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The anterior of the two or three main divisions of the body of certain invertebrates, especially the cephalothorax of an arachnid.

[pro- + Greek sōma, body; see teuə- in Indo-European roots.]

pro·so′mal adj.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.


(Zoology) relating to a prosoma
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014
References in periodicals archive ?
(A) Habitus, lateral view; (B) Prosomal end and urosome, ventral view; (C) Antenna; (D) Mandibular gnathobase; (E) Mandibular palp; (F) Maxilla; (G) Leg 1; (H) Leg 2; (1) Leg 3; (J) Leg 4.
Before experimentation, juveniles of similar size with prosomal width of 14-17 mm were maintained in a sheltered indoor pool and fed with an equally proportioned mixture of all the experimental diets once daily (17:00 h) ad libitum (about 3%-4% body weight) until molting.
Sperm was collected by making 2-3-cm cuts into the soft part of the prosomal ventral cuticle from the base of the appendages toward the lateral margin.
Mucor fragilis on Latrodectus geometricus' prosomal cuticle around cervical grooves and eyes; subject imaged 3 days after inoculation.
The calanoids, hereafter referred to as copepods, were further divided by size: 1) small copepods (<2 mm prosomal length [PL]); and 2) large copepods (>2 mm PL).
Harvestmen (Opiliones) have a distinctive pair of prosomal exocrine glands opening to the surface via ozopores usually placed in the vicinity of the second leg pair.
The large prosomal nerve mass that supplies innervation to the musculature of the legs and fangs is located in the anterio-ventral region of the cephalothorax (Foelix 1996; Punzo & Punzo 2002) and damage to this nerve mass coupled with the loss of hemolymph may have accounted for the collapse of the spider.
The largest 14 animals (prosomal width: 18-23 cm) were assigned to the outdoor unrestrained (OU) group, and they were placed in tanks outside the University of New Hampshire Jackson Estuarine Laboratory (JEL).
The table should read as follows: Table 3 The number of individuals sampled (n), coefficient values (a, [log.sub.e](b)), standard errors for values (SE[a], SE[[log.sub.e](b)]), and correlation coefficient ([r.sub.2]) of the relationship between prosomal width and weight for horseshoe crabs (Limulus polyphemus), loge(Wt)=[log.sub.e] (PW) x a + [log.sub.e](b).
(2005) reported mean prosomal width (PW) for adult females in Pleasant Bay, Massachusetts was 230 ram.
Ventral prosomal complex of male with coxae of legs II and IV meeting in the midline, but coxae I and III not so (Fig.
The sex, prosomal width (PW; to the nearest 1 mm), and weight (to the nearest 10 g) were recorded from a sample of individuals that were collected from the vicinity of each breeding beach.