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Colochirus quadrangularis
(Troschel, 1846)
Quadrangular Sea Cucumber
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Ebony Sharples 2019
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Summary | |
Colochirus quadrangularis commonly known as the quadrangular or thorny sea cucumber is a species of sea cucumber belonging to the family Cucumariidae and was first described by Troschel in 1846 (WoRMS, 2019). This moderately sized sea cucumber is distinguished by its thorny appearance and three rows of bright red tubed feet (O’Loughlin, Harding & Paulay, 2016). The specimen described in this profile was collected from the intertidal rocky shore at Shorncliffe in Queensland. This widespread species is commonly located in shallow waters across the Indo-Pacific region (O’Loughlin et al., 2016). This species, like many sea cucumbers exhibits interesting morphological, physiological and behaviour traits, from their unique regeneration properties to their ability to “breathe” via the anus.
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| Figure 1 |
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Physical Description | |
C.quadrangularis has a leathery body that varies in colour from grey to pink to reddish brown or orange (Cranitch, Wright, Davie & Cowell, 2011). This species is moderate in size ranging from 10-30cm in length and displays a broad anterior end (Cranitch et al., 2011). As suggested in the common name the body of the quadrangular sea cucumber comprises of four longitudinal ridges, resulting in a square cross section and flat ventral surface (Woo et al., 2014). Protruding along these ridges on the dorsal surface are irregular, soft, thorn-like projections called papillae (Woo et al., 2014).
Although not as distinct as other echinoderms C.quadrangularis exhibits pentaradial symmetry along with pronounced features of bilateral symmetry (Smirnov, 2014). The ventral surface has three distinct rows of red tube feet (podia) separated by interambulacra area, tapering at the posterior end (Woo et al., 2014). The anterior end comprises of a mouth that is comparable to the oral pole of other echinoderms. The mouth is surrounded by a ring of ten dendritic feeding tentacles that can be extended and retracted when feeding (Woo et al., 2014). The colour of these feeding tentacles varies from yellow, white or red among different specimens. When retracted the tentacles are enclosed by five blunt valves (James, 1984). The posterior end contains the anus which is surrounded by five tooth-like projections, this end corresponds to the aboral pole of other echinoderms (James, 1984).
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Ecology |
Habitat | |
The specimens examined for the profile were collected at low tide from the intertidal rocky shore at Shorncliffe, Queensland. One specimen was attached to a rocky substrate out of the water, while the other was fully submerged at the bottom of a rock pool. Individuals also populate seagrass beds in which they use their tube feet to firmly attach to the seagrass or other hard projections such as tube worm cases. Previous observations reveal C. quadrangularis are highly abundant in areas that exhibit the seagrass species Enhalus acoroides (Woo et al., 2014). This species has also been observed in deeper waters up to 115 m when discovered in dredged and trawled samples (Marsh & Morrison, 2004). While in captivity it was observed that the specimens preferred to attach themselves to hard surfaces such as the glass on the side of the tank, rubble or aeration pipes and rarely resided in the sand at the bottom of the tank.
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Predators | |
Sea cucumbers are predated on by a number of predatory species including seastars, crustaceans and fish (Francour, 1997). With majority of the literature considering seastars as the main predator (e.g., Mauzey et al., 1968; Bingham & Braithwaite 1986). This is due to the seastars ability to consume large quantities of sea cucumbers made possible by their sensitive detection system and digestive physiology (Francour, 1997).
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Life History and Behaviour |
Reproduction & Development | |
Species with the class Holothuroidea have separate sexes (gonochoric) and unlike other echinoderms they possess only one gonad (Brusca, Moore & Shuster, 2016). Spawning occurs externally as males release a constant stream of sperm out of the anterior end, shortly after females will spawn releasing pale yellow eggs in quick, powerful bursts (Kumara, Jayanatha, Pushpakumara, Bandara & Dissanayake, 2013). Following external fertilisation, the embryo undergoes early stages of embryonic development including cleavage, blastulation and gastrulation (Kumara et al., 2013). Embryos then undergo three distinct phases of larval development:
- Auricularia larvae: This is the feeding stage in which transparent larvae use ciliated bands to swim around the pelagic zone feeding on microalgae (Kumara et al., 2013)
Many species within the order Dendrochirotida are capable of asexual reproduction via transverse fission in the form of constriction, twisting or stretching (Dolmatov, 2014). Only one study has investigated asexual reproduction in C. quadrangularis. The results of this study revealed that the animal constricted however the body wall was not torn and no organs were thrown out hence fission was not evident (Dolmatov, 2014).
