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Black Eyed Gonate Squid

Gonatus onyx Young 1972

Comprehensive Description

provided by Smithsonian Contributions to Zoology
Gonatus onyx

Gonatus fabricii.—Berry, 1912b, [part], p.308, pl.52, fig.4.—? Pearcy, 1965, p.262.

DESCRIPTION.—The mantle is long and slender; posteriorly it tapers gradually to a pointed tip. The muscular portion of the mantle which is moderately thick terminates at the edge of the conus. A muscular cone with a gelatinous core forms a tail that extends posteriorly from the apex of the conus. This structure is not apparent in young specimens, but increases allometrically and becomes prominent in large specimens. The free margin of the mantle projects slightly at the mantle locking-cartilages.

The fins have free anterior lobes. The posterior margins are drawn out along the tail in large specimens. The lateral edges of the fins are rounded.

The funnel is free from the head laterally and reaches to approximately the level of the lenses of the eyes. Each funnel locking-cartilage bears a straight, simple groove. The dorsal pad of the funnel organ has the shape of an inverted V; the arms are broadest in the posterior portions; the anterior portions each have a median longitudinal ridge that extend to the apex. Near the anterior apex, which is blunt and slightly indented, a slender papilla arises. The ventral pads are oval. A large funnel valve is present.

The head is oval and bears large eyes that occupy the entire lateral sides of the head. An anterior sinus is present on each eyelid. Three pairs of nuchal folds are present; the “olfactory” organ arises from the second pair. The nuchal cartilage is elongate and rounded at the anterior end; it has a median ridge with a central groove and marginal ridges.

Arms II and III are very muscular, nearly equal in size, and 50–60% as long as the pen. The ventral arms are the same length or only slightly less than the lateral arms, but are more slender. Arms I are the smallest; they reach about 40–50% of the P.L. Arms I–III all have gelatinous aboral keels which are best developed on arms III. Arms IV have large lateral keels along their entire lengths. Well-developed protective membranes with long, slender trabeculae are present on arms I–III; they are less developed on the arms IV. The armature is in 4 longitudinal series. On arms I–III the median rows consist primarily of large hooks and the marginal rows of small suckers. The suckers arise near the distal ends of the trabeculae. At the extreme tips of the arms, the hooks are replaced by suckers. A total of 25–30 suckers and hooks occur on the proximal half of each arm I–III. Arms IV lack hooks and have 4 series of small suckers. Specimens larger than 40 mm P.L. have 30–37 suckers on the proximal half of arms IV. The arm suckers all have similar dentition. Long, pointed teeth are present on the distal margin, but decrease in size laterally. The proximal border is smooth. The total number of teeth is generally about 12–13. The suckers of the median rows on arms IV are the largest arm suckers, and the marginal suckers of arms I–III are the smallest. The marginal suckers of arms IV are intermediate in size.

The tentacles are robust and have small (approximately 20–25% of the P.L.), complex clubs. The manus possesses the 4 sucker-bearing zones typical of the genus: a ventral-marginal zone that extends the length of the manus and terminates behind the large central hook; a locking zone along the proximal half of the dorsal margin; a dorsal-marginal zone which is continuous with the dactylus distally and proximally passes medial to the locking zone; and, finally, a median zone consisting of a single row of suckers, hooks, or both. The ventral-marginal zone in its central part has 4, rarely 5, suckers that arise from each trabecula and are arranged generally in 4 longitudinal rows. The suckers in the medial row are smaller, but not less than half the diameter of the large suckers in the marginal row. Proximally, the rows converge to a single one which is continuous with the sucker row that extends along the ventral margin of the tentacular stalk. The largest suckers of the ventral marginal zone have 10–12 long, pointed teeth distally, which diminish in size laterally. The teeth are more broadly spaced than are those of the arm suckers.

The locking zone consists of 4–6 thick ridges, each with a large smooth-ringed sucker placed at its proximal end. There is usually a sucker at the distal end of the zone without the adjoining ridge. Alternating with the suckers are large rounded knobs. Proximally, this zone ends abruptly and this break is here used to indicate the proximal limit of the club.

