In order to analyze the morphology of the larval scaphognathite, the description of the zoea 1 of 119 Mediterranean species of decapods, belonging to 46 families, has been examined. Eight characters (shape of the distal lobe and number of setae on its internal margin and top, number of setae on the external margin, shape of the proximal zone and relevant number of setae, presence / absence of a naked zone, ratio length scaphognathite / length endites) have been considered. The shape of the proximal zone and the number of setae proved to be the most variable characters but sound to recognize 14 types of scaphognathite. The expected increase of the examined structure complexity does not agree with the systematics of the adult decapods: on the contrary, examining Dendrobranchiata and Caridea, a tendency to the simplification is evident. The infraorders Thalassinidea andAnomura show the greatest variety of types of scaphognathite, while inside the infraorder Brachyura, excluding the Dromiidae, Homolidae, Latreilliidae, and theMajoidea group, the model of scaphognathite is the same. Comparing the types of scaphognathite of anomurans and brachyurans described in the present work with those reported by van Dover et al. (1982), it is possible to note a general congruity with regard to both the types and the families attributable to each type with some differences due to the chosen characters. The scaphognathite in zoea 1 should be used as a valuable taxonomic tool in phylogenetic analyses at genus and species level, but a deeper knowledge of the larval morphology is necessary, the structure should be more carefully described and drawn, paying attention to all the characters here examined, adding information on the type and length of setae and the presence of setolettes.
The larval scaphognathite in Mediterranean Decapoda: a revision
PESSANI, Daniela;
2011-01-01
Abstract
In order to analyze the morphology of the larval scaphognathite, the description of the zoea 1 of 119 Mediterranean species of decapods, belonging to 46 families, has been examined. Eight characters (shape of the distal lobe and number of setae on its internal margin and top, number of setae on the external margin, shape of the proximal zone and relevant number of setae, presence / absence of a naked zone, ratio length scaphognathite / length endites) have been considered. The shape of the proximal zone and the number of setae proved to be the most variable characters but sound to recognize 14 types of scaphognathite. The expected increase of the examined structure complexity does not agree with the systematics of the adult decapods: on the contrary, examining Dendrobranchiata and Caridea, a tendency to the simplification is evident. The infraorders Thalassinidea andAnomura show the greatest variety of types of scaphognathite, while inside the infraorder Brachyura, excluding the Dromiidae, Homolidae, Latreilliidae, and theMajoidea group, the model of scaphognathite is the same. Comparing the types of scaphognathite of anomurans and brachyurans described in the present work with those reported by van Dover et al. (1982), it is possible to note a general congruity with regard to both the types and the families attributable to each type with some differences due to the chosen characters. The scaphognathite in zoea 1 should be used as a valuable taxonomic tool in phylogenetic analyses at genus and species level, but a deeper knowledge of the larval morphology is necessary, the structure should be more carefully described and drawn, paying attention to all the characters here examined, adding information on the type and length of setae and the presence of setolettes.
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