Jump to content

Macrohectopus

Add links
From Wikipedia, the free encyclopedia

Macrohectopus
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class: Malacostraca
Order: Amphipoda
Superfamily: Gammaroidea
Family: Macrohectopidae
Genus: Macrohectopus
Stebbing, 1906
Species:
M. branickii
Binomial name
Macrohectopus branickii
Lake Baikal within Eastern Siberia
Synonyms[1]

Constantia branickii Dybowsky, 1874 (Unavailable)

Macrohectopus branickii is a species of amphipod (a group containing the scuds) living in the pelagic zone of Lake Baikal, believed to be the only species of amphipod in this niche within freshwater (many more amphipods are pelagic/planktonic in the sea, such as the Hyperiids). It is the only known species within the genus Macrohectopus and the only member of the family Macrohectopidae.[a]

The sheer scale of Lake Baikal allows many species, including M. branickii, to occupy such niches which do not exist in other freshwater ecosystems. These pelagic amphipods are prey to many animals within its ecosystem, including the top aquatic predator of the lake, the Baikal seal.

Description

[edit]
See also: Amphipoda § Anatomy

Macrohectopus branickii was described by Benedykt Dybowski, who diagnosed it as possessing two pairs of antennae covered in setae, with the upper pair more robust and elongate, kidney-shaped eyes that each occupy half of the head, smooth body segments, along with keeled and spined tail segments. The laminae of the gills and brood plates are not covered, and are visible from the side.[4]

The chitinous segments are near-transparent, making the animal "clear as water";[b] which makes the muscle fibers visible without dissection.[4][5] This is likely to be a means of camouflage; Cystisoma, a marine amphipod, is similarly transparent to avoid predation.[6] Indeed, Takhteev noted that M. branickii exhibits some ecological parallels with other marine amphipods, those being the Vitjazianidae and Hyperiopsidae families.[7]

Male M. branickii are up to 6 mm (0.24 in) long, immature females are 7–14 mm (0.28–0.55 in),[8] and mature females reach up to 37 mm (1.5 in);[9] they exhibit significant sexual size dimorphism, with some considering the males to be "dwarfed".[7]

The mitochondrial genome of M. branickii was analyzed in 2021; containing 42,256 base pairs, it is the longest sequence known for amphipods and one of the largest genomes within the animal kingdom.[10]

Ecology

[edit]

Macrohectopus branickii is endemic to Lake Baikal,[1] with the "center" of its range being the deepest, central part of the lake.[11] It prefers waters colder than 4 °C (39 °F).[12]

Lake Baikal contains a great diversity of amphipod species; 40% of all known species of gammaroid amphipods live within this lake, and they have undergone significant adaptive radiation into a plethora of morphological forms. Out of all these species, M. branickii is the only pelagic member of the group;[8] molecular and morphological analysis, however, indicates that the genus originates within Micruropodidae, a family of burrowers, though Micruropus wahli is a capable swimmer and may be caught at the surface through light-fishing;[13] this attraction to light is also observed for the pelagic amphipod.[14] Phototaxis may make them vulnerable to light pollution in littoral zones close to settlements.[15]

These pelagic amphipods migrate vertically every day

The pelagic amphipod migrates throughout the lake all year round, continuing to do so in their peak breeding season.[8] This species also undergoes diel vertical migration,[16] moving to the surface at night from their daytime depth of 200–700 mm (7.9–27.6 in). The larger mature females inhabit the deeper range of this depth compared to smaller individuals.[14] During nighttime, they may be especially abundant in the water column above underwater slopes.[14] The density of amphipods is such that it creates a noticeable scattering layer when using hydroacoustic sensors, akin to the deep scattering layer in the ocean. These sensors are one method used to survey the population of these crustaceans.[17][18][19] The pelagic amphipods tend to feed more on zooplankton the larger they grow, though the exact ratios vary between individuals;[9] these prey items are consistently located above 50 m (160 ft) depth throughout the day.[17]

Trophic ecology

[edit]
Predators of this species include the Baikal seal

Macrohectopus branickii is the main species of macroplankton within the lake,[20] being an important part of the food chain; the microcrustaceans Epischura baikalensis and Cyclops kolensis feed on phytoplankton (predominantly Aulacoseira baicalensis). They then fall prey to the pelagic amphipod,[8] which in turn feed various fish such as omul (Coregonus migratorius), sculpins (Comephorus spp., Cottocomephorus spp.), and the seal, which feeds on the fish and the amphipods.[9][21] During the amphipod's diel migration, some of them may rise up too fast and become temporarily stuck on the water's surface after breaching; they must break through the surface tension to resubmerge. Before resubmerging, they are vulnerable to the water bat Myotis petax, which "trawl up" the amphipods for an easy meal.[14] On occasion they may also rise up to the surface during daytime, and seagulls are quick to take advantage of this opportunity.[14]

