Helleria brevicornis

Helleria brevicornis, the sole species of the monotypic genus Helleria, is a terrestrial woodlouse endemic to the islands and coastal regions of the northern Tyrrhenian sea.[3] H. brevicornis is of interest due to its endemism, unique ecology and basal position in the suborder Oniscidea.

Helleria brevicornis
Plate from first published description[1]
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class: Malacostraca
Superorder: Peracarida
Order: Isopoda
Suborder: Oniscidea
Family: Tylidae
Genus: Helleria
Species:
H. brevicornis
Binomial name
Helleria brevicornis
(Ebner, 1868)
Synonyms[2]
  • Syspastus brevicornis Ebner, 1868
  • Syspastus brevicornis Budde-Lund, 1879
  • Synlomogaster dasypus Costa, 1882
  • Syngastron dasypus Costa, 1883
  • Syspastus sardous Verhoeff, 1908

Description

H. brevicornis is yellow-brown in colour and grows up to 27 millimetres (1.1 in) in length. This species has vestigial antennules, short antennae and a trapezoid telson.[4] Each of its compound eyes consist of 19 ommatidia.[5] Juveniles have bumps and setae while adults are almost smooth with light spots. In adults the plates of the posterior (pleonites) fuse with each other after moulting. Like all other members of the family Tylidae, it is capable of rolling up into a perfect ball with antennas tucked in.[4]

Distribution

The species is found primarily in the oak forests of Corsica, from coastal areas up to an altitude of 1,200 metres (3,900 ft) above sea level, and on Sardinia. It is also known to occur in isolated locations on islands of the Tuscan Archipelago (Elba, Pianosa & Capraia), the Lérins Islands, the Italian coast (Monte Massoncello) the French coast (Massif de l'Estérel & Grasse region) up to an altitude of 600 metres (2,000 ft) above sea level.[4] Records of this species at Genoa and at Ospedaletti are uncorroborated.[3] A molecular phylogenetic analysis found that the colonisation of the French and Italian mainland and of the Tuscan Archipelago occurred most recently but failed to conclusively determine whether the distribution was caused by climate change during the Late Pleistocene period or through accidental human transportation of the species.[6]

Ecology

A detritivore, H. brevicornis lives amongst and feeds on the leaf litter and humus layers of forests soils and is known to dig burrows 10 centimetres (3.9 in) deep.[7] It is found living in large subsocial groups and is known to engage in conspecific coprophagy.[8] Like other peracarids, females of H. brevicornis provide developing embryos with water, oxygen and nutrients through a specialised structure known as the marsupium.[9] They are semelparous, breeding only once in their lifetime.[10] Its hindgut is host to the mesomycetozoean parasite Eccrinoides helleriae.[11]

Mate guarding

H. brevicornis has followed a unique evolutionary path among terrestrial isopods,[12][13] and is the only fully terrestrial isopod that has retained the ancestral behaviour of mate guarding[14] which has been observed in all aquatic isopods and some supralittoral species of the genus Ligia.[15] This may have been selected for[16] because these woodlice are semelparous and females lack seminal receptacles.[10] During the breeding period, a male will guard a female who is about to become sexually receptive by riding on top of and tightly gripping her. This precopulatory mate guarding begins 1 to 20 days before the parturial moult of the female. Copulation occurs within 5 to 12 hours after the female sheds the posterior part of her exoskeleton. The male continues the 'nuptial ride' after mating and stops when the female lays fertilised eggs in her newly formed marsupium.[17]

Taxonomic history

The genus Helleria and type species Helleria brevicornis were first described by Dr. Victor von Ebner, in a publication dated 8 January 1868, from a specimen collected in Corsica. He named the genus Helleria after his friend Camill Heller, who was known for his work on crustacean anatomy, and the specific epithet brevicornis after the Latin for 'short-horned' in reference to the woodlouse's short antennae.[1] Later that year, in a journal published in December, Rev. Alfred Norman described a new genus of amphipods which he also named Helleria,[18] which would eventually be renamed Guernea.[19] In 1879 Gustav Budde-Lund declared Helleria brevicornis a junior synonym to Syspastus brevicornis, a name which he popularised in his seminal 1885 catalog of terrestrial isopods.[20] Meanwhile, Achille Costa had named a woodlouse he found in Sardinia in 1882 Synlomagaster dasypus and subsequently Syngastron dasypus in 1883[21] but subsequent investigation showed it to be the same as H. brevicornis. While other authors had previously pointed out the precedence of von Ebner's publication,[22] an 1893 book by Rev. Thomas Stebbings[23] ensured subsequent authors (with the notable exception of Karl Verhoeff) used Helleria brevicornis Ebner to describe this woodlouse.

