Chaetognatha Taxonomy
Extant forms. Anus opens on the ventral side just before trunk/tail septum. Ref: 1970.
Ducts connect genitals between trunk and tail. Ref: 1958, 1959.
Lateral ventral transverse muscles in trunk and tail. Part of order Phragmophora Tokioka, 1965 (lateral ventral trnsverse muscles are present; usually various kinds of glandular structures present). Ref: 1958, 1959.
One pair of lateral fins. Ref: 1962.
Reported in Bermuda waters. Very rare, probably due to its vertical distribution. Bathyplanktonic. Ref 1769.
No ducts connecting genitals present. Ref: 1958, 1959.
Lateral ventral transverse muscles in trunk only. The remaining part of order Phragmophora Tokioka, 1965. Ref: 1958, 1959.
Tail segment is relatively large. One or two pairs of lateral fins. CC is on the neck and is wider than long. Benthic or benthoplanktonic. Ref: 1970.
Originally, all members were placed under the genus Spadella. Salvini-Plawen (1986) noted three species groups and proposed two new genera. The "Cephaloptera group", Spadella (s. str.), has one pair of lateral fins and lacks digitate adhesive organs. The "Pulchella group", Gephyrospadella, has one pair of fins, but adhesive organs are present. He considered this group a bridge (=Gephyro) between Spadella and Paraspadella. Finally, the "Schizoptera group", Paraspadella, has two pairs of fins and has prominent adhesive organs ventrolaterally at the tail segment. While Bowman & Bieri (1989) agreed that the presence of adhesive organs is taxonomically imporatant, they questioned the importance of the number of lateral fin pairs. They point out that immature individuals of Paraspadella have only a single pair of fins, but, with sexual development, the fins become separated into anterior and posterior parts by the lateral growth of the vagina. Thus, Gephyrospadella was collapsed into Paraspadella
One pair of lateral fins is present. Digitate adhesive organs are absent. Ref: S-V 86, B+B 89.
One or two pairs of lateral fins are present. Digitate adhesive organs are present. Ref: S-V 86, B+B 89.
One pair of lateral fins is present, beginning relatively far anterior of the transverse septum. Digitate adhesive organs are absent. AT and PT are absent. Ventral transverse muscles are confined to the anterior half of the trunk. Monospecific genus. Ref: T 39.
The exact placement of this genus is questionable. Tokioka (Ref 1970) placed it into Eukrohniidae, but most authors now believe it may belong in Spadellidae. Ref: 1958, 1962.
One pair of lateral fins is present. Digitate adhesive organs are absent. A large number of ornamented AT and PT are present. Ref: C 96.
Tail segment is comparatively short. One pair of lateral fins is present, beginning at or near VG. AT are absent. ID is absent. Bathypelagic. Ref: 1961, 1970.
Apical gland cell complex, or papillae tuft, is present at the anteroventral point of the head. Ventral transverse muscles extend from neck to at least the posterior edge of the VG. Ref: McLelland 1989.
BL 19-32 mm. T% <24. The body is slender and rigid. PT 23-25. Hooks 9-10. The clear amber hooks are thick and end in claws. Eyes are present with ommatidia-like structures. Gut contains oil droplets. Ovaries are straight with small ova in 3 or 4 rows. Ref: 1958.
Reported in Bermuda waters. Not common. Mesoplanktonic 600 - 1500 m. Ref 1769.
BL 34-40 mm. PT 11-16. Hooks 11-14. Eyes are present with photoreceptive cells, but without pigment. CC is oval, extending from behind the eyes to the neck. Sometimes a thin collarette is visible around the VG. The gut is orange. Ref: 1958.
Reported in Bermuda waters. Not common. Meso/bathyplanktonic >800m. Ref 1769.
BL 34-40 mm. PT 20-30. Hooks 10-14. Teeth and hooks are brownish. Eyes are present with photoreceptive cells and a triangular pigment cell. A foamy collarette is present around the VG. Ref: 1958.
Reported in Bermuda waters. Rare (Ref 1696, 1769). Mesoplanktonic 700 - 2000 m (Ref 1769).
No ventral transverse muscles; coelom is entirely hollow. Glandular structures are weakly developed on body surface. Ref: 467, 1958, 1959, 1970.
Tokioka (Ref 1970) divided this order into two suborders based on the morphology of the hooks and teeth. Suborder Ctenodontina Tokioka, 1965 has gently curved hooks, comb-shaped tooth rows, and slender teeth. This suborder included the families Sagittidae and Pterosagittidae. Suborder Flabellodontina Tokioka, 1965 has abruptly curved hooks and stouter teeth which are arranged in the shape of a fan. Krohnittidae was contained in this suborder. However, this classification was abandoned after the inclusion of other families into the order because these families have features that do not follow this scheme (ex., Krohnittellidae has no teeth).
Two rows of teeth (AT and PT) are present. Eyes pigmented, with the exception of Caecosagitta. Two pairs of lateral fins (AF and PF) are present (fins may be appressed or joined by tissue). AF lie on the trunk and PF lie partly on the trunk and tail. Ref: 465, 467, 1961, 1962, 1970.
CC is very elongate, extending from just posterior of the CG to the anterior portion of the trunk. ID is absent. Lateral fins are wholly rayed. Ref: 1961, 1970.
The bipunctata group. Ref: 1969.
