© C. GRIFFITHS
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Text by Koen Martens |
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© C. GRIFFITHS
Ostracoda, the seed shrimps or mussel shrimps, are small bivalved crustaceans (1, live ostracod) living in a range of marine and non-marine water bodies, and even in some moist semiterrestrial habitats. About 2,000 species of non-marine ostracods worldwide; >150 reported from southern Africa; many more await description, one of which is included below.
Cypridoids
Superfamily Cypridoidea
Central adductor muscle (holding shells together) has 4–12 scars in loose ‘paw print’ pattern.
Cypridids
Family Cyprididae
The most species-rich of all non-marine ostracod families; includes about 1,000 species worldwide. Carapace shape, size and ornamentation widely variable, but all species have one dorsal (mostly pigmented) eye, and no eye tubercles.
2 Hairy giant ostracod
Megalocypris hispida
© K. MARTENS
Large laterally flattened species, mostly greyish or whitish in colour; valves (2, left valve shown) densely set with long setae. Size: About 5mm in length. Biology: Lives in shallow temporary vleis and pools in the Western Cape. RELATED SPECIES: South Africa can pride itself on having the largest living freshwater ostracod species in the world, the related M. princeps, which can reach 8mm in length; M. durbani is about 3–4mm in length and has been found in the Eastern Cape and in the Drakensberg.
3 Spiny paracypretta
Paracypretta acanthifera
© K. MARTENS
Species with very rounded carapace, almost as wide as it is high, externally set with ridges and spines. Size: About 1.1mm in length. Biology: Common in vleis and pools in the Western Cape, one record in KwaZulu-Natal. Free-swimming, found mostly in macrophyte stands. RELATED SPECIES: Genus has four more species, all occurring in southern Africa.
4 Tuberose zonocypris
Zonocypris tuberosa
© K. MARTENS
© K. MARTENS
Most brilliant representative of subfamily Cypridopsinae is without doubt the globular Z. tuberosa (4): carapace set with ridges and tubercules with elevated pores, from which long and stiff setae emerge. A truly spectacular species! Size: About 0.6mm in length. Biology: Not uncommon in vegetated vleis and lakes, especially in the Western Cape. RELATED SPECIES: Several other species in genus, most with differently ornamented valves, e.g. Z. cordata (4a), which is pitted, and Z. costata, which has ridges; both common in the Western Cape. Like most Cyprididae and Cypridopsinae, these species are good swimmers.
Notodromadids
Family Notodromadidae
A relatively small family, but with surprisingly high morphological variability. Recognisable by the divided dorsal eye and the presence of eye tubercles. Some species have a hyponeustic lifestyle (i.e. live upside down, attached to the water surface).
5 Arched centrocypris
Centrocypris species
© K. MARTENS
Ornamented species, with valve margins set with blunt teeth and dorsal valve margin highly arched, not straight (right valve shown). This species as yet undescribed. Known only from a water hole in Zambezi Region, Namibia. Size: About 1mm in length. Biology: Not known. RELATED SPECIES: Genus comprises eight species, three of which occur in central and southern Africa, the others in Southeast Asia.
Cytheroids
Superfamily Cytheroidea
All cytheroids have four central muscle scars in a ventral row. They are mostly marine, but the Limnocytheridae have many species in fresh water. None of the cytheroids can swim.
6 Obtuse gomphocythere
Gomphocythere obtusata
© K. MARTENS
Another Western Cape species. Males small, with laterally flattened valves, whereas females are larger, with wide posterior brood pouch. Valves are set with pits and ridges. Size: About 0.7–0.8mm in length. Biology: Fully benthic in vleis and lakes of South Africa, especially in the Cape region. RELATED SPECIES: Closely related G. capensis, which can be distinguished by an even wider brood pouch in females; has a similar distribution. The genus is speciose in most of southern and eastern Africa; it includes substantial numbers of endemic species in the ancient lakes Malawi and Tanganyika (East Africa).