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Reproduction

Egg Care in Triggerfish

Maternal care of offspring is rare among coral reef fishes with external fertilization but is known in several species of haremic triggerfish (Thresher 1984). Both male and female triggerfish establish territories where several females belong to each male's territory. It is proposed that the evolution of maternal care in triggerfish resulted since female territories in a harem do not overlap and females only spawn within their territories so a males reproductive fitness would be less by guarding eggs as females in their harem would reproduce with other males (Kuwamura 1997). Kawase (2003) reported biparental care in a species of triggerfish (Xanthichthys mento), but with males having minimum involvement in guarding the eggs. Females care for the demersal eggs until hatching by blowing water and guarding them from intruders, which commonly occurs the first night after being laid in the early morning. Parental care is necessary for eggs to survive and hatch (Kuwamura 1997). The following footage shows a female triggerfish guarding her nest from intruders attempting to prey on her eggs.

Credits
Cinematography: Dr. Stuart Sandin
Edited by: Neilan Kuntz
Written by: Neilan Kuntz
Location: Palmyra Island, Line Islands, Central Pacific (2004)

Kawase, H. (2003). Spawning behavior and biprental egg care of the crosshatch triggerfish, Xanthichythys mento (Balistidae) Envronmental Biology of Fishes 66: 211-219.

Kuwamura, T. (1997). Evolution of Female Care in Haremic Triggerfish, Rhinecanthus aculeatus. Ethology 103:1015-1023.

Thresher, R.E. (1984). Reproduction in Reef Fishes. T. F. H. Publ., Neptune.



 Sponge Spawning

Both brooding and broadcasting reproductive strategies are found in sponges (Porifera). Synchronicity in timing release of gametes has been shown in several Caribbean sponges (Hoppe, 1988). However, regulatory aspects of reproduction in sponges are poorly known (Bergquist 1978). The following footage shows a broadcasting spawning event of the sponge genus, Xestospongia spp. Lunar phase and warmer water temperatures are correlated with the spawning event of these species (Fremont et al. 1994).









Credits
Cinematography: Dr. Forest Rohwer
Edited by: Neilan Kuntz
Written by: Neilan Kuntz
Location: Borneo, Malaysia (Sipadan) (2003)

Berquist, P.R. (1978) Sponges. Hutchinson, London
Fremont, J., P.R. Bergquist (1994). Reproductive biology of three sponge species of the genus Xestospongia (Porifera: Demospongiae: Petrosida) from the Great Barrier Reef. Coral Reefs 13:119-126.

Hoppe, W.F. (1988). Reproductive patterns in three species of large coral reef sponges. Coral Reefs 7:45-50.



Sexual Dimorphism and Dichromatism

Sexual dimorphism: different sizes between sexes of the same species and sexual dichromatism: different coloration between sexes of the same species; is seen in the sling-jaw wrasse, Epibulus insidiator (Family Labridae). The sling-jaw wrasse is a protogynous hermaphrodite: changing from female to male during their life cycle. The females are either dark brown, black or yellow and the posterior part of the much larger terminal phase male is dark brown with a light grey head. Mating behavior of this species follows a lek-like system where females choose haremic males (Colin and Bell 1991). It is believed that sexual dichromatism in labroid fishes has developed as a result of male competition for females during reproduction: a more conspicuous color pattern would enhance the ability of a male to attract a mate (Robertson & Hoffman 1977). Patrolling of territories by males has been observed for fish belonging to the family Labridae (Thresher 1979). Patrolling activity involves passing close to and often interacting with each female while navigating through his entire territory. Prior to spawning the male swims above the female, circling and weaving in synchrony with her before releasing his sperm into the water column.

Credits
Cinematography: Dr. Forest Rohwer
Edited by: Neilan Kuntz
Written by: Neilan Kuntz
Location: Christmas Island, Republic of Kiribati, Central Pacific (2005)

Colin PR, LJ Bell (1991) Aspects of the spawning of labrid and scarid fishes (Pisces:Labroidei) at Enewetak Atoll, Marshall Islands with notes on other families. Enviromental Biology of Fishes 31:229-260.


Robertson DR, SG Hoffman (1977) The roles of female mate choice and predation in the mating systems of some tropical labroid fishes. Z. Tierpsychol 45:298-320


Thresher RE (1979) Social behavior and ecology of two sympatric wrasses (Labridae: Halichoeres spp.) off the coast of Florida. Marine Biology 53:161-172.




Flounder Copulation 

Social organization in flounders (Bothidae) is haremic, with males defending a territory containing a small subunit of females (Konstantinou 1995). Agonistic behavior commonly occurs between resident males and intruding satellite males. In this sexually dimorphic species, males have increased body length, larger left pectoral fin and greater interorbital distance (Kobelowsky 2004). Courtship behaviors vary between species and include: a series of slow rises up to 1 m off the substrate, circling the female by the male, raising of the male pectoral fin. Copulation occurs with both male and female rising from the substrate towards the surface. Of the Caribbean species (Bothus spp.), the male position themselves underneath the female during the ascent (Konstantinou 1995). The male releases a cloud of sperm at the apex and descends while the female hangs and releases her eggs into the sperm cloud. The following footage shows the copulation in the Caribbean species, Bothus lunatus.

