Protamines in the internally fertilizing neobatrachian frog Eleutherodactylus coqui.
The internally fertilizing primitive frog Ascaphus truei (family Ascaphidae) from the Pacific Northwest is the only frog with an intromittent organ. The more advanced neobatrachian frog Eleutherodactylus coqui (family Leptodactylidae) from Puerto Rico has secondarily acquired internal fertilization but mates by cloacal apposition. Nonetheless, both frogs have introsperm with an elongated head containing highly condensed chromatin. Characterization of sperm nuclear basic proteins (SNBPs) in E. coqui by acid-urea polyacrylamide gel electrophoresis indicates that, as in A. truei, testes from a single animal contain several protamines. Amino acid analysis indicates a composition for the most rapidly moving protamine of each species as follows: in E. coqui, ARG (35.6 mol %) + LYS (3.8 mol %) + HIS (7.6 mol %) = 47 mol % total basic residues and in A. truei, ARG (42.1 mol %) + LYS (11.1 mol %) = 53.2 mol % total basic residues. Transmission electron microscopy shows that E. coqui introsperm, like those in A. truei, are elongate with highly condensed chromatin. However, E. coqui introsperm lacks an axial perforatorium that extends into an endonuclear canal. These morphological features are plesiomorphic (primitive) and shared by A. truei with urodeles and basal amniotes (Jamieson et al. (1993) Herpetologica 49:52-65). In E. coqui introsperm, the nucleoprotein complex has a cross-sectional axis of 420 + 20 angstroms and shows a knobby chromatin structural organization in TEM. The presence of arginine-enriched protamines in both a basal anuran like the ascaphid A. truei and a more advanced neobatrachian like the leptodactylid E. coqui supports the hypothesis that internal fertilization acts as a constraint on the range of SNBP diversity in animals.
Kasinsky
Harold E
HE
Department of Zoology, University of British Columbia, 6270 University Blvd., Vancouver, B.C., Canada, V6T 1Z4. kasinsky@zoology.ubc.ca
Frehlick
Lindsay J
LJ
Su
Hua Wei Harvey
HW
Ausio
Juan
J
D000596:Amino Acids / Q000302:isolation & purification; D000818:Animals; D001001:Anura / Q000378:metabolism*; D002843:Chromatin / Q000378:metabolism / Q000648:ultrastructure; D004591:Electrophoresis, Polyacrylamide Gel; D008297:Male; D046529:Microscopy, Electron, Transmission; D010802:Phylogeny; D011479:Protamines / Q000302:isolation & purification*; D011647:Puerto Rico; D012098:Reproduction / Q000502:physiology*; D013045:Species Specificity; D013094:Spermatozoa / Q000378:metabolism* / Q000648:ultrastructure
D000596:Amino Acids; D002843:Chromatin; D011479:Protamines