Amphichaeta
Amphichaeta Tauber, 1879 (ref. ID; 3692, 6913, 7211)
Family Naididae (ref. ID; 6651, 7854)
Family Naididae: Subfamily Chaetogastrinae Sperber, 1948 (ref. ID; 1257, 7211)
ref. ID; 1663
All dorsal setae aciculate. Capilliform seate lacking. (ref. ID; 1663)
ref. ID; 1923
Septa well developed; ventral setae "crotchet", with a swelling, the nodulus; without ventral hair setae. Penis lacking, gonads in some segments between 4 and 8; spermathecae in the same segments as the testes; lateral commisural blood vessels only in the anterior body segments. Without hair setae in dorsal bundles. Segment 3 much longer than the other segments; dorsal setae begin in segment 3. (ref. ID; 1923)
ref. ID; 7211
The genus contained four species only one of which, A. americana Chen, was recorded from North America according to Brinkhurst (1964). The latter was described from material collected at a single site in New Jersey (Chen 1944) and only recently has it been rediscovered and reported from Michigan and South Carolina (Hiltunen and Klemm 1980). A second species, A. leydigii Tauber, is reported as widespread in the United States by these same authors and Loden (1981). We retain the original spelling of the name as reported by Sperber (1948) in place of the alternative A. leydigi. We now have access to material to both species and can also demonstrate that Homochaeta raptisae of Chapman (1981) is cogeneric with the other two. This revision is accepted by P.M. Chapman (personal communication). (ref. ID; 7211)
- Amphichaeta americana Chen, 1944 (ref. ID; 1663, 1861, 1923, 7211)
- Amphichaeta asiatica Liang, 1958 (ref. ID; 6651, 6972)
- Amphichaeta leydigi Tauber, 1879 (ref. ID; 3692, 6651, 7854), leydigii Tauber, 1879 (ref. ID; 1257, 1861, 6913, 7211)
- Amphichaeta magna Sok. (ref. ID; 7211)
- Amphichaeta raptisae (Chapman, 1981) (ref. ID; 6651), (Chapman, 1981) Brinkhurst & Kathman, 1983 (ref. ID; 7211 redescribed paper)
- Amphichaeta sannio Kallstenius, 1892 (ref. ID; 1257, 3692, 6972)
Amphichaeta americana Chen, 1944 (ref. ID; 1663, 1861, 1923, 7211)
Descriptions
Segment III two or three times as long as other anterior segment. Rare species. (ref. ID; 1663)
This species feeds on benthic diatoms. (ref. ID; 1861)
Remarks
This species appears to have been accurately described by Chen (1944) but our specimens from South Carolina have up to seen setae in the dorsal bundles of segment III instead of three or four mentioned by Chen. The distinctive gap in the setal bundles between segments III and IV is more pronounced than in other Amphichaeta species; also the teeth of the setae are more clearly unequal, the posterior ones having conspicuously long upper teeth. The short body ends in a few segments that rapidly diminish in diameter, leaving the characteristically long distal part of the setae beyond the nodulus projecting markedly (in preserved specimens). The vasa deferentia enter the prostate-covered atria apically, in contrast to A. leydigii. (ref. ID; 7211)
Material examined
Keowee Reservoir, South Carolina, 21 specimens August 1977 (Nichols 1981). (ref. ID; 7211)
Remarks
A. asiatica Liang, 1958 is close to the poorly known A. sannio Kallstenius, 1892. Liang (1958) stated that the European species was smaller, with shorter, thinner chaetae lacking the nodulus, and only the left branch of the ventral vessel loops into the prostomium. Liang also stated that the needle teeth are short and equally long in A. sannio, but Sperber (1948) claimed that the upper could be 3 versus 2 µm for the lower in the median chaetae of the bundles, but that in more lateral chaetae the teeth could be "more equal" in length. In the original (translated abstract) description of A. asiatica, the teeth of the dorsal chaetae were described as "usually more equal in length" than the ventrals, the ventrals of II with teeth equally long, but those on the following segments with the upper tooth longer than the lower. The only illustration of chaetae of A. sannio shows no nodulus, unlike other species attributed the genus, but Sperber (1948) did not mention this peculiarity. She did state that she could confirm all but some specific aspects of the original description, however. Brinkhurst and Jamieson (1971) considered A. asiatica to be a possible synonym of A. sannio, and the matter rests there until the two can be compared directly. (ref. ID; 6972)
