Arthropod quiz prep 2: Barnacles, isopods, amphipods, stomatopods, hermit crabs, shrimp, prawns, lobsters, spiny lobsters, and true crabs

Scutum

(Thecostraca) a larger, more anterior/dorsal plate forming the movable operculum

Cypris

(Thecostraca) larval stage after nauplius, but before settled juvenile.

Thecostraca reproduction

Known for the largest penis in the animal kingdom. Hermaphroditic, and mating is usually reciprocal. Larval legs end up on top and used to filter feed, head and antennae become involved in substrate attachment along with cement glands.

Nauplius

The first larval stage of Thecostraca,

Thecostraca

Class of barnacles

Thecostraca feeding

Beat their cirri to increase particle capture rate, retract them into the capitulum to bring particles from larger cirri to smaller cirri to the mouth. Prefer larger plankton (zooplankton, crustacean nauplii) than bivalves (phytoplankton)

Crustacea

Subphylum of arthropods including the classes Branchiopoda, Copepoda, Ostracoda, Thecostraca, Malacostraca, and more

Malacostraca

Class of crustaceans including the orders Mysida, Euphausoacea, Cumacea, Tanaidacea, Isopoda, Amphipoda, Stomatopoda, Decopoda, and more

14

Isopoda walking leg count

14

Amphipoda walking leg count

6

Stomatopoda walking leg count

10

Decapoda walking leg count

Dorsoventrally compressed

Isopoda body shape

Cephalothorax

(Isopoda) Head. Hosts 2 pairs of antennae, although the first pair is tiny and hard to see

Isopoda

Order of isopods

Pereopods

Walking legs found on the underside of the pereonites

Pereonites (7x)

(Isopoda) Name and count of segments found on the thorax-equivalent

Pereon

(Isopoda, Amphipoda) Thorax equivalent

Pleon

(Isopoda, Amphipoda) Abdomen equivalent

Pleonites (5x)

(Isopoda) Name and count of segments found on the abdomen-equivalent

Pleopods

(Isopoda) Legs found on the underside of the pleonites. Size, functon, and number vary with sex, but all marine species use involve them in respiration.

Marsupium

(Isopoda, Amphipoda) Pouch on the underside of a female’s pleon where she carries her young until they are juveniles

Isopoda reproduction

Males deposit sperm internally using their pleopods, females develop fertilized eggs in the marsupium intil they develop into mancae

Mancae

Juvenile isopods

Amphipoda

Order of amphipods

Tergum

(Thecostraca) a smaller, more posterior/ventral plate forming the movable operculum

Cephalothorax

(Amphipoda) Head. Hosts two pairs of fairly large antennae

Laterally comporessed

Amphipoda body shape

Pereonites (7x)

(Amphipoda) Name and count of the segments found on the thorax-equivalent

Pleonites (6x)

(Amphipoda) Name and count of segments found on the abdomen-equivalent

Pleopods

(Amphipoda) Legs found on the underside of the pleonites. Six, not five. Help with respiration, but unlike isopods they typically don’t host gills.

Coxae

(Amphipoda) Plates that connect pereopods to the pereon. Also present in isopods, but less visible. Hosts the gills.

Gnathopods

(Amphipoda) Specialized feeding and mating pereopods. Some isopods have them.

Amphipod reproduction

Males grasp females with gnathopods and carry them for days or weeks before copulation. After the female molts, male releases sperm near female who then sweeps it into her marsupium, or the sperm is deposited directly into the pouch. Female carries the eggs in her marsupium until they hatch into fully formed juveniles.

Precopulation

Also called “amplexus”. Mating behavior whereby male amphipods grasp females with their gnathopods and carry them for days or weeks until they molt and copulation can occur.

Gammarids

Suborder of amphipods that looks normal. Benthic, demersal, or infaunal with a laterallu compressed, curved, shrimp-like body. Major grazers of epiphytes.

Caprellids

Family of amphipods with long, stick-like bodies and benthic/sessile-ish lifestyles. The skeleton shrimp.

Hyperiids

Suborder of amphipods that are planktonic with round, transparent bodies and huge eyes.

Stomatopoda

Order of mantis shrimp

Paired penes and genital slit

“business bits” of a stomatopod, used for internal fertilization

Uropods

“showin’ feathers” of a stomatopod, used by males to dance in courtship displays.

Stomatopod reproduction

Internal fertilization after courtship dance; females brood eggs that hatch into larvae. Sometimes monogamous.

Maxillipeds (10x)

Name and count of “nom grabbers” of stomatopods. Used for food handling and communication.

Antennae

“water tasters” of stomatopods. Used for chemosensing.

Pereopods (6x)

(Stomatopoda) Name and count of the walking legs

Pleopods (10x)

(Stomatopoda) Name and count of the swimming/gill hosting appendages (“swimmy flappers” and “breathin’ feathers”)

Raptorial Appendages

(Stomatopoda) Smasher or spearer claws (“danger arms” and “stabby bits”)

Abdomen

(Stomatopoda) Also called the pleon, contains multiple somites (segments). The “scampies”.

Telson

(Stomatopoda) Protective tail plates found after the pleon. The “anti-smashy shield”.

Stomatopod nervous system adaptations

12-16 types of photoreceptors, ability to see polarized light, ability to rotate eyes independently in all directions, rapid image processing

Zoea

The first stage of a stomatopod larva. Notable for its shorter abdomen, its rostrum, and its dorsal spine.

