Ritter’s Tidepool Shrimp, Palaemon ritteri

Ritter’s Tidepool Shrimp, Palaemon ritteri. Underwater photographs taken from within Zihuantanejo Bay, Guerrero, March 2022. Photographs courtesy of Ron Woheau, Zihuantanejo.

Phylogeny:  Ritter’s Tidepool Shrimp, Palaemon ritteri (Holmes, 1895), is a member of the Palaemonidae Family of Palaemonid Shrimp. The Palaemon Genus is one of seventy-three genera in this large family. There are ninety-six species in the Palaemon Genus. They are also known as the Barred Grass Shrimp and in Mexico as Camaerón de Coral and Camaerón Intermareal de Ritter. The genus name Palaemon comes Greek mythology. Palaemon was the Greek God of harbors and protector of sailors and respected by fishermen.

Morphology: Ritter’s Tidepool Shrimp have a long toothed rostrum, three-jointed mandibular palp, and a branchiostegial spine. They have slender claws on their first two pairs of legs. Their body is transparent with dark stripes with small reddish spots on the tail and red banding on the legs. They reach a maximum of 4.6 cm (1.8 inches) in length.

Habitat and Distribution: Ritter’s Tidepool Shrimp are found in shallow intertidal waters and within subtidal rocky reefs as depths up to 40 m (130 feet). Ritter’s Tidepool Shrimp is an epipelagic species that are found in all Mexican waters of the Pacific Ocean however they are uncommon north of Magdalena Bay along the central and northwest coasts of the Baja Peninsula. They are the most common tidal pool shrimp in the Sea of Cortez.

Diet: Ritter’s Tidepool Shrimp are omnivorous scavengers, feeding on algae, detritus, small invertebrates, and insect larvae that take shelter during the day and emerge at night to feed on top of rocks and over sand.

Predators: Ritter’s Tidepool Shrimp are preyed upon by shore birds and fish.

Reproduction:  Ritter’s Tidepool Shrimp are gonochoric (male or female for life). They reproduce sexually by external fertilization. The males attach spermatophores to the female’s abdomen. The female later releases eggs into the water where they are fertilized by the male’s sperm outside of her body; this occurs within a brood chamber on the female’s abdomen where the eggs are carried until hatching. The eggs hatch into a larval stage.

Ecosystem Interactions: Ritter’s Tidepool Shrimp play an important role in recycling and distributing organic matter within an ecosystem.

Human Interactions: Ritter’s Tidepool Shrimp are of limited interest to humans. From a conservation perspective they have not been formally evaluated.

Synonyms: None.