Sphaeridium, FABRICIUS, 1775

Angus, Robert B, Sadílek, David, Shaarawi, Fatma, Dollimore, Hayley, Liu, Hsing-Che, Seidel, Matthias, Sýkora, Vít & Fikáček, Martin, 2021, Karyotypes of water scavenger beetles (Coleoptera: Hydrophilidae): new data and review of published records, Zoological Journal of the Linnean Society 192 (3), pp. 958-958 : 958-

GENUS SPHAERIDIUM FABRICIUS, 1775

( FIG. 14J–Q )

Material examined: Sphaeridium scarabaeoides (Linnaeus, 1758) : 2 spec. ( BMNH): United Kingdom, Surrey, Egham, R. Angus & F. Shaarawi lgt .

Sphaeridium lunatum Fabricius, 1792: 2 spec. (BMNH): United Kingdom, Surrey, Tilford, R. Angus & F. Shaarawi lgt.

Sphaeridium bipustulatum Fabricius, 1781: 1 spec. (BMNH): United Kingdom, Surrey, Tilford, R. Angus & F. Shaarawi lgt.

Comments: Angus et al. (2000) studied the mitotic and meiotic karyotypes of four European species, Sphaeridium bipustulatum , Sphaeridium lunatum , Sphaeridium marginatum and Sphaeridium scarabaeoides . The published figures of karyotypes were of low quality, and we hence provide those of three species again here and add the meiotic figures as well.

Karyotype: 2 n = 22 + Xy (♂). In the larger species, Sphaeridium lunatum ( Fig. 14J–K ) and Sphaeridium scarabaeoides ( Fig. 14L ), autosome pairs 4 and 5 are subacrocentric to acrocentric and pair 8 subacrocentric, with pair 11 also subacrocentric in Sphaeridium scarabaeoides . In the smaller species, Sphaeridium bipustulatum ( Fig. 14M ) and Sphaeridium marginatum , autosome pair 5 is metacentric and pairs 4 and 10 are subacrocentric. The X chromosome is medium sized metacentric and the Y is dot like in all species.

TRIBE MEGASTERNINI

Figures

Figure 1. Tissuesof hydrophiloid beetles used for chromosome preparations (as dissected, without any additionaltreatment, (B–E) in dorsal view; (A) Helophorus grandis; (B, C, I) Laccobius bipunctatus; (D–H) Coelostoma orbiculare). A, egg with a developing embryo. B–C, internal organs of the same male specimen in translucent light (B) and on black background (C). D, internal organs of a female with digestive system pulled aside. E, internal organs of male specimen. F, details of ovarioles and associated accessory glands. G–I, detail of midgut structure on black background (G) and in translucent light (H, I). Abbreviations: accg, accessory glands; aed, aedeagus; hg, hindgut; mg, midgut; Mt, Malpighian tubes; oo, ovarioles; ovi, ovipositor; rc, regeneration crypts; tes, testes. Not to scale.

Figure 2. Karyotypes of the Amphiopini and Laccobiini. A–E, Amphiops mater, mitotic methaphase from midgut. F–L, Laccobius decorus, mitotic metaphase from midgut.A, C, F, H, J, without treatment. B, D, G, I, K, C-banded. Habitus figures: (E) Amphiops mater; (L) Laccobius decorus.

Figure 3. Karyotypes of the Laccobiini, without treatment. A–H, Paracymus: (A–B) Paracymus aeneus, mitotic metaphase from midgut; (C–D) Paracymus scutellaris (C, spermatogonial mitosis, metaphase; D, mitotic metaphase from midgut.); (E–G) meiotic metaphase I from testes (E, Paracymus aeneus; F–G, Paracymus scutellaris). I–M, Tormus, mitotic metaphase from midgut: (I, K) Tormus posticalis; (J, L) Tormus helmsi. Habitus figures: (G) Paracymus scutellaris; (M) Tormus helmsi, from Fikáček et al. (2013).

Figure 4. Mitotic karyotypes of Hydrobius. A–C, Hydrobius fuscipes, testes. D, Hydrobius arcticus, midgut. E, Hydrobius rottenbergii, testes.F–H, Hydrobius subrotundus (F, midgut; G–H, testes). I, Hydrobius pui, testes.A, D–I, without treatment. B, C, C-banded. J, habitus of Hydrobius fuscipes.

Figure 14. Karyotypes of the Omicrini and Sphaeridiini, without treatment. A–F, Omicrini: (A–B) Noteropagus sp. from Taiwan, meiotic karyotypes from testes; (C–D) Omicrogiton insularis, mitotic karyotype, midgut; (E–F) Paromicrus sp. from Taiwan, mitotic karyotype, midgut. G–I, habitus of examined specimens: (G) Noteropagus sp.; (H) Omicrogiton insularis; (I) Paromicrus sp. J–P, Sphaeridiini: Sphaeridium; (J–K) Sphaeridium lunatum (J, testes, mitosis; K, midgut, mitosis); (L) Sphaeridium scarabaeoides, mitosis, midgut; (M) Sphaeridium bipustulatum, mitosis, midgut; (N–P) meiosis, metaphase I, testes: (N) Sphaeridium scarabaeoides; (O) Sphaeridium bipustulatum; (P) Sphaeridium lunatum. Q, habitus of Sphaeridium scarabaeoides.