Overview

Brief Summary

Taxonomy

Morphology
Neocrinus decorus, like most echinoderms, is composed of numerous calcite plates which are arranged into different organs.N. decorus is divided into 3 sections:
  1. The stem:
    • raises the calyx and arms above the sediment and is composed of a stack of numerous 5-sided star-shaped plates.
    • bears flexible, finger-like appendages called cirri that are used to reattach itself to the substrate after moving.
  2. The calyx (body or theca):
    • is formed of 2 bands of 5 plates that form a cup-shaped body, from which the bases of the arms arise.
    • is covered on top by numerous small polygonal plates. The mouth and anus are found on this surface.
  3. Arms:
    • 5 originate in the calyx but these frequently divide, similar to tree branches, so that there may be up to 40 arms in total.
    • are formed of stacks of U-shaped calcite plates
    • bear numerous projections called pinnae (like those of a fern frond). It is on these pinnae that tube feet, covered in mucus, extend into the water and catch plankton.
    • are moveable
    • are usually arranged in a parabolic fan to collect food
    • can be used for crawling (dragging the stem behind it).
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Introduction

Neocrinus decorus is a stalked crinoid, or sea lily, a type of echinoderm. Although it is flower-like in appearance, it is actually an animal. It lives on the sea floor in tropical Atlantic Ocean waters at depths down to 1200m.Stalked crinoids were first described from fossils and were thought to be long extinct until they were discovered living in the Caribbean in the early 19th century. This surprising find caused quite a stir and they are still often known as living fossils.
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Comprehensive Description

Reproduction lifecycle

Reproduction
Sexes are differentiated for Neocrinus decorus, meaning there are male and female individuals. Eggs are produced in large numbers and are held on the pinnules of female individuals. Sperm released into the water stimulates release of the eggs and they are fertilised immediately after. Therefore, Neocrinus produces many young over a week or so, which are released to fend for themselves.

Lifecycle
Once the eggs are released from the parent and fertilised, the resultant embryo attaches to a solid substrate. This may be the arms of the parent crinoid or another surface.The embryo then develops over several days into a free-swimming, planktonic larva called a doliolaria. After several days these larvae again become fixed and develop a stem, mouth and 5 podia (arm-like structures). This stage is called the cystidean stage.After several weeks the crinoid reaches the pentacrinoid stage where it forms true arms, pinnules, a complete theca and stem. Finally, the crinoid breaks free from the attachment disc and becomes a stalked, free-living adult enabling the animal to move about and seek out the best feeding areas. The animal continues to grow by adding new plates to the stem and arms so that they can reach further into the water column. After a year the animal is fertile and produces either sperm or eggs.

Cyclicity
Most crinoids breed once per year during the spring when both eggs and sperm are released into the water column.
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Biology

Size
Neocrinus decorus has a stem that is more slender than other crinoids, however it grows 3 or 4 times as fast as other species.Adults are approximately 70cm high.

Growth
N. decorus grows:
  • continuously throughout its lifetime
  • 10-17cm per year
Like other echinoderms, Neocrinus has amazing powers of regeneration. Individuals are able to lose about two thirds of the calyx and arms and still be capable of regenerating the missing parts.The crinoid can also shed parts of its stem if attacked by predatory sea urchins and it has been shown that in individuals where the calyx and arms have been detached from the stem, the calyx is able to completely regenerate a stem.

Life Expectancy
The average lifespan of Neocrinus sea lilies is unknown but they probably live for several years. Some crinoids are thought to live for over 10 years.Individual stem elements that have been shed by the parent crinoid are able to survive, presumably without feeding, for over 13 months.

Dispersal
Dispersal is primarily via a planktonic larval stage although adults are also capable of limited mobility, assisting in species dispersal.
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Distribution

Distribution
Neocrinus decorus is found in the tropical waters of the western Atlantic Ocean, particularly around the Caribbean. View a map of Neocrinus decorus distribution on the Oceana websiteAs it is known from Miocene sediments of Barbados and Jamaica, the species spans at least 23 million years (Donovan and Veltkamp, 2001).

Habitat
This deep sea species lives on the sea floor at depths of 150m to 1200m.

Population biology
The species may appear in:
  • large numbers (crinoid meadows) on the sea floor
  • groups on rocky protuberances


Threats and conservation status
These creatures are are vulnerable to:
  • ocean acidification
  • drag net fishing
However, they are unlikely to become threatened or extinct in the near future.

