A morphological comparison of the phyllopodous thoracic limbs of a leptostracan (Nebalia sp.) and a spinicaudate conchostracan (Leptestheria sp.), with comments on the use of Phyllopoda as a taxonomic category

The fourth thoracic appendage of an adult female Nebalia sp. (class Malacostraca, order Leptostraca) is compared with that of an adult female Leptestheria sp. (class Branchiopoda, order Spinicaudata). Although these limbs are "phyllopodous" (flattened, leaflike) in both orders, they differ markedly in the size and arrangement of endites, type and number of setae, and function. Setal types found on the fourth thoracopod of Nebalia sp. are variations of a basic plumose or plumodentate seta, and the diversity of setal types is low. None of the setae is annulate, a distinction in setal formation. In contrast, on the fourth thoracopod of Leptestheria sp. there is a wide variety of setal types and stout spines, some of which have been reported from other "conchostracans" (orders Spinicaudata and Laevicaudata) but not from the thoracopods of any leptostracan. Nearly all of the setae are annulate. Thus, the single character (phyllopodous thoracic appendages) supposedly linking leptostracans and branchiopods in some classificatory schemes (e.g., the class Phyllopoda sensu Schram) has clearly arisen independently in these two taxa and in several other crustacean groups, and cannot be used as an indicator of phylogenetic affinity. The rejection of the class Phyllopoda as defined by Schram is supported, as are arguments for retention of leptostracans within the Malacostraca. The use of Phyllopoda as a taxonomic name, regardless of which crustacean groups are considered to compose the taxon, is discouraged in light of the rather convoluted history and inconsistent application of this term.

Coordination of the movements of the appendages in the Tasmanian mountain shrimp Anaspides tasmaniae (Crustacea; Malacostraca; Syncarida)

The syncarid Anaspides has changed very little in structure since the Palaeozoic and is considered to represent a very early branch from the main line of crustacean evolution. An examination of locomotory co-ordination in Anaspides is made on the assumption that a primitive functional condition will be found where a primitive structural condition exists. The animal uses its thoracic endopodites and its abdominal appendages for locomotion and its thoracic exopodites for respiration. The locomotory appendages are coordinated in a linear sequence, with the exception of the large thoracic appendage at the junction of the abdomen and the thorax. Ipsilateral coupling is weak and gliding coordination is common. The respiratory appendages show considerable independence from the locomotory appendages even though the thoracic exopodites and endo-podites share common basal segments. The exception to this is that, where there is ongoing activity in the respiratory appendages while the animal is stationary, the rhythm of the respiratory appendages determines the rhythm of the locomotory appendages at the commencement of movement. The implications of these findings for an understanding of locomotory oscillator function are discussed.

Environmental factors influencing the feeding behavior of Daphnia magna Straus

Feeding behavior of Daphnia magna on the food organism Saccharomyces cerevisiae, determined by electronic measurement of frequency of thoracic appendage movements (FTA), differs between groups cultured in lake, river, and dechlorinated tap water. FTA also varied between similar Daphnia cultured at different times in water collected from a common source. It is suggested that variability in water quality or physiological changes, possibly influenced by thermal history of the animal, alters feeding behavior. The concept of a "normal filtering rate" (McMahon and Rigler 1965) is reevaluated.