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editThe Echinothuriidae are a family of sea urchins in the order Echinothurioida. These echinoderms are typical of the Indo-Pacific these softer-bodied "leather urchins" are found from abyssal to shallow littoral zones in the ocean.[1] While common in the Indo-Pacific these colourful urchins can be found across the world. Some individuals within Echinothuriidae such as species in the genus Asthenosoma are also known as "fire urchins" due to their bright colours and painful, venomous sting.
Typical of the Indo-pacific the family Echinothuriidae, are softer-bodied echinoderms that inhabit abyssal zones and shallow littoral areas across the world.
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editThey are most often found in the Indo-Pacific, although they have been observed worldwide, and are among the most common urchins inhabiting deep marine environments.[1] While they are most common at great depths (more than 200m below the surface) the genus Asthenosoma has been known to inhabit shallow zones.[1]
The order to which they belong, the Echinothurioida, is defined by the compound plates which cover the ambulacra and the peristome.[2]
Echinothuriidae is separate from other members in their grouping due to having a softer test comparatively.[3] Morphologically they are different but reproductively it is hard to tell visually without investigation. The reproductive habit of echinothuriidae is debated, from pelagic lecithotrophs to direct development, sperm from shallow water echinoid specimens demonstrate a highly conserved morph with minimal variation from species to species.[3] But much of echinothuriidae reproductive biology is restricted to a handful of deep-sea observations of abyssal deep-sea specimens.[3] The deep sea echinothurrid acrosomal vesicles and sperm nuclei are morphologically different from other echinoderm reproductive structures, abyssal echinothuriids showcase far more elongate sperm heads compared to littoral species.[3]
Members of the Echinothuriidae have been observed to attached themselves to living and dead stony corals (Order: Scleractinia) allowing them a degree of protection from crustaceans and fish that feed on urchins. When the threat of predators is low they can be found assembling closely together which likely provides advantages for reproduction and feeding.[4] The levels at which they seek refuge in the coral will also change based on predator prescence as the tend to shift higher on the structures in the prescence of decapod or crustacean predators, while an increase in fish will lead to an increase in urchins closer to the sediment.[4]
Like other echinoids, members of the Echinothuriidae, namely those belonging to the genus Araeosoma, have been known to prey on or consume the remains of crinoids. Although the extent to which they are capable of successfully hunting the crinoids is unknown, experiments done in captivity have this predator-prey interaction as a definite possibility in nature.[5] Gut contents have been found to also contain pieces of corals, crustacean exoskeleton, bryozoans, polychaetes, foraminifera, sponges, and a variety of other invertebrate elements. The high presence of sediment in the gut along with these elements indicates a scavenger like feeding strategy as the pick up deceased material from the sediment.[5]
Some members of the family, specifically those belonging to the genus Asthenosoma, produce the largest eggs of any known echinoid. The embryo and larva develop slowly while floating under the water surface. The larvae are completely lecithotrophic, meaning their yolk sustains them for the duration of their growth.[6]
References
editThree new species and two new records of Echinothuriidae (Echinodermata: Echinothurioida) from seamounts in the Northwest Pacific Ocean: Diversity, phylogeny and biogeography of deep-sea echinothuriids https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2022.1036914/full[1]
predation has no competition [4]
classification of echinoids[2]
Predation on feather stars by regular echinoids as evidenced by laboratory and field observations and its paleobiological implications[5]
Modified Sperm Ultrastructure in Four Species of Soft Bodied Echinoids (Echinodermata: Echinothuriidae) From the Bathyal Zone of the Deep Sea[3]
development of the echiothurid sea urchin Asthenosoma ijimai[6]
- 1 2 3 4 Zheng, Wanrui; Sun, Shao’e; Sha, Zhongli; Xiao, Ning (2022-12-09). "Three new species and two new records of Echinothuriidae (Echinodermata: Echinothurioida) from seamounts in the Northwest Pacific Ocean: Diversity, phylogeny and biogeography of deep-sea echinothuriids". Frontiers in Marine Science. 9. doi:10.3389/fmars.2022.1036914. ISSN 2296-7745.
{{cite journal}}: CS1 maint: unflagged free DOI (link) - 1 2 Durham, J. Wyatt; Melville, R. V. (1957). "A Classification of Echinoids". Journal of Paleontology. 31 (1): 242–272. ISSN 0022-3360.
- 1 2 3 4 5 Eckelbarger, Kevin J.; Young, Craig M.; Cameron, J. Lane (1989). "Modified Sperm Ultrastructure in Four Species of Soft-Bodied Echinoids (Echinodermata: Echinothuriidae) From the Bathyal Zone of the Deep Sea". The Biological Bulletin. 177 (2): 230–236. doi:10.2307/1541938. ISSN 0006-3185.
- 1 2 3 Stevenson, Angela; Mitchell, Fraser J. G.; Davies, Jaime S. (2015). "Predation has no competition: factors influencing space and resource use by echinoids in deep-sea coral habitats, as evidenced by continuous video transects". Marine Ecology. 36 (4): 1454–1467. doi:10.1111/maec.12245. ISSN 1439-0485.
- 1 2 3 Stevenson, Angela; Gahn, Forest J.; Baumiller, Tomasz K.; Sevastopulo, George D. (2017-05). "Predation on feather stars by regular echinoids as evidenced by laboratory and field observations and its paleobiological implications". Paleobiology. 43 (2): 274–285. doi:10.1017/pab.2016.39. ISSN 0094-8373.
{{cite journal}}: Check date values in:|date=(help) - 1 2 Amemiya, S.; Tsuchiya, T. (1979-03-01). "Development of the echinothurid sea urchin Asthenosoma ijimai". Marine Biology. 52 (1): 93–96. doi:10.1007/BF00386862. ISSN 1432-1793.