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Rhinogobiops

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Rhinogobiops
Temporal range:Plioceneto present
Scientific classificationEdit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Gobiiformes
Family: Gobiidae
Subfamily: Gobiinae
Genus: Rhinogobiops
C. L. Hubbs,1926
Species:
R. nicholsii
Binomial name
Rhinogobiops nicholsii
(T. H. Bean,1882)
distribution
Synonyms
  • Gobius nicholsiiT. H. Bean, 1882
  • Coryphopterus nicholsii(T. H. Bean, 1882)

Rhinogobiopsis a genus oftrue gobiesin the familyGobiidae.It ismonotypic,being represented by the single species,Rhinogobiops nicholsii,also known as theblackeye goby,bluespot goby,andcrested goby.[1]They are common inhabitants ofcoral reefsand rocky habitats along the eastern Pacific Ocean coasts of Mexico, the United States, and Canada, although they are hardly noticed, as they often rest motionless near their shelters.

Blackeye gobies range in color from creamy white to a mottled dark purple-brown, but can easily be recognized by the distinctive black spot on their first dorsal fins and an iridescent blue spot beneath their eyes. They are capable of rapidly changing their color in response to social situations or threats. They are alsoprotogynoushermaphrodites,starting out in life as females. They are highly territorial and each male usually maintains aharemof two to eight females.

Taxonomy

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The blackeye goby is the only species recognised in thegenusRhinogobiops.It is a true goby, being classified in thesubfamilyGobiinae,[2]

The species was first described in 1882 by the AmericanichthyologistTarleton Hoffman Beanfrom a specimen fromDeparture Bay,British Columbia,recovered in 1881 by the American survey vesselHassler.He named itGobius nicholsii,afterHenry E. Nichols,the collector of the specimen and the captain of the ship.[1][3]

It was transferred to the genusRhinogobiusin 1907 byEdwin Chapin StarksandEarl Leonard Morris.In 1926, American ichthyologistCarl Leavitt Hubbsmoved it to its own genus,Rhinogobiops.The name comes fromGreek,meaning "resemblingGobius".[4]

In 1960,James E. BöhlkeandC. Richard RobinssynonymizedRhinogobiopswith the genusCoryphopterus,though they noted that it differed from other members of the latter in the number offin raysandscalesand should be treated as asubgenus.[5]In 1995, John E. Randall expressed doubts as to the validity of this move. He was supported by ichthyologists Ray S. Birdsong and even Robins himself in believing thatRhinogobiopsis in fact distinct fromCoryphopterus.[6]

This was confirmed in 2002 in a phylogenetic study on the genusCoryphopterusby Christine E. Thacker and Kathleen S. Cole. They concluded that blackeye gobies were more closely related to acladecontainingLophogobius cyprinoidesthan to the rest of the genus. They transferred it back to the genusRhinogobiopsand it is nowvalidasRhinogobiops nicholsii.[7]

Fossil record

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Abundantotolithfossilsof blackeye gobies from thePlioceneepoch(5.3 to 3.6 million years ago) have been found inLomitaMarl.Pleistocenefossils of the species have also been recovered from otherfossil localitiesin California.[8]

Description

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Blackeye gobies can easily be identified by the fleshy crest on the upper surface of their heads, the distinctive black upper anterior edge of the firstdorsal fin,their large scales, and large, dark eyes.[9][10]They are small fish, reaching a maximum length of only 15 cm (6 in).[1][11]

A blackeye goby with the iridescent blue spot below the eye clearly visible

The body is elongated, slightly compressed, and almost completely covered by scales. The head lacks scales and is wider than it is deep, with a small terminal mouth and a projecting lower jaw. Themaxilladoes not extend below the anterior margin of the eye. The teeth are conical and are present in double rows on both jaws. The eyes are directed slightly upwards and sideways.[8]

