Branchinecta packardi, commonly known as The Rock Pool Fairy Shrimp or Packard's fairy shrimp, belongs to the family Branchinectidae. This species can be found in a diverse range of habitats, including ephemeral potholes, predominantly throughout all seasons of the year. Although often associated with rocky granite habitats, Branchinecta packardi is not limited solely to these environments. It can be frequently observed in Canada, Mexico, and the United States, including states such as Texas, Arizona, Oklahoma, Kansas, Colorado, and New Mexico.
Anatomy: The characteristics outlined below may exhibit variations influenced by environmental conditions, population dynamics, and the organism's age.
Head:
Second Antenna:
Male: It has a slender outgrowth (apophysis) on the back-middle side near the upper end, and opposite it on the front-middle side a welt with a hardened (cornified) lower end. On the middle side just below the middle, there is a peg-like bump, with the tapering end directed towards the back and upper side. (Belk, Denton, 1975).
Female: Females have a reduced second antenna.
Thorax:
Dorsolateral Process (Lobes):
Male: Absent.
Female: On the back of the shrimp, there are typicallyfour cone-shaped bumps (lobes) that increase in size from front to back. These are located on the thoracic and abdominal segments of the shrimp’s body in females, with variations in the number or location of these lobes.
Thoracopods:
Male: limbs are curved with more spines instead of setae
Female: limbs are circular with more fine setae.
Reproductive Segments:
Male: A pair of penes.
Female: The ovisac (a sac containing eggs) is stout and cylinder-shaped, and it extends to below the 3rd to 5th abdominal segment.
Abdomen:
Uniform across sexes without distinctive characteristics.
Telson & Cercopods:
The cercopods, or tail appendages, feature bristles along their inner and lateral margins.
Egg:
Spherical in shape with minor indentations and ridges, ranging in coloration from white to bronze.
Morphology:
Size: Ranges from 1.5 cm to 2 cm in length, contingent on prevailing environmental conditions.
Coloration: The body is mainly transparent but may exhibit undertones of browns, tans, and blues.
Captivity and Growth:
Growth is influenced by multiple factors such as temperature, salinity, and care. These temperature ranges are based on our experience but do not represent the maximum or minimum.
Hatching Temperature Range: 50 to 80°F.
Temperature Range for Adults: 50 to 80°F.
Hatching: At temperatures of 60 to 72 Fahrenheit, nauplii appear after 24 to 48 hours.
Growth Rate: This species exhibits a rapid growth rate, achieving sexual maturity within 5 to 7 days. The average lifespan spans 8 to 10 weeks.
Behavior: The Rock Pool Fairy Shrimp is a fast-moving species, swimming sporadically throughout the water column and feeding on microorganisms. In the absence of readily available food, they will scrape substrate from the habitat floor. They constantly swim in a forward motion and are never stationary. Regardless of sex, both males and females swim very fast and aimlessly.
Reproduction: Males utilize their second antennae to swiftly latch onto females during mating, a process lasting only a few seconds.
References:
Belk, Denton. “Key to the Anostraca (Fairy Shrimps) of North America.” The Southwestern Naturalist, vol. 20, no. 1, 1975, pp. 91–103. JSTOR, https://doi.org/10.2307/3670015. Accessed 8 Mar. 2024.
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