Fridericia parathalassia Schmelz, 2002

Chen, Juanjuan, Zhang, Junqian & Xie, Zhicai, 2025, List of species records of enchytraeids (Enchytraeidae, Clitellata, Annelida) in China, Zootaxa 5566 (1), pp. 61-96 : 73

? Fridericia parathalassia Schmelz, 2002 (T)

Fridericia bulbosa Southern, 1907 ; Stephenson 1911.

Fridericia parathalassia Schmelz 2002 , 2003; Schmelz & Collado 2010.

? Fridericia parathalassia Chen 2009 .

Distribution and habitat. Germany, Ireland, Spain, Sweden, Iceland, England, France, Denmark, Bulgaria ( Schmelz 2003); Russia ( Degtyarev et al. 2023). Marine coastal habitats: sea cliffs, sand dunes, upper salt marsh, wrack beds, brackish water ( Schmelz 2003).

Distribution in China. Guizhou Province (Chen 2009).

Remarks. Chen (2009) described “ Fridericia parathalassia ” based on specimens collected from Guizhou Province, the descriptions are translated as follow: medium-sized worms, brownish-yellow when worms alive. Length 9–12 mm, width 0.4–0.5 mm (in vivo). Segments 69–71. Dorsal pore beginning at VII. Chaetal formula 4 - 2–4: 4 - 2–4. Epidermal gland cells brownish, abundant in I–IV, 3–4 rows per segment; cells in other segments indistinct, one row per segment. Clitellum in XII–1/2XIII, girdle-shaped, well-developed, cells in dense rows. Brain ca. 100 μm long and 100–115 μm wide; slightly concave anteriorly, rounded or truncate posteriorly, sides converging anteriad. A pair of oesophageal appendages in IV–VI, with 3–4 branches in the terminal; lumen distinct and tapering to the end. 5 pairs of preclitellar nephridia from 6/7–10/11, postseptale almost as twice as anteseptale, efferent duct rising from postseptale and near the septum. Origin of dorsal blood vessel in XXIV–XXV, blood colourless. Coelomocytes abundant. Mucocytes 35–45 μm in diameter, the outline wave-shaped, without refractile vesicles. Lenticytes small, ca. 5 μm in diameter. Chloragocytes from VI. Chylus cells in XIII–XV, occupying 2 segments. Subneural glands present in XIII–XIV, between two bundles of ventral chaetae. Seminal vesicle small, occupying only one segment (XI). Sperm funnel pear-shaped, tapering to the end and connecting to sperm duct, ca. 165–200 μm long and 100–110 μm wide; collar almost as wide as funnel body. The head of spermatozoa long, the length more than the width of XII. Sperm duct long, ca. 5 μm in diameter, coiled irregular in XII. Male copulatory organ compact, ca. 150 μm long and 50 μm wide. One mature egg at a time. Spermatheca. Ectal duct long, longer than the width in V, ca. 5 μm wide; ectal duct gland absent. Ampulla onion-shaped, without diverticula, ca. 75–100 μm wide. Ental ducts connecting to oesophage separately in V/VI.

Morphologically, Fridericia parathalassia sensu Chen agrees with original description in chaetae, oesophageal appendages, clitellum, subneural glands, long spermatozoa and spermathecae. But it differs significantly from the original description in body size (69–71 vs. 42–49), dorsal blood vessel (XXIV–XXV vs. XX–XXII), preclitellar nephridia (5 vs. 4 pairs) and spermathecal ectal glands (absent vs. present). Furthermore, Fridericia parathalassia always lives in marine coastal habitats, but Chen (2009) described “ Fridericia parathalassia ” based on specimens collected from Guizhou Province, which is far from the sea and does not match the known habitat requirements. The record of “ Fridericia parathalassia ” is probably a misidentification; further work is necessary to establish its true identity.