Ducks, cranes and other aquatic birds abound in the delta.
Aquatic plants occur among seed plants but these are readaptations of land plants to an aquatic environment.
Aquatic plants with submerged leaves and erect leaves or stems:
The prevalent number of testes is one pair in the aquatic genera and two pairs in earthworms. But there are exceptions; thus a species of Lamprodrilus has four pairs of testes.
Lari.-Aquatic, vomer complete.
In terrestrial A, Lumbricus : 9, to, segments contain ing spermathecae, the orifices of forms dorsal pores are usuwhich are indicated; 14, segment b ally present; in aquatic earing oviducal pores; 15, segforms a head pore only.
In many aquatic plants, the endosperm of the seed is absent or very scanty.
Originally terrestrial groups have taken to an entirely aquatic life, and vice versa; others, originally endowed with the power of flight,.
The Amphizoidae, for example, a small family of aquatic beetles, are known only from western North America and Eastern Tibet, while an allied family, the Pelobiidae, inhabit the British Isles, the Mediterranean region, Tibet and Australia.
The Haliplidae form a small aquatic family allied to the Dyticidae.
Order Colymbiformes.-Plantigrade, nidifugous, aquatic. All toes webbed, fourth largest, hallux short; metatarsus laterally compressed; tibia with high, pyramidal crest.