science

Leiognathidae

Leiognathidae is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Leiognathidae rather than just read about it. In short: Leiognathidae, the ponyfishes, slipmouths or slimys / slimies, are a small family of fishes in the order Acanthuriformes. They inhabit marine and brackish waters in the Indo-Pacific.

Key takeaways

Leiognathidae belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Leiognathidae to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Leiognathidae from memory before moving on to harder problems.

Reference excerpt

Leiognathidae, the ponyfishes, slipmouths or slimys / slimies, are a small family of fishes in the order Acanthuriformes. They inhabit marine and brackish waters in the Indo-Pacific. They can be used in the preparation of bagoong.

Characteristics Ponyfishes are small and laterally compressed in shape, with silvery colouration. They are distinguished by highly extensible mouths, and the presence of a mechanism for locking the spines in the dorsal and anal fins. They also possess a highly integrated light organ in their throats that houses symbiotic bioluminescent bacteria that project light through the animal's underside. Typically, the harbored bacterium is only Photobacterium leiognathi, but in the two ponyfish species Photopectoralis panayensis and Photopectoralis bindus, Photobacterium mandapamensis is also present. Two of the most widely studied uses for luminescence in ponyfish are camouflage by ventral counterillumination and species-specific sexual dimorphism. The light organ systems of ponyfishes are highly variable across species and often between sexes.

Taxonomy Leiognathidae was classified within the suborder Percoidei by the 5th edition of Fishes of the World, but it was placed in an unnamed clade outside the superfamily Percoidea. This clade contains 7 families which appeared to have some relationship to Acanthuroidei, Monodactylidae, and Priacanthidae. Betancur-Rodriguez et al. (2017) placed the family in the order Chaetodontiformes alongside the family Chaetodontidae. More recent classifications place Leiognathidae and the other aforementioned families in the order Acanthuriformes.

Genera The following genera are classified within the Leiognathidae, divided between two subfamilies based on Eschmeyer's Catalog of Fishes:

Subfamily Leiognathinae Gill, 1893 Aurigequula Fowler, 1918 Leiognathus Lacepède, 1802 Subfamily Gazzinae Chakrabarty & Sparks, 2015 Deveximentum Fowler, 1904 (previously as replacement name Secutor Gistel, 1848) Equulites Fowler, 1904 Eubleekeria Fowler, 1904 Gazza Rüppell, 1835 Karalla Chakrabarty & Sparks, 2008 Nuchequula Whitley, 1932 Photolateralis Sparks & Chakrabarty, 2015 Photopectoralis Sparks, Dunlap & Smith, 2005 The following fossil genera are also known:

†Eoleiognathus Bannikov, 2014 (Early Eocene of Italy) †Euleiognathus Yabumoto & Uyeno, 2011 (Middle Miocene of Japan) †Leiognathoides Bannikov, 2001 (Early Oligocene to Early Miocene of Switzerland, Azerbaijan and North Caucasus, Russia)

References

Illustrations

Worked examples

Example 1 — a first encounter with Leiognathidae

Start with the simplest possible case. Write down what Leiognathidae claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Leiognathidae before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Leiognathidae ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Leiognathidae

In research: Leiognathidae appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Leiognathidae in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Leiognathidae is common in secondary-school and first-year university syllabi. It links to neighbouring topics Acanthuriformes families, Bioluminescent fish, Extant Eocene first appearances, so understanding it makes those chapters shorter.
In everyday life: Look for Leiognathidae outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Leiognathidae in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Leiognathidae means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Leiognathidae out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Leiognathidae in simple terms?

Leiognathidae, the ponyfishes, slipmouths or slimys / slimies, are a small family of fishes in the order Acanthuriformes. They inhabit marine and brackish waters in the Indo-Pacific.

Why does Leiognathidae matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Leiognathidae?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Leiognathidae.