03 Patella depressa. Length 26 mm. Lleyn, Wales. September 2015.
Exterior has sculpture of narrow radiating whitish ribs that project as points from the aperture-rim of unworn shells.
Grooves between ribs are brown where uneroded.
Key id. features BELOW.
SPECIES DESCRIPTION part A 1Pd flic.kr/p/BaSA3C
SPECIES DESCRIPTION part B 2Pd flic.kr/p/AfbFkR
OTHER SPECIES ALBUMS www.flickr.com/photos/56388191@N08/collections/
Identification of British patellid limpets.
With the exception of shells with height >50% of length (only P. vulgata grows that high, but many P. vulgata have low shells), shell-exteriors cannot be relied on, and shell-interiors can be confusing. Examination, in good light under magnification, of extended pallial tentacles on living animals is essential for consistent accurate discrimination of the three rock-dwelling Patella species. Best achieved with specimen adhering to underside of supported glass-sheet in black-based container of seawater.
Some morphologically intermediate forms can only be reliably identified by sequencing DNA or allozyme study 36Pd flic.kr/p/BdwtN8 and 37Pd flic.kr/p/AzydCD . Intermediates result from similar environmental factors affecting different species in similar ways and are not hybrids (Sanna et al., 2011 and Sá-Pinto et al., 2007). For the purpose of recording for distribution schemes it is advisable to disregard intermediates unless DNA or allozymes can be employed, especially beyond or on the limits of known distributions. Intermediates most frequent near limit of distributions of P. depressa and P. ulyssiponensis in Isle of Wight , perhaps because conditions not optimal (Fretter and Graham, 1994).
Key identification features of typical British specimens.
Patella depressa
[1&2 in combination, not singly, diagnostic of typical specimens but excludes intermediates.]
1. Pigmented pallial tentacles are opaque chalky-white for more than half of extended-length; may have translucent tip; distinctly whiter than buff mantle-skirt from which they arise 20Pd flic.kr/p/Ay6PEH . Even when mantle-skirt retracted, pallial tentacles often clearly visible contrasting with the darker mantle17Pd flic.kr/p/BaRWfU .
2. Sole of foot pitch-brown 16Pd flic.kr/p/Afb9yv to black 17Pd flic.kr/p/BaRWfU .
3. On shell-interior, whitish projecting points of ribs have short, unglazed, chalky, pure-white central line, but reduced or lacking where projecting points of ribs eroded 8Pd flic.kr/p/Ay6YL9 . [This feature recently recognised by S. Payne, and applies to all in large sample examined by IFS. Unsure yet if universal on P. depressa and exclusive of P. vulgata and P. ulyssiponensis.]
Before making records of this species further north than NW Anglesey it is advisable to familiarize oneself with specimens in areas where it is known to be frequent such as S. Devon, Channel Islands or Brittany.
Confirmation/correction can be sought by posting clear photo of pallial tentacles and foot on British Marine Molluscs Group at www.facebook.com/groups/british.marine.mollusca/
Similar species
Patella ulyssiponensis
1. Pallial tentacles have opaque pigment; white, off-white, cream or, on large specimens, yellowish or orange for about half of length; distal-half fades to translucent. Opaque basal parts often distinct from translucent mantle-skirt that they arise from so possible to confuse with P. depressa; important to use pallial tentacles in combination with foot-colour/shell-length for identification 41Pd flic.kr/p/ABFYRn .
2. Foot not pitch-brown/black; whitish when young 42Pd flic.kr/p/ALnSTW becoming yellowish 43Pd flic.kr/p/Ber2rm and often orange with age 44Pd flic.kr/p/ALnJ39 . Beware of juveniles under 12mm length that lack gonads above sole as dark viscera may show as blackish-shadow through thin pale translucent foot 42Pd flic.kr/p/ALnSTW . Green ovaries resting on interior surface of foot of mature female may show as faint greenish tinted zone along median line of foot where it is thinnest 43Pd flic.kr/p/Ber2rm .
Patella vulgata
Extremely variable species; foot colours and nearly all shell-features have overlaps with P. depressa and P. ulyssiponensis.
1. Pigment-less pallial tentacles are slender, translucent and same colour as mantle-skirt they arise from 45Pd flic.kr/p/AiLHRg .
Cautions:
Pallial tentacles may look white when arise from colourless mantle-skirt in some lighting, but no pigment and not chalky-white 46Pd flic.kr/p/AE15Wx .
Pigment-less translucency and fineness often make discernment difficult, especially when mantle skirt retracted from shell-rim and pallial tentacles viewed against shell 47Pd flic.kr/p/BeqQNY ; often virtually invisible when out of water as may be retracted into mantle 48Pd flic.kr/p/ABFF5R .
Foot colour varies, sometimes as dark as on P. depressa 47Pd flic.kr/p/BeqQNY .