The dorsal-marginal zone contains an irregular group of suckers that do not appear to be arranged in definite rows; distally, however, the suckers merge into 3, or occasionally 2, rows which pass lateral to the large central hook and merge with the suckers of the dactylus. Proximally, the number of suckers decreases rapidly and disappears medial to the locking zone.

The median zone bears a large central hook and a proximal row of suckers. These suckers are never transformed into hooks. Usually, there is no member of this zone distal to the large hook; however, occasionally an enlarged sucker lies behind the hook. Sometimes this sucker may bear an enlarged tooth on the distal margin of the inner ring; and, rarely, this is developed into a small, but completely formed hook. If such a hook is present, it is usually on only one club of the specimen. At the proximal end of the dactylus, suckers are irregularly arranged in 5–6 rows, but quickly decrease in number distally to form 4 regular longitudinal rows. Except for the basal few transverse rows, there is very little difference in size between members of the dorsal and ventral rows. Distally, the dactylus ends in a circle of smooth-ringed suckers at the tip of the club. The suckers from the middle of the dactylus have dentition similar to those of the manus. The total number of suckers on the dactylus (excluding the circle at the tip), the ventral marginal zone, and the dorsal marginal zone varies from 160–200. A well-developed keel is present on the dorsoaboral surface of the dactylus. A narrow, trabeculate protective membrane extends lateral to the suckers along the entire length of the ventral border of the club. On the dorsal margin, a similar membrane terminates in the proximal half of the dactylus.

The tentacular stalk bears a single series of suckers along either margin. Distally, the row along the dorsal margin consists of alternating suckers and pads with adjacent ridges that show faint resemblance to the locking apparatus of the manus; traces of the fleshy ridges accompany only the first few suckers, then disappear. The knobs are displaced medially, relative to the suckers.

The row on the ventral margin is a continuation of the ventral-margin zone on the manus. Most sucker rings in this series. have nearly smooth inner rings. The suckers that are situated one-fifth of the tentacle length from the base of the clubs are nearly smooth, but have the distal margin lightly scalloped. Both marginal rows extend almost the entire length of the tentacle. The number of suckers in the ventral row is 70–115% of the number in the dorsal row. A protective membrane, apparently lacking trabeculae, extends along the entire dorsal margin of the tentacular stalk. A trabeculate protective membrane is present distally on the ventral broder. Only a few, generally less than 10 (maximum range is 0–27), suckers are found between the rows on the oral face of the stalk.

The buccal lappets are indistinct. The buccal membrane connectives attach to the dorsal borders of arms I and II and to the ventral borders of arms III and IV.

The animal is covered with numerous reddish brown chromatophores. This species seems to have a iridescent silver sheen over the lateral surfaces of the head and arms.

Hooks begin to develop on the arms between 26–28 mm P.L. and on the tentacular club between probably 17–24 mm. A spindle-shaped liver set obliquetly to the body axis is present in the larvae.

TYPE LOCALITY.—33°19′ N, 118°45′ W, eastern North Pacific Ocean.

LOCATION OF TYPE.—University of Southern California, U.S.C. Hancock collections, AHF Cephalopod Type No. 4.
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bibliographic citation
Young, Richard E. 1972. "The systematics and areal distribution of pelagic cephalopods from the seas off Southern California." Smithsonian Contributions to Zoology. 1-159. https://doi.org/10.5479/si.00810282.97

Gonatus onyx

provided by wikipedia EN

The Gonatus Onyx is in the class Cephalopoda, in the phylum Mollusca. It is also known as the Clawed arm hook squid or Black-eyed squid. It got these names from the characteristic black eye and from its two arms with clawed hooks on the end that extend a bit further than the other arms. It is a squid in the family Gonatidae, found most commonly in the northern Pacific Ocean from Japan to California. They are one of the most abundant cephalopods off the coast of California, mostly found at deeper depths, rising during the day most likely to feed.

The mantle size of the Gonatus Onyx has been known to reach up to 18cm. G. Onyx size varies from region to region, with larger members of the species being found in warmer areas.

