Acromegalomma josei, Rebello & Nogueira & Carrerette, 2025

Rebello, João Gabriel, Nogueira, João Miguel De Matos & Carrerette, Orlemir, 2025, Description of four new species of Acromegalomma (Annelida, Sabellidae) from the Coast of Brazil (SW Atlantic), with comments on the morphological characters of the genus, Zootaxa 5620 (1), pp. 72-104 : 77-81

Acromegalomma josei sp. nov.

Figures 3–5 ; 17 (A–D); 18 (A–E); 19A; Table 2

Material examined. Holotype. ZUECPOL–2523 : complete, in soft-sediment (sand), 23.808ºS 45.365ºW, 1–3 m deep, March 1993, Praia do Perequê , Ilhabela, São Paulo, Brazil . Paratypes. ZUECPOL–2523 : 1 specimen, in soft-sediment (sand), 23.808º S 45.365ºW, 1–3 m deep, March, 1993, Praia do Perequê , Ilhabela, São Paulo, Brazil . ZUECPOL–3866 : 1 spec., in soft-sediment (sand), 23.796ºS 45.366ºW, 1–3 m deep, May, 1993, Ilhabela, São Paulo, Brazil ; ZUECPOL–4784 : 1 specimen, in soft-sediment (sand), 23.789º S 45.363ºW, 1–3m deep, September, 1995, Praia do Engenho d'Água , São Sebastião, São Paulo, Brazil .

Diagnosis. Spherical eyes on most radioles; collar dorsal margins fused to faecal groove, collar dorsal lappets and dorsal pockets both present; anterior peristomial ring exposed dorsally, between dorsal pockets; caruncle absent; collar ventral lappets rounded; first ventral shield entire; inferior thoracic notochaetae Type B sensu Capa & Murray (2009).

Measurements. Holotype body 15.5 (11.9–12.5) mm long. Radiolar crown 4.5 (2.5–3.2) mm long. Thorax 3.3 (2.3–2.7) mm long, 2.1 (1.3–1.8) mm wide.

Description. General aspects and color patterns. Elongated body whitish, thorax 1.5–3x longer than wide. Branchial crown longer than thorax, 1/3 of total body length, also whitish, lacking visible bands of pigmentation. One pair of large, prominent dorsal eyes on dorsalmost pair of radioles; tiny subdistal compound spherical eyes present on most radioles, except of three ventralmost pairs.

Radiolar crown. Crown longer than thorax, semicircular radiolar lobes, with 17 (16–20) pairs of radioles. Subdistal compound eyes on most radioles, absent on three ventralmost pairs ( Figs 3A ; 19A ); eyes large, spherical, gradually smaller dorsoventrally ( Figs 3C ; 17C–D ). Radioles of dorsalmost pairs with short tips, tips gradually longer ventralwards. Dorsal lips erect, triangular, about 1/5 of crown length, with radiolar appendages (mid-rib), and one pair of pinnular appendages present. Ventral lips about 1/3 of dorsal lips length, broadly rounded. Basal ventral flanges absent.

Peristomium. Anterior peristomial ring exposed between the dorsal pockets ( Fig. 3B ); caruncle absent. Collar dorsal margins fused to faecal groove, dorsal lappets rounded, U-shaped dorsal pockets ( Figs 3B ; 4C, E ; 17B ); collar ventral lappets shorter than first ventral shield, triangular, not overlapping, with mid-ventral incision reaching anterior margin of first ventral shield ( Figs 3A ; 4B, D ; 17A ), ventral sacs and ventral parallel lamellae both present; collar lateral margins straight, covering origin of radioles ( Figs 3A–C ; 4A–E ).

Thorax. Chaetiger 1: notochaetae all elongated, narrowly hooded ( Figs 5A ; 18A ); those of superior row longer; first ventral shield with rounded anterior margin and short medial incision ( Fig. 4B, D ). Chaetigers 2–8: thoracic tori all about same length, not reaching corresponding shields, extending for half extension between notopodia and corresponding ventral shield lateral margin ( Fig. 4B, D ). Notochaetae of superior group elongated, narrowly hooded, 4–6 per fascicle, inferior notochaetae broadly hooded, progressively tapering distally, Type B sensu Capa & Murray (2009), 15–16 chaetae per fascicle ( Figs 5B–C ; 18B ). Uncini with main fang surmounted by numerous rows of minute teeth, covering half of main fang, handles 1.5x length of main fang, 15–22 uncini per torus; companion chaetae with teardrop-shaped membranes, handles as long as those of uncini ( Figs 5D ; 18C ). Interramal eyespots absent throughout.

