Aspects of taxonomy and functional histology in terrestrial flatworms (Tricladida : Terricola)

Winsor, Leigh (1998) Aspects of taxonomy and functional histology in terrestrial flatworms (Tricladida : Terricola). Pedobiologia, 42 (5-6). pp. 412-432.

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Abstract

The taxonomy of terrestrial flatworms is presently based upon a combination of external morphological characters, and internal anatomical characters revealed by histological investigation. Uncertainties regarding the functional anatomy of Terricolan organ systems, particularly the copulatory apparatus, have hindered the exploitation of available characters for taxonomy. Considerable revision remains to be done on taxa world-wide, and provision of character-comparable taxonomic descriptions a priority. The functional histology of selected anatomical systems and their application in taxonomy are reviewed, and include epidermis, subepidermal secretions, musculature and copulatory apparatus. Secretions from the flatworm epithelium comprise at least six types, broadly grouped on the basis of histochemical staining reactions. The secretions are principally concerned with adhesive, locomotory, prey capture, repugnatorial and homeostatic functions in these soil-dwelling animals. Structure and organisation of the body-wall musculature is important in the taxonomy of the Terricola, especially at the levels of sub-family and genus. Cutaneous musculature is normally tripartite, the uncommon simple bipartite structure probably an apomorphic condition. Characters provided by the gonads and copulatory apparatus are important at the subfamily, genus and especially species level. Criteria are provided fur the recognition of eversible and protrusible types of penis. Ejaculate in Terricola is similar in composition and function to that in mammals. Spermatophores are uncommon. Functions of the atrium include resorption of unwanted sperm and yolk, and cocoon formation. The mechanisms of cocoon formation in the Tenicola differs from that described in the other Triclads. Vitelline cells appear not to participate in the development of the outer cocoon wall. The outer wall is a laminate, fibrous composite, composed of at least two scleroproteins produced by globules and strand cells in the atrium. Accessory genital organs include viscid glands which are involved in cocoon deposition, copulatory bursae which receive sperm and which may also resorb copulatory products, and adenodactyli which in some species are responsible for cocoon wall formation. Seven types of adenodactyli are recognised, and the occurrence of these organs on Australian and New Zealand caenoplanids are listed.

Item ID: 27126
Item Type: Article (Refereed Research - C1)
Keywords: Tricladida, Terricola, taxonomy, cocoon formation, musculoglandular organs, planarians
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ISSN: 1873-1511
Date Deposited: 10 Jun 2013 23:43
FoR Codes: 06 BIOLOGICAL SCIENCES > 0608 Zoology > 060808 Invertebrate Biology @ 100%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970106 Expanding Knowledge in the Biological Sciences @ 100%
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