User:LydBo/Gonatus onyx

Reproduction and spawning [edit]
Like most cephalopods, G. Onyx are oviparous organisms, which means that they produce eggs outside of the body. Females lay their eggs from April to July, and brood them for about six to nine months until the hatchlings are ready for release in depths over 2,500 meters. During the brooding period, females live off of built-up lipids inside the digestive gland. In order to fertilize the female eggs, male squids use specialized arms to transfer packages of sperm, called spermatophores, to a female’s seminal receptacle, a specialized internal oviduct near the female’s mouth. Unlike other species of cephalopods, G. Onyx females then lay eggs in egg masses. Female G. Onyx are relatively unique as they hold the egg mass with their hooked arms due to loss of their tentacles. The females lose their tentacles after fertilization due to the inability to feed while holding their eggs. Females migrate to deep water once they lay their egg masses as a strategy to minimize the chance of encountering a predator. The eggs are surrounded by a black jelly-like substance and are contained in individual chambers connected by a thin membrane in a random orientation. Each egg is oval in shape, and range in size from 2.0 mm to 3.0 mm in length, and 1.8 mm to 2.1 mm in width. The egg mass can contain anywhere from 2,000 to 5,000 hatchlings.

Notes:

Seibel, B. A.; Hochberg, F. G.; Carlini, D. B. (2000-10-01). "Life history of Gonatus onyx (Cephalopoda: Teuthoidea): deep-sea spawning and post-spawning egg care". Marine Biology. 137 (3): 519–526. doi:10.1007/s002270000359. ISSN 1432-1793.

Seibel, Brad A.; Robison, Bruce H.; Haddock, Steven H. D. (2005-12). "Post-spawning egg care by a squid". Nature. 438 (7070): 929–929. doi:10.1038/438929a. ISSN 1476-4687.
 * females brood their eggs from April to June or July, and the eggs are though to hatch about 9 months later
 * the squid has a high lipid content in its digestive gland which is not only used for buoyancy but also as energy during the expansive brooding period
 * though to travel to depths from 1250 m - 1750 m to brood
 * hatchlings are up to 5.0 mm
 * eggs are surrounded by a black jelly-like substance and are held in their own chambers connected by a thin membrane
 * the eggs are light yellow, most likely as a result from the yolk, and are covered in black speckles, presumably from the mother's ink
 * egg length is 2-3 mm and width is 1.8 - 2.1 mm
 * can lay more than 2000 eggs in one brooding period
 * females lose their tentacles during the brooding period and instead carry the eggs in their arms
 * researchers believe that these large squid eggs and long brooding periods could be an adaptation that allows for more viable offspring that are capable of vertical migration in shallower waters for food


 * Researchers found squids carrying eggs at depths up to 2,522 m
 * the squids use hooks to hold onto the egg mass
 * the egg mass contains anywhere from 2,000-5,000 eggs
 * the mass extends from the squid's mouth to past its tentacles and forms a hollow tube
 * young squid are found in shallow waters from April-July
 * 6-9 month development cycle
 * the brooding squids do not move and have been found at great depth

Adult life and behavior[edit]
Individuals older than about 3 months move to deeper waters and change their entire lifestyle. Adult G. Onyx are solitary hunters. As they make long vertical migrations during the night, they move closer to the surface to feed on other organisms that follow the same migration. Adults of this species have been known to be cannibalistic, with some studies indicating a rate as high as 42% of prey being of the same species. This cannibalistic behavior could serve as a reason for observed solitary behavior. Cannibalism could have evolved as a way to limit reproductive competition or as a result of low food availability in the deep waters. This explains why cannibalism is more likely to occur where there are higher densities of competing squids for food. Predators and prey from cannibalism tend to occur with individuals that are the same age and size as one another. G. Onyx also preys on fish that are around the same size as the individual, mostly composed of Stenobrachius leucopsarus. The diet of juveniles is largely unknown with some studies finding a predominant crustacean diet and then a shift to nekton when mature.

Adult and juvenile behavior differences are due to the difference in light penetration of the water from living in different depths. Adults are opaque orange and white while juveniles are clear. Adults will change between these two colors as a defense mechanism during escape of potential predators. Individuals were also observed to use ink as a form of shape mimicry. They release ink in long rope-like shapes that allow the squid to be mistaken as a different animal by predators so they can plan their escape. Adults do not exhibit the fast defense behaviors seen in juveniles because they have less predation in the deeper waters and it requires more energy consumption which is a limited resource in the deep.

