Pherecardia Horst, 1886

Salazar-Vallejo, Sergio I., Piotrowski, Christina N., Gustav, Leslie Harris & Paulay, Gustav, 2025, Revision of Pherecardia Horst 1886 (Annelida Amphinomidae), Zoosystema 47 (28), pp. 691-720 : 695

Genus Pherecardia Horst, 1886

Pherecardia Horst, 1886: 165 ; 1909: 299 (syn.); 1911: 17-21 (syn.). — Fauchald 1977a: 102-103 (key and diagn.).

Eucarunculata Malaquin & Dehorne, 1907: 358 ( type species: E. grubei Malaquin and Dehorne, 1907 , by monotypy).

TYPE SPECIES. — Pherecardia lobata Horst, 1886 , by monotypy; junior synonym of Hermodice striata Kinberg, 1857 .

DIAGNOSIS ( MODIF. AFTER HORST 1886). — Amphinominae with median and lateral antennae and palps. Caruncle large, median ridge heart-shaped with several lateral digitate to foliose lobes. Branchiae present in all segments, bushy. Notochaetae capillaries and aciculars, smooth or serrated (harpoon-chaetae). Neurochaetae aciculars nonfurcate, often distally denticulate, hastate (tips bent).

COMPOSITION

We recognize three species in Pherecardia below: P. striata , P. distincta , and P. maculata . The last is known only from a single small specimen and additional material is necessary to evaluate and better characterize it. The first two species were previously confused and regarded as synonyms but are readily differentiated by color pattern and DNA sequence data ( Fig. 8). Both range across most of the tropical Indo-Pacific to the American coasts. Pherecardia striata is evidently much more common. Perusing images in iNaturalist identified as Pherecardia , we note that only 18 pertain to P. distincta against 153 for P.striata , and one specimen from Timor-Leste was blue, probably after the presence of eggs (accessed 22.VII.2024).

REMARKS

Horst (1886: 165) diagnosed Pherecardia as having a caruncle with “a median, heart-shaped portion (= median ridge), which bears on each side several folded lobes” but he did not compare it against other genera. Pherecardia is similar to Hermodice but can be distinguished by caruncle shape. In Pherecardia the caruncle lateral lobes are separate from each other, often fused to the median ridge, whereas in Hermodice they are fused forming a single plate, and the median ridge is indistinct. Malaquin & Dehorne (1907: 360) differentiated Pherecardia (under the synonym Eucarunculata ) from Hermodice Kinberg, 1857 by indicating that the caruncle lobes “are aligned such that they are convergent anteriorly. This is contrary to the caruncle arrangement in Hermodice , where the lateral lobes are convergent posteriorly along the median ridge.” Because Hermodice is restricted to the Atlantic and Mediterranean, whereas Pherecardia is found in the Indian and Pacific Oceans, there were no comparative illustrations until Hartman (1951: 24) included anterior ends of representatives of each genus. Malaquin & Dehorne (1907) also provided a detailed description of the caruncle and dorsal pigmentation and noted that anterior eyes were larger than posterior eyes.

Amphinomids rarely evert their pharynx fully, as this organ does not need to be completely everted for capturing preyitems, but because of some specimens under stress evert a fairly large portion of the anterior gut, and even if the everted fraction constitutes the whole pharynx, it is rarely exposed for capturing food particles ( Salazar-Vallejo 2023). In Pherecardia , the pharynx exhibits two morphological patterns, but the second may be a fixation artifact. Well-preserved specimens ( Fig. 2A, B) exhibit a roughly spoon-shaped pharynx with granular papillae present on the dorsal depressed region. The mouth opens in the center, with a distal furrow separating lateral cushions comprised of a series of crests running ventrally, which become slightly rugose mid-ventrally. The second pattern was observed in poorly preserved specimens, where the pharynx includes three rings: 1) a short outer yellowish oval ring with a thin mid-dorsal blade ( Fig. 2C, D); 2) a median pale ring with a granulose surface that is 3-4 times longer than the outer ring; and 3) an inner ring with a thinner wall that may be twice as long as the median one. There is one video showing a P. striata capturing a crab, but the pharynx is not shown ( van Antwerp 2013). In Hermodice , the short cylindrical pharynx can be everted for capturing prey items offered by hand ( Kosemen 2013), and in another video of a Chloeia Savigny in Lamarck, 1818, it eats a dying anchovy from the tail by sucking it up, and the pharynx is not exposed at all, although it can be expanded laterally for ingesting the head ( MaverickDiving 2022).

As is the case in some other amphinomids with indefinite growth, the number of segments in Pherecardia specimens is not diagnostic. The following morphological features are not useful for separating species of Pherecardia . The number of lateral lobes in the caruncle, which has been applied to separate species in the past, is problematic as it varies in number and complexity of caruncle lateral lobes due to growth and the caruncle is frequently altered by trauma ( Fig. 3). The fine denticulation of neurochaetae can vary within the same parapodium, however this character must be used with caution because denticles may be damaged or corroded by fixative, resulting in the reduction or loss of subdistal denticles ( de Silva 1961: 171). Consequently, these two features should be avoided to diagnose taxa.