Episcopal mitre Mitra mitra, copyright J. C. Schou.

Belongs within: Mitridae.

Mitra, the mitres, is a genus of predatory gastropods with an elongate proboscis, specialised for feeding on burrowing worms. Both their scientific and vernacular names refer to their resemblence to the mitre (pointed hat) worn by ecclesiastical figures.

The bishop’s Mitra
Published 26 June 2009
Mitra cardinalis. Photo from Sydney Shell Club.

The marine gastropods of the genus Mitra get their genus name (as well as their common name of ‘mitre shells’) from the resemblance of many species, at certain angles, to the pointy hat of a bishop (and indeed, the species names Mitra episcopalis, M. pontificalis and M. papalis all appear to be floating around out there). They are fairly middling-sized shells—three or four centimetres long would seem to be a respectable Mitra size—and most of them are slender and pointed at one end (the technical term is ‘fusiform’, and the discription ‘cigar-shaped’ gets bandied about regularly). Members of the subgenus Strigatella, however, are shorter, more globular animals.

Mitra are members of the family Mitridae, which is in term a family of the Neogastropoda. There is a fair probability that if you go looking for gastropods on a trip to the beach that the first one you find will be a neogastropod. This is not so much because neogastropods are that much more abundant than other marine gastropods (although they are a fairly speciose bunch) as because neogastropods tend to be a lot more active than other gastropods, and are much more likely to be visibly on the move while other gastropods are sitting clamped to rocks. And the reason for the greater mobility of neogastropods is a matter of diet.

Mitra idae. Note the siphon protruding in front of the shell. Photo from Wikipedia.

The ancestral diet for gastropods was a reliable, if somewhat unexciting, scraped meal—algae rasped off rocks, or the fruits of scavenging. As a result, mobility is not at much of a premium for most gastropods—it doesn’t take much speed to chase down a patch of algae, and the only reason to move is to get to the next patch of algae. Neogastropods, however, tired of this diet and went for something a little more exciting—they became active predators. Mobile neogastropods at the beach are on the hunt for prey (or, alternatively, pre-deceased animals to scavenge off). One of the most distinctive features of neogastropods to the casual observer is their elongate siphon, which in live animals can usually be seen extended from the front of the shell (which has a distinct notch or anterior extension for it to extend through), waving back and forth as the animal moves, sniffing for any appetising scents. The radula (the tongue-like structure covered with teeth in the mouth of a gastropod) has become adapted to the predatory life-style, with the number of teeth reduced but each individual tooth much larger and sharper. The fusiform body-shape as seen in most Mitra also appears well-suited to mobility, and is shared by a significant proportion of neogastropods.

Mitra mitra everting its proboscis. Photo from here, where they’ve made the mistake of thinking this individual is swallowing a worm.

Members of the family Mitridae possess a particularly elongate proboscis, often longer than the rest of the animal. Running along the inside of the proboscis is the radula and a muscular rod called the epiproboscis, which can be even further extended. Mitrids are specialist feeders on sipunculan worms, which live buried in sediment or burrowed into corals (Taylor 1989), and the epiproboscis is used to capture their prey. Suggestions that it is used to inject digestive enzymes into the prey for external digestion are incorrect, as the prey is usually swallowed directly without allowing time for digestion (Taylor 1989) The method used by Mitra idae to capture a sipunculan was described by West (1990), and as the morphology of the epiproboscis is fairly constant within the Mitridae other species probably use the same or a very similar method. After locating a sipunculan with its siphon, the gastropod would extend its proboscis until it contacted the worm, then the epiproboscis to grab onto the worm. The first move of the Mitra would then be to try and suck the worm directly out of its burrow. If this failed (which I suspect would be the norm), it would then use its radula to rasp a hole through the worm’s skin before inserting the epiproboscis through the hole. The epiproboscis would entwine itself around the worm’s viscera and grab directly onto its intestines. The viscera would then be hauled out through the hole in the sipunculan’s skin and slurped down the waiting proboscis. Once the Mitra had pulled as much of the worm’s guts out as it could, it would close its proboscis over the remaining husk and finish drawing the worm out from its hole. Insertion and retraction of the epiproboscis took a little under ten seconds. The whole process, from initial insertion to final withdrawal, could take up to twenty minutes.

