User:Tannerhmgiles/Cellana exarata

Cellana exarata, also known as the black-foot ‘opihi or Hawaiian Blackfoot is a species of marine gastropod known as a limpet. This species is edible and belongs to one of the families of true limpets. ‘Opihi are significant in Hawaiian history where they have had many uses such as food, tools, and jewelry. They are known as a “fish of death.”

Classification

Limpets are gastropods belonging to the subclass Patellogastropoda and the family Nacellidae. They share many characteristics with many types of primitive mollusc other than gastropods, including a structure called the radula and shell micro-structure.

Anatomy

Diagram of Limpet Shell and Underside.

Basic Anatomy of Saltwater Limpet

This species has flattened, conical shells with a large, muscular foot. Their shells are cone shaped to protect them from waves, while the foot clings to rocks. Hawaiian Blackfoots, like other limpet species, lack an operculum, unlike other snails. Covered by the shell, is their head, mantle, and foot. Their vision is poor but their head and mantle contain small tentacles that protrude just beyond the edge of their shell. These are sensory organs used to help limpets perceive their surroundings. They feed on algae using a radula, an organ made of chitin that is covered in small teeth. They breathe using gills. Their anatomy suggests that limpets may be the most primitive of the living sea snails. Hawaiian Blackfoots can be distinguished from other Hawaiian limpet species by comparing the ridges on their shells, Blackfoot Limpets are somewhat smooth with ridges that do not extend to the edges of the shell. They can reach up to 60mm in length but average between 33 and 37mm.

Habitat

This marine species is found among rocky intertidal zones. Blackfoot limpets are found much higher in the intertidal zone compared to other Hawaiian limpet species. They cling to rocks with their muscular foot, this prevents them from being torn off rocks by predators or strong waves during high tide. During low tide this species is exposed to the air, so they must be able to withstand periods of exposure. They are subject to more extreme temperatures and conditions than other species of limpets.

Distribution

This species is endemic to the islands of Hawaii. It is the most common species of the four species that are found in Hawaii.

Behavior

Radula of Limpet.

All limpets, including the Blackfoot, create small indentions in rocks that are known as homing scars. They leave their homing scars to feed and then return back to the same indentation in the rock. These homing scars help prevent water loss during low tide.

Feeding

Blackfoot Limpets feed on algae found on the rocks using a feeding structure called a radula.

Reproduction

This species reproduces via external fertilization which takes place based on environmental cues. Males and females release their sperm and eggs into the water, this is known as broadcast spawning. The eggs and sperm then fertilize in the water and develop into larvae that drift in the water. They then settle onto shorelines and metamorphose into limpets, their adult form. They typically spawn from May to June and then again from November to January. They reach reproductive age when their shell length is between 20 and 25 mm in length.

Conservation

Over-harvesting

This species has become scarce due to over-harvesting caused by a lack of rules and regulations. There are now strict rules in place to limit the harvesting of these limpets and sustain healthy population sizes. These regulations limit the size, amount, and species that can be harvested. They can be collected year round but must be at least one and one-fourth inches in the longest dimension to be legally harvested. Due to their habitat, many people have died attempting to collect Hawaiian Blackfoots and this is one reason that commercial fish hatcheries have been working to successfully breed and raise this species in captivity. Some fishermen practice traditional methods that are supposed to protect Blackfoots, these include avoiding limpets that are below the waterline and harvesting predators of the limpets.

Climate Change

Not much research has been performed on the affects that climate change has on 'Opihi but a study done in 2019 suggests that this species has a narrow thermal niche that will continue to get narrower as the Earth warms.

Cultural Significance

‘Opihi were consumed by early Hawaiians and are still a common source of food in the Hawaiian Islands, often eaten raw or boiled. Their shells were often traditionally used for jewelry or tools. There is also evidence that Hawaiian limpet species were used for various religious rituals in Hawaiian history. They are known as the “fish of death” because they can be incredibly dangerous to harvest due to their habitat.