The flagellum of insect antennae consists of annuli and not segments. Is there any relation to the absence of muscle in the flagellum?
Thanks a lot,
Yes, there is a relationship between the different terminology and the different anatomy. Shortly before the middle of the last century was Imms to distinguish, in hexapods, segmented antennae and annualate antennae. The first (segmented a.) feature two groups of primitive hexapods, the Collembola and the Diplura, who also have entognathous mouthparts (Protura also have entognathous mouthparts, but they don't have antennae). Segmented antennae, which are also present in the myriapods (rather similar to primitive hexapods), are characterized by intrinsic muscles in all segments (except the last one). The annulate antennae are typical instead in all other hexapods, more evolved, or insects sensu stricto (from Microcoryphia and Zygentoma - two groups unified in the past under the name Thysanura - to all other more 'recent' insects). These insects also have, all, ectognathous mouthparts. In these insects intrinsic antennal muscles exist only in the first two antennal segments (called scape and pedicel, respectively); all subsequent 'elements' (segments or articles, or 'annuli'), which constitute the flagellum and therefore are also called flagellomeres, are devoid of intrinsic muscles.
Regards,
Rinaldo Nicoli
Hello Dear Wafaa
Arthropod antennae generally extend forward from the head. They are sensory organs, although the exact nature of what they sense and how they sense it is not the same in all groups, nor always clear. Functions may variously include sensing touch, air motion, heat, vibration (sound), and especially olfaction (smell) or gustation (taste). So the insects antena need more sensory organ than muscle. Best regards.
R.F. Chapman "The Insects Structure and Function" shows a segmented antenna of Diplura where muscle attachment is separate for each segment. In contrast the annulated antenna of Orthoptera seems to have muscles only in the scape. So internally the flagellum will consist of haemolypmph, and nerves that run the length of the flagellum and there is no distinct internal structure that differentiates one annulus from another. (That is my guess. It has been 30 years since I had insect anatomy.)
Yes, there is a relationship between the different terminology and the different anatomy. Shortly before the middle of the last century was Imms to distinguish, in hexapods, segmented antennae and annualate antennae. The first (segmented a.) feature two groups of primitive hexapods, the Collembola and the Diplura, who also have entognathous mouthparts (Protura also have entognathous mouthparts, but they don't have antennae). Segmented antennae, which are also present in the myriapods (rather similar to primitive hexapods), are characterized by intrinsic muscles in all segments (except the last one). The annulate antennae are typical instead in all other hexapods, more evolved, or insects sensu stricto (from Microcoryphia and Zygentoma - two groups unified in the past under the name Thysanura - to all other more 'recent' insects). These insects also have, all, ectognathous mouthparts. In these insects intrinsic antennal muscles exist only in the first two antennal segments (called scape and pedicel, respectively); all subsequent 'elements' (segments or articles, or 'annuli'), which constitute the flagellum and therefore are also called flagellomeres, are devoid of intrinsic muscles.
Regards,
Rinaldo Nicoli
Dear Colleagues,
I know that the flagellum has not muscles. I asked this question because someone said to me that no relation between the term annuli and absence of muscles as" taenia" for example, has muscle in each proglottid and still called annulus!!. Their bodies are long, and are divided externally by shallow ring-like constrictions called annuli. So why it called annulus although it contains muscles?
Thanks,
Wafaa
The same word can have multiple meanings and can be used with different meanings (i.e., to indicate different morphological structures) in different branches of the same discipline (and sometimes also in the same branch of the same discipline!),
Rinaldo Nicoli
Dear Wafaa
I agree with Shilpa Haribau Kurane,
Insect antennae contain more sensory organ and their mainly function to detect female location in mating behavior. Commonly male antennae more sensitive and contain more hairs than female (look at male mosquito antennae). I have experience cutting cockroach antenna to detect their function. They can't do more again and spin in their places....
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