Ophiomastix venosa

Ophiomastix venosa was initially discovered and described in 1851 by Peters, W., a German zoologist.{{Cite book |last=Harnack |first=Adolf von |url=https://doi.org/10.5962/bhl.title.1839 |title=Geschichte der Königlich Preussischen Akademie der Wissenschaften zu Berlin, im Auftrage der Akademie bearb |last2=Köhnke |first2=Otto |date=1900 |publisher=Reichsdruckerei |location=Berlin}} Since the initial description of O. venosa, few published observations have occurred; the conservational status of this species is not well understood because of this reason. The sightings of Ophiomastix venosa occur throughout the coastal regions of the Indo-Pacific, and have been absent in all other oceanic/coastal regions.

Ophiomastix venosa are morphologically distinct for various reasons. Brittle stars, including O. venosa, have unique body plans; they exhibit pentaradial symmetry (five-point symmetry), with five 'serpent-like' arms that connect to a distinct central disk. Each of the arms are covered in spines that aid in locomotion, feeding, and defense.{{Cite web |last=Burgess |first=Danny |last2=Eagleston |first2=Angela |date=March 28, 2018 |title=The brittle stars embody nature's fragility...and resilience |url=https://ecology.wa.gov/blog/march-2018/eyes-under-puget-sound-critter-of-the-month-the |url-status=live |website=Department of Ecology State of Washington}} The Ophiomastix venosa species is recognized by their enlarged upper arm spines, which are covered by a thickened epithelium, and the absence of or extremely minute scales on their central disk.{{Cite web |last=Devaney |first=Dennis M. |title=A Review of the Genus Ophiomastix (Ophiuroidea: Ophiocomidae) |url=https://scholar.archive.org/work/k35hrvtncrdozpuef53bkecloq/access/wayback/http://micronesica.org/sites/default/files/devaney-8.pdf |url-status=live}} O. venosa exhibit claviform arm spines, meaning that specialized spines along the perimeter of their arms are enlarged and thickened. These enlarged arm spines may be described as 'club-shaped'. These claviform arm spines do not align with the adjacent spines on the opposite vertical series; the alternating pattern of claviform arm spines is 2/3 for O. venosa. The claviform arm spines of O.venosa, are distinguishable to the species as they are also furcated, meaning that there are cloven projections along the tips of their enlarged arm spines.

Ophiomastix venosa generally range in various shades of yellows, grays, and browns with distinct dark and white markings along their central disk and arms. Their smooth central disk is yellow with patterned dark lines outlined in white that irregularly extend from their central radial shields. Their arms are similarly colored to their central disk with dark lines centrally ranging the length of their arms and darker yellow bands circling the dorsal plates along their arms.

File:Ophiomastix venosa (10.17159-2305-7963-2015-v11n1a3) Plate 4 (cropped).jpg

Ophiomastix venosa have a central disk lacking granules and, if present, have spinules that are widely distributed. O. venosa is the largest Ophiocomoid on the southeastern coastal African coral atoll, Aldabra, when comparing disk diameter and the ratio of arm length: disk diameter. O. venosa have been repeatedly described to have central disk diameters larger than those of their relatives. The maximum diameter of the central disk was measured at 41mm when observing individuals along the Aldabra coral atoll. O. venosa have been observed to commonly grow to reach a central disk size of over 20mm in diameter. The length of O. venosa arms are variable, but the species has a patterned arm length to disk diameter ratio of 5.5:1, respectively.

Ophiomastix venosa have dental plates that account for around 20% of their central disk's diameter length. Their oral shields, also located within their central disk, are heart-shaped, and the length of these plates are similar if not equal in width. O. venosa{{'}}s dental plate's length:breadth ratio is 2.8:1.

