Staging of middle and late embryonic development in the medicinal leech Hirudo medicinalis
Research article published in Journal of comparative neurology (1998)
Abstract
We present a description of the last half of embryonic development in the European medicinal leech, Hirudo medicinalis, based entirely on externally visible morphological features, and establish reliably observable stages during that development. Embryogenesis, from the time fertilized eggs are deposited in an eggcase (called a cocoon) to the emergence of juveniles from the cocoon, takes approximately 4 weeks at room temperature. The stages described in this paper extend from the completion of segmentation to the appearance of the final bands of pigmentation. Developmental stages are expressed as percentages of total embryonic developmental time. This staging table was constructed for embryos kept at 20 degrees C. In addition, the development of animals kept at 17 degrees C or at 24 degrees C was compared with those held at 20 degrees C. Development proceeds more quickly at higher temperatures. Because development in embryos held at higher or lower temperatures was linearly related to the stages determined for embryos held at 20 degrees C, the rate of development at any intermediate temperature can be predicted from the staging table at 20 degrees C by simple multiplication.
Abstract sourced from PubMed (NCBI) for the cited record. See the original publication for the authoritative version.
Summary
Staging of middle and late embryonic development in the medicinal leech Hirudo medicinalis.
Why This Matters for Hirudotherapy
This study presents a staging table for the middle and late embryonic development of the European medicinal leech, Hirudo medicinalis, based entirely on externally visible morphological features extending from the completion of segmentation to the appearance of final pigmentation bands. Embryogenesis took approximately four weeks at room temperature, and the authors demonstrated that development proceeds more quickly at higher temperatures, with stages at 17°C or 24°C linearly related to those at 20°C, allowing prediction of developmental rate at intermediate temperatures. The study concerns Hirudo medicinalis, a species used in hirudotherapy, so it has some general biological relevance. However, it is purely descriptive embryology and provides no information on therapeutic efficacy, the salivary secretome, or clinical application.
Citation
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