Marine Life Society of South Australia
Inc.
Newsletter
October 2007 No. 348
“understanding, enjoying & caring for
our oceans”
Next Meeting
This will be the October Meeting and it will
be held as usual at the Conservation Centre on the 17th October commencing at 8.00pm.
Our guest speakers are John and Ellie Coulter who will be talking about their experiences in “Diving
at Garden Island”.
CONTENTS
Australian Giant Cuttlefish (Robert Browne)
The Occurrence Of The Nudibranch Crosslandia
Viridis In South Australian Waters (Steve Reynolds)
Our
stock of 2008 calendars is now down to double figures. If you want any then
please contact me soon. These are the main pictures.
Australian Giant Cuttlefish
Dr Robert Browne
Seadragon
Foundation Inc.
Prelude: The
document is an expanded excerpt for a “Conservation Guide” for the proposed BHP
Billiton Desalination Plant at Port Bonython, Upper Spencer Gulf. The evolving
“Conservation Guide” is available at (SFI 2007).
http://www.seadragonfoundation.org/SFI%20Articles/Articles.htm
The Australian
giant cuttlefish (Sepia apama), protected syngnathids, recreational and
commercial fish, and unique ecosystems are of significance to the sustainable
management of marine biodiversity in the Port Bonython area (SFI 2007). Port
Bonython is located on Point Lowly. The Australian giant cuttlefish is a
species of special consideration because of their large spawning aggregations
at Point Lowly and at other sites in the region (Steer and Hall 2005; ABC 1, 2
provide news stories). The spawning dynamics of the Australian giant cuttlefish
at Point Lowly are unsurpassed in sophisticated sexual mimicry (Hanlon et al.
2005).
The shoreline
reefs at Point Lowly and the surrounding areas support large and unique
spawning aggregations of the Australian giant cuttlefish (Sepia apama)
of high conservation and biological significance. The specific geographical
source the aggregating cuttlefish, and their migration routes and means of
navigation to the close inshore reefs around Point Lowly are unknown (Steer and
Hall 2005).
The Australian
giant cuttlefish is a very large, widespread and abundant cuttlefish species.
Estimates of maximum size vary of mantle length (mantle length is the body only
excluding the head and tentacles) but a published value is 520 mm mantle length
and a weight of 6.2 kgs (PIRSA 1,2,3., 2007; Steer
and Hall 2005). Divers claim to see much larger Australian giant cuttlefish
especially in the Solitary Islands, NSW (N. Skinner pers. comm.).
Whyalla Cuttlefish
Photographer – Paul Macdonald
Australian giant
cuttlefish range across the whole of southern Australia from northern New South
Wales, south to the north coast of Tasmania, and west to Ningaloo, Western
Australia. The east coast and southern Australian populations of Australian
giant cuttlefish form one relatively continuous population (Kassahn
et al. 2004). However, within this population there are 5 discernable groups
with the breeding aggregation north of Whyalla representing a separate
sub-population from the rest of SA, with the zone of overlap at about Wallaroo
(B. Gillanders, pers. com).
Over most of
their range, usually only two or three Australian giant cuttlefish are found mating
and laying eggs in caves on reefs. However, every winter in the Whyalla area,
South Australia, tens of thousands of giant Australian cuttlefish aggregate to
spawn over the shallow inshore rocky reefs and artificial rocky structures
close inshore in about 3-10 meters depth. The cuttlefish start arriving from
Whyalla, and 20 km north east across False Bay to Point Lowly then north all
along the coast to Black Point (B. Gillanders pers
com), in early May and reach peak numbers by the start of June (Steer and Hall
2005).
Between 4 on
average and up to 11 males compete for one female. Females can mate seventeen
times a day with two to eight males. Successful fertilization did not differ
between males paired or unpaired with females, or depend on size or sneaker
males. Sneaker males are males that mate with females while the females are
primarily consorted by another male. There are several strategies adopted by
sneaker males to approach females with a consort, to approach while the consort
is repelling another male, by using hidden stealth for example mating with
female hidden under rock, and most unique to these cuttlefish mimicking the
appearance and behavior of females (Hanlon et. al. 2005, Hall and Hanlon 2002).
