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Arthropods

North Pacific Krill

Author: Conor Graff

North Pacific Krill

By Conor Graff

Common Name: North Pacific Krill

Scientific Name: Euphausia pacifica

Size range: Between 16 and 25mm

Identifying features:

The North Pacific Krill is an ocean-based crustacean that can grow up to 25mm in length (this is a bit of a stretch, however; most average around 16mm). The word Euphausia is Latin for ‘brightly shining’, and indeed, these small invertebrates are noted for what appears to be a bioluminescent characteristic throughout their species. North Pacific Krill have large black eyes and large abdomens, and closer inspection reveals what appear to be gills formed around their legs, and scales on their antennae (these scales are very large and used to protect their antennae from damage).

Habitat:

The North Pacific Krill live, as their name would suggest, on the ocean of the same name. This stretch in habitat runs from the southernmost coasts of the US all the way to Japan, and due to their instincts to band into close ‘clouds’ of themselves, they can cover large areas as a quasi-community without having to move from one place to another. However, the accumulation of these krill is anything but organized; while krill can accumulate into these areas of themselves, they usually form these clusters in areas that would be the most hospitable. The gist is that these krill can be found in very large quantities around the stretch that is their habitat, while other areas are completely barren of krill.

Krill tend to dwell in the ocean’s “twilight zone” (the area between the ‘surface zone’ and the ‘bottom zone’), wherein they can stay out of the reach of most surface zone-dwelling predators. Krill swim to the surface zone during the night, where, under cover of darkness, they can find and feast on their food source, phytoplankton.

Food:

As mentioned above, krill feed mostly on phytoplankton (“plant plankton”), making them herbivorous. They feed via a complicated system in their mouthparts wherein the phytoplankton is filtered out of the water into the krill’s jaws.

Krill do not feed exclusively on phytoplankton; many are omnivores who feed of animal plankton (zooplankton). As mentioned before, Krill only come out at night to feed (all the better in escaping from hungry predators).

Predators:

Krill are perhaps the richest form of protein in the entire ocean, which may be why a certain surface-dwelling species (humans) have discovered and started harvesting them.

They tend to be a primary diet of baleen whales and a number of fish (notably salmon); however, humanity has begun to take an interest in these small creatures. In BC, krill are fished out in large quantities in order to feed aquariums, fish farms, and ourselves; Japan is also immensely interested. Those who have tried krill tend to say it has no taste when fresh and raw; however a bitter, powerful flavor is created from krill that is dried out in the sun or frozen.

Life Cycle:

Krill reproduction starts out in a familiar way to nearly every living creature: that with the release of sperm. Upon receiving the male Krill’s sperm, females store the semen in their bodies and fertilize them, and proceed to release the eggs that come out of this union. A female can release up to 20 000 eggs at a time in clusters with intervals in between. The eggs are laid several hundred meters in the twilight zone, where the larvae can safely hatch without being attacked by most day-dwelling creatures. Upon hatching, krill larvae feed of the nutrients given by the egg yolk. Larvae soon develop through many stages in order to finally reach their adulthood.

Spot Prawn

Spot Prawn

Authors: Aidan McReynolds and Zack Schmit

Common Names: Spot Prawn, Pacific Prawn

Scientific Name: Pandalus platyceros

Size Range: 15 to 22 cm in length at maturity

Identifying Features

Spot prawn are usually 15-22 cm in length when fully matured, making them larger than most shrimp. Two pairs of white spots on the abdomen identify them. They are of a pink or red-brown colour and have white lines on their carapace. They have an upturned rostrum. Their front two legs don’t have pincers but the second ones have small ones.

Habitat

Spot prawn are found in the intertidal region, to about 485m beneath the sea level. They range from the northern parts of the Alaskan coast, to southern California, and are also found along the Korea Strait, and in the Sea of Japan. Their main location along the seashore is on jagged rock faces and sheer underwater cliffs. They move to shallower waters at night to hunt.

Prey

Spot Prawn catch thier prey with their long legs and often hunt at night. In general, prawns and shrimp that are less than 1 cm in length eat plankton. When they are larger they will eat small shrimp, small shellfish and worms. They also eat dead crabs and fish. Prawns and shrimp are not very selective about what they eat.

