The Ultrastructure of the Spermatozoon of Typhlonectes natans (Gymnophiona: Typhlonectidae)

Horst, Gerhard van der; Visser, John; Merwe, Liz van der

doi:10.2307/1564767

Cited by 13 publications

(7 citation statements)

References 8 publications

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“…Residues considered to comprise the receptor-binding region (A1-A3, A5, A19, A21, B22-B26) as well as those involved in dimer formation (B12, B16, B21) and hexamer formation (B6, B10, B14, B17, B20, A13, A14) [9] have been conserved between mammalian and amphiuma insulins. A recent phylogenetic study [10] comparing mitochondrial DNA sequences of the 12 S and 16 S rRNA genes has supported the conclusion of an earlier morphological investigation [11] that the gymnophonians and the urodeles are sister taxa. Amphiuma insulin, however, contains ten substitutions compared with the corresponding region of a caecilian insulin but only six substitutions compared with Xenopus insulin II (Figure 3).…”

Section: Discussionsupporting

confidence: 53%

Characterization of an insulin from the three-toed amphiuma (Amphibia: Urodela) with an N-terminally extended A-chain and high receptor-binding affinity

Conlon

Cavanaugh

Mynarcik³

et al. 1996

Biochemical Journal

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Insulin was isolated from an extract of the pancreas of a urodele, the three-toed amphiuma (Amphiuma tridactylum), and its primary structure established as Ala-Arg-Gly-Ile-Val-Glu-Gln-Cys-Cys-His10-Asn-Thr-Cys- Ser-Leu-Asn-Gln-Leu-Glu-Asn20-Tyr-Cys-Asn for the A-chain and Ile-Thr-Asn-Gln-Tyr-Leu-Cys-Gly-Ser-His10-Leu-Val-Glu-Ala- Leu-Tyr-Leu-Val-Cys-Gly20-Asp-Arg-Gly-Phe-Phe-Tyr-Ser-Pro-Lys for the B-chain. The N-terminus of the A-chain is extended by two amino acids (Ala-Arg) relative to all other known insulins suggesting an anomalous pathway of post-translational processing in the region of the C-peptide/A-chain junction of proinsulin. In common with chicken and Xenopus insulins, which contain a HisA8, amphiuma insulin was more potent (approx. 5-fold) than porcine insulin in inhibiting the binding of [125I-TyrA14]insulin to the soluble human insulin receptor from transfected 293EBNA cells (an adenovirus-transformed human kidney cell line). This result is consistent with previous data showing that insulin analogues extended at GlyA1 by uncharged groups have reduced binding affinity whereas high affinity is preserved in analogues extended by basic amino acid residues.

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Section: Discussionsupporting

confidence: 53%

Characterization of an insulin from the three-toed amphiuma (Amphibia: Urodela) with an N-terminally extended A-chain and high receptor-binding affinity

Conlon

Cavanaugh

Mynarcik³

et al. 1996

Biochemical Journal

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

“…Their spermatozoa are apomorphic in several respects. They have lost the distinct nuclear shoulders, endonuclear canal, and axial perforatorium observed in urodeles, caecilians and primitive frogs (Furieri 1975a,b;Picheral 1979;van der Horst et al 1991;Jamieson et al 1993). The lack of any fibres associated with the axoneme is also an apomorphic character state as associated fibres are present in most amphibians, sarcopterygian fish, and amniotes (see Jamieson 1999a).…”

Section: Discussionmentioning

confidence: 99%

“…The absence of any fibres associated with the axoneme in microhylids is an apomorphic condition for Amphibia. Associated fibres are present in urodeles, caecilians and most frogs (Picheral 1979;Pugin-Rios 1980;van der Horst et al 1991;Kwon and Lee 1995). Their absence from the spermatozoa of the Ranidae, Rhacophoridae, Pipidae and Microhylidae is an apomorphy shared by these families.…”

Section: mentioning

confidence: 99%

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Morphology of the spermatozoa of the Microhylidae (Anura, Amphibia)

et al. 2002

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Microhylid spermatozoa show the autapomorphic condition of possessing a thin post‐mitochondrial cytoplasmic collar. Their spermatozoa are apomorphic in several respects. They have lost the distinct nuclear shoulder, endonuclear canal and axial perforatorium observed in urodeles, caecilians and primitive frogs, possess a conical perforatorium and apomorphically lack any fibres associated with the axoneme. The spermatozoa of Cophixalus, however, differ in several respects from those of the other microhylids examined. Cophixalus spermatozoa are longer in almost all measurements, the acrosome vesicle is cylindrical and does not completely cover the putative perforatorium, the perforatorium is asymmetrical and composed of fine fibres, the nucleus is strongly attenuated and narrower, and the mitochondria are elongate. The absence of fibres associated with the axoneme is an apomorphic condition shared with the Ranidae, Rhacophoridae and Pipidae.

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Ultrastructure of the mature spermatozoa of caecilians (Amphibia: Gymnophiona)

Scheltinga

Wilkinson

Jamieson

et al. 2003

Journal of Morphology

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The spermatozoa of Gymnophiona show the following autapomorphies: 1) penetration of the distal centriole by the axial fiber; 2) presence of an acrosomal baseplate; 3) presence of an acrosome seat (flattened apical end of nucleus); and 4) absence of juxta-axonemal fibers. The wide separation of the plasma membrane bounding the undulating membrane is here also considered to be apomorphic. Three plesiomorphic spermatozoal characters are recognized that are not seen in other Amphibia but occur in basal amniotes: 1) presence of mitochondria with a delicate array of concentric cristae (concentric cristae of salamander spermatozoa differ in lacking the delicate array); 2) presence of peripheral dense fibers associated with the triplets of the distal centriole; and 3) presence of a simple annulus (a highly modified, elongate annulus is present in salamander sperm). The presence of an endonuclear canal containing a perforatorium is a plesiomorphic feature of caecilian spermatozoa that is shared with urodeles, some basal anurans, sarcopterygian fish, and some amniotes. Spermatozoal synapomorphies are identified for 1) the Uraeotyphlidae and Ichthyophiidae, and 2) the Caeciliidae and Typhlonectidae, suggesting that the members of each pair of families are more closely related to each other than to other caecilians. Although caecilian spermatozoa exhibit the clear amphibian synapomorphy of the unilateral location of the undulating membrane and its axial fiber, they have no apomorphic characters that suggest a closer relationship to either the Urodela or Anura.

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The Ultrastructure of the Spermatozoon of Typhlonectes natans (Gymnophiona: Typhlonectidae)

Cited by 13 publications

References 8 publications

Characterization of an insulin from the three-toed amphiuma (Amphibia: Urodela) with an N-terminally extended A-chain and high receptor-binding affinity

Characterization of an insulin from the three-toed amphiuma (Amphibia: Urodela) with an N-terminally extended A-chain and high receptor-binding affinity

Morphology of the spermatozoa of the Microhylidae (Anura, Amphibia)

Ultrastructure of the mature spermatozoa of caecilians (Amphibia: Gymnophiona)

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