Salinity tolerance in the early larval stages of Carcinus maenas (Decapoda, Brachyura), a recent invader of the Bras d'Or lakes, Nova Scotia, Canada
Bibliographic record
Abstract
The European green crab, Carcinus maenas, is an extremely successful species worldwide. C. maenas was first recorded in Nova Scotia in 1953, and by the 1990s it was found in the Bras d'Or Lakes in Cape Breton. Adults of C. maenas can tolerate salinities as low as 4. However, their larvae are not known to survive in salinities below 20 in their native range. High abundances of adult and juvenile C. maenas, as well as zoea-1 larvae and megalopae, are recorded in the Bras d'Or Lakes, where surface salinity may rarely exceed 20. It is possible that the early zoeal stages are more tolerant of lower salinities than those from their native habitat. Alternatively, they may have developed a tolerance for short-term exposure to low salinities. To examine the long-term tolerance of early zoeal stages (zoea-1 and zoea-2) of C. maenas to different salinities, newly released larvae from females from the Bras d'Or Lakes were individually reared in the laboratory at four practical salinities (14, 17, 20, 26). Larval survival decreased sharply and larvae did not develop past zoea-1 in salinities of 14 and 17, while larvae reared at a salinity of 20 did not survive past zoea-2 and larvae reared at a salinity of 26 completed development to the megalopa stage. Variation in larval survival among females was greatest at 26 and decreased with decreasing salinity. To examine the short-term tolerance of early zoeae, newly released zoeae were initially placed in a salinity of 14 for 1 day or 20 for 3 days, before being transferred to a salinity of 26. Larval survival did not increase and development did not resume after larvae were transferred to the higher salinity. These results suggest that early larval stages of C. maenas from the Bras d'Or Lakes are not adapted to either long, or short-term exposures to the low salinities typical of the surface waters of the Lakes. It is possible that these larvae may be able to tolerate exposure to low salinity water for shorter periods than those examined, or that they are behaviourally avoiding waters of low salinity in order to survive in this invaded habitat. Le crabe vert europeen, Carcinus maenas est une espece extremement repandue dans le monde. C. maenas fut pour la premiere fois signale de Nouvelle-Ecosse en 1953, et dans les annees 1990, retrouve dans les lacs du Bras d'Or dans l'ile du Cap-Breton. Les adultes de C. maenas peuvent tolerer des salinites aussi faibles que 4. Cependant, leurs larves ne sont pas connues pour survivre a des salinites inferieures a 20 dans leur milieu d'origine. Des abondances elevees de C. maenas adultes et juveniles, ainsi que de larves zoes 1 et de megalopes, ont ete observees dans les lacs du Bras d'Or, ou la salinite de surface depasse rarement 20. Il est possible que les premiers stades zoes soient plus tolerants a des salinites inferieures a celles de leur habitat d'origine. Ou bien, il se peut qu'ils aient developpe une tolerance a de courtes expositions a de faibles salinites. Afin d'examiner la tolerance a long terme des premiers stades zoes (zoe 1 et zoe 2) de C. maenas a differentes salinites, des larves nouvellement liberees par des femelles des lacs du Bras d'Or ont ete elevees individuellement au laboratoire a quatre differentes salinites (14, 17, 20 et 26). La survie larvaire diminuait rapidement et les larves ne se sont pas developpees apres le stade zoe 1 aux salinites 14 et 17, tandis que celles elevees a une salinite de 20 n'ont pas survecu au stade zoe 2 et que les larves placees a une salinite de 26 ont effectue leur developpement jusqu'au stade megalope. La variation de la survie chez les femelles etait la plus grande a 26 et diminuait a salinite decroissante. Afin d'examiner la tolerance a court terme des premiers stades zoes, des zoes nouvellement ecloses ont ete placees tout d'abord a une salinite de 14 pendant une journee ou a 20 pendant trois jours, avant d'etre transferees a une salinite de 26. La survie larvaire n'a pas augmente et le developpement n'a pas repris apres que les larves aient ete transferees a une salinite plus elevee. Ces resultats suggerent que les premiers stades larvaires de C. maenas des lacs du Bras d'Or ne sont pas adaptes a l'exposition a court comme a moyen terme aux salinites basses typiques des eaux de surface de ces lacs. Il est possible que ces larves puissent tolerer une exposition a une eau de faible salinite pour des periodes plus courtes que celles etudiees ici, ou qu'elles soient capables d'eviter les eaux de faible salinite par un comportement adapte, de facon a survivre dans cet habitat.
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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 | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
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".