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Archaster typicus Müller & Troschel, 1840


Table of Contents

Table of Contents

Archaster typicus on St John's Island, Singapore (Image by Samuel Chan, 2015)




Overview

Archaster typicus is a common sea star found in the Indo-West Pacific region, including Singapore

Footnote Macro

Clark, A. M. & Rowe, F. W. E., 1971. Monograph of shallow-water Indo-West Pacific echinoderms. London, Trustees of the British Museum (Natural History).

! It is also known as the common sea star or the sand-sifting sea star

Footnote Macro

P. K. L., Corlett, R. & Tan, H., 2011. Singapore Biodiversity. Singapore, Editions Didier Millet in association with Raffles Museum of Biodiversity Research

. The common sea star inhabits sandy beaches and can be found on sand or buried within with a distinct star shaped imprint

Footnote Macro

P. K. L., Corlett, R. & Tan, H., 2011. Singapore Biodiversity. Singapore, Editions Didier Millet in association with Raffles Museum of Biodiversity Research

. It is perhaps, most well-known for its mating behaviour where the male sea star mounts on top of the female

Footnote Macro

P. K. L., Corlett, R. & Tan, H., 2011. Singapore Biodiversity. Singapore, Editions Didier Millet in association with Raffles Museum of Biodiversity Research

. A specimen is also on display at the Lee Kong Chian Natural History Museum

Footnote Macro

“Magical echinoderms” by Lee Kong Chian Natural History Museum. Lee Kong Chian Natural History Museum Web Mobile Experience, 2015. URL: http://lkcnhm.nus.edu.sg/webME/67 (accessed on 11 Nov 2015)

!

Archaster typicus on exhibit at the Lee Kong Chian Natural History Museum (Image by Samuel Chan, 2015)


Nomenclature

The name 'common sea star' is a classic example of why vernacular names cause ambiguity. (For why we use scientific names, see this Guardian article

Footnote Macro

“What’s in a name? Why scientific names are important” by Dave Hone. The Guardian, 19 Jun 2013. URL: http://www.theguardian.com/science/lost-worlds/2013/jun/19/dinosaurs-fossils (accessed on 11 Nov 2015)

). The name 'common sea star' can refer to a variety of species across the world, including the common starfish of the Atlantic, Asterias rubens 

Footnote Macro

“Common starfish (Asterias rubens)” by Arkive. Wildscreen Arkive, 2015. URL: http://www.arkive.org/common-starfish/asterias-rubens/ (accessed on 11 Nov 2015)


. Sand-sifting sea star, while providing some description of it, can also refer to a variety of sea stars from the genus Astropecten 

Footnote Macro

“Telling Apart Sand Stars: Archaster vs. Astropecten! Two Common Trade Species” by Christopher Mah. The Echinoblog, 26 Apr 2011. URL: http://echinoblog.blogspot.sg/2011/04/telling-apart-sand-stars-archaster-vs.html(accessed on 11 Nov 2015)

.

The origins of the scientific name, or its etymology, likely lies in the combination of Latin words arch meaning "chief" and astermeaning "star"

Footnote Macro

“Online Etymology Dictionary” by Douglas Harper. Online Etymology Dictionary, 2015. URL: http://www.etymonline.com/(accessed on 11 Nov 2015)

. The species epithet typicus comes form the same Latin word meaning "of or pertaining to a type"

Footnote Macro

“Online Etymology Dictionary” by Douglas Harper. Online Etymology Dictionary, 2015. URL: http://www.etymonline.com/(accessed on 11 Nov 2015)

. Together, this likely means that Archaster typicus was one of the main types of sea star.

Description

The common sea star resembles a typical large sea star with five arms and radial symmetry. It usually possesses varying brown to gray colouration, with some variation of patterns on the arms. Specimens with 4 to 7 arms have also been seen, though much rarer than the normal pentaramous ones

Footnote Macro

“Common sea star” by Ria Tan. Wildsingapore fact sheets, Jan 2014. URL: http://www.wildsingapore.com/wildfacts/echinodermata/asteroidea/archaster.htm (accessed on 11 Nov 2015)

. It possesses spines thought to aid it in burial into sand

Footnote Macro

“Telling Apart Sand Stars: Archaster vs. Astropecten! Two Common Trade Species” by Christopher Mah. The Echinoblog, 26 Apr 2011. URL: http://echinoblog.blogspot.sg/2011/04/telling-apart-sand-stars-archaster-vs.html(accessed on 11 Nov 2015)

.

The parts of the sea star are labelled in the preserved specimen below, where the colour has been through preservation in ethanol. The terms aboral and oral refer to the side opposite the mouth and the side with the mouth respectively, commonly used in describing echinoderms.