03 Patella depressa. Length 26 mm. Lleyn, Wales. September 2015.
Exterior has sculpture of narrow radiating whitish ribs that project as points from the aperture-rim of unworn shells.
Grooves between ribs are brown where uneroded.
Key id. features BELOW.
SPECIES DESCRIPTION part A 1Pd flic.kr/p/BaSA3C
SPECIES DESCRIPTION part B 2Pd flic.kr/p/AfbFkR
OTHER SPECIES ALBUMS www.flickr.com/photos/56388191@N08/collections/
Identification of British patellid limpets.
With the exception of shells with height >50% of length (only P. vulgata grows that high, but many P. vulgata have low shells), shell-exteriors cannot be relied on, and shell-interiors can be confusing. Examination, in good light under magnification, of extended pallial tentacles on living animals is essential for consistent accurate discrimination of the three rock-dwelling Patella species. Best achieved with specimen adhering to underside of supported glass-sheet in black-based container of seawater.
Some morphologically intermediate forms can only be reliably identified by sequencing DNA or allozyme study 36Pd flic.kr/p/BdwtN8 and 37Pd flic.kr/p/AzydCD . Intermediates result from similar environmental factors affecting different species in similar ways and are not hybrids (Sanna et al., 2011 and Sá-Pinto et al., 2007). For the purpose of recording for distribution schemes it is advisable to disregard intermediates unless DNA or allozymes can be employed, especially beyond or on the limits of known distributions. Intermediates most frequent near limit of distributions of P. depressa and P. ulyssiponensis in Isle of Wight , perhaps because conditions not optimal (Fretter and Graham, 1994).
Key identification features of typical British specimens.
Patella depressa
[1&2 in combination, not singly, diagnostic of typical specimens but excludes intermediates.]
1. Pigmented pallial tentacles are opaque chalky-white for more than half of extended-length; may have translucent tip; distinctly whiter than buff mantle-skirt from which they arise 20Pd flic.kr/p/Ay6PEH . Even when mantle-skirt retracted, pallial tentacles often clearly visible contrasting with the darker mantle17Pd flic.kr/p/BaRWfU .
2. Sole of foot pitch-brown 16Pd flic.kr/p/Afb9yv to black 17Pd flic.kr/p/BaRWfU .
3. On shell-interior, whitish projecting points of ribs have short, unglazed, chalky, pure-white central line, but reduced or lacking where projecting points of ribs eroded 8Pd flic.kr/p/Ay6YL9 . [This feature recently recognised by S. Payne, and applies to all in large sample examined by IFS. Unsure yet if universal on P. depressa and exclusive of P. vulgata and P. ulyssiponensis.]
Before making records of this species further north than NW Anglesey it is advisable to familiarize oneself with specimens in areas where it is known to be frequent such as S. Devon, Channel Islands or Brittany.
Confirmation/correction can be sought by posting clear photo of pallial tentacles and foot on British Marine Molluscs Group at www.facebook.com/groups/british.marine.mollusca/
Similar species
Patella ulyssiponensis
1. Pallial tentacles have opaque pigment; white, off-white, cream or, on large specimens, yellowish or orange for about half of length; distal-half fades to translucent. Opaque basal parts often distinct from translucent mantle-skirt that they arise from so possible to confuse with P. depressa; important to use pallial tentacles in combination with foot-colour/shell-length for identification 41Pd flic.kr/p/ABFYRn .
2. Foot not pitch-brown/black; whitish when young 42Pd flic.kr/p/ALnSTW becoming yellowish 43Pd flic.kr/p/Ber2rm and often orange with age 44Pd flic.kr/p/ALnJ39 . Beware of juveniles under 12mm length that lack gonads above sole as dark viscera may show as blackish-shadow through thin pale translucent foot 42Pd flic.kr/p/ALnSTW . Green ovaries resting on interior surface of foot of mature female may show as faint greenish tinted zone along median line of foot where it is thinnest 43Pd flic.kr/p/Ber2rm .
Patella vulgata
Extremely variable species; foot colours and nearly all shell-features have overlaps with P. depressa and P. ulyssiponensis.
1. Pigment-less pallial tentacles are slender, translucent and same colour as mantle-skirt they arise from 45Pd flic.kr/p/AiLHRg .
Cautions:
Pallial tentacles may look white when arise from colourless mantle-skirt in some lighting, but no pigment and not chalky-white 46Pd flic.kr/p/AE15Wx .
Pigment-less translucency and fineness often make discernment difficult, especially when mantle skirt retracted from shell-rim and pallial tentacles viewed against shell 47Pd flic.kr/p/BeqQNY ; often virtually invisible when out of water as may be retracted into mantle 48Pd flic.kr/p/ABFF5R .
Foot colour varies, sometimes as dark as on P. depressa 47Pd flic.kr/p/BeqQNY .