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Feeding | |
C. quadrangularis are suspension feeders that use a sequence of coordinated movements to capture and feed on particles suspended in the water, such as of phytoplankton and organic detritus (Brusca et al., 2016). When feeding the ten-mucus covered buccal tentacles are extended into the water, trapping suspended materials (Brusca et al., 2016). One at a time the tentacle bearing food is slowly retracted into the mouth where food particles are scraped of and ingested. The tentacle is then outstretched as another particle filled tentacle is presented to the mouth (Sun, Hamel, & Mercier, 2018).
It was observed that feeding specimens would located themselves just below the surface of the water. This is consistent with studies that suggest water motion influences the distribution of suspension feeding sea cucumbers (Sun, Hamel, & Mercier, 2018). Exposure to high water flow increases the amount of water passed over the feeding tentacles, hence increases the quantity of suspended material that can be trapped in the tentacles (Toonen, 2003).
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Timelapse showing coordinated movements of C. quadrangularis suspension feeding.
Video by Ebony Sharples. |
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Defence Mechanisms | |
In response to predation sea cucumbers have developed several anti-predatory mechanisms (Francour, 1997) a number of which were displayed in the collected specimens. The specimen exhibited tough, leathery skin which allows for increased protection. Body swelling was observed when collecting the specimen from the field. This occurs when sea cucumbers consume large amounts of sea water causing them to increase in size when they are threatened or in unsuitable conditions. The increased size allows for easy transportation by water currents (Toonen, 2003).
In contrast sea cucumbers can shrink their body to the minimum size possible (Toonen, 2003). This was evident when the specimens were disturbed throughout examination, they would protect their tentacles by retracting them and stiffen their body. Sea cucumbers also possess superior regenerative capabilities (Dolmatov, 2014) which was evident in the specimens’ ability to regenerate its tube feet.
While not directly observed in the specimens, some holothurians have the ability to anally project and then regenerate their entrails by contracting muscles. This process is known as evisceration and is thought to be a defence mechanism (Brusca et al., 2016). In addition, some species can release internally produced toxic substances called holothurian into the water to debilitate or kill predators (Bourjon & Vasquez, 2016). Understanding of these mechanisms in C. quadrangularis are currently lacking, future research into these areas may provide interesting insights.
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| Figure 8 |
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Anatomy and Physiology |
Body Wall | |
The body wall comprises of an epidermis and a dermis composed of connective tissue, enclosing widely isolated, calcareous, skeletal elements known as ossicles. Ossicles are built from porous, spongelike stereom and provide rigidity and protection (Brusca et al., 2016).
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| Figure 9 |
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Digestive System | |
A ring of calcareous plates surrounds the pharynx, which is located behind the mouth. This forms the attachment point for muscles that allow the feeding tentacles to retract while also supporting the foregut and the ring canal. The pharynx connects to the elongated intestine and stomach (Brusca et al, 2016). The long, coiled intestine consists of three portions, a descending, an ascending and finally a descending loop that connects to an expanded rectum that leads to the anus (Brusca et al., 2016).
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| Figure 10 |
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Nervous System | |
The decentralised nervous system comprises of a circumoral nerve ring surrounding the oral cavity that sends nerves to the tentacles and pharynx. From this ring five radial nerves extended down parallel to the body along each ambulacrum (Brusca et al., 2016).
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Respiratory System | |
C. quadrangularis extracts oxygen from the water via a respiratory tree. This organ lies alongside the intestine in the body cavity branching from the cloaca just inside the anus. The sea cucumber draws oxygenated water into the anus by expanding the cloaca, this is known as “anal breathing”. Circular muscles (sphincters) close the cloaca forcing the water into the respiratory trees. Gas exchange occurs across a thin membrane into the fluid of the main body cavity (Purcell, Samyn & Conand, 2012).
