Psammocephalus
Psammocephalus Wicklow, 1982 (ref. ID; 7679 original paper)
Order Hypotrichida Stein, 1859: Suborder Discocephalina Wicklow, 1982: Family Discocephalidae Jankowski, 1979 (ref. ID; 7679)
[ref. ID; 7679]
Diagnosis; Elongate cell shape; pellicle either rigid (e.g. P. borrori) or supple (e.g. P. faurei); complete rows of midfrontal and right and left marginal cirri; peristomial lobe with peristomial cirrus prominent; AZM extends posteriorly along right lateral border of cell. (ref. ID; 7679)
Etymology; The name Psammocephalus is derived from the Greek roots Psamo, meaning sand, and cephala, meaning head. (ref. ID; 7679)
Type species; Psammocephalus borrori (ref. ID; 7679)
- Psammocephalus borrori Wicklow, 1982 (ref. ID; 191, 7679 original paper)
- Psammocephalus dragescoi Wicklow, 1982 (ref. ID; 7679 original paper)
- Psammocephalus faurei (Dragesco, 1963) Wicklow, 1982 (ref. ID; 7679 redescribed paper) reported author and year? (ref. ID; 191)
- Psammocephalus lithophora (Faure-Fremiet, 1954) Wicklow, 1982 (ref. ID; 7679 redescribed paper)
Psammocephalus borrori Wicklow, 1982 (ref. ID; 191, 7679 original paper)
Descriptions
This species is highly thigmotactic, but can also spiral rapidly backward when disturbed. It feeds on diatoms and algae, gliding over sand grains in a forward, then erratic back and forth motion. The ciliate is approximately 100 um in length, 35 um in width. The posterior portion of the cell is elongate and rigid; the anterior portion is strongly cephalized and can be flexed. Like D. ehrenbergi the cephalized region forms a ventral peristomial lobe and houses the membranelles (approximately 8 collar and 20-24 lapel membranelles) and oral membranes including the paroral cirrus and a peristomial cirrus at the anterior end of the paroral membrane. In the cell's posterior region there is a midventral groove that leads posteriorly to a ventral concavity from which 5-9 transverse cirri and 2 accessory transverse cirri emerge. The remaining frontal cirri arise from the midventral groove, beside the lapel membranelles (malar cirri), and on the cephalized region. Two migratory cirri are located just posterior to the distal collar membranelles. As in D. ehrenbergi, left marginal cirri consist of 2 distinct groups: an anterior row of 8-24 cirri, each set ventrally at a 60 degrees angle to the longitudinal axis of the cell, and posterolateral group of 8-13 cirri set within a cortical groove. In addition to left marginal cirri, P. borrori (unlike D. ehrenbergi) possesses right marginal cirri - a uniform row of 11-13 cirri. On the dorsal surface there are 6 bristle rows. Five of these rows, numbers 1, 2, 4, 5 and 6 (numbering from left to right), possess extremely long cilia (7-8 um in length); one row, number 3, possesses short cilia (approximately 2 um in length). Three sets of caudal cirri lie along the right posterior edge of the dorsal surface. The first (posteriormost) is a set of 4 cirri, the second set of 2 cirri, and the third is a set of 2 cirri. Microtubular bundles originate at the anterior edge of each transverse cirrus, extend anteriorly, then unite to form a microtubular trunk - the major component of the posterior cytoskeleton. The transverse cirral kinetosomes are arranged in oblique rows; as in D. ehrenbergi, each internal kinetosome bears a single postciliary microtubule that runs posteriorly between kinetosomal arrays. Large bundles of nematodesmal microtubules descend from the cirral base, then extend posteriorly to join with the U-shaped, post-transverse element of the cytosleleton. The cytoskeleton of the cephalized region is less complex than that of D. ehrenbergi and microtubular protrusions are absent. The cell is multimacronucleate with up to 120 macronuclei. (ref. ID; 7679)
Morphogenesis: I observed only a incomplete series of re-organization morphogenesis in P. borrori; this process, however, enabled me to identify the general developmental pattern (similar to that of D. ehrenbergi) and to trace the source of various cirral organelles. Frontal ciliature develops from 9 streaks. These streaks divide into 4 transverse ranks of procirri. The first (posteriormost) forms the transverse cirri, the second forms 2 accessory transverse and from the third and fourth ranks develop the remaining frontal cirri, including midfrontal, malar, and from the rightmost procirri, 2 migratory cirri. A paroral cirrus appears to develop from the dedifferentiated parental paroral apparatus. Right and left marginal cirri arise by within row development. Two groups of cirri differentiate from the left marginal primordium: the anterior cirral row and posterorlateral group. Caudal cirri from the rightmsot dorsal kineties. (ref. ID; 7679)
Etymology
The species borrori is named in honor of Dr. Arthur C. Borror. (ref. ID; 7679)
Type locality
I discovered P. borrori in the upper 3 cm of sand at Foss Beach, New Hampshire (type locality: 43 degrees 0'24" lat., 70 degrees 44'30" long.). (ref. ID; 7679)
Descriptions
This thigmotactic ciliate (approximately 85 um in length) is cephalized with a flexible peristomial lobe anteriorly and is fairly supple posteriorly. The ciliature of the cephalized region includes 3 frontal cirri, a paroral cirrus, 5-6 collar membranelles, approximately 12 lapel membranelles, and an endoral and paroral membrane. The anterior end of the paroral membrane is differentiated into a peristomial cirrus. Posteriorly the cell possesses right and left marginal cirri, a longitudinal series of midfrontal cirri, 2 accessory transverse cirri, and a U-shaped group of transverse cirri that emerge from a ventral concavity. The posterior end of the left marginal cirral row is differentiated into a set of 4-6 posterolateral cirri. On the dorsal surface are six bristle rows with long (7 um) bristle cilia; 2 or 3 groups of caudal cirri are associated with the rightmost dorsal kineties. The 12-20 macronuclei are arranged in 2 longitudinal arrays on either side of the midfrontal cirri. A postbuccal inclusion (7 um in diameter) containing both a crystalline and an opaque particle is present in P. dragescoi. Food vacuoles contain various kinds of diatoms. (ref. ID; 7679)