BL 14-18. Body is transparent. AT 5-8. PT 11-17. Hooks 8-10. Eyes are very small. Collarette is present on entire body with a particular, "punctuated" aspect and with a swelling between the PF and SV. ID is absent. SV is small with a distinct rounded anterior part. Ref: 1958.
Reported in Bermuda waters. Fairly common (Ref 1701, 1704, 1950) to abundant (Ref 1696). Epiplanktonic (Ref 1696) to 50 m (Ref 1769). Vertical migrator (Ref 1696), but only in the upper most waters (Ref 1769).
BL 11-13 mm. Body is transparent. AT (15-18) are more numerous than PT (11-14). Hooks 7-8. Collarette is present, mostly on neck. ID is absent. AF is short, beginning at the posterior end of the VG. SV is oval with an anterior prominence. Ref: 1958.
Reported in Bermuda waters. Very rare. Ref 1696.
CC begins posterior of the eyes. ID is present. Lateral fins are wholly rayed, with rays almost perpendicular to body. SV is situated just behind PF and is apart from the base of the CF; the anterior glandular portion is not differentiated externally. Tail segment is relatively long. Distribution is usually limited to inlet or neritic waters. Ref: 1961, 1963, 1970.
The neglecta and oceania groups. Ref: 1958, 1969.
Head is almost rectangular in shape, longer than wide, with numerous fine, brown hooks. Central nuclear and peripheral cortical regions are not differentiated in the eye and pigments are not found in these regions. ID is absent. Lateral fins are nearly wholly rayed. A monospecific genus. Ref: 1962, 1970.
A part of the bipunctata group. Ref: 1969.
BL 16-22 mm. AT 6-10. PT 20-38, numerous. Hooks 10-12. Teeth and hooks are deep brown. Eye pigment is absent. Gut is reddish. AF begins far posterior of VG. Ref: 1958.
Reported in Bermuda waters. Common. Mesoplanktonic >700 m. Ref 1769.
CC extends from the neck to anterior part of trunk. ID is present. Fin rays diagonal to body rather than perpendicular, appressed, not irregularly spaced, and missing in some areas. PF are situated mostly on trunk. SV separated from PF. Between one third to one half of trunk length is anterior to transverse septum. No marked constriction of the tail at the transverse septum. Body musculature is weakly developed. Mature ovaries approach, but usually do not reach, VG, with relatively long and narrow ova in a single row. Mesosagitta is a closely related genus. Ref: 1960.
A part of the minima group. Ref: 1958.
The taxonomy of this group is rather confused. Originally, all members were placed in Mesosagitta (Ref 1970) and then later placed in their own genus (Ref 1960). Pierrot-Bults (Ref 1975) suggested that D. neodecipiens is a synonym of D. decipiens, while D. sibogae is not. However, her view is not widely accepted. D. sibogae is often referred to as D. decipiens, and D. neodecipiens still appears in the literature. Bieri (Ref 1960) cast doubt on the validity of D. batava.
BL 8-14 mm. T% 19-32. Body is slender with a small head. AT 4-10. AT are small and triangular and form imbricate rows. PT 6-20, long and narrow. Hooks 5-8. Eye pigment is in the form of an elongated "T", with all three branches about equal in length. CC extends from the neck to the trunk. Collarette is absent. ID is prominent. A rayless zone is present at the anterior end of both lateral fins (although some references state the fins are wholly rayed). AF is long and narrow, beginning at the posterior end of the VG. AF is as long as or slightly longer than PF. PF is rounded and widest near the posterior end. PF is equally situated on trunk and tail. Ovaries are short, extending to the posterior end of the AF. The anterior end forms a sharp point which continues as a fine fiber connected to the body wall. Ova are rather large in a single row. Constriction at tail septum is not present. SV is situated at an equal distance from the PF and CF. SV is long and narrow with a glandular knob at the anterior end. SV ruptures along the whole lateral side. Cosmopolitan, oceanic, temperate/warm oceanic waters, mesopelagic. Ref: 465, 466, 1958, 1961, 1975, Tokioka 1959 (as D. neodecipiens).
Developmental stage characteristics are similar to D. sibogae (see below).
Reported in Bermuda waters. Fairly common (Ref 1701, 1704, 1950) to common (Ref 1769). Mesoplanktonic 300 - 800 m (Ref 1769).
BL 13-20 mm. T% 18-29. Body is slender, flaccid, and widest at the ovaries. Head is broader than D. decipiens and is well differentiated from the neck. AT 6-13. AT are short and triangular, forming imbricate rows. PT 9-23. PT are long and narrow. Hooks 5-8. Hooks are long and strong. Eyes are oval. Eye pigment forms a large, elongated T-shape with the bottom of the "T" pointed towards the center and shorter than the other two branches. Collarette is absent or so small that it is nearly absent. ID is prominent. The lateral field is wide, about ½ the width of the dorsal or ventral side. AF is long, narrow, and tapered, beginning at the posterior end of the VG with a small rayless zone at the anterior end. PF is triangular, widest near the posterior end, and is broader and slightly shorter than the AF. PF is equally situated on the trunk and tail, or slightly more on the trunk than the tail, and also has a small rayless zone anteriorly. Ovaries are slender and long, extending to nearly the VG, and are rounded at the distal end; ova are small, oval-cylindrical, uniform in size, and form a single row. Constriction at tail septum is not present. SV is adjacent to the CF and well separated from the PF. SV is pyriform, with a prominent glandular knob anteriorly. SV has a prominence, or small shield, at the middle of the anterior end of the ventral part. SV opens laterally at the broadest part of the dorsal side. Oceanic, tropical/subtropical, shallow mesopelagic, 200-500 m. Ref: 466, 1958, 1967 (as D. decipiens), 1969 (as D. decipiens), 1975.
