IDENTIFICATION OF THE SHORE BARNACLES OF THE MALTESE ISLANDS

Transcription

1 University of Malta Department of Biology BIO Field Biology IDENTIFICATION OF THE SHORE BARNACLES OF THE MALTESE ISLANDS 1a. Shell flattened. The joint between the terga and the scuta forms an angle with the median line which is much less than 90. The tergo-scutal membranes are of a dark brown colour Euraphia depressa 1b. Shell not flattened. The joint between the terga and the scuta forms an angle of about 90 with the median line. 2 2a. The aperture is oval or sub-circular. The joint between the terga and the scuta intersects with the median line at about ⅓ of its length and is concave with respect to the carina (it has the shape of an ψ). 2b. The aperture is kite-shaped. The joint between the terga and the scuta intersects with the median line at less than ⅓ of its length (i.e. it is closer to the carina) and is more straight or only very slightly concave with respect to the carina. Chthamalus stellatus Chthamalus montagui carina tergum scutum Chthamalus montagui Scale bars = 1mm Euraphia depressa Chthamalus stellatus

2 IDENTIFICATION OF THE COMMONER ROCKY SHORE GASTROPODS OF THE MALTESE ISLANDS 1a. Gastropod has a loosely coiled shell cemented to the rock. 2 (vermetids) 1b. Gastropod has a normal helicospiral shell that is free (not attached to any substratum). 3 1c. Gastropod has a shield-shaped shell without any coiling that is free (not cemented to the substratum although it may be very tightly attached). 2a. Usually found singly or in small groups. Animal inside shell appears white or yellow and without a dark operculum blocking the mouth of the shell. 2b. Usually found in large groups that completely cover the rock to form a small reef. Animal inside shell appears dark due to a purple-balck operculum blocking the mouth of the shell. 3a. Mouth of shell without teeth. 3b. Mouth of shell with one strong tooth on inner lip. 3c. Mouth of shell with a row of small teeth on outer lip. 4a. Shell with a very broad base and a low spire (i.e. as wide or wider than long). 4b. Shell with a narrow base and a high spire (i.e. longer than wide). 5a. Shell of a greenish ground colour with fine crimson lines running obliquely across the whorls. Base of shell flat. 5b. Shell of a greenish ground colour with fine crimson lines running obliquely across the whorls. Base of shell concave. 6a. Small, dark coloured, almost black shell, or with at least a broad dark brown spiral band. 6b. Greyish shell with a checkerboard pattern of white and brown checks. 7a. With at band of alternating reddish and white rectangles below the suture; additional similar bands may be present on the wholes superimposed on a differently coloured background. 7b. Shell with a uniform pattern of alternating dark and light flecks, without any bands of alternating reddish and white rectangles below the suture. 8a. Toothed inner margin of outer lip concave. patellid limpets Vermetus triquetrus Dendropoma petraeum 4 7 (Phorcus spp.) 8 5 (Gibbula spp.) 6 (littorinids) Gibbula divaricata Gibbula rarilineata Melarhaphe neritoides Nodilittorina punctata Phorcus articulatus Phorcus turbinatus Pisania striata

3 8b. Toothed inner margin of outer lip with an inwards fold. Columbella rustica Vermetus triquetrus Gibbula rarilineata Melarhaphe neritoides Nodilittorina punctata Phorcus articulatus Phorcus turbinatus Pisania striata Columbella rustica

4 IDENTIFICATION OF THE PATELLID LIMPETS OF THE MALTESE ISLANDS 1a. Pallial tentacles colourless and translucent. External surface of shell with rows of black spots alternating with dark radial bands. Patella rustica 1b. Pallial tentacles white and opaque. External surface of shell with or without radial bands but without rows of dark spots. 2 2a. Three types of pallial tentacles present, one much longer than the other two. Radial bands usually absent or if present are not very distinct. 2b. Two types of pallial tentacles present, one only slightly longer than the other. Distinct radial bands usually present. Patella caerulea Patella ulyssiponensis Patella rustica Patella caerulea Patella ulyssiponensis

5 OTHER COMMON ANIMALS ON MALTESE ROCKY SHORES 1a. Shell made of eight articulating plates surrounded by a girdle with conspicuous alternating light and dark banding. Lepidochitona corrugata 1b. Shell made up of two valves (bivalve) 5 2a. Gastropod shell with a hermit crab inside. The chelae are more or less equal in size, are reddish and have black tips. Clibanarius erythropus 2b. Typical crab (does not live in a gastropod shell). 6 2c. Typical shrimp; long rostrum with spines; transparent with some white, black and yellow lines; in rockpools or amongst algae in very shallow water. 3a. Sea anemone; green or grey-green tentacles with pink or red tips. Palaemon elegans Anemonia viridis 3b. Sea anemone; deep red colour including tentacles. Actinia equina 4a. Colonial ascidian; coloured zooids embedded in a gelatinous matrix; zooid arranged in a star-shaped pattern. 4b. Colonial ascidian; coloured zooids embedded in a gelatinous matrix; zooid arranged in irregular rows. 5a. Small bivalve (length 10-20mm) with fan-shaped shell; dark brown, no ribs on shell. 5b. Small bivalve (length 20-30mm) with fan-shaped shell; dark brown, prominent ribs on shell. 6a. Square carapace of a dark olive green colour with brown or reddish brown mottling. No spines between eyes. Legs not striped. 6b. Rounded carapace with conspicuous spines between eyes; legs striped light and dark and armed with conspicuous spines. Botryllus schlosseri Botrylloides leachii Mytilaster minimus Brachidontes pharaonis Pachygrapsus spp. (see Note 1) Percnon gibbesi

6 Mytilaster minimus Palaemon elegans Brachidontes pharaonis Percnon gibbesi Pachygrapsus marmoratus Note 1: Check that the crab has two postorbital spines. If it does, it is Pachygrapsus marmoratus. If it has only one post-orbital spine, it may be one of the other two species of Pachygrapsus consult the tutor. 1. Pachygrapsus marmoratus 2. Pachygrapsus transversus 3. Pachygrapsus maurus