Cryptonome elongata ( Treadwell, 1931 ), 2024

Tovar-Hernández, María Ana, González-Vallejo, Norma Emilia & Salazar-Vallejo, Sergio I., 2024, Cryptonome beatrizae n. sp., from drifting wood in Western Mexico, with remarks on Pareurythoe Gustafson, 1930 (Annelida, Amphinomidae), Zootaxa 5424 (5), pp. 535-553 : 545-548

Cryptonome elongata ( Treadwell, 1931) new combination

Figs 8 and 9

Hipponoe elongata Treadwell, 1931: 3–4 , Figs 10 –12.

Pareurythoe elongata : Hartman 1951: 28 (n. comb.).

? Pareurythoe elongata : Hartman 1956: 274.

Diagnosis. Cryptonome with small eyes, oval; median antenna reduced; caruncle straight; first branchiae with 5–6 filaments; parapodial cirri smooth, tapered.

Type material. Caribbean Sea. Holotype ( AMNH 2067 ), Puerto Rico, unspecified locality or substrate, Jun. 1915, R.W. Miner, legit.

Description. Holotype (AMNH 2067) complete, mature female, twisted ( Fig. 8A), almost breaking in two pieces, several parapodia previously removed ( Fig. 8B), 11 placed in small vial: right parapodia 1–4, 36–39, branchiae from chaetigers 10, 43, neurochaetae chaetigers 9–12; colorless, about 150 mm long, 8 mm wide (widest region), 134 chaetigers.

Body tapered in both body ends, depressed towards anterior and posterior end, most segments swollen; body wall damaged, broken in some median segments, pale throughout body. Parapodial cirri, branchiae and chaetae colorless.

Prostomium rounded anteriorly, tapered posteriorly, roughly triangular ( Fig. 8C). Anterior prostomial lobe rounded, larger than posterior one, transverse separation indistinct, two curved depressions ahead of eyes not connected medially; anterior prostomial lobe with short, conical lateral antennae, directed laterally, not reaching prostomial margin, and palps, slightly shorter than lateral antennae. Posterior prostomial lobe with four blackish eyes, oval, posterior eyes slightly larger than anterior ones; median antenna very thin, short, about half as long as laterals, inserted behind posterior eyes. Caruncle small, straight, as long as chaetiger 1.

Peristomium reduced to two fusiform, low, longitudinal medially separated cushions; mouth between chaetigers 2–3 ( Fig. 8D).

Parapodia all biramous, larger anteriorly, progressively smaller along body. Notopodia and neuropodia blunt, notochaetal lobe low, neurochaetal lobe larger, projected laterally.Cirri tapered. Dorsal cirri massive, with large cirrophore along body, especially along anterior chaetigers ( Fig. 8A, B), cirrostyle progressively longer to median segments, tapered, non-articulate ( Fig. 8D), shorter posteriorly. Ventral cirri very short along body, about as long as wide.

Branchiae from chaetiger 3, continued along body, missing in last two chaetigers. Branchial filaments larger, more abundant along chaetigers 10–60, with two stems along anterior chaetigers, with 10–12 basal stems in 2–3 rows, with over 110 filaments by chaetiger 30, with about 20 by chaetiger 125. Branchial filaments digitate or tapered, of similar thickness along body.

Chaetae damaged, partially broken, others eroded by acidic preservative. Anterior and posterior chaetigers with abundant notochaetae, most thin capillaries and some with a subdistal spur and a row of spines continued almost to chaetal tip. Anterior neurochaetae furcates, longest tines 5–10 times longer than shortest ones ( Fig. 9C); by chaetiger 30 furcates have very small spurs, longest tines 30–60 times longer than shortest ones ( Fig. 8F). All acicula spoon-shaped ( Fig. 9G), up to eight in notopodia, about five in neuropodia.

Posterior end tapered; pygidium with anus terminal, with a distal semicircular lobe; no anal cirri ( Fig. 8E). Oocytes in coelom from anterior chaetigers; oocytes round, granulose, about 80 μm in diameter ( Fig. 9D, inset).

One paratype regenerating 11 anterior segments.

Remarks. Hipponoe elongata Treadwell, 1931 , described from Puerto Rico, has a complex taxonomic history. It was included in Hipponoe Audouin & Milne-Edwards, 1830 because no caruncle was observed by Treadwell (1931: 3), and it was regarded as different from H. gaudichaudi Audouin & Milne-Edwards, 1830 because no neurohooks were present. Hartman (1951: 28) transferred H. elongata to Pareurythoe because she thought “the caruncle is withdrawn or retracted” and then modified the diagnosis for the species. However, after the study of the large type specimen (185 mm long), she changed her mind indicating a question mark before the genus name, and because she noted the unusual type of caruncle present ( Hartman 1956: 274): the caruncle “has the form of a broadly divergent V with spreading branches and its base slightly prolonged so as to lie at the middorsum of the first setigerous segment. The distal ends of the caruncle extend forward and nearly conceal the two pairs of large dark eyes.” Consequently, this species cannot be congeneric in Pareurythoe , after the below diagnosis, which indicates its caruncle is a narrow lobe reaching up to chaetiger 3. Kudenov (1994: 205) indicated “ H. elongata is most certainly a Linopherus -like species.” However, Linopherus de Quatrefages, 1866 has a very small caruncle, not concealing eyes nor prostomium, whereas in the type specimen, its caruncle is projected anteriorly almost completely covering eyes ( Hartman 1956: 274), and in Linopherus branchiae are present along anterior and median chaetigers, whereas the holotype has branchiae continued to “near the posterior end of the body” ( Hartman 1956: 275). The holotype matches Cryptonome , by having a small caruncle, first chaetiger dorsally incomplete, and branchiae from chaetiger 3, continued almost to the end of the body (see key in Bleeker et al. 2023: 438); what was described as H. elongata can only match with Cryptonome , not with Linopherus or with any other genus having a small caruncle.

As indicated in the key above, C. elongata separates from other species by having caruncle elongate, tapered, whereas in the other species it is cushion-shaped.

On the other hand, Treadwell (1940: 1) proposed Metamphinome with M. multibranchiata which resembles Hipponoe by having an indistinct caruncle, branchiae from chaetiger 3 and continued throughout the body, and distinct large neurohooks. He did not compare his new genus with Hipponoe but the new genus was regarded as a junior synonym by Hartman (1951: 29), and by Pettibone (1963: 57).