Refs where D. decipiens are probably D. sibogae, but are not included in the above description: 467, 1968, 1971, 1972.
| Stage | Male | Female | Size (mm) |
|---|---|---|---|
| I | Testes as fine tubes; SV begin to appear | Ovaries thin tubes | 10 |
| II | Testes filling tail cavity; SV developing | Ovaries reaching up to anterior end of PF | 12 |
| III | Spermatids and spermatozoids filling tail; SV filling | Ovaries reaching up to posterior end of AF | 13-14 |
| IV | Tail empty; SV full, bursting, or discharged | Ovaries reaching anterior ¼ of AF | 14-16 |
Reported in Bermuda waters. Common. Epi/mesoplanktonic 200 - 500 m. Ref 1769.
CC begins posterior of the eyes. ID is present. Ref: 1961. Lateral fins either wholly rayed or with a narrow inner rayless zone on PT (F. robusta, americana, ferox, and tokiokai).
The hispida group. Ref: 1958, 1969.
BL 8-12 mm. Body is firm, stout, and semi-opaque. AT 6-9. PT 10-15. Hooks 7-8. Head is large and rounded. Collarette is present on entire body. AF begins at the posterior end of VG. Ovaries extend to neck. SV has a distinct rounded anterior knob and touches the CF. Ref: 1958.
Reported in Bermuda waters. Rare outside reefs. Ref 1696.
BL 16-18 mm. Body is firm, stout, and semi-opaque. AT 7-10. PT 12-14. Hooks 5-6. Collarette is present on entire body. AF begins in the middle of the VG. Ovaries extend to neck. SV is elongate and touches the CF. Ref: 1958.
Reported in Bermuda waters. Rare. Ref 1701, 1950.
Body is very flaccid and highly transparent. Trunk musculature is inconspicuous. Vestibular pit is circular. CC is short and confined to the head, extending from just posterior of the CG to the neck. ID is absent. Lateral fins contain distinctive rayless zones. AF are separated from PF and are well posterior of VG. Ref: 466, 1961, 1962, 1970.
The hexaptera group. Ref: 1958, 1969.
BL 38-40 mm. T% 15-21. Body is widest at the middle. Head is broad and fairly well differentiated by neck. AT 2-4 (usually 3). AT are elongate, thin, and sharp with wide bases and usually project forward. PT 2-8 (usually 3-5). Hooks 6-10. Hooks are wide and strongly curved. Eyes are small and oval with longest axis parallel to the body. Eye pigment is small, elongate, and T-shaped, with the middle branch directed towards center. CC is pyriform, extending from the eyes to the neck. Collarette is absent (although Ref 1958 mentions collarette from neck to VG in Red Sea specimens). AF is short and semi-elliptical, with rays only on outer edge. These rays are wider spaced in the anterior than at the posterior. In early stages, the anterior AF is rayless; as maturity progresses, the rayed zone extends anteriorly. AF is situated midway between the VG and the tail septum, with the anterior end at about the middle of the body. PF is large and deltoid, with internal and anterior rayless zones. PF extends from trunk to about the middle of the tail segment with two-thirds of its length on the trunk. PF is longer and wider than AF. Ovaries are narrow and long, reaching VG, and bent at right angles at base when immature; ova are small (0.5 mm diameter) and spherical and are arranged dorsoventrally in three rows, numbering about 250. A slight constriction is present at the tail septum. SV is small and spherical, separated from PF, and close to CF (gap equal to SV length). SV breaks open along the middle of the dorsal lateral region. VD are short, wide and horn-shaped. CF is rounded. Oceanic, cosmopolitan, temperate, tropical/subtropical, 0-500 m. One of the largest species of Chaetognatha, reaching up to 70 mm. Ref: 464, 465, 466, 467, 1958, 1961, 1964, 1965, 1966, 1967, 1968, 1969, 1971, 1972, 1973.
| Stage | Male | Female | Size (mm) |
|---|---|---|---|
| I | Testes begin to appear; SV incipient | Ovaries thin tubes, extending to anterior portion of PF | 22 |
| II | Testes filling tail cavity; SV developing | Ovaries reaching up to posterior end of AF | 27-30 |
| III | Tail empty or partially empty; SV full or broken | Ovaries reaching close to posterior end of VG | 34 |
| IV | Tail empty; SV broken | Ovaries filled with large ova, reaching VG | 38-40 |
Reported in Bermuda waters. Common (Ref 1701, 1704, 1769, 1950). Abundant year-round, with maximum in summer or autumn (Ref 1696). Epiplanktonic (Ref 1696) to 300 m (Ref 1769). Strong vertical migrator (Ref 1769).
