单词 | pleon |
释义 | pleonn.1 Zoology. The posterior division of the body of a crustacean; the crustacean abdomen. †Formerly also: spec. (Owen's term for) the tail-spine or telson of a horseshoe crab, considered as representing the abdomen (obsolete). Cf. pereion n. ΘΚΠ the world > animals > invertebrates > phylum Arthropoda > class Crustacea > [noun] > member of > parts of > abdomen pleon1856 the world > animals > invertebrates > phylum Arthropoda > order Xiphosura or Merostomata > [noun] > genus Limulus > member of > parts of > telson pleon1856 1856 C. Spence Bate in Rep. Brit. Assoc. 1855 27 Abdominal segments (or pleon). [Note] From πλέω, navigo: pleon, part which supports the swimming legs. 1873 R. Owen Anat. King Crab 9 The tail-spine (‘pleon’ and ‘telson’..) nearly equals in length the two antecedent divisions. 1888 Challenger Rep. XXIX. i. 652 The feeble structure of the mouth-organs and of the after-part of the pleon. 1940 Amer. Midland Naturalist 23 206 The last three pleon segments are completely fused and the sutures are not visible. 1965 B. E. Freeman tr. A. Vandel Biospeleol. ix. 123 The representatives of this group show both primitive structures and highly specialised characters, especially with regard to the pleon and the pleopods. 1995 P. J. Hayward et al. in P. J. Hayward & J. S. Ryland Handbk. Marine Fauna N.W. Europe viii. 317/2 The malacostracan body plan..comprises a primitive, five-segmented head, often fused with the thorax, or pereon, of eight segments; the abdomen, or pleon, consists of a further six segments, or rarely seven. Derivatives ˈpleonal adj. ΘΚΠ the world > animals > invertebrates > phylum Arthropoda > order Xiphosura or Merostomata > [adjective] > telson of king-crab pleonal1873 pleonic1873 1873 R. Owen Anat. King Crab 48 Pleonal nerve, or continuation of neural cord. 1985 Proc. Biol. Soc. Washington 98 682 The pleonal and uropodal structure of the male. 2003 Arthropod Struct. & Developm. 32 337 In these species, the heart extends from the border between the fifth and sixth thoracic segments to the fifth pleonal segment. pleˈonic adj. ΘΚΠ the world > animals > invertebrates > phylum Arthropoda > order Xiphosura or Merostomata > [adjective] > telson of king-crab pleonal1873 pleonic1873 1873 R. Owen Anat. King Crab 26 The posterior or ‘pleonic’ artery..has more definite tunics and holds a longer course. 1942 Amer. Naturalist 76 421 There are rudiments of pleonic pleural angles, and there is a small subrectangular antennal angle on the carapace. 1995 Biol. Bull. 188 157 The seventh segment anlage is thus a recapitulation of the seventh pleonic segment. This entry has been updated (OED Third Edition, September 2006; most recently modified version published online March 2022). † pleonn.2 Biochemistry. Obsolete. A hypothetical aggregate of molecules which cannot be increased or decreased in size without changing its chemical nature. ΘΚΠ the world > matter > chemistry > atomic chemistry > [noun] > molecules > molecular aggregates pleon1882 multimer1959 1882 S. H. Vines in tr. F. G. J. von Sachs Text-bk. Bot. (ed. 2) 664 (note) It will be noted that the Atom, Molecule, and Pleon are chemical ideas, whereas the Micella and Micellar Aggregate are purely physical. 1885 G. L. Goodale in A. Gray & G. L. Goodale Bot. Text-bk. (ed. 6) II. ii. vi. 212 The terminology now proposed by Nägeli applies the word pleon to those aggregates of molecules which cannot be increased or diminished without changing their chemical nature. This entry has been updated (OED Third Edition, September 2006; most recently modified version published online March 2020). < |
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