Labelled Aboral view of Archaster typicus specimen (Image by Samuel Chan, 2015)

Closeup images of madreporite and mouth of Archaster typicus (Image by Samuel Chan, 2015)

Labelled Oral view of Archaster typicus specimen (Image by Samuel Chan, 2015)

Closeup images of tube feet and arm tip of Archaster typicus (Image by Samuel Chan, 2015)



Identification

In Singapore, only one species of the Archaster genus is known - Archaster typicus 

Footnote Macro

P. K. L., Corlett, R. & Tan, H., 2011. Singapore Biodiversity. Singapore, Editions Didier Millet in association with Raffles Museum of Biodiversity Research

. There are some similar sea stars that look like it, both within the same genus and within other genera. A brief guide is listed below for some of the more commonly confused species.

Between Archaster spp.

It can be distinguished from other Archaster species by the number of inferomarginal spines

Footnote Macro

Clark, A. M. & Rowe, F. W. E., 1971. Monograph of shallow-water Indo-West Pacific echinoderms. London, Trustees of the British Museum (Natural History).

Footnote Macro

Clark, H. L., 1946. The echinoderm fauna of Australia. Washington, D. C., Carnegie Institution of Washington Publication

.

A. typicus possesses only one wide, flat inferomarginal spine per segment while the other species A. angulatus and A. loriolipossesses two or three

Footnote Macro

Clark, A. M. & Rowe, F. W. E., 1971. Monograph of shallow-water Indo-West Pacific echinoderms. London, Trustees of the British Museum (Natural History).

Footnote Macro

Clark, H. L., 1946. The echinoderm fauna of Australia. Washington, D. C., Carnegie Institution of Washington Publication

.

From sand stars (Astropecten spp.)

It can be distinguished from other similar sand stars like the Astropecten spp. by the radial line running down the arms and the shape of the tube feet

Footnote Macro

“Telling Apart Sand Stars: Archaster vs. Astropecten! Two Common Trade Species” by Christopher Mah. The Echinoblog, 26 Apr 2011. URL: http://echinoblog.blogspot.sg/2011/04/telling-apart-sand-stars-archaster-vs.html(accessed on 11 Nov 2015)

.

Astropecten sp. at Changi Beach (Image by Samuel Chan, 2015)



On A. typicus, a clear central row of plates form a distinct line

Footnote Macro

“Telling Apart Sand Stars: Archaster vs. Astropecten! Two Common Trade Species” by Christopher Mah. The Echinoblog, 26 Apr 2011. URL: http://echinoblog.blogspot.sg/2011/04/telling-apart-sand-stars-archaster-vs.html(accessed on 11 Nov 2015)

. This is not seen on the various Astropecten spp. The tube feet of A. typicus ends in a flat sucker-like disc while the tube feet of Astropecten spp. end in a point

Footnote Macro

“Telling Apart Sand Stars: Archaster vs. Astropecten! Two Common Trade Species” by Christopher Mah. The Echinoblog, 26 Apr 2011. URL: http://echinoblog.blogspot.sg/2011/04/telling-apart-sand-stars-archaster-vs.html(accessed on 11 Nov 2015)

. The stomach of A. typicus is also green and can be everted for feeding while most species of Astropecten cannot

Footnote Macro

Ventura, C. R. R., 2013. Astropecten in Lawrence, J. Starfish (pp. 101-108) Baltimore, John Hopkins University Press.

.

From eight-armed sea star (Luidia maculata)

It can be distinguished from a similar looking eight-armed sea star, Luidia maculata in Singapore by its size, the number of arms, and the shape of the tube feet

Footnote Macro

“Common sea star” by Ria Tan. Wildsingapore fact sheets, Jan 2014. URL: http://www.wildsingapore.com/wildfacts/echinodermata/asteroidea/archaster.htm (accessed on 11 Nov 2015)

.

Luidia maculata at Changi Beach (Image by Samuel Chan, 2015)



L. maculata usually possesses eight arms, but can have any number from six to nine, with lengths from 120mm to 200mm compared to the usual five arms which do not usually exceeds 120mm in A. typicus 

Footnote Macro

“Common sea star” by Ria Tan. Wildsingapore fact sheets, Jan 2014. URL: http://www.wildsingapore.com/wildfacts/echinodermata/asteroidea/archaster.htm (accessed on 11 Nov 2015)

Footnote Macro

“Eight-armed sea star” by Ria Tan. Wildsingapore fact sheets, Jan 2014. URL: http://www.wildsingapore.com/wildfacts/echinodermata/asteroidea/luimaculata.htm (accessed on 11 Nov 2015)

. The tube feet of L. maculata are also pointed like the Astropecten spp., differing from A. typicus with the flat sucker-like disc

Footnote Macro

“Common sea star” by Ria Tan. Wildsingapore fact sheets, Jan 2014. URL: http://www.wildsingapore.com/wildfacts/echinodermata/asteroidea/archaster.htm (accessed on 11 Nov 2015)

Footnote Macro

“Eight-armed sea star” by Ria Tan. Wildsingapore fact sheets, Jan 2014. URL: http://www.wildsingapore.com/wildfacts/echinodermata/asteroidea/luimaculata.htm (accessed on 11 Nov 2015)

.

