110 — Sea slug, Alloiodoris lanuginata

Alloiodoris lanuginata, Warrior Rocks,
 Mt. Maunganui, 2017.

Alloiodoris lanuginata, with coil of eggs,
Warrior Rocks, Mt. Maunganui, 2017.

The sea slug Alloiodoris lanuginata (Abraham, 1877) is another species for which there is no common name. It's endemic to New Zealand's North Island and not particularly common. They are quite coarse to the touch and feel like they are covered in fine sand paper. This coarseness comes from fine spicules contained within tiny tubercles, which cover the dorsal surface of the sea slug.

Ecologically they prefer clean, but sheltered waters and are thought to feed on sponges. But, it's not known which species of sponge they prefer.

This one was found between boulders, on Warrior Rocks, at the base of Mt. Maunganui. It had just laid a coil of eggs. It's overall size was about 80mm, which is about as large as they get.

If I see another one I hope to get better pictures.





More info:

Sea Slug Forum: Alloiodoris lanuginata

Willan, R. C.,& Morton, J. E. (1984). Marine Molluscs part II - Opisthobranchia, pp. 1–106. University of Auckland, Leigh Marine Laboratory.

109 — The rare sand chiton, Pseudotonicia cuneata

Pseudotonicia cuneata, The base of
Mt. Maunganui, Opposite Stony Point, 2017

Pseudotonicia cuneata, The base of
Mt. Maunganui, Opposite Stony Point, 2017

Pseudotonicia cuneata, The base of
Mt. Maunganui, Opposite Stony Point, 2017

There are a few dozen species of chitons (coat-of-mail shells) found on New Zealand coasts. However, as most of them could be considered to be unremarkable-looking, they aren't really noticed by your average beach-goer.

Many chitons are light-adverse and have light-sensing organs (ocelli) on their upper surface. They use these to orient themselves away from the light. As a consequence these species are often found under rocks or ledges. Most of the shallow water chitons are thought to be vegetarian grazers, feeding on algal films on hard surfaces. 

Pseudotonicia cuneata (Suter, 1907), is quite a rare and unusual chiton. It's found mostly around North Island and the top of South, at and below low tide down to a few metres deep.

What makes this chiton species unusual is that, unlike almost all other chitons, it's found in sand. But not just any sand, P. cuneata lives in areas with clean fast-flowing waters, but not those not open to wave action, and where there are also dead shells for it to attach to. These are conditions which aren't all that common, so as a consequence not many people have seen one.

It has been speculated that this species grazes on the algal films found on dead bivalve shells, as it's often found attached to them. However, this is another one of those species for which virtually nothing is known. These ones were about 40–50mm in length and from sand around the base of Mt. Maunganui during a spring low tide.

I've only ever found this species in length of beach about 10–20m long, so their habitat is quite vulnerable.



More info:


Ashby, E. (1928). The rediscovery of Tonicia cuneata Suter and Acanthochites thileniusi Thiele (Order Polyplacophora) together with the description of a new Genus and short review of the New Zealand Acanthochitonidae. Transactions and Proceedings of the Royal Society of New Zealand 1868–1961, 58, 392–607.

Powell, A.W.B. (1979). New Zealand Mollusca. Collins

108 — Striped anemone, Diadumene neozelanica

Lion Rock, Piha, 2016: this clip is a little
over-exposed. In the top left corner there is a
solitary ascidian and below that another
?dead solitary ascidian covered in
 athecate hydroids.

Piha, Jan 2017.

The striped anemone, Diadumene neozelanica* is a smallish anemone (~20 across the disc) found on the lower shore on exposed coasts throughout New Zealand. They get their common name from the light and dark brown vertical stripes on the anemone’s stalk. There are many tentacles, these are quite long and fine, and can be orange/beige in colour. They possess an inner ring of blunt-tipped catch tentacles and these are diagnostic for this species.

The plumose anemone Mimetridium cryptum, Hand 1961 is very similar, but doesn't have these catch tentacles. Apparently, both species can reproduce asexually and form large patches. The problem here is that I have imagery where there are anemones in a large patch, some with the catch tentacles and some without, so at the moment I'm not sure how reliable this feature is.

Piha, Jan 2017

Very little appears to be known regarding the ecology of striped anemones. They appear to like the shade and don't seem to be found in open sunlight. It's interesting that they are orange/beige in colour, as these are colours which absorb higher wavelengths of light; those which can penetrate deeper into the water or into more shaded areas. It may mean that they have photosynthetic zooxanthellae, but this is currently unknown.