BL 6-30 mm. Body is flaccid, transparent, and wide, widest at center. T% 14-21. AT 3-11. AT are wide and overlapping. PT 4-17. Hooks 6-11, with a wide base and a short curved sheath. Head is small, wider than long, but broad when expanded. Neck is short and conspicuous. Eyes are situated closer to each other than to the sides of the head. Eyes are small and oval, with the longest axis tilted in relation to the longitudinal axis of the head. Eye pigment is shaped as a small star, with the tips truncated and two arms longer than the other three. CC lies only on the head and is sinuous or hourglass-shaped. Collarette is absent. Lateral fields are wide. VG is equidistant from the neck and AF. AF have an anterior and inner rayless zone and are sparsely rayed. AF is very short, more than 80% of the tail length and 14-15% of the body length, narrow, elongate, and round. AF is situated far posterior of the VG by a distance greater than the length of the fin. PF is deltoid, is wider (widest at the tail septum) and longer than the AF, and also has an anterior and inner rayless zone. PF is 16-18% of the body length, with more than ½ (about two thirds) on trunk. Ovaries are broad and short. There are three maturity cycles: ovaries extend to 1) two thirds of the extent of the PF on the trunk, 2) to the anterior of the PF, and 3) to the posterior of the AF. Ova are relatively small (0.16 - 0.2 mm diameter, depending on maturity cycle, although larger ones may be present from previous cycles), spherical, and are arranged in three dorsal ventral rows, numbering 16 to >100, depending on maturity cycle. A marked constriction is present at the tail septum. Testes are situated at the posterior end of the tail segment, forming a "V" shaped cluster, extending from the tail tip to the posterior of the PF. SV is small and spherical. SV is in contact with the caudal fin, but is distant from the PF. SV breaks open at the anterior lateral margin along the dorsal side. Cosmopolitan, 0-200 m, tropical/subtropical and temperate oceanic waters, euryhaline. Ref: 464, 465, 466, 467, 591, 1958, 1961, 1964, 1965, 1966, 1967, 1968, 1969, 1971, 1972, 1973, 1981, 1987, 1988.
| Stage | Male | Female |
|---|---|---|
| I | No testes or SV visible | Ovaries extending ¼ or ½ of length of PF along trunk |
| II | Testes well visible; SV begin to appear | Ovaries extending to middle of extent of PF on trunk or anterior of PF |
| III | Testes filled with sperm; SV begin to fill | Ovaries extending to anterior of PF or posterior of AF |
| IV | SV full, bursting, or empty | Ovaries extending to anterior end of PF or up to AF |
Reported in Bermuda waters. Rare (Ref 1696), especially in spring and fall (Ref 1704), to common (Ref 1701, 1950). Epiplanktonic (Ref 1696) to 300 m (Ref 1769).
CC extends from the neck to the anterior portion of the trunk. ID is present. Fin rays are sparse or missing in some parts of the lateral fins and are aligned perpendicular to body. Most of the PF is situated on the trunk. Less than ¼ of the trunk is anterior to transverse septum. There is a marked constriction of the tail at the transverse septum. SV are situated apart from the posterior end of PF. Occur frequently in the mesopelagic, but mainly epipelagic. A monospecific genus. Ref: 1960, 1961, 1970.
The minima group. Ref: 1958.
BL 5-11, small. Body is slender, fragile, flaccid, and transparent or translucent. The body is widest at the posterior part of the trunk. TL% 15-24. Tail segment is short, narrow, and pointed. The small head is narrow and long and is not much wider than neck and body. AT 2-7. PT 3-16. Hooks (5-11) are short with the tips strongly curved inwards. Eyes are large and oval with a three lobed or T-shaped pigment, with the middle branch directed towards center. CC is oval and lies completely on the trunk anterior. Collarette is absent. A small ID is present, but difficult to distinguish because of the characteristically large and dilated gut. Lateral travecula connecting gut and body wall is sometimes evident. The lateral fields are fairly wide. VG is located about ¼ the BL from the anterior end. Lateral fins are fragile and are often broken or destroyed. AF is very narrow, rounded, and rayless, or with only a few rays marginally. AF is posterior to the VG. AF is shorter and narrower than PF. PF is rounded and is completely or marginally rayed, with the rays directed perpendicular to the body. About 75% of the PF lies on the trunk segment. A pronounced constriction is present at the transverse septum. Ovaries are short and thick, extending to the middle or anterior PF, but completely filling trunk coelom in region that they occupy. Ova are large and round (0.2 mm diameter), arranged in a single row, numbering 3-5. SV is elongated and ovate (bedoti-type), with the anterior part larger than the posterior. SV contacts the CF and is widely separated from the PF. SV breaks open along the lateral dorsal margin of the anterior half. Cosmopolitan, epipelagic, temperate/tropic waters. Ref: 465, 466, 467, 1958, 1961, 1964, 1966, 1967, 1968, 1969, 1971, 1972, 1973, 1981, 1982, 1985, 1987.
| Stage | Male | Female | Size (mm) |
|---|---|---|---|
| I | Testes not yet visible or beginning to appear; SV absent | Ovaries short, with small oocytes | 4 |
| II | Testes filling tail cavity; SV begin to develop | Ovaries extending to posterior one third of PF on trunk; oocytes of several orders visible | 5-6 |
| III | Spermatids and spermatozoids fill tail cavity; SV begin to fill | Ovaries extending to middle of PF on trunk; ova large | 6-7 |
| IV | Tail segment filled or partially or totally empty; SV full | Ovaries extending to anterior PV | 9-10 |
Reported in Bermuda waters. Common (Ref 1701, 1950) to abundant (Ref 1704). Epiplanktonic to 300 m (Ref 1769).
CC is very elongate, extending from just posterior of the CG to the anterior portion of the trunk. Lateral fins are wholly rayed. ID is present. Ref: 1970.
The euneritica (including Z. bruuni and A. crassa) group. Ref: 1969.