From knobbly sea star (Protoreaster nodosus)
It can be distinguished from the similarly large knobbly sea star by the general appearance. Adult knobbly sea stars are generally bright orange with black bumps on top of the sea star, as compared to the brown or gray common sea star. Knobbly sea stars are also dorsal-ventrally thicker than the common sea star. More information is provided in the knobbly sea star page.



Habitats

This sea star generally prefers sheltered, silty and sandy habitats, with noted ontogenetic shifts from mangroves in their juvenile stage to seagrass meadows to sandy lagoons in adulthood

Footnote Macro

Bos, A., Gumanao, G., van Katwijk, M., Mueller, B., Saceda, M. & Tejada, R., 2010. Ontogenetic habitat shift, population growth, and burrowing behavior of the Indo-Pacific beach star, Archaster typicus (Echinodermata; Asteroidea). Marine Biology, 158(3), 639-648.

. In juvenile stages, the mangrove and seagrass habitat confers greater benefit of protection against predation and wave action

Footnote Macro

Bos, A., Gumanao, G., van Katwijk, M., Mueller, B., Saceda, M. & Tejada, R., 2010. Ontogenetic habitat shift, population growth, and burrowing behavior of the Indo-Pacific beach star, Archaster typicus (Echinodermata; Asteroidea). Marine Biology, 158(3), 639-648.

. Adult forms which are generally larger then migrate to sandy shores with greater exposure due to decrease predation pressure and to reduce intraspecific competition

Footnote Macro

Bos, A., Gumanao, G., van Katwijk, M., Mueller, B., Saceda, M. & Tejada, R., 2010. Ontogenetic habitat shift, population growth, and burrowing behavior of the Indo-Pacific beach star, Archaster typicus (Echinodermata; Asteroidea). Marine Biology, 158(3), 639-648.

. They are commonly found in shallow habitats, though some records have found them in depths up to 30m

Footnote Macro

Clark, A. M. & Rowe, F. W. E., 1971. Monograph of shallow-water Indo-West Pacific echinoderms. London, Trustees of the British Museum (Natural History).

.

In Singapore particularly, no distinct ontogenetic shifts have been recorded. They are known to cluster within sandy lagoons exposed to tidal influences, with preference for shelter such as by breakwaters. No known associations for juveniles with mangroves have been noted, though this could potentially be due to the lack of a continuum between mangroves to sandy shores in our coastal habitats. Some sea stars have been seen within spoon seagrass meadows (Halophila ovalis).



Distribution

This sea star is found in many parts of the Indo-Pacific region, with localities sighted marked in the map below

Footnote Macro

“Georeferenced Data: Map of global distribution of Archaster typicus” by Global Biodiversity Information Facility. Archaster typicus, 2015. URL: http://www.gbif.org/species/2271315(accessed on 11 Nov 2015)

.

Distribution of Archaster typicus in the Indo-West Pacific (Adapted from Global Biodiversity Information Facility, 2015

Footnote Macro

“Georeferenced Data: Map of global distribution of Archaster typicus” by Global Biodiversity Information Facility. Archaster typicus, 2015. URL: http://www.gbif.org/species/2271315(accessed on 11 Nov 2015)

)


The sand-sifting sea star can be found on many shores in Singapore as well; known observations of this sea star are shown the map below

Footnote Macro

“Echinoderms on Singapore shores” by Ria Tan. Wildsingapore fact sheets, 2008. URL: http://www.wildsingapore.com/wildfacts/echinodermata/echinodermindex.htm (accessed on 11 Nov 2015)

. As noted from the map, most of the populations of the sea star are found within the Southern islands, with some additional observations on the Southern mainland shores near Tanah Merah

Footnote Macro

“Echinoderms on Singapore shores” by Ria Tan. Wildsingapore fact sheets, 2008. URL: http://www.wildsingapore.com/wildfacts/echinodermata/echinodermindex.htm (accessed on 11 Nov 2015)

. Past observations have also included Chek Jawa, though after a massive death event in 2007, no sand-sifting sea stars have been noted till date

Footnote Macro

Loh, K. S., 2008. Life and Death at Chek Jawa. Nature Watch, Oct - Dec 2008: 18-23.