Abdomen. Segments: 72 (67–78). Neurochaetae broadly hooded, those of posterior rows longer,12–14 chaetae per fascicle ( Figs 5E ; 18D ). Uncini with main fang surmounted by rows of minute teeth, covering half of main fang length, and shorter handles than those of thoracic uncini ( Figs 5F ; 18E ), 14–16 uncini per torus.

Pygidium. Broadly rounded, pygidial eyespots absent.

Tubes. Unknown.

Methylene blue staining pattern. Thoracic ventral shields stain uniformly, first shield entire, with M-shaped anterior margin, subsequent ventral shields rectangular, divided into two parts by transverse fissures ( Figs 2 ; 4B ; 17A ).Abdominal shields each divided into two at midlength, by faecal groove, each half further divided transversely. Entire dorsum and lateral sides of the body pale, unstained ( Figs 2 ; 4B ; 17B ).

Etymology. The specific name of Acromegalomma josei honors José Guilherme da Silveira Vasconcelos Ferreira, first author’s husband, for his support and inspiration throughout this research.

Habitat. 1–3 m deep, in soft-sediments.

Distribution. Only known from the type locality, Praia do Perequê, Ilhabela, and surrounding areas, on the Northern coast of the State of São Paulo, Southeastern Brazil, Southern Atlantic Ocean.

Remarks. Individuals of this species were previously identified as A. bioculatum by Rizzo & Amaral (2000). Tovar-Hernández & Carrera-Parra (2011) provided a detailed redescription for that species, based on type material, and the comparison provided herein follows these latter authors. There are major differences between specimens of A. bioculatum ( Ehlers, 1887) and A. josei sp. nov., such as: members of A. josei sp. nov. have (1) eyes on most radioles (eyes on the dorsalmost pair of radioles only, in specimens of A. bioculatum ); (2) dorsalmost radioles have short tips, tips progressively longer ventralwards (all radioles with short tips, in members of A. bioculatum ) and (3) collar dorsal margins laterally fused to the fecal groove (not fused in individuals of A. bioculatum ).

Among the species of Acromegalomma described to date, members of A. josei sp. nov. share similarities with representatives of A. mushaense ( Gravier, 1906) , A. nechamae ( Knight-Jones, 1997) , and A. perkinsi , in having eyes on most radioles and collar margins laterally fused to the fecal groove, with dorsal pockets and dorsal lappets. However, members of all these species, have origin of radioles exposed laterally, while individuals of A. josei sp. nov. possess lateral margins of the collar covering the origin of radioles. Also, members of A. josei sp. nov. have short collar ventral lappets, while these are as long as first ventral shield in members of all these other species. Furthermore, members of the new species have ventral shields of subsequent segments with two transverse fissures, a feature not mentioned in the descriptions of any of those other species. Finally, inferior thoracic chaetae of members of A. josei sp. nov. are Type B sensu Capa & Murray (2009) (as in specimens of A. nechamae ), while individuals of A. perkinsi have inferior thoracic chaetae Type A. Other variable characters distinguishing members of all these species are shown in Table 2 .

Members of A. josei sp. nov. are distinguished from worms of the only other species originally described from the Southern Atlantic, A. schwindtae , by these latter having branchial crown as long as thorax and subdistal compound eyes only on dorsalmost radiolar pair, while specimens of A. josei sp. nov. have a branchial crown longer than thorax and subdistal compound eyes on most radioles. Additionally, individuals of A. josei sp. nov. have thoracic ventral shields with transverse fissures and Type B inferior thoracic notochaetae sensu Capa & Murray (2009), while members of A. schwindtae have entire ventral shields and Type A inferior thoracic notochaetae sensu Capa & Murray (2009).