Systematics of Mitra

Characters (from Oldroyd 1927): Shell fusiform, thick; spire elevated, acute at apex; aperture small, narrow, notched in front; columella obliquely plicate; outer lip thickened, smooth internally.

<==Mitra Lamarck 1798BR05 [=Mitraria Rafinesque 1815BR17; incl. AidoneH08; Mitrariidae, Mitrariinae, MitrinaeBR17]
    |--M. corniculaFP15
    `--+--*M. mitra (Linnaeus 1758)BR17, FP15, BR17 [=Voluta mitraBR17]
       `--M. papalis Linnaeus 1758FP15, WG71
Mitra incertae sedis:
  M. acuminata Swainson 1824BW09
  M. amabilis Reeve 1845H09
  M. amanda Reeve 1845H09
  M. ambigua Swainson 1829BW09
  M. antonelli Dohrn 1860H09
  M. apicalisH86
  M. arenosa Lamarck 1811H09
  M. armillata Reeve 1845H09
  M. asperulata Adams 1852H08
  M. aurantia (Gmelin 1791) [=Voluta aurantia]H09
  M. auroraBW09
    |--M. a. auroraBW09
    `--M. a. floridula Sowerby 1874BW09
  M. australisM54
  M. avenacea Reeve 1845H09
  M. badiaP95
  M. caffra (Linnaeus 1758) [=Voluta caffra]H09
  M. caliginosaO27
  M. cancellata Bolten 1798F27b
  M. ‘cancellata’ Swainson 1821 non Bolten 1798F27b
  M. capricornea Hedley 1907H09
  M. carbonaria Swainson 1822H08
  M. cardinalis Gmelin 1791WG71
  M. catalinae Dall 1919 [=Strigatella (Atrimitra) catalinae]O27
  M. chrysalis Reeve 1844BW09
  M. chrysostoma Broderip 1836BW09
  M. circula Kiener 1839H09
  M. clathrata Defrance 1824F27b
  M. ‘clathrata’ Reeve 1844 non Defrance 1824F27b
  M. ‘clathrata’ Reuss 1845 nec Defrance 1824 nec Reeve 1844F27b
  M. coccineaF66
  M. coffea Schubert & Wagner 1829 [incl. M. thaanumiana Pilsbry 1921]BC01
  M. crassa Swainson 1822H09
  M. crenifera Lamarck 1811H09
  M. cruentata (Gmelin 1791) [=Voluta cruentata]H09
  M. cucumerina Lamarck 1811BW09
  M. curvilirata Sowerby 1874H09
  M. decurtata Reeve 1844BW09
  M. delicata Adams 1853H09
  M. deshayesii Reeve 1844H09
  M. dichroa Adams 1853H09
  M. diegensis Dall 1919 [=Strigatella (Atrimitra) diegensis]O27
  M. digitalisSP72
  M. duplilirata Reeve 1845H09
  M. ebenus [incl. M. ebenus var. uniplicatus Wood 1872]F27b
  M. elatior Finlay 1924F27a
  M. enysiH86
  M. episcopalis [=Voluta (Mitra) episcopalis]G20
  M. eremitarum Roiling 1798BW09
  M. ericea Pease 1860K65
  M. eusulcata Finlay 1924F27a
  M. exilis Reeve 1845F27b
  M. ferruginea Lamarck 1811BW09
  M. filaris (Linne 1771) [=Voluta filaris]H09
  M. formosa Adams 1853H09
  M. fragra Quoy & Gaimard 1833H09 [incl. M. peregraB79]
  M. fultoniO27
  M. funiculataC64
  M. fuscaPP64
  M. gilbertsoni (Cate 1968) [=Pterygia gilbertsoni]BC01
  M. granatina Lamarck 1811H09
  M. hanetiC64
  M. hastata Sowerby 1874H09
  M. hebes Reeve 1845H09
  M. hectori Hutton 1904F27a
  M. hedleyi Murdoch 1905F27a
  M. (Atrimitra) idae Melvill 1893B56, O27 [incl. M. semiusta Berry 1957BC01]
    |--M. i. idaeO27