The type specimen was collected off the coast of California and was deposited at the Santa Barbara Museum of Natural History.[3]

Range and habitat

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. The adults and juveniles inhabit different areas, with the more solitary adults tending to like deeper water and the pack hunting juveniles preferring shallow coastal waters. They have one of the lowest seasonal variations over wide areas from the members of the family Gonatidae. The depth distribution is bimodal and follows a certain diel rhythm.[4] 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.[5] 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 from 0-500m and are more evenly spread out with most found from 0-300m.[6]

Description

The Gonatus Onyx or Black-eyed squid is a relatively smaller-sized squid with an average mantle length of about 12 cm, with some warmer water individuals reaching up to 18 cm. This species shows sexual dimorphism in mantle size with females maturing faster and growing a couple of cm larger than the males. The mantle makes up a majority of their body length, the arms make up another about 40mm on average. They have characteristic black eyes on either side of their head, these highly developed sensory organs are helpful for hunting in pitch black conditions. The armature consists of five pairs, one pair with a large primary hook at the end and multiple rows of suckers, the other four pairs are generally shorter and do not have this tentacular hook, still lined with rows of suckers. The use of clawed arms are thought to be used in hunting and for better catching and handling of their prey.[7] Some individuals are harder to identify as the tentacular club is very fragile and easily damaged. The mantle’s fins are smaller than the other members of Gonatids and the tail is less tapered. G. Onyx like most squid move using a propulsive force, using water expelled from a siphon with the combination of fin movements. The juvenile G. Onyx has been observed using ink as a defensive mechanism and as a propulsive force, while the adults rarely use ink and rather choose to use a faster propulsive force. Matured members possess chromatophores, specialized small organs under the skin of the squid, which are used to change colors to hide reflective internal organs. They have a beak, like all cephalopods; it is relatively small compared to other species. The upper part of the beak is sharp and has less curvature, while the bottom is curved, duller, and shorter. This specialized beak makes it easier for squid to attack prey larger than themselves.[7]

Reproduction and spawning

G. Onyx like most cephalopods are oviparous. Fertilization is external in squids, males use specialized arms to transfer packages of sperm, spermatophores, that are transferred to a female’s seminal receptacle, a specialized internal oviduct near the female’s mouth. Unlike other species of cephalopods, females then lay eggs in egg masses; these masses are composed of two thin membranes. The membranes form chambers holding individual eggs that are arranged in honeycomb-like patterns. Membranes are fused with each individual chamber; this is the reason the egg mass is held together in a random orientation. This egg mass is dark black and there is a thin layer of greyish black membrane over the thinner sections of egg chambers. Each individual egg inside the mass are ovoid in shape, they 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 approximately 2000 hatchlings. Each female and male can reproduce once in their lifetime as both genders die after reproduction. Female G. Onyx are relatively unique as they hold the egg mass with their clawed arms. The females lose their normal arms after fertilization from the inability to feed while holding their eggs. Females migrate to deep water (1250 m – 1750 m) once they lay their egg masses, this is a strategy to minimize the chance of encountering a predator. They can hold these egg sacks for up to nine months as they develop, going this entire time living off of built-up lipids inside the digestive gland.[6]

Early life and behavior

The hatchling’s physiology is very different from mature individuals. Hatching specimens collected were found to be moderately large at a total length of 5.0mm. The mantle length of these hatchlings ranged from 3.2mm-3.5mm and the width was 50-60% of the mantle length. Arms and tentacles are very different, there are 4 pairs of arms that are about 18-20% of the mantle size. Arm pairs 1 and 2 have suckers and sucker buds, arm pairs 3 and 4 lack suckers. There are one pair of tentacles that are proportionally larger than the arm pairs at around 40% of mantle length on average, they both contain a large number of sucker buds and the central hook is not yet visible. Hatchlings can be identified by a characteristic chromatophore pattern, with 5-6 in a single row on the aboral surface of the tentacles, a single pair on the base of the fins on the dorsal mantle, a single pair at the anterior end of the hatching gland on the mid-dorsal mantle, and 2-3 pairs on the lateral mantle. Hatchlings move with the hop-and-sink swimming style. Hatchlings mature into juveniles in about 3 months and are very active schooling predators during this time, they develop their hooks on arms and tentacles. Juveniles tend to school because they have less of a tendency to go after members of the same species when they are not fully developed. They are still relatively small with a dorsal mantle length of 30mm on average. Juveniles quickly accumulate lipids to prepare for reproduction, however, the exact reason for schooling is unknown.[8]

