A propos d'une forme stomatoporienne typique,Stomatopora gingrinaJullien, 1882 (Bryozoaires Cyclostomes), et de son gonzoïde

Abstract

Description of a typical uniserial form of Stomatopora referred to the recent species S. gingrina Jullien, 1882. Abundant material including fertile specimens was collected in bathial depths (600–1400 m) in the Atlantic, mainly North West of Spain. The budding pattern is that found in the fossil species group dichotoma-dichotomoides-bifurca as defined by Illies (1971); lateral peristomial budding occurs under particular topographical conditions. The gonozoid, observed here for the first time in a strictly uniserial species, has the shape of an inflated sac laterally adnate to the upper part of an autozoidal peristome. The gonozoid differs from the general type because it does not present a narrow proximal part. This latter feature is in correlation with its peristomial origin. The ooeciostome is a short distal tube opening upward. According to the coefficient of variation within four series of measurements, three parameters—peristomes diameter, length of the autozoids adnate portion, width of the ancestrula primary disc—are fairly constant and can be used as taxonomical characters. Some interesting morphological features of the Stomatopora here studied can be explained by ecological conditions. The zoarial shape (dispersion of zoidal units by linear branching) and the great length of the peristomes appear to be morphological responses to the deep water habitat which is characterized by small water renewal, high degree of fine sedimentation and scarcity of available food.