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Because larvae differ so much from adults (the analogy with caterpillars and butterflies is appropriate), they are difficult to identify.
Research Scientist: Dr Jeff Leis
Nearly all bony fishes, especially marine ones, have a pelagic larval stage which is morphologically very different from the adult. In general, these larvae live in different places than the adult, have different behaviours, eat different foods and have different predators. During this larval phase, the tiny fish develops from little more than an egg with a tail to a miniature adult with all organs fully operational. In addition, many species have highly specialised larval morphologies, with various structures such as strong spines on the head, that are modified or lost upon metamorphosis.
Larval Fish Systematics
Because larvae differ so much from adults (the analogy with caterpillars and butterflies is appropriate), they are difficult to identify. Much research effort involves working out developmental series of fishes, and describing these to enable other researchers to identify larvae, including many of commercial importance. Once the development (or, ontogeny) of these fishes is understood, it can be used to help understand the relationships. The major group under study at present is the Family Lutjanidae, or the tropical snappers, an important commercial, world-wide, warm-water group. The proceedings of a symposium titled "Fish Larvae and Systematics: Ontogeny and Relationships" (co-organized and co-edited by Drs Jeffrey M Leis, John E Olney and Muneo Okiyama) appeared in the Bulletin of Marine Science in early 1997.
This research has been funded by ARC and the Australian Museum. External collaborators on larval fish systematics research include Dr H Geoffrey Moser, US National Marine Fisheries Service, La Jolla, California; Dr Lynnath Beckley of the Oceanographic Research Institute, Durban, South Africa; and Mr Carl van der Lingen of Sea Fisheries, Capetown, South Africa. Projects are also under way with Australian Museum staff and associates Ms Sally E Reader, Ms Dianne J. Bray, Ms Brooke Carson-Ewart, Dr Tom Trnski, Dr Tony Miskiewicz, Ms Krysia Lee and Ms Suzanne Bullock.
We recently published an identification guide to fish larvae that covers 120 families. The illustrations on this page are taken from that book:
Leis, J.M. and B.M. Carson-Ewart. (editors). 2000. The larvae of Indo-Pacific coastal fishes. An identification guide to marine fish larvae. (Fauna Malesiana Handbooks 2). E.J. Brill, Leiden. ( A soft cover version of this book was published in 2004).
-Abstracts of other recent papers from this project:
Larval development of Pagellus natalensis and evaluation of what larval morphology indicates about relationships in the perciform fish family Sparidae
Jeffrey M. Leis1, Thomas Trnski1 and Lynnath E. Beckley2
1 Ichthyology, and Centre for Evolutionary Research, Australian Museum, 6 College Street, Sydney, NSW 2010, Australia. Email Jeff Leis
2 Oceanographic Research Institute, P.O. Box 10712, Marine Parade, Durban 4056, South Africa.
Abstract. We describe the larval development of Pagellus natalensis based on 34 field specimens of 2-19 mm from the western Indian Ocean off South Africa. P. natalensis has unusual larval morphology for a sparid: in particular, extensive head spination including a serrate supraoccipital crest, serrate supraocular, pterotic, and supracleithral ridges, interopercular spines, strong preopercular spination and pitted frontal bones. Development in the family Sparidae is briefly reviewed, and larval development of P. natalensis is central to this review. We suggest what larval morphology might reveal about sparid relationships, and pose several hypotheses for further testing. These include: Pagellus, Pagrus and Dentex as currently conceived are polyphyletic; Pagellus affinis, bellottii and natalensis and Pagruspagrus are closely related; spiny larval morphology is derived within the Sparidae and indicates that the currently recognized subfamilies are polyphyletic; Spondyliosoma is monophyletic; Calamus and Spondyliosoma are sister taxa.
Marine and Freshwater Research 53: 367-376.
Larval development of Achoerodus viridis (Pisces: Labridae), the Australian Eastern Blue Groper.
Jeffrey M Leis1 and Amanda C Hay
Ichthyology and Center for Biodiversity and Conservation Research, Australian Museum, 6 College Street, Sydney, NSW 2010, Australia
1 contact author (Email Jeff Leis)
Abstract. Larvae of the south-eastern Australian endemic hypsigenyin labrid Achoerodus viridis are described and illustrated from 30 specimens (3.0-9.6 mm) captured in plankton nets and larval-fish beach seines. Development is typical for labrids. Larvae of A. viridis can be distinguished from those of other labrids because they possess distinctive pigment, 28 myomeres, and fin-ray counts of D XI,11, A III,11, and P1 16-18. Larvae of closely-related hypsigenyin labrid genera are poorly known, but similar. Adult A. viridis live on coastal rocky reefs. Larvae of 3.0-8.2 mm were found over the continental shelf off central New South Wales in the Western Tasman Sea. Larvae of 6.6-7.7 mm were captured in a tidal channel leading to an estuarine lagoon, and the smallest larvae captured in sea grass beds in the lagoon were 7.2 and 8.5 mm.
Ichthyological Research 51(1):46-51.
A larva of the eteline lutjanid, Randallichthys filamentosus (Pisces: Perciformes), with comments on phylogenetic implications of larval morphology of basal lutjanids
Jeffrey M Leis
Ichthyology, Aquatic Zoology, Australian Museum, 6 College St, Sydney, NSW 2010, Australia
1 contact author (Email Jeff Leis)
Abstract. The only known larva of Randallichthys filamentosus, a 9.7 mm specimen, is characterized by finray counts of D X,11, A III, 9, ~50 lateral-line scales, an extremely long and whip-like spine 2 of the dorsal fin (80% body length), and very long first ray of the pelvic fin (74% body length). Like all eteline larvae, it is fully scaled at a small size. Within the Lutjanidae, this larva shares the otherwise unique morphological features of very elongate whiplike dorsal-fin spine and very elongate pelvic-fin ray with some species of the apsiline genus Paracaesio. Evidence from larvae supports Johnson’s hypothesis, based on adult morphology, that the Etelinae and Apsilinae are basal lutjanids. The morphology of lutjanid larvae, however, suggests several hypotheses of relationships within basal lutjanids that differ from those based on adult morphology: that the lutjanid subfamilies Etelinae and Apsilinae form a monophyletic group, that Paracaesio is polyphyletic, that Randallichthys and some Paracaesio spp. are closely related, and that Aphareus is closely related to Pristipomoides, not Randallichthys.
Published in Zootaxa 1008: 57 – 64 (2005)
- Australian Museum Larval Fishes website
2. Leis, J.M. and B.M. Carson-Ewart. (editors). 2000. The larvae of Indo-Pacific coastal fishes. An identification guide to marine fish larvae. (Fauna Malesiana Handbooks 2). E.J. Brill, Leiden. ( A soft cover version of this book was published in 2004).