Its role within the lake's ecosystem has been compared to that of Antarctic krill and mysis shrimp,[17] being an important lower-level consumer due to its abundance; the density of pelagic amphipods has been estimated at tens of grams per 1 m2 (11 sq ft), with total numbers reaching several million animals and constituting 90-99% of the zooplanktonic biomass.[8] Annual biomass production of M. branickii is calculated to be around 330,000 t (360,000 tons).[14]

Notes

[edit]
  1. ^ The fossil genus Hellenis, previously considered the only other genus in the family, was removed from Macrohectopidae after a 2024 study evaluating it.[2][3]
  2. ^ Der Körper dieser schönen, zarten Thiere ist wasserhell, woher man sie beim Schwimmen nur an ihren schwarzen Augen warnehmen kann.[4]

References

[edit]
  1. ^ a b Lowry, Jim. "Amphipoda taxon details Macrohectopus branickii (Dybowsky, 1874)". WoRMS. World Register of Marine Species. Retrieved 18 May 2025.
  2. ^ Copilaş-Ciocianu, Denis; Ionesi, Viorel (2024-03-29). "New Miocene fossil taxa illuminate the evolution and paleobiogeography of the Ponto-Caspian gammaroid amphipod radiation". Contributions to Zoology: 1–21. doi:10.1163/18759866-bja10061. ISSN 1383-4517.
  3. ^ Horton, Tammy (12 April 2024). "Hellenis Petunnikov, 1914 †". WoRMS. World Register of Marine Species. Retrieved 23 May 2025.
  4. ^ a b c Dybowsky, B.N. (1874). "Beiträge zur näheren Kenntniss der in dem Baikal-See vorkommenden niederen Krebse aus der Gruppe der Gammariden". Horae Societatis Entomologicae Rossicae, Beiheft (in German). 10: 186-188. doi:10.5962/bhl.title.9945. Retrieved 18 May 2025.
  5. ^ Polina Drozdova; Alexandra Saranchina; Mariya Morgunova; Alena Kizenko; Yulia Lubyaga; Boris Baduev; Maxim Timofeyev (19 June 2020). "The level of putative carotenoid-binding proteins determines the body color in two species of endemic Lake Baikal amphipods". PeerJ. 8: e9387. doi:10.7717/peerj.9387. PMC 7307558. PMID 32596057.
  6. ^ Cronin TW (November 2016). "Camouflage: Being Invisible in the Open Ocean". Current Biology. 26 (22): R1179 – R1181. Bibcode:2016CBio...26R1179C. doi:10.1016/j.cub.2016.09.056. PMID 27875694. S2CID 25085458.
  7. ^ a b Takhteev, V. V. (2000). "Trends in the evolution of Baikal amphipods and evolutionary parallels with some marine malacostracan faunas". Advances in Ecological Research. 31: 197–220. Bibcode:2000AdER...31..197T. doi:10.1016/S0065-2504(00)31013-3. ISBN 0-12-013931-6. Retrieved 18 May 2025.
  8. ^ a b c d e Dmitry Yu. Karnaukhov; Ekaterina M. Dolinskaya; Sofya A. Biritskaya; Maria A. Teplykh; Yana K. Ermolaeva; Viktoria A. Pushnica; Iya V. Kuznetsova; Anastasia I. Okholina; Lidia B. Bukhaeva; Olga O. Rusanovskaya; Eugene A. Silow (12 April 2021). "New data regarding ecology of freshwater pelagic amphipod Macrohectopus branickii and other crustaceans of plankton from the southern part of Lake Baikal". Acta Biologica Sibirica. 7: 39–48. doi:10.3897/abs.7.e65636. Retrieved 18 May 2025.
  9. ^ a b c Koichi Yoshii; Natalia G. Melnik; Oleg A. Timoshkin; Nina A. Bondarenko; Pavel N. Anoshko; Takahito Yoshioka; Eitaro Wada (1999). "Stable isotope analyses of the pelagic food web in Lake Baikal". Limnology and Oceanography. 44 (3): 502–511. Bibcode:1999LimOc..44..502Y. doi:10.4319/lo.1999.44.3.0502. Retrieved 18 May 2025.
  10. ^ Elena V Romanova; Yurij S Bukin; Kirill V Mikhailov; Maria D Logacheva; Vladimir V Aleoshin; Dmitry Y Sherbakov (20 December 2021). "The Mitochondrial Genome of a Freshwater Pelagic Amphipod Macrohectopus branickii Is among the Longest in Metazoa". Genes (Basel). 12 (12): 2030. doi:10.3390/genes12122030. PMC 8700879. PMID 34946978.