BL 15 mm. Body is transparent. AT 3-8. PT 6-17. Hooks 5-9. Eyes have a small pigment cell. A small collarette is present, mostly on neck. ID is absent(?). AF is short. Ova are small and numerous. SV touches PF and has an anterior swelling. Ref: 1958.
Reported in Bermuda waters. Rare. Ref 1701, 1950.
Body is flaccid. Vestibular pit is a slit. CC is short and confined to head. ID is absent. Lateral fins contain distinctive rayless zones. AF closely approach or are joined to PF by rayless, inflated epidermal tissue (fin bridge) and approach or reach VG. Ref: 1961, 1962.
The lyra or maxima group. Ref: 1958, 1969.
BL 30-42 mm. T% 14-20. Body is transparent and is widest at the middle. Head is wider than long and well differentiated by neck. AT 2-8. PT 2-12. Hooks 2-11. Hooks are short, robust, transparent, and well curved with a straight tip. Hooks in mature specimens have a large characteristic basal swelling on inner edge, forming secondary hooks. Teeth and hooks tend to be lost as the animal matures. Eyes are small and oval with a small, elongate, and Y-shaped eye pigment, with the bottom of the "Y" pointing towards the center. CC is pyriform, extending from behind the eyes to scarcely onto the trunk. Collarette is absent (although several references mention that a small, weak collarette may be present). Fin bridge is wide, giving the appearance of a continuous fin in immature specimens. AF is long, becoming broader posteriorly, and rounded, with the outer posterior one third rayed. AF emerges slightly posterior of the VG and is longer than PF. PF is triangular and wider than the AF. PF is rayed along the outer and posterior edges. Greater than ¾ of the PF is situated on the trunk. Ovaries are long and broad, reaching about two thirds up the AF, often with a conspicuous mass of sperm at the anterior end; ova are small (0.2 mm diameter), spherical, and arranged in four dorsal ventral rows, numbering greater than 200. Immature ovaries bend at their base at right angles to the dorsal side. A constriction is present at the tail septum. SV is small, oval, and situated close to PF. SV breaks open along the middle region of the dorsal lateral side. CF is bilobate, a characteristic shared only by P. gazellae and P. scrippsae, both of which are possibly P. lyra and occur in cooler waters. Oceanic, cosmopolitan, temperate, tropical/subtropical, 100-1000 m. Typically found in low temperature, low oxygen, and high salinity waters. Ref: 464, 465, 466, 467, 1958, 1961, 1966, 1967, 1968, 1969, 1971, 1972, 1974.
| Stage | Male | Female | Size (mm) | AT | PT | Hooks |
|---|---|---|---|---|---|---|
| I | Testes as fine tubes; SV not present | Ovaries extending to posterior one third of PF on trunk | 17-22 | 8 | 12 | 7-9 |
| II | Tail filled with spermatids; SV beginning to appear | Ovaries extending to nearly anterior end of PF | 22-25 | 8 | 6-11 | 6-8 |
| III | Tail filled with sperm or emptying; SV full | Ovaries extending to posterior one third of AF | 27 | 6-8 | 4-5 | 3 |
| IV | Tail and SV empty | Ovaries extending to anterior end of AF | 30-42 | 3-5 | 2-4 | 3 |
Reported in Bermuda waters. Common (Ref 1701, 1704, 1950) to abundant (Ref 1769) with late summer maximum (Ref 1696). Epiplanktonic (Ref 1696) or mesoplanktonic to 1250 m (Ref 1769). Clear ontogenetic vertical distribution (Ref 1769).
BL 55 mm. T% 19-29. AT 4-6. PT 5-7. Hooks 4-8. Teeth and hooks are brownish. AF begins at VG. Ref: 1958.
Reported in Bermuda waters. Rare. Ref 1769.
Inner edges of hooks have heavy, coarse serrations. The pigmented area of the eye is small and elongate. CC is very elongate, extending from just posterior of the CG to the anterior portion of the trunk. ID is absent. Lateral fins are wholly rayed except for an inconspicuous narrow rayless zone along the base of the anterior half of the PF. SV is complex, consisting of an elongated trunk and anteriorly-directed, distal knob, which is species specific. SV is situated just behind the PF and is apart from the CF. A distinctive swelling is present near the middle of the vas deferens. Ref: 1961, 1962, 1963, 1970.
The serratodentata group. Ref: 1958, 1969.
BL 7-17 mm. T% 20-33. Body is slender and rigid. AT 3-11. PT 5-20. Hooks 5-9. Hooks are finely serrate on the concave, inner margins, serrations low in profile, visible at 40-100X magnification in most specimens over 5 mm. Head is small with small oval eyes. Eye pigment is shaped like an elongated "T", with the bottom of the "T" pointing towards the center. An elongate, sinuous CC extends from just behind the cerebral ganglia onto the trunk for a distance at least twice the length of the head. Collarette is vestigial, usually not distinct, at neck. Body width is the same from head to tail septum. AF extends to, or nearly to, the posterior end of the VG and has a small anterior internal rayless zone. AF is narrow, broadening at the posterior. PF is situated mostly on trunk and is widest just behind tail septum. PF is broader than and is as long as, or slightly longer than, the AF. PF is shaped like a bell or guitar and has a small inner anterior rayless zone, which ends near the tail septum. Ovaries reach to about the VG; ova are small (0.09 mm diameter), spherical to cuboidal, in one row, numbering about 40. SV reaches, or nearly reaches, the PF and is separated from the CF. SV consists of a clearly demarcated trunk and knob; the knob is broader than the trunk and consists of two anterior lateral papillae. SV breaks open at an external opening situated anterior laterally on dorsal side of the knob. VD is as long as SV. Common, oceanic, tropical/subtropical, temperate, 0 - 500 m. Ref: 464, 465, 466, 467, 591, 1958, 1961, 1965, 1969, 1972, 1982, 1983, 1984, 1985, 1986.
