Amynthas carnosus naribunji Blakemore, 2013

Han, Anne Charis N., Zhang, Yufeng, Miao, Pu, Wu, Shaolong, Xiao, Nengwen, Qin, Mingyan, Zhao, Huifeng, Wu, Donghui & Aspe, Nonillon M., 2024, Distribution and systematics of the cosmopolitan Amynthas carnosus complex (Crassiclitellata, Megascolecidae) from eastern Asia, Zoosystematics and Evolution 100 (3), pp. 1061-1073 : 1061-1073

Amynthas carnosus naribunji Blakemore, 2013

Amynthas pingi : Blakemore 2013 a: 60, figs 4, 5.

Material examined.

Specimen IDs: 551 R 3 (01–10), 10 adults from Longwan Park, Huludao Pref., Liaoning Prov. One specimen from Beijing is a juvenile and was poorly preserved. Thus, its morphological examination was not performed. However, the molecular data is presented (DNA ID: BJCY _ 42, Fig. 1 ).

Diagnosis.

Spermathecal pores four pairs in 5 / 6 / 7 / 8 / 9, located latero-ventrally (0.29–0.30 mm), each with pre-intersegmental hemispherical arc (spermathecal papillae) anterior to intersegments (Fig. 6 ). Pre-clitellar genital markings absent (complying with Kobayashi Type I in Blakemore 2013 a); if present, one to three pairs; pre-setal in VIII and IX when one or two pairs and having a post-setal pair in VIII when three pairs (complying with Kobayashi’s Types III, IV, and VIII); asymmetrical patterns also present (Fig. 7 ). Male pores superficial in XVIII having “ disc-like ” genital markings paired posterio-median to male pores (Fig. 8 ).

Description.

Length 185–228 mm. Color of preserved specimens may have varying shades of brown but dorsum generally dark brown in pre-clitellar region to brown in post-clitellar region, fading to lighter brown towards posterior end with darker clitellum, while ventrum part is paler / fleshy color. Clitellum width 5.8–8.3 mm. Segments 115–137. Prostomium epilobous. First dorsal pore on 12 / 13. Clitellum annular at XIV – XVI without setae or dorsal pores. Setal arrangement perichaetine, setae between male pore 18–19. Female pore single and circular, midventral at XIV.

Spermathecal pores large, having four pairs in 5 / 6 / 7 / 8 / 9 and widely-spaced, latero-ventral (0.29–0.30 mm) in pre-intersegmental hemispherical arc (spermathecal papillae). Pre-clitellar genital markings circular in shape, latero-ventral (0.25–0.29 mm), randomly located in pairs (three pairs / two pairs / one pair, a total of 2–6 genital markings), or asymmetrically located on one side (1–2 genital markings), about 0.38–0.59 mm in diameter.

Male pores superficially paired in XVIII close to lateral margin (with ventral distance 0.26–0.29 mm) on large circular porophores. Post-clitellar genital markings distinguishably paired, post-setally in XVIII, mid-ventral to male pore, 0.42–0.69 mm in diameter.

Septa 4 / 5–7 / 8 and 10 / 11–14 / 15 thickened, 8 / 9 / 10 absent. Esophageal gizzard within VIII-X. Intestinal origin at XV (or XIV). Intestinal caeca simple, paired in XXVII, extending anteriorly to XXII. Last hearts in XIII.

Four pairs of spermathecae in VI-IX. Ampulla ovate, wrinkled; ducts short and stout. Diverticula reaching one-third to half of ampulla with a slender stalk and a wider seminal chamber; seminal chamber elongated or botuliform. Accessory glands sessile and round.

Seminal vesicles paired in XI and XII, large, smooth, yellowish, posterior pair larger but not as obvious compared to A. c. carnosus , each with a dorsal lobe. Ovaries present. Prostate glands paired in XVIII, large, lobulated, covering XVI-XX; ducts thick and large, U-shaped. Accessory glands round, sessile, or slightly lobed, corresponding to each genital marking around male pore area.

Distribution.

Northern China (Liaoning, Beijing) and South Korea (Ulleung Island).

Remarks.

There is not much of a thorough morphological description of A. carnosus naribunji in the original account of Blakemore (2013 a) (see Suppl. material 1: table S 3) aside from its single illustration of paired post-clitellar genital markings in the male pore area and a spermathecal pore with corresponding spermathecae shown in fig. 4 by Blakemore (2013 c).

Notable features of A. c. naribunji in comparison with A. c. carnosus were its slightly larger size with lengths of 185–228 mm, typically wide-spaced pre-clitellar genital markings with a maximum number of six (three pairs) to at least three genital markings; pre-setal / post-setal in VIII and pre-setal in IX. In contrast, A. c. carnosus is typically medium to smaller size, with mostly only four genital markings (two pairs) or less, either wide or closely-spaced pre-clitellar (Table 3 ).

The distinctive character of having “ a pair of genital markings posterio-median to male pores ” in A. c. naribunji may distinguish it from those of A. c. carnosus (Blakemore, 2013 a) . However, it is now undeniable that this seemingly “ distinctive character ” was likewise observed in the A. c. carnosus specimens from Liaoning and Henan (Fig. 8 ). Here, we dismiss the former notion of Blakemore (2013 a) “ to consider for exclusion Kobayashi’s Types I and II markings ” as a distinctive character for the A. c. carnosus subspecies, A. c. naribunji. Although this might be the case, one cannot ignore the certain degree of dissimilarity between the two subspecies’ morphological characters (e. g., the shape of male pore porophore and the distinct shape of the genital markings in A. c. naribunji, described as “ disc-like ” by Blakemore). As such, applications of state-of-the-art methodologies such as high-throughput sequencing or geometric morphometric ( Marchán et al. 2020) may be adopted that go beyond traditional methods of taxonomic diagnosis (which in this case is rather insufficient to “ quantify ” the degree of variations). Nevertheless, the incorporation of genetic data such as DNA barcoding and calculating K 2 P intraspecific distances (as conducted in this study) may aid in suggesting subspecies delineation.

Figures

Figure 1. The geographical distribution of the A. carnosus complex in eastern Asia and its corresponding phylogenetic tree based on COI using the maximum likelihood method. Color coding: red for China, purple for South Korea, and green for Japan.

Figure 6. A. carnosus naribunji (specimen ID 551 R 3 _ 01): Prostomium (A); Male pore with posterio-median paired genital marking (B); Seminal vesicles (C); Intestinal caeca (D); spermathecae (E); Prostate gland with U-shaped think duct (F); and Spermathecal pores with three pairs of pre-clitellar genital markings (G). Scale bars: 1 mm.

Figure 7. A. carnosus naribunji pre-clitellar genital marking variations; A – C. Complying with Kobayashi’s (1936) Types III, IV, and VIII, respectively; D – F. Displays asymmetrical patterns. Scale bars: 1 mm.

Figure 8. Image comparison of male pore porophores and paired posterio-median genital markings between A. carnosus carnosus. A, B. (specimen IDs 362 R 1 _ 07 and HNLNR 2 _ 04) and A. carnosus naribunji from Liaoning; C-E. (specimen IDs 551 R 3 _ 01, 551 R 3 _ 09, and 551 R 3 _ 06) and Ulleungdo, F. (specimen ID w 54).