Predators

Predators of Spot Prawns, during the early larval stage, are mostly jellyfish and plankton feeding fish such as herring. Animals that prey on adult Spot Prawns include fish (sculpin, salmon and flatfish), seagulls, and crabs. Defences that shrimp and prawns employ to avoid being eaten include fast swimming, quick withdrawal to underwater crevices, and colour camouflage. Adults Spot Prawn hide in eel grass to a avoid predators. Young hide under other algaes such as sea colander kelp.

Life

A female Spot Prawn will produce somewhere around 3,000 eggs, which will then become attached to tiny hairs on her bottom side, under her tail. Depending on the time of year, the eggs will be incubated for anywhere between 4 weeks and 3 months. The eggs will then hatch and begin to float around in the water, eating plankton. After they reach one centimetre in size, they will begin their life on the bottom of the sea. Baby Spot Prawn have a green tint to them. After one year, they will have matured fully into an adult. They then spend two years as male, and then undergo a process changing their sex to female. A male will change his sex early, if the male to female ratio is imbalanced.

Industry

With 2450 metric tonnes harvested annually Spot Prawns are BC’s largest shrimp/prawn industry. Fresh prawn are available starting in May for 6 to 8 weeks. According to the David Suzuki Foundation’s Seachoice Programme, the Vancouver Aquarium’s Ocean Wise programme and the Monterey Bay Aquarium’s Seafood Watch; the spot prawn industry is sustainable.

Photos by Aidan McReynolds and Zack Schmit

References

Barrows, Edward M. (2001). Animal behavior desk reference: a dictionary of animal behavior, ecology, and evolution (2nd ed.). Boca Raton, Fla: CRC Press. p. 317. ISBN 0-8493-2005-4. OCLC 299866547.

Butler, T. H.(1980) Shrimp of the Pacific Coast of Canada. Ottawa, Ontartio, k1A 0S9: Canadian Government Publishing Center.

Harbo, Rick M.(2011) Whelks to Whales. Coastal marine life of the pacific north west. Madeira Park, BC, V0N 2H0: Harbour publishing co, Ltd.

Jensen, Gregory C.(1957) Pacific Coast Crabs and Shrimps. Montery CA 93940. Sea Challengers

Lamb, Andy and Hanbe, Bernard P. (2005) Marine Life of the Pacific Northwest. a photographic encyclopedia of invertabrates, seaweeds and selected fishes. Madeira Park, BC, V0N 2H0: Harbour publishing co, Ltd.

February 28, 2017/0 Comments/by adam.james

Arthropods

Rockweed Isopod

Rockweed Isopod

Authors: Emma Hornell and Lilly Powell

Common Names: Rockweed Isopod, Pickle Bug, or Kelp Isopod

Scientific Name: Idotea wosnesenskii

Size Range: 4cm (1.6 inches) in Length

Identifying features

Rockweed Isopods are shrimp-like creatures with 7 pairs of clawed-tipped legs. The males are slightly larger than the females, are paler, and have thicker legs. The colour of individuals can vary from green, brown, to black. It is dependent on their diet and can help them camouflage into their environment. For example some individuals found in coralline algae are very dark red in colour while those living amongst Rockweed are a dark olive green. Their bodies are segmented and flattened from top-to-bottom.

Habitat

Rockweed Isopods can be found along the Pacific Coast from California to Alaska. They live in the intertidal zone and can be found under rocks or clinging to the holdfasts, stalks or blades of seaweed such as the Rockweed (Fucus gardneri). They are also sometimes found in mussel beds.

Prey

Rockweed Isopods are scavengers, surviving mainly on marine plants, algae and algal detritus, and occasionally the eggs of molluscs such as the Emarginate Dog Winkle (Nucella emarginata).

Predators

Rockweed Isopods have a myriad of different predators that likely include foraging shore birds and fish.

Behaviours

To protect itself from predators the Rockweed Isopod relies on camouflage and its ability to hold tightly to rocks and seaweed. Though some marine isopods are able to roll up into a small ball like their terrestrial relatives the Rockweed Isopod is not so flexible. The principally nocturnal creature, however, is a gifted swimmer, using paddle-like appendages on its abdomen to maneuver itself around.

