Category Archives: crustaceans

Friday Fellow: Stonewort Seed Shrimp

by Piter Kehoma Boll

It’s time to talk about an ostracode, or seed shrimp, again and, as usual, this is a difficult time due to the little information easily accessible regarding any particular species of this group. But there is, indeed, one that is considerably well studied. Being one of the most common ostracodes in North America and Eurasia, its scientific name is Cypridopsis vidua, to which I coined the common name “stonewort seed shrimp”.

The stonewort seed shrimp is a freshwater crustacean with the typical ostracode appearance, looking like a tiny bivalve measuring about 0.5 mm in length. Its valves have a distinctive light and dark pattern.

A stonewort seed shrimp with a closed shell. Credits to Markus Lindholm, Anders Hobæk/Norsk institutt for vassforsking.*

A relatively mobile species, the stonewort seed shrimp lives at the bottom of water bodies, over the sediment, and is common in areas that are densely vegetated by stoneworts (genus Chara). This association with stoneworts gives the stonewort seed shrimp both protection from predators, which are mostly fish, and a good food source.

The main food of the stonewort seed shrimp are microscopic algae that grow on the stems of stoneworts. While foraging, the stonewort seed shrimp swims from one stonewort stem to another using its first pair of antennae and clings on the stems using the second pair of antennae and the first pair of thoracic legs. Once realocated, it starts to scrape the microscopic algae using its mandibles.

The body of a stonewort seed shrimp as seen when one of the valves (the left one here) is removed. Credits to Paulo Corgosinho.**

The stonewort seed shrimp is one more of those species in which males do not exist, not even in small quantities. During the warm months of summer, females produce the so-called subitaneous eggs, which develop immediately into new females. However, when winter is approaching, they produce another type of eggs, the so-called diapausing eggs, which remain dormant in the substrate during winter. The adult animals all die during this season and, when spring arrives, a new population appears from the hatching eggs. Since not all eggs hatch in the spring, some of them may remain in the substrate for years before hatching, which usually increases the genetic diversity every year, as it not only depends of the daughters of the last generation.

But how does genetic diversity appear if there are no males and, as a result, the daughters are always clones of the mothers? This mystery is not yet fully solved. Genetic recombination during parthenogenesis, by exchanging alleles between chromosomes, does not seem to be very common. It is possible that different populations are genetically different and that they colonize new areas very often, mixing with each other. Since males are known in closely related species, it is still possible that, some day, we will find, somewhere, some hidden males of the stonewort seed shrimp. It is also possible that, somehow, males went all extinct in the recent past, like in the last glaciation, for example. If so, only time can tell what is the destiny of the stonewort seed shrimp.

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More Ostracods:

Friday Fellow: Sharp-Toothed Venus Seed Shrimp (on 22 June 2018)

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References:

Cywinska A, Hebert PDN (2002) Origins of clonal diversity in the hypervariable asexual ostracode Cypridopsis vidua. Journal of Evolutionary Biology 15: 134–145. doi: 10.1046/j.1420-9101.2002.00362.x

Roca JR, Baltanas A, Uiblein F (1993) Adaptive responses in Cypridopsis vidua (Crustacea: Ostracoda) to food and shelter offered by a macrophyte (Chara fragilis). Hydrobiologia 262: 121–131.

Uiblein F, Roca JP, Danielpool DL (1994) Experimental observations on the behavior of the ostracode Cypridopsis vidua. Internationale Vereinigung für Theoretische und Angewandte Limnologie: Verhandlungen 25: 2418–2420.

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*Creative Commons License This work is licensed under a Creative Commons Attribution 3.0 Unported License.

**Creative Commons License This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

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Friday Fellow: Common Goose Barnacle

by Piter Kehoma Boll

The open surface of the oceans may at first look like a large lifeless sheet. However, if you look closer, you’ll see that there is much more life there than you could imagine. And it does not only include the microscopic plankton that floats in the water column, but also large organisms that dwell right at the boundary between the water and the air. These creatures are called the neuston and come in several shapes and one of them is Lepas anserifera, or the common goose barnacle.

Several common goose barnacles found growing on a cuttlebone in India’s west coast. Their modified legs (cirri) are out looking for food. Photo by Abhishek Jamalabad.*

The common goose barnacle is found in tropical and subtropical waters all around the world. It belongs to the subclass Cirripedia, a peculiar group of crustaceans commonly known as barnacles. They live attached to the substrate and are hemaphrodites, both features that are uncommon among arthropods. Within the barnacles, the common goose barnacle belongs to the order Pedunculata, or goose barnacles, which are characterized by the presence of a stalk that attaches them to the substrate.

Common goose barnacles in Taiwan. A younger specimen is seen growing on a larger one. Photo by Liu JimFood.*

The substrate chosen by the common goose barnacle is almost exclusively floating material. This material, which includes sea weeds and all sort of debris, such as pieces of wood, coconuts or animal carcasses, rarely remains floating for a long time, either because its decay makes it sink or fall apart or because it ends up on the shore. Thus, the goose barnacle has to find a way to complete its life cycle very quickly, and that is what it does.

Common goose barnacles growing on an apple that must have floated for some time and ended up at the shore in the state of Bahia, Brazil. Photo by iNaturalist user kuroshio.**
Common goose barnacles growing on a light bulb washed ashore in Palau Pinang, Malaysia. Photo by Al Kordesch.