| Stage | Male | Female | Size (mm) |
|---|---|---|---|
| I | Testes as fine tubes; SV begin to appear | Ovaries as fine tubes, extending to anterior of PF | 7 |
| II | Testes fill tail cavity; SV conspicuous | Ovaries extend to posterior of AF | 9-10 |
| III | Tail filled with spermatogonia and spermatozoids; SV turgid and full | Ovaries extend to anterior ¼ of AF | 10-11 |
| IV | Tail partially or totally empty; SV full or empty | Ovaries with large ova, filling coelom, extending to VG or close to neck | 12-14 |
Reported in Bermuda waters. Abundant year-round (Ref 1696, 1704), especially in March when it can make up >25% of the total chaetognatha numbers (Ref 1701, 1769, 1950). Vertical migrator (Ref 1769) in the top 50 m (Ref 1696). Epiplanktonic to 300 m (Ref 1769).
The pigmented area of the eye is markedly small as compared with the size of the eye. Collarette is prominent, extending to at least the AF. CC extends from the neck to the anterior portion of the trunk. ID is prominent. Most of the PF is situated on the trunk. Rayless zones on the lateral fins are defined. The body is much stouter than in Mesosagitta, a closely related genus. Occur in mid and deep seas. Ref: 1961, 1970.
The planctonis group. Ref: 1958, 1969.
The specific status of S. planctonis and S. zetesios is uncertain. S. zetesios was regarded by Ritter-Záhony (1911) to be synonymous with S. planctonis. However, David (Ref 1976) resurrected S. zetesios as a separate species. This was refuted by Pierrot-Bults (Ref 1977, 1978), who considered the characters that separated the two species have no specific value and often overlap. But Pierrot-Bults (Ref 1979) later softened her stance, stating that while S. planctonis is the correct species, it consisted of two forms, S. planctonis forma planctonis and forma zetesios.
BL 37 mm. T% 19-30. AT 5-8 (9). PT 10-12 (14). Hooks (6) 8-11. Eye pigment is T-shaped. CC extends from the posterior end of the head to about half way between the head and VG. Collarette is very prominent, extending at least to AF and to the tail in mature specimens; this feature may account for the descriptions of a fin bridge in some of the references. Intestinal walls are characterized by voluminous vacuolar cells which are easily discernible through the body. AF is rayless at the anterior end and along the inner edge. AF begins as far as the middle of the VG and is longer than the PF, constituting 24-32% of the body length. PF is triangular, but slightly rounder than S. zetesios, and widest posteriorly, level with or slightly posterior to tail septum, with about ¼ extending onto tail segment. PT has an inner rayless zone. Ovaries completely fill body cavity; ova are small (0.2 mm diameter) in 4 or 6 rows, numbering greater than 400. SV is elongate and anteriorly rounded. SV is in contact, or nearly so, with PF and separated from CF (Ref 465 states equal distant from PT and caudal fin). SV is simple, oval in shape, and breaks at edge of dorsal side. SV is usually absent in specimens < 25 mm. CF is broad and truncate or slightly rounded. Tropical/subtropical, 0-1000 m. Ref: 465, 466, 467, 1958, 1964, 1966, 1969, 1972, 1976, 1977, 1979, 1981.
Reported in Bermuda waters. Not common (Ref 1696, 1769). Seasonal, with maximum in the spring (Ref 1696, 1701, 1950). Epiplanktonic to 500 m (Ref 1769) or specially at surface (Ref 1696).
BL 39-45 mm. T% 20-33. Head is round, of medium size, and with a distinct neck. AT (6) 8-10 (12). PT (10) 15-19 (22). Hooks 8-11. Hooks are more curved and less numerous in later stages. Eyes are large and oval. Eye pigment is small and T-shaped, with the bottom of the "T" directed towards the center. CC is elongated, extending from the neck to the VG. Collarette is similar to S. planctonis. Body is same width from head to tail septum. Lateral fields are narrow. Intestinal walls are characterized by voluminous vacuolar cells which are easily discernible through the body. AF is rayless or very sparsely rayed at the anterior end and has an inner rayless zone. AF begins at or just posterior of the VG. AF is narrower and slightly longer than the PF, constituting 20-26% of the body length. PF is triangular and widest posteriorly, level with or slightly anterior to tail septum, with about one third extending onto the tail segment. PT has an anterior and inner rayless zone, which extends to about the middle of the portion of the fin on the tail. Ovaries are long, reaching halfway between head and VG in largest specimen, and are thin tubes with thick walls, containing large amounts of fatty material; ova are small (0.2 mm diameter), arranged in 3 dorsal ventral rows, numbering greater than 300. SV is oval in shape, close to the PF but not touching them, and some distance from the CF. SV is formed by a soft membrane which breaks easily along a dorsal lateral ridge, leaving two flaps when broken. SV is usually absent in specimens < 25 mm. Cosmopolitan, mesopelagic in tropical/subtropical regions, epipelagic in temperate regions. Ref: 465, 466, 467, 1958, 1961, 1966, 1969, 1971, 1972, 1976, 1977, 1979, 1981.
| Stage | Male | Female | Size (mm) |
|---|---|---|---|
| I | Testes begin to appear; no SV apparent | Ovaries as thin tubes, extending to ½ extent of PF on trunk | 20 |
| II | Testes fill tail cavity; spermatogonia visible; SV begin to appear | Ovaries as fine tubes reaching to anterior end of PF | 29 |
| III | Tail filled with spermatogonia and sperm; SV oval, begin to fill | Ovaries as thin tubes reaching to middle of anterior third of AF | 32-34 |
| IV | SV filled or broken; oval groove indicating place once occupied by SV | Ovaries reaching to midway between neck and VG | 39-43 |
Reported in Bermuda waters. Not common. Mesoplanktonic 500 - 900 m. Ref 1769.
