Leucothoe incisa, copyright Hans Hillewaert.

Belongs within: Amphipoda.
Contains: Neopleustinae, Parapleustinae, Metopa, Stenothoe.

The Leucothoidea are a group of marine amphipods with the posterior pereopods uniform and telson lobes fused (Bousfield 1983).

Snail mimics and marine symbionts
Published 24 March 2009
The pleustid amphipod Incisocalliope aestuarius. Photo by Marco Faasse.

The Pleustidae are a family of marine amphipods, distributed around the world. However, despite their seemingly cosmopolitan distribution and abundance, it has been surprisingly difficult to find information about this family online. Pleustids are one of the many families in the largest of the amphipod suborders, the Gammaridea (gammarideans include the sandhoppers and other sandhopper-looking crustaceans that are what most people think of when they think of an amphipod). Gammaridean interrelationships are a great tangled mess, and in many places fall into a state that we scientists technically refer to as “buggered beyond belief”. Only slowly are researchers beginning to draw some sense out of things, and they’ll probably be at it for a long time yet. For those who wish to track them down (for the most part, I haven’t seen them), the main revisions of Pleustidae were published by Bousfield & Hendrycks (1994 and following) in Amphipacifica*. Stock (1986) (who very tentatively assigns three oddball stygobiotic species from Japan to the Pleustidae) gives the defining characters of the family as “the rudimentary condition of the accessory flagellum of the first antenna, the biramous third uropod (rami lanceolate), the elongate telson, the weak and more or less similar gnathopods 1 and 2, and… the bilobed condition of the labrum”. Bousfield & Hendrycks (1994, 1995) divided the family into a number of subfamilies.

*The short-lived journal Amphipacifica ended up with three volumes published between 1994 and 2001 (I haven’t found any indications that a planned fourth volume ever made an appearance). While I haven’t found a complete contents listing, it appears that most (if not all) articles had the chief editor, Edward Bousfield, as author or co-author, and the majority were on amphipod taxonomy. Perhaps unjustly, the journal is not remembered for its contributions to crustacean systematics as much as it is for Bousfield’s perhaps unwise foray into vertebrate taxonomy. Yes, this was the journal that saw the publication of the infamous Bousfield & LeBlond (1995), and the name Cadborosaurus wellsi—a paper so controversial that two of the journal’s editors promptly handed in their resignations in protest. For more details, see Darren Naish’s 2006 review.

Not having the resources on hand to give you a a decent overview of the family (sorry), I’m just going to give you a couple of the highlights that I have been able to locate—(as it says in the title) the snail mimics and the symbiotic taxa.

Pleustes panopla, a close relative of one of the snail-mimicing pleustids. Photo via here.

Snail mimicry has been recorded for two pleustids, Pleustes platypa and unidentified species of Stenopleustes (Field 1974). Pleustes platypa lives in kelp beds and mimics the marine gastropod Mitrella carinata. Mimetic Stenopleustes (it is not known how many species are involved) live in beds of Zostera (seagrass) and mimic various species of snails of the genus Lacuna. Different Stenopleustes individuals may have different colour patterns, each matching a different Lacuna species. The amphipod clings tightly to the seagrass, moving slowly to match the speed of a snail. Occassional rocking back and forth mimics the rocking movement of the snails. And while amphipods are perfectly adept swimmers, snail-mimicing Stenopleustes would only swim under extreme provocation, preferring to crawl to the other side of the seagrass blade instead when possible. Obviously, starting to swim would quickly give away that the animal was not a snail!

Other intriguing pleustids are the species that live as symbionts (generally commensals) of larger marine invertebrates. Commensipleustes commensalis is a symbiont of crabs, with enlarged spines on the underside of the forelimbs against which the dactylus (claw) can be folded back, allowing the amphipod to hang onto the host’s setae. Members of the genus Dactylopleustes, on the other hand, live on sea urchins, and their legs have notched claws that can be placed around the host’s spines. Another species, Mesopleustes abyssorum, clings to the legs of sea spiders. But most remarkable of all is the lifestyle that has been inferred for the species Myzotarsa anaxiphilius (Cadien & Martin 1999). Like Commensipleustes, Myzotarsa is a symbiont of crabs (in this case, king crabs of the genus Paralithodes), but while most crab-symbiotic amphipods live around the densely setose mouthparts, Myzotarsa lives underneath the crab’s recurved abdomen. Without setae to cling on to, the claws on the walking legs of Myzotarsa bear special suckers to allow the animal to latch on. What makes Myzotarsa really remarkable is that not just any crab will make a suitable host – instead, the amphipod shows a strong preference for crabs that are parasitised by rhizocephalans (out of 179 specimens of Myzotarsa referred to by Cadien & Martin, 1999, 167 came from parasitised hosts while only six came from a non-parasitised host [the remainder came from hosts whose parasite status was not recorded). It seems that the diet of the little Myzotarsa is the eggs being incubated underneath the abdomen. While healthy crabs will only be carrying eggs if they’re female and if it’s the right season, the chemically-castrated, feminised (if male) and mind-controlled infected crabs will be carrying externa filled with yummy rhizocephalan eggs all year round…

