Acline see orthocline

aclitellate a. [L. a, without; clitella, packsaddle] (ANN: Oli-gochaeta) Lacking a clitellum; an adult earthworm, but still without a clitellar tumescence of the epidermis; the second growth stage.

acme n. [Gr. akme, point] 1. The highest point. 2. That period of greatest development in the phylogenetic history of a group of organisms.

Acoelomata n. [Gr. a, without; koilos, hollow] A coined term denoting those lower phyla of zoological classification that lack a body cavity or coelom as Cnidaria (=Coelenterata), Nemertea, Platyhelminthes, Porifera, or Ctenophora.

acoelomate, acelomate a. [Gr. a, without; koilos, hollow] Refers to any Metazoa with no internal cavities in the body other than the lumen of the gut. acoelous a.

acone eye (ARTHRO: Insecta) A condition (possibly primitive) of a compound eye in which the ommatidium is lacking a crystalline cone, but is modified in the form of elongated transparent bodies called Semper cells. see pseudocone, eucone, exocone.

acontioids n.pl. [Gr. akon, dart; eidos, shape] (CNID: Antho-zoa) Simple or branched adhesive threads of tube anemones situated on the lower portion of the mesenteries.

acontium n.; pl. -ia [Gr. akon, dart; ium, nature of] (CNID: Anthozoa) An elongate, hollow, nematocyst-studded thread of sea anemones.

acoustic a. [Gr. akouein, to hear] Auditory; pertaining to the organs or sense of hearing, or produce sound such as a stridulatory organ.

acquired a. [L. acquirere, to seek] 1. Pertaining to being developed as a result of environmental effects; noninheritable. 2. Resulting from experience or learning.

acquired character A trait or somatic modification that originates during the life of an organism as the result of an environmental or functional cause.

acraein n. [Gr. akrasia, bad mixture] (ARTHRO: Insecta) In Lepidoptera, a secretion of certain butterflies of protective or distasteful function.

Acraspeda n. [Gr. akraspedos, without fringes] (CNID: Hydro-

zoa) In former classifications, a group of jellyfish having a medusa without a velum.

acraspedote a. [Gr. a, without; kraspedon, border] 1. (CNID: Hydrozoa) Refers to medusae without a velum. 2. (PLATY: Cestoda) Pertaining to tapeworm segments that do not overlap.

acrembolic proboscis (MOLL) Having a completely invaginable proboscis. see pleurembolic proboscis.

acridophagus n. [Gr. akridion, locust, grasshopper; phagein, to eat] (ARTHRO: Insecta) The act of preying and feeding on members of the Acrididea.

acroblast n. [Gr. akros, tip; blastos, bud] In spermatogenesis, Golgi material giving rise to an acrosome.

acrocentric a. [Gr. akros, tip; kentron, center] Pertaining to chromosomes with the centromere at or near one of the ends; rod-shaped chromosomes. see telocentric.

acrocercus see cercus acrocyst n. [Gr. akros, tip; kystis, sac] (CNID: Hydrozoa) A chitinous sac containing a planula in which development is completed; may protrude from the gonangium.

acrodendrophily a. [Gr. akros, tip; dendron, tree; philein, to love] Inhabiting the tree-tops.

acron n. [Gr. akros, tip] 1. (ARTHRO) The anterior unseg-mented, or indistinguishably fused, body segments. a. In Crustacea, ophthalmic somite; presegmental region. b. In Insecta, the prostomium. 2. (MOLL) The prostomal region of trochophore larva.

acronematic a. [Gr. akros, tip; nema, thread] Referring to smooth, whip-like flagella.

acroneme n. [Gr. akros, tip; nema, thread] The slender section of a flagellum.

acroparia n.; pl. -ae [Gr. akros, tip; pareion, cheek] (ARTHRO: Insecta) In Coleoptera, the anterior part of the paria bearing the bristles of scarabaeoid larvae.

acroperiphallus n.; pl. -li [Gr. akros, tip; peri, around; phal-

los, penis] (ARTHRO: Insecta) In Protura, the distal part of the periphallus, sometimes retractable into basiperiphallus.

acrophilous a. [Gr. akros, tip; philein, to love] Preferring regions of high altitude.

acrorhagus n.; pl. -gi [Gr. akros, tip; rhax, berry] (CNID: An-thozoa) A marginal tubercle of sea anemones containing specialized nematocysts.

acroscopic a. [Gr. akros, tip; skopein, to view] Looking towards the apex. see basiscopic.

acrosome n. [Gr. akros, tip; soma, body] A cap-like structure investing the front part of the sperm head allowing penetration of the cover of the egg cell; formed from Golgi material.

acrosternite n. [Gr. akros, tip; sternon, chest] (ARTHRO: Insecta) That part of the narrow marginal flange anterior to the antecosta of a definitive sternal plate, including the preceding primary intersegmental sclerotization; normally found on abdominal sterna, but absent on thoracic sterna.

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