Life cycles

The average lifespan of a Rockweed Isopod is three to four years.

Reproduction

Rockweed Isopods reproduce around spring when the male fertilizes the female. The female Isopod holds her young in body pockets while they develop for three to four weeks, finally hatching as miniature adults.

Fun Fact:

Idotea (Pentidotea) wosnesenskii was Named after Russian biologist Ilya G. Voznesenskii.

Original video by Aries

Video editing by Emma Hornell and Lilly Powell

References

Cowles, Dave. (2006). Idotea wosnessenskii. WWU: On Campus. Retrieved May 7th 2013 fromhttp://www.wallawalla.edu/academics/departments/biology/rosario/inverts/Arthropoda/Crustacea/Malacostraca/Eumalacostraca/Peracarida/Isopoda/Valvifera/Family-Idoteidae/Idotea_wosnessenskii.html

Houck, Becky; Fergusson-Kolmes, Linda; Kolmes, Steven; Lang, Terra. (n.d). Final Report on Intertidal Invertebrates in Tillamook Bay – A Report to the Tillamook Bay National Estuary Project. Department of Biology, University of Portland. Retrieved May 9th 2013 fromhttps://nrimp.dfw.state.or.us/web%20stores/data%20libraries/files/Watershed%20Councils/Watershed%20Councils_440_DOC_InvertebrateFaunaOfTillamookBay.pdf

Jamison, David. W. Kelp Isopod. Pugetsoundsealife.com. Retrieved May 7th 2013 fromhttp://www.pugetsoundsealife.com/puget_sound_sea_life/Kelp_Isopod.html

Pentidotea wosnesenskii. (2013, April 13). In Wikipedia, The Free Encyclopedia. Retrieved May 9th, 2013, from http://en.wikipedia.org/w/index.php?title=Pentidotea_wosnesenskii&oldid=550200397

Vancouver Sun. (May 2nd 2009). Urban critter: Rockweed isopod. canada.com | Join the discussion. Retrieved May 7th 2013 fromhttp://www.canada.com/vancouversun/news/westcoastnews/story.html?id=a16723b7-293d-4080-ab7b-671c4ddbc935

February 28, 2017/0 Comments/by adam.james

Arthropods

Pygmy Rock Crab

Pygmy Rock Crab

Author: Sam Mitchell-Joy

Scientific name: Cancer oregonensis, Glebocarcinus oregonensis

Common names: Pygmy Rock Crab, Hairy Cancer Crab, Oregon Cancer Crab

Size range: A Pygmy Rock Crab can grow up to 5cm (2 inches) across its carapace. The males are larger than the females by about a centimeter.

Identifying features: The Pygmy Rock Crab can be identified by its rounded shell with numerous spiny ridges and black tipped claws. Some larger and developing Pygmy Rock Crab have tubercles (rounded projections) that develop in patterns on their dorsum. Their legs are covered in small hairs called setae which are most easily identified under water. The dorsal surface and legs are usually a dull red but can be found in lighter colors such as browns and whites; the underside is most commonly white.

Habitat: The pygmy rock crab lives intertidal to 436 meters deep. They are often found habituating crevices, under rocks, and the holes of dead barnacles. Often a male and a female will share a hole or crevice. Pygmy Rock Crab can be found up the Pacific coast of North America, ranging between southern Alaska and southern California.

Prey: The Pygmy Rock Crab is a nocturnal feeder of small barnacles, small snails, molluscs, worms, and algae.

Predators: The Pygmy Rock Crab is preyed upon by River Otters, Pacific Cod, and its relative the Red Rock Crab (Cancer productus). They hunt nocturnally to avoid crepuscular predators and they may use their rounded shell to block the entrance to protect themselves from predators who aim to grab them from their hole. When caught outside its hole, the crab will roll itself into a ball by tucking its legs in to avoid danger. They will often be found in the empty shell of the Giant Acorn Barnacle (Balanus nubilus) effectively blocking the hole with their carapace.