CC is very elongate, extending from just behind brain to the anterior portion of the trunk. ID is absent. Lateral fins contain a distinctive rayless zone. Ref: 1970.
Two rows of teeth. Massive collarette extends from neck to nearly the SV. Lateral bristles at the level of the VG. One pair of lateral fins, beginning at the trunk/tail septum. A monospecific family. Ref: 466, 1961, 1962, 1970.
The oval CC is longer than wide, extending below level of the neck. Lateral fins are completely rayed. The genus contains only one, widely distributed species. Ref: 467, 1961, 1970.
BL 7-16 mm. Body is short, stout, broad, robust, and opaque due to strong and thick longitudinal muscles. The body width is uniform from head to transverse septum. T% 32-47, long. The constriction at the transverse septum is clear. The head is larger than the body and clearly differentiated from trunk. Short AT 4-10. Long and conical PT 8-18. Teeth are deep brown in color. Hooks 7-10. Hooks are strong, curved, and finely serrated (but probably not visibly so under a dissecting microscope). Eyes are oval with the longest axis perpendicular (although a little tilted) to the body length and with a T-shaped pigment, the middle branch directed towards center. ID is absent, although there is a differentiation at the anterior of the intestine, showing small incipient diverticula. The oval, elongate CC is located on the anterior trunk, beginning in the region of the neck. The prominent collarette extends the length of the body and is most noticeable on the trunk. A pair of long, V-shaped "hair-fans" is present on the anterior third of the collarette, near the VG. Large cells of the collarette give the appearance of wire mesh. Unfortunately, the collarette is often destroyed during collection. VG is situated near the central region between the head and transverse septum. One pair of fully rayed, triangular or semi-circular lateral fins is confined to the tail segment, extending from the transverse septum to the SV. The fins are 21-24% of the total body length. The long, broad ovaries extend to the neck region. Spherical ova are large (0.2 mm diameter) and are arranged in 2 rows dorsoventrally, numbering about 45. SV are elongated, oval or bulged anteriorly, and about 0.45 mm across. SV is close to the CF and contacts the lateral fins. SV opens dorsally at the anterior lateral region. Cosmopolitan, 0-300 m, temperate/tropical waters. Ref: 465, 466, 467, 1958, 1961, 1962, 1964, 1965, 1967, 1968, 1969, 1971, 1972, 1981, 1988.
| Stage | Male | Female | Size (mm) |
|---|---|---|---|
| I | Testes as fine tubes; tail segment empty; no SV present | Ovaries as fine tubes reaching less than ¼ of length to neck | 5-6 |
| II | Tail segment filled with sperm; SV filling or full | Ovaries reaching up to two thirds of level from neck region | 7 |
| III | Tail segment empty; SV empty | Ovaries reaching up to level of VG | 8 |
| IV | Tail segment empty; SV disappear | Ovaries filling body cavity, reaching up to neck region | 9-10 |
Reported in Bermuda waters. Common (Ref 1701, 1704, 1950), with an autumn maximum (Ref 1696). Vertical migrator (Ref 1696, 1769). Epiplanktonic to 300 m (Ref 1769).
One row of long isosceles triangle shaped teeth, with the small side as the base, is present. Hooks are curved more abruptly than in Sagittidae. Collarette is absent. ID is absent. One pair of laterals fins, beginning on the posterior portion of the trunk. The shape of the caudal fin differs from that in the other families. This family contains one genus. Ref: 1961, 1969, 1970.
CC is short, beginning at the level of the neck. Lateral fins have a distinct interior rayless zone. Ref: 1961.
BL 11.4-16.5 mm. Body is stylet-shaped, uniform from neck to transverse septum, with a long tail. TL% 30-40. The head is smaller than the body and is not much broader than the neck. AT (8-14) are long, large, and pointed, consisting of a basal plate, intermediate piece, and the tooth proper, and cover the anterior of the head. AT are orientated almost perpendicular to the head's main axis and, when the tips meet, are arranged in the form of a cone. PT are not present. Hooks (5-10) are transparent and cutlass shaped. Eyes are oval with the longest axis almost perpendicular to the longitudinal axis of the head and with a T-shaped pigment, the middle branch directed towards center. CC is about as long as the head and is deltoid, extending from posterior of the eyes to the anterior trunk. No ventral transverse muscles are present in trunk and tail. Lateral fields are wide. VG is situated about midway between the neck and transverse septum. The single pair of broad, delicate lateral fins (32-35% BL) is semicircular and is only marginally and sparsely rayed, resulting in a weak fin that is often destroyed. Two-thirds of the fins lie along the tail segment. The fins do not extend far anteriorly, to about ½ - two thirds the distance from the transverse septum to the VG. The fins are widest at the transverse septum. The short, broad ovaries extend to the beginning of the lateral fins; spherical ova are large (0.2 mm diameter) and are arranged in two rows, one dorsal and one ventral, numbering 12 (fairly constant). SV is oval and elongate and contacts both the lateral and caudal fins. SV ruptures first at the anterior lateral edge of dorsal side, and then later extends to nearly the whole lateral side leaving only a small posterior portion intact. SV probably fills more than once during its life. CF is spatulate and is almost completely rayed except for a small portion at the base of the fin close to the SV. Epi- and mesopelagic (0-400 m), cosmopolitan, tropical/temperate waters. Ref: 464, 465, 466, 467, 591, 1958, 1961, 1964, 1966, 1967, 1968, 1969, 1971, 1972, 1981, 1982, Tokioka 1959.
