Leptasterias Explained

Leptasterias is a genus of starfish in the family Asteriidae. Members of this genus are characterised by having six arms although five-armed specimens sometimes occur. L. muelleri is the type species. The taxonomy of the genus is confusing and Leptasterias hexactis seems to be a species complex. Some species brood their eggs.[1]

Description and biology

Leptasterias is a genus of starfish in the family Asteriidae and order Forcipulatida.[2] It is often noted that members in the genus have six arms,[3] however, occasionally five-armed specimen can occur. They are also characterized by having several cryptic species complexes.[4] They are often found in the waters of Alaska to central California in rocky intertidal and subtidal habitats. They are typically small in size, measuring less than 6 cm  from ray tip to ray tip. They mature around the age of two. They are known for being lecithotrophic, providing the embryo with no nutrition other than the yolk in its egg. The females will brood their young under their rays until they have fully developed and are capable of crawling away. Because of the way they are bred and the fact that they are smaller creatures, it is difficult for the sea stars to disperse to new areas. Rather than crawling long distances, the sea stars will attach to macroalgae or other floating organisms and substrate, allowing them to be dispersed farther distances. However, this method of dispersal does not happen frequently. Leptasterias can also be used as an indicator species as they are not very able to move far from their habitat and are susceptible to local selection pressures like algal blooms and disease outbreaks. To do this, it is important to identify the certain species of Leptasterias in order to accurately observe changing distributions, abundances, and population health. The cryptic complexes also play a part in determining data for monitoring ecological effects of disastrous events and other environmental stressors.

Habitat

Leptasterias are found in intertidal waters. They spend their time under rocks or in rock pools where the shore is fairly exposed.[5] Leptasterias can typically be found under rocks during the fall months. During this time, the starfish will reproduce and the rock exterior provides protection for the new brood. During the spring months is when Leptasterias can be found in the rock pools, on the surface of rocks. The rocks that Leptasterias inhabit are covered in algae which also protect the starfish as the algae remains moist and allows the starfish to avoid dehydration.[6] Young are found in the rocky substrates in the shallow water while adults usually venture out to greater depths.[7] [8] They can withstand depths up to 800 meters and can be found globally in the North Sea below Norway, the North Atlantic between Iceland and Greenland, and the northeast coast and Pacific coast of The United States.[9]

Reproduction

The reproduction period for Leptasterias begins around the months of October or November and lasts until January.[10] During this time, it is important for the starfish to be beneath rocks due to the possibility of the tide to disperse the sperm elsewhere.[11] Leptasterias do not partake in actual sexual intercourse, but it is essential for the starfish to be in close proximity of each other to better ensure reproductive success. The males ten gonads release sperm that settles on the bottom, beneath the rock. The male spawning period lasts for about 2 hours in order to ensure there are viable sperm present for the female eggs. Females begin releasing eggs through their ten genital papillae. The eggs come out yellow and yolky at a rate of approximately one egg per minute.[12] Once in contact with the sperm, the female then takes the eggs with her tube feet and forms a brood pouch by arching her arms to provide a protective space to place her eggs. Leptasterias do not go through a larval stage. Instead, the embryos develop and leave the mother after the first three pairs of tube feet have appeared. The mother usually protects her young for five to six months.[13]

Species

The World Register of Marine Species lists the following species:

Notes and References

  1. Book: Lambert, Philip . Sea stars of British Columbia, Southeast Alaska, and Puget Sound . 2001 . 117–126 . UBC Press . 9780774808255 .
  2. Foltz . D. W. . Nguyen . A. T. . Kiger . J. R. . Mah . C. L. . 2008-03-18 . Pleistocene speciation of sister taxa in a North Pacific clade of brooding sea stars (Leptasterias) . Marine Biology . 154 . 3 . 593–602 . 10.1007/s00227-008-0952-9 . 37515531 . 0025-3162.
  3. Shirley . T. C. . Stickle . W. B. . 1982 . Responses of Leptasterias hexactis (Echinodermata: Asteroidea) to low salinity . Marine Biology . 69 . 2 . 155–163 . 10.1007/bf00396895 . 87024550 . 0025-3162.
  4. Melroy . Laura M. . Cohen . C. Sarah . 2021-03-04 . Temporal and spatial variation in population structure among brooding sea stars in the genus Leptasterias . Ecology and Evolution . 11 . 7 . 3313–3331 . 10.1002/ece3.7283 . 33841786 . 8019026 . 2045-7758.
  5. O'BRIEN . FRANCIS . 1972-01-01 . SOME ASPECTS OF THE BIOLOGY OF A BROODING STARFISH, LEPTASTERIAS LITTORALIS (STIMPSON) 1853 . Doctoral Dissertations.
  6. Web site: MarLIN - The Marine Life Information Network - Northern starfish (Leptasterias (Leptasterias) muelleri) . 2022-04-13 . www.marlin.ac.uk.
  7. Rochette . R . Hamel . J-F . Himmelman . JH . 1994 . Foraging strategy of the asteroid Leptasterias polaris: role of prey odors, current and feeding status . Marine Ecology Progress Series . 106 . 93–100 . 10.3354/meps106093 . 0171-8630. free .
  8. Gaymer . Carlos F. . Himmelman . John H. . Johnson . Ladd E. . October 2001 . Distribution and feeding ecology of the seastars Leptasterias polaris and Asterias vulgaris in the northern Gulf of St Lawrence, Canada . Journal of the Marine Biological Association of the United Kingdom . 81 . 5 . 827–843 . 10.1017/S0025315401004660 . 85646455 . 0025-3154.
  9. Hrincevich . Adam W. . Rocha-Olivares . Axayácatl . Foltz . David W. . June 2000 . Phylogenetic Analysis of Molecular Lineages in a Species-Rich Subgenus of Sea Stars (Leptasterias Subgenus Hexasterias) . American Zoologist . 40 . 3 . 365–374 . 10.1093/icb/40.3.365 . 0003-1569.
  10. Menge . Bruce A. . 1975 . Brood or broadcast? The adaptive significance of different reproductive strategies in the two intertidal sea stars Leptasterias hexactis and Pisaster ochraceus . Marine Biology . 31 . 1 . 87–100 . 10.1007/bf00390651 . 67800760 . 0025-3162.
  11. CHIA . FU-SHIANG . Brooding Behavior of a Six-Rayed Starfish, Leptasterias hexactis . June 1966 . The Biological Bulletin . 130 . 3 . 304–315 . 10.2307/1539738 . 1539738 . 0006-3185.
  12. January 1929 . V. Skeletal development in Arbacia, Echinarachnius and Leptasterias . Philosophical Transactions of the Royal Society of London. Series B, Containing Papers of a Biological Character . 217 . 440–449 . 289–334 . 10.1098/rstb.1929.0005 . 0264-3960. free .
  13. Hamel . J. F. . Mercier . A. . February 1995 . Prespawning Behavior, Spawning, and Development of the Brooding Starfish Leptasterias polaris . The Biological Bulletin . 188 . 1 . 32–45 . 10.2307/1542065 . 1542065 . 29281304 . 0006-3185.

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