The Bat Star - Patiria miniata

Patiria miniata

By: Logan Pytleski

Classification

Kingdom: Animalia

Phylum: Echinodermata

Class: Asteroidea

Order: Valvatida

Family: Asterinidae

Genus: Patiria

Species: Patiria miniata

Description

The Bat star also known as the Sea bat, Webbed star, and Broad-disk, is a sea star. It has five to nine arms with the middle of its body being much wider than the length of its arms. There can be many solid or spotted colors of these sea stars such as green, purple, red, orange, yellow, or brown. The Bat star gets its name from the webbing between the arms, which appears like a bat’s wings.

Distribution

The Bat Star can be found along the Pacific coast from Alaska down to Mexico. They are in the subtidal region to a depth of about 300m. They are numerous in certain kelp forests. (Meinkoth 1981, Ricketts, et al 1985)

Locomotion

Usually in cnidarians and vertebrates, the speed of locomotion generally increases with a bigger body size. In echinoderms, crawling speed also increases with body size. So, a study on Patiria miniata was conducted to see if this was true. They used an excape-response test to calculate the maximum crawling speed along with the body size of the Patiria miniata.

Another method of testing was focused on the effect of arm number on maximum crawling speed by comparing speeds of five and six armed bat stars. With all the studies, the crawling speed relative to body size declined when body mass was larger, increasing arm length,

Since the Bat star puts their stomach onto bare rock, an experimenter Araki hypothesized that the Asterina miniata's (the sea star's) digestive enzymes break down cellulose. Bat stars produce bleached spots on corals and drift algae which shows degradation of photosynthetic pigments and so damage to the cell walls occur. Some researches have discovered that grazing of the Bat stars kill gametophytes or young sporophytes in some plants. The purpose of this study was to see if Patiria miniata did kill gametophytes and sporophytes in kelp during their early stages of growing. Grazing experiments were done from July 1991 through January 1992. The kelp Macrocystis pyrifera were grown in salt water. Four experiments were done to test the gametophytes and sporophytes for Bat star grazing. Twenty Bat stars were starved for 1 week and then 10 were added to each of the experimental tanks. Four to five Bat stars remained at the bottom of the tanks. At the end of the grazing experiment, it was thought that Bat stars might have contributed to the mortality of Macrocytis pyrifera even without direct grazing on them. A field study was also conducted. This study found that the percent of Macrocytis pyrifera gametophytes and sporophytes decreased significantly when Asterina miniata were present. This study clearly shows that Bat star grazing results in mortality of the giant kelp, Macrocystis pyrifera. They also found that bat star grazing may only have major affects on the kelp when recruitment conditions are poor like low light or nutrients. Giant kelp occurs in lower densities and mostly only affecting plants of small size. Overall, the results suggests that kelp acts as a weed as their reproductive rate and rapid growth is high. Mostly Bat stars seem to only feed on Asterina miniata for the few first weeks after settlement and although the effect may be minor to the kelp as it grows older, they affect the early succession of algal communities. (Leonard 81-98)

Genes In Gonads

Life histories of this sea star include diverse modes of fertilization and reproduction. This study includes; external fertilization of planktonic eggs in species with sex-changing adults and species with internal fertilization of eggs of hermaphrodites. Studies of cell biology and expression of several gamete recognition genes in sea stars species help people understand the evolution of mating systems at molecular levels. Their goal was to analyze diverse gamete recognition molecules and their evolution across modes of planktonic, benthic, and internal fertilization would make a potentially valuable complement to the excellent studies of population genetic structure among species divergence.