Thedorsal finsare close together, with the first dorsal fin having five to seven rays and the second having 12 to 15. Thepectoral finshave 21 to 24 rays, all of which are rigid. Theanal finhas 11 to 14 rays with no spines.[8]It is about the same size as the second dorsal fin.[12]Thecaudal finis rounded with about 17 rays, 12 of which are segmented and branched. Thepelvic finsare completely fused with each other, forming a disk, each with four rays. These function as suckers.[8]

Coloration can vary, as blackeye gobies are capable of rapidly changing color during social interactions and forcamouflage.The basic body color is creamy white to pale tan, but can become a mottled dark purple-brown. The body is irregularly speckled with metallic blue-green. Below the eye is an iridescent bluish spot clearly visible if illuminated (the source of their other common name – bluespot goby). The first dorsal fin has a distinctive black upper anterior edge that is retained even when the fish changes color. During breeding season, the pelvic fins of the males (normally gray in both sexes) turn jet black.[8][13]

Distribution and habitat

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Blackeye gobies are found in the eastern North Pacific, along the coasts of Canada, the United States, and Mexico.[14]It reaches as far north asSt. John Baptist Bay(nearPartofshikof Island) inAlaskato as far south asSan Martin IslandofBaja California,Mexico.[1][9]Its range does not extend into theGulf of California,however.[15]

Its northern range was previously believed to have reached only as far asSkidegate Channelin theHaida GwaiiArchipelago and the waters aroundWales Island,both inBritish Columbia.[1]However, a 2000 survey recovered blackeye gobies fromSitkaandKlawockin southeasternAlaska.This makes the blackeye goby the only known species of goby to be found in Alaskan waters, though the arrow goby (Clevelandia ios) and the bay goby (Lepidogobius lepidus) have also been recovered from northern British Columbia. Subsequent observations on the recovered specimens inaquarianoted that blackeye gobies could only survive in temperatures exceeding 4 °C (39 °F), making them unlikely to be found further north than St. John Baptist Bay.[9]

Blackeye gobies are extremely abundant.[13]They are exclusivelymarineand usually inhabit rocks and reefs fromintertidalareas to depths of 60 m (200 ft) from the surface, though they have been found in depths as much as 106 m (348 ft).[10][8]They are most commonly found in the border area between reefs and sand bottoms. They usually seek out natural crevices and holes in the rock and reef surfaces but are capable of digging their own burrows in softer substrates if needed.[16]They are difficult to see due to their habit of resting completely still until approached closely.[13][17]When threatened they dart quickly back to their shelters.[13]

Ecology and behaviour

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Blackeye gobies are highly territorial. Each male usually guards aharemof two to eight females and a small territory around a shelter. They arediurnaland mostly prey on smallcrustaceansandmollusks.They areprotogynous hermaphrodites,with all individuals being born females and turning into males once they reach a certain size under the correct conditions. They exhibitcourtship displayand breed between April and October. Thelarvaearepelagic.

Social behavior

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A blackeye goby showing coloration typical of a subordinate individual

Male blackeye gobies form harem with both females and juveniles. The males in such groups are usually larger than the female members, typically 9 to 11 cm (3.5 to 4.3 in) in length, while the females range in size from 3.2 to 8.1 cm (1.3 to 3.2 in).[18]

Males are highly territorial and actively defend nest sites and females from intruders.[18]Their territories can range from as small as 0.01 m2(16 sq in) to as large as 1.18 m2(12.7 sq ft). Larger males defend larger territories. During breeding season, the size of the territorial range can decrease even further as males concentrate on closely guarding the nests instead of foraging.[19]

Due to the relative closeness of the territories, males often encounter each other. When two males meet, they approach each other, slowly undulating their bodies, and assume combat-threatdisplaywith all fins stiffly outstretched. Once directly face-to-face, they gape their mouths and expand their throats. They take turns doing this until the "loser" assumes a mottled darker coloration and retreats to his shelter. From then on, the established dominant fish may harass the subordinate fish by chasing or nipping him if he strays too close.[8]

