Marine Life Society of
South Australia Inc.
Newsletter
November 2007 No. 349
“understanding,
enjoying & caring for our oceans”
Next Meeting
This will be the November General Meeting and
it will be held as usual at the Conservation Centre, on the 21st November commencing at 7.30pm.
This will be our final meeting at this venue as it has been sold for
redevelopment. At the time of writing this Newsletter I have no idea as to
where the new Centre will be sited. Watch your emails and future Newsletters.
Our guest speaker for this meeting is Peter Clements from the Natural History Trust who will be speaking on the
Trust and Wombats. Should be a very different and interesting
evening.
CONTENTS
Cleaning Stations and Cleaners (David Muirhead)
More About The
Solar-Powered Sea Slug (Steve Reynolds)
Hi
everyone,
As
I indicated above this is the end of an era. We have been at the Conservation
Centre (CCSA) since our first meeting there in February 1996. Prior to that we met at the Brighton-Glenelg Community Centre at 20
Tarlton Street, Somerton Park and various other locations.
I
wish to take this opportunity to thank the CCSA for their hospitality for the
past (almost) 11 years and for allowing our mail to be held there.
Now
we may have to seek a new venue for the next few months whilst the CCSA sets up
in new premises.
Philip
Thanks
too to all those who have contributed articles to the Newsletter and Journal
this year. Special thanks to Steve for his constant supply of excellent
articles.
Cleaning Stations and
Cleaners
by David Muirhead
We may be
looking too hard for similarities between the only known (actually, we
can’t even say this for sure, but the Western Cleaner Clingfish probably is a
dedicated full-time cleaner) dedicated southern cleaner (ie WCC’s) with a
reliance on occupying a prominent cleaning station, and any possible cleaning
behaviour by grass clingfish species.
Western Cleaner
Clingfish
Photographer -
David Muirhead
It seems
to me the habitats are so strikingly different that whereas a cleaning station
obvious to all confers a wonderful advantage in busy cluttered reefy areas
where competition for living space (free-living eg fish, crabs) and food-laden
currents (sessile, mainly inverts/algae ) as a priority must equal
or exceed in importance competition for niche hiding spots, the converse
applies way out in the middle of open sandy or sparsely grassed benthos
(to a wee grass clingfish, the bare sand surrounding seagrass clumps must look
very scary!)
Here safe
havens from pelagic predators, marauding carnivorous territorial fish
from nearby reefs eg tubemouths, as well as species
favouring grass and sand eg many flatheads, some crabs etc, are clearly at
a premium.
Also there
is not going to be much topographic variability in relief at all, (apart
from the smallish variations between longer-leaved vs
shorter-leaved seagrass clump foliage ,which will be very ephemeral
such that a good station today may be gone the next day due storms etc) so the
idea of a prominent station would seem to be restricted to either:
#1:preferentially perching near the tips of the
highest/longest seagrass blades in any grassed area,
#2:preferentially
stationing oneself in/on a small but robustly anchored, isolated ‘outlier’
grass clump, or
#3:preferentially selecting one of the above sites that is
also favourably located with regard to having adequate water movement to
deliver micro-nutrients to accelerate growth of the seagrass itself while also
favouring high densities of decapod crustacea such as mysids (an important
criteria here seems to be :the more finely shredded decaying marine plant
detritus there is lying in shallow depressions on the sandy or silty
substrate the better.)
And
perhaps one should also include ‘at the optimal depth’-whatever that is-among
these last criteria.
If depth
is indeed a major criterion for a successful station then obviously tidal
variations might themselves mean that cleaner hosts in near-shore sloping
sandy/grassy areas would do better to shift from one clump to another further
in towards or out from the strand during each tide, but clearly depth must have
some role also in determining how good a grassy/sandy site is for use as a
station, unlike in reef habitat with it’s (generally, barring eg catastrophic
sand drifts capable of burying low-relief reefs , wave action in only
the most severe storms) perennially stable relief and
landmarks topography would surely far outweigh this criterion.
Another
variable that could matter much more in open inshore areas than on reefs is
this: In this hypothetical scenario where slow-moving
pipefish constitute the main client group, cleaners that learn
to follow their clients inshore on the incoming tide and out again on the
ebb, provided they can avoid excessive mortality via predation while so doing,
would gain the advantage of a more reliable food source, with also a longer
time window in each tidal cycle to consume the food (ie parasitic eg decapod
crustacean spp living in/on the pipefish, which one assumes would have
broad similarities to those found on the non-syngnathid inshore fishes favoured
as clients by their reef-dwelling ,very successful and close relatives, the
Western Cleaner Clingfish).
Following
clients, especially such slow-moving, cryptic ones as these bizarrely camouflaged
pipefish, rather than enticing them to visit your station, may indeed be a
smart ploy. Alternatively you could describe this as moving your station
frequently to provide a better service to slow, very cryptic clients who
like you are more vulnerable out in the open and hence unlikely to risk
seeking your permanent or semi-permanent station if it means venturing any
distance across bare sand from one clump to another, as it usually
would at the sites where I’m seeing the most pipefish and which inspired
me to put these thoughts to paper.
