Homarine (N-methylpicolinic acid) and trigonelline (N-methylnicotinic acid) appear to be involved in pattern control in a marine hydroid.

A morphogenetically active compound has been isolated from tissue extract of Hydractinia echinata and identified to be N-methylpicolinic acid (homarine). When applied to whole animals, homarine prevents metamorphosis from larval to adult stage and alters the pattern of adult structures. The concentration of homarine in oocytes is about 25 mM. During embryogenesis, metamorphosis and early colony development the overall homarine content does not change. Adult colonies contain a fourfold lower homarine concentration than larvae. The polyp's head contains twofold more homarine than the gastric region and the stolons. A second, similarly active compound, N-methylnicotinic acid (trigonelline), has also been identified in Hydractinia tissue at concentrations about one-third that of homarine. Incubation of larvae in 10 to 20 microM-homarine or trigonelline prevents head as well as stolon formation. If the compounds are applied in a pulse during metamorphosis, a large part of the available tissue forms stolons. Since microM concentrations of homarine and trigonelline are morphogenetically active, whereas mM concentrations are present in the tissue it appears that both substances are stored within the tissue.