Systematics of Leucothoidea

Characters (from Bousfield 1983): Gnathopods 1 and 2 strongly dimorphic, amplexing in male; antenna with neither calceoli nor brush setae; labium with inner lobes partially developed; left mandible with lacinia 5-dentate; pereopods 5–7 homopodous, equal, with coxae posterolobate; pereopod 7 gill absent; uropods 1 and 2 with rami lanceolate, bare, uropod 3 rami non-foliaceous; telson lobes totally fused; brood plate broad, setose.

    |    |--Pagetina Barnard 1931B69
    |    |    `--*P. genarum Barnard 1932B69
    |    `--Heterocressa Nicholls 1938N38
    |         `--*H. monodi Nicholls 1938N38
    |    |--Paranamixis Schellenberg 1938B69
    |    |    `--*P. bocki Schellenberg 1938B69
    |    `--Anamixis Stebbing 1897B69
    |         |--*A. hanseni Stebbing 1897B69
    |         `--A. linsleyi Barnard 1955B69
    |    |--Cressina Stephensen 1931B69
    |    |    `--*C. monocuspis Stephensen 1931B69
    |    `--Cressa Boeck 1871 [incl. Danaia Bate 1857 (preoc.)]B69
    |         |--C. dubia (Bate 1857) [=Danaia dubia; incl. *C. schiodtei Boeck 1871]B69
    |         `--C. minutaB69
    |--Colomastix Grube 1861B69 [incl. Cratippus Bate 1862B69, Exunguia Norman 1869B69; ColomastigidaeB83]
    |    |--*C. pusilla Grube 1861B69
    |    |--C. brazieriN38
    |    |--C. fissilinguaN38
    |    |--C. magnirama Hurley 1954B69
    |    |--C. simplicicauda Nicholls 1938N38
    |    `--C. subcastellata Hurley 1954B69
    |    |--Laphystiopsis Sars 1895B69
    |    |    `--*L. planifrons Sars 1895B69
    |    |--Prolaphystius Barnard 1930B69
    |    |    `--*P. isopodops Barnard 1930B69
    |    `--Prolaphystiopsis Schellenberg 1931B69
    |         `--*P. platyceras Schellenberg 1931B69
    |    |--Prothaumatelson Schellenberg 1931B69
    |    |    |--*P. nasutum (Chevreux 1912) [=Thaumatelson nasutum]B69
    |    |    `--P. carinatum Shoemaker 1955B69
    |    |--Thaumatelson Walker 1906B69
    |    |    |--*T. herdmani Walker 1906B69
    |    |    |--T. cultricaudaN38
    |    |    `--T. walkeri Chilton 1912B69
    |    `--Pseudothaumatelson Schellenberg 1931 [incl. Parathaumatelson Gurjanova 1938]B69
    |         |--*P. patagonicum Schellenberg 1931B69
    |         |--P. cyproides Nicholls 1938N38
    |         `--P. herdmaniN38
    |    |--Leucothoella Schellenberg 1928B69
    |    |    `--*L. bannwarthi Schellenberg 1928B69
    |    |--Leucothoides Shoemaker 1933B69
    |    |    `--*L. pottsi Shoemaker 1933B69
    |    |--Paraleucothoe Stebbing 1899B69
    |    |    `--*P. novaehollandiae (Haswell 1880) [=Leucothoe novaehollandiae]B69
    |    `--Leucothoe Leach 1814 (see below for synonymy)B69
    |         |--*L. spinicarpa (Abildgaard 1789) [=Gammarus spinicarpus]B69
    |         |--L. incisa Robertson 1892BD95
    |         |--L. lilljeborgi Boeck 1861BD95
    |         |--L. occulta Krapp-Schickel 1975BD95
    |         |--L. pachycera Della Valle 1893BD95
    |         |--L. richiardii Lessona 1865BD95
    |         |--L. serraticarpa Della Valle 1893BD95
    |         `--L. venetiarum Giordani Soika 1950BD95
    |--Amphilochidae [Amphilochinae]B83
    |    |--Gitana Boeck 1871B69
    |    |    `--*G. sarsi Boeck 1871B69
    |    |--Gitanopsis Sars 1895B69
    |    |    `--*G. bispinosa (Boeck 1871) [=Amphilochus bispinosus]B69
    |    |--Gitanogeiton Stebbing 1910B69
    |    |    `--*G. sarsi Stebbing 1910B69
    |    |--Amphilochopsis Stephensen 1925B69
    |    |    `--*A. hamatus Stephensen 1925B69
    |    |--Amphilochella Schellenberg 1926B69
    |    |    `--*A. simplicarpus Schelleberg 1926B69
    |    |--Cyclotelson Potts 1915B69
    |    |    `--*C. purpureum Potts 1915B69
    |    |--Amphilochoides Sars 1895B69
    |    |    |--*A. odontonyx Boeck 1871 [incl. A. pusillus Sars 1895]B69
    |    |    |--A. intermedius Scott 1896N00
    |    |    `--A. serratipes (Norman 1869) [incl. A. longimanus (Chevreux 1888)]BD95
