SubPhylum Crustacea Class Malacostraca - crabs, shrimps, lobsters

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1 SubPhylum Crustacea Class Malacostraca - crabs, shrimps, lobsters
Class Maxillopoda - ostracods, barnacles, copepods Class Branchiopoda - brine shrimp, tadpole shrimp Class Remipedia - small cave-dwellers; basal lineage Class Cephalocarida - small benthic detritivores; basal

2 SuperOrder Peracarida
Class Malacostraca SuperOrder Peracarida - carapace reduced in size - unique endites called oostegites (brood pouch, or marsupium) - direct development, which helped colonize land: bypass a planktonic larval stage, mother broods young & releases fully developed juveniles Order Mysida (opossum shrimp) Order Isopoda (isopods)  made it onto land Order Amphipoda (amphipods)

3 SuperOrder Peracarida Order Mysida (opposum shrimp)
Class Malacostraca SuperOrder Peracarida Order Mysida (opposum shrimp) - well developed carapace covering head+thorax segments - pelagic, intertidal, or burrowing - often form benthic “swarms,” which are small clouds of tiny shrimp that hide among urchin spines for protection brood pouch where young develop

4 SuperOrder Peracarida Order Isopoda >10,000 species
Class Malacostraca SuperOrder Peracarida Order Isopoda >10,000 species - no carapace: you can see each segment from above - one lineage successfully colonized dry land: the pill bugs - pereopods are very structurally variable - pleopods used in gas exchange Cirolana

5 kelp isopod rock louse

6 SuperOrder Peracarida Order Amphipoda 8,000 species
Class Malacostraca SuperOrder Peracarida Order Amphipoda 8,000 species - no carapace - includes semi-terrestrial “beach hoppers” - thoracic gills are epipods, extensions of pereopods

7 Decapod Larvae Decapods typically brood their larvae to a well developed, large-eyed zoea larva capable of fast swimming and active behaviors, which can help larvae migrate in & out of estuaries After several molts, the final megalopa larva is produced, which looks very much like the adult - except in crabs, the abdomen is not yet tucked under the thorax stomatopod (mantis shrimp) megalopa crab zoea

8 SubPhylum Crustacea Class Malacostraca - crabs, shrimps, lobsters
Class Maxillopoda - ostracods, barnacles, copepods Class Branchiopoda - brine shrimp, tadpole shrimp Class Remipedia - small cave-dwellers; basal lineage Class Cephalocarida - small benthic detritivores; basal

9 barnacles, copepods, ostracods
Class Maxillopoda 26,000 spp. barnacles, copepods, ostracods Head (5 segments) Thorax (6) Abdomen (4) - usually biramous limbs; no abdominal appendages - mostly small; reduced abdomen, missing some legs Subclasses: Thecostraca (barnacles) Copepoda Ostracoda free-living (acorn, gooseneck) parasitic on crustaceans

10 Class Maxillopoda: SubClass Thecostraca
Free-living barnacles Parasitic Rhizocephalans - hermaphrodites - separate sexes - carapace produces shell - carapace lost - suspension feeders - endoparasites w/ interna and externa Cirri Scutum Tergum Capitulum Peduncle Rootlets of ramifying body Externa

11 - in adult barnacles, the appendages on the thorax (= thoracic
legs, or cirri) are similar in appearance to tentacles of filter-feeding worms and crinoids (to come later) - used to filter feed: scutum and tergum plates open in response to water current, cirri extended up into water, then rapidly retracted inside shell over and over again

12 Nauplius Larval Stage Naupliar eye Antennule Antenna Mandible
antennules, antennae, mandibles; no segmentation; single eye - successive molts: remaining head, thoracic appendages

13 Cyprid Larvae Unique feature of barnacles: non-feeding cyprid larval stage which follows the nauplius stage - has a bivalved shell, and swims using antennae - in free-living barnacles, cyprid glues its head onto the first suitable hard surface it encounters Cyprid attaching, cementing itself head-first to substrate become cirri of adult

14 Class Maxillopoda: SubClass Copepoda - 8,500 spp.
Naupliar eye - cephalic “shield” - keep single naupliar eye - primary consumer of phytoplankton - tiny; swim by flicking antennae Antenna Antennule articulation point (attachment of thorax to abdomen) Ovisac (clump of embryos) Caudal rami

15 Class Maxillopoda: SubClass Copepoda - 8,500 spp.
In males, 1st antennae and 5th thorax limb may be specially modified for “mate guarding” behaviors - males locate, grab and ride around holding a virgin female before her terminal (final) molt - this way, they ensure they are the male who will fertilize her eggs when she molts, and is then ready to mate

16 Class Maxillopoda: SubClass Ostracoda - 6,600 spp.
- bivalved carapace (how many independent origins of a bivalved shell have we seen now??..) - reduced segmentation; body not split into thorax + abdomen - 5 head appendages thoracic appendages, including male copulatory limb-- fewest limbs of any crustacean - many are bioluminescent, using light flashes in complex mating rituals - swim using antennae

17 SubPhylum Crustacea Class Malacostraca - Crabs, shrimps, lobsters
Class Maxillopoda - Ostracods, barnacles, copepods Class Branchiopoda - Brine shrimp, tadpole shrimp Class Remipedia - small cave-dwellers; basal lineage Class Cephalocarida - small benthic detritivores; basal

18 Class Branchiopoda carapace no carapace telson Artemia, brine shrimp
Notostracans: tadpole shrimp Anostracans: fairy shrimp carapace no carapace telson Artemia, brine shrimp caudal ramus often inhabit freshwater vernal pools (temporary)

