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

102 — Palmer's trumpet, Proxicharonia palmeri

Named after the diver who first found it at the Poor Knights Islands, Palmer's trumpet (Proxicharonia palmeri (Powell, 1967)) is a small (~50–60mm), trumpet shell found off northern New Zealand. They are much sought-after by collectors and are an attractive orange beneath a brownish periostracum.

Very little is known about their ecology, but a few have been found offshore and some at considerable depths (~500m). This species is closely related to the fossil P. neozelanica (Marshall & Murdoch, 1923), and there was speculation that they were identical, although now these two are considered separate species. They appear to live in between depths which are too deep to SCUBA dive and too close to rocky outcrops to turn up in dredges or trawls.

The P. palmeri below are from an offshore site and at the time they were collected, probably represented the largest number seen at one time.

Proxicharonia palmeri

Proxicharonia palmeri, showing the animal.

Many many Proxicharonia palmeri. This was but a sub-sample.

More info:

http://www.mollusca.co.nz/speciesdetail.php?speciesid=866&species=Sassia%20palmeri

101 — Crimson (immortal) jelly, Turritopsis rubra

Turritopsis rubra, mussel farm,
Waiheke Island, Auckland, 27/02/14.

Turritopsis rubra, south Piha, 26/04/17.

Turritopsis is a genus of small hydrozoan jellies (<10mm). There are a few species and there appears to be some debate regarding the number. They have a complex lifecycle, which starts off when eggs are released by the medusa (jelly) phase into the plankton. Assuming they survive, they then hatch and settle as a cyst-like blob and form polyps. The polyps then grow and bud off small medusa, which then swim off and grow, produce eggs, and then die. The end.

Turritopsis rubra, mussel farm,
Waiheke Island, Auckland, 27/02/14.

Turritopsis rubra, mussel farm,
Waiheke Island, Auckland, 27/02/14.

Except in Turritopsis dornii it's not necessarily the end. This species can reverse this process, so when times get tough they can revert back into a polyp and wait for conditions to improve. This lifecycle reversal is called transdifferentiation and essentially cheats death, making the jelly biologically immortal.

This transdifferentiation ability enables the jelly to survive long ocean voyages in the ballast tanks of ships and so there is a perception that these little jellies are silently taking over the world's oceans.

As a consequence of their biological immortality, there has been interest regarding the implementation of transdifferentiation in regenerative medicine. However, so far, it appears that the jellies are really hard to keep alive in aquaria making them difficult to study (which seems ironic).

The species pictured here is T. rubra (Farquhar, 1895), which has a south Pacific distribution. It is currently unknown whether this species can transdifferentiate its cells like its close relatives.

These little jellies have quite a painful sting, especially if their tentacles get trapped between a swimmer's (or surfer's) clothing and their skin. The tentacles are long and very fragile, so can break off easily. There was quite a bloom of these little jellies during the summer of 2016–17 on the North Island west coast. Many people thought they were being bitten by sea lice, when in fact they were probably being stung by these jellies. I think "being bitten by sea lice" is a myth.


More info:

Regenerative medicine: http://singularityhub.com/2011/04/25/immortal-jellyfish-provides-clues-for-regenerative-medicine/