German wasp | Vespula germanica

German wasp

Vespula germanica

Coral bush | Ardisia crenata

Coral bush

Ardisia crenata

Purple loosestrife | Lythrum salicaria

Purple loosestrife

Lythrum salicaria

Pom pom weed | Campuloclinium macrocephalum

Pom pom weed

Campuloclinium macrocephalum

Canarybird bush | Crotalaria agatiflora

Canarybird bush

Crotalaria agatiflora

Peanut butter cassia | Senna didymobotrya

Peanut butter cassia

Senna didymobotrya

Rubber vine | Cryptostegia grandiflora

Rubber vine

Cryptostegia grandiflora

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Pacific barnacle

Balanus glandula

Common name:

Pacific barnacle

Scientific name:

Balanus glandula

Alternative common names:

Acorn barnacle. 

The Pacific barnacle is an acorn barnacle, occurring in the high-mid intertidal zone of rocky coastlines. Here it can be one of the most abundant solitary animals, reaching densities of more than 70 000 individuals per square metre. 

Additional Info

  • Where does this species come from?

    Pacific coast of North America.

    What is its invasive status in South Africa?

    NEMBA Category 3.

    Where in South Africa is it a problem?

    Cape Town in the Western Cape.

    How does it spread?

    Spread via larvae in shipping ballast water or hull-fouling.

    Why is it a problem?

    It invades rocky shores. It out-competes the indigenous African chthamalus species - Chthamalus dentatus - and as a result this species is currently rare on the Atlantic South African shores.

    What does it look like?

    Description: It is a small barnacle, up to 8mm in diameter. The shell is brown-grey in colour and smooth. The operculum (gill cover) is oval. Habitat: Mainly on intertidal rocks, in the open ocean and protected waters. Breeding: Mothers brood eggs, which are released into the water as larvae. These planktonic larvae undergo five moults to become a non-feeding cypris with six pairs of legs. Cyprids attach to a suitable substrate (avoiding potential predators or competitors) and metamorphose into adult form. They reach adult size in about two years.

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General News Updates

2019 National Symposium on Biological Invasio…

26-02-2019

This is your invitation to South Africa's 2019 National Symposium on Biological Invasions. The convention is hosted by the Centre for Invasion Biology (CIB), University of Stellenbosch, and the Biolo... Read more

2019 Invasive Species Training

22-01-2019

During the past five years (2014-2018), ISSA invasive species trainers have trained 4 000 in the identification of invasive species and laws pertaining to invasive species across South Africa.  ... Read more

Alien Grass Working Group

04-09-2018

Who are we? The South African National Alien Grass Working Group was jointly initiated by the South African Biodiversity Institute (SANBI) and the Centre for Excellence in Invasion Biology (C·I·B) in... Read more

Permits for planting indigenous Cynodon?

01-03-2018

On 16 February, 2018, South Africa's Department of Environmental Affairs issued amendments to the regulations and lists relating to the National List of Invasive Species.  Updates to the draft&n... Read more

Invasive species training 2018 dates released

28-02-2018

Interested in invasive species?  How much do you know about NEMBA invasive species compliance for landowners and organs of state? The South African Green Industries Council (SAGIC) have released... Read more

Communications post for Africa advertised

25-01-2018

The Nature Conservancy has advertised a brand new post:  Communications Manager, Africa Region. Knowledge of invasive species and water would be an asset in this post. See details below:    Job Titl... Read more