Moturiki Island, Mt. Maunganui, 2016.

Moturiki Island, Mt. Maunganui, 2016.

* (Carlgren, 1924)




























More info: 

de Cook, S. (2010). New Zealand Coastal Marine Invertebrates 1. Canterbury University Press.

Morton, J. A., Miller, M. E. (1968). The New Zealand Sea Shore. Collins.

107 — Cheeseman's trophon, Paratrophon cheesemani

Paratrophon cheesemani, Maori Bay,
west coast of Auckland, March 2011.

Paratrophon cheesemani, between green-lipped
mussels, Maori Bay, west coast of Auckland,
March 2011.

Cheeseman's trophon, Paratrophon cheesemani (Hutton, 1882), is a small gastropod (~14mm) named after Thomas Frederic Cheeseman (1845–1923), an ex-curator at Auckland Museum. It's endemic to the northwest coast of North Island, where it lives in the lower intertidal zone of exposed coasts. There is a transition zone around Port Waikato where this form is replaced by the predominantly southern P. cheesemani exsculptus Powell, 1933.
Once these two forms are genetically analysed* they may turn out to be separate species.

Very little appears to be known regarding their ecology. However, Cheeseman's trophon is a muricid whelk and these whelks feed by boring through the shells of other animals (typically other gastropods, bivalves, and barnacles). My observations suggest that this species possibly fulfils a similar role to that of the oyster borer (Haustrum scobina (Quoy & Gaimard, 1833)), but lower on the shore, especially since vertical distributions of these two species don't appear to overlap. I suspect that this small gastropod is easily overlooked and the exposed nature of its habitat makes working on it difficult in situ.

*Barco et al. (2015) looked at P. cheesemani exsculptus but not P. cheesemani cheesemani, so no comparison was made between the two forms.



More info:

Barco A, Marshall B, Houart R, Olivero M. 2015. Molecular phylogenetics of Haustrinae and Pagodulinae (Neogastropoda: Muricidae) with a focus on New Zealand species. Journal of Molluscan Studies, 81(4): 476–488.

Paratrophon cheesemani http://www.mollusca.co.nz/speciesdetail.php?speciesid=1000&species=Paratrophon%20cheesemani

Paratrophon cheesemani exsculptus http://www.mollusca.co.nz/speciesdetail.php?speciesid=1001&species=Paratrophon%20cheesemani%20exsculptus

106 — Asian paddle crab, Charybdis japonica

Asian paddle crab, Long Bay marine reserve,
Auckland, 24/3/17.

The Asian paddle crab, Charybdis japonica * is a medium-large green-coloured crab (to ~12cm carapace width), which has become established in northeastern New Zealand. At present they are known from the Waitemata Harbour north to Whangarei Harbour, and Opua/Waitangi in Northland.

Asian paddle crabs were first detected in the Waitemata Harbour near the end of 2000. They prefer sheltered estuarine conditions and are very aggressive, with a strong and painful nip (personal experience). They reach maturity at around ~46 mm carapace width (for females) and can reproduce frequently, possibly several times a year, meaning they could become established in a new area quite quickly. However, they need the water temperature to be at least 20˚C to breed and this will probably limit their southward advance.

The invasive asian paddle crabs are of a similar size to the commercially exploited local species of paddle crab (Ovalipes catharus).  Asian paddle crabs feed on a variety of benthic species including gastropods, bivalves, and other crabs; so there is the potential for competition with local species for resources. Recently I was told that in areas where these two species co-occur, asian paddle crabs now predominate: having out-competed the local species.

* (A. Milne-Edwards, 1861)

Asian paddle crab, from under a rock,
Musick Point, Tamaki Estuary, 14/1/17.

Asian paddle crab, from under a rock,
Musick Point, Tamaki Estuary, 14/1/17.

A smaller Asian paddle crab, from under a
different rock, Musick Point, Tamaki
Estuary, 14/1/17.

And less than half a second later...

More info:

http://www.biosecurity.govt.nz/pests/asian-paddle-crab

http://www.cabi.org/isc/datasheet/89054

https://researchspace.auckland.ac.nz/bitstream/handle/2292/6659/whole.pdf?sequence=8

105 — Spotted whelk, Cominella maculosa

Cominella maculosa, low tide at Devonport,
Auckland 2015.