Etymology
This species is named in honor of Dr. Jean Dragesco. (ref. ID; 7679)
Type locality
I discovered P. dragescoi in medium-fine sand between the mean tidal level and mean low water of Foss Beach, New Hampshire (type locality: 43 degrees 0'24" lat., 70 degrees 44'30" long.). (ref. ID; 7679)
Psammocephalus faurei (Dragesco, 1963) Wicklow, 1982 (ref. ID; 7679 redescribed paper) reported author and year? (ref. ID; 191)
Descriptions
The individuals of this population range from 80 to 175 um in length and are supple with a flexible cephalized anterior. This species appears less thigmotactic than D. ehrenbergi. The cephalized region forms a ventral peristomial lobe; the ciliature of this region consists of 3 frontal cirri, a paroral cirrus, 9 collar membranelles, approximately 25 lapel membranelles and an endoral and paroral membrane. The anterior end of the paroral membrane is differentiated into a peristomial cirrus. On the posterior portion of the cell there are right and left rows of marginal cirri; the left marginal cirri are divided into a row of 17-19 anterior cirri and a posterolateral group of approximately 14 cirri. A longitudial series of midfrontal cirri, subtended by a U-shaped group of 8-10 transverse cirri and 2 accessory transverse cirri, are also present, as well as 2 migratory cirri (located just posterior to the distal collar membranelles). Although the cytoskeleton is less complex than D. ehrenbergi, a posterior cytoskeletal trunk, formed by the union of large anterior microtubular bundles of each transverse cirrus, is present. On the dorsal surface are 6 rows of bristles; most rows consists of approximately 15 bristle complexes, each bearing a long (6-7 um) cilium. Row 4, however, consists entirely of short (3 um) bristle. Although most of the bristle complexes of rows 2 and 3 possess long cilia, the anterior ends of both these rows (on the cephalized portion of the cell) possess short (3 um) cilia. Caudal cirri are associated with the rightmost dorsal kineties. Numerous kinds of diatoms are found within the food vacuoles. The cell is multimacronucleate possessing 16-35 macronuclei. (ref. ID; 7679)
Morphogenesis: I observed both morphogenesis of re-organization and an incomplete series of morphogenesis during cell division in P. faurei. During re-organization a longitudinal series of 10-12 oblique streaks are formed on the ventral surface: from the leftmost streak differentiates the paroral apparatus including the paroral cirrus; from the remaining streaks differentiate 4 oblique (later transverse) ranks of frontal cirri. The first (posteriormost) rank forms the transverse cirri; the second rank forms the accessory transverse cirri only; the third rank forms the longitudinal series of midfrontal cirri and, from rightmost procirrus, a migratory cirrus; the fourth rank forms the second migratory cirrus and the remaining anterior frontal cirri. The migratory cirri are later positioned just posterior to the distal collar membranelles. Right and left marginal cirri arise by within row development. The left marginal streak divides to form the anterior marginal row and the posterolateral marginal group. Caudal cirri develop from the rightmost dorsal kineties. Parental membranelles dedifferentiate (at least partially), then reform. A similar process occurs during cell division morphogenesis. First, an oral primordium and a longitudinal series of obique streaks arise on the cell surface while the parental paroral apparatus and midfrontal cirri dedifferentiate. Two frontal fields, each consisting of 4 transverse ranks of procirri, appear by mid-division - each rank develops a similar manner as during re-organization. More procirri develop from frontal streaks than are present in late division (when they are presumed to be resorbed). The paroral apparatus, paroral cirrus, migratory cirri, marginal cirri and caudal cirri all differentiate as in re-organization morphogenesis. (ref. ID; 7679)
Type locality
P. faurei was first described by Dragesco, 1963, from a population in fine marine sand at Roscoff, France. I discovered an additional population of this species in sand near mean low water of Plum Island Mass. (ref. ID; 7679)
Psammocephalus lithophora (Faure-Fremiet, 1954) Wicklow, 1982 (ref. ID; 7679 redescribed paper)
Descriptions
This is an elongate (120-135 um) strongly thigmotactic ciliate with a marked cephalization: the anterior cephalized region is supple and mobile while the posterior portion of the cell is rigid. Right and left marginal cirri and a longitudinal series of frontal cirri emerge from cortical grooves on the ventral surface. A U-shaped group of 7-9 transverse cirri lie within a ventral concavity that is continuous with the midventral groove. A peristomial lip borders the cephalized region ventrally; from a cleft in this lip, just right of the lapel membranelles, extend a small group of cilia that may represent an anterior differentiation of the paroral membrane - presumably a peristomial cirrus: "un sillon oblique occupe par une courte rangee de cirres fins que representent, vraisemblablement, les cils paroraux". Just below the cephalized region, on the right side of the cell, is a statocyst-like inclusion - the "vacuole a concretion" (Faure-Fremiet, 1954). (ref. ID; 7679)
Type locality
In 1954 Faure-Fremiet described the marine interstitial hypotrich P. lithophora from surface sands (0.15-0.40 um) of the Concarnearu region of France. (ref. ID; 7679)