Sights unseen, the magical miniature world of aquatic invertebrates

by CapeNature

By Jeanne Gouws, Freshwater Ecologist

When it comes to the animal Kingdom, conservation is not all about everything big. Big and “furry”, big and “leather-y” or big and “scale-y” vertebrates are not the be-all and end-all of biodiversity. The smaller invertebrate beings, often alien looking, are frequently forgotten.  CapeNature ecologists, however, did not forget about the aquatic invertebrates during recent river surveys, just before lockdown. Numerous river sites were visited during December 2019 and February and March 2020.

Meul River, Riviersonderend mountain catchment area. Jeanne Gouws (CapeNature Ecologist Freshwater) discussing the freshwater invertebrates collected from the river, with Whilmien Swanepoel, Lesley-Anne Williams, Rudie Davids and Pieter Booysen from the Vrolijkheid Nature Reserve. Photo credit: © Dr Martine Jordaan (Ecologist Fauna, Landscape West).

Teloganodidae, Barbarocthonidae, Sericostomatidae, Glossosomatidae. These big word tongue-twisters are the family names of some of the endemic mayflies and caddisflies that call the South Western Cape rivers home. It is not surprising then that they were collected in the healthy upper parts of rivers of the Hexrivier, Riviersonderend and Grootvadersbosch catchments in the Western Cape.

A spiny crawler mayfly nymph, of the family Teloganodidae (Genus Lestagella) from the Bloukranz River. This family, is a temperate Gondwanan relict family which is adapted to cold water. Species of this family have only been found in rivers of the southern and Western Cape regions with some disjunct distribution records in Madagascar and Asia. There are four genera found in South Africa, including species from the genus Lestagella, Ephemerellina, Nadinetella and Lithogloea. See Freshwater Life: a field guide to the plants and animals of southern Africa (Griffiths, Day and Picker) for more information. Photo credit: © Geoff McIlleron, October 2008.

These insects, like several others, prefer good quality water and share their slightly acidic, often peat stained watery homes with numerous other invertebrates. Some of the invertebrates collected during the surveys, could be seen with the naked eye and for others, a magnifying glass was needed. Some are fully aquatic, like riffle and marsh beetles and most bugs, spending their entire lifecycle in the water. Most are semi-aquatic, like dragonflies and damselflies, spending their early life stages under water and their adult stages above.

Subimago (one molt away from being a mature adult) mayfly, of the family Leptophlebiidae (genus Aprionyx) from the Elands River in the Eastern Cape. This particular genus is known as the smooth-clawed prong-gill mayflies. The nymphs occur in pools and moderately flowing parts of mountain streams and are endemic to southern Africa. Six Aprionyx species have been found in the southwestern Cape mountain streams, with two of them ranging further into the mountaineous parts of the Eastern Cape and Kwa-Zulu Natal. See Freshwater Life: a field guide to the plants and animals of southern Africa (Griffiths, Day and Picker) for more information. Photo credit: © Terence Bellingan previously associated with the Albany museum and SAIAB. Photo taken in October 2008.

These and other invertebrates, including flies, bugs, crabs and snails (amongst others), have differing tolerances to pollution levels in water. The super sensitive stoneflies and the endemic caddisflies are found in mountain streams and upper foothill rivers with good water quality.

Long-horned cased caddisfly larvae, of the family Leptoceridae (species Athripsodes bergensis). This species is found in the rivers of the southern Cape and they use grains of sand to construct their cases. They are also known to use the abandoned cases of other mayfly species, such as those abandoned by one of the larvae of the Barbarian tusk case makers (Barbarochthon brunneum), by just adding a sand-grain hood. See Freshwater Life: a field guide to the plants and animals of southern Africa (Griffiths, Day and Picker) for more information. Photo credit: © Jeremy Shelton

Common midges, mosquitos and freshwater earthworms can tolerate polluted waters, and were found at both healthy and polluted river sites during the recent surveys.

Eye to eye with a dragonfly larva from the Aeshnidae family, more commonly known as hawkers or emperors. This family includes the largest dragonfly species found in the world today. There are 456 described species in the world, 14 of which are found in southern Africa. See the Freshwater Life: a field guide to the plants and animals of southern Africa (Griffiths, Day and Picker) for more information.  Photo credit: © Jeremy Shelton

By assessing the health of ecosystems and providing distribution records for taxa our ecologists play a crucial role in contributing to the documenting of the unique biodiversity of our province. This in turn then ensures that the ecosystems housing these taxa are managed in an informed way, taking all relevant fauna and flora into account.

A water scorpion from the genus Laccotrephes (Family Nepidae, Sub-family Nepinae) in its freshwater habitat. These insects prefer slower flowing waters and ambush their prey including other bugs, beetles and even tadpoles by grasping them with their forelegs. They breathe through the siphon (or breathing tube; not pictured) while clinging upside-down from water plants. This specimen represents one of two genera that is found in rivers of the southern and Western Cape, the other one being species of the genus Ranatra (water stick insects). Photo credit: © Jeremy Shelton.

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