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C. quadrangularis drawing in oxygenated water through its anus by using sphincters close to the cloaca this action forces water into the respiratory tree.
Video by Ebony Sharples. |
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Circulatory System | |
Internal transport in C. quadrangularis is achieved through a combination of the water vascular system, the haemal system and perivisceral coeloms (Brusca et al., 2016).
The hydraulic pressure provided by the water vascular is what facilitates locomotion and feeding in C. quadrangularis. The stone canal located beneath the pharynx gives rise to an internal madreportie. This pore takes up celomic fluid from inside the body and transports it to the ring canal that house polian vesicles. The water pressure in the polian vesicles hydraulically control the oral tentacles, when the polian vesicles contract water is forced into the tentacle resulting in extension. The ring canal outspreads into longitudinal canals that run posteriorly down the ambulacra grooves, giving rise to rows of ampulla. The hydraulic pressure of the individual ampulla coupled with the muscle action control the external tube feet. Increased pressure along with forces the sucker on the bottom of the tube feet adhere to the substrate (Brusca et al., 2016).
The haemal system is well developed and comprises of elaborate haemal vessels. The haemal vessels are associated with the digestive tract and form a complex meshwork with the respiratory tree. The haemal system can include a multitude of “hearts” or circulatory pumps (Brusca et al., 2016).
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The water vascular system in C. quadrangularis uses hydraulic pressure to control movement of the tube feet and extension of the feeding tentacles.
Video by Ebony Sharples.
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Biogeographic Distribution | |
C. quadrangularis is widely distributed throughout the Indo-Pacific region and can be found in Australia, East Africa, Madagascar, Malaysia, Singapore, Sri Lanka and many other locales (Kumara et al., 2013; O’Loughlin et al., 2016; Woo, 2014).
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Evolution and Systematics | |
Holothuroidea is one of the six extant classes within the strictly marine phylum Echinodermata. This class comprises of approximately 1,700 extant species that can be separated into five orders (Brusca et al, 2016). The earliest undisputed fossil recorded can be traced back to the Silurian period, roughly 425 million years ago (Arndt et al 1996). Prior to technological advancement the evolutionary relationships of holothuroid linages were poorly comprehended. It is hypothesised that holothuroids arose by paedomorphic reduction from extinct, burrowing echinoderms that resemble spineless sea urchins known as ophiocystioids (Brusca et al., 2016).
Continued diversification occurred throughout the Palaeozoic Era with ancestors diverging. It wasn’t until the early Mesozoic Era, 200 million years ago that majority of the orders including Aspidochirotida, Molpadiida, Dendrochirotida and Dactylochirotida began to diverge (Kerr, 2000). C. quadrangularis belongs to the order Dendrochirotida, the defining characteristics of this order include highly branched tentacles, a muscle for retracting them, a body wall imbedded with small ossicles, the presence of a respiratory tree and tube feet (Brusca et al., 2016). Studies of DNA sequencing is mostly consistent with morphological data. However, discrepancy exists with the family level branching of dendrochirotes (Kerr, 2000).
C. quadrangularis is placed within the family Cucumariidae which contains 96 genera (WoRMS,2019). This family is classified by the presence of ten dendritic tentacles often with two being smaller than the others, leathery skin, ossicles, calcareous ring lacking segmentation (O’Loughlin, Mackenzie, Paulay & VandenSpiegel, 2014). C. quadrangularis is within the genus Colochirus which comprises of 37 direct children (WoRMS, 2019).
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Conservation and Threats | |
Although not as popular as other sea cucumber species C. quadrangularis are harvested for live aquarium trade. Like other marine creatures harvested from the wild majority die before reaching retailers or soon after they are sold due to lack of professional care (Toral-Granda, Lovatelli & Vasconcellos, 2003).