Amphichaeta leydigi Tauber, 1879 (ref. ID; 3692, 6651, 7854), leydigii Tauber, 1879 (ref. ID; 1257, 1861, 6913, 7211)
Descriptions
This species feeds on benthic diatoms. (ref. ID; 1861)
Dorsal setae begin in III, bifid crotchets only, usually five per bundle. Ventral setae of II-III rarely five, all others two or three, rarely four, per bundle. Anterior setae with upper tooth a little shorter and a litle thinner than the lower, both teeth curved. Posteriorly upper tooth becomes straighter and as long as or longer than the lower. The setae of II and III lie close together with a pronounced gap separating those of III and IV. (ref. ID; 7211)
Remarks
The number of setae in these specimens is the same as that cited by Brinkhurst and Jamieson (1971), but the key in that publication could seem to suggest that the anterior setae have upper teeth that are as long as or longer than the lower, while the posterior setae have teeth equally long. In fact the upper setal teeth become progressively longer posteriad, which also occurs in A. americana, but they never achieve the considerable length seen in that species despite some intraspecific variation. (ref. ID; 7211)
Material examined
North end of Mercer Island, Lake Washington, Seattle, Washington, 1.5-10 m depth, more than 100 specimens. March and October 1982. E.V.S. Consultants collection (Kathman 1983). (ref. ID; 7211)
Amphichaeta raptisae (Chapman, 1981) (ref. ID; 6651), (Chapman, 1981) Brinkhurst & Kathman, 1983 (ref. ID; 7211 redescribed paper)
Descriptions
Dorsal setae from III, five per bundle, ventrals II-III four per bundle, others two or three per bundle. Anterior setae with upper tooth projecting straihgt in line with shaft, lower tooth somewhat recurved, both teeth short but about equally long; posterior setae with upper tooth slightly curved and longer than the lower. In some setae a single intermediate tooth is visible, but if cannot always be detected even with oil immersion lenses. (ref. ID; 7211)
Remarks
The specimens from Steveston have been compare with specimens from the type series collected futher upstream in the Fraser River estuary. The Stevenston specimens clearly show the ventral setal bundles of II with dorsals and ventrals in III, and the distinctive gap between setae of III and IV. The intermediate tooth very difficult to see, and while it does not appear restricted to dorsal anterior setae, as suggested by Chapman (1981), it is impossible to tell from light microscopy if it is present in some or all setae.
Amphicaeta raptisae species differs from A. leydigii from Lake Washington mainly by the possession of this intermediate tooth in the bifid setae. Further study of fresh material will be required to establish if other differences exist. The distinctions among the species based on relative lengths of the setal teeth alone seem quite good for A. magna (with short upper teeth), A. americana (with long upper teeth), and A. raptisae (with an intermediate tooth). In all species the posterior setae have longer upper teeth than those of anterior setae. Amphichaeta leydigii has anterior setae with the upper teeth very slightly shorter than the lower but they are slightly longer than the lower posteriorly, although individuals may vary, as noted for A. magna Sok. Amphichaeta sannio Kall. (from European brackish water) appear close to A. leydigii. Sperber (1948) indicates considerable confusion about the identity of A. sannio, which has been regarded as a synonym of A. leydigii by some. In a recent European account (Kasprzak 1981) only slight differences in setal form between these two species are reported. (ref. ID; 7211)
Material examined
Tilbury Slough, Lower Fraser River, five specimens from type series, P.M. Chapman collection; many specimens Fraser River estuary at Steveston, British Columbia, 13 December 1979, Dobrocky Seatech Lt. collection, catalogue No.79-0102. (ref. ID; 7211)