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Pseudoceros

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Pseudoceros
Pseudoceros liparus
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Platyhelminthes
Order: Polycladida
Family: Pseudocerotidae
Genus: Pseudoceros
Lang, 1884[1]
Pseudoceros ferrugineus
Pseudoceros susanae
Pseudoceros dimidiatus
Pseudoceros dimidiatus
Pseudoceros sapphirinus

Pseudoceros is a genus of the flatworms Platyhelminthes.

Description

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Easily recognized features within the genus include a ruffled pharynx,[2] branched intestines,[2] and tentacles on the leading edge.[3][2]  The tentacles may act as chemoreceptors and may also have primitive eyes, simple light-sensitive cells, on them.[3] The Polyclad worms are acoelomates and bilaterally symmetrical.[4]

Color is the main identifier within the family Pseudocerotidae to separate it into genera, as it can be difficult to distinguish internal reproductive anatomy between genera.[5] Because of the similarities in body plan and structure, it is assumed that chemical cues are how these organisms can recognize their own species and differentiate between others.[5]

The intense coloring and patterning on these flatworms could be used to camouflage with their surroundings,[6] confuse and elude predators,[6] to communicate with other members of the species,[6] or as aposematism[6][7] to warn predators of their deadly toxins. The cells and the pigments they contain that are responsible for this coloring have not been well-studied, but one common theory is that they may be ommochrome pigments, although no discoveries have been made to prove this.[6]

Distribution

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Pseudoceros are generally found in tropical and subtropical waters. They are populous in the Indo-Pacific region and have been found as far north as Puget Sound,[8] where Pseudoceros canadensis has been identified, but mostly tend to stay in warmer waters.

Reproduction

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Pseudoceros are simultaneous hermaphrodites[9] and reproduce sexually via random hypodermic insemination through the body tissue.[10] These organisms participate in penis fencing,[9] which is a behavior where the flatworms use their extended penises to stab and inseminate the other, while avoiding becoming inseminated themselves. After successful fertilization, these flatworms are known to lay egg masses on the benthos.[9] Numbers of eggs, egg size, and developmental time vary between species.

Pseudoceros indicus will display parental care in the form of brooding activity.[11] Pseudoceros will hatch into Muller's larvae[11] and undergo indirect development and metamorphosis before becoming an adult organism.[11]

History & taxonomy

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Historically, studying flatworms has been a time and labor-intensive job, generally done through live drawings of specimens, preservation of hard parts (which led to the loss of important information pertaining to the soft parts), and very detailed anatomical studies based on serial sections.[12] More recent technological advances have allowed for scientists to combine photomicrography with molecular analyses to more easily study these organisms.[12]  

There is currently no consensus on what the best method of identification for Pseudoceros is. The two main theories are that species can be identified solely based on their color patterns and that species should be identified based on their reproductive organs instead of coloration.[13] Because of this, identification methods vary within the biological community.

In concordance with the theory that species should be identified based on color patterns, a new method for preserving Pseudoceros samples was developed in 1995 by Cannon and Newman. This method utilizes FCA-PGPP, or Formaldehyde Calcium Acetate-Propylene Glycol, Propylene Phenoxetol,[14] as the fixative. The worms are placed onto filter paper which is placed on top of a frozen layer of the fixative, and this preserves color accurately.[14]

As of 2000, there are 13 genera in the family Pseudocerotidae that comprise an estimated at least 500 species, of which the genus Pseudoceros made up about 75% until the genus Pseudobiceros was separated.[15]

Species

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The following species are recognised in the genus Pseudoceros:[16]

