A comparison of the labrum-paragnath complex in five species of calanoid copepods fileset

Although some information is available on how calanoid copepods collect and handle food, there is very little information on the labrum and paragnaths, structures that are the last to receive food before trituration and ingestion. Five species were used to examine the nature of and differences between the labrum-paragnath complex, species with a variety of feeding modes ranging from detritivore to carnivore. The nature of the complex ranged from very simple in Eucalanus bungii bungii Johnson, 1938, to the heavily sclerotized labrum and paragnaths of the carnivore Paraeuchaeta elongata (Esterly, 1913) with its specialized anterior labral lobe. The labrum, which provides a semi-enclosed space for trituration by the mandible gnathobases, is hood shape while the columnar-shaped paragnaths, which hold and help move food towards the mandible gnathobases, contain setule and spicule armature elements. Not only the shape of the complex, but also its orientation are suggested to play roles in dictating dietary choices. The range of structures, from the simple complex of Eucalanus bungii bungii to the beak like complex of Heterorhabdus tanneri (Claus, 1863), along with its claw-like gnathobase armature, provide an indication of the morphological diversity found in the labrum-paragnath complex of calanoid copepods.

尽管有关桡足类挠足动物如何收集和处理食物的信息已有一些，但对于位于咀嚼和摄入前的最后一道工序——上唇和副上颚的结构，却鲜有研究。本研究选取了五种物种，以探究上唇-副上颚复合体的性质及其在不同摄食模式（从腐食性到肉食性）物种间的差异。该复合体的性质从欧卡兰属（Eucalanus bungii bungii Johnson，1938）中极为简单的结构，到肉食性物种长足副上颚（Paraeuchaeta elongata Esterly，1913）中高度钙化的上唇和副上颚，以及其特化的前唇叶，呈现出极大的变化。上唇，为颚下基部的咀嚼提供一个半封闭的空间，其形状为罩状；而柱状副上颚，则用于固定并帮助食物移动至颚下基部的位置，其表面含有刚毛和针状支架元素。不仅该复合体的形状，其方位亦被认为在决定食物选择上发挥着作用。从欧卡兰属的简单复合体到异杆毛属（Heterorhabdus tanneri Claus，1863）的喙状复合体，以及其类似爪子的颚下基部支架，都揭示了桡足类挠足动物上唇-副上颚复合体中存在的形态多样性。