Life Cycle: The breeding season of the Pygmy Rock Crab is in the summer months, and takes place after the female has molted. A male will often carry a female around who is going to molt in anticipation of the breeding process. A single male is sometimes found with several females during the summer breeding months. Females bearing eggs are found during the months between November and May.

Photos by Sam Mitchell-Joy

References:

Adams, Mary Jo (December 5, 2005). “Cancer oregonensis (Pygmy rock crab)”. Intertidal Organisms EZ-ID Guides. Washington State University. Extension – Island County. Retrieved May 20, 2012 fromhttp://www.beachwatchers.wsu.edu/ezidweb/animals/Canceroregonensis.htm

Dave Cowles (2005). “Glebocarcinus oregonensis (Dana), Schweitzer and Feldmann, 2000)”. Walla Walla University. Retrieved May 20, 2012 fromhttp://www.wallawalla.edu/academics/departments/biology/rosario/inverts/Arthropoda/Crustacea/Malacostraca/Eumalacostraca/Eucarida/Decapoda/Brachyura/Family_Cancridae/Cancer_oregonensis.html

Jamieson, David (2008). Pigmy Rock Crab, Puget Sound Sea Life [www.pugetsoundsealife.com]. Retrieved May 20, 2012.http://www.pugetsoundsealife.com/puget_sound_sea_life/Pigmy_Rock_Crab.html

Klinkenberg, Brian. (Editor) 2010. E-Fauna BC: Electronic Atlas of the Fauna of British Columbia[www.efauna.bc.ca]. Lab for Advanced Spatial Analysis, Department of Geography, University of British Columbia, Vancouver. Retrieved May 20, 2012 from http://linnet.geog.ubc.ca/efauna/Atlas/Atlas.aspx?sciname=Glebocarcinus%20oregonensis Jma

February 28, 2017/0 Comments/by adam.james

Arthropods

Puget Sound King Crab

Puget Sound King Crab

By Sarah Roberts and Julia Mitchell

Common name: Puget Sound King Crab

Scientific name: Lopholithodes mandtii Brandt, 1849

Size range: up to 30 cm across carapace (11.8 inches)

Identifying features: Puget Sound King Crabs are one of the largest crabs on the West Coast, growing up to 30 cm across the carapace. This crab’s main distinguishing features are its box-like body which can resemble a mini army tank, and its brilliant coloring. Juveniles are a bright orange colour, with red and yellow parts. The adults are redder, with yellow, orange, brown, purple, and even blue markings on its body, and are covered in bumps and wart-like tubercles. The carapace is triangular shaped, but rounded at the bottom, and it does not cover its legs which are as wide as the carapace. A differentiating feature from other crabs is that the Puget Sound King Crab has only 6 legs visible, because 2 are hidden in the carapace, whereas other crabs have all 8 legs visible. It also has 2 chelae (claws) that are cuplike and lined with teeth and bristle-like hairs.

Habitat: Puget Sound King Crabs are found in the subtidal areas up to 137 meters deep. They are most often found in rocky areas with strong currents. They like to cling to vertical walls, and perch on small ledges. Juveniles prefer to be under rocks during low tide. They are found from Southern Alaska to Central California. Little is know about the size of the population, and therefore they are a fully protected species by the Washington Department of Fish and Wildlife.

Food: The diet of these crabs is mainly sea urchins, barnacles, starfish, especially sunflower stars and brittle stars, sea anemones, and other echinoderms. They capture their prey with their claws, and each claw has a specific use for eating their food. The left claw is used to crush the animal, and then the right claw is for cutting it and finer handling of the food.

Predators: To ward off predators, the Puget Sound King Crab has a unique shape which allows it to curl up into an ‘army tank’-like form. The mature crabs dark coloring and bumpy texture help it blend in with its surroundings on the ocean floor, while the Juveniles vibrant orange hue helps it blend in with surrounding coral and sea cucumbers. The crab has large, strong claws with molar-like teeth meant for crushing, perfect for protecting itself with.