Reproduction and life history

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Blackeye gobies aresexually dimorphic,with different sexes distinguishable fromgenital papilla,size, and length ofdorsalandanal fins.Females attainsexual maturityat 4.73 to 7.35 cm (1.86 to 2.89 in) in length, while males mature at 7.21 to 8.3 cm (2.84 to 3.27 in) in length.[8]The breeding season lasts for five to seven months, between April and October.[10]During this, the fused pelvic fins (the disk) of the males turn very dark in color.[20]

They exhibit interesting courtship behavior. Males first prepare a nesting site by fanning, rubbing, scooping, and nibbling a selected area.[10][11]They then entice females into the nesting site by swimming up for 2 ft (0.61 m) or more with mouths open and fins outstretched then back down again.[13][21]After doing this once or several times, they resume cleaning the nest site. At times, the males may also rush towards the females. Uninterested females often swim away to a shelter, in which case the males give chase, often nipping her fins. Interested females directly approach the males and slowly undulate their bodies while opening their mouths widely and spreading their fins.[8]

The femalesspawna single layer of around 1700 eggs on the bottom surface of the nest,[10]and may spawn several times. The males follow the females around as they lay the eggs, constantly nipping and bumping them. The males then fertilize the eggs during or immediately after they have been laid.[8]The eggs are spindle-shaped and attached directly to rock surfaces. They are a pinkish to orange color when freshly laid but darken as they mature. The males defend the eggs until they hatch (after 10 to 33 days).[8][22]

The newly hatchedplanktoniclarvaeare 3 mm (0.12 in) in length and grow rapidly. They arepelagic,and can be found more than 104.6 km (65.0 mi) from the shore at depths of several thousands of feet.[10]They differ from adults in having dark-orange vertical bands.[8]They mature after their first winter.[10]

The longest known lifespan in an individual is five years.[23]

Protogynous hermaphroditism

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Blackeye gobies are protogynous hermaphrodites – all of them are born females but can shift once to become males once they reach a length of 2 to 3 in (5.1 to 7.6 cm).[8][21][24][25]This is likely to be the result of the limited availability of good nesting sites. Larger males have a competitive advantage in defending these nesting sites, thus larger males and smaller females have much higher reproductive success rates than small males.[21][26]A change in sex ratio and size distribution can cause of females to undergo the change to become males.[22]

Sex change in blackeye gobies has been correlated with thesteroids17β-estradiol and 11-ketotestosterone. A decrease in the former and an increase in the latter induces females to change to males. This has been artificially replicated in laboratory conditions with the application of 11-ketotestosterone, 11-ketoadrenosterone, andfadrozole(an aromatase inhibitor) on females.[27]The change from female to male takes about four weeks in captive individuals, but the length of time it takes in the wild is unknown.[22]

Diet and predators

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Blackeye gobies arediurnal,being primarily active during daytime.[28]They feed almost exclusively on small crustaceans and mollusks. The most common prey includeamphipods,copepods,isopods,decapods(particularlyhermit crabs),snails,andclams.Other less important prey includeannelidsand otherinvertebrates.Parts ofechinoderms(mostlysea urchins) andbryozoansare also found in the contents of the stomachs of blackeye gobies, though this is likely the result of incidental ingestion rather than true predation. The preferred prey can vary by season depending on their abundance.[8]Blackeye gobies have also been observed feeding directly onchemosyntheticbacterial mats.It is of particular significance if substantiated, as it would be the first known instance of a fish deriving nutrition directly from chemosynthetic bacteria.[29]Blackeye gobies feed mostly by simply picking off the prey directly from the substrate. Occasionally, they may feed by taking a mouthful of substrate, spitting it out, then picking off edible prey as it drifts to the bottom.[8]

Blackeye gobies are heavily preyed upon, in turn, bybass(such askelp bassandbarred sand bass),rock cod,greenling,and other predatory fishes of their rock and reef habitats, as well as birds such asBrandt's cormorantsanddouble-crested cormorants.[10][17][22][25]Sea urchins of the genusStrongylocentrotusare also known to dislodge blackeye gobies from their territories, possibly as a result of egg predation by the former.[30]

