Myrrhinidae Family

Family Myrrhinidae

This family, originally raised by Bergh in 1905, has been reinstated by Martynov et al, 2019. It holds the genera Dondice, Godiva, Hermissenda and Phyllodesmium plus the two small monospecific genera, Nanuca and Nemesignis. This is based on morphological and molecular sequencing known for quite some time from other earlier research papers but not considered suitable to adjust at the time. The Phyllodesmium however do not conform to the morphological criteria, the differences being outlined below.

In general, the external physical attributes of the Myrrhinidae are much the same as those of the Facelinidae family from which they have been relocated. They range in size from small to large with elongate and slender but deep bodies, a wide foot and long tapering tail. The anterior corners of the foot may be developed into propodial tentacles that may be short or extremely long, even filiform. Oral tentacles are usually long and tapering. The rhinophores may present as smooth, lamellate, annulate or papillate. There is a diversity of form in the cerata especially in the Phyllodesmium. The cerata may be inserted as arches (most common) or not. In the majority the anus is cleioproctic, located laterally on the right side posterior to the inter-hepatic space and within the cerata.

The Phyllodesmium genus contains by far the greater number of species of the Myrrhinidae family. Phyllodesmium, however, is significantly different on a morphological basis to the other genera of this family, often with substantially modified cerata and a lack of cnidosacs in almost all species. The diet of Phyllodesmium is different as well, feeding on octocorals (soft corals and gorgonians). Many have modified ceratal shape to assist in the solar exposure of and thus the farming of zooxanthellae obtained from their prey. The cerata shape of some mimic the form of their prey. The rhinophores of all the Phyllodesmium, bar one, are smooth or at most, wrinkled.

Hermissenda (NW & NE Pacific distribution) and Godiva species are not discerning with prey and have been termed generalist feeders when it comes to diet. They are known to move swiftly and act aggressively, even to the extent of voraciously consuming other nudibranchs, including their own species.