.

Distribution of Archaster typicus in Singapore (Adapted from Global Biodiversity Information Facility, 2015

Footnote Macro

“Georeferenced Data: Map of global distribution of Archaster typicus” by Global Biodiversity Information Facility. Archaster typicus, 2015. URL: http://www.gbif.org/species/2271315(accessed on 11 Nov 2015)

& WildSingapore, 2015

Footnote Macro

“Echinoderms on Singapore shores” by Ria Tan. Wildsingapore fact sheets, 2008. URL: http://www.wildsingapore.com/wildfacts/echinodermata/echinodermindex.htm (accessed on 11 Nov 2015)

)




Physical Characteristics


Size

Generally, sea stars are compared using R, the length of the arm from tip to the mouth and sometimes r, the length of the integument between two arms to the mouth. R can then be measured and taken as a mean of all arms, or taken to be the arm directly opposite the madreporite based off the Carpenter orientation

Footnote Macro

Lawrence, J. M., 2013. The Asteroid Arm in Lawrence, J. Starfish (pp. 15-23) Baltimore, John Hopkins University Press.

. This species possesses a small central disc, with mean arm length, R, from 4-60mm in Japan

Footnote Macro

Mukai, H., Nishihira, M., Kamisato, H. & Fujimoto Y., 1986. Distribution and abundance of the sea-star Archaster typicus in Kabira Cove, Ishigaki Island, Okinawa. Bulletin of Marine Science, 38(2): 366-383.

 to 2-81mm in Philippines

Footnote Macro

Bos, A., Gumanao, G., van Katwijk, M., Mueller, B., Saceda, M. & Tejada, R., 2010. Ontogenetic habitat shift, population growth, and burrowing behavior of the Indo-Pacific beach star, Archaster typicus (Echinodermata; Asteroidea). Marine Biology, 158(3), 639-648.

 from a few studies that looked at the size of this species.

In the Singapore Red Data Book however, the common sea star is noted to be much larger in Singapore than compared to the same species found in other countries

Footnote Macro

Davison, G. W. H., Ng, P. K. L. & Ho, H. C., 2008. The Singapore Red Data Book. 2nd edition. Nature Society (Singapore), Singapore.

. This arm length of this sea star, R, ranges from 25mm to 121mm. Furthermore, there appears to be significant size differences between islands, with the specimens found on Pulau Subar Laut (Big Sisters' Island) appearing significantly larger than on other islands surveyed, out of the size range described above.

Sexing

The common sea star has two separate sexes, with distinct male and female individuals

Footnote Macro

P. K. L., Corlett, R. & Tan, H., 2011. Singapore Biodiversity. Singapore, Editions Didier Millet in association with Raffles Museum of Biodiversity Research

. In general, it is impossible to tell the difference among the two sexes for this species without examination of gonads.

Even with the examination of gonads, several studies have noted differences within the gonads of the sea star, with spermatocytes having a creamier colouration and consistency than ova. Through their pseudocopulatory behaviour, several studies have also noted that the bottom individual to be male while the ones above are likely female. Females are also seen to be significantly larger than males, though they are indistinguishable without further examination.



Biology

Behaviour

The common sea star exhibits many interesting behaviours both different and alike with regards to other sea stars, which will be elaborated upon.

Movement

The sand-sifting sea star moves using its tube feet, being capable of reaching speeds of 15.1 cm min-1 up to 72.2 cm min-1

Footnote Macro

Run, J.Q., Chen, C. P., Chang, K. H. & Chia, F. S., 1988. Mating behaviour and reproductive cycle of Archaster typicus(Echinodermata; Asteroidea). Marine Biology, 99: 247-253.

Footnote Macro

Muller, B., Bos, A. R., Graf, G. & Gumanao, G. S., 2011. Size-specific locomotion rate and movement pattern of four common Indo-Pacific sea stars (Echinodermata; Asteroidea). Aquatic Biology, 12: 157-164.

. The rigid body can become more flexible through the water vascular system within, allowing it to contort its body to climb onto steeper surfaces or to flip itself over when overturned

Footnote Macro

Lawrence, J. M., 2013. The Asteroid Arm in Lawrence, J. Starfish (pp. 15-23) Baltimore, John Hopkins University Press.

. It raises the tips of its arms, using the sensory tube feet at the tip of the arms to sense the environment

Footnote Macro

Run, J.Q., Chen, C. P., Chang, K. H. & Chia, F. S., 1988. Mating behaviour and reproductive cycle of Archaster typicus(Echinodermata; Asteroidea). Marine Biology, 99: 247-253.