The male
cuttlefish mimic females by hiding their obviously specialized male arms,
adopting the mottled skin pattern of females, and shape their other arms to
look like a female laying eggs. The sneaker males can change from the male to
female appearance ten times in five minutes. This strategy is successful about
50% of the time in achieving mating and two out of three times in achieving
fertilization (Hanlon et. al. 2005, Hall
and Hanlon 2002).
Females used all
their sperm as well as sperm from previous matings to fertilize eggs, and 70%
of clutches have multiple sires. Therefore, the mating system of Australian
giant cuttlefish has a high level of multiple mating and multiple paternity and
that males of any size or status can obtain successful fertilizations (Naud et al. 2004; Hall and Hanlon 2002; Norman
et. al. 1999). In the Point Lowly area the spawning dynamics of the
Australian giant cuttlefish, driven by the high operational sex ratio and the
high densities in the aggregation, are unsurpassed at a global scale in
sophisticated sexual mimicry. The operational sex ratio is exceptional because
of the fluidity of change between one type of sneaking behavior and the sneak
behavior of female mimicry (Hanlon et. al. 2005). The elaborate colour and pattern displays of the Australian giant cuttlefish
are legendary (Hall and Hanlon 2002) and it is intuitive that the cuttlefish would have exceptional colour
vision to match.
Cuttlefish can
see clearly. They have a unique arrangement of an invertebrate’s visual system
with a vertebrate like one. Cuttlefish have an active iris and a rectangular
expanding and contracting pupil. They also change the position of their lens to
focus like a camera lens system and this part of their visual system is
excellent. However, in spite of the mechanical advantages their vision is
restricted by a low number of photoreceptors.
Close
up of a cuttle eye
Photographer
– Neville Skinner
The skin colour
of some fish groups (Ramachandran et al. 1996) and
many cephalopods change in response to visual stimuli (Hanlon and Messenger
1988). Eyes need at least two colour pigments to see colour. However, there is
only one color pigment in the eyes of the common cuttlefish (Sepia officinalis) (Bellingham et al. 1998). How cuttlefish mimic chromatically rich environments,
found in shallow well lit waters is unexplained (Mathger
et al. 2006).
Colour changes
in cephalopods are controlled by nerves and muscles and can occur rapidly.
Other animals slowly change their body colors mainly through hormones.
Cuttlefish can match black and white backgrounds from birth and are good at
mimicking contrasting backgrounds and quickly mimicking patterns contrasting in
shade of greater than 15% difference in intensity (Mathger
et al. 2006). For comparison owls can differentiate 1% contrast (Porciantti et al. 1989) and human 2% (Lythgae
1979, p279). However, backgrounds of different colour such blue and yellow of
the same shade are recognized as uniform (Hanlan and
Messenger 1996). Cuttlefish can see polarised light
like many marine animals. This possibly enables cuttlefish not to be
disorientated by flare caused by scatter from above.
After mating
females lay about 5-39 eggs a day and 200 eggs in total, individually within
protective casings, with the eggs attached to the underside of flat rocks and
in tight hard to get at spaces among crevices in reefs (Hanlon et al. 2005).
Australian giant cuttlefish appear to use artificial as well as natural
substrata for deposition of their eggs. Anecdotal evidence suggests that
cuttlefish will fix eggs to other man-made objects, such as corrugated iron
thrown into the water in the vicinity (Steer and Hall 2005). Cuttlefish spawn
in the rock walls of the Whyalla Boat Harbour as well as on the more extensive
artificial rock walls adjacent to the steelworks. The eggs hatch within three
to five months, depending on the water temperature, with hatchlings looking
similar to their adult form. Hatchlings
appear in early September (PIRSA 1).
After spawning
most adult cuttlefish then mysteriously disappear again by the end of August
(PIRSA 2). Australian giant cuttlefish are solitary animals when not breeding.
Daytime activity cycles showed individualistic behavior. Australian giant
cuttlefish live in dens, or hover under rocks and emerge during daylight for
short food excursions. The cuttlefish enhances this conservative lifestyle with
efficient foraging while exposure to predation is minimized (Aitkin et al.
2000).
