Erpobdella octoculata

Erpobdella octoculata is a predator and exhibits scavenging behavior. It feeds primarily on chironomid larvae and oligochaetes.^[13] Due to the lack of jaws or a proboscis, this species uses a pharynx to swallow its prey whole.^[14] In a laboratory study, it was found that E. octoculata will suck in pieces of dead or wounded animals including vertebrates such as fish.^[13] In addition, when wounded chironomid larva is present, this species will uses its oral sucker to retrieve blood.^[13] Newly hatched leeches feed on insect larvae and suck the blood from injured Chironomus larvae.^[13] E. octoculata primarily hunts at night.^[15]

E. octoculata uses vermiform crawling to move across the bottoms of stony streams.^[8] Vermiform crawling involves an alternating shortening and extending of the body along the tail and oral suckers.^[16] Both suckers start off relatively distant and are attached to a stone. Then only the oral sucker lifts itself and the entire body extends before the oral sucker reattaches itself.^[16] The front of the body extends while the back shortens. Next the tail sucker lifts and the back of the body shortens.^[16] When the tail sucker attaches back to a stone or substrate, it is relatively close to the oral sucker and the body is in a scrunched c-shape.^[16] Along with vermiform crawling, E. octoculata also swims using oscillatory movements.^[8]

Many leeches contain sensillae, which sense water movement and light with photoreceptors.^[8] E. octoculata lacks developed sensillae and instead has sensory buds on its dorsal surface due to its predaceous nature and fast moving aqueous environment.^[8] Spread through the center of each annulus, these sensory buds have a round, raised appearance on the dorsum of this species. These sensory buds are composed of bipolar sensory cells, which are chemoreceptive and perceive water movement.^[17] This leech does also have a brain that is a mass of ganglia.^[8]

In addition, E. octoculata also has mechanoreceptors located in its skin. They are activated by stimulation such as touch or attacks from predators.^[8] Known predators include perch, water beetles, and caddisflies.^[18]

Freshwater leeches need to constantly remove excess water along with waste products. Nephridia are organs that function similarly to kidneys.^[8] They aid in this water and waste removal and the reabsorption of salts.^[8] Nephridia occur on each segment in the mid-body.^[6]

The life cycle of Erpobdella octoculata lasts 1–3 years.^[19] Adult leeches are distinguished by the presence of a clitellum, where its oval shaped cocoons are secreted from.^[8][20] These cocoons have approximately 5–10 eggs each.^[8] Most individuals lay cocoons within 1 year of hatching and subsequently die.^[21] If an individual does not breed after 1 year, it breeds at 2 years of age and lays cocoons for a second time at 3 years old.^[19] Variations between lengths of the life cycle can potentially be explained by environmental conditions such as water temperature, food availability and dissolved oxygen.^[5]

Since Erpobdella octoculata is a hermaphrodite, it has male and female gonopores.^[22] These gonopores have openings on the dorsum.