Lepidurus packardi

Dorsal compound eyes; a large (up to 3.5 cm long) dorsal shield-like carapace, which is attached to the head region, covering most of the 35 to 48 pairs of swimming appendages (phyllopods); and two long cercopods at the end of the last body segment (telson) (Pennak, 1978, and Longhurst, 1955).

Mostly resembles LEPIDURUS COUSEI; but, their ranges are apparently disjunct. Identifications of the species entails the examination of the arrangement of spines and length of the supra-anal plate, eyes, and nucral organ. Individuals similar in external morphology to both species have been collected in the Modoc Plateau area of northeastern California between each of their respective ranges. Although preliminary, genetic work on LEPIDURUS, conducted by King (pers comm., 1996), has revealed that specimens obtained from the Modoc Plateau area are genetically distinct. Yet, the genetic relationships between them and L. PACKARDI and L. COUSEI have not been determined.

The only useful external morphological characteristic to distinguish the sexes are the ovisacs (AKA foot capsules) attached to the eleventh pair of appendages (i.e., phyllopods) of females (Linder, 1952).

Found in a variety of natural, and artificial, seasonally ponded habitat types including: vernal pools, swales, ephemeral drainages, stock ponds, reservoirs, ditches, backhoe pits, and ruts caused by vehicular activities. Wetland habitats vary in size from very small (2 square meters) to very large (356,253 square meters) and exhibit extremes in depth (2-15 cm) and volume (23-9,262,573 cubic meters (Helm, 1998).

Bisexual. Cysts occurring in the dry pool bottom hatch within three weeks of inundation (Ahl, 1991). Laboratory studies conducted by Ahl (1991) revealed cysts hatching within 17 days when incubated at 10 oC, however, the majority (64%) of the cysts hatched within four days. Lanway (1974) observed the appearance of hatchlings within two to three days after ponding in natural systems and 10 to 13 days after incubated at 10 oC in the laboratory. The author's dissertation work in the laboratory and field studies reveals similar hatching results as those obtained by Ahl (1991) and Lanway (1974). The hatched neonate is a metanauplius which undergoes several molts (ecdysis) each gaining additional phyllopod appendages until reaching allude. This process takes approximately six to seven weeks depending on temperature and food availability (Ahl, 1991, and Helm, in prep). Reproduction occurs throughout the ponding season, when females average between 10 and 12 mm in carapace length (Ahl, 1991). Ahl (1991) reported that fecundity increases with size and clutch size ranges from eight to 61 eggs. Ahl (1991) laboratory studies also revealed that eggs lain during the same ponding event can hatch without dehydration. Other life history characteristics include mean days to mature (38.1), mean days to reproduce (54.1), mean population longevity in days (143.6) (Helm, 1998).