Ocean sunfishes can possess an enormous number of ova in the hundreds of millions (Nelson 1994, Carwardine 1995 and See Thys et al (2020) for new world records. Despite the sunfish’s prolific ova production, larval sunfishes are sampled infrequently in plankton surveys and little is known about their spawning events.
After they hatch, rotund sunfish larvae develop conspicuous, protrusive spines (see below) presumably to deter predators and reduce larval mortality (Thys et al. 2020). At this stage, it is possible to visually distinguish different sunfish genera (e.g. Masturus, Mola, Ranzania); however, at present, we must rely on molecular techniques (e.g. genetic sequencing) to distinguish different larval sunfish species (Lyczkowski-Shultz 2003, Hellenbrecht et al. 2019). These larval sunfish have been found to be an important episodic prey item for several large, pelagic fishes and seabirds.
Of the five current sunfish species, we know the most about the early life of Ranzania laevis (the slender sunfish). R. laevis larvae are encountered and sampled most frequently (Hellenbrecht et al. 2019) and have been reared from eggs (Leis 1977). To describe early development of the other sunfish genera, Masturus and Mola, we rely on individual specimens captured at different life stages from all around the world to collate descriptions of morphological development. At present, we are still filling in the gaps of some morphological transitions for these fishes.
Early Life Cited Literature:
Carwardine, M., 1995. The Guinness Book of Animal Records. Guinness. Middlesex.
Hellenbrecht, L., M. Freese, J. Pohlmann, H. Westerberg, T. Blancke and R. Hanel. 2019. Larval distribution of the ocean sunfishes Ranzania laevis and Masturus lanceolatus (Tetraodontiformes: Molidae) in the Sargasso Sea subtropical convergence zone. Journal of Plankton Research 41: 595–608.
Leis, J.M. 1977. Development of the eggs and larvae of the slender mola, Ranzania laevis (Pisces, Molidae). Bulletin of Marine Science 27(3): 448–466.
Lyczkowski-Shultz, J. 2003. Preliminary guide to the identification of the early life history stages of molid fishes of the western central North Atlantic. In: W.J. Richards [eds.]. Early Stages of Atlantic Fishes: An Identification Guide for the Western Central North Atlantic. (August) NOAA Technical Memorandum NMFS-SEFSC-504, 10pp.
Nelson, J.S., 1994. Fishes of the world. 3d ed. Wiley, New York.
Thys, T.M., T. Nakatsubo, M. Nyegaard, I. Potter, J. Ryan, J. Whitney et al. 2021 Ocean Sunfish
Larvae: Detection, Identification and Predation pp. 105-129. In: T. M. Thys, G.C. Hays and J.D.R.
Houghton [eds.]. The Ocean Sunfishes: Evolution, Biology and Conservation, CRC Press. Boca
Raton, FL, USA. See this reference for ontogenetic sequences of larval molids.
Mola mola larvae
Masturus lanceolatus larvae
Ranzania laevis larvae