Introduction

I decided to create an ID guide to help people when identifying the different species of shrimp that can be found within the anchialine pools of Hawaii. I am by no means an expert, I'm just a hobbyist who keeps a few brackish shrimp species as pets. I was deeply disappointed with the lack of information available online in regards to the species that inhabit the anchialine pools so wanted to create an ID guide to help people identify their observations. I plan to update this guide with more information and pictures as those become available in the future. If you're feeling benevolent and would like to provide pictures for any species I'm missing within this guide please do send me a message.

Shrimp Species:

Hawaiian Red Shrimp / Opae Ula (Halocaridina rubra)

This species is the most common and well known of the shrimp that inhabit the anchialine pools of Hawaii. It is a forager, which grazes on algae, bacteria and decaying organic matter in the pool, however is also capable of filter feeding. This shrimp can be variable in colour ranging from red to pink and even transparent. Very rarely yellow or orange individuals may be found. Colour can vary depending on the population. The most recognisable feature about this shrimp is it's claws. The claws are small and are held in a location to enable them to pick at the rocks they're stood on and then pull tiny pieces of food into their mouth. Their claws are held inwards towards their own body (opposed to outwards which is displayed in many of the predatory shrimp species within the same habitat.) They also possesses black coloured eyes. These shrimp can reach lengths of 0.6 inches or 15 millimetres.

Anchialine Snapping Shrimp (Metabetaeus lohena)

This species is the second most well known shrimp species to inhabit the anchialine pools. It possesses black eyes and larger claws for hunting prey. They can range in colour from red, pink, transparent or yellow. These shrimp can be identified by their larger claws and the presence of a large black spot in the centre of it's head just behind the eyes. They can reach lengths of around 0.7 inches or 18 millimetres.

Ivory Devil Shrimp (Antecaridina lauensis)

This species is red, pink or white in colour and possesses white eyes. Their claws are also white and pointed downwards for picking at algae, bacteria and decaying organic matter from the surface of rocks. They can appear similar to Halocaridina rubra, however the white claws and eyes of Antecaridina lauensis distinguishes them. Unfortunately a picture of a red individual isn't available for this guide due to copyright, however I can leave a link so you can see a red one here for yourself.

Glass Saddle Shrimp (Calliasmata pholidota)

This species looks rather similar to Metabetaeus lohena, however you can tell it apart as Calliasmata pholidota is larger, possesses larger claws and also has white eyes. Colour-wise red or transparent individuals can be found. Coloured individuals often (but not always) have a noticeable discoloured "saddle" like colouration on their carapace, which can also be transparent. The large claws for hunting prey signify their predatory nature. Unfortunately a picture of a an individual isn't available for this guide due to copyright, however I can leave a link so you can see both a clear one here and a red one here for yourself.

Feathered Hawaiian Pool Shrimp (Procaris hawaiana)

This larger shrimp species is endemic to Hawaii and lacks pinchers. It instead possesses legs covered in setae, which it uses to filter feed while swimming through the waters of the anchialine pool. It would be hard to mistake it for any other species due to the presence of setae covered legs and absence of claws. It can be found in colours ranging from light red, pink or orange. This is a rare species that is seldom photographed, so unfortunately I have no images to show of it right now.

Red-banded Skulker Shrimp (Periclimenes pholeter)

This shrimp species is red or pinkish in colour, with multiple horizontal red bands along it's abdomen. It possesses black eyes. It also has long arms and claws, indicating a predatory diet. This species is very timid and quick to flee into crevices when encountered, which makes it difficult to photograph. This is a rare species that is seldom photographed, so unfortunately I have no images to show of it right now.

Feeble Shrimp (Palaemon debilis)

A transparent shrimp species speckled with tiny brown spots. It has a blackish-brown rostrum. It also possesses a large black or brown spot on the 6th abdominal segment (the tail just before the fins). This species is known to inhabit brackish water such as estuaries, but can also be found within Hawaiian anchialine pools.

Burn's Shrimp (Palaemonella burnsi)

This shrimp species is small and can be found at lengths of up to around 0.3 inches or 7.6 millimetres. It is a transparent shrimp, which is sprinkled with red pigmentation. It possesses long arms for hunting and catching prey such as H. rubra.

Subterranean Giant Pool Shrimp (Vetericaris chaceorum)

This is the largest native shrimp that can be found in the anchialine pools of Hawaii. Ranging from 1.77 to 2 inches or 45 to 50.8 millimetres. The body of the shrimp can be yellow to orange in colour, however the appendages of the shrimp are transparent. This shrimp species is a strong swimmer and a predator, feeding on crustaceans including smaller shrimp such as Halocaridina rubra. Despite being predatory it lacks claws, instead swimming while holding it's legs into a basket-like shape to catch prey as it swims. This shrimp lacks eyes, however does possess eye stalks. There are currently no images available for this guide due to copyright, however you can take a look at what this species looks like here.

Hawaiian River Prawn (Macrobrachium grandimanus)

One of the larger species that can be found in the anchialine pools, reaching lengths of around 3 inches or 80 millimetres. It is a native species to Hawaii. The species is able to survive in both saltwater to freshwater, which makes it capable of inhabiting the brackish water of the anchialine pools. This species is brown in colour and identifiable from other species due to having asymmetrical claws, with one claw being significantly larger than the other.

Tahitian Prawn (Macrobrachium lar)

It is easily identified due to being so large, with some specimens exceeding 7 inches or 180 millimetres. It possesses symmetrically long arms and large claws. It can be variable in colour being found in shades of brown, grey and blue. It is an invasive species in Hawaii and can inhabit both freshwater and saltwater, making it capable of surviving within the brackish waters of the anchialine pools. It is carnivorous, predatory and when fully grown dwarfs all of the anchialine shrimp species in Hawaii.

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