Streptocephalus henridumontis: Dumont’s Fairy Shrimp

Streptocephalus henridumontis, commonly known as Dumont’s Fairy Shrimp, belongs to the Streptocephalidae family and is found in a diverse range of habitats, including desert ephemeral pools. Populations of this species are observed in the Sonoran desert region, spanning northwestern Mexico and southwestern United States. It is frequently sighted in the southwestern United States, such as Arizona and New Mexico (Maeda-Martínez et al.).

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 has a simple, short front appendage that usually has two lobes at the tip. The second antennae have a long, extended part (peduncle) that doesn’t have a swelling (pulvinus), but instead, it has about 12 cone-shaped bumps on the inner side of its far end. The inner upper side of the base of the ‘hand’ has a forward-pointing spine-like structure. It has a triangular projection (spur) with a tip that has a swollen digit-like structure. There is a thin layer or plate on the side (lateral lamella) that forms a sharp angle with the far end of the ‘thumb’ and the spur. This arrangement creates a cavity in the middle-lower part (medioventrally). The far end of the ‘thumb’ is bent (geniculate), with a noticeable elbow on the lower side. The upper edge is unarmed (inerm), and the tip is pointed (acuminate). The ‘finger’ has two bends (bigeniculate), with two ‘teeth’ on the inner upper side of the near part. The far ‘tooth’ is wide at the base, with its front margin extended forwards and upwards to form a digit-like structure. The near ‘tooth’ is shorter, somewhat pointed (subacuminate) and slanted forwards. The upper layer (dorsal lamella) of the ‘finger’ is narrow at the first bend, with a straight border at the second bend. The tip of the ‘finger’ is pointed, with a swollen part near the tip that is armed with a spine-like structure on the lower side (Maeda-Martínez et al.).

• Female: reduced second antennae.

Thorax:

• Dorsolateral Process:

  • Male: absent.

  • Female: absent.

• Thoracopods:

  • Consistent between sexes with setae on the edges of the limbs.

• Reproductive Segments:

  • Male: pair of penes.

  • Female: The ovaries have two branches (biramous) and they vary in length, extending from the 4th to 8th segments of the thorax (the part of the body between the head and the abdomen) to the 4th to 6th segments of the abdomen. The pouch for carrying eggs (brood pouch) ends at the 6th to 7th segments of the abdomen (Maeda-Martínez et al.)

• Cyst:

  • The cyst, or the closed sac-like structure, is round and decorated with rib-like structures that form many-sided (polygonal) areas. The shell of the cyst is made up of a single layer that is soft and porous (spongy cortex)(Maeda-Martínez et al.).

Abdomen:

• Consistent between sexes with no unique features.

Tail:

• Cercopods:

  • The tail appendages (cercopods) are separate and are set with bristly hairs (setae) along the middle and side borders. They range in red to orange pigmentation.

Morphology:

• Size: 2.0cm to 2.5cm in length, contingent on prevailing environmental conditions.

• Coloration: body is transparent but may have hues of blue, pink, green.

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: 68 to 78°F.

• Temperature Range for Adults: 68 to 78°F.

Hatching: At temperatures of 68 to 78 Fahrenheit, nauplii appear after 24 to 48 hours.

Growth Rate: This species has a moderate growth rate reaching sexual maturity at around 10 to 14 days with an average life span of 8 to 10 weeks.

Behavior: This species prefers to swim in open water, feeding on microorganisms in the water column, and is constantly swimming more or less in a stationary manner.

Reproduction: males use their second antenna to latch onto the females only taking but a few seconds to mate.

References:

Maeda-Martínez, Alejandro M., et al. "Two New Fairy Shrimp of the Genus Streptocephalus (Branchiopoda: Anostraca) from North America." Centro de Investigaciones Biológicas del Noroeste, S.C., Apartado postal 128, La Paz, Baja California Sur, 23000, Mexico. Centro de Bachillerato Tecnológico Agropecuario 198, Maneadero, 22900 Baja California, Mexico.