Figures

FIGURE 2. Methyl blue staining patterns of specimens of each of the new species of Acromegalomma described herein, in ventral view. Numbers refer to chaetigers.Abbreviations: t: thorax; a: abdomen.

FIGURE 3. Acromegalomma josei sp. nov., holotype. A. Entire worm, lateral view; B. Thorax, dorsal view; C. Anterior end, dorsolateral view. Scale bars: A: 3 mm; B: 1 mm; C: 2 mm. Abbreviations: de: dorsalmost radiolar eyes; dp: dorsal pockets; se: subdistal eyes.

FIGURE 4. Acromegalomma josei sp. nov., paratypes, before and after methylene blue staining.A. Entire worm, ventral view; B.Anterior end, ventral view; C.Anterior end, dorsal view; D.Anterior end, ventral view; E. Anterior thoracic chaetigers, dorsal view. Scale bars: A: 3 mm; B–D: 2 mm; E: 1 mm.Abbreviations: dp: dorsal pockets; dl: dorsal lips, Paratype ZUECPOL-3866: photos B, C; Paratype ZUECPOL-4784: photos A, D, E.

FIGURE 5. Acromegalomma josei sp. nov., chaetae under compound microscopy. A. Collar chaetae; B. Superior thoracic notochaetae; C. Inferior thoracic notochaetae (Type B sensu Capa & Murray 2009); D. Thoracic neurochaetae; E. Anterior abdominal neurochaetae; F. Anterior abdominal uncini (notochaetae). Scale bars: A–F: 5 μm.

FIGURE 17. Acromegalomma new species. Body schemes. A–D: A. josei sp. nov., A. Anterior thoracic chaetigers, ventral view; B. Anterior thoracic chaetigers, dorsal view; C. Dorsalmost radiolar eye; D. Eye of lateral radiole. E–H: A. omenae sp. nov., E. Anterior thoracic chaetigers, ventral view; F. Anterior thoracic chaetigers, dorsal view; G. Dorsalmost radiolar eye; H. Eye of lateral radiole. I–L: A. punctum sp. nov., I. Anterior thoracic chaetigers, ventral view; J. Anterior thoracic chaetigers, dorsal view; K. Dorsalmost radiolar eye; L. Tips of lateral and ventralmost radioles, lateral view. M–Q: A. scutolenis sp. nov., M. Anterior thoracic chaetigers, ventral view; N. Anterior thoracic chaetigers, dorsal view; O. Dorsalmost radiolar eye; P. Eye of lateral radiole; Q. Ventralmost radiolar eye. Arrows om F, J, N point to caruncle. Scale bars. A–B, E–F, M–N: 1 mm; C–D, G–L, O–Q: 0.5 mm.

FIGURE 18. Acromegalomma new species. Chaetae. A–E: A. josei sp. nov. A. Collar chaeta; B. Thoracic notochaetae; C. Thoracic neurochaetae.D.Anterior abdominal neurochaeta; E.Anterior abdominal uncinus (notochaeta). F–J: A. omenae sp. nov. F. Collar chaeta; G. Thoracic notochaetae; H. Thoracic neurochaetae. I. Anterior abdominal neurochaeta; J. Anterior abdominal uncinus (notochaeta).K–O: A.punctum sp. nov. K.Collar chaeta; L.Thoracic notochaetae;M.Thoracic neurochaetae.N.Anterior abdominal neurochaeta; O. Anterior abdominal uncinus (notochaeta). P–T: A. scutolenis sp. nov. P. Collar chaeta; Q. Thoracic notochaetae; R. Thoracic neurochaetae. S. Anterior abdominal neurochaeta; T. Anterior abdominal uncinus (notochaeta). Scale bars. A–B, G–H, J–K, N, P–Q: 10 μm; C–F, I, L–M, R–S: 5 μm; O, T, J: 2 μm.

FIGURE 19. Acromegalomma new species. Subdistal compound eyes arrangement. A. Acromegalomma josei sp. nov.; B. Acromegalomma omenae sp. nov.; C. Acromegalomma punctum sp. nov.; D. Acromegalomma scutolenis sp. nov. Small dots: radioles with subdistal compound eyes; large black dots: dorsalmost radiolar eyes.