Freshwater Life - A field guide to the plants and animals of southern Africa

7	Text by Charlene Janion-Scheepers

Springtails

Subclass Collembola

Small (0.5–8mm in length) six-legged arthropods with elongated to globular bodies. Although once considered to be primitive insects, and still often included in insect field guides, they are now placed in their own separate subclass. They are best recognised by the unique, forked, jumping organ (furca) folded under the abdomen, and an abdominal organ called the ventral tube, thought to be used for water balance.

Although terrestrial and none actually live underwater, their water-repellant cuticle makes them well adapted to living in damp surroundings. They commonly occur on the surfaces of water bodies, and are associated with snowfields, glaciers and wet caves. Several species are intertidal. The claw of the foot and the end of the furca are modified in these water-adapted species. Only the first of these groups is common in South Africa and is included below. Springtails feed mostly on detritus, fungal hyphae and other microorganisms.

Males deposit a spermatophore (sperm package), which is taken up by the female, who subsequently lays eggs singly or in batches in the soil. Some species can also reproduce parthenogenetically (virgin birth, absence of males). Juveniles resemble adults, differing only in size and number of hairs on the body. Moulting occurs periodically throughout the life span, which varies from a few months to several years. The freshwater springtail fauna comprises about 525 species worldwide, of which about 20 are known from southern Africa. Although knowledge is growing for this group in southern Africa, studies on their distribution and ecological function are lacking and there are still many undescribed species.

1 Long springtails

Order Entomobryomorpha

Hydrophilic species mostly belonging to the family Isotomidae. Recognised by having a poorly developed first thoracic segment, an elongated body shape and no scales. Colour variable. Maximum of eight ocelli per eye. Size: Up to 4mm in length. Biology: Can be found floating on water, in soil or among and under rocks along banks of streams or dams. Most common species found along water bodies include Isotomurus palustris (1 and map) and Ballistura schoetti (1a). Both are recorded from scattered localities in South Africa and probably widespread. Feed on detritus and microorganisms. Some families reproduce parthenogenetically, but mostly females are fertilised by taking up spermatophores deposited by males, and then lay clutches of eggs on any substrate. RELATED SPECIES: Other species, such as Isotoma species, are often found in wet moss by waterfalls and streams.

2 Plump springtails

Order Poduromorpha

Hydrophilic species mostly belonging to the Family Hypogastruridae. Clearly developed first thoracic segment; body mostly dark, but colour varies from dark grey to pink to reddish blue. Most common and observed species include Ceratophysella denticulata (distribution shown) and Hypogastrura species (2). Size: Up to 1.5mm in length. Biology: Often found in dense mats that may number thousands of individuals, floating on the surface of rain pools or small ponds (2a). Also recorded from various localities in South Africa and are widespread, but especially common in disturbed sites. Feed on detritus and microorganisms. RELATED SPECIES: In northern temperate countries Podura aquatica (the only species of family Poduridae) is frequently found on water, but this species has not yet been recorded in South Africa.

3 Round springtails

Order Symphypleona

Order easily recognised by globular body shape, and members may have distinctive colour patterns; species from the family Sminthurididae mostly found near aquatic habitats. Size: Up to 2.5mm in length. Biology: Commonly found floating on surface pools after rain, and have even been found on surfaces of swimming pools. Males often display elaborate courtship behaviour to entice a female to take up the spermatophore; family Sminthurididae males have modified antennae for attaching to the antennae of the female. Species widespread and found year-round near water. Feed mainly on detritus and fungi, although a few can also feed on live plant material. RELATED SPECIES: Most common genera found along water are Sphaeridia (3), Sminthurides species (family Sminthurididae) and Dicyrtomina species (family Dicyrtomidae) (3a).

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Springtails

Subclass Collembola