Branchinecta mackini, commonly known as the Alkali Pool Fairy Shrimp, belongs to the Branchinectidae family. Dexter first described this intriguing species in 1956.
Typically inhabiting ephemeral environments like dry lake beds, the fairy shrimp thrives in habitats rich in chemical compounds such as calcium sulfate, calcium carbonate, and sodium salts. These areas are characterized by a combination of sand, loam, and clay soils (Rogers, D. C., 2014). The distribution of Branchinecta lindahli is extensive, stretching from Canada to Mexico. It is predominantly found in the western United States, along the Pacific Coast. This species usually appears in its habitats during the winter or spring (Thorp, J. H., & Rogers, D. C., 2015).
Anatomy: The characteristics outlined below may exhibit variations influenced by environmental conditions, population dynamics, and the organism's age.
Head:
Second Antenna:
Male:The shrimp possesses a second antenna situated near the body, known as the proximal antennomere, which features a basal posteriomedial apophysis and is adorned with small spines along its medial side. The distal antennomere of this second antenna bends inward, with a significant flexure near its median section. This segment is relatively flat and terminates in a tip that does not recurve (Obregón-Barboza, Hortencia, et al., 2015).
Female: The second antennae are smaller in size, while the first antenna is longer than the second antennae. The second antennae have a cylindrical shape with a slightly pointed tip.
Thorax:
Dorsolateral Process (Lobes):
Both males and females have smooth thoracic segments without lobes.
Thoracopods:
Male: Limbs tend to have a more curved shape and contain more spines than fine setae.
Female: The limbs are more rounded and covered with fine setae.
Reproductive Segments:
Male: A pair of penises.
Female:The ovaries are divided into two branches, with the lateral egg duct positioned at the beginning of the second genital segment. The mating amplexial groove is not clearly defined, and the cylindrical brood pouch does not have specific structures for the male's second antennae during copulation. The end of the brood pouch extends under the second or third abdominal segment, which aligns with the fourth or fifth segments that lack legs (Obregón-Barboza, Hortencia, et al., 2015).
Abdomen:
Uniform across sexes without distinctive characteristics.
Telson & Cercopods:
The cercopods, or tail appendages, feature bristles along their inner and lateral margins.
Egg:
The egg, or the closed sac-like structure, has a surface that is decorated with dips (indentations) and raised lines (ridges). It is round in shape and has rib-like structures that form many-sided (polygonal) areas.
Morphology:
Size: 2 cm to 2.5 cm in length, contingent on prevailing environmental conditions.
Coloration: The body is predominantly transparent with possible undertones of brown, tan, and blue.
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 72°F.
Temperature Range for Adults: 50 to 75°F.
Hatching: At temperatures of 60 to 72 Fahrenheit, nauplii appeared after 24 to 48 hours.
Growth Rate: This species grows at a moderate pace, reaching sexual maturity in 10 to 14 days and typically lives for 8 to 10 weeks.
Behavior: The fairy shrimp is a species that moves at a moderate pace, gracefully gliding through the water while feeding on microorganisms. When food is scarce, they scrape the substrate at the bottom of their habitat for sustenance. These creatures usually stay close to the base of their habitat, hovering slightly above the substrate. They are recognized for their continuous forward swimming movement, although females may sometimes stay still for extended periods.
Reproduction: Males utilize their second antennae to swiftly latch onto females during mating, a process lasting only a few seconds.
References:
Obregón-Barboza, Hortencia, et al. "A Review of the Branchinecta (Branchiopoda: Anostraca) from the Baja California Peninsula: First Record of the Giant Fairy Shrimp B. gigas Lynch, 1937 from Mexico." Journal of Crustacean Biology, vol. 35, no. 3, 2015, pp. 433-440.
Thorp, J. H., & Rogers, D. C. (2015). Thorp and Covich’s Freshwater Invertebrates: Keys to Nearctic Fauna (4th ed.). Elsevie
Lynch, J. E. (1964). Packard’s and Pearse’s species of Branchinecta: Analysis of a nomenclatural involvement. American Midland Naturalist, 71(2), 466-488. Retrieved from http://www.jstor.org/stable/2423306
Rogers, D. C. (2014). Anostracan (Crustacea: Branchiopoda) zoogeography II. Relating distribution to geochemical substrate properties in the USA. Zootaxa, 3856(1), 1-49. Magnolia Press. https://doi.org/10.11646/zootaxa.3856.1.1
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