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Thamnocephalus platyurus: Beavertail Fairy Shrimp

Updated: Jul 29, 2024


Thamnocephalus platyurus, commonly known as the Beavertail Fairy Shrimp, belongs to the family Thamnocephlidae. This species can be found in a diverse range of habitats, including playas, predominantly during the warmer seasons of the year. Although it is often associated with habitats having moderate dissolved solids, Thamnocephalus platyurus is not limited solely to these environments. It can frequently be observed in Mexico and the United States, specifically in states such as Texas, New Mexico, Colorado, Arizona, and California.


Anatomy: The characteristics outlined below may exhibit variations influenced by environmental conditions, population dynamics, and the organism's age.


 

Head:



Second Antenna:

Male: The second antenna has two segments (antennomerae); the far segment is slender, hard (scleroid), without bristles (non-setose), curved and tapers towards the tip on the lower side. The base segment is cylindrical, robust, with a cone-like process at the end on the side, and with a long fleshy ridge in the middle, elongated at the tip to a flexible, thick, digit-like process. The front appendage on the head is faintly ringed (annulated), as long as half of the body, with a single trunk at the base that branches out at the far end into two major arms on the right and left. The trunk is about as long as the second antenna, somewhat flattened from top to bottom, and as wide at the base as the base of the second antenna. The first branch of the major arm is inserted on the upper middle side, as long as the distance from its base to its head, with the base third unbranched, after which 3-4, usually 3 unbranched spine-like sub-branches of similar length occur, ending in a claw-like spine. The second branch of the major arm is in a front position relative to the first branch, with 3-7, usually 5 upper spine-like sub-branches, with the base two usually split at the tip; all sub-branches end in a claw-like spine. There are no lower sub-branches. The third branch of the major arm forms a peg-like process structurally, ending in a distinct spine pointing downwards, inserted on the upper middle side on the base part of the arm.


Female: The second antenna is long and flat, and when it is bent over towards the back, it reaches the fifth segment of the thorax (the part of the body between the head and the abdomen).


 

Thorax:


Dorsolateral Process (Lobes):

The thoracic segments are smooth and without lobes, which is characteristic of the genus

 

Thoracopods:

The structure is comparable across sexes, characterized by delicate setae along the limb's edges.


 

Reproductive Segments:

Male: A pair of penises.

Female: The ovaries have one branch (uniramous), with the lateral egg duct at the first reproductive segment. The groove for mating (amplexial groove) is not differentiated. The pouch for carrying eggs (brood pouch) is pear-shaped (pyriform) with no structures to receive the male’s head appendages during mating. The tip of the pouch has lower and upper triangular lips and extends under the sixth abdominal segment (eighth segment without legs).


 

Abdomen:

Fused segments, i the same between sexes.


 

Telson & Cercopods:

The last abdominal segments and tail appendages (cercopods) are flattened from top to bottom, forming a prominent wide paddle-like structure where side ridges (lateral carinae) extend forwards usually up to the second abdominal segment (fourth segment without legs), with marginal bristles (setae) limited to the tail segment (telson).


Egg:

The eggs are round, with a shell that is decorated by twisted ribs forming many-sided (polygonal) areas. There are eight to 13 polygonal areas distributed in a half-sphere section.


 

Morphology:

Size: 4cm to 5cm in length, contingent on prevailing environmental conditions.

Coloration: The body is typically transparent but can exhibit tints of orange, pink, and red depending on the environment and oxygen levels.


 

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: 72 to 78°F.

Temperature Range for Adults: 72 to 78°F.


Hatching: At temperatures of 72 to 78 degrees Fahrenheit, nauplii appear after 24 to 48 hours.


Growth Rate: This species has a rapid growth rate but reaches sexual maturity at around 14 to 17 days, with an average lifespan of 10 to 14 weeks.


Behavior: This species prefers to swim in open water, feeding on microorganisms in the water column, and is constantly swimming, never in a stationary pattern.


Reproduction: Males use their second antenna, including the cephalic appendage, to latch onto females, taking only a few seconds to mate.


 

References:

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