Institute of Earth Sciences, University of Silesia in Katowice, Sosnowiec, Poland.
Faculty of Computer Science and Materials Science, University of Silesia in Katowice, Chorzów, Poland.
PLoS One. 2020 Dec 9;15(12):e0242924. doi: 10.1371/journal.pone.0242924. eCollection 2020.
The coexistence of sessile, tube-dwelling polychaetes (serpulids) and hydroids, has been investigated. Serpulid tubes bearing traces after hydroids are derived from different stratigraphic intervals spanning the Middle and Upper Jurassic, the rocks of which represent the diverse paleoenvironments of the Polish Basin. Although fossil colonial hydroids classified under the species Protulophila gestroi are a commonly occurring symbiont of these polychaetes during the Late Cretaceous and Cenozoic, they seem to be significantly less frequent during the Jurassic and limited to specific paleoenvironments. The hydroids described here are represented by traces after a thin stolonal network with elongated polyp chambers that open to the outer polychaete tube's surface with small, more or less subcircular apertures. Small chimney-like bulges around openings are an effect of the incorporation of the organism by in vivo embedment (bioclaustration) within the outer layers of the calcareous tube of the serpulid host. Considering the rich collection of well-preserved serpulid tubes (>3000 specimens), the frequency of bioclaustrated hydroids is very low, with an infestation percentage of only 0.6% (20 cases). It has been noticed that only specimens of the genus Propomatoceros from the Upper Bajocian, Lower Bathonian, Middle Bathonian, and Callovian have been found infested. However, the majority of bioclaustrated hydroids (17 cases) have been recorded in the Middle Bathonian serpulid species Propomatoceros lumbricalis coming from a single sampled site. Representatives of other genera are not affected, which is congruent with previous reports indicating that Protulophila gestroi was strongly selective in the choice of its host. A presumably commensal relationship is compared with the recent symbiosis between the hydroids of the genus Proboscidactyla and certain genera of sabellid polychaetes.
共生的固着管栖多毛类环节动物（管居环节动物）和水螅，已经被研究过了。管居环节动物的管状外壳上有海螅痕迹，这些痕迹来自跨越中侏罗世和上侏罗世的不同地层间隔，这些岩石代表了波兰盆地多样化的古环境。虽然在晚白垩世和新生代，分类为 Protulophila gestroi 的化石群体水螅是这些多毛类环节动物的常见共生体，但在侏罗纪它们似乎明显较少，仅限于特定的古环境。本文描述的水螅是通过薄的匍匐网络痕迹代表的，该网络痕迹具有伸长的息肉室，这些息肉室开口通向外部多毛类环节动物管的表面，带有小的、或多或少为近圆形的孔。开口周围的小烟囱状凸起是生物体通过活体包埋（生物隔离）进入管居环节动物宿主的钙质管的外层的结果。考虑到保存完好的管居环节动物的丰富收藏（>3000 个标本），生物隔离的水螅的频率非常低，感染率仅为 0.6%（20 例）。已经注意到，只有来自上巴约阶、下巴通阶、中巴通阶和卡洛夫阶的 Propomatoceros 属的标本才被发现有感染。然而，大多数生物隔离的水螅（17 例）都记录在从中一个采样点采集的中巴通阶管居环节动物物种 Propomatoceros lumbricalis 中。其他属的代表不受影响，这与之前的报告一致，表明 Protulophila gestroi 在选择宿主方面具有很强的选择性。一种假定的共生关系与最近Proboscidactyla 属水螅和某些 Sabellidae 多毛类环节动物属之间的共生关系进行了比较。
