Leech parental care - paper

Geoff Read g.read at niwa.cri.nz
Fri Jul 27 23:00:43 EST 2001


Prof. Dr. U. Kutschera wishes to alert Annelida listers to his forthcoming 
leech paper. Reprints will be available from his address (below).  

The Evolution of Parental Care in Freshwater Leeches*  

(Theory Biosci. 2001, in press)  

U. Kutschera (1) and P. Wirtz (2) 

(1) Fachbereich Biologie, Universität Kassel, Germany 

(2) Departmento de Oceanografia e Pesces, Universidade dos Açores, 
Portugal  

Address for correspondence: U. Kutschera, FB 19 Biologie, Universität 
Kassel, Heinrich-Plett-Str. 40, D-34109 Kassel, Germany, Fax: 
(0561)804-4009, e-mail: kut at hrz.uni-kassel.de   

Key words: hirudinea, life history, natural selection, parental investment  

*Dedicated to Professor Dr. G. Osche on the occasion of his 75th 
birthday.  

Summary: The life-history strategies of a selection of the most common 
European freshwater leeches (Euhirudinea) are described. On the basis 
of this information and results from the literature, the probable 
phylogenetic development of parental care in  the Euhirudinea is 
reconstructed. The jawless worm leeches (Erpobdellidae) secrete a 
protective cocoon, cement it to the substrate and sometimes ventilate it 
before they leave the egg capsules. This behaviour represents the most 
ancient state in leech evolution. Members of the jawed Hirudinidae 
deposit desiccation-resistant cocoons on land. All known Glossiphoniidae 
(leeches equipped with a proboscis) have evolved the habit of brooding 
the eggs and young. These unique parental care patterns within one 
family of extant freshwater leeches can be arranged schematically in a 
series of increasing complexity which may reflect the evolution of 
brooding behaviour. Glossiphoniid leeches of the genus Helobdella, 
which have a world-wide distribution, display the most highly developed 
parental care system: they not only protect but also feed the young they 
carry. This results in the young being much larger when they leave the 
parent and, presumably, in higher subsequent survival. Isolated cocoons 
of all aquatic leeches are rapidly destroyed by predators, primarily water 
snails. In erpobdellids (but not glossiphoniids, which protect the cocoons) 
a large portion of the cocoons are lost due to predatory attacks. We 
conclude that the major selective pressure driving the evolution of 
parental care in leeches may have been predation on eggs and juvenile 
stages.  


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