A straight line
between the One Steel Jetty at Whyalla to the east at Point Lowly encloses
False Bay (a closure area for cuttlefish fishing) where tens of thousands of
cuttlefish aggregate to mate and spawn. The closure area includes all waters
enclosed by a line from the light house at Point Lowly to the southern end of
the Port Bonython jetty, then in a south westerly direction to the eastern most
point of the One Steel jetty, position latitude 33º 02” 12.63’ south and
longitude 137º 36” 1.98’ east, near Whyalla, then to the high water mark at the
base of the jetty, then following the high water mark along the shoreline in an
easterly direction back to the point of commencement (Map grid GDA94).
Australian giant cuttlefish also spawn at Black Point northward form Point
Lowly across Fitzgerald Bay (Steer and Hall 2005).
In the
mid-1990s, an overseas market was discovered for the Australian giant
cuttlefish and export licenses were granted. In 1997, 26 boats took 262,000 kg:
that is approximately 60,000 cuttlefish over a full breeding season and
cuttlefish numbers dropped dramatically. The boats and commercial fishers were
black with cuttlefish ink. Thousands of dollars a day could be made by
harvesting the aggregated spawning cuttlefish. The Australian giant cuttlefish
fishery in the area has since been regulated and a closure created in False
Bay. Australian giant cuttlefish are also caught by recreational fishers in the
Whyalla (Steer and Hall 2005).
Upper Spencer
Gulf is home to an expanding marine-based ecotourism industry. The unique
spawning aggregations of the charismatic Australian giant cuttlefish were
devastated by excessive fishing. Now with greater protection from fishing the
cuttlefish are now recovering. However, the minimum biological and practical
requirement for eco-tourism should be recovery of the spawning aggregation to
pre-fishery levels.
A boat based and shore based diving
industry exists in the area dependent on the Australian giant cuttlefish. At
Point Lowly platforms are in place for divers to walk down to the water. From
the platform, divers cover about twenty meters over flat rock and then swim
into six meters of water. Water temperatures during the spawning season can be
as cold as twelve degrees centigrade.
Suggestions from the public of how
ecotourism could contribute to Australian giant cuttlefish conservation are; the
establishment of spawning reefs including rock walls and breakwaters,
monitoring of sites, and provision of exclusion zones to fishing for around all
Australian giant cuttlefish aggregation reefs in the region. There are
unprotected spawning aggregations to the north of Point Lowly. Artificial
spawning sites need depth as Australian giant cuttlefish normally spawn in 3
-10 m of water (Steer and Hall 2005).
Australian giant cuttlefish spawn in
the rock walls of the Whyalla Boat Harbour as well as the more extensive
artificial rock walls adjacent to the steelworks. There appears to be potential
to establish additional artificial habitat south of Whyalla (Steer and Hall
2005).
References:
ABC 1. 2007. Australian Broadcasting Commission. http://www.abc.net.au/7.30/stories/s141788.htm.
ABC 2. 2007. Australian Broadcasting Commission.
http://www.abc.net.au/northandwest/stories/s1668412.htm?backyard).
Aitkin JP, O’Dor RK, Jackson GD. 2000. Rapt
viewing: A day in the energetic life of the giant cuttlefish (Sepia apama)
Bulletin of Marine Science: Vol. 71, No. 2, pp. 1113–1146.
Bellingham J, Morris AG, Hunt DM, 1998. The rhodopsin gene of the cuttlefish Sepia officinalus sequence and spectral tuning. Journal of
Experimental Biology. 210: 2299-2306.
Hall KC, Hanlon RT. 2002. Principal features of the mating system of a
large spawning aggregation of the giant Australian cuttlefish Sepia apama
(Mollusca : Cephalopoda). Marine Biology, 140 (3): 533-545.
Hanlon RT, Naud MJ, Shaw PW, Navenhand
JN. 2005. Transient sexual mimickry leads to
fertilization. Nature. 433. Jan 2005. p212.
Hanlon RT, Messenger . 1996. Cephalopod Behaviour. Cambridge University
Press.
Hanlon RT, Messenger JB. 1988. Adaptive coloration in young cuttlefish (Sepia officinalis L.):The morphology and development of body
patterns and their relation to behaviour. Phil. Transactions of the Royal
Society of London. B 320: 437-487.