  11. ^ Mekhanikova, I. V. (22 February 2022). "The Rare Abyssal Baikal Amphipod Polyacanthisca calceolata (Crustacea, Amphipoda) at the St. Petersburg Methane Seep, Central Baikal". Biology Bulletin. 48: 543–557. doi:10.1134/S1062359021140119. Retrieved 18 May 2025.
  12. ^ N.G. Melnik; N.A. Bondarenko; O.I. Belykh; V.V. Blinov; V.G. Ivanov; I.V. Korovyakova; T.Ya. Kostornova; M.I. Lazarev; N.F. Logacheva; G.I. Pomazkova; P.P. Sherstyankin; L.M. Sorokovikova; L.I. Tolstikova; E.P. Tereza (2006). "Distribution of pelagic invertebrates near a thermal bar in Lake Baikal". Hydrobiologia. 568(S): 69–76. Bibcode:2006HyBio.568...69M. doi:10.1007/s10750-006-0331-9.
  13. ^ Kenneth S. Macdonald III; Lev Yampolsky; J. Emmett Duffy (29 December 2004). "Molecular and morphological evolution of the amphipod radiation of Lake Baikal" (PDF). Molecular Phylogenetics and Evolution. 35 (2): 23–343. doi:10.1016/j.ympev.2005.01.013. PMID 15804407. Retrieved 18 May 2025.
  14. ^ a b c d e f S. I. Didorenko; A. D. Botvinkin; V. V. Takhteev (17 December 2021). "A New Trophic Relationship in the Baikal Ecosystem: The Pelagic Amphipod Macrohectopus branickii (Crustacea, Amphipoda) and the Bat Myotis petax (Mammalia, Chiroptera)". Biology Bulletin. 48 (7): 907–914. Bibcode:2021BioBu..48..907D. doi:10.1134/S1062359021070116. Retrieved 18 May 2025.
  15. ^ Dmitry Karnaukhov; Maria Teplykh; Еkaterina Dolinskaya; Sofya Biritskaya; Yana Ermolaeva; Viktoria Pushnica; Iya Kuznetsova; Anastasia Okholina; Lidia Bukhaeva; Еugene Silow (September 2021). "Light pollution affects the coastal zone of Lake Baikal". Limnology Review. 21 (3): 165–168. doi:10.2478/limre-2021-0015 (inactive 3 June 2025). Retrieved 18 May 2025.{{cite journal}}: CS1 maint: DOI inactive as of June 2025 (link)
  16. ^ D. Karnaukhov, S. Biritskaya, M. Teplykh, N. Silenko, E. Dolinskaya, E. Silow (October 2019). "The abundance and structure of population of pelagic amphipod Macrohectopus branickii in the coastal zone of Lake Baikal". Acta Biologica Sibirica. 5 (3): 154–158. doi:10.14258/abs.v5.i3.6574. Retrieved 18 May 2025.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  17. ^ a b c Rudstam, Lars G.; Melnik, Nataly G.; Timoshkin, Oleg A.; Hansson, Sture; Pushkin, Sergei V.; Nemov, Vladimir (1992). "Diel Dynamics of an Aggregation of Macrohectopus branickii (Dyb.) (Amphipoda, Gammaridae) in the Barguzin Bay, Lake Baikal, Russia" (PDF). Journal of Great Lakes Research. 18 (2): 286–297. Bibcode:1992JGLR...18..286R. doi:10.1016/S0380-1330(92)71296-9. ISSN 0380-1330. Retrieved 18 May 2025.
  18. ^ Makarov M.M.; Dzyuba E.V.; Zaydykov I.Yu.; Naumova E.Yu. (25 December 2024). "Hydroacoustic studies of macrozooplankton in Lake Baikal". Limnology & Freshwater Biology (6): 1491–1502. doi:10.31951/2658-3518-2024-A-6-1491. Retrieved 18 May 2025.
  19. ^ Elena Yu. Naumova; Igor Yu. Zaidykov; Mikhail M. Makarov (February 2020). "Recent quantitative values of Macrohectopus branickii (Dyb.) (amphipoda) from Lake Baikal". Journal of Great Lakes Research. 46 (1): 48–52. Bibcode:2020JGLR...46...48N. doi:10.1016/j.jglr.2019.10.002. Retrieved 18 May 2025.
  20. ^ Matveyev, A. N.; Samusenok, V. P. (22 June 2015). "The fishes and fishery in Lake Baikal". Aquatic Ecosystem Health & Management. 18 (2): 134–148. Bibcode:2015AqEHM..18..134M. doi:10.1080/14634988.2015.1028868. ISSN 1463-4988.
  21. ^ Watanabe, Yuuki Y.; Baranov, Eugene A.; Miyazaki, Nobuyuki (2020-12-08). "Ultrahigh foraging rates of Baikal seals make tiny endemic amphipods profitable in Lake Baikal". Proceedings of the National Academy of Sciences. 117 (49): 31242–31248. Bibcode:2020PNAS..11731242W. doi:10.1073/pnas.2014021117. PMC 7733859. PMID 33199633.
Retrieved from "https://en.wikipedia.org/w/index.php?title=Macrohectopus&oldid=1295269447"