Saturday 21 September 2013

A new species of Thecideide Brachiopod from a shipwreck off the coast of Sulawesi.

Brachiopods (or Lampshells) superficially resemble Bivalve Molluscs, though they are not closely related. They were abundant in the seas of the Palaeozoic, often dominating benthic faunas, but today are comparatively rare, and seldom seem outside the tropics. Brachiopods have a filter feeding apparatus called a lophophore, unlike anything found in any Mollusc, but also found in Bryozoans and Phoronid Worms. This is encased with in a shell with two valves, each symmetrical about a midline, but not necessarily the same as each other, along with the rest of the organs of the body; there is typically remarkably little flesh to a Brachiopod compared to a Mollusc with a shell the same size. Thecideide Brachiopods are a group of small Articulate Brachiopods (Brachiopods in which the shell has a toothed hinge, as opposed to Inarticulate Brachiopods, which have shells held together by muscle and tendons) which appeared in the Triassic and are common (for Brachiopods) today. They cement their ventral valves to hard substrates, such as rocks or the shells of other organisms, and prefer cryptic (hidden) environments.

In a paper published in the journal Zootaxa on 7 August 2013, Eric Simon of the Department of Palaeontology at the Belgian Royal Institute for Natural Sciences and Jana Hoffmann of the Museum für Naturkunde at the Leibniz-Institut für Evolutions- und Biodiversitätsforschung, describe a new species of Thecideide Brachiopod from a shipwreck in the harbour of Donggala, Central Sulawesi, Indonesia.

The new species is placed in the genus Ospreyella, and given the specific name mutiara, which means 'pearl' in Indonesian, and is the name of the wrecked ship in which the species was discovered. Ospreyella mutiara is a small-to-medium sized Thecideide Brachiopod reaching at most 4 mm. The females are larger than the males and have a distinct marsupial notch (used to hold a brood pouch in which the young, attached to specialized tentacles, are nursed prior to dispersal). The shells are whitish and biconvex.

Ospreyella mutiara. (1) Fully grown adult  attached to the substrate in (a) dorsal, (b) ventral and (c) lateral views. (2) Young specimen attached to the substrate in (a) dorsal, (b) anterior and (c) lateral views. (3) A piece of metallic substrate from the store in the shipwreck with several juvenile specimens; (a) overview, (b) detailed view of two juvenile specimens attached to the substrate and (c) detailed view of one juvenile specimen. (4) Adult specimen with a median brood pouch and larvae. (a) Opened complete articulated specimen showing the lophophore in living position. Specialized tentacles are located at the posterior part of the lophophore. (b) Dorsal view of ventral valve showing detached fibres of the adductor and diductor muscles in the posterior part of the specimen. Two calcitic oval pads cover the gonads in the visceral cavity. Exposed larvae are visible between the calcitic pads in the posterior part of the valve. (5) Adult ventral valve attached to the substrate. The two calcitic oval pads covering the gonads are missing. (a) Dorsal view showing the peripheral ridge, the surface of the valve floor, the interarea, the pseudodeltidium and one tooth. The left tooth is broken. (b) Detailed view of the hemispondylium which consists of two pointed lateral lobes and a prominent median myophragm. (6) Juvenile ventral valve attached to the substrate. The sculptured surface of the anterior part of the pseudodeltidium is very apparent. The ventral valve is coalesced with the substrate. (7) Dorsal view of the posterior part of the ventral valve. The interarea exhibits fine sub-parallel growth lines. The pseudodeltidium is convex. The hinge line is straight. The prominent protegulum exhibits a wrinkled surface. (8) Dorsal view of the pseudodeltidium and the hinge line of the ventral valve. Simon & Hoffmann (2013).

Ospreyella mutiara. (1) Very early juvenile stage with a trocholophe lophophore possessing 27 tentacles. Lateral adductor and median adductor muscles visible on the left side of the shell. (2) Early juvenile stage with a schizolophe lophophore possessing 48 tentacles. The median ramus precursor is developed. (3) Juvenile with schizolophe lophophore consisting of 55 tentacles. The median ramus is widening. Detached lateral adductor and median adductor muscle fibres are visible. (4) Developmental stage with ptycholophe lophophore. Detached lateral adductor and median adductor muscle fibres are visible. (5) Specimen considered as “male” with further developed median ramus and ramuli. A marsupial notch is missing. (6) One of the largest specimens with male features. No marsupial notch is apparent. (a) Ventral view, (b) anterior view, (c) lateral view, (d) posterior view and (e) detailed view of the entire median portion of the brachial bridge. (7) One of the smallest specimens with female features. This specimen considered as “female” possesses a brooding apparatus. Two larvae are attached to the specialized tentacles, which are removed from the median brood pouch in the ventral valve. (a) Ventral view. The median ramus and the ramuli are further developed than in the largest shell with male features. (b) Detailed view of the larvae attached to the specialized tentacles. Fragments of the broken brood pouch are still covering the larvae. (8) Specimen with female features. Three larvae are attached to the specialized tentacles. The median ramus and the ramuli are well developed. (a) Ventral view. (b) Detailed view of the marsupial notch with specialized tentacles and attached larvae. (9) A larger specimen with female features. Marsupial notch and specialized tentacles are present. No larvae are attached to the tip of the tentacles. The tentacles of the lophophore are perfectly spaced by spines on top of the major interbrachial lobe. (a) Ventral view, (b) lateral view, (c) anterior view and (d) posterior view. (10) Fully grown specimen with female features. The median ramus is uplifted and exhibits a very narrow concave crest. The anterior median depression is inconspicuous. (a) Ventral view. (b) Detailed anterior view of the marsupial notch with specialized tentacles. (c) Detailed posterior view of the marsupial notch with specialized tentacles. Simon & Hoffmann (2013).

The specimens were collected from within a shipwreck in 30 m of water at the entrance to the harbour of Donggala in Central Sulawesi, Indonesia. The ship sank 58 years ago and its interior is extremey dark, resembling a cave, which suggests that submarine caves might be the natural habitat of Ospreyella mutiara. This is the first time a member of the genus Ospreyella has been found in Indonesia, however the discovery is not altogether surprising as the genus in known from both the Indian and Pacific Oceans.

The location of the shipwreck of the Mutaria, where the Brachiopods were collected.

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