Pyrolycus jaco

Pyrolycus jaco is a species found in the Eastern Pacific Ocean off the coast of Costa Rica. This species is exclusively found in the Jacó Scar hydrothermal seep. This species is the fourth member of the Zoarcidae family associated with the deep-sea hydrothermal and methane sites in the eastern Pacific to be discovered following Thermacres andersoni and T. cerberus, Rosenblatt & Cohen 1986, and Pachycara rimae, Anderson 1989.

Little is known about the reproduction of Pyrolycus jaco. Another type of eelpout in the family Zoarcidae is the Lycenchelys sarsi, which lays about twenty to forty large (up to 5.4mm in diameter) eggs buried under the sediment found in their habitats. This number and behavior is typical of all species within Zoarcidae. Eelpouts reach their prime sexual maturity at two years old. The offspring are typically released between November and December. This fish has a gestation period of seven to eight months. This is long compared to most live-bearing fish, which average a three- to five-week gestation period. On average the female eelpouts can produce between twenty and seventy-two offspring within their lifetime. Though not much is known about the parental care habits of P. jaco, zoarcids as a group occasionally exhibit parental care characteristics. Their eggs hatch benthic larvae that are not widely dispersed. This is a likely factor in the species' extreme endemism to hydrothermal vents and methane seeps.

The Pyrolycus jaco mostly feeds on immobile invertebrates, snails, and other limpets based on the gut contents. Other zoarcids have a similar diet. This suggests that zoarcids aren't particularly active because the organisms consumed were localized and often sessile.