I love this for two reasons –

1) Teasing out details of another fish’s larval and juvenile development phases, even if in captivity, is a great addition to our body of knowledge.

2) Captive bred Candy Bass for the aquarium industry! Anytime another fish is added to the ranks of captive bred for the aquarium industry it’s a big plus for breeders, aquarium enthusiasts and conservation.

This is a great effort and success from Todd Gardner at the Long Island Aquarium to get at least one (and hopefully nearly a dozen) Liopropoma sp. larvae to the settlement. Congratulations!

I absolutely love the high-flying dorsal extensions on these larvae. I’m sure that it caused Todd no end of problems, but it is magnificent!

Click here to view the embedded video.

Just returned from a wonderful week as teaching assistant for a coral reef ecology course that has a field component in Belize on the Meso-American reef. While I love the reefs and seagrass beds, one of my favorite spots to visit in Belize is Twin Cayes- an amazing mangrove caye. Drifting down the channel that separates the two cayes is something I look forward to every trip. Unfortunately my compatriots usually end up pulling me out of the channel as I often take a full hour to explore the same area they cover in maybe 20 minutes, but then that is the secret of enjoying the mangrove channel: minimize any movement as it stirs up silt and organics and go slow, very, very slow, edging along the prop roots at the side of the channel and allow time to take it all in.

Welcome to the Mangroves! (c) Eric Heupel

As the others go screaming along the channel, I wait well behind, letting the silt clear and the animals recover from their passage. The reward is a wealth of invertebrate and fish life, and one of my favorite marine denizens of Belize: the juvenile Sergeant Major.

A juvenile sergeant major in the mangroves, ~1.5cm long (c) Eric Heupel

In Belize, we find juvenile sergeant majors in the shallows under docks and similar structures as well as in the mangroves. The adults are common in the patch reef and very common in the continuous fore-reef areas. Adults feed on coraline algae, copepods and other small crustaceans, anemones, tunicates, and invertebrate larvae. Juveniles appear to feed on benthic and planktonic algae, invertebrate larvae and small crustaceans (copepods especially?). Matt Wittenrich at Florida Institute of Technology has successfully (though with great difficulty) raised larvae from egg hatch through metamorphosis by feeding them green water and wild caught plankton using a flow through system to clear out whatever the juveniles did not eat. He noted through observations they would eat rotifers and green water (algae) but really grew best when they had plenty of copepods to eat. Below are his images of the larval development from ~1 day post hatch to ~20 days post hatch when metamorphosis is complete.

Abudefduf Larval Life Cycle (c) Matt Wittenrich

Juvenile sergeant majors are one of the fish I see most commonly under the prop roots of Twin Cayes. They alternate between flitting nervously around a prop root or patch of algae as I come past and charging out to challenge me, then retreating back to the safety of prop root or algae “nest”, which is a behavior they continue to show out on the patch reef when they are 15cm in size.

Classification

Kingdom

Animalia

Phylum

Chordata

Class

Actinopterygii

Order

Perciformes

Family

Pomacentridae

Genus

Abudefduf

Species

Abudefduf saxatilis

While most of the larvae out there are from crustaceans and insects, larvae come from a wide variety of taxonometric groups including several groups of Chordates. Today’s animal is one of my favorite larvae of all from Belize – the Spotted Trunkfish (Lactophrys bicaudalis (Linnaeus, 1758)). My idea of a perfect day out would be to dive on the reef at Carrie Bow Cay in the early morning and then spend the rest of the day snorkeling in the mangroves nearby, looking for and at the larval forms of fish and the invertebrates. So, on to the trunkfish…

Juvenile Spotted Trunkfish (Lactophrys bicaudalis)

While fish don’t go through complete metamorphosis, many species do go through radical changes from birth through “settlement”. In Belize many of the larval, and post larval juvenile, forms of reef fish can be found in the mangroves including the boxfishes (Ostraciidae), a family of teleost fish which includes fish often named cowfishes and trunkfishes. On my trip to Belize I was thrilled to find some juvenile spotted trunkfish, like the one above, among the mangroves myself. The above picture however is from the Smithsonian Institution’s Larval Fish Group. The Larval Fish Group is one of several excellent resources for larval fish.

Eventually this small (~1.0cm) larvae will grow to become an up to 40cm long (~16″) adult feeding on algae and small benthic (bottom) invertebrates such as mollusks, crustaceans, tunicates, sessile tunicates, and echinoderms (sea stars, sea cucumbers and urchins). They spawn at dusk releasing large eggs (~2mm) into the pelagic ocean. After hatching the larvae will remain in the nekton. The plates that form their armor begin to develop as lumps in the early preflexion larval stages. In Gulf of Mexico sampling they were rarely found and at the pre-settlement stages there were no uniquely distinguishing characteristics to allow identification of pelagic larvae to the genus or species levels. According to William’s wonderful Early Stages of Atlantic Fishes (Marine Biology), Ostraciidae spend a short amount of time as pelagic ichthyoplankton, settling rapidly to seagrass beds and mangroves. Eventually they do recruit back to the reefs to settle and develop a fiercely guarded territory on the reef.

Here then is the adult form:

mature Spotted Trunkfish

Two interesting bits about Spotted Trunkfish:

• They hunt by blowing jets of water into the sediments around the reef to uncover and dislodge the small inverts.
• Some boxfishes (Ostraciidae), including the Spotted Trunkfish (L. bicaudalis) have another form of defense beside their armor. They release a compound called ostracitoxin when stressed which can kill other fish, making members of the boxfish a poor choice for aquaria.

Classification

Kingdom

Animalia

Phylum

Chordata

Class

Actinopterygii (Ray-finned fishes)

Order

Tetraodontiformes (Puffers and filefish)

Family

Ostraciidae (Boxfishes, Cowfishes and Trunkfishes)

Genus

Lactophrys

Species

Lactophrys bicaudalis

References

Böhlke, J.E. and C.C.G. Chaplin, (1993) Fishes of the Bahamas and adjacent tropical waters. 2nd edition. University of Texas Press, Austin.

Richards, W.J.(ed.). (2006) Early Stages of Atlantic Fishes: An Identification Guide for the Western Central North Atlantic. Taylor and Francis, Boca Raton, FL pp. 2640.

Life Photo Meme