Kassahn KS, Donnellan SC,
Fowler AJ, Hall KC, Adams M, Shaw PW. 2004. Molecular and
morphological analyses of the cuttlefish Sepia apama indicate a complex
population structure. Marine Biology 143
(5): 947-962.
Lythgae JN. 1979. The ecology of vision. Oxford: Oxford
University Press.
Mathger LM, Barbosa A, Miner S,
Hanlon RT. 2006. Color blindness and contrast perception in cuttlefish (Sepia
officinalis). Vision Research 46: 1746-1753.
Naud NJ, Hanlon RT, Hall KC, Shaw PW, Havenhand JN.
2004. Behavioral and genetic assessment of reproductive success in a spawning
aggregation of the Australian giant cuttlefish, Sepia apama. Animal
Behavior. 67(6): 1043-1050.
Norman MD, Finn J, Tregenza
T (1999) Female impersonation
as an alternative reproductive strategy in giant cuttlefish. Procedings of the Royal Society of
London. B 266: 1347–1349
PIRSA 1. 2007. Primary Industry and Resources South Australia. http://www.pir.sa.gov.au/pages/fisheries/rec_fishing/mf_cuttle.htm:sectID=2081&tempID=65).
PIRSA 2. 2007. Primary Industry and Resources South
Australia. http://www.pir.sa.gov.au/pages/fisheries/rec_fishing/rec90.htm:sectID=299&tempID=10)
PIRSA 3. 2007. Primary Industry and Resources South
Australia. (http://www.pir.sa.gov.au/byteserve/aquaculture/aquafishfactsheets/snapfarm.pdf).
Porciatti V, Fortanese G, Bognali
B. 1989. The electro-retinogram of the little owl (Athene noctua).
Vision Research 29: 1693-1698.
Rachmachandran VS, Tyler CW, Gregory RL, Rogers-Rachmachandran
D, Duesing S, Pillsbury C et al. 1996. Rapid adaptive
camouflage in tropical flounders. Nature 379: 815-818.
SFI. 2007. “Conservation Guide” for the proposed BHP
Billiton Desalination Plant at Port Bonython, Upper Spencer Gulf. Seadragon Foundation Inc.
http://www.seadragonfoundation.org/SFI%20Articles/Articles.htm
Steer MA, Hall KC. 2005. Estimated abundance and biomass
of the unique spawning aggregation of the giant Australian cuttlefish (Sepia
apama) in northern Spencer Gulf, South Australia. Report to Coastal Protection Branch,
Department for Environment and Heritage, South Australia. South Australian Research and Development
Institute (Aquatic Sciences), Adelaide, RD 05/0012-1.
The Occurrence Of The Nudibranch Crosslandia
Viridis In South Australian Waters
by Steve
Reynolds
Steve
Leske, the Reef Watch Project Officer, found (and photographed) an unusual
green sea slug whilst diving at Edithburgh on the Yorke Peninsula during June
2007. Steve’s photo of the creature can be viewed in the Reef Watch Newsletter
Issue 10.2, June 2007 or at http://www.reefwatch.asn.au/PDF/Issue_10_2.pdf
.
Steve
described the slug as looking like ‘origami’, with paper flat ‘wings’.
The slug had some tiny, iridescent blue spots dotted around its body. There was
some conjecture at the time that the slug may have been the nudibranch Crosslandia viridis.
The Sea Slug
Forum at
http://www.seaslugforum.net/showall.cfm?base=crosviri
classifies Crosslandia viridis as
follows: -
Order: Nudibranchia
Suborder: Dendronotina
Family: Scyllaeidae
It gives the
distribution of the species as “Tropical Indo-West Pacific”.
There are
several photos of specimens which all look quite different to each other.
The forum’s Bill
Rudman describes Crosslandia viridis as follows: -
“This strangely
shaped dendronotoidean nudibranch looks very like a
species of the sacoglossan genus Elysia.