Alima

The middle stage of a stomatopod larva. Notable for its longer abdomen, wide telson,longer antennae, and more developed raptorial appendages.

Erichthus

The final stage of a stomatopod larva. Notable for its more developed pleopods and the beginning of formation of uropods on the telson.

Astacidea

Decapod infraorder of true lobsters

Achelata

Decapod infraorder of spiny/slipper lobsters

Caridea

Decapod infraorder of true shrimp

Dendrobranchiata

Decapod suborder of prawns

Anomura

Decapod infraorder of hermit crabs, mole crabs, squat lobsters, and porcelain crabs.

Brachyura

Decapod infraorder of true crabs

Anomura traits

4th and/or 5th pair of pereopods are very small or highly modified, sometimes has an asymmetrical abdomen, has two distinct chela

Penaeida

Family of Dendrobranchiata (prawns)

Caridea traits

Brooders, 4 chelipeds, 2nd large abdominal region (pleura) overlaps the first and third

Penaeida traits

Broadcast spawners, 6 chelipeds, fairly uniform abdominal regions

Pereopods (10x)

(Caridea) Name and count of walking legs

Chelipeds

Clawed walking legs

Chelae

Claws found on walking legs

Maxillipeds (6x)

(Caridea) Name and count of legs for handling food

Petasma

(Caridea) External sex organ used for transferring sperm to a female’s thelycum

Rostrum

‘structural nose’, not for chemosensing but for defense and locomotion. Found in many decapods.

Pleura (6x)

(Caridea) Name and count of the flaps/shields covering the abdomen segments

Astacidea traits

Crusher and pincer claws (chela) on the chelipeds, short and smooth antennae, smooth carapace, typically solitary and live in colder water

Achelata traits

No chelipeds/chela, long, thick, spiny antennae, spined carapace, typically live in warmer water and often in groups

Chela

(Astacidea) Claws. Notably distinct between sides. One is the crusher and the other is the cutter/pincer.

Chelipeds

(Astacidea) legs on which chela are found, specialized first pair of pereopods.

Modified antennae

Two large, flat plats found on slipper lobstesr (Achelata) used for sensing the environment and digging up infaunal prey

Carapace

(Brachyura) protective shell

Teeth

(Brachyura) protective spines on the carapace

Pereopods

(Brachyura) walking legs

Chelipeds

(Brachyura) first set of pereopods

Chela

(Brahcyura) claw on the cheliped

Maxillipeds

(Brachyura) modified mouthparts that look like small, flat appendages. Pass food from chela to mouth.

Dactyl

(Brachyura) movable appendage on the chela; also the flattened appendage on the 5th pereopod of swimming crabs

Fiddler crabs

Uca genus of Brachyurans. Known for digging burrows with their small claw and attracting mates with their enormous claw. Filter the sand for POM and make big balls of filtered sand.

Spider crabs

Majoidea family of Brachyurans. Known for their long legs and habit of decorating themselves with sessile flora and fauna via the microscopic, sticky hairs that cover their exoskeleton. Use the decorations for food and/or crypsis. Includes the kelp crab and the sheep crab.

Swimming crabs

Portunidae family of Brachyurans. Known for the flattened dactyl on their fifth pereopod that allows them to swim. Includes green crabs and blue crabs.

Pea crabs

Pinnotheridae family of Brachyurans. Known for their tiny bodies and symbiotic/borderline parasitic relationship with the other invertebrates that they live on or in.

Shamefaced crabs

Calappidae family of Brachyurans. Known for the big, wide chelipeds that hide their face. They use these for defense, peeling mollusk tissue off of shells, digging, and filtering using the tiny hairs on their inner edges.

Cancer crabs

Cancridae family of Brachyurans. Known for their wide, many-toothed carapaces, predation of bivalves, and ecosystem engineering in soft sediment habitats via their aggressive excavations while hunting, exposing prey for other predators.

Zoea

First larval stage of brachyurans, anomurans, and carideans. Longer than it is wide (like amphipods) and often has a long rostrum/dorsal spine.

Megalopa

Second and final larval stage of brachyurans, anomurans, and carideans. Wider than it is long and more resembles the adult form.

Nauplius

First larval stage of a penaeid. Looks similar to that of a barnacle.

Protozoea

Second larval stage of a penaeid. Resembles that of a crab, but with less developed appendages.

Mysis

Third and final larval stage of a penaeid. Looks like a skinny, stretched-out mini shrimp with large eyes.

Astacidea larval stages

Larvae simply numbered stages 1-4 based on size. Look like less developed versions of adults.

Phyllosoma

First larval stage of Achelata. May stay in the plankton for 2 years. Sometimes hitchhikes on jellyfish like hyperiids do. Looks nothing like an adult.

Puerulus

Second and final larval stage of Achelata. Looks more like an adult now.

Anomura overview

variable carapace, 4/5th pleopod very small, 2 distinct chela/chelipeds, brooders with pseudo-external fertilization

Caridea overview

thin, laterally compressed carapace, relatively long pleopods posterior of pereopods (for swimming), 4 chelipeds/chela, brooders with pseudo-external fertilization

Dendrobranchia overview

thin/cylindrical carapace, relatively long pleopods posterior of pereopods (for swimming), 6 chelipeds/chela, external fertilization/broadcast spawning

Astacidea overview

cylindrical & heavy carapace, relatively short pleopods (for brooding), 2 distinct chelipeds/chela, brooders with pseudo-external fertilization