Pseudoceros is a genus of the flatworms Platyhelminthes.
Description Easily recognized features within the genus include a ruffled pharynx, branched intestines, and tentacles on the leading edge. The tentacles may act as chemoreceptors and may also have primitive eyes, simple light-sensitive cells, on them. The Polyclad worms are acoelomates and bilaterally symmetrical.
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. 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.
The intense coloring and patterning on these flatworms could be used to camouflage with their surroundings, confuse and elude predators, to communicate with other members of the species, or as aposematism 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.
Distribution 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, where Pseudoceros canadensis has been identified, but mostly tend to stay in warmer waters.
Reproduction Pseudoceros are simultaneous hermaphrodites and reproduce sexually via random hypodermic insemination through the body tissue. These organisms participate in penis fencing, 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. Numbers of eggs, egg size, and developmental time vary between species.
Pseudoceros indicus will display parental care in the form of brooding activity. Pseudoceros will hatch into Muller's larvae and undergo indirect development and metamorphosis before becoming an adult organism.
History & taxonomy 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. More recent technological advances have allowed for scientists to combine photomicrography with molecular analyses to more easily study these organisms.
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. 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, 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.
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.
Species The following species are recognised in the genus Pseudoceros:
Pseudoceros affinis (Collingwood, 1876) Pseudoceros agattiensis Dixit, 2019 Pseudoceros albicornus (Stimpson, 1857) Pseudoceros albomarginatus Hyman, 1959 Pseudoceros asamusiensis Kato, 1939 Pseudoceros astrorum Bulnes & Torres, 2014 Pseudoceros ater Hyman, 1959 Pseudoceros atraviridis (Collingwood, 1876) Pseudoceros atropurpureus Kato, 1934 Pseudoceros auranticrinis Dixit, Raghunathan & Chandra, 2017 Pseudoceros bicolor Verrill, 1902 Pseudoceros bicuti Ramos-Sanchez, Bahia & Rolando Bastida-Zavala, 2020 Pseudoceros bifasciatus Prudhoe, 1989 Pseudoceros bimarginatus Meixner, 1907 Pseudoceros bipurpureus Dixit, 2021 Pseudoceros bolool Newman & Cannon, 1994 Pseudoceros buskii (Collingwood, 1876) Pseudoceros caeruleocinctus Hyman, 1959 Pseudoceros caeruleopunctatus Palombi, 1928 Pseudoceros canadensis Hyman, 1953 Pseudoceros cardinalis Haswell, 1907 Pseudoceros cardiosorus (Schmarda, 1859) Pseudoceros cerebralis (Kelaart, 1858) Pseudoceros chloreus Marcus, 1949 Pseudoceros clavicornis (Schmarda, 1859) Pseudoceros coccineus (Stimpson, 1857) Pseudoceros colemani Prudhoe, 1977 Pseudoceros collingwoodi Laidlaw, 1903 Pseudoceros concinnus (Collingwood, 1876) Pseudoceros confusus Newman & Cannon, 1995 Pseudoceros contrarius Newman & Cannon, 1995 Pseudoceros corallophilus Hyman, 1954 Pseudoceros cruentus Newman & Cannon, 1998 Pseudoceros devisii Woodworth, 1898 Pseudoceros dimidiatus von Graff, 1893 Pseudoceros dulcis Kelaart, 1858 Pseudoceros duplicinctus Prudhoe, 1989 Pseudoceros exoptatus Kato, 1938 Pseudoceros felis Newman & Cannon, 1994 Pseudoceros ferrugineus (Hyman, 1959) Pseudoceros flavomaculatus Graff, 1893 Pseudoceros flavomarginatus Laidlaw, 1902 Pseudoceros fulminatus (Stimpson, 1855) Pseudoceros fuscogriseus Hyman, 1959 Pseudoceros fuscopunctatus Prudhoe, 1977 Pseudoceros fuscus (Kelaart, 