component of the spiny water flea's diet.
Answer: True
Explanation: *Daphnia pulicaria* and other *Daphnia* species are indeed primary components of the spiny water flea's diet.
What is the primary food source for the spiny water flea?
Answer: Smaller planktonic organisms (zooplankton)
Explanation: The primary food source for the spiny water flea consists of smaller planktonic organisms, commonly referred to as zooplankton.
What is the approximate daily consumption rate of prey organisms for an individual spiny water flea?
Answer: 10-20
Explanation: An individual spiny water flea is capable of consuming approximately 10 to 20 prey organisms per day.
*Bythotrephes longimanus* competes with native fish species such as salmon and trout for food resources.
Answer: False
Explanation: While *Bythotrephes longimanus* competes for food resources, the specific native fish species mentioned as competitors in the source material are panfish and perch, not salmon and trout.
The barbs on the spiny water flea's spine make it an easy prey item for very small larval fish.
Answer: False
Explanation: The barbs on the spiny water flea's spine serve as a defense mechanism, deterring predation by very small larval fish.
The spiny water flea's predation on *Daphnia* has been linked to increased populations of other zooplankton species.
Answer: False
Explanation: The spiny water flea's predation on *Daphnia* is linked to declines in *Daphnia* populations and increased competition with native species, not an increase in other zooplankton populations.
The spiny water flea poses a minimal risk to aquatic ecosystems due to its small size.
Answer: False
Explanation: The spiny water flea poses a significant risk to aquatic ecosystems because its predation on zooplankton disrupts the base of the food chain, irrespective of its small size.
Since its introduction to the Great Lakes, there has been an observed increase in the late summer populations of several Cladocera species.
Answer: False
Explanation: Since its introduction, there has been an observed decrease, not an increase, in the late summer populations of several Cladocera species in the Great Lakes.
The densities of *Daphnia retrocurva* have increased in the Great Lakes following the invasion of the spiny water flea.
Answer: False
Explanation: Following the invasion of the spiny water flea, the densities of *Daphnia retrocurva* (along with *Daphnia pulicaria*) have decreased in the Great Lakes.
Which native fish species are mentioned as competing with the spiny water flea for food?
Answer: Panfish and perch
Explanation: The source material identifies panfish and perch as native fish species that compete with the spiny water flea for shared food resources.
Why are very small larval fish often unable to prey on *Bythotrephes longimanus*?
Answer: The barbs on the water flea's spine deter predation.
Explanation: The presence of barbs on the spine of *Bythotrephes longimanus* acts as a deterrent, making it difficult for very small larval fish to successfully prey upon them.
What impact has the spiny water flea's predation on *Daphnia* had on native zooplankton populations?
Answer: It has caused declines in *Daphnia* populations and competition with native species.
Explanation: The predatory activity of the spiny water flea on *Daphnia* species contributes to declines in *Daphnia* populations and intensifies competition with other native zooplankton species.
Which specific *Daphnia* species have shown decreased densities in the Great Lakes following the invasion?
Answer: *Daphnia pulicaria* and *Daphnia retrocurva*
Explanation: Following the invasion of *Bythotrephes longimanus*, notable decreases in the densities of *Daphnia pulicaria* and *Daphnia retrocurva* have been observed in the Great Lakes.
What ecological role does zooplankton play, making the spiny water flea a significant risk?
Answer: They form the foundation of aquatic food chains.
Explanation: Zooplankton are critical as they form the foundational level of most aquatic food chains, making their consumption by invasive species like the spiny water flea a significant ecological concern.
What ecological changes have been observed in the Great Lakes correlated with the presence of *Bythotrephes longimanus*?
Answer: Decreased species richness and reduced late summer Cladocera populations.
Explanation: Correlated with the presence of *Bythotrephes longimanus* in the Great Lakes, observations include decreased species richness and a reduction in late summer populations of Cladocera.
How does the spiny water flea's diet potentially disrupt aquatic ecosystems?
Answer: By preying on zooplankton, which are the base of the food chain.
Explanation: The spiny water flea's predatory consumption of zooplankton, the base of many aquatic food chains, can significantly disrupt ecosystem stability.
What ecological role does *Bythotrephes longimanus* play in the Great Lakes ecosystem, according to observed changes?
Answer: It has reduced the populations of key zooplankton species like *Daphnia*.
Explanation: Observed ecological changes in the Great Lakes indicate that *Bythotrephes longimanus* plays a role in reducing populations of key zooplankton species, such as *Daphnia*.
The eggs of the spiny water flea are highly vulnerable and cannot survive drying out.
Answer: False
Explanation: The eggs of the spiny water flea are remarkably resilient and can survive adverse conditions, including desiccation (drying out) and passage through the digestive tracts of fish.
