Midshipman fish
Encyclopedia
The midshipman fishes are the genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 Porichthys of toadfishes. They are distinguished by having photophore
Photophore
A photophore is a light-emitting organ which appears as luminous spots on various marine animals, including fish and cephalopods. The organ can be simple, or as complex as the human eye; equipped with lenses, shutters, color filters and reflectors...

s (which they use to attract prey and after which they are named, reminding some of a naval uniform's buttons) and four lateral line
Lateral line
The lateral line is a sense organ in aquatic organisms , used to detect movement and vibration in the surrounding water. Lateral lines are usually visible as faint lines running lengthwise down each side, from the vicinity of the gill covers to the base of the tail...

s. Typical midshipman fishes, such as the Plainfin Midshipman, are nocturnal and bury themselves in sand or mud of the intertidal zone during the day. At night they float just above the seabed. Some species are armed with venomous dorsal spines and are capable of inflicting serious injuries if handled.

Mating in midshipman fishes depends on auditory communication; males during the breeding season broadcast a sound usually described as a hum, generated by rapid contractions of the muscles in the swim bladder. The sound can be kept up for up to an hour, and is loud enough to be heard by (and to puzzle) people on nearby land and houseboats; the hulls of the boats tend to amplify the sound to sleep-disrupting levels. Reproductive females develop a selective sensitivity to this sound, and respond by laying eggs in the rock nest of a singing male.

Researchers from the University of Washington
University of Washington
University of Washington is a public research university, founded in 1861 in Seattle, Washington, United States. The UW is the largest university in the Northwest and the oldest public university on the West Coast. The university has three campuses, with its largest campus in the University...

 and Cornell University
Cornell University
Cornell University is an Ivy League university located in Ithaca, New York, United States. It is a private land-grant university, receiving annual funding from the State of New York for certain educational missions...

 have recently demonstrated that the increase in sensitivity associated with female reproductive status can be duplicated in non-reproductive females of the Plainfin Midshipman (Porichthys notatus) by boosting hormone levels, and that this acts on the fish's inner-ear
Ear
The ear is the organ that detects sound. It not only receives sound, but also aids in balance and body position. The ear is part of the auditory system....

 to produce the change in sensitivity. An increase in levels of the hormones testosterone
Testosterone
Testosterone is a steroid hormone from the androgen group and is found in mammals, reptiles, birds, and other vertebrates. In mammals, testosterone is primarily secreted in the testes of males and the ovaries of females, although small amounts are also secreted by the adrenal glands...

 and estradiol
Estradiol
Estradiol is a sex hormone. Estradiol is abbreviated E2 as it has 2 hydroxyl groups in its molecular structure. Estrone has 1 and estriol has 3 . Estradiol is about 10 times as potent as estrone and about 80 times as potent as estriol in its estrogenic effect...

 triggers changes that result in increased sensitivity to higher sound frequencies.

There are about 15 species of midshipman fishes, including the following:
  • Darkedge midshipman, Porichthys analis
  • Porichthys bathoiketes
  • Saddle midshipman, Porichthys ephippiatus
  • Greene's midshipman, Porichthys greenei
  • Porichthys kymosemeum
  • Daisy midshipman, Porichthys margaritatus
  • Mimetic midshipman, Porichthys mimeticus
  • Specklefin midshipman, Porichthys myriaster
  • Plainfin midshipman, humming toadfish, or California canary fish, Porichthys notatus
  • Smalleye midshipman, Porichthys oculellus
  • Porichthys oculofrenum
  • Porichthys pauciradiatus
  • Atlantic midshipman, Porichthys plectrodon
  • Porichthys porosissimus
  • Porichthys queenslandiae

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