Goose barnacles start their lives as a planktonic one-eyed larva that, after five stages, develops into another larval form known as cyprid. The cyprid’s only purpose is to find a suitable surface to live and, once it finds it, it secretes a glycoproteinaceous substance that attaches it to the substrate by the head. It then develops into the adult animal and secretes a series of calcified plates that surrounds its body. The adults use their feathery legs (cirri) to capture food, mostly plankton, and carry it inside their shell.

Common goose barnacles growing on a brush washed ashore in New Jersey, USA. Photo by Stan Rullman.**

Due to human activities, the amount of floating material on the ocean surfaces increased greatly. Thus, the number of available substrates for the goose barnacle to grow also increased, and so likely did its population. Unfortunately, the human-generated floating material also includes a lot of small plastic particles, and goose barnacles frequently ingest them together with food. Although the harm caused by ingesting plastic particles has not been assessed yet, they certainly do not improve the barnacle’s health.

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Reference:

Goldstein MC, Goodwin DS (2013) Gooseneck barnacles (Lepas spp.) ingest microplastic debris in the North Pacific Subtropical Gyre. PeerJ 1: e184. doi: 10.7717/peerj.184

Inatsuchi A, Yamato S, Yusa Y (2010) Effects of temperature and food availability on growth and reproduction in the neustonic pedunculate barnacle Lepas anserifera. Marine Biology 157(4): 899–905. doi: 10.1007/s00227-009-1373-0

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*Creative Commons License This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

**Creative Commons License This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

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Friday Fellow: Peacock Mantis Shrimp

by Piter Kehoma Boll

Invertebrates are much less likely to become popular creatures than vertebrates, but every now and then there is an exception, and one of them is certainly Odontodactylus scyllarus, the peacock mantis shrimp.

Peacock Mantis Shrimp at Guinjata Bay, Mozambique. Photo by Peter Southwood.*

Found in the Indo-Pacific region, from the east coast of Africa to Guam, the peacock mantis shrimp is a large and colorful species of the crustacean order Stomatopoda, popularly known as mantis shrimps. Measuring up to 18 cm in length, their body is mainly green with some large black spots with a white contour one the cephalothorax. The legs are reddish orange and the region around the eyes has a light blue shade. Due to this beautiful appearance, the peacock mantis shrimp has become a popular animal to be raised in aquariums.

Frontal view of a peaock mantis shrimp in the Andaman Sea, Thailand. You can see the club-like appendages used to break the shell of prey. Photo by Silke Baron.**

Mantis shrimps are predators and the peacok mantis shrimp is not an exception. It feeds mainly on shelled mollusks, such as gastropods and bivalves, and crustaceans. To break the strong carapace of its prey, it smashes them with a powerful strike using its club-like second pair of thoracic appendages. This strong attack, caused by a complex mechanism in the appendage, is so strong that it easily breaks the shell of the prey. In aquariums, this can be problematic, as they sometimes break the aquarium’s wall. More than only striking the prey with incredible force, the attack of the mantis shrimp generates a sudden region of low pressure between the shell and the appendage when the appendage is quickly retracted. This phenomenon, called cavitation, generates a bubble of gas that quickly collapses and generates large amounts of energy in the form of heat, light and sound and creates a second impact on the prey.

Female peacock mantis shrimp carrying eggs in Indonesia. You can also see the eyes with two hemispheres separates by a band of larger ommatidia arranged in 6 lines. Photo by Terence Zahner.***

The peacock mantis shrimp has also a magnificent vision system. Its compound eyes are divided into an upper and a lower hemisphere which are separated by a band of six lines of enlarged ommatidia (the small eyes that form the compound eye). This three regions of the eye are used to detect different wavelengths, including UV light, and even include special cells that convert unpolarized light into polarized light or filter circular polarized light, allowing the mantis shrimp to detect light in different ways from different parts of the eye. This complex system is being studied for the development of optical devices to store and read information.

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References:

Jen Y-J, Lakhtakia A, Yu C-W, Lin C-F, Lin M-J, Wang S-H, Lai JR (2011) Biologically inspired achromatic waveplates for visible light. Nature Communications 2: 363. doi: 10.1038/ncomms1358

Kleinlogel S, Marshall NJ (2009) Ultraviolet polarisation sensitivity in the stomatopod crustacean Odontodactylus scyllarus. Journal of Comparative Physiology A 195(12): 1153–1162. doi: 10.1007/s00359-009-0491-y

Land MF, Marshall JN, Brownless D, Cronin TW (1990) The eye-movements of the mantis shrimp Odontodactylus scyllarus (Crustacea: Stompatopoda). Journal of Comparative Physiology A 167(2): 155–166. doi: 10.1007/BF00188107

Marshall J, Cronin TW, Shashar N, Land M (1999) Behavioural evidence for polarisation vision in stomatopods reveals a potential channel for communication. Current Biology 9(14): 755–758. doi: 10.1016/S0960-9822(99)80336-4

Patek SN, Caldwell RL (2005) Extreme impact and cavitation forces of a biological hammer: strike forces of the peacock mantis shrimp Odontodactylus scyllarus. The Journal of Experimental Biology 208: 3655–3664. doi: 10.1242/jeb.01831

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*Creative Commons License This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.

**Creative Commons License This work is licensed under a Creative Commons Attribution 2.0 Generic License.

***Creative Commons License This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

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