Ophiomastix venosa is a species of brittle star belonging to the Ophiomastix genus.{{Cite web |title=WoRMS - World Register of Marine Species - Ophiomastix venosa Peters, 1851 |url=https://www.marinespecies.org/aphia.php?p=taxdetails&id=212397 |access-date=2025-04-16 |website=www.marinespecies.org}} The Ophiomastix genus is composed of 31 species/subspecies{{Cite web |title=WoRMS - World Register of Marine Species - Ophiomastix Müller & Troschel, 1842 |url=https://www.marinespecies.org/aphia.php?p=taxdetails&id=204164 |access-date=2025-04-16 |website=www.marinespecies.org |language=en}}; O. venosa is most closely related to O. annulosa, O. koehleri, and O. asperula.{{Cite journal |last=O'Hara |first=Timothy D. |last2=Hugall |first2=Andrew F. |last3=Cisternas |first3=Paula A. |last4=Boissin |first4=Emilie |last5=Bribiesca-Contreras |first5=Guadalupe |last6=Sellanes |first6=Javier |last7=Paulay |first7=Gustav |last8=Byrne |first8=Maria |date=2019-01-01 |title=Phylogenomics, life history and morphological evolution of ophiocomid brittlestars |url=https://www.sciencedirect.com/science/article/abs/pii/S1055790318302197?casa_token=KrcUTvpMOhYAAAAA:8MEn9TbrZa47YNxSc7YiiudLcX4rIIQkb_8XOPp_xSUEjRR800QCeSf94709fdPoiUBTJpISdoU |journal=Molecular Phylogenetics and Evolution |volume=130 |pages=67–80 |doi=10.1016/j.ympev.2018.10.003 |issn=1055-7903}}

File:Indo-Pacific biogeographic region map-en.png

Ophiomastix venosa is a strictly marine species of Echinoderms. They have been commonly found in Indo-Pacific shallow, coastal waters along coral atolls and rock formations, and are believed to be limited to the intertidal and coastal zones of Indo-Pacific waters.{{Cite book |last=British Museum (Natural History) |url=https://www.biodiversitylibrary.org/page/2236748 |title=Bulletin of the British Museum (Natural History) Zoology |last2=History) |first2=British Museum (Natural |date=1979 |publisher=BM(NH) |volume=v.37 (1979-1980) |location=London}} Ophiomastix venosa have been observed in many different microhabitats ranging throughout the Indo-Pacific Oceans and Seas with various substrate and geological components.

Early observances of Ophiomastix were discovered throughout the Red Sea, within coastal waters of Zanzibar, ranging through the coastal waters along the Pacific Hawaiian Islands.{{Cite book |last=Lyman |first=Theodore |url=https://books.google.com/books?hl=en&lr=&id=S61AAQAAIAAJ&oi=fnd&pg=PA2&dq=ILLUSTRATED+CATALOG+OF+THE+MUSEUM+OF+COMPARATIVE+ZOOLOGY,+AT+HARVARD+COLLEGE.+No.+VI.+SUPPLEMENT+TO+THE+OPHIURIDA+AND+ASTROPHYTID%C3%86.+BY+THEODORE+LYMAN.&ots=8O5vUGGovR&sig=B8yiat4-Dwe0nZTeRLp0a0L0XIw |title=Ophiuridæ and Astrophytidæ |date=1865 |publisher=University Press: Welch, Bigelow, & Company |language=en}} More recent observations of O. venosa have occurred through studies located within the South China Sea.{{Cite journal |last=Lane |first=David J.W. |last2=Marsh |first2=Loisette M. |last3=VandenSpiegel |first3=David |last4=Rowe |first4=Frank W.E. |title=Echinoderm Fauna of the South China Sea: An Inventory and Analysis of Distribution Patterns |url=https://www.researchgate.net/profile/Halldis-Ringvold/post/Which_key_is_best_to_identify_sea_stars/attachment/59d64790c49f478072eaf162/AS%3A273844755992576%401442301085870/download/Lane+et+al.+2000+Asteroidea+South+China+Sea.pdf |journal=The Raffles Bulletin of Zoology |issue=8 |pages=459–493 |via=ResearchGate}} One sighting of O. venosa occurred over the course of an expedition in the Mozambique Channel; the individual was sighted within a patch of reef in the Indian Ocean (between the coast of Eastern Africa and Madagascar).{{Cite journal |last=Mulochau |first=T. |last2=Conand |first2=C. |last3=Stöhr |first3=S. |last4=Eléaume |first4=M. |last5=Chabanet |first5=P. |date=2014 |title=First inventory of the echinoderms from Juan de Nova (Iles Eparses, France) in the Mozambique Channel, South Western Indian Ocean. |url=https://www.ajol.info/index.php/wiojms/article/view/112588 |journal=Western Indian Ocean Journal of Marine Science |language=en |volume=13 |issue=1 |pages=23–30 |issn=2683-6416}} O. venosa has also been observed inhabiting coral atolls off of the southeastern coast of Africa.

