Bibliographic record
Abstract
Genus Themisto Guérin 1825 Remarks This genus has provided much taxonomic confusion in the past. Its status has been in question being known alternately as Euthemisto or Parathemisto, sometimes with subgenera. Bowman et al. (1982) restored the genus Themisto, which up until that time was considered a junior homonym of the nudibranch Themisto Oken, 1815; a work rejected for nomenclatural purposes by the ICZN (1956). The uncertainty of the generic status combined with several illdefined species, subspecies and varieties has made specific determination very difficult, despite the efforts of Bowman (1960), Sheader and Evans (1974) and Schneppenheim and WeigmannHaass (1986). Vinogradov et al. (1982) recognise six species, but Schneppenheim and WeigmannHaass (1986) demonstrated that northern hemisphere material, previously identified with T. gaudichaudii Guérin, 1825, is a separate species, T. compressa Goës, 1865. In view of the past confusion, and recent studies by Schneppenheim and WeigmannHaass (1986), a new key to species is provided to assist future workers. The holotype of T. gaudichaudii was discovered recently in the GuérinMéneville collection (No. 438), in the ANSP (Zeidler 1997). The correct citation for the original description of this species has been confused in the past with some authors citing Guérin, 1828 (eg. Schneppenheim & WeigmannHaass 1986; Spamer & Bogan 1992, 1994). This has arisen because, although the genus and species was first described in 1825, Guérin (1828) more or less repeated his description in a separate memoir introducing them as new, and providing figures of the type. All species of Themisto are mainly freeswimming, and can occur in large numbers, particularly in colder waters where, like krill, they play a significant role as food for planktonfeeding predators. Although considered mainly freeliving, species of Themisto are known to be associated with medusae and salps (Madin & Harbison 1977; Laval 1980), and specimens of T. australis have been collected from Salpa fusiformis from Tasmanian waters. Additional biological and ecological information is given by the following; Bary (1959), Kane (1963), Siegfried (1965), Gray (1967), Evans (1968), Semenova (1974), Sheader (1975, 1977, 1981, 1990), Sheader and Evans (1975), Williams and Robins (1981), Bowman et al. (1982), Hiroki (1988), Corey (1990), Semura et al. (1991), Percy (1993), Colombo and Vinas (1994), Koszteyn et al. (1995), Condon and Norman (1999) and Vinogradov (1999b). Themisto has a bipolar distribution with species restricted to the colder waters of the Arctic and Antarctic regions and occasionally venturing into cooltemperature waters. Species: as in the following key. Key to the species of the genus Themisto 1. Pereopod 5 not longer than P6 or P7 ........................................................................... 2 Pereopod 5 much longer than P6 or P7 ........................................................................ 5 2. Maxilliped without row of setae on distal margin of basal plate (arctic and subarctic of Atlantic) ............................................................................. T. abyssorum (Boeck, 1871) Maxilliped with row of setae on distal margin of basal plate ..................................... 3 3. Pereopods 5 & 6; dactylus smooth. Antenna 1 of female hooked, stout (colder waters of Australia and New Zealand) T. australis (Stebbing, 1888) Pereopods 5 & 6; dactylus with setae at base. Antennae 1 of female straight, tapering (North Pacific) ............................................................................................................. 4 4. Antennae 2 of females longer than A1. Adult females reach 9–17 mm in length. Pereopod 3 with 6–8 (usually 7) robust setae on posterior margin of carpus ...................... .......................................................................................... T. japonica (Bovallius, 1887) Antennae 2 of females equal in length to A1. Adult females reach 5–9 mm in length. Pereopod 3 with 3–5 (usually 4) robust setae on posterior margin of carpus ................ ........................................................................................... T. pacifica (Stebbing, 1888) 5. Pereopod 7 usually longer than P6, but shorter than P5. Gnathopod 2; merus with relatively straight distal margin,anterodistal corner produced into small tooth(North Atlantic) ................................................................................................. T. compressa Goës, 1865 Pereopod 6 & 7 subequal in length. Gnathopod 2; merus with rounded distal margin 6 6. Pereopods 3–7; dactylus with setae on basal part (arctic and subarctic) ........................ ....................................................................... T. libellula (Lichtenstein in Mandt, 1822) Pereopods 3–7; dactylus smooth (colder waters of southern oceans) ............................. ......................................................................................... T. gaudichaudii Guérin, 1825
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.019 | 0.003 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".