    |    `--Amphilochus Bate 1862 [incl. Callimerus Stebbing 1876]B69
    |         |--*A. manudens Bate 1862B69
    |         |--A. brunneus Della Valle 1893BD95
    |         |--A. melanops Walker 1895N00
    |         |--A. neapolitanus Della Valle 1893BD95
    |         |--A. sabrinae Stebbing 1878N00
    |         `--A. tenuimanusN00
    |    |  i. s.: Pleusymtes Barnard 1969B69
    |    |           `--*P. glaber (Boeck 1861) [=Amphithopsis glaber, Sympleustes glaber]B69
    |    |         Relictomaera Barnard & Karaman 1982S86
    |    |           |--R. relicta (Ueno 1971)S86
    |    |           `--R. tsushimana (Ueno 1971)S86
    |    |         Pleustes Bate 1858B69
    |    |           `--*P. panopla (Krøyer 1838) [=Amphithoe panopla]B69
    |    |         Austropleustes Barnard 1931B69
    |    |           `--*A. cuspidatus Barnard 1931B69
    |    |         Mesopleustes Stebbing 1899B69
    |    |           `--*M. abyssorum (Stebbing 1888) [=Pleustes abyssorum]B69
    |    |         Parepimeriella Schellenberg 1931B69
    |    |           `--*P. irregularis Schellenberg 1931B69
    |    |         Stenopleustes Sars 1895 [incl. Sympleustes Stebbing 1899]B69
    |    |           |--*S. malmgreni (Boeck 1871) [=Amphithopsis malmgreni]B69
    |    |           `--S. latipes (Sars 1858) [=Amphithoe latipes, *Sympleustes latipes]B69
    |    |--NeopleustinaeBH95
    |    |--ParapleustinaeBH95
    |    |--Pleusirus Barnard 1969 [Pleusirinae]BH95
    |    |    `--*P. secorrus Barnard 1969BH95
    |    |         |--P. s. secorrusBH95
    |    |         `--P. s. asiaticus Kudryaschov & Tzvetkova 1975BH95
    |    `--Dactylopleustes Karaman & Barnard 1979 (see below for synonymy)BH95
    |         |--*D. echinoicus (Tzvetkova 1975) [=Parapleustes echinoicus]BH95
    |         |--D. echinoides Bousfield & Hendrycks 1995 [=D. (*Neodactylopleustes) echinoides]BH95
    |         `--D. obsolescens Hirayama 1988 [=D. (*Apodactylopleustes) obsolescens]BH95
         |--Microstenothoe Pirlot 1933B69
         |    `--*M. ascidiae Pirlot 1933B69
         |--Prometopa Schellenberg 1926B69
         |    `--*P. tuberculata Schellenberg 1926B69
         |--Stenula Barnard 1962B69
         |    `--*S. latipes (Chevreux & Fage 1925) [=Stenothoides latipes]B69
         |--Metopelloides Gurjanova 1938B69
         |    `--*M. micropalpa (Shoemaker 1930) [=Metopella micropalpa]B69
         |--Parametopa Chevreux 1901B69
         |    `--*P. kervillei Chevreux 1901B69
         |--Prostenothoe Gurjanova 1938B69
         |    `--*P. sextonae Gurjanova 1938B69
         |--Probolisca Gurjanova 1938B69
         |    |--*P. ovata (Stebbing 1888) [=Metopa ovata]B69
         |    `--P. nasutigenes (Stebbing 1888) [=Metopella nasutigenes]B69
         |--Parametopella Gurjanova 1938B69
         |    |--*P. cypris (Holmes 1905) [=Stenothoe cypris]B69
         |    `--P. stelleri Gurjanova 1948B69
         |--Metopella Sars 1895B69
         |    |--*M. longimana (Boeck 1871) [=Metopa longimana]B69
         |    `--M. ovataN38
         |--Mesometopa Gurjanova 1938B69
         |    |--*M. esmarki (Boeck 1872) [=Metopa esmarki]B69
         |    `--M. neglectaB69
         |--Stenothoides Chevreux 1900 [incl. Mesostenothoides Gurjanova 1938]B69
         |    |--*S. perrieri Chevreux 1900B69
         |    |--S. bassarginensisKBC03
         |    `--‘Mesostenothoides’ nenoiKBC03
         |--Proboloides Della Valle 1893 [incl. Proboliella Walker 1906]B69
         |    |--*P. gregarius (Sars 1882) [=Metopa gregaria]B69
         |    |--P. antarcticusN38
         |    |--P. bruzeliiS00
         |    |--P. crenatipalmataN38
         |    `--P. dentimanus Nicholls 1938N38
         |--Metopoides Della Valle 1893B69
         |    |--*M. magellanica (Stebbing 1888) [=Metopa magellanica]B69
         |    |--M. aurorae Nicholls 1938N39
         |    |--M. compactaN38
         |    |--M. heterostylisN38
         |    `--M. sarsii [incl. M. walkeri]N38

