Coelenterata (Cnidaria) Characteristics

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Questions and Answers

In cnidarians exhibiting metagenesis, what is the underlying genetic or epigenetic mechanism that governs the alternation between polyp and medusa forms, considering the differential gene expression patterns required for each morphology?

Telomere shortening in polyps that triggers a cascade of cellular senescence, ultimately leading to medusa transformation.
Reversible DNA methylation patterns that selectively silence genes responsible for polyp characteristics during medusa formation and vice versa. (correct)
Complete chromosomal elimination during the transition from polyp to medusa, resulting in a reduced genome size in the medusa form.
Horizontal gene transfer from symbiotic organisms that introduces novel genes responsible for medusa formation.

The nematocysts of all cnidarians are uniformly composed of cnidocil-triggered tubules that evert to deliver toxins, irrespective of the specific ecological niche or prey preference of the cnidarian species.

False (B)

Propose a novel mechanism by which a sessile polyp could enhance its evolutionary fitness in a highly competitive marine environment, considering the limitations imposed by its immobility and the need to acquire resources efficiently.

The polyp could develop a symbiotic relationship with chemosynthetic bacteria to gain nutritional independence from the fluctuating plankton supply characteristic of many marine habitats. Furthermore, the bacteria could produce localized concentrations of toxic metabolites that deter predators and hinder the growth of other organisms that compete for space and other resources.

In cnidarians that possess both polyp and medusa stages in their life cycle, the transition between these forms often involves a complex interplay of environmental cues and hormonal signals. Specifically, the differentiation of a medusa from a polyp is frequently triggered by a surge in ___________ hormone levels, which activates a cascade of downstream transcription factors that promote the expression of genes essential for medusa morphology.

Thyroid Signup and view all the answers

Match the following cnidarian species with their predominant mode of prey capture and feeding strategy:

Physalia physalis = Employs a pneumatophore to float on the surface of the water and uses long, venomous tentacles to ensnare and paralyze fish and other relatively large prey. Metridium senile = Utilizes numerous cilia on its tentacles to generate water currents that draw plankton and other small particulate matter towards its mouth for suspension feeding. Gorgonia ventalina = Relies heavily on symbiotic zooxanthellae for nutrition, supplementing their energy needs through the absorption of dissolved organic matter from the surrounding water. Obelia dichotoma = Exhibits both polyp and medusa stages, with the polyps capturing small invertebrates using nematocysts, and the medusae preying on planktonic organisms. Signup and view all the answers

If a novel neurotoxin is isolated from a species of box jellyfish (Chironex fleckeri), and this toxin is found to selectively disrupt the function of voltage-gated sodium channels in mammalian cardiomyocytes without affecting neuronal sodium channels, what are the most likely implications for the development of an antidote?

Due to the toxin's selective action on cardiac sodium channels, an effective antidote would likely need to target cardiac-specific sodium channels, minimizing potential neurological side effects. (D) Signup and view all the answers

The alternation of generations (metagenesis) observed in some cnidarians is solely driven by environmental factors such as temperature and nutrient availability, without any underlying genetic or epigenetic control mechanisms.

False (B) Signup and view all the answers

Describe the potential consequences of ocean acidification on the skeletal structure and overall fitness of coral species within the phylum Cnidaria, and propose a specific molecular mechanism by which certain coral species might exhibit greater resilience to these effects.

Ocean acidification reduces the saturation state of calcium carbonate, hindering coral calcification and skeletal growth. This leads to weaker skeletons, increased vulnerability to erosion, and decreased resilience to storms and other disturbances. Some coral species might exhibit greater resilience by upregulating the expression of genes involved in bicarbonate transport, allowing them to more efficiently extract carbonate ions from the surrounding seawater and maintain internal pH levels conducive to calcification. Signup and view all the answers

Flashcards

Coelenterata (Cnidaria)

Aquatic animals, mostly marine, with radial symmetry.

Cnidoblasts (Cnidocytes)

Cells containing stinging capsules (nematocysts) used for anchorage, defense, and prey capture.