On the IUCN Red List of Threatened Species the current conservation status of this species is not known. However, it would be advisable to monitor populations given the potential for this species to be overexploited like many others within the class Holothuroidea.
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References | |
Bingham, B. L., & Braithwaite, L. F. (1986). Defense adaptations of the dendrochirote holothurian Psolus chitonoides Clark. Journal of Experimental Marine Biology and Ecology, 98, 311-322.
Brusca, R. C, Moore, W., & Shuster, S. M., (2016). Inverterbrates. Sunderland, Massachusetts: Sinauer Associates Inc Publishers.
Cranitch, G., Wright, J., Davie, P., & Cowell, B. (2011). Wild Guide to Moreton Bay and Adjacent Coasts. Queensland: Queensland Museum.
Dolmatov, I. Y. (2014). Asexual reproduction in holothurians. The Scientific World Journal, doi:10.1155/2014/527234
Francour, P. (1997). Predation on holothurians: a literature review. Invertebrate Biology, 116, 52-60.
James, D. B. (1984). Studies on Indian echinoderms - 15. On Psolus mannarens1s sp. Nov. and other Dendrochirotids from the Indian Seas. Journal of the Marine Biological Association of India, 26, 109-122.
Kerr, A. (2000). Evolution and systematics of Holothuroidea (Echinodermata). Thesis, Yale University.
Kumara, A., Jayanatha, J. S., Pushpakumara, J., Bandara, W., & Dissanayake, D. C. T. (2013). Artificial breeding and larval rearing of three tropical sea cucumber species – Holothuria scabra, Pseudocolochirus violaceus and Colochirus quadrangularis – in Sri Lanka P.A.D. SPC Beche-de-Mer Inf. Bull. 33, 30–37.
Marsh, L.M., & Morrison, S.M. (2004). Echinoderms of the Dampier Archipelago, Western Australia. Records of the Western Australian Museum, 6, 293-342.
Mauzey, K. P., Birkeland ,C., & Dayton, P. K. (1968). Feeding behavior of asteroids and escape responses of their prey in the Puget Sound region. Ecology, 49, 603-619.
O’Loughlin, P. M., Harding, C., & Paulay, G. (2016). The sea cucumbers of Camden Sound in northwest Australia, including four new species (Echinodermata: Holothuroidea). Memoirs of Museum Victoria, 75, 7–52.
O’Loughlin, P. M., Mackenzie, M., Paulay, G., & VandenSpiegel, D. (2014). Four new species and a new genus of Antarctic sea cucumbers with taxonomic reviews of Cladodactyla, Pseudocnus, Paracucumidae and Parathyonidium (Echinodermata: Holothuroidea: Dendrochirotida). Memoirs of Museum Victoria, 72, 31–61.
Purcell, S.W., Samyn, Y., & Conand, C. (2012), Commercially important sea cucumbers of the world, FAO Species Catalogue for Fishery Purposes, 6, 1-127.
Smirnov, A. V. (2014). Sea Cucumbers Symmetry (Echinodermata: Holothuroidea). Paleontological Journal, 48, 1215–1236.
Sun, J., Hamel, J., & Mercier, A. (2018). Influence of flow on locomotion, feeding behaviour and spatial distribution of a suspension-feeding sea cucumber. Journal of Experimental Biology, 221, jeb189597.
Toonen, R. J. (2003). Invertebrate Non-Column: Sea cucumbers - Part II. in Advanced Aquarists Online Magazine.
Toral-Granda, V., Lovatelli, A., Vasconcellos, M. (2008). Sea cucumbers. A global review of fisheries and trade. FAO Fisheries and Aquaculture Technical Paper, 516.
Woo, S. P., Teh, C. P., Norhanis, M. R., Nithiyaa, N., Amelia-Ng, P. F., Zulfigar, Y., & Tan, S. H. (2014). Sea cucumber species of the Merambong Shoal with notes on the distribution and habitat of the dominant species. Malayan Nature Journal, 66, 159-167.
WoRMS. (2019). Cucumariidae Ludwig, 1894. Retrieved from: http://www.marinespecies.org/aphia.php?p=taxdetails&id=123187 on 2019-05-29
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