Credits
 
Cinematography: Dr. Stuart Sandin
Edited by: Neilan Kuntz
Written by: Neilan Kuntz
Location: Bonaire Island, Dutch Territory (2001)

Kobelowsky, A. (2004) Sexual dimorphism of the Flounder, Bothus robins. (Pisces:Bothidae). Journal of Morphology 260(2):165-171.


Konstantinou, H., D.C. Shen (1995) The social and reproductive behavior of the eyed flounder Bothus ocellatus, with notes on the spawning of Bothus lunatus and Bothus ellipticus. Environmental Biology of Fishes 44:311-324.



Coral Broadcast Spawning Event

Corals have two types of reproduction †sexual and asexual. It is the sexual reproduction that results in the formation of a new genetically different offspring and reproduction, producing clones within a colony. Coral have two strategies for sexual reproduction- broadcast and brooding. Brooding species release the male gametes into the water column. When the gametes come in contact with the surface of a colony of the same species they are absorbed into the tissues were fertilization of the female gametes occurs. The fertilized eggs develop into a planulae larva. Once fully developed the planulae leave the parent colony and become planktonic before eventually settling on a suitable substrate and growing, forming a new genetically distinct colony. In contrast, broadcast spawning corals, as shown in this video, release both male and female gametes into the water at the same time. Only viable for a couple of hours, the density and timing of gametes released is critical to maximize the probability of successful fertilization in the water (Oliver & Babcock 1992). Positively buoyant, these gametes float to the surface and can form slicks on the surface of the water.
These slicks can be seen from low flying aircraft. Once fertilization has occurred, the planulae may remain planktonic for up to thirty days. Mass spawning of different species can occur during the same day. A timing divergence of a couple hours however, may occur and is vital for reproduction isolation (Knowlton et al. 1997). In the case of the Montastraea species complex, differences in gamete release times appears responsible for the speciation between closely related reproductive sibling species Montastraea annularis, Montastraea franksi, and Montastraea faveolata (Levitan et al. 2004). This video sequence shows the release of gametes from a broadcast spawning event.

Credits
Cinematography: Neilan Kuntz
Edited by: Neilan Kuntz
Written by: Dr. Olga Pantos
Location: Bocas del Toro, Panama (2003)

Knowlton, N. Maté, J.L., et al. (1997) Direct evidence for reproductive isolation among the three species of the Montastrea annularis complex in Central America (Panamá and Honduras). Marine Biology 127: 705-711.

Levitan, D.R., H. Fukami, et al. (2004) Mechanisms of Reproductive Isolation Among Sympatric Broadcast Spawning Corals to the Montastrea Annularis Species Complex. Evolution 58(2): 308-323.

Oliver, J., Babcock, R. (1992) Aspects of the Fertilization Ecology of Broadcast Spawning Corals: Sperm Dilution Effects and in situ Measurements of Fertilization. Biological Bulletin 183: 409-417.




Asexual Reproduction

Mushroom corals of the genus, Sacrophyton spp., employ several reproductive strategies that include asexual bud production. Asexual budding has been proposed as a mechanism to enable certain corals such as fungiids to recolonize a site following the mortality or injury of a parent polyp (Krupp et al. 1996). This reproductive strategy requires that the stress responsible for the parent injury permit the bud to survive to adults. A recent investigation (Gilmour 2002a) shows that the coral, Fungia fungites, undergoes asexual budding when stressed with acute sedimentation. However, asexual budding could be a last effort strategy for a stressed coral to propagate. Gilmour (2002b) found with genetic analysis that asexual buds made less contribution to the adult population compared to the sexual recruits in an area exposed to chronic and acute sedimentation. This could also be related to differences in settlement preferences between asexual buds and sexual larvae. The following footage shows a fungiid coral releasing an asexual bud in an aquarium environment. Aquarium corals of this genus are known to bud when conditions are suboptimal serving as warning signal of being stressed. Note: during the release of the bud, the coral is folded in and the polyps are retracted, but reopens and extends its polyps after one hour of the buds release. This behavior during budding may be to change hydrostatic pressure to help release the coral's bud.

Credits
Cinematography: Neilan Kuntz
Edited by: Neilan Kuntz
Written by: Neilan Kuntz
Location: San Diego State University (2004)

Gilmour, J. P. (2002a) Acute sedimentation causes size-specific mortality and asexual budding in the mushroom coral, Fungia fungites. Marine and Freshwater Research 53: 805-812.

Gilmour, J. P. (2002b) Substantial asexual recruitment of mushroom coral contributes little to population genetics of adults in conditions of chronic sedimentation. Marine Ecology Progress Series 235: 81-91.

Krupp, D. A., Jokiel, P. L. and Chartrand, T. S. (1996) Asexual reproduction by the solitary scleractinian coral Fungi scutaria on dead parent coralla in Kanehoe Bay, Oahu, Hawaiian Islands. In: Proceedings of the 7th International Coral Reef Symposium 1: 527-534.