The spiny water flea reproduces exclusively through sexual reproduction.
Answer: False
Explanation: While sexual reproduction occurs, the spiny water flea is also capable of parthenogenesis, which is a form of asexual reproduction.
How resilient are the eggs of the spiny water flea to environmental challenges?
Answer: They are quite resilient, surviving drying and passage through fish guts.
Explanation: The eggs of the spiny water flea exhibit considerable resilience, capable of enduring desiccation and surviving transit through the digestive systems of fish.
What is the significance of parthenogenesis in relation to *Bythotrephes longimanus*?
Answer: It enables asexual reproduction, contributing to population growth.
Explanation: Parthenogenesis, a form of asexual reproduction, allows *Bythotrephes longimanus* to reproduce rapidly without a mate, contributing significantly to population growth.
The fishhook water flea (*Cercopagis pengoi*) has a spine that is more robust than that of the spiny water flea.
Answer: False
Explanation: The spiny water flea (*Bythotrephes longimanus*) possesses a more robust spine, while the fishhook water flea (*Cercopagis pengoi*) has a more slender spine that terminates in a loop-like hook.
Previously, individuals of *Bythotrephes* with a straight spine were classified as *Bythotrephes cederstroemi*.
Answer: False
Explanation: Previously, individuals with a kinked spine were identified as *Bythotrephes cederstroemi*, while those with a straight spine were classified as *Bythotrephes longimanus*.
Genetic analysis confirmed that the kinked-spined form of *Bythotrephes* represents a distinct species separate from *Bythotrephes longimanus*.
Answer: False
Explanation: Genetic analysis indicated that the kinked-spined form, formerly considered *Bythotrephes cederstroemi*, is actually a variation of *Bythotrephes longimanus* produced through parthenogenesis.
The genus *Bythotrephes* is currently considered polytypic, encompassing multiple distinct species.
Answer: False
Explanation: Current genetic evidence suggests that the genus *Bythotrephes* is monotypic, containing only a single species, *Bythotrephes longimanus*.
The 2024 study by Karpowicz et al. suggests that *Bythotrephes* comprises multiple distinct species.
Answer: False
Explanation: The 2024 study by Karpowicz et al. supports the hypothesis that *Bythotrephes* comprises a single species, *Bythotrephes longimanus*.
The radiation of the *Bythotrephes* genus is estimated to have occurred primarily during the Holocene epoch.
Answer: False
Explanation: The radiation of the *Bythotrephes* genus is estimated to have occurred rapidly during the Late Pleistocene or post-glacial period, not primarily during the Holocene epoch.
Based on evolutionary reconstructions, only one potential dispersal event has been identified in the history of *Bythotrephes*.
Answer: False
Explanation: Evolutionary reconstructions identify five distinct potential dispersal events in the history of the genus *Bythotrephes*.
How does the spine of *Bythotrephes longimanus* differ from that of the fishhook water flea (*Cercopagis pengoi*)?
Answer: The spiny water flea has a more robust spine, while the fishhook water flea has a slender, loop-like hooked spine.
Explanation: While both species possess spines, *Bythotrephes longimanus* has a more robust spine, whereas *Cercopagis pengoi* (fishhook water flea) has a slender spine terminating in a hook.
What did genetic analysis reveal about the previously distinct forms *Bythotrephes longimanus* and *Bythotrephes cederstroemi*?
Answer: B. cederstroemi is a variation of B. longimanus produced through asexual reproduction.
Explanation: Genetic analyses have demonstrated that the form previously identified as *Bythotrephes cederstroemi* is actually a variation of *Bythotrephes longimanus*, arising through parthenogenesis (asexual reproduction).
Based on current genetic evidence, how many species are recognized within the genus *Bythotrephes*?
Answer: Only one species (*B. longimanus*)
Explanation: Current genetic evidence indicates that the genus *Bythotrephes* is monotypic, comprising only the single species *Bythotrephes longimanus*.
The 2024 study by Karpowicz et al. suggests that the morphological radiation of the *Bythotrephes* genus occurred during which period?
Answer: Late Pleistocene or post-glacial period
Explanation: The 2024 study by Karpowicz et al. posits that the morphological radiation of the *Bythotrephes* genus occurred rapidly during the Late Pleistocene or post-glacial period.
Which continent is considered the probable center from which *Bythotrephes* dispersed?
Answer: Europe
Explanation: Europe is considered the likely continent of origin from which the genus *Bythotrephes* dispersed into other geographical regions.
How many potential dispersal events in the evolutionary history of *Bythotrephes* were identified in recent reconstructions?
Answer: Five
Explanation: Recent evolutionary reconstructions have identified five distinct potential dispersal events within the history of the genus *Bythotrephes*.