Throughout the coastal waters of the Indo-Pacific, O. venosa have been observed in specialized microhabitats with various substrate forms. The species has been observed in shallow coral reef structures covering sandy gravel substrate, under rocks and boulders in shallow waters, along the intertidal zone of seaward platforms (landforms occurring on rocky shore lines due to coastal erosion{{Cite journal |last=Kennedy |first=David M. |date=2015-08-01 |title=Where is the seaward edge? A review and definition of shore platform morphology |url=https://linkinghub.elsevier.com/retrieve/pii/S0012825215000902 |journal=Earth-Science Reviews |volume=147 |pages=99–108 |doi=10.1016/j.earscirev.2015.05.007 |issn=0012-8252}}), and within seagrass beds near oceanic channels.

Ophiomastix venosa have been studied to reside in relatively limited parameters of water; the species is comparatively sensitive to the dissolved oxygen concentration, pH, salinity, and temperature parameters within their habitat when compared to other species that inhabit separate niches.{{Cite journal |last=Paujiah |first=E. |last2=Kinasih |first2=I. |last3=Hawa |first3=P. |last4=Widiana |first4=A |last5=Kurniati |first5=T. |last6=Cahyanto |first6=T. |date=April 18, 2018 |title=Distribution Of Brittle Star (Ophiuroidea) on Rancabuaya Coastal Areas, Garut, West Java |url=https://iopscience.iop.org/article/10.1088/1757-899X/434/1/012124/pdf |journal=IOP Conference Series: Materials Science and Engineering |volume=434 |issue=3 |pages=012124 |doi=10.1088/1757-899x/434/1/012124/meta |via=ResearchGate}}

The O. venosa brittle star, although observed on limited occasions, resides in many regions throughout the Indo-Pacific oceans and seas. Their habitats are distinguished by substrate characteristics and habitable water parameters, allowing the species to reside in many locations around the world with significantly similar niches.

Ophiomastix venosa have complex development cycles and perform sexual reproduction.

Ophiomastix venosa reproduce on an annual cycle, in which they spawn throughout the months of November to February,{{Cite journal |last=Delroisse |first=Jerome |last2=Fourgon |first2=Didier |last3=Eeckhaut |first3=Igor |date=October 2013 |title=Reproductive cycles and recruitment of the two co-existing tropical brittle-stars from the barrier reef of Toliara (Madagascar), Ophiocoma scolopendrina and Ophiomastix venosa. |url=https://orbi.umons.ac.be/bitstream/20.500.12907/32852/1/Delroisse_et_al_2013_CBM_ReproductiveCycles.pdf |journal=Cahiers de Biologie Marine |issue=54 |pages=721–727 |via=ResearchGate}} this duration of time is known as the austral summer. O. venosa eggs average 550 µm in diameter, which is much larger than egg sizes of other closely related Ophiomastix species. Their eggs are buoyant in the water column, which increases the success of fertilization and distribution, and are green with a smooth envelope.

The larva O. venosa are vitellaria, meaning that their larvae are free-swimming within the water column and non-feeding.

