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. |