Adult life and behavior

Individuals older than about 3 months move to deeper waters and change their entire lifestyle. Older G. Onyx are solitary hunters and 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 the more solitary behavior. Other prey tends to be fish that are around the same size as the individual, the prey is 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.[9]

References

  1. ^ Barratt, I.; Allcock, L. (2014). "Gonatus onyx". IUCN Red List of Threatened Species. 2014: e.T162950A957015. doi:10.2305/IUCN.UK.2014-1.RLTS.T162950A957015.en. Retrieved 18 November 2021.
  2. ^ Julian Finn (2016). "Gonatus onyx Young, 1972". World Register of Marine Species. Flanders Marine Institute. Retrieved 6 March 2018.
  3. ^ Current Classification of Recent Cephalopoda
  4. ^ Watanabe, Hikaru; Kubodera, Tsunemi; Moku, Masatoshi; Kawaguchi, Kouichi (2006-06-13). "Diel vertical migration of squid in the warm core ring and cold water masses in the transition region of the western North Pacific". Marine Ecology Progress Series. 315: 187–197. doi:10.3354/meps315187. ISSN 0171-8630.
  5. ^ admin (2020-03-17). "Running the gauntlet— Deep-sea animals face multiple dangers in their daily migration". {{cite journal}}: Cite journal requires |journal= (help)
  6. ^ a b Hunt, J. C.; Seibel, B. A. (2000-04-01). "Life history of Gonatus onyx (Cephalopoda: Teuthoidea): ontogenetic changes in habitat, behavior and physiology". Marine Biology. 136 (3): 543–552. doi:10.1007/s002270050714. ISSN 1432-1793. S2CID 84763064.
  7. ^ a b Hunt, J. C.; Seibel, B. A. (2000-04-01). "Life history of Gonatus onyx (Cephalopoda: Teuthoidea): ontogenetic changes in habitat, behavior and physiology". Marine Biology. 136 (3): 543–552. doi:10.1007/s002270050714. ISSN 1432-1793. S2CID 84763064.
  8. ^ "Advances in Marine Biology", Advances in Marine Biology Volume 60, Advances in Marine Biology, vol. 60, Elsevier, 2011, pp. iii, doi:10.1016/b978-0-12-385529-9.00007-x, ISBN 9780123855299, retrieved 2022-04-22
  9. ^ Hoving, H.J.T.; Robison, B.H. (2016). "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: 94–98. doi:10.1016/j.dsr.2016.08.001. ISSN 0967-0637.

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Gonatus onyx: Brief Summary

provided by wikipedia EN

The Gonatus Onyx is in the class Cephalopoda, in the phylum Mollusca. It is also known as the Clawed arm hook squid or Black-eyed squid. It got these names from the characteristic black eye and from its two arms with clawed hooks on the end that extend a bit further than the other arms. It is a squid in the family Gonatidae, found most commonly in the northern Pacific Ocean from Japan to California. They are one of the most abundant cephalopods off the coast of California, mostly found at deeper depths, rising during the day most likely to feed.

The mantle size of the Gonatus Onyx has been known to reach up to 18cm. G. Onyx size varies from region to region, with larger members of the species being found in warmer areas.

The type specimen was collected off the coast of California and was deposited at the Santa Barbara Museum of Natural History.

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copyright
Wikipedia authors and editors
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visit source
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Habitat

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epi-bathypelagic

Reference

van der Land, J. (ed). (2008). UNESCO-IOC Register of Marine Organisms (URMO).

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Jacob van der Land [email]