The rhinophores are hidden in small pockets at the
tip of the tentacle-like extensions to the front edge of the mantle. Crosslandia is closely related to Notobryon and Scyllaea,
the latter adapted for life on floating pieces of brown algae. All members of
the family feed on hydroids living on algae. Only one species (of Crosslandia) is recognised from the Indo-West
Pacific and it ranges from bright green to dull brown, apparently matching the
algae or seagrass it is living on.”
Crosslandia viridis has already
been recorded at Point Turton, Yorke Peninsula by Stuart Hutchison & Ron
Greer in 1998. So much for a distribution of
‘Tropical Indo-West Pacific’! Visit
http://www.seaslugforum.net/display.cfm?id=2876
for details re
the Point Turton sighting.
Bill was away
about the time of Steve’s discovery so any contact with the Sea Slug Forum was
delayed for a short while. Steve submitted the details (and photograph) of his
discovery to the Forum on 23rd July 2007, saying, “This is another
sighting from South Australia. Locality: Edithburgh, 2-3 metres, South
Australia, Gulf St Vincent, 10 June 2007.”
Bill Rudman’s
immediate response was “Your animal looks very like the Crosslandia
viridis I recall from East Africa. It will be
very interesting to see whether all the animals I have grouped here under
that name turn out to be the same species.”
Sightings of Crosslandia viridis reported
through the Sea Slug Forum included specimens of between 5mm and 26mm long.
There is just
one photo of Crosslandia viridis in Neville Coleman’s “1001 Nudibranchs” book.
It was taken by Julie Marshall at Heron Island on the Great Barrier Reef in
March 2001. Julie’s specimen of Crosslandia
viridis, which was found at low tide, was just
8mm long. Neville calls Crosslandia viridis ‘Green Crosslandia’. He
says that the habitat of Crosslandia viridis is coral reef.
Rudie Kuiter
found a relative of Crosslandia viridis at Kangaroo Island in March 1978. His 35mm
specimen of Scyllaea pelagica
was found in seagrass meadows at a depth of 5m. Two of Rudie’s
photos of Scyllaea pelagica
are on page 100 of “1001 Nudibranchs” (following Julie Marshall’s photo of Crosslandia viridis). Neville
calls Scyllaea pelagica
‘Pelagic Scyllaea’. Both Scyllaea
pelagica and Crosslandia
viridis belong to the family Scyllaeidae.
The Sea Slug
Forum species list at
http://www.seaslugforum.net/specieslist.cfm
lists the
following species as belonging to the family Scyllaeidae:
-
Crosslandia daedali
Crosslandia sp. 1
Crosslandia viridis
Notobryon wardi
Scyllaea pelagica
The web page at
http://www.seaslugforum.net/factsheet.cfm?base=scylpel
says that the
distribution of Scyllaea
pelagica is “Worldwide, living pelagically attached to pieces of floating kelp or Sargassum
weed, where they feed on attached hydroids”.
According to the
web page at
http://www.seaslugforum.net/factsheet.cfm?base=notoward,
Scyllaea
have a medio-dorsal posterior crest which they use as
a 'paddle', by vigorously waving it from side to side, to swim when disturbed. Notobryon wardi also
have a medio-dorsal posterior crest, like Scyllaea pelagica, for
‘paddle-swimming’.
The webpage also
says that both Scyllaea and Notobryon have dendritic
gill-like processes on the inside of the mantle lobes, especially in larger
specimens. It also says that Notobryon feeds
on hydroids and is closely related to Scyllaea
pelagica and Crosslandia
viridis. It differs from both in lacking a
median tooth in the radula and from Crosslandia, in having a medio-dorsal
posterior crest, which is absent in Crosslandia.
So, Crosslandia
viridis does not possess a medio-dorsal posterior crest for ‘paddle-swimming’ like Scyllaea and Notobryon.
Part 2 of Neville Coelman’s
article titled “All About Nudibranchs Defence Mechanisms”, published in the
June 2007 issue of Dive Log magazine, discussed the swimming escape response of
nudibranchs and other opisthobranchs. He says that
“Various species of nudibranchs react to imminent danger or interference by
rising off the bottom and swimming away from the point of disturbance”. He
mentions the Spanish Dancer, other species of nudibranchs, and also sea hares
and Bat-wing sea slugs.