Since it was first described, some authors had placed Helleria and Tylos in the same family while others had separated them into two different families. The current taxonomy of placing the two genera in the family Tylidae has persisted since 1960 with Albert Vandel's publication of Isopodes terrestres.[4]

References
  1. Dr. Victor von Ebner (1868). "Helleria, eine neue Isopoden-Gattung aus der Familie der Oniscoiden. Mit einer Tafel. (Tab. 1)". Verhandlungen der ZoologischBotanischen Gesellschaft in Wien (in Latin and German). 18: 95–114 – via archive.org.
  2. Helmut Schmalfuss (2003). "World catalog of terrestrial isopods (Isopoda: Oniscidea) — revised and updated version" (PDF). Stuttgarter Beiträge zur Naturkunde, Serie A. 654: 341 pp.
  3. Franco, FERRARA; Stefano, TAITI (1996). "The terrestrial Isopoda of Corsica (Crustacea, Oniscidea)" (PDF). Bulletin du Muséum National d'Histoire Naturelle (in French and English). 18 (3–4) – via Bionames.
  4. Vandel, Albert (1960). Isopodes terrestres (Première partie) (PDF). Faune de France (in French). Vol. 64. Paris: Fédération Française des Sociétés de Sciences Naturelles.
  5. Grimaldi, Ilaria Maria (2003). "FILOGEOGRAFIA DI HELLERIA BREVICORNIS" [Phylogeography of Helleria brevicornis] (in Italian). Università degli Studi di Roma La Sapienza. {{cite journal}}: Cite journal requires |journal= (help)
  6. Gentile, Gabriele; Campanaro, Alessandro; Carosi, Monica; Sbordoni, Valerio; Argano, Roberto (February 2010). "Phylogeography of Helleria brevicornis Ebner 1868 (Crustacea, Oniscidea): Old and recent differentiations of an ancient lineage". Molecular Phylogenetics and Evolution. 54 (2): 640–646. doi:10.1016/j.ympev.2009.10.005. ISSN 1055-7903. PMID 19853050.
  7. Culliney, Thomas W. (2013-09-25). "Role of Arthropods in Maintaining Soil Fertility". Agriculture. 3 (4): 629–659. doi:10.3390/agriculture3040629.
  8. Mead, Françoise; Gabouriaut, Danielle (July 1988). "Belated and Decreased Reproduction in Isolated Females of Helleria brevicornis Ebner (Crustacea, Oniscoïdea). Recuperation After the Addition of Faeces to the Female Environment". International Journal of Invertebrate Reproduction and Development. 14 (1): 95–104. doi:10.1080/01688170.1988.10510368. ISSN 0168-8170.
  9. Warburg, M.R. (1993). "The Reproductive System and Reproduction". Evolutionary Biology of Land Isopods. Springer. p. 85. doi:10.1007/978-3-662-21889-1. ISBN 978-3-662-21891-4. S2CID 42882939.
  10. Longo, Guglielmo; Trovato, M; Mazzei, Veronica (2011-09-01). "Variability of the female genital system morphology and of sperm storage in terrestrial isopods (Isopoda, Oniscidea)". Italian Journal of Zoology. 78 (3): 287–297. doi:10.1080/11250003.2010.544333.
  11. Lichtwardt, Robert W. (1986). "Appendices" (PDF). The Trichomycetes Fungal Associates of Arthropods. Springer-Verlag. pp. 225, 295, 302. doi:10.1007/978-1-4612-4890-3. ISBN 978-1-4612-9348-4. S2CID 45382056.
  12. Hurtado, Luis A.; Lee, Eun J.; Mateos, Mariana; Taiti, Stefano (2014-04-15). "Global Diversification at the Harsh Sea-Land Interface: Mitochondrial Phylogeny of the Supralittoral Isopod Genus Tylos (Tylidae, Oniscidea)". PLOS ONE. 9 (4): e94081. Bibcode:2014PLoSO...994081H. doi:10.1371/journal.pone.0094081. ISSN 1932-6203. PMC 3988090. PMID 24736501.