19 Crustaceans on Land 1. 2. Sow bugs (terrestrial isopods) are most
successful group - direct development cut ties to the sea Land crabs must still return to the ocean to spawn 3. Insects – molecular evidence indicates the most successful animal lineage evolved from a crustacean ancestor

20 (1) Insects are nested within the “Crustacea”, which is therefore
a paraphyletic group! New name, “Pancrustacea”, refers to crustaceans + insects Analysis of 62 genes redefined arthropod relationships Regier et al. 2010, Nature

21 (1) Insects are nested within the “Crustacea”, which is therefore
a paraphyletic group! 2) Maxillopoda not a true group - barnacles, copepods & ostracods do not form a clade - despite sharing the same “formula” for body segments, these are all unrelated groups Regier et al. 2010, Nature

22 Insects are nested within the “crustacea”, which is therefore
a paraphyletic group! 2) Maxillopoda not a true group 2a – barnacles are sister to Malacostraca (crabs, etc) 2b – copepods are sister to (Malacostraca + barnacles) 2c – ostracods are basal to rest of Crustacea Regier et al. 2010, Nature

23 Ecdysozoa Onychophorans Arthropods Tardigrades Priapulids Kinorhynchs
- clade Ecdysozoa was named in 1997 from an analysis of 18S ribosomal RNA gene - members all molt to grow, controlled by hormone ecdysone Tardigrades Priapulids Kinorhynchs Loriciferans Nematodes Nematomorphs

24 Phylum Tardigrada - “water bears” 3 Orders, 10 Families
~ 800 species microscopic 8-legged “water bears” from semi-aquatic habitats prone to drying out (e.g. moss) display extreme cryptobiosis when environments dry out: the ability to enter a state of suspended animation, with no metabolism or apparent ageing, until conditions improve - 4 pairs of unjointed legs - uncalcified cuticle lines parts of gut main cavity = hemocoel; no gills, respire across wet body wall

25 Cryptobiosis in Tardigrades
During environmental stress, legs are pulled and body coated in a double-walled cuticular envelope, forming a cyst Then, a single-walled tun state develops, where metabolism is undetectable and individuals can survive long periods of dessication (= dryness) Tuns have survived… - up to 10 years without water - complete vacuum, long periods with no oxygen - temperatures near absolute zero: 8 hr at -272°C !! - toxic liquids (ether, 100% alcohol) Allows tardigrades to persist in an unstable ecological niche

26 mostly feed on plants, algae stylet used to punch holes in plants or algae; then tardigrade sucks out cytoplsm convergent evolution: very similar to the single tooth and method of feeding in sacoglossan sea slugs (my group, the herbivores)

27 Ecdysozoa Onychophorans Arthropods clade Cycloneuralia Tardigrades
– brain forms a loop around esophagus – anterior end = introvert, which can be withdrawn into body Tardigrades Cycloneuralia Priapulids Kinorhynchs Loriciferans Nematodes Nematomorphs

28 Ecdysozoa Onychophorans Arthropods clade Cephalorhyncha Tardigrades
– spiny collar of scalids around the introvert Tardigrades Cephalorhyncha Priapulids Kinorhynchs Loriciferans Nematodes Nematomorphs

29 Phylum Nematoda ~25,000 species
- body round in cross-section, but no circular muscles; longitudinal muscles let them thrash around to move - covered in cuticle, shed in 4 molts during juvenile growth  allows survival in hostile environments - extensions of muscles called muscle arms branch out to contact neurons, instead of other way ‘round like most animals - unique excretory system featuring renette cells; no circulatory structures Includes model organism for developmental biology, C. elegans

30 Phylum Nematoda Ecological importance:
- tremendously abundant decomposers - 200 per ml of coastal mud - 90,000 per rotting apple - 9 billion per acre of soil Medical importance: - cuticle allows them to resist immune system, function as endoparasites (endo = living inside the host’s body) - parasitic forms cause diseases including river blindness, elephantiasis, trichinosis

31 Nematomorphs – “horsehair worms”
~320 species - long thin body encased in well-developed cuticle - over 1 meter long, less than 1 mm wide - no apparent segmentation - all growth accomplished by larvae, which are parasites in arthropod hosts - gut, but no mouth; nutrients are absorbed from insect host across body wall, taken up by gut tissue

32 Priapulids 18 species - benthic marine “worms”
- introvert with hooked spines - complete gut, protonephridia for excretion - no circulatory system - thin cuticle surrounds body - loricate larva has special cuticle that’s shed at metamorphosis Introvert Trunk rings Caudal appendages

33 Phylum Kinorhyncha ~ 180 species
- all marine; interstitial = live between grains of mud or sand - body with 13 segments: head, neck, and 11-segment trunk - no cilia; crawl by extending head, locking spines in place - head = introvert; can retract into neck - ring of backward-facing spines (scalids) used to lock body in place when crawling  convergent evolution with how annelids use chetae to dig - well-developed cuticle - no larval stage!

34 Phylum Kinorhyncha

35 Phylum Loricifera ~ 100 species - all marine; only discovered in 1983!
- body tiny (< 0.5 mm) but complex (>10,000 cells) - head with piercing stylets around mouth - head, neck + thorax retract into abdomen - 9 rings of spines called scalids - complete gut, but no circulatory system or nephridia

36 Phylum Loricifera Head Thorax Abdomen