Accessory genitalia see accessory appendages

accessory glands (ARTHRO: Insecta) 1. A pair of glands opening primarily on the venter or the eighth or ninth abdominal segment of females that secrete an adhesive substance or material forming a cover or case (ootheca) for the eggs. 2. In males, secretion glands opening into the ejaculatory duct.

accessory lamellae (MOLL: Bivalvia) In Pholadinae, accessory periostracal coverings or shelly plates along the dorsal margin, over the anteroventral pedal gape, or along the posteroventral margin encircling the siphons.

accessory lobes (ARTHRO) Ventral lobes of the protocerebrum.

accessory nidamental gland (MOLL: Cephalopoda) Small paired glands subordinate to the nidamental gland.

accessory pigment cells (ARTHRO: Insecta) As many as twenty-four cells that surround the retinulae of a compound eye; in superposition eyes the pigment granules assume different positions in light and darkness; also known as secondary pigment cells, secondary iris cells, iris pigment cells and outer pigment cells.

accessory pulsatile organs (ARTHRO) Pulsating structures connected with the hemocoel that are concerned with maintaining a circulation through the appendages, but pulsating independently from the heart.

accessory sac (platy: Cestoda) A sac in the proglottid wall that opens into the genital atrium.

accessory spicule (PORIF) A category of megasclere, supplemental to the primary skeleton, may be located anywhere.

accessory stylets (nemer) Replacement stylets that are stored in reserve stylet sacs or pouches.

accessory subcoastal vein (ARTHRO: Insecta) In Perlidae, the vein given off from the subcosta, branching toward the apex of the wing.

accessory testis (ARTHRO: Insecta) In Coleoptera, the coiled middle section of the vas deferens serving as a reservoir for mature sperm.

accidental evolution A condition that occurs as a consequence of mutation, but does not appear to improve survival value.

accidental host A host in which a pathogenic parasite is not commonly found.

accidental myiasis (ARTHRO: Insecta) In Diptera, the presence within a host of a fly larva that is not normally parasitic; pseudomyiasis.

accidental parasite A parasite in other than its normal host; an incidental parasite.

accidental transport Unintentional movement of a pathogen from one location to another by an animal not normally associated with the parasite or disease. see phoresis.

acclimation n. [L. ad, to; Gr. klima, climate] The habituation of an organism to a foreign or different climate or environment; acclimatization.

acclivous a. [L. acclivis, ascending] Pertaining to an upward slope. see declivous.

accretion n. [L. accrescere, to increase] Growth or increase by external addition. see intussusception.

acelomate see acoelomate acentric a. [Gr. a, without; kentrol, center] Pertaining to not being centered; lacking a centromere when referring to a chromosome or chromosome fragment.

acentric inversion An inversion of any part of the chromosome not involving the centromere.

Acephala (MOLL) Former name for Class Bivalvia.

acephalocyst n. [Gr. a, without; kephale, head; kystis, bladder] (PLATY: Cestoda) A hydatid larval stage; bladderworm; cysticercus.

acephalous a. [Gr. a, without; kephale, head] (ARTHRO: In-secta) Pertains to the absence of any structure comparable to a head, as in certain dipteran larvae; acephalic. see eucephalous, hemicephalous.

acerata n. [Gr. a, without; keratos, horn] 1. Without true antennae. 2. (ARTHRO) In former classifications, the name Acerata comprised a class combining Merostomata and Arachnida.

acerate a. [L. acer, sharp] Of or pertaining to needle-shaped; acerose; acicular.

acerose a. [L. acer, sharp] Having a sharp, rigid point; acerate; acicular.

acerous a. [Gr. a, without; keras, horn] Lacking horns, antennae or tentacles.

acervate a. [L. acervare, to heap] Pertaining to heaped or growing in heaps or clusters. see coacervate.

acervuline a. [L. acervare, to heap] Resembling small heaps.

acescence n. [L. acesceres, to turn sour] Acetic acid fermentation.

acetabular caps (ARTHRO: Insecta) The coxal cavity of Hemiptera.

acetabuliform a. [L. acetabulum, cup; forma, shape] Resembling the shape of a shallow cup or saucer.

acetabulum n.; pl. -la [L. acetabulum, cup] 1. A cup-shaped socket or cavity. 2. (ANN: Hirudinoidea) In leeches, the large posterior sucker. 3. (ARTHRO: Chelicerata) In Acari, the genital sucker. 4. (ARTHRO: Insecta) a. Any cavity into which an appendage is articulated; the coxal cavity. b. The conical cavity at the anterior of some larvae; in Diptera, the cavity in the sucking mouth. c. In dytiscid water beetles, stalked cuplets or sucker discs on the anterior tarsi, in some, also the second tarsi, thought to act as adhesive organs during copulation; a pallette. 5. (ECHINOD: Echin-oidea) The cavity located on the proximal end of a spine. 6. (MOLL: Cephalopoda) The sucker on the arm. 7. (PLATY: Cestoda) The sucker on the scolex. 8. (PLATY: Trematoda) The ventral sucker.

achaetous, achetous a. [Gr. a, without; chaite, hair] Without setae, bristles, or chaetae.

achatine, achatinus a. [L. achates, agate] Pertaining to lines resembling those of an agate; in bands of more or less concentric circles.

achelate a. [Gr. a, without; chele, claw] Lacking pincherlike organs or claws.

achilary a. [Gr. a, without; cheilos, lip] Lacking a lip.

achlamydate a. [Gr. a, without; chlamys, mantle] Lacking a mantle.

achroacyte n. [Gr. a, without; chroa, colored; kytos, container] A colorless cell; a lymphocyte.

achroglobin n. [Gr. a, without; chroa, colored; L. globus, sphere] (MOLL) A colorless respiratory pigment.

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