    `--M. i. montereyensis Berry 1920O27
  M. imperialis Roiling 1798BW09
  M. insignis Adams 1853 (n. d.) [=M. (*Aidone) insignis]H08
  M. interlirata Reeve 1844H09
  M. jukesii Adams 1853H09
  M. legrandi Tenison Woods 1876TW76
  M. lensO27
  M. leucodesma Reeve 1844H09
  M. ligata Adams 1853F27b
  M. limbiferaB79
  M. limosa Martyn 1786H09
  M. litterata Lamarck 1811BW09
  M. longispira Sowerby 1874H09
  M. lowei Dall 1903O27
  M. lubens Reeve 1845H09
  M. lucida Reeve 1845H09
  M. luctuosa (Adams 1853)BW09
  M. lugubris Swainson 1822WG71
  M. maoria Finlay 1927F27a
  M. maura [incl. M. chilensis, M. orientalis]C64
  M. michaui Crosse & Fischer 1864H09
  M. modesta Reeve 1845H09
  M. multisulcata Harris 1897F27b
  M. nigricans Pease 1865 [=Strigatella nigricans]K65
  M. nodulosa Gmelin 1791 [incl. M. nodulosa pallida Usticke 1959 non M. pallida Pease 1860]BC01
  M. nucleola [incl. M. crenata]C64
  M. obeliscus Reeve 1844H09
  M. othone Tenison-Woods 1879F71
  M. pallida Pease 1860K65
  M. patriarchalis (Gmelin 1791) [=Voluta patriarchalis]H09
  M. paupercula (Linnaeus 1758)BW09
  M. peasei Dohrn 1860H09
  M. porphyritica Reeve 1844H09
  M. procissa Reeve 1844H09
  M. pudica Pease 1860 [incl. M. nuxavellana, M. subrostrata]K65
  M. pura Adams 1853H09
  M. ralphi Cossmann 1900 (see below for synonymy)F27b
  M. reticulata Adams 1853H09
  M. retusa Lamarck 1811BW09
  M. rhodiaM54
  M. rotundilirata Reeve 1844H09
  M. rubritincta Reeve 1844BW09
  M. rufescens Adams 1853H09
  M. rugosa (Gmelin 1791) [=Voluta rugosa]H09
  M. ruppeliF27b
  M. saltata Pease 1865K65
  M. sanguisuga (Linnaeus 1758) [=Voluta sanguisuga]H09
  M. scabricula (Linne 1767) [=Voluta scabricula]H09
  M. ‘scalariformis’ Tenison Woods 1876 non Borson 1825TW76
  M. scita Tenison Woods 1876TW76
  M. sculptilis Reeve 1845H09
  M. scutulata (Gmelin 1791) [=Voluta scutulata]H09
  M. semilaevis Edwards 1849F27b
  M. sigillata Azuma 1965Q89
  M. solida Reeve 1844H09
  M. stictica (Link 1807)BW09
  M. subdivisa (Bolten 1798) [=Vexillum subdivisum]H09
  M. subruppeli Finlay 1927 [=M. multisulcata Sowerby 1914 non Harris 1897]F27b
  M. suturata Reeve 1845H09
  M. tabanula Lamarck 1811H09
  M. taeniata Lamarck 1811H09
  M. tasmanica Tenison Woods 1876TW76
  M. tatei Angas 1879F27b
  M. teresiae Tenison Woods 1876TW76
  M. ticaonica Reeve 1844WG71
  M. variabilis Reeve 1844WG71
  M. variegata (Gmelin 1791) [=Voluta variegata]H09
  M. vermiculata Martyn 1786H09
  M. vexillum Reeve 1844BW09
  M. vulpecula (Linnaeus 1758) [=Voluta vulpecula]H09
  M. zephyrina Sowerby 1874H09

Mitra ralphi Cossmann 1900 [=M. semilaevis Tate 1889 non Edwards 1849, M. tatei Cossmann 1899 non Angas 1879, Costellaria tatei, Turricula tatei]F27b

*Type species of generic name indicated


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