#amphipoda

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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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(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

Propaganda under the cut:

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.

A pair of skeleton shrimp (Caprellidae sp.) fighting

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".

Anonyx spp.

A genus of marine amphipods found in northern oceans.

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.