. These can be seen in the video embedded below (Do note the likely misidentification of A. typicus as A. angulatus, though both species have similar movement characteristics).

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A different view of the movement over a glass surface is shown below to highlight how the numerous tube feet work together to move the sea star.

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It can also bury itself with the help of its tube feet and inferomarginal spines, similar to Astropecten spp. despite the different morphology of the tube feet

Footnote Macro

Ventura, C. R. R., 2013. Astropecten in Lawrence, J. Starfish (pp. 101-108) Baltimore, John Hopkins University Press.

Footnote Macro

Hennebert, E., Jangoux, M. & Flammang, P., 2013. Functional Biology of Asteroid Tube Feet in Lawrence, J. Starfish (pp. 24-36) Baltimore, John Hopkins University Press.

. This is likely to prevent desiccation and avoid predation while the tide recedes

Footnote Macro

Bos, A., Gumanao, G., van Katwijk, M., Mueller, B., Saceda, M. & Tejada, R., 2010. Ontogenetic habitat shift, population growth, and burrowing behavior of the Indo-Pacific beach star, Archaster typicus (Echinodermata; Asteroidea). Marine Biology, 158(3), 639-648.

.

Feeding

This sea star is a detritivorous species that feeds extraorally, everting its green stomach through its mouth over sediment

Footnote Macro

P. K. L., Corlett, R. & Tan, H., 2011. Singapore Biodiversity. Singapore, Editions Didier Millet in association with Raffles Museum of Biodiversity Research

. It then takes in detritus and other organic materials found on or within the benthos with the stomach, before ejecting any remaining sediment grains

Footnote Macro

Bos, A., Gumanao, G., van Katwijk, M., Mueller, B., Saceda, M. & Tejada, R., 2010. Ontogenetic habitat shift, population growth, and burrowing behavior of the Indo-Pacific beach star, Archaster typicus (Echinodermata; Asteroidea). Marine Biology, 158(3), 639-648.

.

Reproduction

The common sea star has a very interesting pseudocopulatory mating behaviour only known to itself, the closely related A. angulatus, and an Antarctic brooding species of sea star Neosmilaster georgianus 

Footnote Macro

Run, J.Q., Chen, C. P., Chang, K. H. & Chia, F. S., 1988. Mating behaviour and reproductive cycle of Archaster typicus(Echinodermata; Asteroidea). Marine Biology, 99: 247-253.

Footnote Macro

Keesing, J. K., Graham, F., Irvine, T. R. & Crossing, R., 2011. Synchronous aggregated pseudo-copulation of the sea star Archaster angulatus Müller & Troschel, 1842 (Echinodermata: Asteroidea) and its reproductive cycle in south-western Australia. Marine Biology, 158: 1163-1173.

. This means that the sea stars exhibit behaviour similar to copulation but do not involve a sexual union. In this mating behaviour, the male sea star contacts with female through the tip of the arms, using chemical cues to identify the sex of the sea star in contact

Footnote Macro

Run, J.Q., Chen, C. P., Chang, K. H. & Chia, F. S., 1988. Mating behaviour and reproductive cycle of Archaster typicus(Echinodermata; Asteroidea). Marine Biology, 99: 247-253.

. After which, the male sea star climbs on top of the female, into a position where their arms alternate

Footnote Macro

Run, J.Q., Chen, C. P., Chang, K. H. & Chia, F. S., 1988. Mating behaviour and reproductive cycle of Archaster typicus(Echinodermata; Asteroidea). Marine Biology, 99: 247-253.

. During the release of gametes, the male sea star shifts its arms so that both the male and female's goniopores are allowed to release their gametes into the water column above

Footnote Macro

Run, J.Q., Chen, C. P., Chang, K. H. & Chia, F. S., 1988. Mating behaviour and reproductive cycle of Archaster typicus(Echinodermata; Asteroidea). Marine Biology, 99: 247-253.

. The behaviour sequence can be seen in the images below.

Mating behaviour sequence of Archaster typicus (Adapted from Run et al., 1988

Footnote Macro

Run, J.Q., Chen, C. P., Chang, K. H. & Chia, F. S., 1988. Mating behaviour and reproductive cycle of Archaster typicus(Echinodermata; Asteroidea). Marine Biology, 99: 247-253.

)



This pseudocopulatory behaviour is a form of aggregation, where members of the same species come together to increase fertilization chances due to the vast nature of the oceans

Footnote Macro

Mercier, A. & Hamel, J., 2013. Reproduction in Asteroidea in Lawrence, J. Starfish (pp. 101-108) Baltimore, John Hopkins University Press.