References

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  1. ^ Lang, A (1884). "Die Polycladen des Golfes von Neapel und der angrenzenden Meeresabschnitte. Eine Monographie". Fauna und Flora des Golfes von Neapel, Leipzieg. 11. Retrieved 11 April 2020.
  2. ^ a b c Hyman, Libbie (April 1954). "The polyclad genus Pseudoceros, with special reference to the Indo-Pacific region". Pacific Science. 8: 219–225.
  3. ^ a b Newman, Leslie; Cannon, Lester (2003). Marine Flatworms: The World of Polyclads. CISR Publishing. p. 14.
  4. ^ Rawlinson, Kate; Litvaitis, Marian (2008). "Cotylea (Polycladida): a cladistic analysis of morphology". Invertebrate Biology. 127 (2): 121–138. doi:10.1111/j.1744-7410.2007.00119.x.
  5. ^ a b Newman, Leslie; Cannon, Lester. "Pseudoceros (Platyhelminthes: Polycladida) from the Indo-Pacific with twelve new species from Australia and Papua New Guinea" (PDF). The Raffles Bulletin of Zoology. 46: 293–323.
  6. ^ a b c d e Lindsay-Mosher, Nicole; Pearson, Brett (2019). "The true colours of the flatworm: Mechanisms of pigment biosynthesis and pigment cell lineage development in planarians". Seminars in Cell & Developmental Biology. 87: 37–44. doi:10.1016/j.semcdb.2018.05.010. PMID 29758350. S2CID 44144052.
  7. ^ Ang, Hing; Newman, Leslie (1998). "Warning colouration in pseudocerotid flatworms (Platyhelminthes, Polycladida). A preliminary study". Hydrobiologia. 383: 29–33. doi:10.1023/A:1003449226586. S2CID 37282925.
  8. ^ Hyman, Libbie H. (April 1954). "The Polyclad Genus Pseudoceros, with Special Reference to the Indo-Pacific Region". Pacific Science. 8 (2): 219–225. hdl:10125/9167.
  9. ^ a b c Jia Wen Tong, Samantha; Ong, Rene (2020). "Mating behavior, spawning, parental care, and embryonic development of some marine pseudocerotid flatworms (Platyhelminthes: Rhabditophora: Polycladida) in Singapore". Invertebrate Biology. 139 (2). doi:10.1111/ivb.12293. S2CID 225782903.
  10. ^ Litvaitis, M.; Newman, Libbie (2001). "A molecular framework for the phylogeny of the Pseudocerotidae (Platyhelminthes, Polycladida)". Hydrobiologia. 444: 177–182. doi:10.1023/A:1017503124908. S2CID 21562766.
  11. ^ a b c Chim, C.; Ong, Rene; Gan, B. "Penis fencing, spawning, parental care and embryonic development in the cotylean flatworm Pseudoceros indicus (Platyhelminthes: Polycladida: Pseudocerotidae) from Singapore". Raffles Bulletin of Zoology. 31: 60–67 – via ResearchGate.
  12. ^ a b Janssen, Toon; Vizoso, Dita; Schulte, Gregor; Littlewood, Timothy; Waeschenbach, Andrea; Schärer, Lukas (November 2015). "Corrigendum to 'The first multi-gene phylogeny of the Macrostomorpha sheds light on the evolution of sexual and asexual reproduction in basal Platyhelminthes'". Molecular Phylogenetics and Evolution. 92: 82–107. doi:10.1016/j.ympev.2015.06.004. PMID 26093054.
  13. ^ Litvaitis, M.; Newman, Libbie (2001). "A molecular framework for the phylogeny of the Pseudocerotidae (Platyhelminthes, Polycladida)". Hydrobiologia. 444: 177–182. doi:10.1023/A:1017503124908. S2CID 21562766.
  14. ^ a b Newman, L. J.; Cannon, L. R. G. (1995). "The importance of the fixation of colour, pattern and form in tropical Pseudocerotidae (Platyhelminthes, Polycladida)". Biology of Turbellaria and some Related Flatworms. pp. 141–143. doi:10.1007/978-94-011-0045-8_23. ISBN 978-94-010-4025-9.
  15. ^ Litvaitis, M.; Newman, Libbie (2001). "A molecular framework for the phylogeny of the Pseudocerotidae (Platyhelminthes, Polycladida)". Hydrobiologia. 444: 177–182. doi:10.1023/A:1017503124908. S2CID 21562766.
  16. ^ "WoRMS - World Register of Marine Species - Pseudoceros Lang, 1884". www.marinespecies.org. Retrieved 2021-10-17.
  17. ^ a b Collingwood, Cuthbert (1876). "VI. On thirty-one Species of Marine Planarians, collected partly by the late Dr. Kelaart, F.L.S., at Trincomalee, and partly by Dr. Collingwood, F.L.S., in the Eastern Seas". Transactions of the Linnean Society of London. 2nd Series. Zoology. 1 (3): 83–98. doi:10.1111/j.1096-3642.1876.tb00435.x.
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