Hunt, J. C., and B. A. Seibel. "Life history of Gonatus onyx (Cephalopoda: Teuthoidea): ontogenetic changes in habitat, behavior and physiology." Marine Biology 136 (2000): 543-552.


 * Adults are colored opaque orange and white while juveniles are clear. Adults will change between these two colors as a defense mechanism during escape of potential predators
 * Adult and juvenile behavior differences are due to the difference in light penetration of the water from living in different depths
 * Adults do not exhibit the fast defense behaviors seen in juveniles because they have less predation in the deeper waters and it requires more energy consumption

Hoving, Henk-Jan T., and B. H. Robison. "Deep-sea in situ observations of gonatid squid and their prey reveal high occurrence of cannibalism." Deep Sea Research Part I: Oceanographic Research Papers 116 (2016): 94-98.

Bush, Stephanie L., and Bruce H. Robison. "Ink utilization by mesopelagic squid." Marine Biology 152 (2007): 485-494.
 * Cannibalism for this species could function as a result to limit reproductive competition as well as a result of low food availability in the deep waters
 * Cannibalistic behavior is more likely to occur with higher densities of competing squids for food
 * Predators and prey from cannibalism tends to occur with individuals that are the same age and size as one another


 * Adults were observed to use ink as a form of shape mimicry. They release ink in long rope-like shapes that allow the squid to be mistaken as a different animal by predators so they can plan their escape.

Range and habitat [edit]
G. onyx is a very common cephalopod that is found in the Northern Pacific Ocean, ranging from coastal California to the east coast of Japan, and are found as far north as the Bering Sea. They are one of the most abundant cephalopods found in coastal California and are distributed with a latitude from 30°N to 43°N. In these locations, they are typically found over the basin, shelf and shelf breaks, with a low variation in abundance.

The adults and juveniles inhabit different areas, with the more solitary adults tending to live in deeper water and the pack hunting juveniles preferring shallow coastal waters. They have one of the lowest seasonal variations over wide areas of the family Gonatidae. The depth distribution is bimodal and follows a certain diel rhythm. During the day they tend to stay at deeper depths with adults found from 400-1000m, with an average depth of around 700m. Younger members are found at 0-800m during the day with an average of around 400m. During the night both adults and juveniles tend to rise from the deeper water. Adults at night have a range of depths from 100-800m, with a large majority found around 400-500m. Juveniles have a smaller range of 0-500m and are more evenly spread out with most found from 0-300m. When laying eggs, female G.onyx have been found at even deeper depths. They have been observed holding egg mass in their arms between 1500 and 2600m, with one female seen brooding an egg mass in Monterey Canyon at a depth of 1590m.

Notes: [12] Elaina M. Jorgensen, Identification, distribution and relative abundance of paralarval gonatid squids (Cephalopoda: Oegopsida: Gonatidae) from the Gulf of Alaska, 2001–2003, Journal of Molluscan Studies, Volume 73, Issue 2, May 2007, Pages 155–165, https://doi.org/10.1093/mollus/eym010


 * found over the basin, shelf and shelf break
 * low variation in abundance
 * size range broader and larger size wise than other squids

[6] Hunt, J., Seibel, B. Life history of Gonatus onyx (Cephalopoda: Teuthoidea): ontogenetic changes in habitat, behavior and physiology. Marine Biology 136, 543–552 (2000). https://doi.org/10.1007/s002270050714


 * one of the most abundant cephalopods found in coastal California
 * distributed with a latitude from 30°N to 43°N

[8]Seibel, Brad A.; Robison, Bruce H.; Haddock, Steven H. D. (December 2005). "Post-spawning egg care by a squid". Nature. 438 (7070): 929. Bibcode:2005Natur.438..929S. doi:10.1038/438929a. ISSN 1476-4687.
 * observed holding egg mass in their arms between 1500 and 2600m and a female was seen brooding an egg mass in Monterey Canyon at 1590m
 * A female Gonatus onyx brooding an egg mass photographed at 1590 metres depth in Monterey Canyon