Parasitesof blackeye gobies include thetrematodesPronoprymna petrowiandLecithaster gibbosus.[31]

In aquaculture

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Blackeye gobies adapt well toaquariaand are often caught alive for such purposes.[10]However, they can be troublesome if kept with other males and other species of fish, as they are extremely territorial and aggressive.[8][32]

References

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  1. ^abcdeW.I. Follett (1970)."Benthic fishes cast ashore by giant waves near Point Joe, Monterey County, California".Proceedings of the California Academy of Sciences.Fourth Series.37(15): 473–488.
  2. ^Nicolas Bailly (2010)."Rhinogobiops nicholsii(Bean, 1882) ".World Register of Marine Species.RetrievedJanuary 9,2012.
  3. ^Tarleton Hoffman Bean (1882)."Notes on a collection of fishes made by Captain Henry E. Nichols, U.S.N., in British Columbia and southern Alaska, with descriptions of new species and a new genus (Delolepis) "(PDF).Proceedings of the United States National Museum.4(255): 463–474.doi:10.5479/si.00963801.4-255.463.Archived fromthe original(PDF)on 2014-05-17.
  4. ^Carl L. Hubbs (1926)."Notes on the gobioid fishes of California, with descriptions of two new genera"(PDF).Occasional Papers of the Museum of Zoology, University of Michigan(169). University of Michigan: 1–7.
  5. ^James E. Böhlke & C. Richard Robins (1960). "A revision of the gobioid fish genusCoryphopterus".Proceedings of the Academy of Natural Sciences of Philadelphia.112:103–128.
  6. ^John E. Randall (1995)."FusigobiusWhitley, a junior synonym of the gobiid fish genusCoryphopterusGill "(PDF).Bulletin of Marine Science.56(3): 795–798.
  7. ^Christine E. Thacker & Kathleen S. Cole (2002)."Phylogeny and evolution of the gobiid genusCoryphopterus"(PDF).Bulletin of Marine Science.70(3): 837–850.
  8. ^abcdefghijklmnopJ.W. Wiley (1973)."Life history of the western North American gobyCoryphopterus nicholsii(Bean) ".Transactions of the San Diego Society of Natural History.17:187–208.doi:10.5962/bhl.part.19964.
  9. ^abcDavid J. Csepp & Bruce L. Wing (1999)."Northern range extensions and habitat observations for blackeye gobiesRhinogobiops nicholsiiand Kelp PerchBrachyistius frenatusin southeastern Alaska "(PDF).Alaska Fishery Research Bulletin.6(2): 78–84.
  10. ^abcdefghiJohn E. Fitch & Robert J. Lavenberg (1975).Tidepool and Nearshore Fishes of California.California Natural History Guides: Volume 38. University of California Press. pp.66–67.ISBN978-0-520-02845-6.blackeye goby.
  11. ^abDaniel W. Gotshall (2011).Pacific Coast Inshore Fishes, 5th Edition (Revised).Shoreline Press. p. 101.ISBN978-1-885375-27-8.
  12. ^Ronald A.Fritzsche & J. William Cavanagh (2007).A Guide to the Fishes of Humboldt Bay(PDF).Department of Fisheries, Humboldt State University. p. 103.
  13. ^abcde"Blackeye goby,Coryphopterus nicholsii(Bean) ".Calisphere, California Digital Library, University of California. 2011.RetrievedJanuary 12,2012.
  14. ^"Rhinogobiops nicholsii(Bean 1882) ".Fish Wise. 2007.RetrievedJanuary 10,2012.
  15. ^Donald A. Thomson; Lloyd T. Findley & Alex N. Kerstitch (2000).Reef Fishes of the Sea of Cortez: The Rocky-Shore Fishes of the Gulf of California.University of Texas Press. p. 246.ISBN978-0-292-78155-9.