Cominella maculosa, Sumner, Christchurch, 1993.

The spotted whelk, Cominella maculosa * is another small to middle-sized snail (~45mm) endemic to New Zealand. It's very similar to it's near relative the speckled whelk (C. adspersa). However, spotted whelks have a slightly different distribution, tending to occur in shallower, more sheltered waters and harder substrates. They are found throughout North Island and down to at least Christchurch in the south. South Island forms are smaller and more compact than those from the north.

These two Cominella species are thought to be predator/scavengers and can often be found around carrion. Graham (1941) reported C. maculosa as feeding on the rock oyster **  and cockle *** in Manukau Harbour. However, those observations were published before the advent of the Pacific oyster #, which now dominates much of that habitat. It would be interesting to find out if C. maculosa preys on the Pacific oyster.


* (Martyn, 1784)
** Saccostraea glomerata (Gould, 1850)
*** Austrovenus stutchburyi (Wood, 1828)
# Crassostraea gigas (Thunberg, 1793)



More info:

http://www.mollusca.co.nz/speciesdetail.php?speciesid=1088&species=Cominella%20maculosa

Donald K. M. , Winter, D. J., Ashcroft, A. L., Spencer, H. G. 2015. Phylogeography of the whelk genus Cominella (Gastropoda: Buccinidae) suggests long-distance counter-current dispersal of a direct developer. Biological Journal of the Linnean Society, 115, 315–332.

Graham DH 1942. Breeding habits of twenty-two species of marine Mollusca. Transactions and Proceedings of the Royal Society of New Zealand, 71, 152–159.

104 — Absence of stingray...

Stingray 'pit', Te Matuku marine reserve,
Waiheke Island, 25/11/16.

These pictures show the pits left in the mudflat made by the feeding of stingrays, at Te Matuku marine reserve, Waiheke Island.

There are three species of stingray found in New Zealand waters and the most common is the short-tailed stingray (Dasyatis brevicaudata (Hutton, 1875)), which can grow up to 4.3m, making them the largest stingrays in the world.

Another stingray 'pit', Te Matuku marine reserve,
Waiheke Island, 25/11/16.

In the first picture, the orientation of the stingray was such that the head was pointing down to the right, so that its mouth was over where the dark hole in the mud is now. The ray then liquified the sediment beneath its head so that it could get to the invertebrates buried below the surface. If you look carefully you can see its outline in the mud. In the second picture the ray's orientation is with the mouth pointing towards the upper left of the picture. I've sharpened this shot a little to try and bring out a bit more detail.

It is thought that short-tailed stingray feed on crabs and bivalves (Ayling & Cox 1982), but these data are quite old and probably could be updated in light of the invasive species now found in the Auckland region. Stingrays share their habitat with a number of new arrivals, several of which could now be prey items.

Recent research on a closely related species from Japan has revealed that stingrays are bioengineers, and are important in the turnover and re-oxygenation of sediments (Takeucki & Tamaki 2014). By digging these pits, stingrays may therefore help to maintain a healthy mudflat ecosystem.


More info:

http://www.seafriends.org.nz/issues/res/pk/stingrays.htm#short-tailed_sting_ray

http://phys.org/news/2016-09-stingrays-food-swallowing.html

Ayling, T, Cox GJ 1982. Collins guide to the sea fishes of New Zealand. Collins, Auckland, New Zealand.

Takeuchi S, Tamaki A 2014. Assessment of benthic disturbance associated with stingray foraging for ghost shrimp by aerial survey over an intertidal sandflat. Continental Shelf Research, 84, 139–157.

103 — Micro molluscs, Micrelenchus sanguineus

Micrelenchus sanguineus, Mount Beach,
Mt. Maunganui, 2015. 

Micrelenchus sanguineus * is a small herbivorous gastropod endemic to New Zealand. They are found at and below low tide down to a few metres depth on and around the bases of seaweed in clear water locations. They are quite small (~8mm), but can be brilliantly coloured and quite attractive little shells.

North Island examples from tend to be more colourful and patterned than ones from the south, which also differ in having a heavier shell (known as the cryptus form).

*(Gray in Dieffenbach, 1843)





















More info:

http://www.mollusca.co.nz/speciesdetail.php?speciesid=241&species=Micrelenchus%20sanguineus