The distribution of neuroactive substances within the cercaria ofSanguinicola inermis

Abstract

The serotoninergic and peptidergic components of the nervous system of the cercaria of Sanguinicola inermis (Digenea: Sanguinicolidae) were examined using whole-mount immunocytochemistry and a plan of the nervous system has been described. Antibodies to serotonin (5-hydroxytryptamine, 5-HT) and the neuropeptides, FMRFamide, GFNSALMFamide (S1) and SGPYSFNSGLTFamide (S2) were used in the study. Immunoreactivity (IR) was demonstrated to all but the S2 antisera and showed a similar fundamental distribution. IR was found in paired cerebral ganglia located anteriorly within the body and connected by a cerebral commissure. From the ganglia paired ventral and dorsal longitudinal nerve cords extend anteriorly into the cephalic organ and into the body. There is no apparent connection with the tail. Several transverse commissures connect the longitudinal nerve cords throughout the body and several associated cell bodies have been located. A double-stranded dorsal and ventral longitudinal nerve cord extends the length of the tail and six cell bodies are associated with these cords, uniquely demonstrating either FMRFamide and S1, or 5-HT-like IR. Only 5-HT-like IR was found to extend into the posterior tail furcae and there appears to be a lack of any peripheral tegumental innervation. Double-labelling experiments suggest that the serotoninergic and peptidergic components of the cercarial nervous system are distinct.

An appreciation of Professor John Lewis

“…Very little was known about this pathogenic fluke, but when funding was achieved from research councils and the NRA (Thames Region) much work was undertaken to determine the morphology, life cycle, migration, development and histopathology of S. inermis in carp (Kirk & Lewis, 1992, 1993, 1994, 1996, 1998). Ultrastructural studies were also undertaken on the egg and miracidium of S. inermis and the distribution of serotonergic and peptidergic components within the cercarial nervous system (McMichael-Phillips et al, 1992a, b, 1996). The successful maintenance of S. inermis in the laboratory (Kirk & Lewis, 1992) allowed further progress to be made on immunological aspects, including cellular responses of carp to eggs of S. inermis , changes to the cellular composition of the spleen and pronephros in infected carp, and in vitro polarization of carp leucocytes and adherence of these leucocytes to adult worms and cercariae of S. inermis (Richards et al ., 1994a, b, 1996a, b).…”

Fasciola hepatica: surfaces involved in movement of miracidia and cercariae

“…Serotonin (5-HT) is an excitatory transmitter in the body wall musculature of F. hepatica (Tembe et al, 1993). In the tail of the cercaria of Sanguinicola inermis (McMichael-Phillips et al, 1996) cell bodies associated with the ventral and dorsal longitudinal nerve cords demonstrated either FMRFamide and S1 or 5-HT-like immunoreactivity. In the cercarial tail of S. inermis only 5-HT extended into the posterior tail furcae and there is other evidence that the serotinergic and peptidergic components of the nervous system are distinct.…”