''Pseudorhabdosynochus kritskyi'' is a diplectanid monogenean parasitic on the

gill A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...

s of the gag, ''Mycteroperca microlepis''. The species has been described by Dyer, Williams and Bunkley-Williams in 1995 and redescribed successively by Yang, Gibson and Zeng in 2005 and by

Kritsky ''Kritsky'' is a genus of digeneans in the family Aporocotylidae or blood flukes.WoRMS (2018). Kritsky Orelis-Ribeiro & Bullard, 2016. Accessed at: http://www.marinespecies.org/aphia.php?p=taxdetails&id=871002 on 2018-09-23 The name of the genus ...

, Bakenhaster and Adams in 2015. The name of the species honours the American parasitologist

Delane C. Kritsky Delane C. Kritsky is an American parasitologist who specialised on the Monogenea, a class of parasitic flatworms which are important ectoparasites of fishes. His research was mainly in the fields of taxonomy (biology), taxonomy, faunistics, and p ...

Description

''Pseudorhabdosynochus kritskyi'' is a small monogenean, less than 1 mm (700 μm) long. The species has the general characteristics of other species of ''

Pseudorhabdosynochus ''Pseudorhabdosynochus'' is a genus of monopisthocotylean monogeneans, included in the family Diplectanidae. The type-species of the genus is ''Pseudorhabdosynochus epinepheli'' ( Yamaguti, 1938). The genus includes more than 80 species, which a ...

'', with a flat body and a posterior

haptor The haptor is the attachment organ of the monogeneans, a group of parasitic Platyhelminthes. The haptor is sometimes called opisthaptor (from ''opistho-'': behind) to emphasize that it is located in the posterior part of the body, and to differe ...

, which is the organ by which the monogenean attaches itself to the gill of is host. The haptor bears two

squamodisc Squamodiscs are epidermal structures, which are typical of and found only in certain monogeneans of the family Diplectanidae. There are, typically, two squamodiscs, one ventral and one dorsal, located on the haptor of the monogenean. Squamodiscs ...

s, one ventral and one dorsal. The sclerotized male copulatory organ, or "quadriloculate organ", has the shape of a bean with four internal chambers, as in other species of ''

''. The

vagina In mammals, the vagina is the elastic, muscular part of the female genital tract. In humans, it extends from the vestibule to the cervix. The outer vaginal opening is normally partly covered by a thin layer of mucosal tissue called the hymen ...

includes a sclerotized part, which is a complex structure. The redescription by

, Bakenhaster & Adams in 2015 includes the following: Body dorsoventrally flattened. Tegument smooth, scales absent. Cephalic region broad, with two terminal and two bilateral poorly developed lobes, three bilateral pairs of head organs, pair of bilateral groups of cephalic-gland cells at level of pharynx. Four eyespots immediately anterior to pharynx, lacking lenses; members of posterior pair slightly larger, closer together than those of anterior pair; accessory chromatic granules small, irregular in outline, usually absent in cephalic region.

Pharynx The pharynx (plural: pharynges) is the part of the throat behind the mouth and nasal cavity, and above the oesophagus and trachea (the tubes going down to the stomach and the lungs). It is found in vertebrates and invertebrates, though its struc ...

ovate, muscular;

esophagus The esophagus (American English) or oesophagus (British English; both ), non-technically known also as the food pipe or gullet, is an organ in vertebrates through which food passes, aided by peristaltic contractions, from the pharynx to the ...

short to nonexistent; intestinal ceca blind, extending posteriorly to peduncle, diverging posterior to testis. Peduncle broad.

Haptor The haptor is the attachment organ of the monogeneans, a group of parasitic Platyhelminthes. The haptor is sometimes called opisthaptor (from ''opistho-'': behind) to emphasize that it is located in the posterior part of the body, and to differe ...

subtriangular, with dorsal and ventral anteromedial lobes containing respective squamodiscs and lateral lobes having hook pairs 2–4, 6, 7.

Squamodisc Squamodiscs are epidermal structures, which are typical of and found only in certain monogeneans of the family Diplectanidae. There are, typically, two squamodiscs, one ventral and one dorsal, located on the haptor of the monogenean. Squamodiscs ...

s subequal, with 14 or 15 U-shaped rows of rodlets; three or four innermost rows oval, closed. Ventral anchor with elongate superficial root, long deep root having lateral swelling, slightly curved shaft, and short recurved point extending just short of level of tip of superficial root. Dorsal anchor with subtriangular base, superficial root short to lacking, moderately long deep root, slightly arcing shaft, recurved point extending past level of tip of superficial root. Ventral bar with medial constriction, tapered ends, longitudinal medioventral groove. Paired dorsal bar with enlarged medial end. Hook with elongate slightly depressed thumb, delicate point, uniform shank; FH loop nearly shank length.

Testis A testicle or testis (plural testes) is the male reproductive gland or gonad in all bilaterians, including humans. It is homologous to the female ovary. The functions of the testes are to produce both sperm and androgens, primarily testostero ...

subspherical, usually with indentation of posterior margin suggesting two posterior lobes; proximal vas deferens dorsoventrally looping left intestinal cecum; seminal vesicle a simple dilation of distal portion of vas deferens, lying just posterior to male copulatory organ; vas deferens entering large subspherical ejaculatory bulb; ejaculatory duct entering portal to male copulatory organ; large vesicle (prostatic reservoir?) lying to right of male copulatory organ. Male copulatory organ reniform, quadriloculate, with short tapered cone, elongate distal tube, and variable apparently retractile filament (usually not observed); walls of two distal chambers thick, walls of chambers becoming thinner proximally. Germarium pyriform; germarial bulb dextral, lying diagonally at body midlength, with elongate dorsoventral loop around right intestinal cecum; ootype lying to left of body midline; Mehlis' gland not observed; uterus delicate, banana shaped when empty. Common genital pore ventral, dextral to MCO. Vaginal pore sinistroventral at level of seminal vesicle; vagina with distal vestibule; vaginal sclerite having sclerotized tube with distal recurved and funnel-shaped terminus opening into vestibule; single chamber usually spherical, with thick wall; proximal vaginal canal delicate, leading to seminal receptacle. Seminal receptacle near body midline. Bilateral vitelline ducts at level of origin of uterus;

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