Wide-bodied
Pipefish
Photographer -
Kevin Smith
It then
follows that if the cleaner host has accommodated it’s very specialised
clients in this manner, (ie placed it’s services as proximally as possible
to those clients without actually becoming a remora!), there is no added
advantage to be had from trying to be visible to any pipefish sheltering in
other clumps which may often be many metres away across bare sand, as
these pipefish will probably stay put, unless desperate for a clean.
I, while
scuba diving (either solo, when I always carry my ‘Spare Air’ redundant
emergency air supply, wear my ‘Shark Shield’ with fully charged 4-hour
rechargeable battery, tow a buoyed ‘diver below’ flag, in daylight, calm seas,
minimal current, good viz, depths generally under 3 metres but
often around 2 metres or less, shore entry/exit and never at unfamiliar or
remote sites, or with the likes of Kevin Smith, Graham Short, Rob Kirk of
the UEC and several others including my long-suffering life partner
Jenni) have now observed these pipefish in very shallow grassy/sandy
areas in calm embayments for many hours (100+) in recent
years.
I can
confirm that, during daylight hours at least, they are generally very reluctant
to move far from their grass clump, even if it is so small as to seem grossly
inadequate as protection should a larger predator appear on the scene.
Port Phillip
Pipefish
Photographer -
David Muirhead
Indeed
they seldom move more than a metre away if at all, for any reason short
of catastrophic disruption to their hiding place. A good example of this is
when, as has happened on odd occasions, a buddy diver has unwittingly so
violently flattened the clump of seagrass I was observing with a downward
thrust of one of his/her fins while said buddy was lying prone near the bottom
with legs stuck out behind observing, like me, another clump nearby
!
At dead
slack tide, they can be a bit easier to coax away from the clumps,
sometimes even appearing inquisitive to the point of voluntarily leaving the
clump to follow a very gently drifting diver behind and to one
side.
What
happens if you approach one of the free-ranging pipefish on
those less common occasions where numbers of them are out and about?
Often
comprising several species, this behaviour is clearly not species specific
within the modest cohort of pipefish species to which I refer.
I recall
several dives where quite a few Port Phillip, Briggs Crested, Rhino, and one or
two Pugnose Pipefish were widely scattered about in a quite extensive bare
sandy area, seemingly almost at random and without individuals seeming to have
a particular ‘home seagrass outlier clump’ in mind as a strategic retreat,
sometimes not even within a distance of up to 5-7 metres despite this
surely being a ‘far horizon’ experience for these slow, very weak swimmers. My
guess is that this patch was so particularly well endowed with mysids or
whatever their favourite food is that each pipefish felt an
individual imperative to capitalise on this feast, but probably they were still
only game for this ‘reckless’ behaviour when tide and other variables indicated
minimum predation risk!
At all
other times, even when one slowly circles closely around the particular outlier
grass clump you first find them on, they usually prefer to hide on (those with
prehensile tails eg widebody, spotted), in, at the base of, (eg Port Phillip,
Pugnose) or behind the seagrass clump. Some species seem to do this almost
to a suicidal fault, eg Pugnose and Port Phillip, others with slightly less
doggedness but still clearly reluctantly eg Widebody, Rhino and Briggs
Crested.
Pugnose Pipefish
Photographer -
David Muirhead
As noted
above there are what I as a conservation diver would see as special
occasions when one does find most of these species (especially Briggs
crested ,rhino and Port Phillip) on or very near the bottom out over bright
sandy areas many metres from the nearest seagrass clumps, and also not
uncommonly well inshore of the blue line in this same context (even as shallow
as 1 metre depth), seemingly more often when there is minimal current and
plenty of ambient light ie probably when predation risk is lowest.
But at
most other times the rule is: If you want to locate them, just glide from
(usually Posidonia spp) outlier clump to clump, stopping to carefully peruse
every part of each clump, always paying particular attention to the
bases/sheaths of the blades, where they arise from the rhizome. This is the
favoured retreat of several species notably Port Phillip pipefish,
and here they are often almost impossible to see even at close
quarters, with their bodies laying almost flat against the bottom, in parallel
with the rhizome (seagrass stolon or runner) or intertwined among the
living blades and dense drift detritus including dead leaves/blades which one
finds trapped at this same site. The longer, more mature rhizomes, which
can be quite tough and fibrous, often also have a depressed
groove-like channel in the sandy substrate underlying the linear rhizomes,
generated by tidal current or wave action, and this collects yet more
drift weed, further aiding the pipefishes' ability to avoid discovery.
...more
randoms from Lassiter’s Reef Second Valley, nothing special here but, to
everyone with an interest: I always suspect the snook (shortfin pike) one
sees idle amongst scaberia may be at cleaning stations, perhaps that of a
juvenile Blue Spotted Wrasse, or moonlighter or old wife or even a grass
clingfish, which do at times occupy scaberia (and being taller than surrounding
plants, would make a good station perhaps)-yes, idle speculation, AGAIN!