Life cycle: In early winter the Puget Sound king crabs move from deep waters to shallower waters to molt and mate. They can only mate once the female crab has molted. After she has molted and mated the female returns to deeper waters and carries the 186,000 eggs with her for a year. Meanwhile, the male and the juveniles remain in shallow waters and will molt during the summer months, and then they will return in autumn. During spring, the females will spend 12-14 days hatching her eggs, and the larvae will spend 2 months in plankton beds before settling at the bottom where they spend the rest of their lives. It takes 7 years for a Puget Sound King Crab to mature, and it remains unknown to how long their life span is.

Photography by D. Young

References:

Cowles, D. (2004). Lopholithodes mandtii (Brandt, 1849). Key to invertebrates found at or near the Walla Walla University Marine Station (Rosario) Fidalgo Island, Anacortes, WA. Retrieved June 8, 2010 fromhttp://www.wallawalla.edu/academics/departments/biology/rosario/inverts/Arthropoda/Crustacea/Malacostraca/Eumalacostraca/Eucarida/Decapoda/Anomura/Family_Lithodidae/Lopholithodes_mandtii.html

February 7, 2009. Lopholithodes mandtii (Puget Sound King Crab). Zipcode Zoo. Retrieved June 8, 2010 from http://zipcodezoo.com/Animals/L/Lopholithodes_mandtii/

Rawlings, J. (December 5, 2008). Emerald Sea Royalty- Puget Sound King Crab. Newsvine. Retrieved June 8, 2010 from http://john-rawlings.newsvine.com/_news/2008/12/05/2182487-emerald-sea-royalty-puget-sound-king-crab

February 28, 2017/0 Comments/by adam.james

Arthropods

European Green Crab

European Green Crab

Authors: Lilly Powell and Emma Hornell

Common name: European Green Crab

Scientific name: Carcinus maenas

Size Range:

The European Green Crab is commonly between 60mm long and 90mm wide but has been noted to grow up to 101mm wide in non-native areas such as British Columbia.

Identifying Features:

The European green crab is not always pure green, its dorsal shell being mottled dark green to brown with yellow patches on the ventral surface. However, the crab’s shell may change to orange or red during the molting cycle. Some of the most identifiable features of the Carcinus maenas are the array of five spines on either side of the eyes on the front end of the carapace, and three rounded bumps between its eyes.

Habitat:

European Green Crabs are an invasive alien species that originated in the Baltic Sea, in the Atlantic Ocean off the coast of Western Europe and Northern Africa. It is believed they first came to North America in the 1800’s in the dry ballasts or ballast water of large ships. They first became established on the west coast of North America in Central California near California. Though most invasive species in British Columbia are thought to come in ballast water of visiting ships it is thought the Green Crab most likely arrived as larvae that drifted on northern currents from the central California area. They can now be found from Central California all the way up to Southern British Columbia. Green Crabs are very adaptive and can tolerate a wide range of salinity (4-54 ppt) and temperatures (0-33°C). Green Crabs can be found in a variety of habitats in the intertidal zone such as: protected rocky shores, cobble beaches, sand flats, and tidal marshes.

Prey:

The European Green Crab will feed on anything it can get its claws on, its most common prey being: clams, oysters, mussels, and other small native crabs. The crab is extremely dexterous, and has many ways to open the shellfish it eats.

Known Predators:

In its native habitat Carcinus maenas’ predators include the Conger Eel, the Trigla Lucerna, Bass, and the Fivebeard Rockling. The crab’s defenses include its ability to rotate its claws over its back to defend against predators coming from behind, and being able to live outside of water in the sun for up to a week.

Reproduction & Life Cycle:

European Green Crabs typically mate during the summer, when the female crab has just molted and is vulnerable. During this time, the male green crab guards the female by pairing with her in a “pre-molt cradling”, protecting her from other males and predators. The egg sac appears a few months after mating and is carried for several months. The eggs then hatch into free-swimming larvae that stay in the water for 17 to 80 days before settling to the bottom as tiny crabs. The European green crab lives for up to five years and reaches sexual maturity at two or three years.

Impacts:

Known as The Most Invasive Crab in the World, the European Green Crab is a huge threat to our waters. Its floating larval stage contributes largely to its rapid migration and its feeding habits and environmental tolerance enables it to adapt to many places. Marine biologists believe the crab will also wipe out many commercial fish after already being discovered as a leading natural contributor to the dramatic declines in soft-shell clam fishery (aided by its ability to consume over 40 small clams a day). Also a threat to vital Eel-Grass habitats for many small creatures, the crab will snap the plants at their base, effectively preventing the grass from growing and reproducing.