Ophiomastix venosa undergo metamorphosis throughout their larval, juvenile, and adult developmental stages.{{Cite journal |last=FOURGON |first=DIDIER |last2=EECKHAUT |first2=IGOR |last3=VAÏTILINGON |first3=DEVARAJEN |last4=JANGOUX |first4=MICHEL |date=2005-01-01 |title=Lecithotrophic development and metamorphosis in the Indo-West Pacific brittle star Ophiomastix venosa (Echinodermata: Ophiuroidea) |url=https://www.tandfonline.com/doi/abs/10.1080/07924259.2005.9652156 |journal=Invertebrate Reproduction & Development |volume=47 |issue=3 |pages=155–165 |doi=10.1080/07924259.2005.9652156 |issn=0792-4259 |via=Taylor & Francis Online}} The gastrula of O. venosa, which is a stage in embryonic development, morphs into an early larvae with uniformly distributed cilia, which then further develops into other larval and juvenile forms. O. venosa develop into lecithotrophic larvae, meaning that their larval form develops from the yolk provided by the mother, rather than their larval forms feeding on resources acquired from their surrounding environment. Lecithotrophic larvae, since dependent on their mother's yolk for nutrition,{{Citation |last=Calado |first=Ricardo |title=Chapter One - Trophic Ecology of Benthic Marine Invertebrates with Bi-Phasic Life Cycles: What Are We Still Missing? |date=2015-01-01 |work=Advances in Marine Biology |volume=71 |pages=1–70 |editor-last=Curry |editor-first=Barbara E. |url=https://linkinghub.elsevier.com/retrieve/pii/S0065288115000061 |access-date=2025-04-17 |publisher=Academic Press |doi=10.1016/bs.amb.2015.07.001 |last2=Leal |first2=Miguel Costa}} are limited as to how far they can disperse as larvae and often settle to the benthos quickly to metamorpihize into symbiotic or free-living juveniles; O. venosa{{'}}s egg buoyancy allows for greater dispersal to counter the limited dispersal ability of their lecithotrophic larvae.

Ophiomastix venosa exhibit symbiotic relationships in juvenile developmental stages.

The development period from larvae to new recruits, or juveniles with a central disk diameter of 4mm, is around 3–4 months long. Brittle star species are commonly observed living in close connections with other species.{{Cite journal |last=Byrne |first=Maria |last2=Cisternas |first2=Paula |last3=O'Hara |first3=Tim |date=2008 |title=Brooding of pelagic-type larvae in Ophiopeza spinosa: reproduction and development in a tropical ophiodermatid brittlestar |url=https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1744-7410.2007.00110.x?casa_token=i2GmT0jfLWgAAAAA%3ARSRF8zCx7KEADAzgX7oRyQzTp678YcEmmnJdvkixTMmZYeCyPxGp6lyVJf2_n_ZjY9e11lWgEFPb9yUt& |journal=Invertebrate Biology |language=en |volume=127 |issue=1 |pages=98–107 |doi=10.1111/j.1744-7410.2007.00110.x |issn=1744-7410}} Juvenile O. venosa have been observed to 'hitchhike' on the disks of another species of brittle star that inhabit similar geographical locations, Ophiocoma scolopendrina, through development.{{Cite journal |last=Fourgon |first=Didier |last2=Jangoux |first2=Michel |last3=Eeckhaut |first3=Igor |date=2007 |title=Biology of a “babysitting” symbiosis in brittle stars: analysis of the interactions between Ophiomastix venosa and Ophiocoma scolopendrina |url=https://onlinelibrary.wiley.com/doi/full/10.1111/j.1744-7410.2007.00108.x?casa_token=52KRqxh9CP8AAAAA%3AtegaB5m-FDpo12FWWYoccV-Kt6birOUnf6pS4yIpdkQTcnHkDHTqVLq70SfaAaFyzHXqLo0u_J5lVEfV |journal=Invertebrate Biology |language=en |volume=126 |issue=4 |pages=385–395 |doi=10.1111/j.1744-7410.2007.00108.x |issn=1744-7410}} This is described as 'babysitting' symbiosis. Juvenile O. venosa feed on the excess neuston that their host, O. scolopendrina, does not ingest. This symbiotic relationship between O. venosa and their 'babysitting' companion allows for more successful development of juveniles into adulthood. O. venosa juveniles participating in a symbiotic relationship with O. scolopendrina are able to specifically recognize their symbiotic babysitter. O. venosa juveniles depart from their symbiotic host and migrate into their personal microhabitat when their central disk reaches a diameter of 6mm. When the symbiotic juveniles depart from their symbiotic host, their feeding habits alter and they begin to feed on algae into adulthood.

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Category:Ophiocomidae

Category:Animals described in 1851

Category:Taxa named by Wilhelm Peters