https://cdn.shopify.com/s/files/1/0181/4635/products/GLPblue2_1024x1024.jpg?v=1414760881Zooplankton of the Great Lakes

Brachionus

Site created by:  Benjamin Coyle

Project home page

Classification:

Kingdom: Animalia

    Phylum: Rotifera

       Class: Eurotatoria (Sub Class: Monogononta) 

            Super order: Pseudotrocha

                       Order: Ploimida

                                Family: Brachionidae

                                        Genus: Brachionus

                                              Species: 24 child taxa (sub/forms)

Distribution and Habitat:

Brachionus species are highly plastic and can survive highly variable environmental changes both seasonally and annually. Tolerant of cold, salinity, changes in ionic composition and desiccation, species under the genus Brachionus have a cosmopolitan distribution as they have been found on all continents (Fontaneto et. al, 2006; Alcantara-Rodriguez et.al, 2012).  Species of brachionous such as B. plicatilis (and others) can be considered euryhaline and tolerate wide salinity fluctuations by means of osmoregulation (Lowe et. al, 2005).

Anatomy:

Brachionous spp retain general rotifer body plans. Brachionous are loricate, footed rotifers. At the posterior end of the body is an opening in the lorica for a foot. This foot is divided, and sometimes coiled. Some spp have a foot that is completely retractile where others are not.

Figure 1: Generalized Brachionous anatomy

 


                               

Species Morphology:

Morphologies of Brachionous spp are highly contrasting. Species may have lorica with distinct spines whereas some spines are no longer present. Within a single species there can exist two different morphotypes (Figure 2). B. plicatilis can be found in the small (s) morph or the large (L). They differ in their lorica length: 130 to 340 µm (average 239 µm) for the L-type and 100 to 210 µm (average 160 µm) for the S-type. With these differences also come differences in weight, shape of spines and optimal growth temperatures (L-type rotifers have a wider temperature range while S-type rotifers have a higher temperature resistance) (Morretti 1999).

Figure 2: Morphologies of Brachionous species. B. quadridentatus (A1 & A2) and B. calyciflorus anuraeiformis (B1 & B2) exhibiting variable posterior spine morphologies. (Photos via Plewka 2016)

 

Life history:
As with all rotifers, species of Brachionous are capable of sexual and asexual reproduction (Figure 3). The asexual reproduction of Brachinous is carried out through amictic parthenogenetic reproduction. When mictic, sexual reproduction needs to occur, diploid females will produce a haploid egg, which if left unfertilized will develop into a haploid male. The stimulus for initiation of mixis is still unknown although photoperiod is likely a crucial actor.

Figure 3: Life cycle of a Brachionoid (from Nogrady et al., 1993)

        

 

Feeding Ecology:

Brachionous spp are filter feeders, ingesting bacteria, algae, yeast and protozoa. Studies have found that some brachionous spp such as Brachionus quadridentatus and Brachionus plicatilis, tend to investigate their food and have the ability to select particles on the basis of size. Using microplastics, researchers were able to show that B. quadridentatus actively selects for food 3 and 5 µm and B. plicatilis selects for smaller particles (Heerkloß and Hlawa 1995).

Works Cited:

Alcantara-Rodriguez JA., Ciros-Perez J., Ortega-Mayagoitia E., Serrania-Soto CR., Piedra-Ibarra E. 2012. Local adaptation in populations of a Brachionus group plicatilis cryptic species inhabiting three deep crater lakes in Central Mexico. Freshwater Biology, 57:728–740.

Fontaneto D., De Smet WH., Ricci C. 2006. Rotifers in saltwater environments, re-evaluation of an inconspicuous taxon. Journal of Marine Biology Association of the United Kingdom, 86:623–656.

Heerkloß, R., Hlawa, S. 1995. Feeding biology of two brachionid rotifers: Brachionus quadridentatus and Brachionus plicatilis. Hydrobiologia 313:219.

Jersabek CD., Segers H, Dingmann BJ. 2003. The Frank J. Myers Rotifera collection. The whole collection in digital images. The Academy of Natural Sciences of Philadelphia, Special Publications.

Lowe CD., Kemp SJ., Montagnes DSJ. 2005. An interdisciplinary approach to assess the functional diversity of free-living microscopic eukaryotes. Aquatic Microbial Ecology, 41,67–77

Morretti, Alessandro. Manual on hatchery production of seabass and gilthead seabream. Vol. 1. Food & Agriculture Org., 1999.

Nogrady, T., Wallace RL.,  Snell TW. 1993. Guides to the identification of the microinvertebrates of the continental waters of the world. Vol. 4. The Hague: SPB Academic Publishing. Rotifera. Vol.l. Pp. 47-93 in H.J.F. Dumont (ed.).

Plewka, M. 2016 Rotifer Images. Digital image. Pling Factory. N.p., n.d. Web. 24 Oct. 2016. <http://www.plingfactory.de/Science/Atlas/KennkartenTiere/Rotifers/01RotEng/E-TL/Genus/Brachionus.html>.