  16. ^Randi Parent (2008)."Celebrate Earth Weekend at the Santa Monica Pier Aquarium April 26–27"(PDF).Sea Stars.18(3). Heal the Bay, Santa Monica Pier Aquarium: 4.
  17. ^abMark A. Steele & Todd W. Anderson (2006). "Predation". In Larry Glenn Allen; Daniel J. Pondella & Michael H. Horn (eds.).Ecology of Marine Fishes: California and Adjacent Waters(PDF).University of California Press. p. 443.ISBN978-0-520-24653-9.
  18. ^abTerril Efird & Martin Duffy.Social Dynamics of the Blackeye Goby,Rhinogobiops nicholsii.
  19. ^Christopher G. Lowe & Richard N. Bray (2006)."Movement and Activity Patterns".In Larry Glenn Allen; Daniel J. Pondella & Michael H. Horn (eds.).Ecology of Marine Fishes: California and Adjacent Waters.University of California Press. p. 531.ISBN978-0-520-24653-9.
  20. ^Roger Tory Peterson; Earl S. Herald & William N. Eschmeyer (1999).A Field Guide to Pacific Coast Fishes: North America.Houghton Mifflin Harcourt. pp. 160, 261.ISBN978-0-520-24653-9.
  21. ^abcBill Bushing. (2008)."Dive Dry with Dr. Bill: The Sex Life of Gobies".Starthrower Educational Multimedia.RetrievedJanuary 12,2012.
  22. ^abcdFrederieke Janet Kroon (1991).Protogynous hermaphroditism in a temperate reef fish, the blackeye goby,Coryphopterus nicholsii(Pisces: Gobiidae)(PDF).Sea Stars(Ph.D thesis). Vol. 18. The University of British Columbia.
  23. ^Rainer Froese & Susan M. Luna."Rhinogobiops nicholsii(Bean, 1882) ".FishBase.RetrievedJanuary 12,2012.
  24. ^Mark A. Steele & Graham E. Forrester (2002)."Variation in the relative importance of sublethal effects of predators and competitors on growth of a temperate reef fish".Marine Ecology Progress Series.237:233–245.Bibcode:2002MEPS..237..233S.doi:10.3354/meps237233.hdl:10211.3/201957.
  25. ^abTom Haight (1999)."Blackeyed Goby (Coryphopterus nicholsi) ".Doheny State Beach Interpretive Association. Archived fromthe originalon May 18, 2011.RetrievedJanuary 12,2012.
  26. ^Kathleen S. Cole (2010).Reproduction and Sexuality in Marine Fishes: Patterns and Processes.California Natural History Guides: Volume 38. University of California Press. p. 151.ISBN978-0-520-26433-5.
  27. ^L. Kokokiris; A Fostier; F. Athanassopoulou; D. Petridis & M. Kentouri (2006). "Gonadal changes and blood sex steroids levels during natural sex inversion in the protogynous Mediterranean red porgy,Pagrus pagrus(Teleostei: Sparidae) ".General and Comparative Endocrinology.149(1): 42–48.doi:10.1016/j.ygcen.2006.05.002.PMID16806215.
  28. ^Miranda Watts (2004).The Role of Fluorescence in Feeding and Prey Attraction in the HydromedusaOlindias formosa(PDF).MBARI.
  29. ^Markes E. Johnson & Jorge Ledesma-Vázquez (2009).Atlas of Coastal Ecosystems in the Western Gulf of California: Tracking Limestone Deposits on the Margin of a Young Sea.University of Arizona Press. p. 151.ISBN978-0-8165-2530-0.
  30. ^Mark A. Hixon (2006)."Competition".In Larry Glenn Allen; Daniel J. Pondella; Michael H. Horn (eds.).Ecology of Marine Fishes: California and Adjacent Waters.University of California Press. p. 455.ISBN978-0-520-24653-9.
  31. ^David I. Gibson (1984)."Trematoda".In L. Margolis; Z Kabata (eds.).Guide to the Parasites of Fishes of Canada, Part IV.NRC Research Press. p. 333.ISBN978-0-660-16403-8.
  32. ^David Wrobel.The Temperate Reef Tank – Part Two(PDF).FishChannel.com.
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