Amphioxus Gut Hormones

Cross references:   Amphioxus Hormones      Endostyle = Thyroid    
Lamellar Body = Pineal Gland  
Amphioxus Pituitary     Amphioxus Gonads   
Amphioxus Stress Hormones     Amphioxus Oxytocin    Amphioxus Genomics  

Enteric Endocrine System (Goog) 
This description of the endocrine system of the human gut is provided for reference. 

Immunohistochemical localization of polypeptide hormones in endocrine cells of the digestive tract of Branchiostoma lanceolatum
    "The digestive tract of the cephalochordate Branchiostoma lanceolatum was investigated with regard to occurrence and distribution of endocrine cells. By the use of the peroxidase-antiperoxidase (PAP) technique, cells in the gut epithelium reacting with antisera against 8 different mammalian polypeptide hormones were localized. Positive reactions were obtained with antisera against the four mammalian islet hormones (insulin, glucagon, pancreatic polypeptide, somatostatin) and against secretin, vasoactive intestinal polypeptide, pentagastrin and neurotensin. No immunoreactivity was found with antisera against members of the lipotropin family (ACTH, met-enkephalin, agr-endorphin), against big-gastrin, cholecystokinin, substance P and moulin.

The amphioxus genome illuminates vertebrate origins and cephalochordate biology

Full length article available online.
"The insulin superfamily includes insulin, insulin-like growth factors (IGFs), and relaxins. In vertebrates, insulin is produced by the pancreas, a gut derivative, and is essential for regulating glucose metabolism. IGF is critical for growth, and relaxins are associated with parturition among other roles.
    Amphioxus lacks a morphologically defined pancreas, but particular cells in the gut express an insulin-like peptide (Chan et al. 1990; Holland et al. 1997). In addition to this gene, we identified five other insulin/relaxin-related genes and their putative receptors in the amphioxus genome. Three of the insulin/relaxin-related genes are linked in the genome. Phylogenetic analysis of neighboring genes revealed synteny of four of the six insulin-like peptides with human paralogons hosting the insulin/IGF and relaxin-type genes ... The organization of the corresponding genomic region in Ciona is similar (Olinski et al. 2006), indicating that insulin and relaxin-type precursor genes were positioned in one chromosomal segment in the ancestral chordate.
Also considered in 
Amphioxus Hormones  Endostyle = ThyroidAmphioxus Genomics