Collettea Lang 1973
Collettea Lang, 1973 Diagnosis. See Larsen (2011). Remarks. The genus currently comprises 23 species including the one described here, and excludes the three provisional species, “ Collettea sp. A, sp. B, and sp. C”, in Błażewicz-Paszkowycz & Larsen (2005). It is easily recognized by the long cy...
| Main Authors: | , |
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| Format: | Other/Unknown Material |
| Language: | unknown |
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2016
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| Online Access: | https://zenodo.org/record/5673115 https://doi.org/10.5281/zenodo.5673115 |
| Summary: | Collettea Lang, 1973 Diagnosis. See Larsen (2011). Remarks. The genus currently comprises 23 species including the one described here, and excludes the three provisional species, “ Collettea sp. A, sp. B, and sp. C”, in Błażewicz-Paszkowycz & Larsen (2005). It is easily recognized by the long cylindrical pleotelson, and females that lack pleopods. However, the genus as currently composed is probably not monophyletic, as certain species (e.g. C. minima and C. lilliputa) have different mandibular molar shapes, longer uropods, and different cheliped forms (especially the fixed finger dentition). Previous keys (Larsen 2000; Błażewicz-Paszkowycz & Larsen 2005) have used the “pleon size relative to pereon size” as an important character, but we feel it may be misleading because in the new species described here, the pleon (defined as including the pleotelson) of the holotype is as long as the pereon, but one of the paratypes has a pleon that is shorter than the pereon. Measurement of pereon and pleon lengths is compromised by the problems of specimen curvature and degree of relaxation/contraction. It is safely done only with straight specimens (as in Fig. 1) or combined measurements of the individual segments. Non-variable features such as cephalothorax and pleotelson lengths are better characters in this regard. Care must also be given to the presence of mancae in the material; in the manca-II stage of Collettea, pereonite-6 is hardly bigger than one of the pleonites and is easy to overlook this and believe one is measuring the pleon. A few other problems that became apparent when examining Collettea species from the BIOICE material (a large-scale benthic investigation of Iceland waters) were the assessments of the fusion line of antenna article-4 and the number of ventral setae on the cheliped fixed finger - these characters are used to distinguish C. cylindrata (G.O. Sars, 1882) and C. wilsoni Larsen, 1999, for instance. Some specimens lack the fusion line, some have them, and some specimens have a ‘hint’ ... |
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