שיחה:ארסן-ים פרחוני
הוספת נושאתרגום משפטים[עריכת קוד מקור]
בעלי הידע באנגלית, בעלי הידע בבעלי חיים ובעלי הידע בתרגום איך לתרגם את המשפטים האלו: Flower urchins feed on algae, bryozoans, and organic detritus.[26][29]
Predators Flower urchins have few predators.[17] They are known to be toxic to fish. One of the few organisms capable of consuming flower urchins with no apparent adverse effects is the predatory corallimorph Paracorynactis hoplites. However it is unknown if flower urchins are among its natural prey.[30]
Associated species
The zebra crab, Zebrida adamsii, is a parasite of flower urchins The commensal alpheid shrimp Athanas areteformis, can sometimes be found living among the spines of flower urchins (as well as burrowing urchins and collector urchins).[31] The intestines of flower urchins can also serve as habitats for the commensal flatworm Syndesmis longicanalis.[32]
Flower urchins are also common hosts of the zebra crab, Zebrida adamsii. These tiny crabs are obligate symbionts of sea urchins. They cling to the spines on the outer surface of the sea urchin test using their highly specialized walking legs. Because their ability to walk on substrates like sand is impaired, zebra crabs spend their entire benthic life stage attached to sea urchins, switching between hosts only during the mating season. Usually only one zebra crab is attached to an individual sea urchin outside of the mating season, but larger sea urchins can be hosts to two (very rarely more). The area of the test they inhabit is characteristically smooth; completely devoid of spines, pedicellariae, tube feet, and even epidermis. It is unknown if they physically destroy and/or consume these appendages or if they use other stimuli to induce the host sea urchins to autotomize. Although previously considered harmless commensals, authors have since reclassified them as parasites. In addition to the visible external damage, a 1974 study also observed abnormal behavior and coloration among infected sea urchins. They also appear to be immune to the flower urchin's venom.[10][33][34]
Reproduction Flower urchins are dioecious (having separate male and female individuals), but it is almost impossible to determine the sex of an individual by external characteristics alone. A possible method is by examining the external characteristics of the genital pores (gonopores). In males, they are generally short, cone-shaped, and extrude above the body surface; while in females they are usually sunken. However this is not reliable, as 15% of the cases can exhibit the opposite characteristics. All other external features, like shape and size of the tests or color of the spines are indistinguishable between the two sexes.[35] Flower urchins have a chromosome number of 2n = 42.[36]
Relatively little is known of the spawning behavior of flower urchins. Like other sea urchins, fertilization happens externally. Males and females release free-swimming gametes (eggs and sperm) directly into the water currents in mass spawning events.[37] In Okinawa, Japan, a 1994 study identified the spawning season of flower urchins as occurring in winter, at the same time as the closely related and sympatric Toxopneustes elegans. It also recorded possible natural hybrids resulting from instances where the eggs of Toxopneustes pileolus are fertilized by the sperm of Toxopneustes elegans.[38]
In Taiwan, a 2010 study observed flower urchins spawning in May on the years 2007 and 2009. They occurred on highly similar conditions: in the afternoon low tide of the spring tide immediately after a new moon. During the event, spawning individuals discard the debris that usually cover their bodies before releasing their gametes into the water.[37] Another study published in 2013 did not find any obvious correlation between lunar and tidal cycles to the mass spawning behavior of the flower urchin populations in southern Taiwan. It did note that the spawning patterns appeared to be non-random, with higher spawning rates on daytime on certain dates. However, the study was conducted within a span of only five months (from April to August 2010).[39]
"Covering" behavior
Flower urchin off the coast of Réunion exhibiting "covering" behavior Flower urchins are among the numerous species of sea urchins known as "collector urchins", so named because they frequently cover the upper surfaces of their bodies with debris from their surroundings. This behavior is usually referred to as "covering" or "heaping".[28][33][40] Flower urchins are usually found almost completely covered in objects like dead coral fragments, shells, seaweed, and rocks.[17][41] These are held fast to their bodies using their tube feet and pedicellariae.[37]
The function of this behavior is not well understood. Some authors believe that the debris serve as ballast, preventing them from being swept away by wave surges when feeding;[37][42] while others believe that they may function as some sort of defense against predation.[33] A 2007 study has hypothesized that the behavior may serve as protection from UV radiation during daytime.[43 יהודה אמיר - שיחה 16:36, 20 באפריל 2022 (IDT)