. This is known to occur in many species of echinoderms as well as other marine invertebrates

Footnote Macro

Mercier, A. & Hamel, J., 2013. Reproduction in Asteroidea in Lawrence, J. Starfish (pp. 101-108) Baltimore, John Hopkins University Press.

.

Relationships with Other Species

The common sea star plays host to a few known parasites, including the Eulimidae snails, a family that parasitises various species within Echinodermata

Footnote Macro

“Ulimid snails” by Ria Tan. Wildsingapore fact sheets, Aug 2012. URL: http://www.wildsingapore.com/wildfacts/mollusca/gastropoda/eulimidae/eulimidae.htm (accessed on 11 Nov 2015)

Footnote Macro

Waren A., 1983. A Generic Revision of the Family Eulimidae (Gastropoda, Prosobranchia). Journal of Molluscan Studies, 49(Supplement 13): 1-96.

Footnote Macro

“P is for Parasitic Snail! Enter: The Eulimidae!” by Christopher Mah. The Echinoblog, 3 Jun 2014. URL: http://echinoblog.blogspot.sg/2014/06/p-is-for-parasitic-snail-enter-eulimidae.html (accessed on 11 Nov 2015)

. There have been reports of tiny white Eulimid snails found on the aboral surface of common sea stars in Singapore

Footnote Macro

“Ulimid snails” by Ria Tan. Wildsingapore fact sheets, Aug 2012. URL: http://www.wildsingapore.com/wildfacts/mollusca/gastropoda/eulimidae/eulimidae.htm (accessed on 11 Nov 2015)

, where they insert their proboscis into the tissues of the sea star to feed on the fluids inside

Footnote Macro

Waren A., 1983. A Generic Revision of the Family Eulimidae (Gastropoda, Prosobranchia). Journal of Molluscan Studies, 49(Supplement 13): 1-96.

Footnote Macro

“P is for Parasitic Snail! Enter: The Eulimidae!” by Christopher Mah. The Echinoblog, 3 Jun 2014. URL: http://echinoblog.blogspot.sg/2014/06/p-is-for-parasitic-snail-enter-eulimidae.html (accessed on 11 Nov 2015)

. The identity of these species and the effects of its parasitism on the common sea stars have not been investigated.



Eulimid snail on Archaster typicus (Image by Ria Tan, 2011

Footnote Macro

“Parasitic Ulimid snails (Family Eulimidae) on Common sea star (Archaster typicus)” by Ria Tan. 30 Aug 2011. URL: https://www.flickr.com/photos/wildsingapore/7891993886/ (accessed on 11 Nov 2015)

)




Closeup of Eulimid snail on Archaster typicus (Image by Ria Tan, 2010

Footnote Macro

“Oil-slicked Tanah Merah: Parasitic Ulimid snail (Family Eulimidae) on Common sea star (Archaster typicus)” by Ria Tan. 21 Dec 2010. URL: https://www.flickr.com/photos/wildsingapore/5299543199/ (accessed on 11 Nov 2015)

)



A black or brown polychaete worm has also been seen in the mouth of the sea star, though what relationship exists between the two species are unknown. It is unlikely that the sea star is preying on the worm.

Polychaete worm in mouth of Archaster typicus (Image by Samuel Chan, 2015)





Conservation

Threats

The largest threat facing sea stars in general, is the collection of specimens for the marine curio trade. A few species known to be traded include A. typicus, the Knobbly Sea Star (//Protoreaster nodosus//) and the Blue Sea Star (Linckia laevigata)

Footnote Macro

Bos, A., Gumanao, G., van Katwijk, M., Mueller, B., Saceda, M. & Tejada, R., 2010. Ontogenetic habitat shift, population growth, and burrowing behavior of the Indo-Pacific beach star, Archaster typicus (Echinodermata; Asteroidea). Marine Biology, 158(3), 639-648.

. These are collected en masse in certain places especially in Southeast Asia, depleting large numbers of mature adults that can have large impacts on their populations

Footnote Macro

Bos, A., Gumanao, G., van Katwijk, M., Mueller, B., Saceda, M. & Tejada, R., 2010. Ontogenetic habitat shift, population growth, and burrowing behavior of the Indo-Pacific beach star, Archaster typicus (Echinodermata; Asteroidea). Marine Biology, 158(3), 639-648.

.