1858) Pseudoceros galatheensis Dixit, Raghunathan & Chandra, 2017 Pseudoceros galaxea Dixit, 2021 Pseudoceros gamblei Laidlaw, 1902 Pseudoceros glaucus Prudhoe, 1989 Pseudoceros goslineri Newman & Cannon, 1994 Pseudoceros gravieri Meixner, 1907 Pseudoceros griseus Hyman, 1959 Pseudoceros guttatomarginatus (Stimpson, 1855) Pseudoceros habroptilus Hyman, 1959 Pseudoceros haddoni (Laidlaw, 1903) Pseudoceros hancockanus (Collingwood, 1876) Pseudoceros harrisi Bolanos, Quiroga, & Litvaitis, 2007 Pseudoceros heronensis Newman & Cannon, 1994 Pseudoceros imitatus Newman & Cannon, 1994 Pseudoceros imperatus Newman & Cannon, 1998 Pseudoceros indicus Newman & Schupp, 2002 Pseudoceros intermittus Newman & Cannon, 1995 Pseudoceros interruptus (Stimpson, 1855) Pseudoceros irretitus Newman & Cannon, 1998 Pseudoceros japonicus (Stimpson, 1857) Pseudoceros jebborum Newman & Cannon, 1994 Pseudoceros josei Newman & Cannon, 1998 Pseudoceros juani Bahia et al., 2014 Pseudoceros kelaarti (Collingwood, 1876) Pseudoceros kentii Graff, 1893 Pseudoceros kylie Newman & Cannon, 1998 Pseudoceros lacteus (Collingwood, 1876) Pseudoceros lactolimbus Newman & Cannon, 1998 Pseudoceros laingensis Newman & Cannon, 1998 Pseudoceros langamaakensis Faubel, 1983 Pseudoceros laticlavus Newman & Cannon, 1994 Pseudoceros latissimus type A (Schmarda, 1859) Pseudoceros leptostictus Bock, 1913 Pseudoceros limbatus Leuckart, 1828 Pseudoceros lindae Newman & Cannon, 1994 Pseudoceros liparus Marcus, 1950 Pseudoceros litoralis Bock, 1913 Pseudoceros lividus Prudhoe, 1982 Pseudoceros luteus (Plehn, 1898) Pseudoceros macroceraeus Schmarda, 1859 Pseudoceros maculatus (Pease, 1860) Pseudoceros maximum Lang, 1884 Pseudoceros maximus-type A Lang, 1884 Pseudoceros meenae Dixit, Sivaperuman & Raghunathan, 2018 Pseudoceros memoralis Kato, 1938 Pseudoceros mexicanus Hyman, 1953 Pseudoceros microceraeus (Schmarda, 1859) Pseudoceros micropapillosus Kato, 1934 Pseudoceros monostichos Newman & Cannon, 1994 Pseudoceros montereyensis Hyman, 1953 Pseudoceros mossambicus Prudhoe, 1989 Pseudoceros mulleri (Delle Chiaje, 1829) Pseudoceros niger (Stimpson, 1857) Pseudoceros nigrocinctus (Schmarda, 1859) Pseudoceros nigropunctatus Dixit, Raghunathan & Chandra, 2017 Pseudoceros nipponicus Kato, 1944 Pseudoceros ouini Newman & Cannon, 1994 Pseudoceros paradoxus Bock, 1927 Pseudoceros paralaticlavus Newman & Cannon, 1994 Pseudoceros periaurantius Newman & Cannon, 1994 Pseudoceros periphaeus Bock, 1913 Pseudoceros peripurpureus Newman & Cannon, 1994 Pseudoceros perviolaceus (Schmarda, 1859) Pseudoceros pius Kato, 1938 Pseudoceros pleurostictus Bock, 1913 Pseudoceros punctatus Laidlaw, 1902 Pseudoceros purpureus (Kelaart, 1858) Pseudoceros rawlinsonae Bolanos, Quiroga, & Litvaitis, 2007 Pseudoceros regalus Laidlaw, 1903 Pseudoceros reticulatus Yeri & Kaburaki, 1918 Pseudoceros rubellus Laidlaw, 1903 Pseudoceros rubronanus Newman & Cannon, 1998 Pseudoceros rubrotentaculatus Kaburaki, 1923 Pseudoceros sagamianus Kato, 1937 Pseudoceros sapphirinus Newman & Cannon, 1994 Pseudoceros scintillatus Newman & Cannon, 1994 Pseudoceros scriptus Newman & Cannon, 1998 Pseudoceros stellans Dixit, 2019 Pseudoceros stimpsoni Newman & Cannon, 1998 Pseudoceros striatus Kelaart, 1858 Pseudoceros susanae Newman & Anderson, 1997 Pseudoceros texanus Hyman, 1955 Pseudoceros tigrinus Laidlaw, 1902 Pseudoceros tomiokaensis Kato, 1938 Pseudoceros tristriatus Hyman, 1959 Pseudoceros velutinus (Blanchard, 1847) Pseudoceros verecundus Newman & Cannon, 1994 Pseudoceros vinosus Meixner, 1907 Pseudoceros vishnui Dixit, Raghunathan & Chandra, 2017 Pseudoceros yessoensis Kato, 1937 Pseudoceros zebra (Leuckart, 1828) Pseudoceros zeylanicus (Kelaart, 1858)
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