#amphipoda

[bowelfly]

inkwash bugs

[dailybugfacts]

Pretty niche and disgusting, but I've always been fascinated by whale lice- entire groups of organisms that live exclusively on other massive animals, like an oceanic version of a turtle carrying a continent. Know anything about them?

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TODAY'S FACT IS

Did you know that Whale Lice (Cyamidae family) aren't actually lice? These crustaceans are more closely related to the skeleton shrimp than any insect. Each species of this parasitic crustacean prefers a specific species of whale to call host. The sperm whale, however, has 2 different whale lice, as one species, Cyamus catodontis, lives on male sperm whales and Neocyamus physeteris is only found on females and calves. These parasites tend to eat the algae and flaking skin on the outside of the whale's body.

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Photo of Neocyamus Physeteris by Jakob Fahr

[bestanimal]

Round 3 - Malacostraca - Amphipoda

(Sources - 1, 2, 3, 4)

Order: Amphipoda

Common Name: no common name for the whole order, other than “amphipods”, though freshwater species are often called “freshwater shrimp”, “scuds”, or “sideswimmers”

Suborders*: 6 - Amphilochidea (89 families), Colomastigidea (2 families), Hyperiidea (35 families), Hyperiopsidea (3 families), Pseudingolfiellidea (1 family), and Senticaudata (109 families)

*(I am not listing families as, as you can see above, it would take up too much space)

Anatomy: no carapace; one pair of sessile (stalk-less) compound eyes; two pairs of antennae; gills on the coxae (base of the leg); generally laterally compressed body divided into 13 segments; head is fused to the thorax; gnathopods (uniquely modified feeding legs)

Diet: mostly detritivores or scavengers; some are grazers of algae, omnivores, or predators of small insects and other crustaceans

Habitat: found in almost all aquatic environments, from fresh water to water with twice the salinity of sea water, from the tideline to the deepest known point of the ocean; some species of the family Talitridae are terrestrial

Evolved in: Lower Carboniferous

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Voting ended onAug 21, 2025

Propaganda under the cut:

The largest amphipod species is the Supergiant Amphipod (Alicella gigantea) (image 2), a deep sea amphipod which can reach up to 34 cm (13 in) in length. This may not seem “supergiant”, but it is actually quite massive for an amphipod, most of which are typically less than 10 millimetres (0.4 in) long!

Terrestrial species of the family Talitridae are commonly called “landhoppers”, and those that live on beaches are often referred to as “sandhoppers” or “sand fleas” (though they do not bite people as true fleas do). The sandhopper Talitrus saltator (image 3) has been the subject of a great deal of scientific research, to determine the environmental cues which it uses to control its behavior. The species feeds on rotting seaweed which accumulates on the strandline, and thus adjusts its schedule to the tides. It spends its day buried 10–30 cm (3.9–11.8 in) deep in the sand, above the strandline, emerging at night when the tide has fallen. The sandhopper is capable of determining where the sea is, using multiple indicators: including the angle of the sun, moon, or even by detecting the blue wavelengths of light from the sea and the red-brown colors of land.

There are over 350 species of amphipod native to Russia’s ancient Lake Baikal.

Compared to other crustacean groups, such as the Isopoda, Rhizocephala, or Copepoda, relatively few amphipod species are parasitic to other animals.

In populations found in benthic ecosystems, amphipods play an essential role in controlling brown algae growth.

Amphipods are bioindicators, meaning that they are often used by ecologists to determine the health of an ecosystem.

[uncharismatic-fauna]

Uncharismatic Fact of the Day

If you need a bottle opened, look no further than Capropodocerus kamaitachi! A relative of sandhoppers, this species was discovered in 2023 by Yu Matsumoto et al. It's only 5.4 mm (0.21 in) long, and is currently known to reside in the Kumano Sea at depths of 840–873 m (2755-2864 ft). It's large claws, also known as gnathopods, are used to grab food or grasp mates.

[snototter]

A pair of skeleton shrimp (Caprellidae sp.) fighting

by Alexander Semenov

[herpsandbirds]

Phronima, family Phronomidae, order Amphipoda, Gulf of Aqaba, north Red Sea

This is a genus of small deep sea hyperiid amphipod crustaceans.

Phronima rear their young, and sometimes live in, the empty "tunics" of tunicates (sea squirts), which they kill and eat.

They are also known as "pram bugs" and "barrel shrimp".

photograph by Gil Koplovitz

[every-day-creechur]

Anonyx spp.

A genus of marine amphipods found in northern oceans.

image by James Robert Taylor

[todropscience]

DEEP-SEA DOMINANCE: THE SUPERGIANT AMPHIPOD ACROSS THE ABYSS

The deep-sea amphipod Alicella gigantea, described in 1899, currently known as the world’s largest amphipod, inhabits depths of the lower abyssal and upper hadal zones. Historically, it has been sampled or observed in situ infrequently relative to other deep-sea amphipods, suggesting low population densities and providing a sense of rarity. Consequently, little is known about the demography, genetic variation and population dynamics of A. gigantea.

Although elusive, Alicella gigantea is one of the most widely distributed amphipods known, thriving across more than half of the world’s oceans, according to a recent study by researchers at the University of Western Australia. Amphipods like A. gigantea are shrimp-like crustaceans with narrow bodies and a distinctive hunched posture. They inhabit nearly every aquatic habitat on Earth, from shallow coasts to the hadal trenches, though their numbers dwindle with increasing depth.

In the most comprehensive assessment to date, scientists compiled 195 records from 75 locations across the Pacific, Atlantic, and Indian Oceans, including both published data and new expeditions. Genetic analysis of mitochondrial and nuclear genes revealed extremely low divergence among global populations, supporting the existence of a single, globally distributed species. The haplotype network showed minimal regional differentiation, with shared haplotypes across vast distances and the Pacific identified as the species’ main stronghold. Far from being rare, A. gigantea occupies nearly 60% of the global ocean, a silent giant spanning the deep.

Main photograph: The supergiant amphipods. Oceanlab, University of Aberdeen, UK.

Reference (Open Access): Paige et al., 2025. The supergiant amphipod Alicella gigantea may inhabit over half of the world’s oceansR. Soc. Open Sci.