Hastula inconstans
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Housing of Hastula inconstans |
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| ( Hinds , 1844) |
Hastula inconstans (common synonym : Impages inconstans ) is the name of a snail from the family of terebridae that the Indo-Pacific is widespread and polychaete (Polychaeta) eats. She rides the waves on sandy beaches and kills her prey with her poison in the trough of the waves.
features
The ogive-shaped, a wide casing mouth and no longer comprising 12 whorls shell of Hastula inconstans achieved in adult worm a length of about 3 cm and 7 mm wide and has a glossy surface with irregular, low, but angled, axially extending ribs is sculpted. A string-shaped fasciola sits at the base of the bowl. The siphon channel is short, the outer lip of the housing mouth is notched at the back, but widened at the front. The spindle has a callus. In this type there is no groove in front of the seam and the surfaces between the ribs are smooth. While the seams are colored white, the surrounding areas are brown to greenish-brown with a slightly paler central stripe. The coloring is most saturated between the ribs, and the area around the body is covered with an additional white stripe on the periphery. The case mouth is brown, the spindle white.
distribution and habitat
Hastula inconstans is common in the Indo-Pacific from India to the Marquesas Islands and the Hawaiian Islands. In India it can be found on the coast of Tamil Nadu , Tranquebar and the Andaman Islands . It lives on sandy beaches that are directly exposed to coastal surf.
Development cycle
Like all screw snails, Hastula inconstans is sexually separate. In contrast to the genus Terebra, the male does not follow the female's mucus trail, but may come across it more by chance in order to then mate it with his penis . The female lays about 1 to 2 mm long and wide capsules in parallel rows on 1 to 2 mm large basalt particles under rocks. Each capsule contains around 40 eggs with a diameter of around 100 µm. The further development is not known, but due to the tiny protoconch of the snails, only a very short free-swimming phase of the Veliger larvae or even a direct development within the egg capsule can be concluded.
nutrition
Hastula inconstans feeds on sedentary Vielborstern (Polychaeta) family Spionidae . On the sandy beaches of Kauai , Maui and Hawaii , Dispio magna , a detritus eater that picks up food particles with its two palps , has been observed as the sole food. The snail lives dormant buried in the sand that it leaves to forage. The prey is caught in connection with the swell, whereby the snail is able to ride on the water, identifies prey worms exposed in the trough and seizes them with the propodium . The snail quickly stretches its lip tube towards the prey and pushes the buccal tube forward in the tube so that the radula comes into contact with the prey and pierces a hole in it with a radula tooth. The snail pounces on the victim and releases a milky poisonous substance that gets through the stab wound into the prey and immobilizes it. The victim or a larger portion of the same is swallowed whole in less than a minute into the lip tube (rostrum), but the absorption through the actual mouth into the intestinal canal takes much longer. To do this, the snail and its prey quickly dig into the sand before the next wave comes. Until then, only the apex of the snail shell looks out of the sediment.
literature
- Walter O. Cernohorsky: Tropical Pacific marine shells: Family Terebridae. Pacific Publications, Sydney / New York 1978. pp. 146–150, here p. 149.
- Bruce A. Miller (1979): The Biology of Hastula inconstans (Hinds, 1844) and a Discussion of Life History Similarities among other Hastulas of Similar Proboscis Type. Pacific Science 33 (3), pp. 289-306.
- R. Venkitesan, AK Mukherjee (2012): Contribution to the knowledge on Indian marine molluscs: Family Terebridae. Records of the Zoological Survey of India 111 (3), pp. 49-77, here pp. 55f.
Web links
- Fischhaus Zepkow: Family Terebridae - screw snails
- Terebridae. From: JM Poutiers: Gastropods . In: Kent E. Carpenter, Volker H. Niem (Eds.): FAO Species identification guide for fishery purposes. The living marine resources of the Western Central Pacific. Volume 1: Seaweeds, corals, bivalves and gastropods. Food and Agriculture Organization of the United Nations, Rome, 1998. pp. 629-636, here 635.