Parazoa Hormones

Cross references:   Parazoa    Placozoa   Porifera     Hormones in General    
Evolution of Hormones      Coelenterata Hormones    
Coelenterata Neuropeptides   
Hemichordate Hormones     Protochordate Hormones

Demonstration of an endocrine signaling circuit for insulin in the sponge Geodia cydonium 

Full length article available online.  Click on the 'complete article' link to get a PDF. 
The existence of an insulin-mediated cell-to-cell signaling in the sponge Geodia cydonium is demonstrated in this study by molecular biological and immunological techniques.

Applying immunological and electron microscopical techniques it is shown that insulin is produced in specialized cells (spherulous cells).

Plasma membranes of sponge cells are shown to be provided with an insulin-binding receptor composed of two molecules (Mr 104,000 and Mr 98,000). Heterologous insulin (from bovine pancreas) was found to stimulate gene expression in G. cydonium cells. It is concluded that sponges are provided with an endocrine signaling circuit: signaling cells (spherulous cells), hormone (insulin), and hormone receptor bearing target cells which respond to the hormone stimulus.

    Identified Hormones, Neurotransmitters or Neuromodulators

Insulin (Wiki)

Neuroactive substances specifically modulate rhythmic body contractions in the nerveless metazoon Tethya wilhelma (Demospongiae, Porifera) 
    Sponges (Porifera) are nerve- and muscleless metazoa, but display coordinated motor reactions. Therefore, they represent a valuable phylum to investigate coordination systems, which evolved in a hypothetical Urmetazoon prior to the central nervous system (CNS) of later metazoa. We have chosen the contractile and locomotive species Tethya wilhelma (Demospongiae, Hadromerida) as a model system for our research, using quantitative analysis based on digital time lapse imaging. In order to evaluate candidate coordination pathways, we extracorporeally tested a number of chemical messengers, agonists and antagonists known from chemical signalling pathways in animals with CNS.
    Sponge body contraction of T. wilhelma was induced by caffeine, glycine, serotonine, nitric oxide (NO) and extracellular cyclic adenosine monophosphate (cAMP). The induction by glycine and cAMP followed patterns varying from other substances. Induction by cAMP was delayed, while glycine lead to a bi-phasic contraction response. The frequency of the endogenous contraction rhythm of T. wilhelma was significantly decreased by adrenaline and NO, with the same tendency for cAMP and acetylcholine. In contrast, caffeine and glycine increased the contraction frequency. The endogenous rhythm appeared irregular during application of caffeine, adrenaline, NO and cAMP. Caffeine, glycine and NO attenuated the contraction amplitude. All effects on the endogenous rhythm were neutralised by the washout of the substances from the experimental reactor system.
    Our study demonstrates that a number of chemical messengers, agonists and antagonists induce contraction and/or modulate the endogenous contraction rhythm and amplitude of our nerveless model metazoon T. wilhelma. We conclude that a relatively complex system of chemical messengers regulates the contraction behaviour through auto- and paracrine signalling, which is presented in a hypothetical model. We assume that adrenergic, adenosynergic and glycinergic pathways, as well as pathways based on NO and extracellular cAMP are candidates for the regulation and timing of the endogenous contraction rhythm within pacemaker cells, while GABA, glutamate and serotonine are candidates for the direct coordination of the contractile cells.
    Full length article available online for free.     

Click on the link, below, for a very informative table. 

Table 2

Table 2
Summary of induced effects on Tethya wilhelmaOverview regarding induced contraction, endogenous contraction rhythm alteration and/or amplitude attenuation by substances used in the present and previous study, including effects on sponges, reported by (more ...)   
    Identified Hormones, Neurotransmitters or Neuromodulators
caffeine, glycine, serotonine, nitric oxide (NO) and extracellular cyclic adenosine monophosphate (cAMP). 
adrenergic, adenosynergic and glycinergic pathways, as well as pathways based on NO and extracellular cAMP 
GABA, glutamate and serotonine 
    My comment
It should be noted that the substances listed above were "extracorporeally tested" and not identified as occurring naturally in the sponge.  I think that this may disqualify them as "hormones". 

    GABA and glutamate specifically induce contractions in the sponge Tethya wilhelma.
Only abstract available online.
    "Sponges (Porifera) are nerve- and muscleless. Nevertheless, they react to external stimuli in a coordinated way, by body contraction, oscule closure or stopping pumping activity. The underlying mechanisms are still unknown, but evidence has been found for chemical messenger-based systems. We used the sponge Tethya wilhelma to test the effect of gamma-aminobutyric acid (GABA) and glutamate (L: -Glu) on its contraction behaviour.
    Minimal activating concentrations were found to be 0.5 microM (GABA) and 50 microM (L: -Glu), respectively. Taking maximum relative contraction speed and minimal relative projected body area as a measure of the sponge's response, a comparison of the dose-response curves indicated a higher sensitivity of the contractile tissue for GABA than for L: -Glu. The concentrations eliciting the same contractile response differ by about 100-fold more than the entire concentration range tested. In addition, desensitising effects and spasm-like reactions were observed. 
   Presumably, a GABA/L:-Glu metabotropic receptor-based system is involved in the regulation of contraction in T. wilhelma."   
    Identified Hormones, Neurotransmitters or Neuromodulators:
GABA, Glutamate 
    My comment
Although not specifically stated in the Abstract, it sounds as though the GABA and Glutamate were applied externally rather than found to be natural elements of the sponge.  It seems to me that this should disqualify them as hormones.