biology

Pseudobathylagus

Pseudobathylagus is a biology 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 Pseudobathylagus rather than just read about it. In short: Pseudobathylagus milleri, the Stout blacksmelt, also called the Owlfish due to its large eyes relative to its body, is a species of deep-sea smelt native to the north Pacific Ocean where it is found to depths of 6,600 m (21,700 ft). This species grows to a length of 16.5 cm (6.5 in).

Key takeaways

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

Reference excerpt

Pseudobathylagus milleri, the Stout blacksmelt, also called the Owlfish due to its large eyes relative to its body, is a species of deep-sea smelt native to the north Pacific Ocean where it is found to depths of 6,600 m (21,700 ft). This species grows to a length of 16.5 cm (6.5 in). It is the only species in the genus Pseudobathylagus.

Description, taxonomy, and etymology Pseudobathylagus milleri is a deep-sea smelt that was originally characterized as Bathylagus milleri by D. S. Jordan and C. H. Gilbert in 1898 based on a specimen collected at Cortes Bank, 1,419 m (4,660 ft) from the surface. It was named after their linguist colleague at Stanford University, Walter Miller, for his contribution to zoological nomenclature. In 1939, W. M. Chapman described a new species Bathylagus alascanus, named after the location they were collected from, Alaska. However, Chapman's specimens were later considered to be also B. milleri. In 1986, N. V. Parin described anatomical differences compared to Bathylagus species, such as the absence of orbitosphenoid and postcleithrum. He thus reclassified it to Pseudobathylagus milleri (from Greek ψεύδης, pseudés = false), which is currently the only species under Pseudobathylagus. Parin also noted that the eyes of larvae are not stalked, which is a common feature among Bathylagus. The eyes are remarkably larger compared to other fishes in Bathylagidae as well, leading to the common name "Owlfish".

Ecology Pseudobathylagus milleri is widely distributed across the North Pacific Ocean, having been spotted from the east coast of Japan to the west coast of the U.S., and as far north as the Bering Sea. As a deep-sea smelt, Pseudobathylagus milleri generally lives in the mesopelagic and bathypelagic zones of the ocean. Nevertheless, specimens have been collected from depths of as shallow as 250 m (820 ft) and as deep as 6,600 m (21,700 ft). Their diet include small crustaceans such as Copepoda and Gammaridea. Gut content examination also found parasitic digenean trematodes in Pseudobathylagus milleri, including Aponurus argentini in the stomach, and Steringophorus congeri and Paraccacladium sp. in the intestine.

Reproduction and development The reproduction of Pseudobathylagus milleri is oviparous. Larvae have been reported to be more abundant during spring from December to April. The larvae are about 5 mm long when hatching. The body length of adults can range from below 10 cm (3.9 in) to over 20 cm (7.9 in).

Genetics Pseudobathylagus milleri has 30 pairs of chromosomes (2n = 60). They vary greatly in size, with the X chromosome being the largest and about twice of the next largest, seven pairs of intermediate sizes, and the Y chromosome among the smallest, dot-like chromosomes. The nuclear genome has not been sequenced, but partial sequences of some mitochondrial genes, including cytochrome oxidase subunit I and cytochrome b, are available for DNA barcoding.

References

External links Video of a squid subduing and killing an owlfish from the Monterey Bay Aquarium Research Institute.

Illustrations

Worked examples

Example 1 — a first encounter with Pseudobathylagus

Start with the simplest possible case. Write down what Pseudobathylagus claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, 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 Pseudobathylagus 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 Pseudobathylagus 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 Pseudobathylagus

In research: Pseudobathylagus appears in biology 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 Pseudobathylagus 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: Pseudobathylagus is common in secondary-school and first-year university syllabi. It links to neighbouring topics Bathylagidae, Deep sea fish, Fish described in 1898, so understanding it makes those chapters shorter.
In everyday life: Look for Pseudobathylagus 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 Pseudobathylagus in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Pseudobathylagus 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 Pseudobathylagus out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Pseudobathylagus in simple terms?

Why does Pseudobathylagus matter?

Because it connects several biology 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 Pseudobathylagus?

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 Pseudobathylagus.