While on
subject, I also think grass clingfish at Normanville are likely candidates for
facultative cleaner role, with a focus on inshore pipefish species as clients,
for similar reasons given in my recent email re slender weed whiting S.
attenuatus.
Slender Weed whiting
Photographer - David Muirhead
Just
finding them often cohabiting in the same small posidonia outliers (almost
impossible to find any clingfish or any of the pipefish species below in main
seagrass beds nearby) of course proves nothing, but they ARE clingfish, of
similar size to the Western Cleaner Clingfish but with longer snouts? Ideal for
cleaning pipefish and they (admittedly like many inshore demersal species)
favour the same small outlying seagrass clumps where I see the vast majority of
Port Philip, Briggs Crested, Pugnose, Widebody, Spotted and Rhino Pipefish
in this shallow bay.
Hard to
believe that's just coincidence, and surely so many fish in close proximity
would be competing needlessly for the mysids/copepods etc in the immediate
vicinity (if they indeed have similar diets or at least overlapping dietary
preferences which admittedly I don’t know either!!)
Other
variables could explain all this eg mysids et al might be found in much higher
densities here, sufficient to override the inter-species competition factor,
but even looking amongst the seagrass beds on occasions there are still teeming
hordes of them yet one still cannot locate any clingfish or pipefish other
than along edges (scarce pipefish, NO clingfish) or especially in outlier
clumps (plenty of both, at right times of year).
Tubemouth
Photographer -
David Muirhead
Another
possibility could be this: if Tubemouths (S argyrophanes) which are as
common here as anywhere (ie if I want to find one, this bay is my best hope,
but still much scarcer or difficult to locate dive to dive) do eat grass
clingfish and/or slower pipefish species (eg all the above listed species, but
not the larger, faster, more wide-ranging Brushtail Pipefish which
interestingly are also common here but in my experience almost always
over large seagrass beds or with low reef mixed w seagrass-rarely if ever
do Brushtails venture out over sand or hang around outlier clumps) then
both grass clingfish and slow cryptic pipefish would be easy prey for the
‘stalk and pounce’ behaviour of these very stealthy, brilliantly cryptic
tubemouths, but Tubemouths themselves, while bigger than most pipefish and all clingfish,
are vulnerable out over sand so tend not to visit these outliers. They however
often lurk in the seagrass near edges of large beds, suggesting they may prey
upon the smaller demersals that must often have no choice but to run for this
cover, eg if stronger wave or tidal action or pelagic predators forced
them off their outlier clumps.
I’ve used
the Tubemouth (a type of weed whiting) as an ideal example for the purpose
above, but clearly other inshore fish groups eg the seemingly ‘garbage-guts’
wrasses and leatherjackets, most of which spend most time in reefy or
weedy/grassy areas and much less often venture far out over sandy expanses,
would fit the mould too.
Again, that's all for
now folks....
More About
The Solar-Powered Sea Slug
by Steve Reynolds
Since completing
my March 2007 newsletter article titled “Even More Nudibranch Discoveries” I
have found more information about the aeolid nudibranch Pteraeolidia
ianthina. This was the solar-powered sea slug found at Port Noarlunga reef
by Paul Macdonald on 18th June 2006.
Here (yet again)
on page 14 is Paul’s photo of the Pteraeolidia ianthina which featured
on page 10 of our 2006 Journal (described as Flabellina species).
Pteraeolidia ianthina
Photographer - Paul Macdonald
Bill Rudman of
the Sea Slug Forum had commented that the nudibranch’s “white colour suggest it
has not yet started to farm zooxanthellae in its
body, so I presume it is quite young”. It seems
that solar-powered sea slugs are so-called because they
harness solar energy. Bill said that “Pteraeolidia has evolved a method
of capturing and farming zooxanthellae (microscopic
plants) in its own body. The plants flourish in this protected environment and,
as they convert the sun's energy into sugars, they pass a significant
proportion on to the nudibranch for its own use.” and “White juveniles are
usually found in lush growths of short “turfing”
hydroids, but until now no sign of zooxanthellae has
been found in the hydroids. Adults can last some time without feeding,
presumably obtaining sufficient nourishment from their zooxanthellae
gardens. The large solitary hydroid is the preferred adult food.”
Pages 114-5 in Neville Coleman’s book “1001 Nudibranchs” features several photos
of Pteraeolidia ianthina. Not one of the specimens look
similar in any of these photos.
A photo taken by a James Robins is featured in the
December 2004/January 2005 issue of “Sportdiving”
magazine (No.107). It is on page 51 as part of Neville’s “Indo-Pacific Identity
Crisis” column. James Robins found a 1cm specimen of Pteraeolidia ianthina during
a night dive in early June at about 18m in Jervis Bay, NSW. Neville describes
it as a juvenile form of Pteraeolidia ianthina, saying that “the very small
ones appear to have cerata much closer together and
as they grow these are spread out more along the body. Although the adults can
be blue, brown, purple or a mixture of several colours when they have various zooxanthellae living in their tissues, the juveniles are
always white. However, the oral tentacles always have purple bands.”