Risk statement
N. decorus is non-invasive, with little impact on the environment.
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Physical Description

Morphology

Diagnostic description

  • Basals variable from small and separated to rather large, forming contiguous basals circlet, commonly with median prolongation of lower edge covering interradial edge of uppermost columnals.
  • Arms divided at primibrachs 2 and further divided with variable intervals.
  • Articulartion at primibrachs 1-2 and secundibrachs 1-2 more or less embauyed synarthrial.
  • Cryptosyzygial or synostosial articulations generally at secundibrachs 3-4 and more distal.
  • No symmorphy.
  • Column heteromorphic, xenomorphic, with short proxistele of low pentastellate (most proximally) to rounded pentagonal columnals, and a longer mesistele/dististele of low to moderately high, rounded pentagonal columnals with planar latera.
  • Nodal/infranodal articulations cryptosymplectial, all other articulations symplectial.
  • Areola petals pear-shaped, surrounded by adradial and (commonly) marginal crenulae, separated by adradial grooves.
  • Nodals with 5 cirri directed outwardly and posteriorly.
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Ecology

Habitat

Depth range based on 63 specimens in 1 taxon.
Water temperature and chemistry ranges based on 41 samples.

Environmental ranges
  Depth range (m): 143 - 565
  Temperature range (°C): 11.557 - 20.533
  Nitrate (umol/L): 2.133 - 16.134
  Salinity (PPS): 35.544 - 36.809
  Oxygen (ml/l): 3.261 - 4.438
  Phosphate (umol/l): 0.150 - 1.281
  Silicate (umol/l): 1.119 - 10.004

Graphical representation

Depth range (m): 143 - 565

Temperature range (°C): 11.557 - 20.533

Nitrate (umol/L): 2.133 - 16.134

Salinity (PPS): 35.544 - 36.809

Oxygen (ml/l): 3.261 - 4.438

Phosphate (umol/l): 0.150 - 1.281

Silicate (umol/l): 1.119 - 10.004
 
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Associations

Predators
Cidaroid echinoids (sea urchins) are known to feed on Neocrinus decorus (Baumiller et al., 2008). To escape predation the crinoids break off a section of stem and then use their arms to crawl away quickly from the slow-moving cidaroids.Blue-headed wrasse (Thalassoma bifasciatum) and dusky damselfish (Stegastes fuscus) have also been shown to predate N. decours in experiments (McClintock et al., 1999). This has been suggested as the reason why stalked crinoids are no longer found on reefs as they have no defence against these predators.

Diseases
Neocrinus sea lilies are vulnerable to parasites and/or diseases which affect the calcite plates. Infections cause calcite overgrowths of the plates, producing shapes and malformations similar to plant galls.
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Life History and Behavior

Behavior

Behaviour

Trophic strategy
Neocrinus decorus:
  • is a bottom-dwelling (epibenthic) filter feeder
  • feeds mainly on plankton
  • avoids coprophagae (eating its own faeces)


Behaviour
Neocrinus decorus is semi-sessile. It lives on the sea floor, mainly on hard substrates such as rocky outcrops, but doesn’t attach itself.Like other crinoids, Neocrinus catches plankton by arranging its crown of arms into a parabolic fan and positioning this within a current. To process plankton more effectively, it faces the fan into the current. The arms bear numerous rows of pinnules from which mucus covered tube feet extend and catch plankton. Food particles are passed down the arms and into the mouth.The animal’s stem holds the arms off the sea floor, helping to position them where the currents are usually strongest. The stem also enables Neocrinus to reach plankton its rivals cannot.

Migration
This crinoid is not known to migrate however individuals are capable of crawling to better feeding areas by using their arms for 'rapid' movement or cirri for slow movement.Watch a YouTube video of Neocrinus decorus using its arms to move along the sea floor
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Evolution and Systematics

Evolution

Living fossils and the Permo-Triassic extinction
Stalked crinoids were first described as fossils and were thought to be long extinct until they were dredged from the Caribbean in the early 19th century. This caused something of a stir and they are still commonly known as living fossils.Crinoids were at their most abundant during the Carboniferous but were severely reduced at the Permo-Triassic extinction event with only 1 linage surviving. All modern crinoids radiated from this single lineage.

Neocrinus and its relatives
Neocrinus:
  • is closely related to other stalked crinoids such as Metacrinus, although its divergence from the other stalked crinoids is unknown.
  • belongs to the family Isocrinidae which has a long fossil history stretching back to the Triassic when it appeared after the mass extinction at the end of the Permian.
Fossil remains of Neocrinus suggest it has been present in the Caribbean since the Miocene and has therefore undergone very little change for the past 20 million years or so (Donovan and Veltkamp, 2001).
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