Dactylopleustes Karaman & Barnard 1979 [incl. Apodactylopleustes Hirayama 1988, Neodactylopleustes Bousfield & Hendrycks 1995 (n. n.); Dactylopleustinae]BH95

Leucothoe Leach 1814 [incl. Cuvieria Leach 1814 (n. n.) nec Lesueur & Petit 1807 nec Rang 1827, Lycesta Savigny 1816]B69

*Type species of generic name indicated


[BD95] Bakalem, A., & J.-C. Dauvin. 1995. Inventaire des crustacés amphipodes (Gammaridea, Caprellidea, Hyperiidea) des costes d’Algérie: essai de synthèse. Mésogée 54: 49–62.

[B69] Barnard, J. L. 1969. The families and genera of marine gammaridean Amphipoda. United States National Museum Bulletin 271: i–vi, 1–535.

[B83] Bousfield, E. L. 1983. An updated phyletic classification and palaeohistory of the Amphipoda. In: Schram, F. R. (ed.) Crustacean Phylogeny pp. 257–277. A. A. Balkema.

[BH95] Bousfield, E. L., & E. A. Hendrycks. 1995. The amphipod family Pleustidae on the Pacific coast of North America: Part II. Subfamilies Parapleustinae, Dactylopleustinae, and Pleusirinae. Systematics and distributional ecology. Amphipacifica 2: 65–133.

Bousfield, E. L., & P. H. LeBlond. 1995. An account of Cadborosaurus willsi, new genus, new species, a large aquatic reptile from the Pacific coast of North America. Amphipacifica 1 (Supplement 1): 3–25.

Cadien, D. B., & J. W. Martin. 1999. Myzotarsa anaxiphilius, new genus, new species, an atylopsine amphipod (Gammaridea: Pleustidae) commensal with lithodid crabs in California. Journal of Crustacean Biology 19 (3): 593–611.

Field, L. H. 1974. A description and experimental analysis of Batesian mimicry between a marine gastropod and an amphipod. Pacific Science 28 (4): 439–447.

[KBC03] Kashin, I. A., E. V. Bagaveeva & S. F. Chaplygina. 2003. Fouling communities of hydrotechnical constructions in Nakhodka Bay (Sea of Japan). Russian Journal of Marine Biology 29: 267–283.

[N38] Nicholls, G. E. 1938. Australasian Antarctic Expedition 1911–1914. Under the Leadership of Sir Douglas Mawson, O.B.E., B.E., D.Sc., F. R. S. Scientific Reports. Series C—Zoology and Botany vol. 2 pt 4. Amphipoda Gammaridea. David Harold Paisley, Government Printer: Sydney (Australia).

[N39] Nicholls, G. E. 1939. The Prophliantidae: a proposed new family of Amphipoda, with description of a new genus and four new species. Records of the South Australian Museum 6 (3): 309–334.

[N00] Norman, A. M. 1900. British Amphipoda: families Pontoporeidae to Ampeliscidae. Annals and Magazine of Natural History, series 7, 5: 326–346.

[S00] Stebbing, T. R. R. 1900. Arctic Crustacea: Bruce collection. Annals and Magazine of Natural History, series 7, 5: 1–16.

[S86] Stock, J. H. 1986. Amphipoda: Pleustidae. In: Botosaneanu, L. (ed.) Stygofauna Mundi: A Faunistic, Distributional, and Ecological Synthesis of the World Fauna inhabiting Subterranean Waters (including the Marine Interstitial) pp. 560–561. E. J. Brill/Dr W. Backhuys: Leiden.

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