Trade of Echinoderm species in Sydney (Image by Juria Toramae, 2015)


Similarly, other species of sea stars are collected for food or for traditional medicine in certain countries, though little nutritional value or medicinal effects are known, where they can be treated as delicacies

Footnote Macro

“People eating starfish” by Christopher Mah. The Echinoblog, 16 Apr 2008. URL: http://echinoblog.blogspot.sg/2008/04/people-eating-starfish.html (accessed on 11 Nov 2015)

. An online blog even showcases starfishes as part of China Qingdao's street food culinary scene, see

Footnote Macro

"Starfish" by Frank Kasell. A Field Guide to Chinese Street Food, 28 Jul 2012. URL: http://www.chinesestreetfood.com/2012/07/starfish.html (accessed on 11 Nov 2015)

. Together, these problems take a toll on the populations of the targeted species of sea stars. The largest problem of these are that information on the size and trade of these sea stars are relatively unknown and unregulated. Without information, it is hard to inform what effects these practices are having on the natural populations of the sea stars and the ecosystem.

Status

The International Union for Conservation of Nature (IUCN) publishes a Red List that confers a conservation status on species based on threat status and population size

Footnote Macro

“The IUCN Red List of Threatened Species” by the International Union of for Conservation of Nature. IUCN, 2015. URL: www.iucnredlist.org/ (accessed on 11 Nov 2015)

A. typicus is not listed as data deficient under the IUCN Red List

Footnote Macro

“The IUCN Red List of Threatened Species” by the International Union of for Conservation of Nature. IUCN, 2015. URL: www.iucnredlist.org/ (accessed on 11 Nov 2015)

, similar to many other marine invertebrate species where information is very limited regarding their population and threats.

In the Singapore Red Data Book, A. typicus is thought to be Vulnerable in Singapore, facing threats of habitat destruction, largely due to the effects of land reclamation on our shores

Footnote Macro

Davison, G. W. H., Ng, P. K. L. & Ho, H. C., 2008. The Singapore Red Data Book. 2nd edition. Nature Society (Singapore), Singapore.

. The effects of pronounced salinity and temperature changes may also have large impacts on their population and recovery

Footnote Macro

Loh, K. S., 2008. Life and Death at Chek Jawa. Nature Watch, Oct - Dec 2008: 18-23.

.



Taxonomy

Archaster typicus was originally described by Müller and Troschel in 1840 as the type specimen for the genus Archaster 

Footnote Macro

“Archiv für Naturgeschichte” by the Biodiversity Heritage Library. The Biodiversity Heritage Library, 2015. URL: http://www.biodiversitylibrary.org/page/7203199#page/333/mode/1up (accessed on 11 Nov 2015)


. The original description from the Archiv für Naturgeschichte is shown below.


Original description of Archaster genus and Archaster typicus by Müller & Troschel (Adapted from Biodiversity Heritage Library, 2015

Footnote Macro

“Archiv für Naturgeschichte” by the Biodiversity Heritage Library. The Biodiversity Heritage Library, 2015. URL: http://www.biodiversitylibrary.org/page/7203199#page/333/mode/1up (accessed on 11 Nov 2015)

)



It was originally placed in an unnamed family before being placed in Archasteridae by Viguier in 1878

Footnote Macro

Sukarno, M. & Jangoux, M., 1977. Révision du genre Archaster Müller et Troschel (Echinodermata, Asteroidea: Archasteridae). Revue de Zoologie Africaine, 91(4): 817-844

. Till date, Archasterremains as the sole genus within Archasteridae with only 3 species known after redescription by Sukarno & Jangoux

Footnote Macro

Sukarno, M. & Jangoux, M., 1977. Révision du genre Archaster Müller et Troschel (Echinodermata, Asteroidea: Archasteridae). Revue de Zoologie Africaine, 91(4): 817-844

 - A. typicus 

Footnote Macro

Archaster typicus Müller & Troschel, 1840” by Christopher Mah. WoRMS taxon details, 2015. URL: http://www.marinespecies.org/aphia.php?p=taxdetails&id=213119 (accessed on 11 Nov 2015)

A. angulatus Müller & Troschel, 1842

Footnote Macro

Archaster angulatus Müller & Troschel, 1842” by Christopher Mah. WoRMS taxon details, 2015. URL: http://www.marinespecies.org/aphia.php?p=taxdetails&id=213121 (accessed on 11 Nov 2015)

, and A. lorioli Sukarno & Jangoux, 1977

Footnote Macro

Archaster lorioli Sukarno & Jangoux, 1977” by Christopher Mah. WoRMS taxon details, 2015. URL: http://www.marinespecies.org/aphia.php?p=taxdetails&id=213122 (accessed on 11 Nov 2015)

.

The type specimen of A. typicus, part of the Leiden collection, has been lost

Footnote Macro

Jangoux, M. & de Ridder, C., 1987. Annotated catalogue of recent Echinoderm type specimens in the collection of the Rijksmuseum van Natuurlijke Historie at Leiden. Zoologische Mededelingen, 61(6): 79-96.