Orange Hermit Crab

Orange Hermit Crab

Author: Rachel Walker

Scientific Name: Elassochirus gilli

Common Name: Orange Hermit Crab

Size Range: On average, the male orange hermit crab grows to 20.4mm in length.

Identifying Features: The Orange Hermit Crab is most distinctly recognizable by its vibrant orange, almost red colour. It has a smooth body with no visible hairs or spines, and stout eyestalks with a non-inflated cornea. The orange hermit has two sets of legs that come out of the shell that they use for walking, and two sets on the inside for moving its body in and out of its shell. Their legs are compressed to resist bending under water, and are a bright blue colour at the upper leg. Their left hand is a wide fixed finger while their right is a much larger, expanded, flattened claw which they use to cover the opening of their shell while they are inside for protection, and for grabbing and fighting. The shells of orange hermits tend to be whitish or grey with brown and pale yellow blotches or streaks, though they find new shells when they grow out of them. Being such friendly creatures though, they will never displace another creature for its shell.

Habitat: The orange hermit crab lives in intertidal waters to 200m (660ft) in the Northwestern Pacific Ocean along the coast of Northern Alaska, down to Northern Washington. They are most commonly found in bedrock or rocky areas with a fast-moving current and thrive in a suitable habitat.

Prey: Hermits are not fussy eaters; they feed on decaying wood, leaf litter, grasses, plants, items by the shore, and even fallen fruit if available. They locate their food by either smelling, or seeing other crabs eating. These orange crustaceans feed by creating a current with appendages near the head, or scavenge material that drifts by.

Predator: Hermit crabs are preyed upon by a variety of animals. Under water, they must be mindful of many fish such as clownfish, triggerfish, porcupinefish, pufferfish, and the California sheephead, which have powerful jaws for breaking shells, or beak-like mouths for ripping shells apart. Other aquatic animals that eat hermits are octopuses, which coat them in saliva and remove it from its shell or pry the shell apart, and bigger crabs, such as the blue crab, which use their large claws to crush their shells or pull them out. On land, if a hermit crab is washed up, birds often fly by and pick them up! When threatened, hermits scuttle away or burrow in an attempt to hide. For protection, they have their shells, regeneration abilities to grow back appendages, and possibly a symbiotic relationship with anemones, as many hermit crabs are known to have this relationship, but it is uncertain if the orange hermit has this relation or not, though it is likely. The anemones attach onto the hermits shell and eat food left behind by the crab, while defending it by stinging predators with their tentacles.

Life Cycle: At 2 years old, hermit crabs are fully grown and ready to mate. To mate, both crabs must partially leave their shell, leaving them exposed to predators. Once the eggs are fertilized, the female must carry them in her shell for a month, keeping them safe and moist. As the eggs mature, they turn from dark red to grey as they consume yolk. When she is ready to lay her eggs, the mother waits until low tide, travels into the ocean, and releases hundreds of eggs in rocks and crevices. As soon as salt water washes over them, the eggs hatch. Shrimp-like larvae called zoeae immediately then swim to masses of plankton where they are venerable to predators. From there they are carried by currents and dispersed. They are in the zoeae stage for 6-8 weeks before maturing to the larval stage called glaucothe. During this period they molt several times in 1-2 weeks, looking more and more mature with each molt, looking like a cross between a crab and a lobster. After a couple months, the hermit will find a shell, crawl inside, and make its way to land where it will spend the remainder of its life, changing shells as it grows. At 2 years, the hermit crab will be fully grown and is able to mate and continue the cycle, and live for another 10 years as a happy hermit.

Photograph by William Leonard

Barnacle Larva – Nauplius Larva

Barnacle Larva – Nauplius Larva

Author: Alondra

The nauplius larva is the first swimming larval stage of a barnacle. After this stage it changes into a cyprid larval stage and then anchors itself onto a substrate as an adult barnacle.

February 19, 2013 Plankton Tow – Cadboro Bay