| Stage | Male | Female | Size (mm) |
|---|---|---|---|
| I | Tail segment filling with spermatids; SV begin to develop | Ovaries extending to one fifth the length of the extent of fins on trunk; ova small | Up to 10 |
| II | Spermatozoids visible in tail; SV begin to fill | Ovaries extending to ½ the length of the extent of fins on trunk | 11-12 |
| III | Tail segment empty; SV in a regenerative process | Ovaries extending to two thirds the length of the extent of fins on trunk | 11-12 |
| IV | Tail segment empty and SV as in previous stage; or tail filled with sperm and SV filling | Ovaries extending to anterior end of fins | 12-16 |
Reported in Bermuda waters. Fairly common (Ref 1696, 1701, 1950) to abundant (Ref 1704). Epi/mesoplanktonic to 900 m (Ref 1769).
BL 8mm. AT 16. Hooks 8-11. Lateral fins are triangular and almost wholly rayed. Ovaries reach to at least the VG. Ova are in a single row. Ref: 1958.
Reported in Bermuda waters. Rare. Ref 1701, 1704, 1950.
AT and PT are absent. The single pair of lateral fins is completely rayed and begins posterior of the VG, extending onto the tail segment. A monogeneric family, Krohnittella Germain & Joubin, 1912. Ref: Bieri 89.
VG is replaced by a dorsal ganglion. The two pairs of lateral fins completely lack fin rays. One pair of teeth, which are highly curved, are present. Eyes are vestigial. Benthic or benthoplanktonic. A monospecific family, Bathybelos typhlops Owre, 1973. Ref: 657, Bieri 89.
The single pair of lateral fins is very broad and wing-like. Lateral fins originate far anterior of the VG. Eyes are well developed and pigmented. A thick collarette is present between the head and lateral fins. A monospecific family, Pterokrohnia arabica Srinivasan, 1986. Ref: Srinivasan 86.
AF = Anterior fin
AT = Anterior teeth
BL = Body length at maturity
CC = Corona ciliata
CF = Caudal fin
CG = Cerebral ganglion
ID = Intestinal diverticula
PF = Posterior fin
PT = Posterior teeth
T% = Percentage of tail length to total length
SV = Seminal vesicle
VD = Vas deferens
VG = Ventral ganglion
464. Fraser, 1957.
465. Pierrot-Bults & Chidgey, 1988.
466. McLelland, 1989.
467. Michel, 1984.
591. Suárez-Caabro & Madruga, 1960.
657. Owre, 1973.
1696. Moore, 1949. 343-µm mesh, 70-cm diameter closing nets. Various collections between 1938 and 1940 at 50-m depth intervals down to a maximum of 300 m.
1701. Grice & Hart, 1962 (Ecol. Monogr.). See Ref 1950.
1704. Deevey, 1971. 363-µm mesh, 1-m net. Two samples per month between March 1961 and April 1962, 500 m to surface.
1769. Pierrot-Bults, 1982. 330-µm mesh, 1-m² rectangular midwater trawl closing net. Various depth intervals were collected during March 1973. Eighteen day samples down to 2000 m and 20 night samples to 3500 m.
1950. Grice & Hart, 1962b (Progress Report). 230-µm mesh, ¾-m open net. Oblique tows to 200 m were collected September and December, 1959, and March and July, 1960.
1958. Casanova, 1999.
1959. Casanova, 1985.
1960. Bieri, 1991 (Six new genera).
1961. Lutschinger, 1993.
1962. Bieri, 1991b (Systematics).
1963. Tokioka & Pathansali, 1963.
1964. Boltovskoy, 1975.
1965. McLelland & Heard, 1992.
1966. Silas & Srinivasan, 1970.
1967. Sund, 1959.
1968. Srinivasan, 1979.
1969. Alvarino, 1967.
1970. Tokioka, 1965.
1971. Alvarino, 1992.
1972. Alvarino, 1983.
1973. Nagasawa & Marumo, 1976.
1974. Silas & Srinivasan, 1968.
1975. Pierrot-Bults, 1979.
1976. David, 1956.
1977. Pierrot-Bults, 1969.
1978. Pierrot-Bults, 1970.
1979. Pierrot-Bults, 1975.
1980. Chidgey, 1989.
1981. Alvarino, 1983.
1982. Tokioka, 1939.
1983. Pierrot-Bults, 1976.
1984. Pierrot-Bults, 1974.
1985. Grant, 1963 (Chesapeake).
1986. Alvarino, 1961.
1987. Aida, 1897.
1988. Nagasawa & Marumo, 1979.
2005/03/01 JC
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