. Another source states that two syntypes have also been designated, with one is located in India

Footnote Macro

“GBIF 911916205 Specimen of Archaster typicus” by Global Biodiversity Information Facility. Global Biodiversity Information Facility, 2015. URL: http://www.gbif.org/occurrence/911916205 (accessed on 11 Nov 2015)

 and one in Indonesia

Footnote Macro

“GBIF 911916206 Specimen of Archaster typicus” by Global Biodiversity Information Facility. Global Biodiversity Information Facility, 2015. URL: http://www.gbif.org/occurrence/911916206 (accessed on 11 Nov 2015)

. However, the certainty of these specimens being either the holotype or the syntypes are to be questioned till more information arises. 

Synonyms

The following species were junior synonyms of Archaster typicus and have since been consolidated under this name

Footnote Macro

Archaster typicus Müller & Troschel, 1840” by Christopher Mah. WoRMS taxon details, 2015. URL: http://www.marinespecies.org/aphia.php?p=taxdetails&id=213119 (accessed on 11 Nov 2015)

.
Archaster nicobaricus Behn in Möbius, 1859
Astropecten stellaris Gray, 1840

DNA Barcode

Archaster typicus COI Barcode (Adapted from BOLD Systems, 2014)

Footnote Macro

"Record Details For GBEH0091-06" by BOLD Systems. Public Data Portal, Specimen Record, 2014. URL: http://www.boldsystems.org/index.php/Public_RecordView?processid=GBEH0091-06 (accessed on 11 Nov 2015)




Phylogeny

No phylogenetic study has been done of the Archaster species within Family Archasteridae, likely due to the small number of species present. It is also likely important to verify any potential differences between DNA sequences amongst different regions and within the different Archaster species through means of COI or other sequences as the sequences online are largely represented by only one specimen each, especially with the difference in size amongst species from different regions.

Many different studies have constructed phylogenetic trees of major clades in the Class Asteroidea, with little agreement on what relationships holds within the class and orders

Footnote Macro

Mah, C. L. & Blake, D. B., 2012. Global Diversity and Phylogeny of the Asteroidea (Echinodermata). PLoSONE, 7(4): e35644.

44]. Certain orders within the Class Asteroidea are also not monophyletic, with disagreements on the relationships between the different orders and families [44]. This is partially seen below, in a constructed tree from the results of previous studies by Mah and Foltz

Footnote Macro

Mah, C. L. & Blake, D. B., 2012. Global Diversity and Phylogeny of the Asteroidea (Echinodermata). PLoSONE, 7(4): e35644.

. Thus, much more phylogenetic work needs to be done on Asteroidea to resolve more fine-scale details between the different taxa.

Summary Phylogenetic Tree of Asteroidea with bold arrow showing position of Archasteridea and dotted arrows showing positions of highlighted families (Adapted from Mah & Foltz, 2012)

Footnote Macro

Mah, C. L. & Blake, D. B., 2012. Global Diversity and Phylogeny of the Asteroidea (Echinodermata). PLoSONE, 7(4): e35644.



While there are still many unknowns, some information can still be gleaned from the tree. It is most interesting to note that despite its similarities to the Astropecten genus within the Astropectinidae family, these two genera are actually further apart, possibly indicating a case of convergent evolution into the forms for their sandy habitat

Footnote Macro

Gale, A. S., 2013. Phylogeny of the Asteroidea in Lawrence, J. Starfish (pp. 3-14) Baltimore, John Hopkins University Press.

. It is more closely related to Acanthasteridae (Acanthaster planci), Oreasteridae (Protoreaster nodosus) and Asteropseidae, notably families with many species from the tropical region

Footnote Macro

Mah, C. L. & Blake, D. B., 2012. Global Diversity and Phylogeny of the Asteroidea (Echinodermata). PLoSONE, 7(4): e35644.

.

Amongst the different species compared above, Archasteridae appears to be more closely related to Oreasteridae with both being from the Order Valvatida and much more distantly related to Luidiidae and Astropectinidae from the Order Paxillosida.



Glossary

This glossary helps defines many of the specific terms regarding Asteroidea.
Aboral - Surface opposite the mouth
Goniopore - Openings along the arm that allow for the release of gametes
Inferomarginal spine - Spines along the inferomarginal plates, usually the bottom plate on the side of the arm
Integument - Concave region between two arms
Madreporite - Calcerous opening in sea stars used to filter water, acting as a valve system to control pressure and water flow between the sea star and environment
Oral - Surface alongside the mouth
Pentaramous - 5 point radially symmetrical



Literature and References

This species page contains additional information from the honours project of the author yet unpublished. Please contact Samuel at samuelchan@u.nus.edu for more information.

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This page was authored by Chan Yong Kit Samuel
Last curated on 2015