  13. Michel-Salzat, Alice; Bouchon, Didier (September 2000). "Phylogenetic analysis of mitochondrial LSU rRNA in oniscids". Comptes Rendus de l'Académie des Sciences, Série III. 323 (9): 827–837. doi:10.1016/s0764-4469(00)01221-x. ISSN 0764-4469. PMID 11072627.
  14. Santhanakumar, J.; Mohanraju, R.; Kirubagaran, R.; Subramoniam, T. (2014-01-08). "Mate guarding behaviour in the supralittoral isopod,Ligia dentipes(Oniscidea) from the Andaman and Nicobar Islands". Invertebrate Reproduction & Development. 58 (2): 128–137. doi:10.1080/07924259.2013.870935. ISSN 0792-4259. S2CID 84949037.
  15. Jormalainen, Veijo (2007-08-01). "Mating Strategies in Isopods". In Duffy, J.E.; Thiel, M. (eds.). Evolutionary Ecology of Social and Sexual Systems. Oxford University Press. pp. 167–190. doi:10.1093/acprof:oso/9780195179927.001.0001. ISBN 9780195179927.
  16. Zimmer, Martin (October 2001). "Why do male terrestrial isopods (Isopoda: Oniscidea) not guard females?". Animal Behaviour. 62 (4): 815–821. doi:10.1006/anbe.2001.1845. ISSN 0003-3472. S2CID 53175429.
  17. Mead, Françoise; Gabouriaut, Danielle (1977-01-01). "Chevauchée Nuptiale Et Accouplement Chez L'Isopode Terrestre Helleria Brevicornis Ebner (Tylidae). Analyse Des Facteurs Qui Contrôlent Ces Deux Phases Du Comportement Sexuel". Behaviour (in French and English). 63 (3): 262–279. doi:10.1163/156853977X00441. ISSN 1568-539X.
  18. Norman, Alfred Merle (December 1868). "LII.—On Crustacea Amphipoda new to Science or to Britain". Annals and Magazine of Natural History. 4. 2 (12): 418–419. doi:10.1080/00222936808695843. ISSN 0374-5481 – via BHL.
  19. Horton; et al. (2018). "Guernea (Guernea)". World Amphipoda Database. Retrieved 2018-08-01 – via WoRMS.
  20. Budde-Lund, Gustav (1885). Crustacea Isopoda Terrestria per Familias et Genera et Species (in Latin). Copenhagen: Hauniae, Sumtibus Auctoris. pp. 280–281. doi:10.5962/bhl.title.109769. OCLC 1042907183 – via archive.org.
  21. Costa, prof. A. (1883). "Diagnosi dì nuovi Artropodi trovati in Sardegna". Bollettino della Società Entomologica Italiana (in Italian). 15: 332–341 – via archive.com.
  22. Eaton, Rev. A. E. (15 November 1882). "LIII.—Note on Platyarthrus Hoffmanseggii, Brandt, and Helleria brevicornis, Ebner, Terrestrial Isopoda". Annals and Magazine of Natural History. 5. 10 (60): 458. doi:10.1080/00222938209459750. ISSN 0374-5481 – via BHL.
  23. Thomas Roscoe Rede Stebbing (1893). "XXVII Woodlice and other terrestrial Isopods". A History of Crustacea: Recent Malacostraca. London: Kegan Paul, Trench, Trübner & Co. p. 425 – via archive.org.
  • Data related to Helleria brevicornis at Wikispecies
  • Image gallery of H. brevicornis at Trilobite.ch; key image(s): photo of underside.
  • Image gallery of H. brevicornis at insecte.org (in French); key image(s): macro photo of juvenile.
  • Macro photos of H. brevicornis on MyrmecoFourmis.fr (in French); key image(s): photos of conglobation.
  • Image gallery of H. brevicornis at fansite (in French); key image(s): photos of fused pleonites & trapezoid telson and mancae emerging from marsupium.
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